May A5', l1942*.
w. J. MA1-'rox
2,282,231
SEPARATION OF AROMATIC HYDROCARBONS
Filed April 19, 1941
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M7731.
Patented May 5, 1942
' 2,282,231
UNITED STATES PATENT OFFICE
william J. Matrox, chicago, nl., “signor to Uni
versal Oil Products Company, Chicago, Ill., a
corporation of Delaware
Application April 19, 1941, Serial No. 389,448
9 Claims. ' (Cl. 26o-674)
'I'his invention relates to a process for sepa
of these aromatic hydrocarbons and the boiling
points of the corresponding naphthenic hydro
carbons produced therefrom by hydrogenation.`
Thesey different boiling points are indicated in
rating ethyl benzene from 4isomeric xylenes.
More specifically the process is concerned with a
combination of chemical and -physical methods
for separating ethyl benzene from m- and p iu
xylehes which are often present in' hydrocarbon
the following table:
.
`
fractions containing ethyl benzene.
Because of the very small differences -between
the boiling points of ethyl benzene and m- and
.
.
Boiling
point
Aromatic hydrocarbon`
p-xylenes, separation of these aromatic hydro
'
Boiling point
_
of aromatic
igfgcgâìâïägc
hydrocarbon
hydrocarbon
10
carbons can not be made efficiently by means of
fractional distillation. Other commercial meth
ods of effecting such separations are either not
known or have not been put into general use.
Ethyl benzene __________ __
_
'
I
136
'
132
p-xylene ________________ __
_
138
120
m-xylene. _ _ __
_
139
121
o-xyiene _____________ _ _ _ _________ __
144
129
In the case of o-xylene, this isomer boils from _
5° to 8° AC. (9° to 14° F.) -higher than ethyl-ben
zene and the other -xylenes'and therefore can
be substantially separated therefrom by dis
tillation.
y
.
Ethyl benzene and alsoA some m- and p
xylenes are separated from the higher boiling
o-xylene by fractional distillation. Since ethyl
~ benzene boils about 8° lower than o-xylene, this
Since ethyl benzene has now become a highly 20 separation is readily accomplished. -The re
important compound in industrial manufactur
maining mixture containing ethyl benzene and
ing processes and especially in the production of
m- and p-xylenes is then hydrogenated by any
styrene, the latter being used in the manufacture
of several well-known hydrogenation processes to
of resins, a suitable method is needed for sepa
give a commingled mixture of ethyl cyclohexane
>rating ethyl benzene from the xylenes which
either occur with it in'distillates obtained from
coal tar, or are formed >simultaneously in manu.
facturing processes as by the dehydrogenation
and cyclization of aliphatic- hydrocarbons to
yield aromatic hydrocarbo
_
‘
In one specific embodiment the present inven
tion comprises a process for separating ethyl
benzene from a mixture comprising essentially
ethyl benzene and isomeric xylenes which com'
prises fractionally distilling -said mixture to re
,moveA a relatively lower boilingfraction contain
ing m- and p-xylenes and. ethyl benzene from a
residue of higher boiling o-xylene, subjecting
said relatively lower boiling fraction to catalytic
hydrogenation to form a naphthenic hydrocar
bon mixture including ethyl cyclohexane and
dimethyl cyclohexanes, separating said naph
thenic hydrocarbon mixture by distillation into
and m'- and p-dimethyl> cyclohexanes.
The re- .
sulting ethyl cyclohexane, which boils from 11
to 12° C. higher than the m- and p-dimethyl
cyclohexanes, remains after the dimethyl cyclo
hexanes are removed by fractional distillation
30 and then the ethyl cyclohexane` is dehydro
genated in the final step of the process to yield
ethyl benzene. The hydrogen liberated in this
dehydrogenation treatment is returned to the
hydrogenation stage of the process for further
35 use in convertingaromatic hydrocarbons into
'naphthenic hydrocarbons. As desired, the di
` methyl cyclohexanes so separatedfrom ethyl
cyclohexane may or may not be reconverted
into xylenes by dehydrogenation.
A number of catalysts may be employed for `
effecting the hydrogenation and dehydrogenation
treatments used in effecting the aromatic hy
drocarbon separation process as hereinafter set
forth. At temperatures` of from about 100°.to
dimethyl cyclohexanes and an ethyl cyclohexane '
45 about 150° C. tire aromatic nucleus maybe hy
fraction, catalytically dehydrogenating said ethyl
cyclohexane fraction to give ethyl benzene and
drogenated readily in the lpresence of nickel cata
a hydrogen-containing gas, and recycling said` ‘ lysts with substantially no isomerization of the
hydrogen-containing gas to further use in the
products o_r formation of secondary reaction
hydrogenation o1'y an additional quantity of the
products and therefore the yield lof desired
fraction comprising essentially m and p-xylenes 50 naphthenicïhydrocarbon is practically-quantita
and ethyl benzene being charged to the lhydro
genation step of the process.
The process of this invention for separating
ethyl benzene from the isomerlc xylenes makes
use of the diiferences'between the boiling points
tive.
‘
-
'
~
_
A veryV emcient nickel catalyst .has been pre
pared by precipitating basic nickel carbonate in
‘ the presence of diatomaceous earth by adding
sodium carbonate solution to al solution of
2,282,231
troduced thereto are converted into the corre
nickelic‘ sulfate. The resulting precipitate vis sponding
naphthenic hydrocarbons with substan
2.A
' then. washed free from suliates, -dried, heated
tially no decomposition, cracking, or other -unde
- to decompose nickel carbonate, and iinally re
to form a catalyst con'taining about 65A o nickel and about 35% dia 5
sirable side reactions.
duced with hydrœen
-
.
are directed therefrom through line 20 and valve `
tomaceous earth. -Such catalysts containing
' nickel operate usually at temperatures of'from
'
The products from hydrogenation reactor Il
2l- to fractionator 22 of conventional design in
_ which a hydrogen-containing gas, a 'di-methyl
about 50° to about 200° C. and. underva pressure
fraction, and ethyl cyclohexane are
of 4from substantially atmospheric to 100 or morefio` cyclohexane
substantially-separated. The hydrogen-contain
atmospheres.
ing gas is directed from iractionator 22 through
The hydrogenation stage of the present ,proc
'
line 23 and valve 2l to’ line 38 through. which it is
recycled tocommingle with thematerials charged
to hydrogenation reactor I9. A substantially di
other supported nickel catalysts, other catalysts
A containing copper, iron, cobalt, platinum, pal 15 -methylcyclohexane fraction is withdrawn from
ess may also be carried out in the process of
other forms of nickel such as “Raney" nickel, ,
ladium, chromium, molybdenum, etc.,l as metals.l
fractionator 22` through lin'e 25 -and valve 26 to
or as metal oxides either alone or in admixture . cooling and stora , not shown, or to any other
with nickel or> with supporting materials such I -desired use. Aîsîibstantially ethyl cyclohexane
' fraction is directed Afrom the >bottom of fraction
as alumina, magnesia„etc. For example, an ei
ator 22 through line 21 and valve 28 to pump 23
ñcient hydrogenation catalyst comprises oxides 2,0 which
discharges through line 30 and valve 3i into
of copper and chromium either with or without
'the addition of small percentages of nickel even '
as 1ow- as o.oo1 to 0.2%. catalysts or the types
dehydrogenation reactor 32 containing a catalyst
suitable for converting Aethyl cyclohexane into-
ethyl benzene and hydrogen with substantially no
indicated _are active for the hydrogenation _of
aromatic hydrocarbons when operating at tem 25 cracking or decomposition into .undesired prod
peratures `of -from about 200°- to about- 350° ._C.
The products from dehydrogenation reactor 32
and under a pressure cg; approximately 100 at
are directed through line 33 and valve `3l to gas
mospheres ofvhydrogen.
‘
f. `
separator 35 in which a gas comprising essentially
A rather wide variety of catalysts may be used
forv dehydrogenating ethyl cyclohexane to ethyl «30 hydrogen is separated fromethyl benzene. 'The
hydrogen-containinggas is withdrawn from gas
benzene-or, when desired, for converting thev di-.l
separator'35 through line 36 containing valve 31.
methyl cyclohexanes into isomeric xylenes. At
part of the hydrogen-containing gas may
temperatures varying from about 250° to'about ' While
be discharged through valve 31, at least a portion
600°' C.- andV at substantially atmospheric pres
sure or under a slightly elevated pressure, nickel 35 of said gas is directed through recycle line 38 and`
valve >39 .to compressorv 40 4which discharges
catalysts of the types described above for- hydro
through line 4I and valve 42 into line I2, already
genation have been found active and eiiicient for
mentioned, through which the mixture lof aro-v
dehydrogenation. In` addition to these nickel ,
hydrocarbons and hydrogen is introduced
catalysts, various metal oxides may be used, par- - 40 matic
to hydrogenation reactor I9. From gas separator
vticularly such oxides as those of' metals in the
ucts.
’
yleft-hand columns oi groups V ‘and VI of the
_
n
.
.
»3l the ethyl benzene fraction is withdrawn
-periodic table and especially oxides of vanadium,
through line 43, valve 4l, cooler 45,'line I6, and
able _supports or carriers.
eilecting the separation of ethyl benzene from
isomeric xylenes. Since the hydrogenation and
dehydrogenation reactions used in this process
valve 41 to storage or to further use as desired.
'_chromium, and molybdenum, or oxidesof zinc, '
According to the process of the present inven-) .
aluminum, magnesium, etc. used-¿either alone, in , .m tionhydrogen
is used essentially as a. tool for
mixtures’with each other, or deposited -upon suit-.
4
.
- For the purpose of illustrating they process of
the present invention, the` attached drawing
‘ shows diagrammatically one form of an apparatus
are accompanied by relatively low losses due°to
in which the various Ísteps may be carried out for ‘t0 decomposition, cracking, or 'other undesirable side
reactions, av highly efIicient separation of ethyl
separating ,ethyl benzene` from a mixture` con-_
benzene is eilected.
Y
~
taining ethyl benzene and isomeric xylenes. L
~The following example‘is introduced to illus
Referring to the drawing, a hydrocarbon 'mix-. .
trate the results» normally expected from the
Ature'containing ethyl benzeneV and xylenes is
'- introduced through line I and valve 2 to pump 3 ‘.55 process. although this example‘is not presented
with the intention of unduly limiting the broad
which discharges throughline I and valve l into
, tractionator4 6-01. conventional design in which a
mixture comprising essentially ethyl benzene,- m
scope of the invention.
'
A hydrocarbon mixture formed by dehydro?
and p-xylenes isseparated from relatively higher . cyclization of 100 parts -by weightl of normal
boiling',o-xyl'ene, the latter >material being with 60 octane in thel presence of a chromia-alumina
catalyst and consisting of approximately 15 parts
drawn from fractionator. 3 through line 1, valve
3, cooler 9,:line III, and valve _VII to'storage or to , by weight of ethyl benzene, 35 parts by weight of
a xylene mixture containing about equal amounts
further treatment or use as desired. yThe mixture
of o-, m-, and p-xylenes. l0 parts by weight of
comprising essentially ethyl'benzen'e and m- andp-xylenes is directed from iractionatdr i through Ae5 octenes, and 20 parts by`weight of unconverted
octane is fractionally distilled and separated-’into
line I2, therein commingled with at least three
molecular proportions of hydrogen :introduced
an octane-octane fraction, a mixture comprising
essentially ethyl benzene and m- and »p-xylenes,
and a' residue‘consisting of substantially pure
One molecularproportion of said mix
into line> I2 andthehce passes through valve I3 70 Yo-xylene.
ture comprising essentially ethyl benzene and m
into hydrogenation reactor Il preferably con
and p-xylenes is commingledv with‘4 molecularI
tainin'g. a ilxed bed hydrogenation csgtalyst such
through line I3 and valve Il-t'o compressor II
I >which discharges` through line I3A and valve: I1
as one of those hereinabove set iorth‘and-.oper- _
proportions of vhydrogen and rthe commingled
.mixture is passed at"150° C. under a pressure of
~76
20 atmospheres through a reactor containing a
stantially all of lthe aromatic hydrocarbons in
ated at such a temperature and pressure that sub
i
.
aasaasí
_ ñxed bed ot hydrogenation catalyst comprising
approximately 65% by weight of reduced nickel
and'35% by weight of diatomaceo'us earth. Hy
drogenation to ethyl cyclohexane and di-methyl
cyclohexanes is substantially complete after one
3
m- and p-xylenes and a hydrogen-containing ,
gas, and recycling said hydrogen-containing gas
\ to further use in the hydrogenation oiv an addi
tional quantity of the mixture being charged to
5 the hydrogenation step of the process. -,
pass over the catalyst when approximately 1 vol
4. A process for separating ethyl benzene from
a mixture comprising essentially ethyl- benzene
charged Der hour through 1 volume of the nickel
and isomeric xylenes which comprises fraction-diatomaceous earth catalyst.
ally distilling said mixture to lremove a relatively
Fractional distillation of the hydrogenation .10 lower boiling fraction containing m.- and
product separates approximately 14 parts by
4p-xylenes and ethyl benzene from a residue of
weight oi substantially pure ethyl cyclohexane“
higher boiling o-xylene, subjecting 1 molecular
from a mixture containing about .24 parts by
proportion oi.' said relatively lower boiling frac
weight of di-methyl cyclohexanes and 1 part by
tion and at least 3 molecular proportions of lhy
weight of ethyl cyclohexane. Passage of the sub 15 drogen to contact with a hydrogenating catalyst
ume of liquid aromatic hydrocarbon mixture _is
stantially pure ethyl cyclohexane fraction over
' under conditions'of temperature and pressure
a composite comprising essentially 8% by weight
of chromium sesquioxide' and 92% by weight of
adequate to form a naphthenic hydrocarbon mix
ture including ethyl- cyclohexane and di-methyl
cyclohexanes, separating said naphthenic hydro
alumina at 500° C. under substantially atmos
pheric pressure using an ethyl cyclohexane
charging rate corresponding to a liquid space
velocity of 1 gives substantially complete con
version into ethyl benzene and hydrogen, the
carbon ' mixture by distillation into dimethyl
cyclohexanes and an ethyl cyclohexane fraction,
catalytically dehydrogenating said ethyl cyclo
hexane fraction to give ethyl benzene and a hy
latter being compressed and recycled to com- l
drogen-containing gas, and recycling said hy
mingle with the mixture ot ethyl benzene, m- and 25 drogen-containing gas to further use in the hy
p-xylenes, and added hydrogen beingv conducted
to the hydrogenation stage of the process.
drogenation of an additional quantity of the
fraction comprising essentially m- and p-xylenes
Y
The nature of the present invention and its
-and ethyl benzene being charged to the hydro
commercial utility are evident iromthe speciñca
genation step~ of the process..
. _
tion and example given, although neither section 30 5. A process for separating ethyl benzene from
is intended to unduly limit its generally broad
.a mixture comprising essentially ethyl benzene
scope.
and -isomeric xylenes which comprises traction
'» ally distllling said mixture to remove a relatively
I claim’as my invention:
1. A process for separating ethyl benzene from
lower vboiling fraction containing m- and
a mixture comprising essentially ethyl benzene in) p-xylenes and ethyl benzene from a residue of
and isomeric xylenes which comprises fraction
higher boiling o-xylene, subjecting 1 molecular'
. ally distilling said mixture to remove a relatively
proportion of said relatively lower boiling traction t
lower boiling fraction containing m- .and
higher boiling o-xylene, subjecting said rela
tively lower boiling fraction to catalytic hydro
andvat least 3 molecular proportions of hydrogen
to contact with a hydrogenating catalyst under
conditions of temperature and pressure adequate
to form a naphthenic hydrocarbon mixture in
genation to form a naphthenic hydrocarbon mix
cluding ethyl cyclohexane and dimethyl cyclo
p-xylerìes and ethyl benzene from a residue of
ture including ethyl cyclohexane and dimethyl
hexanes, separating said naphthenic hydrocar
cyclohexanes, separating said naphthenic hydro
bon mixture by distillation into dimethyl cyclo
carbon mixture by distillation .into dimethyl 45 hexanes and an ethyl cyclohexane fraction. sub
cyclohexanes and an ethyl cyclohexane fraction,
jecting said ethyl cyclohexane fraction to con
and catalytically dehydrogenating said ethyl
tact with a nickel-containing catalyst at a tem
cyclohexane fraction to give ethyl benzene.
perature 'of from about 250° to about 600°.C. to
2. A process for separating ethyl benzenefrom
form ethyl -oenzene and a hydrogen-containing
a mixture comprising essentially ethyl benzene,
50 gas, and recycling said hydrogen-containing gas
m-xylene, and p-xylene which comprises subject- _ to further use in the hydrogenation of an addi
ing said mixture to catalytic hydrogenation to
form a naphthenic hydrocarbon mixture includ- '
ing ethyl cyclohexane and dimethyl cyclohexanes,
separating said naphthenic hydrocarbon mixture 65
by distillation into a dimethyl cyclohexane irac
tion and an ethyl cyclohexane fraction, catalyti
cally dehydrogenating said Aethyl cyclohexane
fraction to give ethyl benzene and a hydrogen
containing gas, and recycling said hydrogen-con
taining vgas to further use in the hydrogenation
of an additional Aquantity of the mixture being
charged to the hydrogenation step of the process. .
tional duantity of the fraction comprising es
sentially m- and p-xylenes and ethyl benzene be
ing charged to the hydrogenation step of the
process.
6. A process for separating ethyl benzene from
a mixture comprising essentially ethyl benzene,
m-xylene, and 'p-xylene which comprises sub
jecting 1 molecular proportion of said mixture
and at least 3 molecular proportions of hydrogen
lto contact with a dehydrogenating ,catalyst un
der> conditions of temperature and Apressure ade
quate to form a naphthenic hydrocarbon mix
3. A process i'or separating ethyl benzene trom
ture including ethylcyclohexane and dimethyl
a mixture comprising essentially ethyl benzene, 65 cyclohexanes. separating said naphthenic hydro
m-xylene, and p-xylene which comprises subject
carbonhmixture by distillation into a dimethyl
ing said mixture to catalytic hydrogenation to
cyclohexane fraction and an ethyl cyclohexane
form a naphthenic hydrocarbon mixture includ
fraction, catalytically dehydrogenating said ethyl
ing ethyl cyclohexane and dimethyl cyclohexanes,
cyclohexane fraction to give ethyl benzene and .
separating said naphthenic hydrocarbon -mixture 70 a-hydrogen-containlng gas, and'recycling said
-by distillation into an ethyl cyclohexane fraction
and -a dimethyl cyclohexane fraction, separately
4catalytically dehydrogenating said ethyl cyclo
hydrogen-containing gas to further use in the
hydrogenation of an additional quantity o! the
" mixture >being charged to the hydrogenation step
hexane fraction and said dimethyl cyclohexane
of the process.
traction to giveV ethyl benzene. a mixture of 75 7. A process for separating ethyl benzene from
/
Ü ’3,289,031
a mixture lvcomprising
,
_
`subjecting said >ethyl «cyclohexane traction 'to '
contact with a compositeïof a maior proportion
ethyl benzene
and isomeric xylenes ,which comprises .fraction
_Y -_ lower boiling fractioncontaining‘m- an'dp-xyl»-
" ot a carrier and a relatively smaller proportion
» o! an oxidevof an! element selected from the
. `enea and ethyl benzeneirom a residuen! ¿high-f
er boiling o'--xylene,~ subjecting 1 molecular'pro
-’ 'oz the periodic table to form ethyl benzene and
ally distilling said mixture to remove a relatively
members of the left-hand column of group VI
a hydrogen-containing gas, and recycling> said
_portion- of said relatively lower boiling fraction
hydrogen-containing gas to `further" use in the
and atleast 3 molecular proportions of hydrogen'
'hydrogenation of an additional quantity >of said
to contact' with a hydrogenating catalyst‘under
conditions of temperature and pressure adequate 10 relatively lower boiling traction containing‘m- `
and p-xylenes and ethyl benzene being charged
to form anaphthenic-hydroc'arbon mixture in»v
to the hydrogenation step o! the process.
cluding' ethyl cyclohexane?and- dimethyl cyclo
9. 'A process' for separating ethyl benzene from
hexanes, separating said naphthenic Ihydrocar
a mixture comprising essentially ethylbenzene
` bon mixture by distillation into; dimethyl cyclo-`
hexanes and an ethyllcyclohexane fractiomsuh 15 and isomeric xylenes which comprises traction
ally distilling said mixture to remove a relatively
jecting said ethyl’cyclohexane fraction to con- -
lower-boiling fraction containing m- q»and p-xy-`
tact with `a composite of a major proportion of .
lenea and ethyl benzene from a residue of higher
a carrier and a relatively smaller proportion of
boiling o-xylene, subjecting l molecular propor
an oxide-oi. an: element“ selected' from the mem
bers of theleft-hand column of groupl Vo! the 20 tion of said `relatively lower boiling fraction and
atleast y3 molecular proportions of hydrogen to
periodic table to form ethyl benzene and a hy
drogen-containing Bas. 'and recycling said hy-A 'contactfwithß a hydrogexíating catalyst under
conditions of temperature and pressure adequate
drogen-containing .gas to further use in the hy
drogenation- ci an additional quantity o!I said ' to form a naphthenic hydrocarbon mixturefin»
cluding ethyl cyclohexane andy m- and >iJ-di
relatively lower boiling traction containing nti-v
methyl ,cyclohexanea separating said naphtl'lenlcl
and p-xylenes and ethyl benzene being charged
hydrocarbon mixture by distillation into an ethyl
to the hydrogenation stepof. the process.
' ' 8. Aprocess lor separating ethyl benzene from
_ cyclohexane fraction and a dimethyl cyclohex--
a mixture comprising essentiallyv ethyl benzene
and isomeric xylenes which comprises fraction
$0’- genating said ethyl cyclohexane fraction and said
ally distilling said mixture to removev a rela
tively lower boiling fraction containing m- and
p-xylenes and lethyl .benzene from a residue of
ane fraction, 'lleparatelyil catalytically dehydro
higher boiling o-xy1ene, subjecting 1 molecular
dimethyl cyclohexane traction in the presence of
a> composite oi' a _maior proportion of alumina
and a relatively smaller proportion'of an oxide
of chromium to give ethyl benzene, a mixture ot
proportion of said relatively lower boiling -irac-' 86 m-xylene and p-xylene, and a hydrogen-contam
tion and lat least 3 molecular proPOrtions of hy- '
drogen _to contact with a hydrogenating catalyst
under conditions of _temperature and pressure
adequate to form naphthenic hydrocarbon mix
ing gas, and recycling said hydl'cgcn-containing
~ ygals to further >use in the- hydrogenation o! an ,
additional quantity o! Vsaid relatively lower boil
ing Afraction containing m- -and p-xylenes and
ture including eth l cyclohexane‘pand. dimethyl 40 ethyl benzene being chargedy to the hydrogena
tion step'ot the process.
‘
.
v
cyclohexanes, separating said naphthenic hydro
carbon mixture by distillation into‘ dimethyl cy
clohexanes- and an ethyl cyclohexane fraction.
u
.1. mirroir.V