Patented Oct._ 17, 1944
2,360,685
UNITED STATES PATENT OFFICE.
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2,360,685
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AZEOTROPIC DISTILLATION
'Ernest Petersen Jensen, Belle, W. Va., assignor to
E. _I. du Pont de Nemours & Company, -Wil
mmgton, Del., a corporation of Delaware
NoDrawing. Application August 10', 1943,
Serial No. 498,084‘
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20 Claims.
_ his invention relates to a method for separat-_
ing substances which boil closely together or form
binaries such that separation cannot be achieved
by simple fractional distillation. More particu
larly, this invention relates to the separation of
hydrocarbons from mixtures of hydrocarbons
and alcohols produced by hydrogenation of coco
nut oil.
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(Cl. 202-42)
ties and alcohols having 8 to l8 carbon atoms
still remain in the residue,
In accordance with .
this invention, fresh propylene glycol is added to
the residue and hydrocarbon-propylene glycol
azeotrope is distilled out, thus removing the hy
drocarbon impurities. Other glycol substances,
namely trimethylene glycol, ethylene glycol, 1,3- .
butylene glycol and‘ the like could be used in place
Y
It is an object of this invention to provide a
of propylene glycol, but I prefer to use propylene
method for separating closely boiling‘ substances 10 glycol because it is‘one of the products of coconut )
or substances which form azeotropes where sepa
oil hydrogenation.
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ration by fractional distillation is dif?cult or im
According to my preferred method, the mix
practical‘. It is a further object of the invention
ture of alcohols having 8 to 18 carbon atoms per
to provide a method for separating hydrocarbon
molecule, produced by hydrogenation of coconut
impurities from alcohols containing 8 or more 15 oil, and containing as impurity hydrocarbons
carbon atoms. A still further object of this in
(dodecane, tetradecane and other similar‘ normal
vention is to remove hydrocarbon impurities from
aliphatic hydrocarbons) is treated with propyla
the alcohols obtained in the hydrogenation of ,
ene glycol, and thereafter the hydrocarbons are
coconut oil.
distilled o?’ as azeotropes with propylene glycol.
In accordance with this invention, those hydro 20 ~ The resulting azeotropes on condensation contain
carbons produced as by-products or impurities
two phases, namely an upper hydrocarbon phase,
in the hydrogenation of coconut oil to alcohols
and a lower propylene glycol phase. The lower
may be separated from the alcohols by addition
propylene
glycol phase is preferably drawn 01T
to the mixture of alcohols and hydrocarbons of
and returned to the still kettle, the operations
a glycol substance followed by distillation of the
being continued in this manner until substan
resulting azeotrope.
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tially all of the hydrocarbon impurity has been
Some‘ of the oils of the coconut oil group are
removed from the still-kettle contents. The dis
Areca nut fat, Aouara kernal oil, babassu oil,
tillation residue ‘is then treated with water to
cohune oil, coyal oil, Ouricury kernal oil, Maripa
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fat, palm kernal oil and tonka butter. These oils, 30 remove propylene glycol.
When the propylene glycol is recovered and re
upon hydrogenation, yield alcohols having 8 to 18
cycled in the ‘above manner, a small amount of
propylene glycol willsu?ice for removal of com
carbon atoms, andalso hydrocarbons which ‘may
be formed by over-hydrogenation. In addition
to these products the hydrogenation of these oils
yields propylene glycol. However, in many instances, the amount of propylene glycol formed
by the hydrogenation reaction is not suf?cient to
" remove the hydrocarbon impurities from the al
cohols by azeotropic distillation. Generally, what
paratively large amounts of-hydrocarbon. If de
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sired, very large amounts of glycol may be em
_ ployed without deviating from the principle of
this invention, since it is possible to remove any
excess from'the still-pot residue by extraction
with water. However, I ?nd it convenient to
. happens when the raw hydrogenated product is, 40 employ from 0.2 to 20 parts, of glycol substance
distilled is that ?rst a lowboiling cut including
per part _of hydrocarbon to b‘e removed.
water comes over, then azeotropic mixtures con
The following‘ table gives the boiling points of
certain azeotropes produced in accordance with
taining propylene glycol. After the propylene gly
_ col has thus been removed, hydrocarbon impuri
this invention.
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Boiling points of azeotropes
Boiling points at varionspressures '
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Azeotrope components
M
Propylene glycol-dodecane .................. __
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Propylene
glycobtetradecane.................-_ _
Ethylene g ycol-dodecanenn.
Ethylene glycol-tctradecane ................. "
Atmphe?c'
6
175 C’
17
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$3. $53. $3. 11%.
130
135 ‘
120.5
126
135
125
10111
111
110
13s
11s
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‘2,800,685
. more carbon atoms, obtained by hydrogenation
[The invention is further illustratd by the fol
lowing examples, without being restricted thereto.
Example 1.-—A sample of impure n-octanol,
produced by fractionating coconut oil hydrogena
of coconut oil itself.
I claim:
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1. A process for separating normal aliphat
hydrocarbons, having 12 to 14 carbon atoms per
molecule, from mixture with normal aliphatic
tion product, had a hydroxy number and a spe
ci?c gravity such that the presence of hydrocar
bon impurities was indicated. To 100 parts of
alcohols having am 18 carbon atoms per mole
cule which comprises introducing into the hydro
this impure n-octanol was added 25 parts of pro
pylene glycol, and the mixture was distilled at
subatmospheric pressure. -A binary azeotrope
which contained 40 volume percent upper hydro
carbon layer and 60 volume percent lower pro
pyiene glycol layer distilled over at 120.5° C.,
carbon-alcohol mixture a glycol selected from the
class consisting of propylene glycol, trimethylene
glycol, ethylene glycol and 1,3-butylene glycol, in
quantity'equivalent to from 0.2 to 20 parts per
part of hydrocarbon in the mixture, distilling off
an azeotrope of the hydrocarbon and glycol, re
covering the hydrocarbon and glycol from the
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trope had been collected to permit satisfactory
100 mm.
After a su?loient amount of the azeo
azeotrope, washing the distillation residue to re
move glycol therefrom, and purifying the residual
alcohols by distillation.
separation of the layers,‘ the lower layer was
_ drawn off and continuously returned to the still
kettle at" approximately the same rate at which
2. In a process for manufacturing products of
the condensate was formed. The distillation was
continued in this manner until substantially no 20 increased alcohol content from mixtures contain
ing non-cyclic hydrocarbons, and non-cyclic alco
» more hydrocarbon was'removed from the still
hols having 8 to 18 carbon atoms per molecule,
such alcohols being di?lcult or impractical to
kettle contents, The recovered hydrocarbon, on
redistillation, boiled at 145° 0., 100 mm., which is
separate‘ from the admixed hydrocarbon by frac
tional distillation, the steps which comprise in
the boiling point of dodecane. The distillation
_ residue after being washed with water to remove
troducing a glycol selected from the class con
propylene glycol, was puri?ed by redistillation.
sisting of propylene glycol, trimethylene glycol,
ethylene glycol and 1,3-butylene glycol, into the
It boiled at 135° C., 100 mm., ‘which is the boiling .
point of n-octyl alcohol.
Example 2.—Example l was repeated, except
that the distillations-were all performed at at
30
mospheric pressure. The boiling points observed
were: propylene. glycol-dodecane azeotrope, 175° .
mixture, distilling off an azeotrope of the hydro
carbon and glycol, and treating the distillation
residue with water to free it of the glycol.
3. In a process for removing hydrocarbons from
alcohol-containing products obtained by hydro
0.; dodecane, 216° C.; and n-octyl alcohol, 195° C.
genation of coconut'oil, the steps which comprise
Example 3.—A mixture containing 2 parts of
introducing propylene glycol into the hydrocar
tetradecane, 5 parts of propylene glycol and 93 35 bon-alcohol mixture, and distilling off an azeo
parts of n-decyl alcohol was distilled at'subat
tropic mixture containing propylene glycol and
‘mospheric pressure. A binary azeotrope which
hydrocarbon.
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contained 30 ,volume percent upper tetradecane
4. In a process for separating hydrocarbons
layer, and '70 volume percent lower propylene
from alcohols having 8 or. more carbon atoms,
glycol layer was distilled, boiling at 114° C., 64
such hydrocarbons being diillcult to separate by
mm. Propylene glycol was thereafter washed
fractional distillation from alcohols having 8 to
from the still-kettle contents, and the distillation
10 carbon atoms per molecule, the steps which
was resumed. N-decanol, substantially free of
comprise introducing propylene glycol into the
hydrocarbon was collected, boiling at ‘165° C.,
hydrocarbon-alcohol mixture, distilling oil a hy
100 mm.
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45 drocarbon-propylene glycol azeotrope, washing
Example 4.—A mixture of crude alcohols ob
the distillation residue with water to remove
" tained by hydrogenation of coconut oil was dis
propylene glycol therefrom and purifying the res
tilled to- remove foreshot which boiled at 70-230“
idual alcohols by distillation.
0., at atmospheric pressure. To 100 parts of the
5. In a process for separating hydrocarbons
resulting residue was added 10 parts of propylene 50 from
alcohols having 8 or more carbon atoms,
glycol and the mixture was distilled at atmos
such hydrocarbons being difficult to separate by
pheric pressure. A fraction which contained 30
‘fractional distillation from alcohols having '8 to
volume percent upper hydrocarbon layer and '70
10 carbon atoms per molecule, the steps which
volume percent lower propylene glycol layer was
comprise
introducing propylene glycol into the
collected, boiling at I'll-173° C. The hydrocar 65 hydrocarbon-alcohol mixture, and distilling off a
_ bon layer was drawn oil, and was redistilled, yield
. ing pure tetradecane which boiled at 252.5° under -
atmospheric. pressure. The propylene glycol layer
was removed and distilled, yielding pure propyl
ene'glycol which boiled at 187° C. under atmos
pheric pressure.
While I have illustrated my invention by cer-'
tain applications and examples, I donot limit
my claims to such speci?c ,cases, for there are
many problems of separation whose solutions may
employ. as a basic principle the separation of non
cyclic'hydr'ocarbon from closely boiling alcohols
having 8 or more carbon atoms per molecule, by
azeo'tropic distillation of the hydrocarbon with a '
hydrocarbon-propylene glycol azeotrope.
6. In a process for manufacturing products of
increased alcohol content from mixtures contain;
ing non-cyclic hydrocarbomand non-"cyclic 'alco
hols having 8 to 10 carbonatoms per ‘molecule,
such alcohols being di?lcult or impractical to
separate from the admixed hydrocarbon by frac
tional distillation, the steps which comprise in
troducing propylene glycol into the mixture, dis
tilling off an azeotrope of propylene glycol and
hydrocarbon, and treating the distillation residue
with water to remove propylene glycol therefrom.
'7. A process for separating normal aliphatic
hydrocarbons, having from 12 to 14 carbon atoms
glycol substance.‘ The method of this invention 70
per molecule, from normal aliphatic alcohols hav
may be employed for the separation of the non-,
ing from 8 to 18 carbon atoms per molecule which
cyclic hydrocarbon impurities from the impure
comprises introducing. into such hydrocarbon-al
alcohols which are'obtained by hydrogenation of
cohol mixture propylene glycol in quantity equiv
coconut oil acids, such alcohols being similar to
or identical with'the alcohols, containing 8 or 15 alent to from 0.2 to 20 parts per part of the hy
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2,360,686
drocarbon, distilling off an azeotrope of hydrocar
bon and propylene glycol, recovering the hydro
carbon and propylene glycol from the'azeotrope,
washing the distillation 'residue with water to
glycol from the azeotrope, washing‘the distilla
remove propylene glycol therefrom, and purifying
the residual alcohols by distillation.
taining non-cyclic hydrocarbon, and non-cyclic
tion ‘residue with water to remove propylene glycol
therefrom and distilling the residual alcohols.
13. In a process for manufacturing products
of increased alcohol content from mixtures con
alcohols having 8 to 18 carbon atoms per molecule,
8. A process for separating normal aliphatic
hydrocarbons, having‘from 12 to 14 carbon atoms
per molecule, from admixture with alcohols hav
ing 8 or more carbon atoms per molecule which
such alcohols being dif?cult or impractical to sep
comprises introducing into such hydrocarbon
containing mixture propylene glycol in quantity
propylene glycol per part of hydrocarbon present,
equivalent to from 0.2 to ZO-parts per part of the
hydrocarbon, distilling off an azeotrope of hydro
and the hydrocarbon.
carbon and propylene glycol, recovering the hy
mixtures containing dodecane 'and n-octyl- al
arate from the admixed hydrocarbon by frac
tional distillation, the steps which comprise in
troducing into the, mixture 0.2 to 20 parts of
and distilling off an azeotrope of propylene glycol
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14. In a process for separating dodecane from
dro'carbon and propylene glycol from the azeo
cohol, the steps which comprise effecting a ratio
trope, and washing the distillation residue with
of 0.2 to 20 parts of propylene glycol per‘ part
water to remove propylene glycol therefrom.
of dodecane, distilling off an'azeotrope of dodecane
9. A process for separating normal aliphatic 20 and propylene glycol, recovering propylene glycol
hydrocarbons, having 12 to 14 carbon atoms per
and dodecane from the azeotrope, and treating
molecule, from normal aliphatic alcohols having 8
the distillation'residue with water to free it of,
to 18 carbon atoms per molecule which'comprises _
introducing propylene glycol into such hydro
propylene glycol.
15. In a process for separating dodecane from
25 mixtures containing dodecane and n-octyl alcohol
the steps which comprise introducing propylene
trope of hydrocarbon and propylene glycol, re
covering the hydrocarbon and propylene glycol
glycol into the mixture and distilling o? a dode
from the azeotrope, washing the distillation resi
cane-propylene glycol azeotrope.
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due with water to remove propylene glycol there
16. A process for separating dodecane from
from, and purifying the residual alcohols by dis- -30 mixture with alcohols having 8 or more carbon
atoms per molecule which comprises introducing
tillation.
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10. A process for separating normal aliphatic
propylene glycol with the mixture and distilling
off a propylene glycol-dodecane azeotrope.
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hydrocarbons,- having 12 to 14 carbon atoms per
carbon-alcohol mixture, distilling v01f an azeo
molecule, from normal aliphatic alcohols having
17. In a process for separating tetradecane from
mixtures containing tetradecane and n-decyl al
prises introducing into such hydrocarbon-alcohol
cohol, the steps which comprise effecting a ratio
of 0.2 to 2.0 parts of propylene glycol per part
mixture propylene glycol in quantity equivalent to
from 0.2 to 20 parts per part of hydrocarbon
of tetradecane, distilling o? an azeotrope of tetra
in the mixture, distilling o? an azeotrope of hy
decane and n-decyl alcohol,‘ recovering tetra
drocarbon and propylene glycol, and recovering 40 decane and propylene glycol from the azeotrope,
the hydrocarbon and propylene glycol from the
and treating the distillation residue with water to
8 to 18 carbon atoms per molecule which come .
' azeotrope.
free it of propylene glycol.
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11. A process for removing normal aliphatic
18. In a process for separating tetradecane from
hydrocarbons, having 12 to 14 carbon atoms per
mixtures containing tetradecane and n-decyl ‘al
molecule, from admixture with normal aliphatic 45 cohol, the steps which comprise introducing pro-'
pylene glycol into the mixture, and distilling off
alcohols having 8 to 18 carbon atoms per mole
a tetradecane-propylene glycol azeotrope.
cule, the step which comprises introducing into
such hydrocarbon-alcohol mixture propylene gly
19.3A process for separating tetradecane from 7
mixture with alcohols having 8 or more carbon
col in quantity equivalent to from 0.2 to 20 parts
per part of hydrocarbon in the mixture, and 50 atoms per molecules which comprises introduc
ing propylene glycol with the mixture and dis
distilling off an azeotrope of hydrocarbon and
tillisng off a propylene glycol-tetradecane azeo
propylene glycol.
12. A process for manufacturing products of
20. A process for separation of hydrocarbons;
increased alcohol content from mixtures contain
.ing non-cyclic hydrocarbons and non-cyclic al 65 from mixture with alcohol-containing products
obtained by hydrogenation of coconut oil acids,
cohols having 8 to 18 carbon atoms per molecule,
the steps ‘which comprise introducing propylene
such alcohols being di?icult or impractical to sep
glycol with the mixture distilling o? propylene
arate from the hydrocarbons by fractional dis
glycol-hydrocarbon azeotrope, and recovering the
tillation, the steps which” comprise introducing
into the mixture 0.2 to 20 parts of propylene 60 hydrocarbon fromthe upper layer of the azeo- '
trope.
glycol per part of hydrocarbon present, distilling
oif an azeotrope of hydrocarbon and propylene
glycol, recovering the hydrocarbon and propylene
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trope.
ERNEST P. JENSEN. '