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Патент USA US2411106

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Patented Nov. 12, 1946
UNITED sTÀTEs 'PATENT >01u-‘lcs
SEPARATION 0F STYRENE
ETHYL
BY` AZEOTROPIC DISTILLA
- Theodor A. Petry, Wenonah, and Grady LfPayne,
Clarksboro, N. J., assignors to Socony-Vacuum
Oil Company, Incorporated,l a corporation of
New York
Application July 1, 1942, serial Nc. 449,358
5 Claims.
1
(c1. ,2oz-_42)
i
single‘diagrammatic iigure of the drawing at
This invention has to do with the separation of
styrene in relatively pure form from crude mix
tures containing the same.
~
tached
Styrene finds uses in the synthesis of a, number
of organic chemicals and polymerization prod
l ucts and is of particular interest in connection
with certain forms of synthetic rubber. For most
of these uses the styrene must be in a relatively
hereto.
_
y
,
.
The effect of the presence of ethyl Cellosolve
i
as a distillation assistant may be indicated by the
5 .
following operations conducted in batch at at
mospheric pressure. In each case the charge
mixture consisted‘of a mixture of 60% by weight
of ethyl benzene and 40% by weightrof styrene. «
\pure state and substantially without polymerized
c derivatives present.
In each case the distillations were conducted in
Crude styrene is normally 10 batch at atmospheric pressure employing a> frac
contaminated with appreciable quantities orma
terials of similar boiling points and fairly close
tionating column of about eleven theoretical
plates. #In the first case in the absence of the dis
ly related chemical' structure such as, for exam
~tillation- assistant, the recovery oi condensed
product commenced at a tower top temperature
ple, ethyl benzene. Upon this account and also
because of the readily polymerizable nature of 15 of 272° F. and the ,distillation was conducted until
styrene, its preparation in a requisite degree -of
50% of the still charge had been recovered’ as an
overhead product, at which time the tower top `
purity by ordinary distillation methods presents
considerable diiliculty. Relatively i complicated
temperature has risen to 279° E.; and the distil
lation was stopped because the material in the
and expensive methods are, therefore, frequent
ly employed for obtaining styrene of a high de 20 still became polymerized. The last 10% of the
gree of purity.
c
‘
material collected as overhead distillate was
92.5% ethyl benzene and 7.5% styrene and sty
This invention has for its principal object the
rene Awas present in all portions of the overhead
provision- of a method for the recovery of rela
product except the first 10% of the still charge
tively pure styrene from such crude styrene mix
tures with a minimum of difficulty and a mini 25 taken overhead. It will be `seen that from the
- mum of degradation of the styrene product itself.
This invention is based upon the discovery that
substantially pure styrene can be recovered read
ily- from crude styrene by simple distillation
methods conducted in the presence of a properly
selected distillation assistant. Such a distillation
assistant should be capable of forming constant
' boilingmixtures with styrene which are consid
erably higher boiling than those formed with the
usual contaminants present in crude styrene. In
general, among those distillation assistants
which may be used, it is preferable to use those
lmembers which permit of a similar separation by
r standpoint of recovering styrene, this distillation
was an absolute failure since practically all of
the styrene remained in the still and had become
polymerized at the time distillation was stopped.
30 In a second operation, the same mixture .of`
ethyl benzene and styrene was used, and the
same still was used except that the still charge
consisted of one part of the crude styrene mix
ture and one part vof ethyl Cellosolve. In this
case, distillation commenced at a _tower top tem
perature of 250° F. and a' total overhead of 79%
, by volume of the crude styrene charge (after sep
aration of distillation assistant) was recovered.
Of the overhead distillate, 40% was quite pure
water. In general, any polar compound boiling
within the range of 90° to 250° C., and preferably 40 ethyl benzene and the last 19% taken overhead
was unpolymerized styrene of 100% purity. The
one which is water soluble, can be used to eiïect
intermediate 20% of overhead product was a '
the separation. We have found that ethyl Cel
mixture of styrene and ethyl benzene in which
v losolve, (glycol mono-ethyl ether) is particular
the styrene wasl unpolymerized, which could be
‘y useful in this connection, is soluble in water
subjected tc- a second distillation with similar re
45
and can be separated readily from the various
coveries. The bottoms from this operation when
products of distillation. The amount of the dis
separated from distillation assistant were found
tillation assistant which will be added depends
_to be polymerizedf In these two experiments,upon the amount of contaminant present in the
which differed only in the presence of ethyl Cel
charge mixture and upon thenature vcf the dis 50 losolve in proper amount as a distillation assist
, tillatign assistant used. Usually the quantity of
ant, it was found that the presence of this dis
assistant required varies between 25% and 25,0%
tillation assistant enabled the recovery of_Á hal!
by volume of the contaminants in the crude
of the styrene present' in a pure state and of a
styrene.
l
.
further portion of the styrene present in an un
The process for theseparation is shown by the
polymeri'zed state still capable of recovery by
2,411,106 ‘
similar treatment, while in the absence or thev l
distillation assistant, no recovery of styrene «
could be made.
_
These operations do not, however, set forth Ithe
` preferred form of our process for the recovery of
styrene of high purity from such mixtures. The
polymerization of styrene is a matterof time and
~
ing a mixture containing crude styrene to distil
lation in the presence of glycol monoethyl ether
as a distillation assistant, recovering from said
distillation at least two fractions, one consisting
'of "substantially pure styrene and some of the
distillation assistant and the other consisting oi
a mixture of contaminants and distillation as»
sistant and separating the distillation assistant
from the styrene containing fraction.
temperature. We have- found 'that by conduct
ing a distillation at relatively reduced- pressure
2. That method o! `recovering relatively purev
and in the presense of a distillation assistant, dis 10
styrene from crude mixtures comprising styrene
tillation operations may be conducted for the re
and contaminants of similar boiling point, pri
covery of styrene in a high state of purity with
marily ethyl benzene, which consists of subject
out the loss of any styrene by polymerization.
ing a mixture containing crude styrene to dis
` For example, using the same crude styrene
mixture containing 40% by weight of styrene and 15 tillation in the presence'of glycol mono-ethyl
ether to the extent of not less than 25% by vol
60% by weight of ethyl benzene, adding an equal
ume of the crude styrene mixture, recovering
volume of ethyl Cellosolve, and distilling in a
from said distillation at least two fractions, one
batch distillation, at a pressure of 55 mm. of
consisting of substantially pure styrene and some
mercury at the top oi the fractionating column, .
using a fractionating‘ column containing the 20 of the distillation assistant and the other con
sisting of »a mixture of contaminants and distil
equivalent of 2'? theoretical fractionating plates,
it was found that the ilrst 51% taken overhead
was substantially pure ethyl benzene having a
‘refractive index oi 1.492 (Num.) compared to a
lation assistant and separating the distillation
assistant from the styrene containing fraction.
3. That method of recovering relatively pure
refractive index of 1.4958 for reagent grade ethyl 25 styrene from crude mixtures comprising styrene
and contaminants of similar boilingwpoint, pri
marily ethyl benzene, which consists of subject
. benzene, that the next«25% taken overhead in
this batch' distillation consisted of a mixture of
ethyl benzene and styrene -and that the re
ing a mixture containing crude styrene to distil
mainder of -the charge in the still at the 75%
lation under pressure substantially less than at- .
other‘words, by combination of reduced pressure,
and the use of a distillation assistant, of proper
sisting of substantially pure styrene and some
kind and proper amount, no styrene was de
graded by polymerization and over 50% of the
sisting of a mixture of contaminants and distil
lation assistant from the styrene conïtaining ,
recovered cut point was styrene having a refrac 30 mospheric in the presence of glycol mono-ethyl
ether as a distillation assistant, recovering from
tive index of 1.5461 (Num) against a refractive
said distillation at least two fractions, one con
index of 1.5457 for reagent grade styrene. In
, styrene present was directly recovered in a high
state of purity, the remainder being contained in
a mixturenot unlike the original charge. Ad~_
of the distillation assistant and the other con
fraction.
' 4. That method of recovering relatively purev
styrene from crude mixtures comprising styrene
ditionally, the method-of operation was an ex-` 40 and contaminantsofsimilar boiling point, pri
marily ethyl benzene, which consists of subject
ceedinglyl simple one involving the use only of
ing a mixture containing crude styrene to distil
materials capable of ready and eiïective separa
lation under pressure substantially less than"tion from the distillation products. It did not
atmospheric in the presence of glycol mono
involve the introduction into the distillation
products of anything of the nature of an ln 45 ethyl ether to the extent of not less than 25%
_ hibitor which might later require costly removal‘ _ by volume of the crude styrene mixture, recover-A
ing from said distillation at least two fractions,
or interfere with the further use of the styrene
one consisting of substantially pure styrene and
product.
`
some of the distillation assistant andthe other
‘ In its most eifective form, this process may be
consisting of a mixture of contaminants and dis
conducted as a continuous operation in a column
tillation assistant and separating the distillation ,
_ of high Iractionating eilìciency from which rela
assistant from the styrene containing fraction.
' 5. 'I'he process of recovering a concentrated
lation assistant may be withdrawn at the bottom
styrene fraction from a mixture thereof pri
and the contaminants together with distillation
assistant may be withdrawn at the` top, each 55 marily with ethyl benzene which comprises sub
jecting suchmixture to azeotropic distillation in
product to be freed of ldistillation assistant by
the presence of ethylene glycol mon’o-ethyl ether,
scrubbing with water. ’I'he distillation assistant
removing as the overhead from such distillation,
may then be removed from the water by dis
tillation and returned to the process as is usual y a binary azeotrope primarily of ethyl benzene
in such operations.
60 and the ethylene glycol mono-ethyl ether and
-tively pure styrene containing some of the distil- _
lWe claim:
-
_
,
i 1. That method of, recovering relatively pure
styrene from crude mixtures comprising styrene
and contaminants of similar boiling point, pri
marily ethyl benzene, which consists of subject
recovering the concentrated vstyrene fraction
from such distillation.
‘
-
'
THEODOR. A. PE'I'RY.
GRADY L. PAYNE.- -„ .
Certiñcate of Correction
Patent No. 2,411,106.
~
.
f
p
¢
THEODOR A. PETRY ET AL.
November 12, 194e.
_
_
It is hereby certified that errors appear in the printed specification of the above
numbered patent requiring correction as follows: Column 2,v line 18, for “has” read
had; column 3, line 24, for the' numeral “1.492” read 1.4962; and that the said Letters
Patent should be read with these corrections therein that the same may conform to
the record of the case in the Patent Office.
Signed and sealed this 25th day of February, A. D. 1947.
[uw]
LESLIE FRAZER,
‘
First Assistant Commissioner of Patents.
Disclaimer
2,411,106.--Theodor A. Petry, Wenonah, and Grady L. Payne, Clarksboro, N. J.
SEPARATION 0F STYRENE FROM ETHYL BENZENE BY AzEoTRoPIC DISTILLA
TION. Patent dated Nov. 12, 1946. Disclaimer ñled July 23, 1948, by the
assignee, Socony-Vacuum Oil Company, Incorporated.
Hereby enters this disclaimer to claims 1, 2, 3, 4, and 5. ‘
[Oficial Gazette August 17, 1.948.]
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