Ministry of Education and Science of Russian Federation
Federal Agency for Education
State Educational Institution of Higher Professional Education
UFA STATE PETROLEUM TECHNOLOGICAL UNIVERSITY
A.M. Syrkin, E.M. Movsumzade, O.I. Mikhailenko, M.N. Nazarov
FUNDAMENTALS OF CHEMISTRY OF OIL AND GAS
А.М. Сыркин, Э.М. Мовсумзаде, О.И. Михайленко, М.Н. Назаров
ОСНОВЫ ХИМИИ НЕФТИ И ГАЗА
Допущено Министерством Образования Республики Башкортостан
в качестве учебного пособия
Уфа 2005
4
UDC 665.62(07)
BBK 35.514я7
S 95
Reviewers:
Head of department of organic chemistry of Russia Academy of Sciences
Ural Centre, professor I.B. Abdrakhmanov
Head of GUP “Neftekhimpererabotka”, professor E.G. Teliachev
Head of department of mining and operation of oil and gas fields, USPTU,
Professor Zeigman Y.V.
Syrkin A.M., Movsumzade E.M., Mikhailenko O.I., Nazarov M.N.
S 95 Fundamentals of chemistry of oil and gas: The manual. – Ufa: Ufa state
Petroleum technical university, 2005. – 106 p.
ISBN
In the manual hypothesizes of origin of oil, physicochemical properties of oil, classifications of them, properties and
reactions of the main classes of the compounds contained in oil and gas are observed. Methods of petroleum and gas
refining for production of various petroleum derivatives – engine fuels, lubricating oils and products of petrochemistry, ways of industrial use of oil ingredients are observed.
Meant for students of the trade “Oil-and-gas business”.
UDC 665.62(07)
BBK 35.514я7
ISBN
© Ufa state petroleum technical university,
2005
© Syrkin A.M., Movsumzade E.M., Mikhailenko O.I., Nazarov M.N., 2005
5
UFA STATE PETROLEUM TECHNICAL UNIVERSITY
A.M. Syrkin, E.M. Movsumzade, O.L. Mikhailenko, M.N. Nazarov
FUNDAMENTALS OF CHEMISTRY OF OIL AND GAS
The manual
Ufa 2005
6
UDC 665.6(075.8)
S
It is authorized by publishing council Ufa state petroleum technical
University in the capacity of the manual
Reviewers
Head of department of organic chemistry of Russia Academy of Sciences’
Ural Centre, professor I.B. Abdrakhmanov
Head of GUP “Neftekhimpererabotka”, professor E.G. Teliachev
Head of department of mining and operation of oil and gas fields, USPTU,
professor Zeigman Y.V.
Syrkin A.M., Movsumzade E.M., Mikhailenko O.I., Nazarov M.N.
Fundamentals of chemistry of oil and gas: the manual. – Ufa: Ufa state
Petroleum technical university, 2004. – 106 p.
In the manual hypothesizes of origin of oil, physicochemical properties of oil, classifications of them, properties and reactions of the main
classes of the compounds contained in oil and gas are observed. Methods of
petroleum and gas refining for production of various petroleum derivatives –
engine fuels, lubricating oils and products of petrochemistry, ways of industrial use of oil ingredients are observed.
Meant for students of the trade “Oil-and-gas business”.
UDC 665.6(075.8)
© Ufa state petroleum technical university, 2004
© Syrkin A.M., Movsumzade E.M., Mikhailenko O.I., Nazarov M.N., 2005
93
THE FOREWORD
One of the major problems in chemistry of oil and gas is the study of compositions of oils and natural gases with the help of physical and physicochemical methods
of research. Chemistry of oil also deals with physicochemical properties of hydrocarbons and nonhydrocarbon components of oils in connection with their structure.
Composition of oils and gases depends on geological and geochemical conditions of formation and occurrence of oil. Therefore, the study of chemical composition and components of oils has a great significance for understanding of geochemical processes of transformation of oils in the earth's crust. On the other hand the composition of oils defines possible ways of their extraction and transport as well as their
conversion into various products.
The study of oils usually includes: an elementary chemical composition, group
composition, i.e. content of various classes and groups of compounds, individual
chemical composition of separate compounds and isotopic composition of oils.
Chapter 1
GENERAL CHARACTERISTIC OF OIL AND GAS
—————————————————————————————————
Oil is a mutual conjugate solution of hydrocarbons and heteroatomic organic
compounds. It is necessary to emphasize, that oil is not a mixture of substances, but a
solution of hydrocarbons and heteroatomic organic compounds. It means that the
study of oil intends to qualify it as a solution.
Oil – is not only a solute in solvent but the mutual solution of proximate homologues and other compounds. It is named conjugative solution because proximate
compounds are dissolved in each other and form thereby the common system that
represents oil as a whole.
The destruction of conjugative mutual system of proximate ingredients leads to
the partial destruction of the oil as a system.
Oil itself is a liquid mineral that is contained in porous sedimentary rocks of an
earth's crust, in cracks and other hollows of parent rock formations (granite, gneisses,
basalts, etc.).
Oil is a deep-brown sometimes almost colourless and sometimes black coloured liquid.
Oil is a combustible mineral as well as mineral coal, brown coal and shales.
Unlike other combustible minerals, oil consists of a ready mixture of various hydrocarbons, whereas special heat treatment is needed for obtaining of hydrocarbons from
solid combustible minerals. Therefore, oil is the most valuable raw material for production of diverse engine fuels, grease oils and products of petrochemical synthesis.
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1.1. OIL AND GAS PRODUCTION
The most known commercial oil deposits form significant accumulations in sedimentary rocks (sands and carbonates); these rocks have a sufficient porosity and
other conditions that are needed for accumulation of large amounts of oil.
Usually the dense bed of clay serves as a supporting medium for petroliferous
horizon. The oil deposit may include several horizons located one above another in a
vertical direction. These horizons are separated by dense beds of sedimentary rocks
and oil from various horizons of the same deposit may be different on properties.
It is considered, that oil is capable to some underground moving, named as migration.
The oil deposits usually contain accompanying petroleum waters and gases;
their densities are considerably different, that is why these substances are bedded in
order: aqueous lay, liquid oil and gases - above the oil.
Fig. 1 demonstrates the principal diagram of a routine oil deposit. A prospect
of oil bases on the knowledge of geological structures as well as on the analysis of
indications of oil in the earth's crust, on the application of geophysical and geochemical methods and on prospecting.
6
6
5
1
2
4
3
4
Fig. 1. The model lay-out diagram of holes on the oil deposit:
1 - a fold of an impermeable rock; 2 - an accumulation of gas; 3 - an accumulation of oil;
4 - stratal water; 5 – a vertical hole; 6 - slanting boreholes
Depending on a deposit oil occurs on a depth within 500 - 5000 m, at temperatures 35-260 °С and pressure up to 500 atm.
Values of temperature and pressure are also high in gas fields.
Pressure in layers depends on the depth of a bed and on the temperature.
To extract the oil and investigate oil deposits holes are drilled both in a vertical
and i. a slope direction.
95
Tree ways are suitable for operation of oil well: flowing, compressor and bottomhole pumping.
Due to the high pressure of stratal waters, gas and rocks the extraction of oil at
the first stage is conducted with a flowing method through a stop valve and pipes. Oil
enters in traps and storage capacities from bowels under its own pressure.
When pressure is decreased oil is mined with a compressor method. A column
of force pipes with a column of pipes of smaller diameter (lifting pipes) inside is put
into the hole. Compressed gas – air or natural gas is fed to force pipes; the pressure is
increased and oil is pushed to the bottom end of lifting pipes. Such artificial gas-andoil mixture has smaller density than a crude oil and consequently it is lifted through
the internal column of pipes to wellhead on the surface. During the operation of deep
well and great fall in pressure decrease bottomhole pumping is applied and oil is
gradually forced out on the surface.
With the help of these methods it is possible to take no more than 40 % of oil.
Other oil is taken with other methods. Thus gases (methane, ethane, etc.) are pumped
in the hole under high pressure and oil leaves upward. Sometimes edge waterflooding
is applied: water that was injected into the hole expels oil. During the operation of
tough oils steam up to 200 °С or dissolvents are injected into the hole. It is rather effective to pump acids, surfactants and some other reagents into a layer.
The problem of maximal extraction of oil from a layer is one of the major
problem of the operation of petroleum and gas fields.
Due to the great pressure oil in a layer dissolves associated gases; they evolve
during the rising of oil on the surface. The composition of associated gases depends
on the pressure.
The pressure in petroleum bed is decreased during the operation; according to
the gaseous tension the composition of gases is also changed: at the beginning gas is
enriched with methane, then with ethane, then with propane, etc.
At the moment of the lowest pressure the most "aliphatic" gases containing
large amounts of liquid (under standard temperature and pressure) hydrocarbons (socalled casing-head gasoline) are evolved.
1.2. THE ORIGIN OF OIL AND GAS
The question on the origin of oil and gas has the great theoretical and practical
significance. The solution of this problem makes easier to search for petroleum and
gas fields, to evaluate their stocks and to organize their operation and processing.
Now it is a common knowledge about geological conditions of oil and gas
formation. But the question on the origin is not finally solved.
Numerous theories about the origin of oil and gas are divided into two basic
classes – an organic (biogenic) and inorganic (abiogenic) origin.
One of inorganic theories of the origin of oil was offered in 1877 by
D.I.Mendeleev. He has put forward so-called “carbide” hypothesis. According to his
opinion, water penetrated into the depth of land inside of cracks in sedimentary and
96
crystal rocks up to magma and reacted with carbides of heavy metals with formation
of hydrocarbons:
СаС2 + 2 Н2О → Са(ОН)2 + С2Н2
Al4C3 + 12 H2O → 4 Al(OH)3 + 3 CH4
Hydrocarbons and water were evaporated under the influence of high temperatures, lifted to outside parts of land and condenced in permeable sedimentary rocks.
Experiments carried out by chemists have confirmed such way of hydrocarbons formation.
In 1982 the Russian scientist Sokolov V.D. offered so-called "space" hypothesis; according to this assumption petroleum hydrocarbons are formed from carbon
and hydrogen during the formation of Earth and other planets. When the Earth became cool hydrocarbons were captured and condenced in an earth's crust. The corroboration of this hypothesis is connected with the detection of fair quantities of methane in the atmosphere of planets.
Deep-seated massive crystal rocks, as well as meteorites, contain elementary
carbon and carbides of heavy metals. The same rocks contain water, hydrogen, carbon dioxide and carbonic acid. A lot of other hypotheses about the inorganic origin of
oil and gas in bowels of Earth are presently put forward as a result of chemical reactions immediately from carbon and hydrogen under high temperatures, pressures and
catalytic action of metals oxides (Fe, Ni, etc.) (N.A. Kudryavtsev, V.B. Porfiljev,
etc.).
The first hydrocarbon synthesis from CO and Н2 was carried out by Russian
chemist E.I. Orlov in Kharkov (1908); he obtained the elementary olefinic hydrocarbon – ethylene according to the schema:
2 СО + 4 Н2 → С2Н4 + 2 Н2О
This reaction has been carried out at 100 °С and under the contact with the catalyst consisting of Ni + Pd, precipitated on coke.
Later it has been established, that not only ethylene, but also some other more
complex alkenes are formed.
Heavy metals of the iron subgroup especially in the presence of aluminum and
magnesium oxides under the pressure and without it promote the formation of hydrocarbons of various classes that have complex composition:
2 CO + H2
CO + 2 H2
Fe
Ni
Co
CH2 + CO2
CH2 + H2O
According to conditions these reactions lead not only to liquid hydrocarbons
and water, but also to paraffins, ceresins, gases – methane and its proximate homologues - and carbonic acid.
97
However, it is necessary to say, that inorganic hypotheses of the origin of oil
contradict both geological data and present knowledge of the composition of oils.
The majority of geologists and chemists support the organic origin of oil and
gas. Supporters of this hypothesis (М.V. Lomonosov, V.I.Vernadsky, I.M.Gubkin,
A.F.Dobrjansky, etc.) consider, that sources of oil were plants and animals that have
accumulated during million of years at the bottom of ponds in past geologic epochs
as a silt. Than mortified organisms were overlapped by beds of sedimentary rocks
and under the effect of anaerobic bacteria underwent biochemical metamorphosis.
There were complex processes of hydrolysis and reduction of substances that are contained in organisms: lipids, carbohydrates, proteins and lignin. A part of organic
compounds in upper layers of sedimentary depositions was converted into gases
(CO2, N2, NН3, CН4, etc.) – this is a stage of diagenesis. In lower sedimentary layers
on the depth of 1-3 km under high-pressure (10-30 МPа) and temperature (120-150
°С) and at catalytic effect of rocks the decisive phase of genesis of oil began: formation of hydrocarbons from organic materials and their transformations – this is a stage
of catagenesis.
Products of transformation – oil and gas - are originally scattered in petroparent, more often in argillaceous rock. Oil and gas are capable to move (to migrate) in
strata of rocks due to the pressure effect of rock, diffusion, a filtering in pores and
fractures under the act of capillary forces. As a result of migration oil and gas were
collected into so-called traps, i.e. in low-permeability rocks. Such accumulations of
oil are called oil pools. If the amount of oil and gas in a deposit is great or there are
some deposits in the given frame of layers of rocks - it is petroleum, oil-and-gas or a
gas field.
A lot of geological and geochemical observations and facts confirm the organic
hypothesis of oil origin. The most convincing is a well proved connection between oil
composition, natural material and organic matter of ancient sedimentary rocks and
present sediments.
1.3. MAIN PHYSICOCHEMICAL PROPERTIES OF OILS
Physicochemical properties of oils and their fractions depend on chemical
composition and structure of individual ingredients and also - on their complex inner
structure cased by intermolecular forces.
Oil and its fractions consist of the greate number of diverse substances that
have different chemical nature and various quantitative and qualitative compositions;
so, properties of petroleum derivatives have averaged characteristics that are quite
differ both for different oils and fractions and for same fractions of different oils.
1.3.1. Physical properties of oils and petroleum derivatives
The most important indexes of oils are relative density, viscosity, molecular
mass, boiling and congelation points, combustion heat and optical properties that give
us a first notion about composition of oils.
98
Density of oil characterizes composition and quality of oil and ease of its settling of water.
Density – is a magnitude that can be determined as a ratio of the mass of substance to the volume of this substance.
The relative density is usually used for oil and its derivatives; it can be determined as a ratio of a density of oil at 20 °С to the density of water at 4 °С (d420).
Relative density of gas demonstrates in how much time a density of it is higher
than one of a dry air.
Mainly relative density of oils is changed in limits of 0.750-1.0 g / cm3. But
there are oils with a density below 0.750 and heavy-bodied asphalt-base oils, which
have a density exceeds 1.0. Difference in the density of oils is connected with difference in a quantitative relation of hydrocarbons of various classes: oils with predominance of alkanes are easier than ones consist of aromatic hydrocarbons. Oils that
contain significant amount of pitchy compounds have a density higher than 1.0. Density is determined with aerometer and hydrostatic balance.
Viscosity of oil is a property that demonstrates a resistance to movement of
corpuscles relatively one another. There are different types of viscosity: dynamic, kinematical and relative. Unit of dynamic viscosity in the international system of units
(SI) is Pascal per second (Pа∙s). It means the resistance that two layers of liquid each
with a square of 1 m2 and in a distance of 1 m from each other put up under mixing
with a speed of 1 m/s under the act of force of 1 N.
A value that is reversed to dynamic viscosity is called as a flow.
Kinematic viscosity is a ratio of dynamic viscosity of a liquid to its density at
the temperature of determination. In SI system unit of kinematic viscosity is m2 / s.
Widespread units of kinematic viscosity in S.G.S. system are Stoke (St) and a centistoke (сSt); 1 St = 1·10-4 m2 / s.
A value of so-called relative viscosity is often used in practice.
Kinematic viscosity of oils from various deposits is changed within a range of
2 - 300 mm2 / s (сSт) at 20°С and usually is not higher than 40-60 mm2 / s. Viscosity
of oils depends on the nature of hydrocarbons, temperature and pressure.
Naphthenic hydrocarbons have the greatest viscosity. The rise of temperature
leads to sharp decreasing of viscosity and the growth of pressure – to its increasing.
Viscosity has a great significance since it defines scales of migration during the
formation of oil deposits and plays the important role in process of oil production
(sticky oil is more difficult to extract from entrails), defines power consumption for
pumping-over of oil in pipelines. Viscosity is determined with viscosimeters.
Average molecular mass of the majority of oils is equal 250-300.
Oils are characterized by temperature of the beginning and final boiling point
within the average range of 450-500 °С.
The set point of oil that is depended on its composition has also the great significance. There are oils of above-zero temperature of congelation with significant content of solid paraffins. Oils without paraffins in most cases have negative set points.
99
Oils are used for production of various fuels that is why they are characterized
by combustion heat in the range of 10400-11000 kcal / kg (43250-45500 Dj / kg).
Combustion heat is determined with combustion of fuel in calorimetric bombs.
One of qualitative characteristics of oil is a colour which can change from
black, deep-brown up to reddish, yellow and bright-yellow depending on the content
of gum-asphaltene materials.
Oils have a visible fluorescence – iridescent colour of a surface in a reflected
light due to the presence of condensed polynuclear aromatic compounds.
Oil shines or luminescents under ultraviolet radiation that is caused by the
presence of resins, asphaltenes and porphyrins. This property is used in analysis of
oil. The luminescence and fluorescence have a grate practical significance (search
and prospecting), because they help to detect traces of oil in cores and rocks of depositions.
One of the important optical characteristics of oil and petroleum derivatives is
the index of refraction (refractive index). During the refraction of light on the interface of two medium the ratio of a sine of the angle of fall to a sine of the refractive
angle remains constant. This ratio calls the index of refraction of the second medium
in relation to the first.
Index of refraction (n) depends on the wave length of the fallen light and temperature. It can be determined with the help of refractometers at the temperature of 20
°С for monochromatic light (yellow line D of sodium). Index of refraction characterizes the purity of individual compound only and its application to such complex mixture as oil is limited, but it may use for analysis of its ingredients and fractions.
Physical properties of bed oils are rather differ from ones of surface degassed
oils; that are caused by effect of temperature, pressure and solved gases. Change in
physical properties of bed oils is connected with conditions of their presence in a
layer and this fact must be taken into account during the estimation of oil and gas resources as well as designing, development and maintenance of oil deposits.
1.3.2. Elementary and isotopic composition of oils and natural gases
In spite of the fact that oil occurs in different geological conditions its elementary composition is changed in small limits. Five chemical elements: сarbon, hydrogen, sulphur, oxygen and nitrogen – are always present in oils with a significant
quantitative predominance of the two first elements. Carbon content of oils oscillates
within 83-87 % and in natural gases – 42-78 %. Hydrogen presents in oils within 1114 % and in gases – 14-24 %. The most common of other elements that are present in
oil is sulphur: its content in some oils attains 6-8 %. In natural gases sulphur usually
presents as hydrogen sulphide in amount of 23 % (the Astrakhan deposit) and even
more than 40 % (Texas).
The oxygen content of oils sometimes attains 1-2 %. In natural gases oxygen
usually presents as СО2; its amount varies from zero concentration up to almost clear
100
carbon dioxides (80 % СО2 – deposit in Western Siberia, 99 % СО2 – New Mexico
City).
The nitrogen content of oils does not exceed 1 % and in natural gases attains
10%. Some natural gases almost completely consist of nitrogen (85-95 % N2, a deposit West-Brook in Texas).
Helium, argon and other noble gases present in natural gases too. The helium
content in gases is usually less than 1-2 % but in some cases it attains 10 %. The argon content in gases as a rule does not exceed 1 % and rather seldom attains 2 %.
Metals: aluminum, iron, calcium, magnesium, vanadium, nickel, chrome, cobalt, germanium, titanium, sodium, potassium, etc - also present in oils in trace
amounts. Phosphorus and silicon are detected too. The content of these elements does
not exceed several shares of percent and depends on geological conditions of the occurrence of oil. So, iron is basic in Mesozoic and tertiary oils. The content of vanadium and nickel is higher in Paleozoic oils of the Volga-Ural range. It is considered
that the part of microelements is present in oil from the moment of its formation in
sedimentary rocks and other part collects in a consequent period of existence of oils.
Elementary composition of some oils is given in tab. 1 (appendix).
Isotopic composition (i.e. a relation of isotopes of carbon, hydrogen, sulphur
and nitrogen) represents the greate interest to find out a geochemical history of oils. It
is known that ratios of masses of various isotopes in oils are: 12С/13С – 91-94, Н/D
(1Н/2Н) – 3895-4436, 32S/34S – 22-22.5, 14N/15N – 273-277.
Various components of the same oil have different isotopic composition of
elements. Low-boiling fractions are reached by сarbon-12. On the other hand aromatic hydrocarbons are more enriched with an isotope 13С than that of paraffin hydrocarbons.
1.3.3. Group chemical composition of oils
Elementary composition of oil leads to the conclusion that oil mainly consists
of hydrocarbons. There are three main classes of oil hydrocarbons: alkanes, cycloalkanes and arenes.
Mixed hydrocarbons attend too. Alkenes and alkynes are present in small
amounts because of the rigid conditions of the existence of oil in nature (temperature
up to 200 °С and more).
Relatively young (tertiary) depositions mainly contain cyclic and polycyclic
hydrocarbons and oils of Paleozoic depositions consist of aliphatic hydrocarbons.
There are also nonhydrocarbon compounds in oil. They contain oxygen, sulphur and nitrogen; some resins and asphaltenes containing oxygen, sulphur and nitrogen with a not quite clear chemical nature are known too. There are also some other
heteroorganic compounds, but at present time their nature is not quite investigated.
Oil also contains some mineral substances.
101
1.3.4. Fractional composition of oil
The distribution of oil hydrocarbons on boiling points has the grate significance for the estimation of oil quality and choice methods of its further processing.
Fractional distillation is the first step of laboratory research of chemical composition
of oils: fractions that boil within two, three, and sometimes one degrees are taken for
the determination of separate groups or individual hydrocarbons.
Laboratory technical monitoring includes the selection of 10-th and then 50-th
degree factions from the beginning of boiling up to 300 °С.
On industrial distillation fractions that boil in more broad temperature range
are taken. Such fractions are called distillates. The first step includes the distillation
at atmospheric pressure; the following distillates are taken:
– petrol (the beginning of boil 170200 °С);
– naphtha (160200 °С);
– kerosene (180270-300 °С);
– gas-oil (270350 °С).
Intermediate fractions:
– kerosene - gas-oil (270300 °С);
- gas-oil - solar (300350 °С);
- distillation residue - mazut.
So-called light oils products are compounded from the fractions that boil up to
350 °С: aviation and motor spirits; benzines and ligroins – dissolvents; kerosenes –
jet engine fuel and tractor fuel; burning kerosene; gas-oils – diesel fuel.
Distillation residue (more than 350 °С) – mazut is distilled in vacuum to prevent a decomposition of the ingredients and the following oil distillates are obtained:
solar, transformer, spindle, autol, cylinder and distillation residue – tar oil (or topped
residue). Oil distillates are used for preparation of lubricating oils and viscous lubricants.
The most viscous lubricating oils and bitumen are obtained from tar oil (topped
residue).
Oils differ in their fractional composition depending on the oil field.
1.4. CLASSIFICATION OF OILS
Oils of different deposits and even of one deposit, but of different horizons, are
differed in elementary and hydrocarbon composition that defines also difference in
their physical and chemical properties. Properties of oils determine methods of their
extraction and exploitation of deposits and of their processing and quality of products. Absolutely equal oils do not exist but there are oils closed by the chemical na-
102
ture and properties. It was the basis for chemical and technological classification of
oils.
1.4.1. Chemical classification
This classification is connected with the dominant content of hydrocarbons that
belong to one or several classes. The class of oil that is based on group chemical
composition is determined only for the fraction that boils up to 300 °С. Oils are divided into three basic types depending on the predominance of hydrocarbons of one
class (50 % and higher) in this fraction: 1) methanoic (М); 2) naphthenic (N); 3) aromatic (А).
The presence of more than 25 % of hydrocarbons of other classes in control
sample makes such oil a member of the mixed type: 1) methanoic - naphthenic (МN);
2) naphthenic - methanoic (NM); 3) aromatic - naphthenic (АN); 4) naphthenic aromatic (NA); 5) methanoic - aromatic (МА); 6) aromatic - methanoic (АМ). There
are oils with approximately equal amounts of all three basic classes of hydrocarbons
(methanoic - naphthenic - aromatic oils). Oils of the first three types are rare. Aromatic and naphthenic oils are more often occurred. The majority of oils belong to the
mixed types. Oils of types МА and АМ are not detected in the nature.
1.4.2. Technological classification
According to the technological classification that is accepted in our country,
oils are subdivided into classes – under the sulphur content, types – depending on the
potential content of fuels (the fractions which boil up to 350 °С), groups – under the
potential content of base oils, subgroups – under the quality of oils, determined by
viscosity index, kinds – under the paraffin content.
Oils are subdivided into three classes - under the amount of sulphur: I – sweet
oil (the sulphur content is no more than 0.5 % of masses), II – sulphurous (the sulphur content is from 0.51 to 2 % of masses), III – high-sulphur (2 % of sulphur and
higher).
Oils are divided into three types depending on the yield of light fractions distilled up to 350 °С: Т1 – no less than 45 %, Т2 – 30-44.9 %, Т3 – less than 30 %.
Oils are divided into four groups - under the content of base oils: М1 – no less
than 25 % counting upon oil; М2 – 15-25 % counting upon oil and no less than 45 %
counting upon mazut; М3 – 15-25 % counting upon oil and 30-45 % counting upon
mazut; М4 – less than 15 % counting upon oil.
There are two subgroups (I1, I2) that are based on the quality of basic oils estimated by viscosity index.
If the oil contains no more than 1.5 % of paraffin it belongs to the lowparaffinic oil (P1), if the paraffin content is 1.5 - 6 % – to paraffinic oil (P2), in case of
more than 6 % – to high paraffinic oil (P3).
103
According to the technological classification each sort of oil has a code. For
example, Т1М3I1P2 – means that it is high-sulphur paraffin oil with the light fractions
content of over 45 %, oils – of 15-25 % counting upon the oil and its viscosity index
is more than 85.
Technological classifications also include some more specific types - for example – classification of oils for choice the way of transportation.
Chapter 2
CHEMICAL COMPOSITION OF OIL
—————————————————————————————————
2.1. HYDROCARBONS OF OIL AND PETROLEUM DERIVATIVES
Hydrocarbons are the simplest organic compounds. Their molecules are built
up of atoms of two elements – carbon and hydrogen. General formula – CnHm. They
are differed on the constitution of the carbon skeleton and bond types between carbon
atoms (fig 2).
hydrocarbons
acyclic
(aliphatic)
saturated
сyclic
alicyclic
unsaturated
cyclоalkanes
C nH2n
alkanes
С nH2n+2
aromatic
cyclоalkenes
cyclоalkynes
not benzenoid
arenes
(benzenoid)
alkenes
C nH2n
alkynes
С nH2n-2
alkadienes
C nH2n-2
polyunsaturated
hydrocarbons
Fig. 2. Classification of hydrocarbons
According to the structure of carbon chain hydrocarbons are divided into acyclic (aliphatic), which molecules include open carbon – carbon chains, for example,
hexane and isohexane:
104
СН3
СН3-СН2-СН2-СН2-СН2-СН3
hexane
СН3-СН-СН2-СН2-СН3
isohexane
and cyclic (carbocyclic) hydrocarbons.
The separate classes of carbocyclic hydrocarbons that have distinguishing features («aromatic character») are called aromatic, for example:
H
C
H C
H C
C
H
C H
H C
C H
H C
H
C
C
H
C
C
H
benzol
C
C
C
H
C
H
H
naphthalene
Other carbocyclic hydrocarbons, for example, cyclohexane, are called alicyclic:
Н2С
Н2С
СН2
СН2
СН2
СН2
сyclohexane
Hydrocarbons can be saturated and unsaturated – depending on bond nature between carbon atoms. The latter can contain a various amount of double (alkenes, alkadienes, cycloalkenes, etc.), triple (alkynes, cycloalkynes, etc.) or both double and
triple bonds:
СН3
СН3
СН2
СН
СН2
С
СН
СН
Н2С
СН2
isoprene
(2-methyl-1,3-butadiene)
propylene
(propene)
Н2С
СН3
СН3
С
СН
methylacetylene
(propyne)
СН3
С
СН
СН2
СН2
сyclohexene
СН
СН2
С
2-methyl-2-hexene-5-yne
2.2. ALKANES
2.2.1. Structure, isomerism, structural formulas
СН
105
Alkanes – aliphatic hydrocarbons containing atoms of сarbon that are connected to themselves and to atoms of hydrogen with a single bond (σ-bond). Hence,
their other name – paraffins, or saturated hydrocarbons. The first and the simplest
member of alkane’s row is methane, СН4. Molecules of methane and of other alkanes
contain carbon atom in the state of sp3-hybridization.
The general formula of compounds of this series is СnH2n+2. Each consequent
representative differs from previous on group CH2 (the methylene group, tab. 2).
Such series of affine organic compounds with the same structure, close chemical and
physical properties that are changed regularly are called homologous series; members
of these series – homologues.
Homologous series of alkanes is often named methane series according to the
title of the first member. Three first compounds have no isomers. But from the butane
the phenomenon of isomerism is observed, i.e. existence of several compounds with
equal quality and quantitative composition and with equal molecular mass but with
different physical and chemical properties.
The constitution of butane С4Н10 can be represented with the help of two formulas:
CH3
CH2
CH2
CH3
CH3
CH
CH3
CH3
isobutane
n-butane
Such type of isomerism is named as a chain isomerism (in this case – the isomerism of a carbon skeleton). Hydrocarbons with a linear carbon chain are named
hydrocarbons of “normal constitutions” (n-butane). Increasing of carbon atoms in the
molecule of alkane leads to the increasing of isomers; so, it is possible to write formulas of three isomers for hydrocarbon С5Н12:
C H3
C H3
C H2
C H2
n -pentane
C H2
C H3
CH3
CH
C H3
C H2
is opentan e
C H3
H 3C
C
C H3
C H3
neopentane
Hexane (С6) has 5 isomers; decane (С10) – 75, eicosane (С20) – 336319.
The formulas of isomers of butane and pentane mentioned above are structural.
They display not only the number and sorts of atoms in the molecule, but also the
order and type of bonds between them. Two kinds of formulas exist: total, or the constitutional:
106
H
H
H C
H C
H
H
H
H
H C
C
C
C
H
H
H C
H
H
C
H
H
H
H
isooctane
and brief or link:
6
CH
3
5
CH3
CH3
7
CH
CH
2
3
4
C
2
CH
1 3
CH
3
8
isooctane
There are four types of carbon atoms in isooctane: atoms 1,5,6,7,8 are connected only with one carbon atom – such atoms of сarbon are named primaries, atom
3 is connected with two other carbons and is called secondary, atom 4 is connected
with three other carbons and is named tertiary carbon atom. The carbon atom 2 is
called quaternary. According to this approach atoms of hydrogen connected with appropriate carbon atoms are called as primaries, secondaries and tertiaries.
2.2.2. Nomenclature
There are several methods of denomination of organic compounds: trivial (historical) names, rational and regular nomenclatures.
Trivial names are usually connected with sources or with first methods of obtaining or with names of scientists or are casual. They do not illustrate the structure of
molecule and in most cases arose in the starting period of chemistry evolution.
According to rational and regular nomenclatures names of organic compounds
not only indicate the type and number of atoms but also represent the structure of organic molecule.
The most convenient is the regular nomenclature of organic compounds; it is
able to name any compound using system of rules that were designed by the nomenclature commission of organic compounds – International Union of Pure and Applied
Chemistry –abbreviated as IUPAC.
The first four representatives of alkanes have casual names: methane, ethane,
propane, butane. Names of next alkanes are also trivial although they are derived
from Greek numerals corresponding to the number of carbon atoms in the molecule
of alkane (with exception of nonane and undecane that have Latin roots, tab.2); the
ending "-ane" is overall for all homologues. These names do not show the constitution of alkanes (normal, branched chain, etc.) and, therefore, can be used only for
names of alkanes of the normal constitution.
107
For denomination of alkanes with branched carbon chain it is necessary to
know names of hydrocarbon radicals – alkyls; there are molecules of hydrocarbons
without one atom of hydrogen. Their names are foremed from names of corresponding alkanes by replacement of ending "-ane" with "-yle". That is why they are named
"alkyls". The general formula of alkyls is CnH2n+1. In formulas of organic compounds
alkyls are usually designated as Alk or more often as R.
According to IUPAC nomenclature names of branched alkanes are formed as
follows:
1. The longest chain is chosen in a molecule of hydrocarbon:
H3C
CH
CH2
CH
CH3
CH3
CH2
CH2
CH2
CH3
2. Then this chain is numbered from the beginning of carbon atom that is
nearest to the substituent (a radical that has the smaller number of carbon atom):
1
2
H3C
3
CH
4
CH
CH2
CH3
CH2
CH2
CH3
CH2
5
6
CH3
7
3. Hydrocarbon is named in the following order: in the beginning of the name a
location of the substituent is pointed out (a number), then the name of this substituent
is written and in the end – the name of the main chain is added. The hydrocarbon
mentioned above can be called: 2-methyl-4-ethylheptane.
If several identical substituents are present in the main chain their numbers are
designated with Greek numerals (di-, three-, etc.) which is put before the name of
these radicals and their position is pointed out with the same number repeated twice
(or several times – depending on the amount of substituents). For example:
CH3
1
2
CH3
C
3
4
5
CH2
CH2
CH3
2,2 - dimethylpentane
CH3
Let's consider some examples:
1
CH3
3
4
5
CH
2
CH
CH
CH2
CH3
CH3
CH(CH3)2
6
CH2
2,3-dimethyl-4-isopropyloctane
7
CH2
8
CH3
108
1
2
СH3
CH
3
4
CH2
CH
CH3
5
CH3
CH
6,7,8
9
(CH2)3
CH3
C3H7
2,5-dimethyl-4-propylnonane
According to the rational nomenclature saturated hydrocarbons are considered
as derivatives of methane; in its molecule one or several atoms of hydrogen are substituted for radicals. Names are built as follows: all substituents are named in accordance with precedence (pointing out their amount if they are identical); the basis of
the name is word "methane". There are some examples of hydrocarbons and their
names according to the rational and regular nomenclature:
CH3
H3C
C
C2H5
CH2
CH2
CH3
trimethylpropylmethane or
2,2-dimethylpentane
CH3
H3C
CH
CH
CH3
CH3
methylethylisopropylmethane or
2-methyl-3-ethylpentane
These examples demonstrate that the regular nomenclature is more convenient
and perfect.
2.2.3. Physical properties
The four first representatives of methane series are gases, hydrocarbons of the
normal constitution from pentane (С5) to hexadecane (С16) are liquids and from heptadecan (С17) and higher – solid compounds. The increasing of molecular masses of
normal alkanes in methane series leads to the increasing of boiling and melting points
and densities (see tab. 2). The difference in boiling points of neighboring homologues
of normal alkanes С5–С10 is 20-30 °С and gradually diminishes to 15 °С for alkanes
(С15–С20).
Alkanes with a branched chain of carbon atoms boil at lower temperatures in
comparison with alkanes of the normal constitution; the increasing of the number of
substituents leads to the increasing of the difference in boiling points between alkanes
of normal and branched constitution. The same regularity is observed for the density;
it is well illustrated in tab. 3.
All conformities mentioned above become clear if you try to take into account
that phase transition between liquid and gaseous states demands to overcome intermolecular interactions. The shape of branched molecules tends to be spherical, so
their area of surface is diminished, intermolecular forces are diminished too and the
lower temperature is needed to overcome these forces.
109
Melting points of alkanes greatly depend on the structure of their molecules, or
on their ability "to be packed" into crystals. Therefore, melting points of 2,2dimethylbutane and 2,3-dimethylbutane (tab.3) are –99.7 °С and –128.4 °С respectively.
All alkanes are easier than water; their density does not exceed 0.8 g∙cm-3.
Alkanes are practically insoluble in water, but there are good soluble in organic
solvents. Methane, ethane and the highest homologues have no odour; middle alkanes
have the odour of benzine. Chains of carbon atoms in molecules of alkanes have the
zigzag shape. The valence angle between carbon atoms is 109°28′; the bond distances
“carbon – carbon” and “carbon – hydrogen” are 0.154 and 0.11 nanometers respectively.
109°28 '
0.164
During the development of oil fields physical conditions and properties of hydrocarbons are changed with the change of temperature and pressure. To correct a
technological regime of maintenance of deposits and systems of oil and gas gathering
it is necessary to know the change of states and properties of hydrocarbons in the
wide range of pressure and temperature.
2.2.4. Chemical properties and processing
It is known that all atoms in molecules of alkanes are linked to themselves by
strong σ-bonds, and valences of carbon atoms are completely saturated with hydrogen. Therefore, alkanes do not enter into reactions of addition. They demonstrate rather high chemical inertness at usual conditions: do not react with ionic reagents (acids, alkalis), oxidizing agents and active metals (therefore, for example, sodium can
be kept in kerosene).
That is why saturated hydrocarbons were called paraffins (from Latin
“рarum affinis” – small affinity).
Main chemical transformations of alkanes are possible only as excessive energy process (heating or UV radiation). Two possible reactions take place in this case:
spliting a С–H bond with consequent replacement of hydrogen by other atom or
group (replacement spliting reactions) and spliting a C–C bond (decomposition).
In spite of the fact that the energy of C-H and C-C bonds are 376.8-410.3 and
314-368.4 кDj / mole respectively, spliting a С–H bond is more preferably due to the
greater accessibility of this bond for the attack by chemical reagents.
The following reactions represent the greatest interest for petrochemistry:
110
Halogenation. It goes rather easily with the substitution of hydrogen for halogens. Chlorine is the most widely used substituent among other halogens because of
its accessibility, cheapness and high reactivity.
It has been established by N.N.Semyonov that this reaction proceeds according to the chain-radical mechanism. Under the action of light molecular chlorine decomposes on atoms which initiate a radical process. Chlorine atom eliminates hydrogen from methane with the formation of free radical – methyl and hydrogen chloride.
The chemically active methyl radical interacts with molecular chlorine and forms a
stable product - methyl chloride, which is converted to other products of chlorination
by the same way with a consecutive formation of methylene chloride, chloroform and
carbon tetrachloride:
Сl Cl
Cl + Cl
H3C H + Cl
H3C + H Cl
methane
methyl
H3C
+
Cl Cl
H3C Cl + Cl
methyl chloride
CH3Cl + Cl
CH2Cl + HCl
CH2Cl + Cl Cl
CH2Cl2 + HCl
methylene
chloride
СH2Cl2
Cl2
-HCl
Cl2
CCl4
HCl
chloroform
perchloromethane
CHCl3
This way of chlorination is typical of other alkanes. In industry chlorination of
hydrocarbons is carried out both in vapour and liquid phases by different methods:
under heating at 400-500 °С (thermal chlorination), at the presence of catalysts (catalytic chlorination) and by the action of light (photochemical chlorination).
Chlorinated derivatives of methane and other lowest alkanes are good dissolvents of fats, synthetic resins and rubbers, nitrocellulose and acetyl cellulose. They
can be used for clearing of wells from asphalto-gum and paraffin depositions. Alkyl
chlorides also are applied to dewaxing of oils.
Chlorinated derivatives of alkanes are used for production of alcohols, including highest alcohols:
C5H11Cl + KOH
C5H11OH + KCl
Passing of methyl chloride (or its mixture with chlorine-containing aromatic
hydrocarbons) over silicon copper at 300 °С leads to alkyl- and arylchlorosilanes:
111
C 6H5
SiCl2
CH3Cl + C 6H5Cl + Si
CH3
Alkyl- and arylchlorosilanes are starting products in the synthesis of silicoorganic compounds that are used for the production of silicone fluids, lubricant greases,
resins and rubbers.
Chloroform and carbon tetrachloride are used for making chlorofluoro- and
fluoroderivatives that are employed as refrigerants – freons:
CCl4 + 2HF → CCl2F2 + 2HCl
.
Completely fluorinated alkanes are used as inert heat-carrying agents and for
the production of polymers – fluoroplastics.
Chlorination of solid paraffins is used for the obtaining of dopants that are depressed a set point of oils (depressant dopants).
Nitration. Nitration of alkanes is carried out with the help of a nitric acid at the
temperature of 200-450 °С. Nitration is always accompanied by partial decomposition of hydrocarbons with the formation of nitrocompounds that contain smaller
number of carbon atoms. For example propane forms not only 1- and 2-nitropropanes
but also nitroethane and nitromethane:
CH3
CH2
CH3
CH2
CH2
NO 2
CH3
CH
CH3
2-nitropropane
1-nitropropane
NO 2
CH3
CH3CH2
СH3
NO 2
NO 2
nitroethane
nitromethane
Nitromethane, nitroethane and nitropropane are good dissolvents for ethers of
cellulose, polymers and varnishes. They can be applied as components for the lowering of self-ignition points of diesel fuels.
Reduction of nitroalkanes in acidic medium leads to amines. Amines are used
for obtaining corrosion inhibitors, surfactants and for sanitation of gases from hydrogen sulphide:
+
R NO2 + 3 H2
H
Pt
R
NH2 + 2 H2O
112
Sulphonation. Concentrated (fuming) sulphuric acid sulphurizes alkanes at
weak heating: the atom of hydrogen is substituted for the sulphonic-acid group:
R H + H2SO4
R SO3H +H2O
As a result alkanesulphoacids are formed.
Sulphochlorination. The reaction of sulphur dioxide and chlorine with alkanes
leads to sulphochlorination:
R H + SO2 + Cl2
UV
R SO2Cl + HCl
alkylsulphochloride
Sulphochlorides are easily hydrolyzed to sulphoacids:
R–SO2Cl + H2O → R–SO3H
Reaction of sulphochlorides with the excess of ammonia leads to sulphamides:
R–SO2Cl + NH3 → R–SO2NH2 + HCl
Sulphoacids can be also obtained by sulphooxidation:
2 R–H + 2 SO2 + O2 → 2 R–SO3H
Alkanesulphoacids form salts with alkalis – sulphonates:
R–SO3H + NaOH → R–SO3Na + H2O
Sulphonates and sulphamides with 12-18 and more carbon atoms that can be
obtained from liquid paraffins evolved from diesel fractions serve as surface-active
and emulsifying agents of oil and flotation agents.
Dehydrogenation. In the presence of catalysts and heating alkanes undergo the
elimination of hydrogen - as a result of the cleavage of С–H bond – with the formation of alkenes. For example, dehydrogenation of ethane leads to ethylene:
C H3C H3
C H2
C H2 + H2
As a result of dehydrogenation of butane butylene and butadiene are formed:
Cr2O 3
CH 2
CH
CH
CH 2
bu tad iene
C 4 H 10 580°
CH 2
CH
CH 3
1-bu tene
CH 3
113
The product of this reaction - mixture of isomeric butylenes - is widely applied
for production of polymeric benzines and synthesis of alkylates, which are highoctane components of benzines.
Dehydrogenation of butane is very important for the production of butadiene –
a valuable starting material for the synthesis of rubbers:
C 4H10
600-620°
CH2
Ca 8Ni(PO4)6
+ Cr2O3
CH
CH
CH2 + 2 H2
Dehydrogenation of isopentane evolved from natural gasoline and oil-refinery
gases leads to isoprene - the important intermediate for the synthesis of rubbers:
C 5H12
CH2
C
CH
CH2 + 2 H2
CH3
Dehydrogenation of the lowest alkanes at very high temperatures leads to acetylene:
2 C H4
C 2H6
1500°
1100-1200°
CH
CH
C H + 3 H2
C H + 2 H2
Isomerization. Under the action of catalysts and at heating alkanes isomerize
to the branched hydrocarbons:
CH3CH2CH2CH2CH3
pentane
AlCl3
100°
CH3
CH
CH3
CH2
CH3
isopentane
The process of isomerization is used for the raise of octane value of benzines.
Oxidation. Alkanes completely burn in the presence of the large excess of
oxygen (or air) and at high temperature with the formation of water and carbon dioxide:
CnH2n+2 + (3n+1) O2 → n CO2 + (n+1) H2O
This process is used for obtaining a thermal energy from natural gas and petroleum derivatives.
Partial oxidation of methane by oxygen of air leads to the formation of carbon
oxide and hydrogen, called as synthesis gas:
114
CH4 + 0.5 O2
800-900°
CO + 2 H2
Synthesis gas is also obtained by conversion of methane with steam or carbon
dioxide:
Ni
C H4 + H2O
700-870°
C H4 + C O 2
800-1000°
C O + 3H 2
Ni
2C O + 2H 2
Synthesis gas is used for obtaining of many organic products.
Oxidation of alkanes by oxygen of air in mild conditions leads to the formation
of mixture of carboxylic acids, alcohols, aldehydes, ketones.
It is possible to produce methanol, formaldehyde and formic acid by oxidation
of methane and products of its oxidation:
CH 4 + 0.5 H 2 O
CH 3 O H + 0.5 O 2
HCHO + 0.5 O 2
Cu
CH 3 OH
220-280°
Cu (Fe,Mo)
600-700°
(300-400°)
HCHO + H 2 O
HCO O H
Methanol is a valuable agent for prevention of gas-hydrate formation in pipelines; it is also applied as a combustible and dissolvent.
Formaldehyde is used in many organic industrial syntheses, for example, for
production of plastics, plastifiers, explosives; it is also applied for prevention of bacterial metallic corrosion and for the extirpation of sulphatereducing bacteria.
Partial oxidation of ethane leads to methyl alcohol, СН3ОН, and ethyl alcohol,
С2Н5ОН and acetaldehyde СН3СНО. The air starved for oxygen is used for prime deriving of alcohols.
Partial oxidation of butane is very important for the industry because it leads to
the great amount of aldehydes, ethyl acetate and acetic acid:
CH3CH2OH + CH3CHO acetaldehyde
O
CH3
CH2
CH2
CH3 + O 2
CH3
2CH3
ethyl acetate
C
O
C 2 H5
COOH acetic acid
The relationship between products of oxidation depends on the temperature of
the process and can be changed in broad extents.
115
Oxidates of the lowest alkanes can be used in the synthesis of dopants, scours,
alkylation agents, ingredients of rocket fuel and dissolvents.
Catalytic oxidation of highest alkanes (С12–С25) (worked out by academician
S.S.Nametkin) has the important industrial significance because it leads to highest
fatty alcohols and acids. Starting materials for this purpose are paraffins that were obtained from petroleum derivatives:
CH3 (CH2)m CH2OH
CH3
(CH2)n
CH3
KMnO4
mixture of alcohols
100-120°
CH3
(CH2)m
COOH
mixture of acids
These products are used for obtaining of surfactant species, scours and plastifiers.
Complexation. Gaseous alkanes form solid complexes with water. There are
intercalation compounds or clathrates. Complexes of gaseous hydrocarbons with water are formed at the temperature near 0 °С. Sometimes these complexes cause the
blockage of gas conduits. In the presence of gaseous molecules liquid water crystallizes with the formation of cages where molecules of alkane ("guest") are placed. So,
propane at the pressure of 0.4 МPа and temperature of 2 °С forms in water crystalline
compound С3Н8·17Н2О.
Alkanes of normal constitution from heptane form at the usual temperature intercalation compounds with urea H2N–CO–NH2. Molecules of urea in these compounds are bridged together by hydrogen bonds and form helical hexagonal channels
with the diameter of 4.9 А°; these channels contain molecules of alkane.
Diameter of the effective cross-section of the alkane molecule of nonbranched
structure is 3.8-4.2 А°. Therefore, molecules of n-alkanes can be placed into this
channel in contrast to molecules of isoalkanes with much greater diameter. That is
why it is possible to separate n-alkanes from branched analogs. However, slightly
branched alkanes with the straight chain of 10 carbon atoms also form stable complexes with urea.
Thiourea
S
H2 N
C NH2 forms intercalation compounds with isoparaffins. Diameter
of hexagonal channels that are formed by molecules of thiourea is 7 A; therefore,
molecules of even highly branched alkanes can be easily placed into these channels.
Molecules of hydrocarbons in clathrates of urea and thiourea are retained with the
help of Van der Waals forces. Probably, the presence of weak hydrogen bonds is also
possible.
2.2.5. Alkanes of oil
116
Alkanes occupy the extremely important place among petroleum hydrocarbons.
So, natural gases almost completely consist of alkanes.
The overall alkanes content of oils is 40-50 % (vol.) and attains 50-70 % in
some oils. However, there are oils with the alkane’s content of 10-15 % only.
Light distillates of any oils almost completely consist of alkanes. The growth
of the average molecular mass of oil’s fraction leads to the decreasing of the alkane’s
content. Middle fractions that boil within 200-300 °С contain 55-61 % of alkanes and
in fractions that boil near 500 °С the amount of these hydrocarbons is 19-5 % and
less.
Gaseous alkanes. Hydrocarbon gases are subdivided into natural, associated
and gases of gas condensate deposits depending on deposits and methods of mining.
Natural gases belong to gases of only gas fields. They consist of methane (9399 %) with small impurity of ethane, propane, butanes and pentanes. There are also a
large amount of carbon dioxide, nitrogen, hydrogen sulphide and noble gases (Ar,
Ne, etc.).
The majority of natural gases belong to so-called dry gases because of the great
predominance of methane.
Gas-fields are placed in different regions of our country. Western Siberia is especially affluent in natural gas.
Associated gases. It is the name of hydrocarbon gases accompanying the crude
oil. These gases are dissolved in oil because of the seam pressure and are evolved
during the mining of oil when the pressure is decreased. It is typical the high content
of methane and the large amount of ethane, propane, butanes and higher hydrocarbons up to octane for these gases. In contrast to dry gases these hydrocarbons are
called aliphatic or affluent gases. Their composition is changed in broad ranges and
depends on the type of a deposit and conditions of the oil production. Associated gases are a source of the light benzene.
Gases of gas-condensate deposits. Some gas fields with a high seam pressure
(within 25-30 МPа) are affluent in liquid petroleum hydrocarbons. During the development of these deposits the pressure is decreased, liquid hydrocarbons condense and
can be separated from gas as a liquid condensate that contains benzene and kerosene
fractions. The gas after separation is closed in content to dry gases.
Chemical composition of gases of different deposits is given in tab. 4.
Natural gases are widely used as household and industrial fuels, serve as the
most valuable raw material for chemical and petrochemical industry. The liquefied
petroleum gases are used as dissolvents for extraction of residual oil from the layer.
Liquid alkanes. The content of liquid alkanes depends on the oil field and can
be changed within 10 - 70 %. Mangyshlak, Siberian, Tatarstan and Bashkortostan oils
are most rich of these alkanes. During fractional distillation liquid hydrocarbons are
divided into benzine (С5–С10) and kerosene (С11–С16) distillates. Nowdays all possible isomers of pentane, hexane and heptane are found in oils.
Usually oil contains from twenty to forty individual normal and branched alkanes; others are present in trace amounts.
117
The most typical compounds are alkanes of normal and slightly branched structure. The last group contains mainly methyl substituted hydrocarbons.
Average data on the content of individual alkanes in benzine fractions of oils
are given in tab. 5.
Now it is revealed 17 of 18 possible isomers of octane and 24 of 35 possible
isomers of nonane.
Ten isomers of decane are selected and most others are detected by spectral
methods.
Undecane, dodecane, three-, tetra-, penta- and hexadecanes are found among
hydrocarbons С11–С16.
In some oils isoprenoic hydrocarbons – branched alkanes with a regular interleave of methyl substituents in a chain through three methylene groups – are detected:
H3C CH CH2 CH2 CH2 CH CH2 CH2 CH2 CH CH2 CH2 CH2 CH CH3
CH3
CH3
CH3
CH3
Their content in different oils is up to 9 %.
Isoprenoic hydrocarbons represent especial interest for the geochemistry of oil
because their structure is typical for biochemical ingredients. Peculiarities of the constitution and high concentration in various oils confirm their biogenic nature.
The distribution of normal and isoalkanes depends on the oil type. Normal alkanes (up to 50 %) are predominated in oils of methanoic type. Oils of naphthenic
type contain predominary isoalkanes (up to 75 % and more). They could be formed in
oils from phytol – unsaturated phytogenic aliphatic alcohol which is a constituent of
chlorophyll.
Oils of methanoic type are older; so, predominance of normal alkanes in them
is explained by elimination reactions of side chains of isohydrocarbons. In this connection the predominant content of isoalkanes in naphthene oils confirms that they
have more young age.
Liquid alkanes have the great importance because they form liquid fuels. It is
established, that normal alkanes have detonating properties, therefore, their presence
in benzines is undesirable.
On the contrary, they are desirable in diesel oil because the increase of chain
length leads to the increase of so-called cetane number which characterizes ability of
diesel oil to the combustion.
Branched alkanes have antiknoking properties that are characterized by octane
value of benzines.
Liquid alkanes as a part of benzine, kerosene and other products of petroleum
refining are used first of all as a fuel. Large amounts of them are applied for production of synthetic fatty acids, alcohols and surfactants. Besides that, they are a good
raw material for the microbiological manufacturing of protein–vitaminized concentrates.
118
Solid alkanes. Solid alkanes are present in all types of oils. They are named
paraffins. Paraffins are present in oils in small concentration (0.1-5 %). However,
some oils contain 7-27 % of solid alkanes.
The predominant amount of paraffins is contained in mazut (its distillation
gives fraction of hydrocarbons C17-C35); other hydrocarbons, С36–С55, remain in tar.
Chemical composition of hydrocarbons, isolated from lube cuts, corresponds to normal alkanes (more than 75 %) and small amounts of cycloalkanes and branched hydrocarbons. They have melting point of 45-54 °С, boiling points – up to 550 °С, a
density of 0.860-0.940 and molecular mass – 300-500.
Solid hydrocarbons С36–С55 are called ceresines. They contain alkanes of normal and isometric structures with cyclic and aromatic fragments. Ceresines have
melting points 65-88 °С, their boiling points are higher than 600 °С, molecular mass
– 500-750. They are similar to wax.
Paraffins are easily crystallized as plates and plate ribbons. Ceresines are crystallized as shallow needles, therefore in contrast to paraffins they do not form firm
congealing systems.
Paraffins are dissolved and suspended in oil. Their solubility depends on the
temperature: it is rather small in the cold but becomes unconfined at heating up to 40
°С. Due to the high temperature in the Earth’s bowels paraffins are dissolved in oils
but they precipitate as a solid phase during the rise of oil on the surface. Therefore,
the presence of paraffins within 1.5-2 % leads to the formation of deposits in holes
and trade collecting mains and hinders the maintenance of holes and transport of oil.
Paraffins and ceresines have diverse application in chemical industry, for example, in production of vaseline, impregnation of wood, dressing of cloths; they are
used as insulating materials in electro- and radio engineering.
Paraffins are applied as stiffeners in the production of plastic lubricants. As
well as liquid alkanes they have the great significance for the production of synthetic
fatty acids and alcohols.
2.3. CYCLOALKANES
Cycloalkanes or cyclanes are cyclic hydrocarbons made up of carbon atoms
(carbocyclic compounds), linked by σ-bonds. According to the classification mentioned above cyclanes are the part of alicyclic compounds. The general formula of
cycloalkanes is CnH2n. Hence, molecules of cyclanes without substituents consist of
СН2 groups (methylene groups) that form rings; that is why their other name is polymethylene compounds.
In technical and oil literature cycloalkanes are usually called naphthenes.
These hydrocarbons were discovered by V.V.Markovnikov in Baku oils in 1833.
According to the number of cycles in the molecule cycloalkanes are subdivided
into monocyclanes (general formula – СnН2n), bicyclanes (СnН2n-2) and polycyclanes
(СnН2n-4, СnН2n-6, etc.).
119
2.3.1. Nomenclature and isomerism
2.3.1.1. Monocyclanes
Names of cycloalkanes are formed by adding a prefix “cyclo-“ to the name of
the corresponding linear alkane with the same number of carbon atoms:
H2 C
H2 C
CH2
H2 C
CH2
CH2
H2 C
cyclopropane
cyclobutane
H2C
H2 C
C H2
CH2
C H2
H2 C
CH2
C H2
H2C
C H2
CH2
cyclopentane
cyclohexane
Substituted cycloalkanes are named and numbered as their acyclic (noncyclic)
analogs:
H CH3
C
H2C
C H2
H2C
H2C
H2C
C C 2H5
C H
H2
C
CH3
CH3
CH2
CH2
1,1-dimethylcyclopentane
1-methyl-3-ethylcyclohexane
As a matter of convenience cycloalkanes are often represented as geometrical
figures. It is meant, that carbon atoms are present in all angles of the figure and all
loose valences are engaged in hydrogen atoms:
CH3
CH3
CH3
cyclohexane
CH3
1-methyl-2-propylcyclopentane
1,3-dimethylcyclohexane
The following types of an isomerism are possible for cycloalkanes:
a) The isomerism connected with the size of the cycle:
CH3
methylcyclopropane
cyclohexane
120
b) The isomerism connected with the position of substituents in the cycle:
CH3
CH3
CH3
CH3
CH3
1,3-диметилциклогексан
1,2-диметилциклогексан
CH3
1,4-диметилциклогексан
c) Side-chain isomerism:
CH3
CH2CH2CH3
propylcyclohexane
CHCH3
isopropylcyclohexane
d) The isomerism connected with stereoorientation of side chains or geometrical (cis-, trans-) isomerism:
CH3
CH3
CH3
trans-1,2-dimethylcyclopentane
CH3
cis-1,2-dimethylcyclopentane
2.3.1.2. Bicyclical alkanes
Two cycles form a condensed system if they have two common neighboring
carbon atoms. If these two common atoms are non-adjacent there is a bridging system. Cycles that are connected by the ordinary bond are named ensembles of cycles.
H2
H2
C H C
H2C
C
C H2
H2C
C
C H2
C H C
H2
H2
condensed system
bicyclo[4.4.0]decane
H2
C
H2 C
H2C
C H2
CH2
C H2
C
H2
bridging system
bicyclo[2.2.1]heptane
ensemble cycle
bicyclohexyl
(bicyclohexane)
Nodal atoms are the most displaced atoms. Chains of atoms that are connected
nodal atoms in the molecule are called bridges.
The condensed and bridging systems consisting only of two cycles are named
as well as alkanes with the same total number of carbon atoms adding a prefix "bicyclo-". Number of carbon atoms in each of three bridges is indicated in square brackets
121
between the prefix "bicyclo-" and the name of hydrocarbon. Numerals are mentioned
in the order of decrease and separated with points.
Ensembles of two identical cycloalkanes are named with the help of prefix "bi" that is written before the name of the corresponding monovalent radical or before
the name of the corresponding hydrocarbon.
Ensembles of different cycloalkanes are named using a more complex cycle as
a basic and another one is named as a substituent:
cyclopentylcyclohexane
2.3.2. Physical properties
Physical properties of some cycloalkanes are given in tab. 6.
According to these data it is clear that cycloalkanes have higher boiling and
melting points than that of corresponding alkanes. This is a result of the more close
packing of cycloalkanes molecules in liquid or solid states and more strong action of
intermolecular forces.
The presence of one alkyl substituent in cycloalkane molecule disturbs it‘s
symmetry and leads to the sharp decrease of melting point.
The order of substituents influences on the boiling point. For example, cycloalkanes with substituents at neighboring carbon atoms in the cycle boil at higher temperature.
Melting points of monoalkylated cycloalkanes are much lower than that of corresponding alkanes.
The increase of the number and lengths of alkyl substituents leads to the closing of physical properties of cycloalkanes and appropriate alkanes.
2.3.3. Chemical properties and processing
Chemical properties of cycloalkanes are similar to alkanes. They are rather inert towards different reagents and enter into chemical reactions in very rigid conditions only or in the presence of catalysts. However, cycloalkanes are more active than
alkanes in reactions with sulphuric and nitric acids. In the presence of catalysts (platinum, palladium and nickel) sixmembered cycloalkanes are dehydrogenated into
corresponding aromatic hydrocarbons (Zelinsky reaction):
Pt
300° C
+ 3H2
122
This reaction became the basis for catalytic reforming (platforming) that is
used for obtaining of benzene homologes: high-octane components to benzines and
raw materials for petrochemical processing. During this process cyclopentane hydrocarbons are isomerizated into cyclohexane derivatives with consequent dehydrogenation into aromatic hydrocarbons. The same reaction easily proceeds in the presence of
aluminum chloride:
CH3
Cyclohexanes as well as alkanes are difficult to oxidize with the formation of
dicarboxylic acids or products without ring destruction. So, in the presence of strong
oxidizing agents (KMnO4, H2SO4, HNO3, etc.) at 100 °С five- and sixmembered
cycles are converted to dicarboxylic acids:
HNO3
100°C
HOOC (CH2)4 COOH
hexane diacid
Dicarboxylic acids are widely used in petrochemical synthesis, for example in
production of polyester and polyamide fibers.
Oxidation of cycloalkanes in mild conditions leads to alcohols (cyclohexanol)
or ketones (cyclohexanone):
OH
сyclohexanol
O
сyclohexanone
O2
Co Cl2
Cyclohexanol is employed as dissolvent for polymers; cyclohexanone is used
for production of caprolactam - starting material for deriving a polyamide fiber – caprone.
O
N
H2N-OH
-H2O
cyclohexanone
OH
H+
oxime of
cyclohexanone
O
NH
caprolactam
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2.3.4. Cycloalkanes of oil and their effect on properties of petroleum derivatives
Oils contain from 25 to 75 % (mass.) of сycloalkanes. The content and distribution of cycloalkanes in fractions is defined by the type of the oil.
Monocyclic cycloalkanes - methyl substituted cyclopentanes and cyclohexanes
- are dominating components of oil. Most of them contain substituents in 1,3- or in
1,2,3-positions. Homologues of cyclohexane are more widespread than that of cyclopentane; it can be explained by peculiarities of the oil origin. Alkylcycloheptanes are
also found in oils in a small amount.
The following condensed bicycloalkanes and their homologues:
bicyclo[2.2.1]heptane
(decalin)
bicyclo[3.3.0]octane
(pentalane)
bicyclo[4.3.0]nonane
(hydrindane)
bridging compounds:
7
6
bicyclo[2.2.1]heptane
(norbornane)
1
8
5
2
3
4
bicyclo[3.2.1]octane
8
7
6
1
9
5
2
3
4
bicyclo[3.3.1]nonane
are found in oils. Decalins are most widespread and have the greate practical significance. There are homologues of bicyclopentyl, bicyclohexyl, cyclopentylcyclohexyl
and bicyclopentylmethane among other bicycloalkanes in oils:
CH2
Only tricyclo[3.3.1.1.3,7]decane (adamantane) and its homologues are detected
in oils among other tricyclic cycloalkanes:
or
A molecule of adamantane is very stable. Its crystal lattice is similar to the lattice of diamond.
124
The highest fractions of oil contain polycyclic alkanes: systems of condensed
4, 5 and 6 cycles with short side chains (terpanes, steranes) – that are derived from
widespread in nature steroids.
Monocyclic cycloalkanes with long side chains as well as condensed cycloalkanes of complex structure are solid compounds at the normal temperature. They are
components of paraffins and ceresines.
Now cyclohexane and derivatives of adamantane only are isolated from oil.
They are used in petrochemical synthesis and other different ranges (medicinal materials, polymers, etc.). Other cycloalkanes of oils are used as additives to benzines or
as raw materials for production of aromatic hydrocarbons.
The high concentration of cycloalkanes in benzines and kerosenes ensures the
high quality of fuels. The knock stability of cycloalkanes lies between normal alkanes
and arenes. Cyclopentane and cyclohexane have the best antidetonant properties.
In diesel oils monocycloalkanes with long side chains are desirable. For rocket
fuels low-branched monocycloalkanes are especially desirable since they evolve a lot
of heat at combustion and have low set points.
For lubricating oils mono- and bicyclic cycloalkanes with long side chains are
more preferable. They have a good viscosity, suitable lubricating properties and low
set points.
2.4. ARENES AND HYDROCARBONS OF MIXED CONSTITUTION
Arenes, or aromatic hydrocarbons are compounds with cyclic group consisting
of six carbon atoms in their molecules which is called the benzene group (benzene
ring):
C
C
C
C
C
C
benzene ring
The name of hydrocarbons of this group "aromatic compounds" is casual and
has lost the original sense now. Really, the first discovered compounds of this row
had specific, sometimes pleasant, odour or were isolated from natural redolent products. But the amount of "fragrant" compounds of this group is insignificant. At the
same time the presence of benzene groups in a molecule causes some peculiarities of
the structure, physical properties and chemical behavior of these substances.
There are mononuclear (one benzene group in a molecule) and polynuclear
(two or more benzene groups) aromatic hydrocarbons. Side chains of arenes may
consist of normal and branched hydrocarbon radicals as well as radicals with double
or triple bonds and cyclic groups:
125
CH3
CH2
benzene
CH
CH3
ethylbenzene
CH
CH3
isopropylbenzene (cumene)
CH2
vinylbenzene
сyclopentylbenzene
diphenyl
CH2
diphenylmethane
naphthalene
phenanthrene
Hence, arenes can contain along with aromatic rings different aliphatic chains
and also include other (nonaromatic) cyclic groups in a molecule.
The first and one of the most important members of homologous series of mononuclear aromatic hydrocarbons is benzene, С6Н6. And the appropriate homologous
series is benzene series.
2.4.1. Structure of benzene
The general formula of monocyclic arenes (CnH2n-6) demonstrates that they are
unsaturated compounds.
German chemist A.F. Kekule in 1865 offered the cyclic formula of benzene with conjugated bonds (alternating ordinary and double bonds) – cyclohexatriene-1,3,5:
H
H С
H С
С
С
С H
С H
H
Such structure of benzene molecule does not explain many of its properties:
1. Typical of benzene are reactions of aromatic substitution, not additional
reactions that are characteristic of unsaturated compounds. Additional reactions are
possible but they flow with more difficulties than that of alkenes.
2. Benzene does not enter into reactions that are qualitative tests on unsaturated hydrocarbons (with bromine water and KMnO4 solution).
To overcome this difficulty Kekule assumed the alteration of a position of olefinic bonds in benzol molecule, i.e. he has put forward the theory of "oscillation" according to which olefinic bonds are not fixed on one place:
126
According to later electron diffraction studies all C-C bond distances in benzene molecule are 0.140 nanometers (average value between lengths of the ordinary
С–С bond - 0.154 nanometers - and olefinic С=С bond - 0.134 nanometers). The angles between all carbon-carbon bonds in the cycle are 120°. So, the molecule is a planar regular hexagon.
The modern structural explanation of molecule С6Н6 deals with hybridization
of orbitals of carbon atoms.
Carbon atoms in benzene molecule are in the state of sp2-hybridization. Each
carbon atom forms three σ-bonds (two of them – with other carbon atoms and the
third – with atom of hydrogen). All σ-bonds are in one plane:
Н
0.140 nм
С
С
Н С
120°
С
Н
Н
С Н
0.109 nм
С
Н
Every carbon atom has one р-electron which does not participate in hybridization. Those nonhybridized electrons are in the plane that is perpendicular to the plane
of σ-bonds. Each р-cloud is overlapped with two others р-clouds and as a result the
united conjugative π-system is formed (fig. 3).
a)
b)
Fig. 3. The mutual overlapping of 2р-orbitals in the molecule of benzene:
a) - the side view; b) - the top view
As a result of such overlapping of 2р-orbitals of all six carbon atoms the "equalizing" of distances of ordinary and double bonds takes place, i.e. classical double and
ordinary bonds are absent in the molecule of benzene. The uniform distribution of πelectronic density between all carbon atoms is the cause of high stability of the molecule.
127
Now a common method of the graphic representation of benzene molecule
does not exist. But to underscore the uniformity of π-electronic density in benzene
one of the following formulas may be used:
Thus, according to modern data bond distances between carbon atoms in benzene ring are the same and correspond to the average value between lengths of the
ordinary and double bonds. However, in condensed arenes not all carbon-carbon
bonds in the cycle are equivalent and therefore a common structure with three olefinic bonds in the ring is used in this case.
2.4.2. Nomenclature and isomerism
2.4.2.1. Monosubstituted benzenes
Simple derivatives of benzene are named as substituted benzols. In this case
the substituent is denoted by a prefix before the word "benzene". So, benzene that has
ethyl group instead of hydrogen atom is called as ethylbenzene. Many benzenes have
trivial names which are widespread:
CH3
CH CH2
methylbenzene
(toluene)
vinylbenzene
(styrene)
CH3
CH CH3
isopropylbenzene
(cumene)
2.4.2.2. Disubstituted benzenes
Three possible isomers of disubstituted benzenes are denoted by prefixes “o
(ortho)-)“, “m (meta-)“, “p (para-)”:
CH3
CH3
CH3
CH3
C2H5
CH3
CH3
о-dimethylbenzene
(о-xylene)
CH3
м-dimethylbenzene
(м-xylene)
p-dimethylbenzene
(п-xylene)
о-ethyltoluene
128
If substituents are different they are listed before the word “benzene” in alphabetic order, for example, о-ethylpropylbenzene.
If one of substituents corresponds to the monosubstituted benzene with a trivial
name (for example, toluene) disubstituted benzene is named as derivative of this
compound.
In contrast to dimethylcycloalkanes dimethylbenzenes are flat and have no
“cis-“ and “trans-” isomers.
In case of two or more substituents in the ring their position can be indicated
by numerals under the condition that numbers of substituted carbon atoms should be
least:
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH CH3
1-methyl-4-isopropyl
benzene (cymene)
CH3
1,3,5-trimethyl
benzene
(mesitylene)
CH3
CH3
1,2,4-trimethyl
benzene
(pseudocumene)
1,2,3-trimethyl
benzene
(hemeliton)
When hydrogen atom is removed from one of carbon atoms of benzene phenyl
group С6H5– is formed, and when hydrogen atom is removed from methyl group of
toluene – benzil group C6H5–CH2– is formed. Groups, derived from aromatic compounds are named “-aryls”.
2.4.2.3. Polycyclic arenes
Hydrocarbons that have two or more benzene rings connected by the ordinary
bond are named bi-, ter-, etc. phenyls according to the number of rings, for example:
diphenyl
terphenyl
Bi- and polyarylalkanes are called as aryl bisubstituted alkanes:
CH2
diphenylmethane
For many condensed arenes trivial names are used:
CH
triphenylmethane
129
9 10
7
6
8
1
5
4
2
7
3
6
naphthalene
9
10
1
1
10
4
2
3
8
7
4
11
9
10
8
1
2
6
5
4
7
1
4
6
3
5
6
chrysene
2
5
4
3
fluorene
1
2
3
1
7
phenanthrene
2
3
6
5
pyrene
5
9
anthracene
8
7
8
9
8
11
2
3
12
4
10
6
9
5
7
8
perylene
Numbers of atoms are used to mark a position of substituents.
2.4.3. Physical properties
The basic physical properties of arenes presented in oils are shown in tab. 7.
Physical properties of arenes are connected with the number of carbon atoms,
number of substituents and their location in the molecule. Arenes have higher boiling
points, than that of the corresponding cycloalkanes. It is caused by more dense packing of their molecules (a flat ring) as well as by more strong physicochemical interaction between molecules due to the presence of π-electrons.
Homologues with o-alkyl substituents boil at higher temperatures than that of
n-isomers.
The symmetrical location of alkyl substituents increases melting points of substituted arenes due to the increase of dense packing of their molecules.
The increase of number of cycles also leads to the increase of melting points.
The appearance of side chains reduces melting points, and elongation of such chains
leads to the increase of melting points.
More hydrogen-rich homologues have a lower density. Arenes with symmetric
location of substituents have the least density owing to the less dense packing in matter. Arenes have maximal density and index of refraction in comparison with other
hydrocarbons; this circumstance is used in analytical practice.
Arenes as contrasted to other hydrocarbons can absorb a radiant energy in ultra-violet spectral range; it is used for their analytical detection.
Arenes also are different from other hydrocarbons by the ability to dissolve selectively in some dissolvents - polar liquids: sulphur dioxide, dimethyl sulphate, sulpholane, acetone, phenol, furfurol, diethylene glycol, aniline, nitrobenzene, etc.
130
Selective solvents are used for industrial isolation of arenes from oil fractions
and petroleum derivatives and also for their separation into individual compounds.
Besides that arenes are capable to be quantitatively adsorbed by silicagel, aluminogel and some other adsorbents. Desorption of highest arenes flows with different
speeds and lets separate and evolve individual aromatic hydrocarbons (or their narrow fractions) from oil fractions by chromatography.
2.4.4. Chemical properties and use
2.4.4.1. Addition reactions
Arenes enter into addition reactions with greate difficulty. For this purpose
high temperature, UV-radiation and catalysts are required.
Halogenation:
Cl
UV
3Cl2
40-60°
Cl
Cl
Cl
Cl
hexachlorocyclohexane
(hexachlorane)
Cl
Hexachlorane is used as insecticide.
Hydrogenation:
3H2
Ni
200-230°
cyclohexane
2.4.4.2. Replacement reactions
Replacement reactions are the most typical of arenes. They take place under rather mild conditions and flow especially easily for homologues of benzene.
Halogenation. Depending on conditions of halogenation it is possible to produce various substituted products:
131
Sulphonation. Concentrated sulphuric acid easily substitutes hydrogen for sulphoxyl with formation of sulphoacid.
H
HO
SO3H
SO 3H
H2O
benzenesulphonic acid
This reaction proceeds quantitatively and can serve as one of methods of determination of the arenes content of oil fractions.
Fusion of benzene sulphonic acid and benzene chloride with alkali leads to
phenol:
C6H5SO 3H
C 6H5Cl
OH
2NaOH
Na2SO3
NaOH
Phenol is used mainly for the production of phenol-formaldehyde resins.
Nitration. Interaction of benzene with mixture of concentrated nitric and sulphuric acids leads to the formation of nitrobenzene:
H
HO NO 2
NO2
H2SO4
H2O
Reduction of nitrobenzene leads to aniline:
NO2
NH2
3H2
2H2O
aniline
Aniline is mainly used for the production of polyurethane cellular plastics.
Complete nitration of toluene leads to the explosive substance – trotyl (2,4,6trinitrotoluene):
132
CH3
NO2
HNO3
NO2
H2SO4
CH3
NO2
2,4,6-trinitrotoluene
Alkylation. In the presence of catalysts, such as АlCl3, HF, H2SO4, HCl, BF3
arenes react with alkenes, alcohols, halogenated alkanes. This is the way for industrial production of ethylbenzene and isopropylbenzene:
CH2
CH2
CH2
AlCl3,HCl
CH3
90-100 °
ethylbenzene
Catalytic dehydrogenation of ethylbenzene leads to styrene and isopropylbenzene – to -methylstyrene – valuable monomers that used for the production of rubbers and plastic:
CH2
CH3
600-630°
CH
Fe2 O 3+Cr2O3+NaOH
CH2
styrene
Alkylation of benzene with chlorine alkanes both the further sulphonation and
neutralization of products leads to alkylarylsulphonates – synthetic surfactants. These
materials (with some additional components) are named sulphonоls:
C6H6
RCl
HCl
H SO
RC 6H5 H2 O 4
2
RC 6H4SO2OH
NaOH
H2O
RC6H4SO 2ONa
2.4.4.3. Other reactions of arenes
Dealkylation and hydrodealkylation. In connection with the greatest significance of benzene it is obtained now by dealkylation or hydrodealkylation of toluene:
C6H5CH3
Ni
375°, H2O
C6H5CH3
Mo, Co, Cr
600°
C 6H6 CO 2H2
C6H6 CH4
133
Condensation with formaldehyde. In the presence of concentrated sulphuric
acid arenes condense with formaldehyde with the formation of insoluble residue of
brown colour:
R
n
R
[
(n - 1) CH2O
]n
(CH2 )
(n-1) H2O
R
This reaction is used for analytical detection of arenes in oil fractions.
Oxidation. Arenes (with the exception of benzol, naphthalene and other unsubstituted homologues) easily enter into oxidizing reactions. In the series of alkyl
derivatives of arenes resistance to oxidation diminishes with the increase of the chain
length and degree of branching. As the result sour compounds are formed. These
properties of arenes are widely used in industry for deriving oxygen-containing derivatives:
CH 3
COOH
CH3
О2
catalyst
O2
catalyst
CH 3
p-xylene
CH3
COOH
terephthalic acid
о-xylene
O2
phthalic anhydride
CH 3 C
120°,C u
OH
phenol
C H(CH 3 )2
C O
O
C O
CH 3
O
acetone
Different processes of oxidation of toluene are developed for obtaining of terephthalic acid. Benzene and naphthalene are the most resistant to oxidation by air.
However, they are also oxidized in very rigid conditions (high temperature, the catalyst) with the breakdown of a benzene ring:
O2
V2O5,400-450 °
C
O
O
C
O
maleic anhydride
O2
V2O5
C
O
O
C
O
phthalic anhydride
134
Terephthalic acid is the intermediate in the production of synthetic polyester
fiber lavsan (terylene). Phthalic anhydride is used for the production of alkyd- and
polyester resins, plasticizers and insect repellants.
Formation of complexes with phenol trinitrate. Polycyclic arenes (naphthalene, anthracene and their homologues) easily form complexes with phenol trinitrate
(2,4,6-picronitric acid) – so called picrates.
Benzene and its homologues do not form stable complexes and can serve as
dissolvents in the process of complex formation.
Picrates of aromatic hydrocarbons are solid yellow crystalline substances and
have legible melting points. Melting point of a picrate makes possible to identify a
polycyclic aromatic hydrocarbon.
The complex formation with phenol trinitrate is used as a method of isolation
of polycyclic aromatic hydrocarbons. Picrates are easily decomposed by hot water.
Phenol trinitrate dissolves in water and polycyclic aromatic hydrocarbons liberate out
in the free state.
2.4.5. Hydrocarbons of mixed constitution
High-boiling fractions of oil mainly consist of hydrocarbons of the mixed (hybrid) constitution. They are polycyclic hydrocarbons that contain cycloalkan fragments condensed with arenes.
Kerosene-gas-oil fractions contain elementary hybrid bicyclic hydrocarbons
and their homologues:
indan
tetralin
fluorene
acenaphthene
Aromatic cycles of hybrid hydrocarbons in most cases have short (methyl or
ethyl) substituents; cycloalkan rings have one or two rather long alkyl substituents.
Especially high concentration of hybrid hydrocarbons is observed in lube cuts. Their
structure is very little investigated.
Hybrid hydrocarbons are undesirable components of lubricating oils because
they make worse their frictional properties and diminish antioxidation stability.
2.4.6. Arenes of oil, effect on properties of petroleum derivatives;
application
The arenes common content of oils is 10-20 % of mass., and in aromatic oils
their content achieves 35 %. Young oils are the most affluent in arenes.
135
The increase in boiling point of oil fractions for all kinds of oils is accompanied by the raise of arenes content.
The content of monocyclic benzol derivatives in petrol fractions is changed
from 5 up to 25 % and depends on a deposit of the initial oil.
There are all methylsubstituted isomers of benzol up to С10 in these fractions.
Toluene, m-xylene and 1,2,4-trimethylbenzene are base components of oil. 1,3Isomers are dominated among disubstituted homologues of benzene and 1,3,5- and
1,2,4-isomers - among trialkylbenzenes.
The arenes content of kerosene and gas-oil fractions is 15-35 %. Beside that
naphthalene, biphenyl, biphenylethane and their methylderivatives are detected here.
Naphthalene is present in a very small amount; it is the confirmation of common rule:
first members of homologous series are always present in smaller concentrations in
oils in comparison with higher homologues. There are polycyclic arenes, such as
anthracene, phenanthrene, pyrene, fluorene, chrysene, perylene and their alkyl(mainly, methyl-) derivatives in high-boiling fractions.
The arenes average content of different types of Russian oils (in mass. %) are
as follow: benzene – 67 %, naphthalene – 18 %, phenanthrene – 8 %, chrysene and
benzofluorene – 3 %, pyrene – 2 %, anthracene – 1 %, other arenes – 1 %. Homologues of phenanthrene are present in a greater amount than that of anthracene; that is
agreed to the relative content of these compounds in vegetative and animal cloths.
Arenes are desirable components of carburetor combustibles because they have
rather high octane values (toluene – 103, ethylbenzene – 98).
On the other hand the presence of arenes in diesel and reactive fuels are extremely undesirable because of the worse combustion.
Polycyclic arenes with short side chains must be deleted from oils because of
the worsening of operational properties of them.
Arenes are the valuable raw material for petrochemical synthesis: production of
synthetic rubbers, plastic, synfils, aniline dyes, explosives and pharmaceuticals. The
greatest significance is connected with benzene, toluene, xylenes, ethylbenzene and
naphthalene.
2.5. UNSATURATED HYDROCARBONS
Unsaturated hydrocarbons are substances with carbon atoms connected by multiple (double or triple) bonds.
These hydrocarbons are named “unsaturated” because they contain smaller
number of hydrogen atoms than saturated hydrocarbons with the same number of
carbon atoms in the molecule.
Unsaturated hydrocarbons are divided into alkenes, cycloalkenes and alkynes
depending on the number and character of multiple bonds.
2.5.1. Alkenes and cycloalkenes
136
Alkenes are unsaturated compounds that contain olefinic bond С=С. These
compounds used to name “olefins”. The general formula of alkenes is CnH2n.
Unsaturated cyclic rings with one olefinic bond are called as cycloalkenes or cycloolefines (general formula – CnH2n-2).
Unsaturated hydrocarbons that contain two or more olefinic bonds are also
ranked among alkenes and cycloalkenes.
2.5.1.1. Nomenclature
Names of all alkenes are based on titles of corresponding alkanes with the replacement of the ending “-ane” with “-ene”. Main is the chain that contains the olefinic bond. The position of the last is market by the number of carbon atom from
which the double bond begins and this atom has the least number:
CH2
C CH CH2
CH3
CH3
CH3
2-methylpentene-1
CH CH
CH3
CH2
pentene-2
If there are two or three olefinic bonds in the hydrocarbon molecule the ending
“-ane” in the corresponding alkane’s name is replaced with “-diene” or “-triene” according to the number of olefinic bonds with the indication of the position of multiple bonds:
CH2
C CH CH3
CH2
CH CH CH2
butadiene-1,3
butadiene-1,2
For the first members of homologous series of alkenes trivial names are often
used:
H2C
CH2
ethylene
(ethene)
H2C
CH CH3
propylene
(propene)
H2C C
CH2
allene
(propadiene)
CH2
C
CH
CH2
CH3
isoprene
(2-methylbutadiene-1,3)
Names of cycloalkenes and cycloalkadienes are constrained similarly on the
base of cycloalkanes names. In this case numbering begins from the olefinic bond:
137
1
1
2
4
cyclohexene
3
3
cyclohexadiene - 1,3
2
CH3
3-methylcyclohexene
Monovalent radicals of alkenes are named by adding the ending “-enyl”. For
some of them trivial names are more common:
CH2
CH2
CH
ethenyl
(vinyl)
CH CH2
propenyl
(allyl)
In commercial processes of oil processing alkenes are obtained in a mixture
with alkanes. Their properties are quite differing and individual compounds can be
easily separated.
2.5.1.2. Physical properties
Physical properties of alkenes are presented in tab. 8.
Alkenes with 2, 3 and 4 carbon atoms at standard temperature and pressure are
gases, alkenes С5–С17 – liquids and the rest – solid compounds.
Cis-isomers have lower melting points, higher boiling points, density and index
of refraction in comparison with trans-isomers.
The density of alkenes is a little higher, than that of corresponding alkanes.
Alkenes are slightly soluble in water but their solubility is higher than that of
alkanes. They readily dissolve in organic solvents.
Adsorptive ability of alkenes is lower than that of arenes but is higher than that
of alkanes. This is the base of quantitative determination of alkenes in petroleum derivatives by the method of adsorptive chromatography.
Selective absorption of infrared radiation is typical of alkenes; therefore infrared spectra are used for detection and determination of their structure.
2.5.1.3. Chemical properties and use
Chemical properties of alkenes are caused by the olefinic bond. Action of different reagents leads to the break of the less strong -bond; as a result two new bonds are formed. That is why addition reactions are characteristic of alkenes:
C
C
A
B
C
C
A
B
138
Addition of hydrogen (catalytic hydrogenation). Addition of hydrogen to alkenes or cycloalkenes leads to appropriate alkanes or cycloalkanes:
the catalyst
RCH
CH2
R
H2
CH2
CH3
Halogenation. Alkenes add halogens, especially easily - chlorine and bromine
under the normal conditions. As a result, dihalogenated alkanes are formed with halogens at the neighboring carbon atoms.
The reaction of alkenes with bromine is used for qualitative detection of unsaturated compounds in petroleum derivatives, because this process results in the decolouration the brown solution of bromine:
CH3
CH
CH
pentene-2
CH3
Br2
CH3
CH
CH
Br
Br
CH2
CH3
2,3-dibrompentane
Quantitative determination of alkenes in oil derivatives is based on addition
reactions of bromine and iodine; there are methods of bromine and iodine numbers
which have been set up on the determination of equivalent amounts of bromine and
iodine entered into the reaction.
Chlorination of alkenes is of great importance for the production of plastic,
rubbers and dissolvents. Chlorination of ethylene leads to the formation of valuable
dissolvent – ethylene dichloride:
CH2
CH2
Cl2
CH2Cl CH2Cl
ethylene dichloride
From ethylene dichloride vinyl chloride is obtained – the important compound
for the production of polyvinylchloride plastic:
CH2Cl
CH2Cl
480-520°
CH2 CHCl
chloric vinyl
HCl
Sulphonation. Addition of sulphuric acid to alkenes and cycloalkenes is submitted to Маrkоvnikov’s rule: the atom of the negative part of the reagent adds to the
carbon atom, that is connected with the least number of hydrogen atoms. As a result
of the process acidic ethers of sulphuric acid (alkylsulphates) used for deriving surfactants are formed:
CH3
(CH2)4
CH
CH2
H2SO 4
CH3(CH2)n
CH
CH3
OSO 2OH
139
This reaction is also used for clearing and determination of alkenes in petroleum derivatives. Concentration of sulphuric acid that is used for this purpose is no
more than 80-90%, because more concentrated acid reacts with arenes too.
Hydration. Hydration of alkanes (addition of water) is used for the industrial
production of ethyl-, isopropyl- and other monohydric alcohols:
280-290°
C2H4 H2O
CH3CH
H3PO4
C2H5OH
CH2 H2O
CH3
CH
CH3
OH
The most important is ethanol which is used as dissolvent, in the production of
synthetic rubber, polymers, ethers, as a fuel, antifreeze, etc.
Ethyl-, isopropyl- and other alcohols are used for replacement of residual oil.
They are added to acids during the acidic treatment of holes; this process leads to the
decrease of swelling capacity of argillaceous rocks. It promotes the increase of the
scope of the acid’s action on the layer, facilitates the removal of reaction products
from the face zone and increases the efficiency of acid treatments.
Oxidation. Oxidation of ethylene is used for the production of ethylene oxide:
CH2
CH2 0,5 O 2
Hg
CH2 CH2
O
Ethylene oxide is mainly used for the production of ethylene glycol:
CH2
O
CH2
CH2
H2O
CH2
OH
OH
ethylenе glycol
The last is used for the obtaining of polyester fibers, ethanolamines, surfactants
and antifreezes.
Oxidation of the mixture of propylene and ammonia leads to acrylonitrile – the
important monomer for synthetic rubber, chemical fibers (nitron) and other polymers:
CH2
CH
CH3
1,5 O 2 NH3
CH2
CH
CN
3 H2O
Polymerization of alkenes has the important industrial significance.
Ozonolysis. Ozone quantitatively adds to alkenes at room temperature. Aromatic hydrocarbons, that are present in petroleum derivatives in the mixture with alkenes practically do not react with ozone:
140
O O
CH3
CH
CH
CH2
CH3
O3
CH3
CH
O
CH CH2
CH3
Quantitative determination of alkenes in petroleum derivatives is based on this
reaction.
Cycloalkenes and alkadienes also take part in all reactions typical of olefinic
bond and mentioned above.
However, unsaturated compounds with conjugative olefinic bonds have specific properties. First of all it is showed in addition reactions.
Action of halogens, hydrogen and other reagents on alkadienes with conjugated
bonds leads to the addition to edge carbon atoms; the olefinic bond instead of ordinary is formed in the middle of the molecule in this case:
СH2
CH CH CH2 + Cl2
butadiene-1,3
Cl
CH2 CH CH CH2
1,4-dichlorbutene-2
Cl
Addition reactions of alkenes to conjugated dienes (a reaction of diene synthesis) have the grate significance:
HС
HC
CH2
+
CH2
CH2
2H2
CH2
cyclohexene
benzene
It is the base of arenes formation at thermal processing of alkanes.
2.5.2. Alkynes
Alkynes are unsaturated hydrocarbons that contain one triple bond in the molecule. The simplest representative of alkynes is acetylene С2Н2, so they are often
named acetylene hydrocarbons. The general formula of alkynes is С2Н2n-2.
2.5.2.1. Nomenclature
Names of alkynes are formed by the replacement of the ending “-ane” in the
title of the corresponding alkane with “–yne”. The position of the triple bond determines the choice of the main chain and the order of numbering. The trivial name
"acetylene" is conserved for the first member of homologous series. Sometimes these
compounds are named as derivatives of acetylene:
HC CH
ethyne
(acetylene)
HC
C CH3 CH3 C C
CH3
propyne
butyne-2
(methylacetylene)
(dimethylacetylene)
141
Radicals formed from alkynes by eliminating of hydrogen atom have the ending “-nyl”:
CH C
CH
acetenyl
C
CH2
propinyl-3
2.5.2.2. Physical properties
Physical properties of some alkynes are given in tab. 9.
Lowest alkynes С2–С4 are gases, С5–С6 – liquids and highest members - solid
compounds. Boiling point of alkynes is a little higher than that of corresponding alkenes. It is connected with the more strong intermolecular interaction in the series of
alkynes because their molecules have some electrical dipole moment. For the same
reason solubility of lowest alkynes in water is a little higher than that of alkenes and
alkanes; nevertheless, their solubility is very small.
The density and index of refraction of alkynes are much higher than that of alkenes and, especially, of alkanes.
2.5.2.3. Chemical properties
Chemical properties of alkynes are caused by the nature of the triple bond,
properties of sp-hybridized carbon atoms. Typical of alkynes as well as of alkenes are
addition reactions. But of alkynes they proceed slower than that of alkenes.
Hydrogenation. In the presence of catalysts (Pt, Pd, Ni) the addition of hydrogen takes play:
CH
CH
H2
CH2
CH2
H2
CH3
CH3
A triple bond is hydrogenated easier than that of a double bond. The reaction
can be stopped at the stage of alkene formation.
Halogenation. Interaction with halogens flows more slowly than that of alkenes. This reaction is used for obtaining of dissolvents:
CH
CH 2Cl2
Cl2CHCHCl2
ethylene dichloride
Hydrohalogenation. Hydrochlorination of acetylene is used in industry for obtaining of vinyl chloride:
CH CH HCl
150-200°C
HgCl2
CH2
CHCl
Vinyl chloride is a starting material for the production of polymer PVC.
142
Hydration. Direct hydration of acetylene leads to the acetic aldehyde (this
reaction was discovered in 1881 by M.G. Kucherov):
CH
CH H2
O
HgSO4
CH3
C
H
Acetic aldehyde is widely used for obtaining valuable chemicals, for example,
acetic acid:
CH3CHO
O2
the catalyst
CH3COOH
Acetic acid is a starting material for obtaining chemical fibers and plastic, dissolvents and many other products. It is used for acid treatment of high-temperature
holes to increase the petroeffect of layers.
Addition of formonitrile:
CH
CH
HCN
CuCl2
CH2 CH CN
acrylonitrile
Addition of organic acids and alcohols:
CH
CH HOC2H5
CH3СOOH CH
KOH
150-200°C
CH
CH2
ZnO
CH O C2H5
vinyl acetate
O
CH3
C
O
CH
CH2
Vinyl esters – products of the last reactions - are used as monomers for the
production of polymers and plastics.
Oxidation. Alkynes are oxidized easier then that of alkenes. Process is accompanied by the break of carbon – carbon triple bond. Alkynes rapidly decolorize a solution of KMnO4 that can be used as a qualitative test on the triple bond:
3 CH
CH 10 KMnO4 2 H2O
6 CO 2 10 KOH 10 MnO 2
Replacement reactions. Alkynes are notable for high mobility of hydrogen
atoms connected with sp-carbon atoms. These hydrogens are easily substituted for
halogens or metals. In case of metals acetylides are formed.
For example, treatment of acetylene with ammonia solution of CuOH leads to
the formation of red-brown precipitate of copper acetylide:
143
CH
CH 2 [Cu(NH3)2]OH
Cu C C Cu 2 H2O 4 NH3
acetylide of copper
This reaction can be used for the detection of triple bond terminated alkynes
and for the isolation of acetylene hydrocarbons. After precipitation and extraction of
acetylides it is possible to liberate free alkynes with the help of inorganic acids:
Cu
C
C
Cu
2 HCl
CH
CH 2 CuCl
Polymerizations of alkynes have the industrial significance.
2.5.3. Unsaturated hydrocarbons of oil and petroleum derivatives.
Effect on the quality of fuels. Application
It was considered earlier that alkenes are not present in oils or are contained in
a slight amount. But it has been shown at the end of 80-th that alkene’s content in
some oils of Eastern Siberia, Tatarstan and other regions of Russia can reach 15-20
mass % of oil.
Alkenes are also found in a slight amount in Canadian oil: hydrocarbons from
С6Н12 to С13Н26 are selected from it. In a slight amount unsaturated hydrocarbons are
present in products of simple distillation of oil. A fair quantity of unsaturated hydrocarbons is contained in gases of thermal and catalytic processing of oil fractions (up
to 25 %). A large amount of gaseous alkenes is also contained in liquid products of
cracking (benzenes). There are alkenes of normal and brunched structures, cycloalkenes (cyclopentene, cyclohexene and their homologues), arenes with the olefinic
bond in the side chain (styrene, indene and their homologues).
Alkadienes are present in products of vapour-phase cracking and pyrolysis
(from 5 to 10 % mass.); mainly there are 1,3-butadiene, 1,3-pentadiene and cyclopentadiene.
Unsaturated hydrocarbons increase the octane value of combustibles. However,
due to the high reactivity they can be easily oxidized by oxygen of air (especially dienes). As a result deposits and resins are formed; they can destroy the normal working process of motors. That is why obtaining of petroleum derivatives stable to oxidation demands their preliminary purification from unsaturated hydrocarbons or adding
of antioxidants.
Unsaturated hydrocarbons have the greate significance for petrochemical industry because they are the base for the production of a greate amount of petrochemical products.
2.6. HETEROATOMIC COMPOUNDS AND MINERAL
COMPONENTS OF OIL
144
Hydrocarbons containing heteroatoms (O, S, N) are named as heteroatomic
compounds. Heteroatomic compounds: oxygenous, sulphurous, nitrous – are present
in all oils. Oils contain heteroatomic compounds both of cyclic and in much smaller
extent of acyclic structure. A ratio of them and their content depends on the age and
origin of oil.
The amount of heteroatomic compounds in the low-molecular part of oil is insignificant (up to 10 %). A main mass of them are concentrated in the high-molecular
part of oils (up to 40 %) and especially in the tarry-asphalt residue (up to 100 %).
Tarry-asphalt matters dominates in young oils; that is why these oils contain a
large amount of heteroatomic compounds.
Presence of some heteroatomic compounds and their concentration in oils are
of great importance for the solution of the problem of starting material of oil and
processes of its transformation during maturation.
2.6.1. Oxygenous compounds
The concentration of oxygenous compounds in oil attains 10 %. The main part
of oxygen is contained in tarry-asphalt materials (about 90 %). Other oxygenous
compounds are represented by organic acids, phenols, ketones and ethers.
2.6.1.1. Acids
Organic or carboxylic acids are hydrocarbons which contain one or several
carboxyl groups in a molecule:
O
C
OH
The general formula of monocarboxylic acids is R-COOH. The number of carboxyl groups determines the basicity of acids. Acids may be monobasic (monocarboxylic) and polybasic (polycarboxylic). According to the nature of hydrocarbon
groups acids can be saturated, unsaturated and aromatic.
Saturated acids are subdivided into aliphatic (fatty) and cyclic.
Nomenclature. More often carboxylic acids are named according to the trivial
nomenclature. These names are routinely connected with sources from which they
have been selected for the first time: for example, formic acid – from ants, acetic acid
– from vinegar, butyric acid – from oil, etc.
According to the regular nomenclature names of monobasic carboxylic acids
are formed from titles of hydrocarbons with the same number of carbon atoms using
the ending “-ic” and the word "acid". In case of the presence of substituents numbering of the main chain begins with carbon atom of the carboxyl group:
145
5
4
3
2
1
CH3 CH2 CH CH2 COOH
CH3
3-methylpentanoic acid
The carboxyl group itself can be also considered as a substituent; in this case it
is designated by the ending – carboxylic acid.
CH3 CH2 CH CH2 COOH
CH3
2-methylbutane-1-carboxylic acid
COOH
cyclopentanecarboxylic acid
Trivial names are used for widespread natural carboxylic acids. The same rules
work in the nomenclature of bi- and policarboxylic acids:
COOH
HOOC
COOH
dicarboxylic acid
(ethanedioic acid)
HOOC CH2 COOH
propanedioic or
methane-dicarboxylic
(propane diacid)
COOH
benzol 1,2-dicarboxylic acid
(phthalic acid)
To name salts of carboxylic acids the ending “-ate” and a cation’s name are
used instead of ending “-ic” and acid’s name.
Petroleum acids, physical properties and application. All carboxylic acids
that are present in oil and its fractions are named as petroleum acids. They mainly
consist of a mixture of aliphatic and naphthenic acids. The basic part of petroleum acids corresponds to carboxylic derivatives of monocycloalkanes СnH2n-1COOH (n =
5,6,9) that are named as naphthenic acids. Their content of oils is changed from traces up to 3 % (the greatest amount belongs to heart cuts). The majority of naphthenic
acids are derivatives of cyclopentane and cyclohexane with predominance of the first.
The carboxyl group as a rule is in a distance of 1-5 carbon atoms from the cycle:
(CH2)nCOOH (n = 1-5)
The cycle may contain methyl substituents. In some oils bi- and tricyclic С13–
С18 naphthenic acids are detected. The concentration of fatty carboxylic acids
СnH2n+1СООН in oils does not exceed 0.01%. Acids of С1 - С25 are detected. Among
them acids of the isometric structure and acids with the even number of carbon atoms
dominates.
146
In some cases organic acids with a benzene ring in a molecule are detected in
oils. Residual cuts of oils contain carboxylic derivatives of mixed hydrocarbons.
Physical properties of acids are presented in tab. 10.
The first three members of fatty acids are colourless fluent liquids with sharp
stimulating odour that can be mixed with water in all ratios. Beginning with butyric
acid they are oily fluids low soluble in water and with nice odour.
The highest acids beginning with decanoic are solid compounds without odour.
They practically do not soluble in water but dissolve in ether and benzol.
The increase of molecular mass of acids leads to the increase of their boiling
points and decrease of densities. Melting points of acids display the same regularity
that alkanes have. Acids of the isometric structure have lower boiling points than that
of linear acids. Due to the high polarity of О–Н bond carboxylic acids form strong
intermolecular hydrogen bridges. That is why lowest carboxylic acids are less volatile
than it could be expected on the basis of their molecular masses. In all aggregate
states (even partly in gaseous) dimeric molecules with two hydrogen bonds dominates:
R C
O
O H
H O
C
R
O
All dicarboxylic acids are colourless crystalline compounds. Lowest homologues are good soluble in water.
Naphthenic acids have all typical properties of carboxylic acids.
Naphthenic acids isolated of oil are dark oily fluids with unpleasant odour.
They are weak soluble in water and rather good in all organic solvents. Naphthenic
acids have low set points (up to –80°). They strongly depress the interfacial tension of
water, in other words, they are surface-active compounds.
Naphthenic acids react with oxides of metals and with metals at heating forming salts. It results in corrosion of metal instrumentation. Naphthenic acids easily
form salts with lead, zinc, copper, less readily – with iron and more less – with aluminium.
On this cause all naphthenic acids are deleted from petroleum derivatives during clearing. To refine an oil and oil fractions from naphthenic acids their ability (interaction with alkalis, carbonates or oxides of alkali metals) to form salts insoluble in
hydrocarbons but soluble in water is used.
Application. Technical naphthenic acids evolved from kerosene and light oil
distillates are used as dissolvents of resins, rubber, for impregnation of sleepers and
in other productions.
Salts of alkali metals of naphthenic acids have a high surface activity; therefore
they are employed as an emulsion breaker at dehydration of oil and for preparation of
detergents and viscous lubricants.
147
An aqueous solution of sodium salts of the naphthenic acids (40 % mass.), obtained from alkaline waste products at clearing of kerosene and diesel oils, is used as
a material considerably stimulating a rise of agricultural crops.
Salts of naphthenic acids (naphthenates) are also employed as ingredients of
lubricants working under high pressure (lead naphthenate), corrosion-resistant coats
(naphthenates of lead, aluminium, manganese and cobalt), fuel additives (naphthenates of manganese and iron). Naphthenates of copper protect wood and cloths from
bacterial decay.
Sodium salts of naphthenic acids are used in oil industry for the insulation of
inflow of stratal waters: reaction with calcium salts contained in stratal waters leads
to the formation of water-insoluble calcium salts of naphthenic acids. It results in
blockage of rock’s pores and formation of waterproof shields capable to protect
working face of holes.
Naphthenate soap is used as a defoamer in preparation of drilling fluid.
2.6.1.2. Phenols
Organic compounds containing a hydroxyl group connected with benzene ring
are called as phenols.
Physical properties and application. The simplest phenols are liquids or solid
matters with low melting points (phenol – 43 °С, cresols – 11 °С). Phenol is good soluble in water (9.3 g per 100 g of water) because of formation of hydrogen bonds but
the majority of other phenols has bad solubility in water.
Nomenclature. Phenols are named either with trivial names, as derivatives of
simple members of this row – phenol (С6Н5ОН) and cresol (СН3–С6Н5–ОН), or under the regular nomenclature adding the ending “-оl” to the name of aromatic hydrocarbon.
Phenols of oil. The phenols content of some oils can attain 0.1-0.2 %. Significant amount of them can be detected in condensates from deposits with high pressure
and also in stratal waters.
Phenols detected in different oils are as follow:
148
OH
OH
OH
OH
OH
CH3
о-cresol
phenol
м-cresol
OH
H3C
CH3
OH
CH3
xylenol
CH3
p-cresol
C 2H5
naphthol
о-ethylphenol
Treatment of oils with alkali results into formation of phenols salts – phenolates, which precipitate out together with petroleum acids. To segregate phenols this
mixture is treated with 5-6 % solution of sodium bicarbonate. Thus, petroleum acids
are converted into salts and dissolved in aqueous bed and phenols are extracted with
ether from a reaction mixture.
Technical phenols isolated of oil and oil fractions are employed as herbicides,
fungicides and sanitizing drugs.
2.6.1.3. Ketones and ethers
Compounds which contain carbonyl group С=О connected with two alkyl or
aryl groups (the same or different) are called as ketones.
The general formula of ketones is R–CO–R1
Nomenclature. Names of ketones are formed from names of initial hydrocarbons and the ending “-one”.
O
O
fluorenone
cyclohexanone
Number of the carbonyl carbon atom in aliphatic ketones should be the least:
O
CH3 C
CH2 CH2 CH3
pentanone-2
149
Ketones also can be named by enumeration both of hydrocarbon groups in order of the increase of complexity after that a word “-ketone” is added:
O
CH3 CH2 C CH3
C2H5
O
methylethylketone
(butanone-2)
C
ethylphenylketone
Some ketones have trivial names:
O
O
CH3 C CH3
acetone
(propanone or
diethylketone)
CH3 C
acetophenone
(methylphenylketone)
Physical properties. Acetone and next horologes are fluent liquids and highest
ketones are solid compounds. Boiling points of ketones are higher than that of hydrocarbons with similar molecular mass because of the dipole-dipole interaction between
their molecules.
Ketones with a small molecular mass dissolve in water. The increase of molecular mass leads to the decrease of solubility of these compounds. All ketones are
good soluble in organic solvents.
Ketones of oil. Ketones are present in oils in the trace amount. Different methylketones – from acetone to methylbutylketone - are found in gaseous condensates.
Cycloalkylketones and alkyldisubstituted fluorenones are detected in oils.
Ethers. A paltry amounts of ethers R–O–R1 and esters:
R C
O
1
O R
are detected in oils too.
The question on their structure and content in oils is a little investigated. The
ground mass of ethers and esters is concentrated in fractions that are distilled above
370 °С.
A large amount of oxygen (in composition of heterocyclic compounds) is
present in tarry matters.
2.6.2. Sulphur compounds
Oils contain both inorganic and organic compounds of sulphur: elementary
sulphur, hydrogen sulphide, thiols, sulphides, di- and polysulphides, thiophenes. The
main part of them belongs to sulphides and thiophenes.
150
Beside that sulphur-oxygen compounds – sulphones and sulphoxides - exist.
Nowdays more than 250 sulphur-containing compounds are revealed in oils.
Elementary sulphur is contained in oils in a dissolved state. Its amount can
change from 0.0001 up to 0.1 % (mass.) and, as a rule, is proportional to the content
of sulphur in oil.
Elementary sulphur is contained only in oils from calcareous and sulphatedolomitic depositions. Elementary sulphur agglomerates in the sludge at the bottom
of oil storage tank during the storage of such oils.
Heating of oil (during distillation) leads to the reaction of sulphur with hydrocarbons:
2RH S
R
S
R
H2
Sulphur gets into distillates from starting oil and also is formed there after
thermal decomposition of sulphurorganic compounds.
Hydrogen sulphide in layers is contained both in gases and in the dissolved
state in oils. Quantity of hydrogen sulphide dissolved in oils can reach 0.02 % of
masses. Hydrogen sulphide is formed as the result of the decomposition of unstable
sulphurorganic compounds at the heating of oil during its processing. Another way of
formation of H2S is reaction of hydrocarbons with elementary sulphur.
2.6.2.1. Thiols
Thiols are sulphurous analogues of alcohols and phenols – hydroxyl derivatives
of hydrocarbons. They contain thiol (mercapto) group –SН. The general formula of
thiols is R–SH.
Nomenclature. If R is alkyl or cycloalkyl group thiols are named thioalcohols
and if R is aryl group these compound are called as benzenethiols. According to the
regular nomenclature names of thioalcohols are formed from names of corresponding
hydrocarbons with the ending “-thiol”. Besides that the old nomenclature is often
used: a word “mercaptan” is added to the name of alkyl- or aryl- group.
Benzenethiols are named also arenothiols, thiophenols or mercaptоarenes. Before the name of the corresponding phenol a prefix “-thio” is often added:
CH3 CH2 SH
ethanethiol
(ethyl mercaptan)
SH
cyclohexanethiol
(cyclohexylmercaptan)
SH
benzenethiol
(phenylmercaptan, thiophenol)
Physical properties. Lowest thiols are easy volatile liquids with strong unpleasant odour which can be detected at a million times dilution. Therefore they are
added to the natural gas as odorant for the detection of its outflow in gas conduits.
151
Mercaptans are poorly soluble in water and good soluble in hydrocarbons and organic
solvents. They boil at lower temperature than that of corresponding alcohols. It can
be explained as a result of a smaller association of their molecules because sulphur
atom is less electronegative than oxygen and, consequently, less able to the formation
of hydrogen bonds.
Chemical properties. Thiols have weak acid properties; therefore they easily
interreact with alkalis with the formation of salts – mercaptides:
R
SH
NaOH
RSNa
H2O
This reaction is reversible and proceeds easily with lowest mercaptans only.
The use of this reaction for the extraction of mercaptans from oil fractions in industry
do not lead to the complete isolation of them because mercaptides of high molecular
weight are easily hydrolyzed by water. The increase of the molecular mass of mercaptans leads to the increase of hydrolytic lability of mercaptides, so it becomes more
difficult to evolve them with the help of alkali. Mercaptans easily form salts with
metals and their oxides (especially, with heavy metals); it leads to the corrosion of
metals:
RSH
CuO
(RS)2Cu
H2O
Resulting mercaptides are bad soluble in petroleum derivatives and form deposits which clog filters of engines and other mechanisms.
Rather weak oxidizing agents (oxygen of air) oxidize mercaptans into disulphides:
2R
SH
0,5 O2
R
S
S
R H2O
This reaction (in the presence of catalysts) is used to improve quality of benzines.
Strong oxidizing agents (HNO3, H2O2, etc.) oxidize mercaptans into sulphoacids:
R
SH
HNO3
R SO 3H
sulphoacid
Heating leads to the break of С–S bond and mercaptans turn into hydrocarbons:
R
SH
300-400°
the catalyst
R H H2S
Thiols (mercaptans) of oil. Methylmercaptan (b.p. 5.0 °С) and ethanethiol
(b.p. 37 °С) can be contained in natural and associated gases together with hydrogen
sulphide. Mercaptans are contained mainly in petrol and kerosene fractions.
152
The concentration of mercaptans in different oils changes from 0 to 75 % relatively to all sulphur compounds of oils.
More than 50 mercaptans from C1 to C8: alkyl, cycloalkyl and aryl mercaptans
- have been selected from different oils.
2.6.2.2. Sulphides
Sulphides are sulphurous analogues of ethers. The general formula of sulphides
is R–S–R1.
Nomenclature. According to the regular nomenclature names of sulphides are
formed from names of alkyl groups with the ending “-sulphide”.
CH3 S CH3
CH3 S C2H5
CH3 S
dimethylsulphide
methylethylsulphide
S
methylcyclopentansulphide
diphenylsulphide
Cyclic sulphides are named adding a prefix “thiа-“ to the name of the cyclic
hydrocarbon. Trivial names are also used.
S
thiacyclopentane
(thiophane)
S
thiacyclohexane
(thiopirane)
S
thiaindan
S
thiophene
S
thiahydrindane
Physical properties. Sulphides are liquids with unpleasant odour; their boiling
points are a little higher than that of thiols with the same molecular mass. These
compounds are poorly soluble in water and rather good soluble in sulphuric acid and
organic solvents.
Chemical properties of sulphides. Sulphides form complexes with different
electrophilic compounds that are insoluble in hydrocarbons: halogenides of metals
(AlBr3, SnCl4, TiCl2), fluorine hydride, boron fluoride (BF3), sulphur dioxide, etc.,
due to two lone electron pairs at sulphur atom. This is a base for methods of isolation
of these compounds from oil fractions.
Sulphides can be oxidized by strong oxidizing agents with the formation of
sulphoxides or – depending on conditions - sulphones.
C2H5 S
C2H5
H2O2
C2H5
C2H5
C2H5
S
O
diethylsulfoxide
S
O
O
C2H5
diethylsulphone
Beside that sulphides decompose under heating with the formation of hydrogen
sulphide, mercaptans and alkenes:
153
C3H7
S
C 3H7
C3H7SH
C 3H7
S
C3H7
H2S
C 3H6
2 C3H6
The growth of molecular mass of sulphides leads to the decrease of their thermal stability.
Thiophenes have the highest thermal stability of all sulphur compounds. Chemical properties of thiophenes are closed to arenes.
Sulphides of oil. More than 40 sulphides (mainly alkyl sulphides) are found in
oils. Beside that slight amount of alkylcycloalkyl, alkylphenyl and diphenyl sulphides
together with alkyl derivatives of thiopyran is detected.
The concentration of alkyl, cycloalkyl and aryl sulphides is 50-70 % and alkyl
thiophenes - 40-50 % (mass.) relatively to the sum of sulphur compounds in light and
middle fractions of oils.
Polycyclic sulphides are contained in kerosene and lube cuts:
S
S
S
S
Some oils contain cyclic sulphides consisting of thiаcyclopentane that is condensed with a benzene ring: thiaindan, dialkyl thiaindanes.
The large amounts of thiophene and its derivatives are also contained in middle
and higher-boiling fractions of oil and especially in products of its thermal
processing. There are for example alkyl substituted thiophenes. Aryl derivatives of
thiophane and thiophene together with sulphur derivatives of hybrid hydrocarbons are
widespread in high-boiling fractions.
S
S
benzothiophene
S
dibenzothiophene
naphthothiophene
S
tetrahydrobenzothiophene
2.6.2.3. Disulphides
Disulphides are compounds with general formula R–S–S–R1. Their names are
formed analogously to sulphides.
For example:
154
C2H5
S
S
C2H5
S
S
CH3
diethyldisulphide
methylcyclohexyldisulphide
Disulphides are heavy liquids with unpleasant odour; they almost insoluble in
water but rather good soluble in organic solvents.
Disulphides are present in oils in small amounts.
It is assumed, that disulphides are absent in crude oils but they are formed from
mercaptans as a result of oxidation by oxygen of air after the process of oil production.
The disuphides content is increased with a raise of molecular mass and boiling
point of oil fractions, but up to the fixed limit because these compounds are thermally
unstable.
Chemical properties of disulphides are similar to that of sulphides. At heating
they decompose with the formation of mercaptans, sulphides and hydrogen sulphide.
Disulphides are easily reduced into mercaptans; this reaction is used for their detection in the presence of other sulphur organic compounds:
R
S
S
R
H2
Zn
CH3COOH
2RSH
2.6.2.4. Sulphur compounds of oils
The sulphur content of oils can be changed from the tenth shares up to several
percents in dependence on the nature of oils.
The different classes of sulphur compounds that are present in some oils are
shown in tab. 11.
There is a various distribution of sulphur compounds on oil fractions. The concentration of sulphur compounds is increased with the raise of boiling points of fractions.
The main part of them (70-90 % of mass.) is concentrated in a heavy petroleum
residue (mazut and tar) and especially in a asphalt-pitchy part.
The distribution of sulphur compounds on oil fractions depends on the oil type
(tab. 12).
The concentration of sulphur compounds in oil fractions can be approximately
calculated by A.K.Karimov's empirical formula:
r
aM
32
r – the concentration of sulphur compounds in the fraction given, mass. %;
a – the concentration of sulphur in the fraction given, mass. %;
M – molecular mass of fraction.
155
In tab. 13, for example, group composition of sulphur compounds of two oils
with the common concentration of sulphur: about 1 % (Oil A) and about 5 % (Oil B)
- is given.
2.6.2.5. Origin of sulphur compounds of oil
There are different suppositions about origin of sulphur compounds contained
in oils.
Most probably that sulphur compounds were formed in natural oils as a result
of redox processes that took place between sulphates and hydrocarbons during the
geologic time.
Process of sulphuration of natural organic matters including sulphuration of
oils consists of several stages. The first is oxidation of hydrocarbons and other organic compounds by sulphates of metals (from underground waters) with the formation
of sulphides and hydrosulphides:
C nHm
M eSO 4
M eS
CO2
H2O
Sulphides and hydrosulphides then decompose into hydrogen sulphide:
MeHS CO2 H2O = MeHCO3 H2S
MeS CO 2 H2O = MeCO 3
H2S
Further saturated hydrocarbons react with hydrogen sulphide and form lower
homologues of hydrocarbons together with free sulphur:
C2H6
H2S = 2 CH4 S
Free sulphur can be also formed as a result of oxidation of hydrogen sulphide
by oxides of metals from depositions or by sulphates dissolved in waters:
2 Fe(OH)3 3 H2S = 2 FeS S 6 H2O
CaSO 4 3 H2S 2 CO2 = Ca(HCO3)2 4 S 2 H2O
Then processes of sulphuration itself, i.e. reactions between sulphur and hydrocarbons or other organic compounds included in oils with the formation of sulphur
containing organic molecules take place.
Some researches assume that the part of sulphur compounds is inherited from
initial organic matter, in particular, from proteins.
2.6.2.6. Effect of sulphur compounds on properties of petroleum derivatives.
Application of sulphur compounds
156
The sulphur compounds that are present in oils hinder its processing because of
the corrosion of instrumentation and poisoning of catalysts.
The increase of the sulphur compounds content in combustibles increases a
fuel rate and promotes a corrosive wear of the engine. Sulphur oxide that is formed at
combustion of fuels pollutes the atmosphere and causes a grate harm to the environment. Therefore, clearing of petroleum derivatives from sulphur compounds are
widely used now.
At the same time sulphur compounds are valuable raw materials for the organic
synthesis, therefore their separation from oil fractions is developed.
Mercaptans are used for rate control of polymerization of rubbers and as components to prevent oxidation of polymers and combustibles.
Sulphides are used for the synthesis of dyes and biologically active substances.
Products of sulphides oxidation: sulphoxides, sulphones and sulphoacids - find employement as dissolvents and extragents of metals, (such as gold, platinum, silver,
etc.). Sulphides and sulphoxides are good corrosion inhibitors of metals; they are flotation agents, surfactants, plastifiers, insecticides, herbicides and fungicides.
Thiophenes are used for the synthesis of oils and fuels additives, synthesis of
growth-promoting agents of plants and polymeric materials.
2.6.3. Nitrogen compounds
The nitrogen content of oils does not exceed 0.3 % and the maximal concentration of nitrogen compounds in high pitchy oils is 10 %.
The nitrogen content of oils mainly depends on the geographical location of
deposits and, to a lesser degree, on the geologic formation. Oils with the greatest concentration of nitrogen compounds are mined from tertiary depositions.
Nitrogen compounds are absent or are detected in trace amount in light distillates of oil. The increase of boiling points of fractions leads to the increase of nitrogen compounds content and, as a rule, more than a half of nitrogen compounds is
concentrated in a gum-asphalt part.
The nitrogen compounds, named as amines and amides of acids are detected in
oils.
2.6.3.1. Amines
Amines are derivatives of ammonia in which one, two or all three atoms of hydrogen are substituted for organic groups. Depending on this factor they are subdivided into primary, secondary and tertiary amines:
R NH2
primary
R
NH
R1
secondary
R
1
R
11
N R
tertiary
157
Depending on the organic group, jointed to the nitrogen atom, these compounds are subdivided into alkyl, aryl and heterocyclic amines.
Nomenclature. Alkylamines are named, adding the ending “-amine” to the
name of the alkyl group, connected with nitrogen atom:
CH3
NH2
CH3
methylamine
NH CH3
CH3
N
CH3
C2H5
CH3
trimethylamine
dimethylamine
N
C2H5
CH3
diethylmethylamine
Arylamines and amines with two, three and a more number of amino groups
are considered as aminoderivatives of hydrocarbons. Many arylamines have trivial
names:
NH2
NH2
CH2
NH2
CH3
CH2 NH2
1,2-diaminoethane
(ethylene diamine)
a-naphthylamine
aminobenzol
(aniline)
NH2
2-aminotoluene
(o-toluidine)
Heterocyclic amines usually have trivial names too:
N
N
H
pyrrolidine
H
pyrrole
N H
indole
N
N
H
piperidine
pyridine
N
quinoline
N
N
N
H
carbazole
acridine
isoquinoline
Physical properties. Primary and secondary amines are polar compounds and
can form hydrogen bonds with water. Therefore, low molecular weight amines are
good soluble in water.
The lowest alkylamines are gases and the highest – liquids or solid matters,
which are easily oxidized by oxygen of air and become dark. They are toxic and have
unpleasant odour. Physical properties of some amines are presented in tab. 14.
Chemical properties. Nitrogen of amino group has a lone electron pair; therefore amines have basic properties.
Amines react with acids adding a proton to the lone pair of electrons of nitrogen atom with the formation of salts analogous to ammonium salts:
158
R-NH2 + HCl → [R-NH3]+Cl-
Addition of a proton also takes place in water solutions:
+
-
[ R NH3] OH
R NH2 HOH
Basic properties of arylamines are considerably weaker than that of alkylamines.
Pyridine and related compounds have more weak basic properties in comparison with aliphatic amines but also add a proton:
HCl
N
N
Cl
H
hydrochloride of pyridine
pyridine
On the other hand, derivatives of pirrol decompose in acid medium:
polymer
N
H
pyrrole
As it has been mentioned above, reaction with acids leads to the corresponding
salts of ammonium. It is possible to obtain starting amines again from these salts in
case of treating them with strong alkali, for example, with caustic soda. These reactions are applied to the extraction of basic amines from oil and petroleum derivatives
because amines in contrast to other compounds of oil are soluble in weak acids and
can be recovered at alkalization.
Nitrous acid reacts with primary and secondary amines but it does not react
with tertiary alkylamines in the cold. Reaction with primary alkylamines results in the
liberation of nitrogen and formation of alcohols, alkenes and other substances.
R NH2 HO N O
N2
R OH
H2O
Chemical properties of nitrogen aromatic heterocyclic compounds are close to
arenes. So, hydrogenation of pyridine results in formation of piperidine:
159
H2
N
catalyst
N
H
piperidine
pyridine
Amines in oil. Amines of the basic and neutral nature exist in oil and petroleum derivatives. Basic are compounds that may be extracted by acid solution. The
concentration of nitrogen bases achieves 50 % of the sum of all compounds of nitrogen. The increase of fractional boiling points leads to the decrease of the concentration of nitrogen bases. The main part of nitrogen bases is concentrated in kerosene,
diesel and gas-oil fractions. Basic amines are represented predominantly by derivatives of tertiary amines: pyridine, quinoline, isoquinoline and - to a lesser degree – by
acridine.
Aryl amines: methyl anilines and xylidines – are also present in oils.
Alkylamines are not detected in oils. There are compounds, that contain two nitrogen atoms in some oils (derivatives of indole and carbazol quinolines). There are
also compounds, that contain nitrogen and sulfur heteroatoms in one molecule:
N
N
S
benzothiazole
S
thiazole
Alkylderivatives of pyrrole, indole and dibenzopyrrole refer to amines of neutral character. Highest fractions of oil contain porphyrins; their molecules consist of
four pyrrole rings. They are both in a free state and as complexes with metals, mainly
with vanadium and nickel.
The large amounts of porphyrins are typical of sulphurous oils. The porphyrins
content of some oils attains 0.1 %, but usually it is much less.
2.6.3.2. Amides of acids
Amides are compounds that contain amino group instead of OH in carboxylic
radical.
Names of amides are derived from names of appropriate acids with the change
ending “-oic” for “-amide”.
O
CH3
CH2
CH2
butanamide
C
NH2
160
All amides of acids are colorless crystalline compounds (with the exception of
fluid methanamide – formamide). Lower homologues are soluble in water. They are
associated because of the presence of intermolecular hydrogen bonds and consequently have rather high melting and boiling points.
Chemical properties. In contrast to amines amides have very poor basic properties. It can be explained by the conjugation of carbonyl group with a lone pair of
nitrogen electrons; it is so-called as mesomeric effect that leads to the decrease of the
electron density on nitrogen atom:
R C
O
NH2
Therefore, amides react only with very strong acids with the formation of unstable salts:
O
CH3
O
C NH2
[CH3
]
-
C NH2 Cl
chloride acetamide
HCl
acetamide
At the same time amides are weak acids:
2R C
O
HgO
NH2
(R C
O
)2 Hg
NH
H2O
Amides are slowly hydrolyzed by water. But this reaction is accelerated by the
presence of acids or bases:
R C
O
NH2
H2O
OH
NH3
R CH2
NH2
R C
O
Amides can be reduced into amines:
R C
O
NH2
H2O
4H+
catalyst
At treatment of amides with nitrous acid the liberation of nitrogen and formation of carboxylic acid takes place:
R C
O
NH2
HO NO
R COOH N 2
H2O
161
Dehydration of amides leads to nitriles:
O
CH3
C
NH2
P2O5
CH3
C N
H2O
Acetonitrile has the greate significance as a valuable dissolvent and monomer
in the synthesis of polymers.
Amides of acids in oil. Amides of acids belong to neutral nitrogen compounds
of oil. They form the main part of this group. The structure of amides and their content of oil are investigated insufficiently. But it is established, that the main part of
them is tertiary amides.
2.6.3.3. Origin of nitrogen compounds of oils. Effect
on properties of petroleum derivatives and application
It is considered that the main part of nitrogen compounds is inherited from animal and vegetative substances that compose a starting material of oil.
Possible sources of pyrrole, indoles and, probably, pyridine derivatives are proteins and pigments (from chlorophyll, etc.).
The mechanism of metamorphosis of mother substance into nitrogen compounds is not yet established. It is assumed, that anaerobic fermentation of proteins
results in formation of amides and other derivatives of amino acids and compounds
containing pyrrole rings. In the presence of air the further transformation into ammonia takes place.
The proof of the organic origin of oil is based on the presence of porphyrins
which have the same structure as a hemin (a colourant of blood) and chlorophyll.
Porphyrin complexes of oil are optically active and can accelerate redox reactions
therefore it is assumed, that they take an active part in genesis of oil.
Nitrogen compounds can form products of gumming and sealing, that leads to
worse service properties of reactive and diesel fuels. They also render a negative effect on catalysts during oil processing.
Nowadays, only a slight part of nitrogen compounds isolated from oil finds use
as corrosion inhibitors for the protection of the drilling and oil-field equipment, anticorrosive additives to dopes and fuels and also as a constituent of insecticides.
But these extremely important compounds in oils are not used as a chemical
raw material because of the absent of satisfactory methods of their separation into
fractions with close composition and properties.
The highest amines (С12–С20) are corrosion inhibitors of metals. Quaternary
salts of such amines are used as the cation-active surfactants in oil production. The
highest aliphatic amines find application in varnish-and-paint and rubber industry.
Ethylene diamine, Н2NСН2СН2NН2, is used in production of surfactants.
162
Hexamethylene diamine, Н2N(СН2)6NН2, is used for the synthesis of fibers and
for the removal of gypsum-hydrocarbon depositions in oil wells.
Anilines are employed in production of dyes, drugs, cellular plastics and synthetic resins.
Pyridine is used in the production of synthetic rubbers and plastics and as dissolvent.
Quinolines, acridines, pyrrole and dibenzo-pyrrole are used in the synthesis of
drugs, dyes and plastics.
2.6.4. Gum-asphalt materials
Gum-asphalt materials are the complex mixture of the most high molecular
weight ingredients of oil; their content attains 10-50 % of mass. In a high concentrated form gum-asphalt materials exist in the nature as native bitumens. Gum-asphalt
materials are heterorganic compounds of the hybrid structure, that include atoms of
nitrogen, sulphur, oxygen and some metals (Fe, Mg, V, Ni, etc.). Hydrocarbon part of
gum-asphalt materials is 80-95 % of molecular weight. Young oils of the aromatic
nature are the most affluent in gum-asphalt materials. More aged oils contain much
less gum-asphalt materials.
Gum-asphalt materials of oil can be divided into groups according to their solubility in different dissolvents.
Gum-asphalt materials combine two large groups of high-molecular compounds of oil – resins and asphaltenes with common chemical composition, structure
and properties. The ratio between resins and asphaltenes in oils and heavy residue
(where they are concentrated) is from 9:1 to 7:1. конец
Resins. Composition and properties of petroleum tars depend on the chemical
nature of oil. Despite of various natures of oils of different deposits, carbon and hydrogen content of resins changes in rather narrow limits (in % of mass): C – from 79
up to 87, Н – from 9 up to 11. But heteroatoms content more strongly depends on the
oil nature: oxygen - from 1 up to 7 % of mass., sulphur – from the tenth shares of
percent up to 7-10 %. Some resins contain nitrogen (up to 2 %).
Resins include from 70 up to 90 % of all heterorganic compounds of oil. They
also contain 1-2% more hydrogen in comparison with asphaltenes. The main part of
resins is neutral compounds. Acid products are represented mainly by asphaltenic acids.
Alkane oils (paraffinic oils) are characterized by high content (46 %) of neutral
gum substances.
Basic structural elements that are included in molecules of petroleum tars are
condensed cyclic systems: aromatic, cycloalkane and heterocyclic rings. According to
Sergienko S.R., the structure of resins molecules can be represented by following
formulas:
163
R
R
OR
R
(CH2)n
S
R
R
(CH2)n
S
RO
(CH2)n
(CH2)n
R
R
R
R
R
RO
n=4, R=C5H11
S
(CH2)n
R
R
(CH2)n
(CH2)n CH3
R
(CH2)n S
(CH2)n
R
O
R
R
R
Resins are very viscous sluggish liquids; sometimes they are solid amorphous
substances of dark-brown or brown colour. They have a density near 1.1 g / ml; their
molecular mass changes from 600 to 1000.
Tarry compounds are thermally and chemically unstable, can easily oxidize
and condense into asphaltenes.
Resins are easily sulphurized and dissolve in sulphuric acid. This is the base of
sulphuric-acid clearing of fuels and oils. Tarry substances form complexes with chlorides of metals and phosphoric acid.
Asphaltenes are more high-molecular compounds than resins. They differ
from resins not only in a smaller hydrogen content, but also a higher concentration of
heteroatoms. It is assumed that asphaltenes are condensation products of resins.
On the base of investigations of asphaltenes chemical structure it is considered
that they are polycyclic aromatic condensed systems with short aliphatic substituents
at aromatic rings. Five and six-membered heterocycles are also present in their molecules. The quantitative relationship of aromatic, naphthenic and heterocyclic structural elements oscillates in a wide range in dependence on the nature of oils.
The following types of polycyclic frames – links of molecules of resins and asphaltenes are offered:
164
1
CH3
11
R
R
111
R
R
CH3
S
1111
R
S
O
Asphaltenic oxygen is present not only in heterocycles, but also in different
functional groups: hydroxyl, carbonyl, carboxylic and ethereal.
Sulphur is also included into sulphidic bridges between fragments of asphaltenic molecules. Ring compounds containing sulphoxide group are also detected.
Atoms of nitrogen are present in pyridine and pyrrole rings, and the last are
more often found in porphyrin complexes of vanadium and nickel.
Asphaltenes are solid amorphous substances with the density more than 1.14
and molecular mass 2000 - 4000.
Asphaltenes, isolated from crude oils well dissolve in carbon disulphide, chloroform, benzene, cyclohexane and other organic solvents but do not dissolve in the
lowest alkane hydrocarbons. This is the base for the extraction of asphaltenes from
oil and its derivatives.
Asphaltenes become soft at heating but do not melt; after 300 °С they pass into
coke and gas.
Polar centers in a molecule (owing to the presence of heteroatoms and conjugated electronic systems of aromatic fragments) lead to the self association of asphaltenes even in diluted solutions and also in oils. At high concentrations they form colloid system that defines the viscosity of oils.
Asphaltenes are chemical active compounds. They easily undergo oxidation,
sulphonation, halogenation, nitration and with some difficultly – hydrogenation. Asphaltenes also may form complexes with chlorides of metals and phosphoric acid.
In dependence on solubility asphaltenes of petroleum residues (products of
thermal petroleum refining) are divided into two subgroups of compounds – carbenes
and carboids. Carbenes are insoluble in any hydrocarbons and partly soluble only in
pyridine and carbon disulphide; carboids do not dissolve practically in anything.
These compounds are absent in crude oils, they are formed as secondary products of high-temperature petroleum refining in the presence of air oxygen.
It is necessary to say, that self-contained solid pitchy black materials – asphalts
- exist in the nature. Usually they lie near oil deposits. It is assumed, that these substances are formed at evaporation and simultaneous oxidation of oil in places of its
outflow on the surface. They contain high molecular weight hydrocarbons, resins and
asphaltenes.
The gum-asphalt materials, found in oil have a different origin. The part of
them has probably relict character. Other part consists of oxidized and sulphurized
hydrocarbons of high molecular weight or of products of abiogenous transformation
of some unstable heteroatomic compounds and polycyclic hydrocarbons.
165
Presence of pitchy-asphalt materials in combustibles and lubricating oils is undesirable. They worsen colour, increase a carbonization and depress lubricant ability
of oils. Pitchy-asphalt materials poison catalysts and lead to the coking of equipments
during petroleum refining. At the same time pitchy-asphalt materials, as a part of
some natural asphalts and residues of the vacuum distillation of oils and bitumens,
give them valuable technical properties for use in the national economy.
Now bitumen consumption is tens million tons a year. Mostly they are used as
a part of rigid pavements, as a connecting, sealing and hydraulic insulating material
for building roofs, bases of buildings and hydraulic constructions. They serve for
electro insulation of cables, accumulators, as a part of some rubbers and varnishes.
Another important field of bitumens application is connected with surface coats
of buried pipelines for their corrosion protection. The efficiency of this method is defined not only by high waterproofing properties of bitumen coats but also by their
good electrical isolating properties that considerably diminish the bad effect of vagabonding currents. The most important is a corrosion protection of oil and gas main
pipelines.
Bitumen can be a part of flushing fluid used at drilling. Quality of bitumens
depends on the content of various gum-asphalt materials. Asphaltenes increase hardness of bitumens, rise their softening point; neutral resins give elasticity and rise
hardness.
2.6.5. Mineral components
Salts and complex organic compounds of metals belong to mineral components
of oil. Oil contains up to 0.03 mass % of these substances. Some metals get into oil at
its taking and transportation. Alkaline and earth metals (Na, K, Ba, Sr, Mg) together
with polyvalent metals (d-elements: V, Zn, Ni, Fe, Mo, Co, W, Cr, Cu, Mn, Pb, Ga,
Ag, Ti) and p-elements, such as Al, etc. are detected in oils.
Determination of composition and concentration of these elements is carried
out mainly with spectral analysis of the ash obtained at combustion of oil.
In contrast to other elements oil contains a comparatively large amount of vanadium and nickel as metalporphyrine complexes.
High-sulphur crude oils contain 2·10-2 mass % of vanadium and 1·10-2 % of
nickel; the concentration of other metals is much less.
Analysis of trace elements of oil is of the greate interest in connection with a
problem of the origin of oil. The presence of many elements in oil that are typical of
plants and animals is the evidence of their relationship.
Metals in oil hinder its processing. Many metals, first of all, vanadium and
nickel, reduce the activity of catalysts and accelerate the process of coke deposition
in furnaces. Vanadium oxide (V) which is formed during the combustion of oils promotes the corrosion of equipment.
The presence of trace elements in refinery cokes pollutes metals of electrothermal productions (aluminium, iron, etc.). Organometallic complexes are adsorbed
166
on the oil-water interface due to their surface-active properties and promote the formation of emulsions.
Organometallic compounds. Organometallic compounds of V, Ni, Cu, Zn
and other metals contained in oils, are mainly concentrated in the tar; however, some
part of them (up to 0.01 %) is volatile and passes into oil distillates.
The main part of metals is contained in resins and asphaltenes. The other significant part of metals is present in oils as metalporphyrine complexes. The metalloorganic compounds content of oils is connected with the high concentration of heteroorganic compounds, resins and asphaltenes and is considerably – in 2-3 times
higher, than that of low-sulfur oils with the low asphalt-tarry matters content.
Chapter 3
PETROLEUM REFINING AND PROCESSING
OF PETROLEUM GASES
—————————————————————————————————
3.1. PETROLEUM REFINING
3.1.1. Preparation of oil to processing
So-called crude oil that is mined on oil fields contains associated gases (50-100
m / t), stratal water (200-300 kg / t), inorganic salts (10-15 kg / t) and mechanical
impurities.
Before processing of oil it is necessary to delete water, gas and impurities of
solids. Otherwise solid impurities will spoil equipments and reduce quality of petroleum derivatives; on the other hand, associated gases and fugacious fluid hydrocarbons - valuable products - will be evaporated and lost during the storage of oil.
Therefore one of the problems of oil preparation is isolation and collection of gas and
fugacious ingredients.
Liberation of associated gases is carried out in gas traps by the decrease of solubility of gases owing to the decrease of pressure.
A part of light petrol fractions is entrained simultaneously with gases and then
directed for the further processing to gas-refining plants together with gases and a
condensate of gas condensate deposits. These plants carry out:
3
1) extraction of labile benzine including hydrocarbons from С3 and higher
from gases;
2) liquefaction of gas for pumping-over to its users;
3) separation of labile benzine into individual hydrocarbons: propane, isobutane, butane and stable benzine.
Gas-refining plants also contain equipments for drying and purifying of gases
from hydrogen sulphide.
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Oil that is minded on oil fields is also purified from the main part of water and
salts.
Water is the permanent, inevitable and undesirable ingredient which is getting
out together with oil from the hole.
The impurity of water disturbs a technological working process of equipments.
Besides that water contains dissolved salts: sodium, calcium and magnesium chlorides; these salts partially decompose during the distillation of oil with the formation
of hydrochloric acid that destroys equipments. That is why oils must be separated
from water.
But it is not easy to do because of the formation of emulsions as a result of stirring of oil with water during their motion in the hole. And these emulsions get out of
the hole instead of oil with water as two easily divided liquids. Two types of emulsions are possible: water is dissipated in oil as a numberless amount of smallest drops
(1), and oil is dissipated in water by the same way (2).
Formation of such emulsions can be explained by the presence of so called as
emulsifying agents or emulsifiers. Their sources are some impurities of oil: resins, asphaltenes, soaps of petroleum acids and other salts. Emulsifiers are concentrated into
films on surfaces of oil or water drops. The nature of emulsifying agents defines the
type of emulsion mentioned above.
Emulsions of oil are stable mixtures. They can not be separated even at long
storage in container. Besides that these emulsions also contain dispersed solid particles of rocks that do not precipitate. Therefore it is impossible to dispatch such
emulsion to the refining plant; previously it must be underwent the special
processing, so-called demulsification of oil.
Some methods of the oil demulsification (destruction of emulsive films on the
surface of oil or water drops) are known. One of them is a heating of oil emulsion.
However, in many cases emulsions are quite resistant and heating that was followed
by a tank bottoms does not result in desirable separation of oil and water.
Therefore special materials - so called as demalsifiers – together with heating
are widely used for demulsification of oil.
Different methods to destruct emulsions including thermochemical under pressure are used now. The better method of destruction is the electrical method founded
on the action of electrical field.
It is based on the desalting and dehydration of oil under the action of electrical
field and can be realized in apparatuses called as electrodehydrators.
The emulsion flows into such electrodehydrator and then passes between electrodes under high tension. Action of alternating voltage leads to the movement of
charged droplets. Continuous change in the direction of movement under the action
of the alternating electrical field results in the collision of droplets with one another
and with electrodes. As a result a merging of drops takes place. Water collects in the
bottom of the electrodehydrator and can be easily deleted.
Now electrodehydrators of a spherical form and a capacity of 500-600 m3 are
employed for demulsification.
Introduction of demalsifiers immediately into the crude oil from the hole pro-
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motes deeper desalting and leads to the decrease of the residual salts content (up to
5-7 mg / l). Usually, oil enters for desalting after thermochemical processing in settling tanks where the ground mass of stratal water is separated. It facilitates a work of
electrodehydrators. Oil is fed into electrodehydrators with the adding 3-7 % of washing water and about 0.05 % of alkali. Alkali is necessary for the formation of neutral
or alkali medium that accelerates the demulsification and depresses the corrosion of
equipments.
The technological diagram of the electrical desalting equipment that combines
thermochemical dehydration and electrical desalting equipment itself is shown on fig.
4.
Fig. 4 The technological diagram of electrical desalting equipment:
1 - a raw pump; 2 - a heat exchanger; 3 - a steam heater; 4 - thermal sedimentation tank; 5,6
- electrodehydrators; 7,8 - water pumps; 9 - proportioning pumps; 10 - mixing valves; 11 - a pressure controller
Lines: I - crude petroleum; II - a demalsifier; III - alkali; IV - fresh water;
V - desalinized oil; VI – a steam; VII - a sewerage water
First of all such treatment of oil is carried out previously on the oil field and finally on the petroleum refining plant. Besides that, the alkalization of oil (addition of
alkali or ammonia solutions to the crude oil) is carried out for the neutralization of
acidic and sulphureous impurities that cause the corrosion of equipment.
3.1.2. Initial oil distillation
The initial oil distillation is the first technological process of petroleum refining. Every refining plant has equipments for initial processing.
Reducing of crude oil is set up on the difference in boiling points of hydrocarbons that are close to each other in physical properties.
Distillation or distilling is a separation of a mixture of mutually soluble liquids
into fractions which differ in boiling points with each other and with starting mixture.
This mixture heats up to boiling with partially evaporation; as a result, distillate and
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residue which differ on composition from starting mixture are obtained. Modern
equipment carries out a crude oil distillation using a flash evaporation. During this
procedure low-boiling fractions remain in the apparatus after evaporation and reduce
a partial pressure of higher-boiling fractions that enables to realize distillation at lower temperatures.
Flash evaporation and consequent condensation of steams lead to two fractions:
light fraction that consists mainly of low-boiling ingredients and heavy fraction
which contains less low-boiling ingredients in comparison with a feed stock, i.e. distillation leads to the dressing of one phase with low-boiling, and other – with highboiling components. However, this way doesn’t give the required separation of oil
ingredients for obtaining of products that boil in definite temperature ranges. In this
connection the rectification of petroleum vapors takes place after flash evaporation.
Rectification is a diffusive separation of liquids with different boiling points by
the multiple countercurrent vapor-reflux contacting.
Modern equipments for initial processing combine both flash evaporation and
rectification.
Now the reducing of crude oil is carried out as a steady process in so called as
atmosphere-vacuum tubular equipments with a pipe-still heater and a rectification
column (fig. 5).
This process is based on the heating of oil up to 350 °С in a pipe-still heater;
after that oil enters into mid-range of the lower section of the atmospheric distillation
column. Petrol, kerosene and other fractions that boil at temperatures from 40 up to
300 °С turn into vapor because they are overheated relatively to the oil with 350 °С.
Vapors of these low-boiling fractions flow upwards in the column and higher-boiling
black oil (mazut) flows downwards. It results in the differences in temperatures on
the height of the column. The highest temperature is in the bottom of the column and
the lowest – in the upper part.
Fig. 5. The schema of the atmospheric-vacuum equipment for the crude distillation:
1,5 - pipe-still heaters; 2,6 - distillation columns; 3 - heat exchangers; 4 - condensers
170
Vapors of hydrocarbons that flow up are in contact with more cool liquid
which flows down; as a result these vapors are chilled and partly condensed. The liquid heats up and volatile fractions are evaporated from it. As a result the composition
of liquid and vapor is various because the liquid is enriched in non-volatile hydrocarbons and vapour - in volatile. Such process (condensation and evaporation owing to
the difference in temperature on the height of the column) leads to the separation of
hydrocarbon fractions on boiling points and on composition. Special separating devices – so called as plates - are placed inside a column to intensify the process of separation. Plates are perforated steel sheets with holes for a liquid and vapour. Some
constructions contain holes that are covered with bubble caps and overflow tubes for
a liquid (fig. 6).
3
2
4
5
1
steam
steam
steam
Fig. 6. The schema of the device and job of a distillation plate column:
1 - plates; 2 - fitting pipes; 3 - bubble caps; 4 - overflow beakers; 5 – walls
of a column
Vapours bubble through a liquid and intensively agitate it on such plate; as a
result a foamy blanket is formed. During this process higher-boiling hydrocarbons are
chilled and condense while low-boiling hydrocarbons dissolved in a liquid are heated
and passed into vapours. Vapours are lifted to a higher plate, and the liquid overflows
on a lower one. Processes of condensation and evaporation take place again on this
plate. Usually distillation columns have a height of 35-45 m and up to 40 plates. A
degree of separation is quite enough to condense and to take fractions in the strictly
fixed interval of temperatures. So, solar oil is taken at the temperature of 300-350 °С,
kerosene fraction - at 200-300 °С and naphtha fraction - at 160-200 °С. Vapours of
benzine fraction are passed through a top of a column without condensation at the
temperature of 180 °С where they are chilled and condensed in a special heat exchanger. The part of this fraction is reverted for the refluxing of the top plate of a
column. The aim of this operation is to separate volatile hydrocarbons more carefully
and to condense impurities of less fugitive hydrocarbons that flow downwards; it can
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be realized by the contact of hot steams with the refrigerated benzine fraction. Such
way leads to the more pure benzine with octane value from 50 up to 78.
More careful distillation of the benzine leads to three fractions: gasoline (petroleum ether) – 40-70 °С, actually benzine – 70-120 °С, and ligroin – 120-180 °С.
Mazut is collected in the bottom of the distillation column. It can serve as
burner oil or as a raw material for the obtaining of lubricating oils, engine fuel and
petroleum gases – in dependence on the sulphur compounds content of oil. Usually,
in case of more than 1 % of sulphur, mazut is used as high energy burner oil; the distillation is stopped and the process becomes a single-stage. In case of the obtaining of
lubricating oils the further distillation of mazut takes place in the second (vacuum)
distillation column. Such way is called as two-stage process. It differs from a singlestage process by smaller fuel consumption and by higher efficiency of equipments –
owing to the use of vacuum and the higher extent of heat utilization. Use of vacuum
at the second stage of distillation prevents the decomposition of heavy hydrocarbons,
reduces boiling point of mazut and diminishes fuel consumption for its heating.
The essence of the second stage comes to the heating of mazut by heated gases
up to 420 °С in a pipe-still heater and consequent distillation in a column. As a result,
about 30 % of tar and up to 70 % of the lubricated ingredients (raw materials for the
obtaining of lubricating oils) are formed. The approximate yield and temperature of
selection of lube cuts of mazut are given in tab. 15.
The oil heating up to 350 °С is carried out in two stages for the improvement
of the working regime of atmosphere-vacuum equipment and for the greater economy
of heat.
In the beginning oil is previously heated up to 170-175 °С by the heat of products of distillation (the last are appropriately chilled), and then – in a pipe-still heater
by heated gases. Such operation diminishes fuel consumption and the cost of
processing.
3.1.3. Chemical processes of petroleum refining
As a result of fractional distillation of oil it is possible to separate 5-25 % of
benzine and up to 20 % of kerosene. Rather small yield of these valuable products
causes the wide application of chemical, so called as destructive methods of petroleum refining (cracking distillation, pyrolysis, reforming), that lead to the destruction
of large molecules and, as a result, to the greate amount of light products with the
improved properties. The additional amount of benzine is obtained by the cracking:
decomposition of less necessary petroleum derivatives (mazut, gasoil, solar oil,
topped residuum, etc.) at heating up to 420-550 °С, more often in the presence of catalysts. It leads to the increase of the overall yield of benzine in several times: up to
40-50 % and even up to 70 %.
This process has been established for the first time by D.I. Mendeleyev and
A.A. Letni. In 1890 V.G. Shuhov developed the operation and construction of basic
apparatuses for cracking distillation under pressure. But the practical use of cracking
distillation was begun only in 1913 in USA and in the beginning of 30-th – in USSR.
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3.1.3.1. Thermal cracking, pyrolysis and coking
The simplest industrial method of the decomposition of heavy petroleum hydrocarbons into light substances is thermal cracking – the decomposition of large
molecules under heating and the formation of smaller molecules of hydrocarbons.
However, decomposition of molecules during cracking proceeds chaotically and cannot lead to hydrocarbons of the desired structure. Partially it may be achieved in the
presence of special catalysts, i.e. by a catalytic cracking. Further structural transformations of hydrocarbons obtained as a result of cracking is carried out during reforming.
Cracking is a complex chemical process because a raw material is a mixture of
hydrocarbons and they may convert into different substances.
However it is possible to understand some regularity in behavior of various
classes of hydrocarbons at high temperatures.
Alkanes at high temperatures mainly decompose with the cleavage of
carbon-carbon bonds. As a result of decomposition and simultaneous migration of
hydrogen atoms new molecules of alkanes and alkenes of lower molecular mass are
formed:
C16H34
hexadecane
C8H18
octane
C8H16
octene
Lowest alkanes also undergo dehydrogenation and disintegration with the bond
cleavage at the end of carbon chain.
Isoalkanes are thermally less stable than alkanes of the normal structure:
C 4H10
C4H8 H2
C4H10
C 3H6 CH4
Cracking of cycloalkanes leads to the following reactions:
1) dealkylation (elimination of alkyl side chains):
(CH)2
CH3
CH3 + CH2
CH2
2) cleavage of a ring with the formation of alkenes, dienes and alkanes:
C 2H4 + C4H8
2 C 3H6
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3) dehydrogenation of sixmembered naphthenes with the formation of arenes:
+
3 H2
Arenes with side hydrocarbon chains are dealkylated under cracking with the
formation of simple arenes and alkenes. For example, benzene and ethylene are
formed from ethylbenzene:
CH2
CH3
C2H4
Besides that, arenes condense predominantly with unsaturated hydrocarbons
that lead to the formation of hydrocarbons with rather large number of benzene rings
and the small hydrogen content; such mixture is called as coke.
Unsaturated hydrocarbons can be polymerized or eliminate small molecules
with the higher number of multiple bonds:
CH3
CH2 CH
butylene
CH2
CH2
CH CH
divinyl
CH2
H2
Besides that, they enter into alkylation, isomerization and cyclization reactions
(both with each other and with different hydrocarbons) with the formation of isohydrocarbons, naphthenes and arenes. The increase of temperature reduces the thermal
stability of hydrocarbons; it is more visibly for highest homologous of alkanes.
Hence, heating first of all leads to the decomposition of hydrocarbons with long
chains.
The rise in temperature moves the place of С–С bond split to the end of the
chain; as a result hydrocarbons with short chains up to methane are formed. However,
methane (at temperatures 820 °C and higher) also decomposes into carbon and hydrogen. Thus, the rise in temperature increases a yield of gaseous products. The rate
of thermal decomposition of hydrocarbons decreases in order: alkanes – cycloalkanes
– arenes. Hence, the increase in temperature promotes the accumulation of arenes in
products of cracking.
The rise in pressure shifts the equilibrium between gaseous products and starting liquid compounds in reactions of decomposition of hydrocarbons to the left.
Therefore, to increase the yield of liquid products the process must be carried out under raised pressure; on the other hand if it is desirable to obtain more gaseous products, the cracking is carried out under reduced pressure.
Thermal cracking is subdivided into liquid-phase (processing of last cuts and
residues of petroleum refining together with light cuts – ligroin, kerosene, gasoil at
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460-560 °С and the pressure of 2-7 МPа) and vapour-phase (processing of tar, bitumen and cracking residues at 550-600 °С and atmosphere pressure).
The technology of thermal cracking is carried out in two stages: the heating of
the raw material in pipe-still heaters to provide the sufficient rate of cracking (1) and
distillation of cracking products (2). As a result benzine, gases and a cracking residue
are obtained.
Among other chemical methods of petroleum refining thermal cracking now
has the lower significance than it was 20-25 years ago. Nevertheless, this process is
so far used for the refining of heavy petroleum residues. Thermal cracking of mazut,
for example, leads to the following products with average yields (%): cracked gasoline 30-35; cracked gases 10-15, cracked residue 50-55.
Thermal benzines have a higher knock value than that of some straight-run
benzines due to the presence of aromatic and branched hydrocarbons. Octane value of
such benzines is about 70. The presence of reactive unsaturated hydrocarbons in
cracked gasolines decreases their stability in comparison with straight-run gasolines.
Gases of thermal cracking form a mixture of saturated and unsaturated hydrocarbons: ethane, ethylene, propane, propylene, butanes, butylenes, pentanes, etc. –
and serve as a raw material for chemical synthesis. The cracking residue is used primarily as a burner oil.
Pyrolysis is used in case of obtaining not a benzine, but gases and liquid aromatic hydrocarbons as main products.
In contrast to the thermal cracking pyrolysis takes place in vapour-phase at the
atmospheric pressure, temperatures near 670-720 °С and results in the heavy decomposition and secondary reactions of hydrocarbons. As a result up to 50 % of gas,
aromatic hydrocarbons and resin from kerosene or light gasoil are obtained. Gases of
pyrolysis differ from cracking gases on the heightened ethylene, propylene, and butadiene content. Liquid products of pyrolysis are starting materials for the obtaining of
benzene, toluene, xylene, green oil (it is used for making carbon black), naphthalene
oil (from which naphthalene is separated) and pitch (the raw material for the production of coke). High-viscosity petroleum residues are utilized for coking.
Coking is the process of heavy decomposition of petroleum residues without
air at the atmospheric pressure and temperature of 450-500 °С. Coking of mazut, bitumen, tar, resin, cracking of residues and other waste products leads to the maximal
yield of light oils. High-viscosity residues are used for the production of electrodes,
gases, motor spirits, diesel and burner oils. However, the motor spirit has poor quality
and low antidetonant properties. For a raise of octane value of such benzine it is subjected to reforming.
3.1.3.2. Catalytic processes
A catalytic cracking is mostly used now. A catalytic cracking of petroleum derivatives (solar and kerosene fractions) is carried out in the presence of catalysts with
the obtaining of a high quality benzine with a high yield. The catalyst reduces the activation energy of cracking reactions therefore a rate of catalytic cracking is higher
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than that of thermal; this circumstance leads to the more mild conditions of the cracking (temperature of 450-520 °С, pressure of 0.1-0.2 МPа). Aluminosilicates with the
advanced surface serve as catalysts. Amorphous aluminosilicates were employed earlier, but now more active crystalline aluminosilicates (zeolites) with additions of rareearths elements are used. Decomposition of hydrocarbons follows the same way, as at
the thermal cracking.
Catalytic cracking leads not only to decomposition reactions but to other
processes: isomerization, dehydrogenation and hydrogenation. Alkanes are cracked
with the formation of lighter (saturated and unsaturated) hydrocarbons. Alkenes are
isomerized into hydrocarbons with branched chains and form cycles with a consequent hydrogenation that results in formation of arenes. Cycloalkanes also convert
into arenes by the same way.
Arenes with the long side chains will be dealkylated (elimination of side
groups) under conditions of cracking with the formation of benzene and unsaturated
hydrocarbons.
Condensation of arenes is accompanied with a coke deposition on the surface
of a catalyst that reduces its activity. It can be regenerated by the burning of the catalyst in the presence of air at 550-600 °С.
Reactivation of catalyst periodically alternates with cracking. Catalytic cracking with fluidized bed and with moving catalyst exist in industry. Cracking with
fluidized bed of catalyst is more important because of the high intensity of process
and ease of reactivation of the catalyst.
Benzine of catalytic cracking contains a large amount of arenes and isoalkanes
and therefore has a high octane value (78-80); together with ethyl fluid it equals 9095. Beside that this benzine is more stable because of the absence of unsaturated hydrocarbons. Gases of catalytic cracking have a yield of 12-15 % and consist of saturated and unsaturated hydrocarbons from С1 up to С5; they are used in industrial organic synthesis.
The high quality of light oils, high octane value of benzines and raise of their
stability can be achieved by using of the catalytic reforming.
The catalytic reforming is the original cracking that in contrast to catalytic
cracking is carried out under pressure of hydrogen and in the presence of other catalysts.
Use of hydrogen and catalysts decrease the rate of coke’s depositions on the
catalyst and considerably reduce the concentration of sulphur in benzine (in case of
sulphurous oils). Such effect is attained owing to the catalytic elimination of sulphur
followed by its hydrogenation and conversion into easily deleted hydrogen sulphide.
Diverse versions of catalytic reforming differ from each other in temperature,
pressure, catalysts and methods of their regenerations. The most widespread is socalled platforming: catalytic processing of easy oil fractions in the presence of platinum catalyst (platinum on alumina) and hydrogen at 500 °С. Usually low-octane
benzines of simple distillation or naphtha stock are used as light oil fractions in this
process.
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As a result of simultaneous reactions of decomposition, hydrogenation and
isomerization that take place during platforming it is possible to obtain (in dependence on pressure) high-octane gasoline or aromatic hydrocarbons (benzene, toluene,
xylene). For example, in case of pressure from 15 up to 30 atm, high-quality benzine
with octane value of 98 is formed. Such benzine is rather stable and has a small concentration of sulphur.
Irrespective of conditions a mixture of gases: methane, ethane, propane, butane
and isobutane (from 5 up to 15 %) - are obtained as products of catalytic reforming
together with liquid hydrocarbons. Some of these gases serve as a raw material for
the production of methanol, formaldehyde, divinyl, propylene and high-octane components to benzines.
3.2. PROCESSING OF PETROLEUM GASES
Gaseous hydrocarbons are widely used as a fuel and raw material for petrochemical processing. In case of their utilization as a fuel natural mixtures may be
used without separation. But petrochemical processing demands individual hydrocarbons or their narrow fractions.
Separation of gases into individual components or fractions for the further
processing is carried out by the following methods: compressor, absorptive, condensation – rectifying at low temperatures and adsorptive.
The compressor method is based on the pressure increase with the consequent
refrigeration resulting in condensation of higher-boiling gases; it is used rather rarely
now, mainly for the transportation of gas.
The absorptive method includes washing of gas under pressure and its refrigeration by fluid absorbent. Saturated absorbent enters into desorber with the consequent distillation of absorbed hydrocarbons. The condensed gases, mainly С3–С4, undergo further rectification.
The condensation-rectifying method (or a method of low-temperature rectification) includes simultaneous use of high pressure and low temperature for the liquefaction and rectification of gases.
The adsorptive method is based on the ability of some solid matters to absorb
selectively different components of gas.
The final stage of separation of gas mixtures is rectification. It is used for making individual hydrocarbons of high purity.
Separation of gas mixtures is carried out in complex gas-fractionation equipments.
Some of gases obtained are used as a raw material for polymerization, alkylation and isomerization.
Polymerization and alkylation of gases that were obtained as a result of cracking or pyrolysis lead to different kinds of high-quality benzines (polymer-benzine,
alkyl-benzine and pyro-benzene).
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Catalytic polymerization of butylene fraction with consequent hydrogenation
leads to the technical isooctane and alkylation of butane-butylene fraction – to alkylate. These products are high-octane components of engine fuels.
Some individual hydrocarbons can be used for the production of fuel without
any chemical processing. For example, pentane and normal butane after separation
from gas mixture are injected into benzine to raise their octane value and vaporability. Propane, butane and their mixture are employed as a fuel for gas-balloon engines
and household purposes.
Some oil products (condensed gas, С3 and С4-fractions, oil-refinery gases and
casing-head gas, paraffin, aromatic hydrocarbons, etc.) are transferred from refining
and natural-gasoline to chemical plants for the further processing. This branch of
chemical industry deals with organic synthesis that is based on products of petroleum
refining. These products are separated into individual hydrocarbons which are converted into different compounds by physicochemical or chemical methods.
Physicochemical methods are based on the action of high or low temperatures
and high or reduce pressure (with or without catalysts).
Chemical methods are set up on the actions of acids, alkalis, oxidizing agents,
halogens, hydrogen and other reagents that lead to nitration, sulphonation, oxidation,
halogenation, hydrogenation, hydrolysis, isomerization, polymerization, etc. These
methods of processing convert hydrocarbons of petroleum gases into valuable chemicals.
3.3. PURIFICATION AND STABILIZATION
OF PETROLEUM DERIVATIVES
3.3.1. Purification of petroleum derivatives
Purification of petroleum derivatives is a final stage in production of fuels and
lubricating oils. It is connected with the presence of alkenes, sulphurous, oxygen and
nitrogen-containing compounds in products of distillation and cracking, which cause
instability of their properties. There are chemical and physicochemical methods of
purification. Treating with sulphuric acid and hydrogen (hydrofining) are ascribed to
chemical methods and adsorption or absorption - to physicochemical ones.
3.3.2. Stabilization of petroleum derivatives
Some times purified liquid fuel and lubricating oils are unstable at storage owing to the slowly oxidation of unsaturated and easily polymerized hydrocarbons. Such
oxidative processes are accompanied by the formation of tarry matters and deposits
that increase the harmful action of petroleum derivatives on tare, pipelines and me-
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chanisms. To inhibit these reactions some antioxidants: phenols and arylamines – are
added to petroleum derivatives.
3.4. PRODUCTS OF PETROLEUM REFINING
Products of petroleum refining are a starting material for the further chemical
processing of diverse petroleum derivatives. They can be subdivided into following
groups:
1) fuel (benzines, kerosenes, diesel and fuel oils);
2) lubricating oils;
3) paraffins, ceresines;
4) pliant lubrications;
5) bitumens;
6) coke;
7) raw material for the petrochemical and basic organic synthesis;
8) other petroleum derivatives for different purpose.
Petroleum fuel is subdivided into motor or light oils used for the combustion in
engines and burner oils used in steam boilers and industrial furnaces.
Benzine is a carburetor fuel for engines of internal combustion. Benzine now is
one of the most important petroleum derivatives because it serves as a fuel for engines of motor vehicles and propeller airplanes.
The aircraft benzine is easier, has a density of 0.73-0.76 g / sm3 and b.p. of 40180 °С; automobile benzine is more heavy, has a density of 0.74-0.77 g / sm3 and b.p.
of 50-200 °С. The most important property of benzine as a fuel is its antiknock rating,
or antiknock value.
Antiknock value of carburetor fuel is characterized by octane value and determined on special equipments by the comparison of samples of tested fuel with a standard fuel. As a standard fuel mixtures of isooctane with high antiknock properties and
of normal heptane with a low antiknock activity are used. Antiknock value of isooctane is used as 100 and n-heptane – as a zero. Octane value corresponds to the percentage of isooctane in a standard mixture that detonates identically with the investigated sample of a fuel. Alkenes and arenes have the greatest antiknock value and
normal alkanes and cycloalkanes with linear side chains - the lowest one. Alkenes of
the normal structure have higher octane values than that of normal alkanes with the
same number of carbon atoms. Hence, octane value of benzine depends both on the
concentration of hydrocarbons mentioned above and their structures. Benzine of
straight distillation of naphthenic oils has octane values of 65-78, and that of parafinic oils – 40-60.
Antiknock value of benzine strongly rises (up to 10-20 octane units) in the
presence of a small amount of antidetonator dissolved in a fuel. Usually tetraethyl
lead – Pb(C2H5)4 - rather toxic agent, is used for these purposes. This agent is used as
a mixture with ethyl bromide and -naphthalene chloride (ethyl fluid); additives
mentioned above promote the removal of lead oxides by the conversion them into vo-
179
latile halogenides. Now tetraethyl lead has rather small application because of the bad
influence on the environment. More ecologically safe components are used now to
increase the octane value of benzines: methyl tert-butyl ether, molybdenic compositions, alkylates, etc.
Distillates obtained by crude distillation with b.p. of 150-250 °С (composite
propellant) or 150-280 °С (composite modified propellant) are used as liquid propellants.
Diesel oil has greate significance now because of the wide spread of Diesel engines. The product of distillation of parafinic oil - gas oil or its mixture with kerosene
(b.p. of 200-350 °С) is used as a fuel for making high-speed Diesel engines (tractor,
locomotive, automobile).
Ability of Diesel oil to flash in engine is characterized by a cetane number. The
cetane number is the index of flammability of Diesel oil; it equals (in %) to the cetane
(n-hexadecane) concentration in the mixture with -methylnaphthalene, that has the
same flammability as a tested fuel. A cetane number of cetane itself is 100% and of
-methylnaphthalene – 0%. The cetane number depends on the chemical composition
of fuel: alkanes have the greatest cetane number, cycloalkanes - the smaller and
arenes are characterized by the lowest one. The higher cetane number means the better quality of Diesel oil.
Burner oils are prepared by blending of residual products of a straight distillation (mazut, topped residuum and tar) with residual products of thermal and some
catalytic processes.
Gaseous petroleum fuels consist of casing-head gases and gases obtained at the
refining of petroleum and its derivatives.
The second group of petroleum derivatives includes lubricant (mineral) oils;
they form a layer of lubricant between adjoining parts of machines, rigs and engines
that leads to the decrease in the friction between parts of mechanisms (it is substituted
for internal friction in lubricant). Therefore, the main characteristic of lubricating oils
together with points of flash and of congelation is their viscosity.
Lubricating oils are subdivided into groups according to branches of their application: (1) industrial oils – for spindles, machines, etc., (2) oils for internal combustion engines – motor oils, aviation oils, etc.; (3) transmission, turbine; compressor
oils; (4) oils for steam-engines; (5) oils of special purpose. Lubricating oils are produced by merging of purified residual and distillate oils.
Modern mechanisms and engines demand lubricating oils only with dopants:
substances that are used for the improvement of working properties of oils.
Solid highest alkanes are removed from lubricating oils obtained from parafinic
crude petroleum because of the problem of their precipitation at low temperatures and
congelation of oils; this operation is called as dewaxing. Oil is dissolved in the mixture of methyl ethyl ketone, benzene and toluene, then it is cooled to –20-40 °С and
solid paraffin is filtered off followed by the distillation of solvents. Urea forms
slightly soluble complexes with highest n-alkanes; this is used for dewaxing of Diesel
fuel. Complexes mentioned above are isolated and decomposed into urea and liquid
paraffin by heating up to 60-75 °С.
180
After purification solid paraffin is used for the impregnation of matches and
leather, as insulator in the electrical engineering and for the production of candles. It
can be oxidized by air oxygen into synthetic fatty acids that are used in the production of soap. Fusion with lubricating oil leads to vaseline; it is used in medicine and
perfumery.
Liquid paraffin is purified by dissolving in benzene with the following treatment of counterflow adsorbent; then solvent is distilled off. It is used for the obtaining of highest aliphatic alcohols.
Some kings of bacteria assimilate paraffin in solution of salts containing nitrogen, phosphorus and potassium and produce protein. Then microorganisms are isolated by centrifugation and used as a food additive for animals; it consists of a protein
concentrate with vitamins and nonreplaceable aminoacids.
Greaselike products or lubricating greases (solid oil, constalin, etc.) are obtained by dispergation of stiffeners (soaps of Ca, Na or Al) in lubricating oils; they
are used for the greasing of working parts of mechanisms at high temperatures and
pressures and for the corrosive protection of metals.
Oil bitumens are produced by oxidation of tars of pitchy oils and also by merging with asphalts. Bitumens are solid or liquid water-insoluble materials.
Refinery coke is manufactured by coking of residual products of oil processing
in special cubes or furnaces. Coke is porous solid material of grey or black colour. It
is used as a solid fuel and as a raw material for the production of synthetic graphite,
electrodes for electrical furnaces and different electroindustrial wares.
Besides that, petroleum refining leads to the production of:
1) kerosene for lighting;
2) solvents: benzine (fraction with b.p. 45-170 °С), petroleum ether (40-70 and
70-100 °С), white spirit (165-200 °С). Usually solvents are produced from petroleum
casing-head gases on gas-fractionation or initial crude distillation equipments and at
the catalytic reforming;
3) lubricant-cooling liquids;
4) petroleum acids and their salts;
5) demulsifiers of oil emulsions.
3.5. PRODUCTS OF PETROCHEMICAL PROCESSING
Petrochemical industry deals with the chemical processing of petroleum derivatives. Now the production of more than 25 % of all chemical products in the
world is based on oil and hydrocarbon gases as a raw material.
In 1975 105-110 million tons of oil (about 4 % of the annual consumption of
oil) were spent in the world for petrochemical syntheses. In developed countries this
value attains 5-10 % of the annual consumption of oil. In 1990 the use of oil for
chemical synthesis amounted 10-12 %, and in 2000 – 15 % of all oil and natural gas
resources.
181
The most important hydrocarbons that are used in large amounts in petrochemical industry are as follows:
1) paraffinic (methane, ethane, propane, butane, pentane, etc.);
2) unsaturated (ethylene, propylene, butylene, divinyl, acetylene, etc.);
3) aromatic (benzene, toluene, xylenes);
4) gaseous mixture of carbonic oxide with hydrogen.
These compounds serve as a raw material for the production of monomers for
polymers, plastics and synthetic rubbers. The other direction includes the obtaining of
synthetic scours and surfactants, synthetic combustible lubricating oils, solvents, pesticides, refrigerants, antifreezes and a lot of individual organic compounds: alcohols,
acids, aldehydes, ketones, ethers, glycols, glycerin and nitro compounds. All these
substances are produced for other branches of chemical industry: aniline-dye, varnish-and-paint, pharmaceutical, vitaminous, rubber-technical, agricultural, etc.
We are indepted for professor Kuznetsov V.V. for the significant support in
English translation of this book.
APPENDIX
Table 1
Elementary composition of some oils (% of mass.)
Deposit
C
H
O
S
N
Sakhalin
Groznyy
Tyumen (Western Siberia)
Azerbaijan
Tatarstan
Volgograd region
Orenburg region
Kuibyshev region
Peninsula Mangyshlak
Bashkortostan
Komi
Western Siberia
87.15
85.90
85.92
85.30
83.34
85.10
83.85
82.78
85.73
84.42
85.47
86.23
11.85
13.10
12.88
14.10
12.65
13.72
12.02
11.72
13.00
12.15
12.19
12.70
0.27
0.80
0.36
0.54
0.21
0.02
0.85
2.14
0.4
0.06
1.93
0.25
0.30
0.13
0.66
0.03
1.62
1.07
3.00
3.05
0.69
3.04
0.09
0.63
0.43
0.07
0.18
0.03
0.18
0.09
0.28
0.31
0.18
0.33
0.20
0.10
182
Table 2
Physical properties of normal alkanes
Title
Formula
Boiling point,
°С
Melting
point, °С
Density, ρ420
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Hendecane
Dodecane
Tridecane
Tetradecane
Pentadecane
Hexadecane
Octadecane
Eicosane
Pentacosane
Triacontane
Pentatriacontane
Tetracontane
Pentacontane
СН4
С2Н6
С3Н8
С4Н10
С5Н12
С6Н14
С7Н16
С8Н18
С9Н20
С10Н22
С11Н24
С12Н26
С13Н28
С14Н30
С15Н32
С16Н34
С18Н38
С20Н42
С25Н52
С30Н62
С35Н72
С40Н82
С50Н102
–161.6
–88.6
–42.2
–0.5
36.1
68.8
98.4
125.7
149.5
173.0
195.8
214.5
234.0
252.5
270.5
287.0
317.0
344.0
259/2кPа
304/2 кPа
331/2 кPа
–
421/2 кPа
–182.5
–183.2
–187.6
–133.3
–129.7
–95.3
–90.6
–56.8
–53.6
–30.3
–25.6
–9.6
–6.0
5.5
10.0
18.1
28.0
36.5
53.3
65.9
74.6
80.8
93.0
0.424
0.546
0.585
0.579
0.626
0.659
0.684
0.703
0.718
0.730
0.740
0.745
0.757
0.764
0.769
0.775
0.777
0.778
–
0.780
0.781
–
–
183
Table 3
Physical properties of isomeric alkanes
Title
Formula
Boiling
point, °С
Melting
point, °С
Density,
ρ420
2-methylpropane
(isobutane)
СН3СН(СН3)СН3
–11.7
–159.6
–
n-butane
СН3СН2СН2СН3
СН3С(СН3)2СН3
–0.5
9.5
–133.3
–16.6
0.579
0.591
2-methylbutane
(isopentane)
СН3СН2СН(СН3)СН3
27.8
–159.9
0.62
2,2-dimethylbutane
(neohexane)
СН3С(СН3)2СН2СН3
49.7
–99.7
0.649
2,3-dimethylbutane
(diisopropyl)
СН3СН(СН3)СН(СН3)
СН3
58.0
–128.4
0.662
2-methylhpentane
(dimethylpropylmetane)
СН3СН(СН3)СН2СН2С
Н3
60.3
153.7
0.660
3-methylpentane
(diethylmethylmethane)
СН3СН2СН(СН3)СН2С
Н3
63.3
–
0.664
2,2-dimethylpropane
(neopentane)
184
Table 4
Composition of the gases of some deposits (% vol.)
Deposits
С
С
С
Н4
2Н6
3Н8
98.6
95.2
98.3
0.07
1.0
0.03
0.02
0.33
0.1
74.8
93.0
84.8
47.48
8.7
3.2
4.5
1.92
39.0
41.0
82.0
85.7
31.9
30.1
20.0
21.0
6.0
4.0
23.9
20.2
С
4Н10
С
5Н12
С
N2
+ others
О2
2S
0.013 0.011
0.07 0.03
0.04 0.02
0.18
0.40
0.13
–
–
–
3.90
0.90
1.40
0.93
1.80
0.47
0.30
0.56
6.40
0.13
1.50
3.08
0.10
–
0.10
–
1.15 35.0
21.55 21.5
4.30
2.20
5.00
1.98
18.5
17.4
3.0
3.5
5.9
23.6
6.2
6.8
3.5
2.0
2.7
10.6
4.7
4.6
1.0
1.4
0.8
4.8
0.1
0.1
5.0
2.09
1.6
1.5
11.5
7.1
1.5
.3
31.5
6.8
Gaseous:
Polar
Urengoy
nor'-Stavropol
1.11
3.009
0.11
Gas condensate:
Vuktyl
Gazli
Orenburg
Astrakhan
Casing-head gases:
Romashkin
Tuymazy
Gyznovsk
Nebit-Dag
Syzran
Lyrkhanovsk
–
2.0
–
0.01
1.70
2.40
185
Table 5
Abundance of alkanes in fractions of various oils
Hydrocarbons
Average content in fraction, % from the sum of
alkanes
For oils of the UIG
For foreign oils
Fraction 60-95 °С
n-hexane
2-methylpentane
3-methylpentane
2,2-dimethylpentane
2,4-dimethylpentane
2,3-dimethylpentane
3,3-dimethylpentane
2-methylhexane
3-methylhexane
3-ethylpentane
23.0
14.9
12.0
3.3
4.0
8.8
1.7
14.0
14.9
3.4
35.9
14.0
12.0
1.5
3.5
2.6
–
20.0
10.5
–
Fraction 95-122 °С
n-heptane
2,2-dimethylhexane
2,3-dimethylhexane
2,4-dimethylhexane
2-methylheptane
3-methylheptane
4-methylheptane
52.6
1.1
4.0
4.7
23.8
8.1
5.7
49.2
5.7
11.8
5.1
–
–
28.2
186
Table 6
Physical properties of some cycloalkanes
Melting
point, °С
3
Boiling
point, °С
4
Density,
ρ420
5
–94.4
49.3
0.7454
CH3
–142.7
71.8
0.7488
Ethylcyclopentane
C2H5
–138.4
103.4
0.7657
1,1-dimethylcyclopentane
CH3
–69.7
87.8
0.7523
–53.8
99.5
0.7723
–117.6
91.9
0.7519
-120.3
130.8
0.7756
–108.2
156.8
0.7843
–
169.0
0.4840
6.6
80.9
0.7781
–126.6
100.8
0.7692
–114.4
132.0
0.7772
–33.5
119.5
0.7840
–50.1
128.0
0.7965
–89.4
125.0
0.7760
Title
Formula
1
2
Cyclopentane
Methylcyclopentane
CH3
cis-1,2-imethylcyclopentane
CH3
trans-1,2-dimethylcyclopentane
CH3
CH3
С3Н7
Propylcyclopentane
С4Н9
Butylcyclopentane
СH2
Isopentylcyclopentane
CH3
CH
C2H5
CH3
Cyclohexane
CH3
Methylcyclohexane
C2H5
Ethylcyclohexane
CH3
1,1-dimethylcyclohexane
CH3
cis-1,2-dimethylcyclohexane
CH3
CH3
trans-1,2-dimethylcyclohexane
CH 3
CH 3
Propylcyclohexane
C 3H 7
–94.5
154.7
0.7932
Butylcyclohexane
C 4H 9
–78.6
179.0
0.7997
187
Table 7
Physical properties of arenes
Melting point
at 0,098 МPа,
°С
Density,
ρ420
Index of
refraction,
nD20
Title
Formula
Boiling
point, °С
Benzene
Toluene
Ethylbenzene
о-xylene
m-xylene
p-xylene
Isopropylbenzene (cumene)
n-propylbenzene
Mesitylene
tret-butylbenzene
Pseudocumene
Hemeliton
n-butylbenzene
1,3-dimethyl-2-ethyl
benzene
1,2,4,5-tetramethyl
benzene (durol)
1,2,3,5-tetramethyl
benzene (isodurene)
1,2,3,4-tetramethyl
benzene
n-amylbenzene
Pentamethylbenzene
Hexamethylbenzene
Naphthalene
α-methyl naphthalene
2,7-dimethyl naphthalene
β-ethylnaphthalene
α-ethylnaphthalene
Diphenyl
Anthracene
Phenanthrene
Pyrene
Chrysene
С6Н6
С6Н5СН3
С6Н5С2Н5
С6Н4(СН3)2
С6Н4(СН3)2
С6Н4(СН3)2
С6Н5–i-С3Н7
5.5
–95.0
–94.4
–25.2
–47.9
13.3
–96.9
80.1
110.6
136.1
144.4
139.1
138.3
152.4
0.8789
0.8760
0.8669
0.8801
0.8641
0.8610
0.8581
1.5012
1.4969
1.4959
1.5055
1.4970
1.4962
1.4922
С6Н5–n-С3Н7
С6Н3(СН3)3
С6Н5–tret-С4Н9
С6Н3(СН3)3
С6Н3(СН3)3
С6Н5–n-С4Н9
С6Н3С2Н5(СН3)2
–99.2
–44.7
–58.1
–43.8
–25.4
–88.5
–16.3
158.6
165.0
168.9
165.3
176.1
182.6
189.9
0.8628
0.8653
0.8669
0.8762
0.8944
0.8662
–
1.4919
1.4990
1.4925
1.5048
1.5130
1.4880
–
С6Н2(СН3)4
+79.2
196.8
–
–
С6Н2(СН3)4
–23.7
193.1
0.8906
1.5105
С6Н2(СН3)4
–6.3
205.0
0.9014
1.5185
С6Н5– n-С5Н11
С6Н(СН3)5
С6(СН3)6
С8Н10
С8Н9СН3
С8Н7С2Н5
–78.2
–13.6
+166.0
+80.3
+34.6
+97.0
204.5
210.0
265.0
218.0
241.1
262.3
0.8618
0.8830
–
–
1.029
–
1.4920
1.5075
–
–
1.6026
–
С8Н9С2Н5
С8Н9С2Н5
С12Н10
С14Н10
С14Н10
С16Н10
С18Н12
–7.0
–13.8
69.0
216.0
199.2
150.0
254.0
258.0
258.7
255.6
342.3
340.1
392.0
448.0
0.9922
1.00816
–
–
–
1.277
–
1.6028
1.6089
–
–
–
–
–
188
Table 8
Physical properties of alkenes
Boiling point, °С
Melting point, °С
Density, ρ420
Ethylene (ethene)
–169.4
–103.8
0.570
Propylene (propene)
Butylene (butene-1)
cis-butene-2
trans-butene-2
Isobutylene
Amylene (pentene-1)
Hexylene (hexene-1)
Cyclopentene
Tetrahydrobenzene
Divinyl (butadiene-1,3)
Isoprene (2-methylbutadiene-1,3)
–185.2
–185.4
–139.3
–105.8
–140.8
–165.2
–139.8
–136.1
–103.5
–108.9
–146.0
–47.7
–6.3
3.7
0.9
–6.9
30.1
63.5
44.2
82.9
–4.47
34.07
0.610
0.630-10
0.644-10
0.660
0.626
0.611
0.673
0.772
0.811
0.658 (0 °С)
0.681 (0 °С)
Title
Table 9
Physical properties of alkynes
Title
Acetylene
Methylacetylene
Butyne-1
Butyne-2
Pentyne-1
Pentyne-2
Hexyne-1
Melting point, °С
Boiling point, °С
–81.8
–102.7
–122.5
–32.3
–98.0
–101.0
–132.0
–83.6
–23.3
8.5
27
39.7
56.1
71.4
189
Table 10
Physical properties of carboxylic acids
Title of an acid
on system IUPAK
Methanoic
Ethanoic
Propanoic
Butanoic
Pentanoic
Hexanoic
Heptanoic
Tetradecanoic
Hexadecanoic
Octadecanoic
Propene-2-oic
2-methylpropene2-oic
Formula
trivial
Formic
Acetic
Propionic
Butyric
Valeric
Caproic
Enanthic
Myristic
Palmitic
Stearic
Acrylic
Methacrylic
Н-СООН
СН3СООН
СН3-СН2-СООН
СН3(СН2)2СООН
СН3(СН2)3СООН
СН3(СН2)4СООН
СН3(СН2)5СООН
СН3(СН2)12СООН
СН3(СН2)14СООН
СН3(СН2)16СООН
СН2=СН-СООН
СН2=С-СООН
│
СН3
Benzenecarboxylic Benzoic
О
Boiling
point, °С
Melting
point, °С
Density,
ρ420
8.4
16.7
–22.0
–6.5
–34.5
–9.5
–10.0
58
64
69.4
12.3
16
100.7
118.1
141.1
163.8
187
205
223.5
–
–
–
142
163
1.220
1.049
0.992
0.964
0.939
–
0.910
–
–
–
–
–
121.7
249
–
208
–
–
189.5
135.6
104
136
–
–
–
–
–
121(44)
–
–
–
–
1.034422
154
139(15)
0.9785
179
104(11)
1.051017
150
116(15)
1.00622
С
ОН
o-benzene-1,2dicarboxylic
Phthalic
С
С
О
ОН
О
ОН
Ethanedioic
Propanedioic
Hexanedioic
Butene-2-dioic
Cyclohexanecarboxylic
2,4-dimethylcyclohexanecarboxylic
Oxalic
Malonic
Adipinic
Maleic
НООС-СООН
НООС-СН2СООН
НООС(СН2)5СООН
НООС-СН=СН-СООН
С
О
ОН
СН3
СН3
О
С
ОН
Cyclopentanecarboxylic
3-methylcyclopentanecarboxylic
С
О
ОН
НО
О
С
СН3
190
Table 11
Distribution of sulphur compounds in high-sulphur crude oils
Content of
sulphur,
% mass.
Region
Bashkiria
Tataria
Kujbyshev region
Orenburg region
Perm region
Siberia
1.9-4.0
0.9-4.0
2.0-3.7
2.6-3.2
1.0-3.1
0.9-3.0
Distribution of sulphur counting upon its over-all content,
% mass.
homologues of thiophene and
thiols
sulphides
high molecular weight frames
0-10
0-2.6
0.09-7.3
0.72-2.7
0-7.2
0-74
6-40
11-36
7.4-24
7.3-20
7.6-29
0-28
50-94
61-89
69-92
77-92
63-93
26-92
Table 12
Distribution of sulphur among fractions in sulphurous and
high-sulphur crude oils, % of mass.
Region
Bashkiria
Tataria
Kujbyshev region
Orenburg region
Perm region
Siberia
Fractions, °С
start-120
120-200
200-250
250-300
0.02-0.57
0.02-0.25
0.02-0.27
0.01-0.18
0.02-0.10
0.01-0.05
0.08-1.74
0.05-1.04
0.02-0.75
0.11-0.67
0.06-0.59
0.02-0.36
0.35-2.5
0.17-2.29
0.02-1.61
0.38-1.17
0.12-1.56
0.16-0.72
0.67-3.95
0.72-3.13
0.07-3.18
1.18-2.4
0.25-2.59
0.43-1.58
191
Table 13
Group composition of sulphur compounds
Am
ount of
sulphur,
Final boiling point
%
of
of
frac- mass.
on
fraction
tions, °С
до 200
200-300
0,18
1,02
до 200
200-300
0,40
2,78
Amount of sulphur (% of mass.) on the over-all sulphur
content of the given fraction by the way:
hydrogen
sulphide
elementary
sulphur
mercaptans
sulphides
disulphides
residual
5,4
1,0
Oil A
13,6
10,4
39,7
1,0
1,6
1,9
1,1
8,8
38,6
76,9
7,3
0,0
Oil B
4,3
2,1
15,4
2,5
32,4
15,1
0,5
11,8
40,0
68,2
Table 14
Physical properties of some amines
Title
Methylamine
Dimethylamine
Diethylamine
Triethylamine
Aniline
Pyridine
Quinoline
Acridine
Pyrrole
Indole
Carbazole
Melting point, °С
Boiling point, °С
–92
–96
–39
–115
–6
–42
–5
108
–
52.5
238
–7.5
7.5
55
89
184
115
237
346
131
254
355
192
Table 15
Fractions of distillation of black oil (mazut)
Temperature of sampling, °С
Approximate fractional yield, %
Spindle
230-250
10-12
Machine
260-305
5
Cylinder: light
heavy
315-325
350-370
3
7
Residuum (tar)
350-370
27-30
Fraction
THE CONTENTS
1.
1.1
1.2
1.3
1.3.1
1.3.2
1.3.3
1.3.4
1.4
1.4.1
1.4.2
2.
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.3
2.3.1
2.3.2
2.3.3
2.3.4
2.4
2.4.1
2.4.2
2.4.2.1
The foreword
General characteristics of oil and gas
Oil and gas production
The origin of oil and gas
Main physico-chemical properties of oils
Physical properties of oils and petroleum derivatives
Elementary and an isotopic composition of oils and natural
gases
Group chemical composition of oils
Fractional composition of oils
Classification of oils
Chemical classification
Technological classification
Chemical composition of oils
Hydrocarbons of oil and petroleum derivatives
Alkanes
Constitution, isomerism, structural, formulas
Nomenclature
Physical properties
Chemical properties and processing
Alkanes of oil
Cycloalkanes
The nomenclature and isomerism
Physical properties
Chemical properties and processing
Cycloalkanes of oil and their effect on properties
Arenes and hydro carbons of mixed constitution
Structure of benzene
Nomenclature and isomerism
Monosubstituted benzenes
4
4
5
7
8
10
11
11
12
12
12
13
13
15
15
17
19
20
26
29
30
32
32
34
35
36
38
38
4
2.4.2.2
Disubstituted benzenes
38
2.4.2.3
Polycyclic arenes
39
2.4.3
Physical properties
40
2.4.4
Chemical properties and use
41
2.4.4.1
Addition reactions
41
2.4.4.2
Replacement reactions
42
2.4.4.3
Other reactions of arenes
43
2.4.5
Hydrocarbons of mixed constitution
45
2.4.6
Arenes of oil, effect on properties of petroleum derivatives
45
2.5
Unsaturated hydrocarbons
46
2.5.1
Alkenes and cycloalkenes
47
2.5.1.1
Nomenclature
47
2.5.1.2
Physical properties
48
2.5.1.3
Chemical properties and use
48
2.5.2
Alkynes
51
2.5.2.1
Nomenclature
51
2.5.2.2
Physical properties
52
2.5.2.3
Chemical properties
52
2.5.3
Unsaturated hydrocarbons of oil and petroleum derivatives
. Effect on the quality of fuels. Application.
54
2.6
Heteroatomic compounds and mineral components of oil
55
2.6.1
Oxygenous compounds
55
2.6.1.1
Acids
55
2.6.1.2
Phenols
58
2.6.1.3
Ketones and ethers
59
2.6.2
Sulfur compounds
60
2.6.2.1
Thiols
61
2.6.2.2
Sulphides
63
2.6.2.3
Disulphides
64
2.6.2.4
Sulphur compounds of oil
65
2.6.2.5
Origin of sulphur compounds of oil
66
2.6.2.6
Effect of sulphur compounds on properties of petroleum
derivatives. Application of sulphur compounds
67
2.6.3
Nitrogen compounds
67
2.6.3.1
Amines
67
2.6.3.2
Amides of acids
70
2.6.3.3
Origin of nitrogen compounds of oils. Effect on properties of
petroleum derivatives and application
72
2.6.4
Gum-asphalt materials
73
2.6.5
Mineral compounds
76
3.
Petroleum refining and processing of petroleum gases.
77
3.1
Petroleum refining
77
3.1.1
Preparation of oil to processing
77
3.1.2
Initial oil distillation
80
5
3.1.3
Chemical processes of petroleum refining
3.1.3.1
Thermal cracking, pyrolysis and coking
3.1.3.2
Catalytic processes
3.2
Processing of petroleum gases
3.3
Purification and stabilization of petroleum derivatives
3.3.1
Purification of petroleum derivatives
3.3.2
Stabilization of petroleum derivatives
3.4
Products of petroleum refining
3.5
Products of petrochemical processing
APPENDIX
CONTENTS
83
83
86
87
89
89
89
89
92
93
105