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Патент USA US2404163

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july 16, 1946.
2,404,163
E. L. CARPENTER ETALMETHOD OF REFINING CRUDE OLEFINIC NITRILES
Filed oci. 31; 1959
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3 Sheets-Sheet 1
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1NVENTOR5
ATTORNEY.
July 16, 1946.
E. L. CARPENTER ET Al.
METHOD OF REFINÍNG CRUDE OLEFINIC NITRILES
Filed Oct. 3l, 1939 '
2,404,163
3 Sheets-Sheet 2
F/G.2.
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July 16, 1946.
E. L. CARPENTER E1-A_L
2,404,163
METHOD 0F RE'FINING CRUDE OLEFINIC NITRILES
Filed ou. s1, 193s
s sheets-sheet s
ATTORNEY.
- ‘_ Patented
2,404,163
`16„ 1946
UNITED
o
-:iWÃE'IÍHOD.0F
s'rA'rss
REm'lNBÉEgRUDE-OLEFINIC
PATENT: ` ori-*ics
` o
Erwin L. Carpenter. Old Greenwich, Harold S. .
Davis, ~ Riverside, and Oscar F. Wiedeman,
Stamford, Conn., assignors to American Cyan
amid Company, New York, N. Y., a corporation v
of Maine
' Application October 31, 1939, Serial' No. 302,072 ,
13 Claims.
l
(Cl. 20E-42)
.
.
2
l
The present invention relates to the refining of
by the dehydration of ethylene cyanohydrin, is
crude oletlnic nitriles, that is, those nitriles which
permitted to separate into two layers. The lower
may be hydrolyzed to oleñnlc acids.
layer of water containingfrom 5 'to 8% of acryl
'I'he dehydration of an alkylene cyanohydrin
onitrile is withdrawn and shaken with about twice
yields equi-molecular proportions of the corre 5 its volume of xylene. The mixture separates into
sponding olefinic nitrile and water, which may
two layers upon standing. The lower layer, being
be collected as two partially miscible layers.
principally water, isj withdrawn and discarded.
Upon separation, the upper layer is `found to be
The upper xylene layer containing the acryloni
predominantly nitrile containing some Water,
trile is united with the initial acrylonitrile layer
while the lower is predominantly water contain
containing from 4 to 5% water. The xylene dis
ing some nitrile.
„
places a small amount of water from the mixture.
This water layer is withdrawn and returned to
_an initial water layer containing some acryloni
For instance, in the production of acrylonitrile
from the dehydration of ethylene cyanohydrin,
the upper nitrile layer of the product is found to
trile.- The remaining layer of acrylonitrile, xyl
contain from‘4 to 5% of water whereas the lower
or water layer may contain from 5--8% of nitrile.
Therefore, in the manufacture of the olefinic
'nitriles, it is highly essential to have at hand a
method whereby the crude product can vbe refined
to a pure dry state.
ene and dissolved water is fractionated in a frac
tionating still operating with substantially total
reflux of the nitrile. 'I'he Water and nitrile form
an azeotropic mixture in the reflux column.
.Over a temperatureY range of from 70 to.75° C.`
this reñux mixture is condensed at the retlux
l
The principal object of the present invention
resides in a method of refining a crude olefinicv
nitrile wherein the product may -be readily ob'- l
tained free fromwater. Another important ob
ject is to provide an oleflnic nitrile in a pure state
by a method requiring only simple apparatuswith
high eillciencies.
'
'
l
The applicants have discovered that olefinic->
nitriles saturated with water, distill azeotropically
in such proportions that the .percentage by weight
of water in the distillate exceeds .the solubility
of water in the nitrile. and consequently the dis
tillate separates into two layers.Í Hencea largel «
’ proportion ofjthe water may be removed from
head and allowed to' stratify into two layers. The
upper nitrile layer flows -back into the still while
the lowerfwater layer is-Withdrawn and returned
to an initial water layer containing some acryloni
trile. A small amount of nitrilepolymer forms
during the fractionation. A fraction of wet
acrylonitrile is then removed from the still con
tent at a temperature of from 75 to 77° C. and
returnedto an initial acrylonitrile layer contain
ing water.` The dry acrylonitrile is fractionally
distilled from the still content at 77-78° C. The
still residue of polymer and xylene is ñlte'red
and the latter returned to the cycle.
As illustrated by the flow sheet of Fig.‘2, a nuan-v
the saturated solution by' placing a water sepa
rator in the head of a reflux column and con
tity of a crude olefinic nitrile such as. for exam
v ple, a crude product of acrylonitrile and water,
tinuously reñuxlng the solution. As the water is ì f produced‘asv above, is permitted to separate into
removed from the solution, the percentage of
vtwo layers. ‘ The lower layer of` waterfcontaining
-water in the distillate decreases and ilnally be- » l- from 5 to 8% of acrylonitrile is withdrawn‘zand
' comes _equal to the solubility of the'water _inthe ‘ol shaken with .about twice its volume of xylene.
nitrile.
At this point, the water' separator -in A vThe mixture upon standing separates into two
v the column is removed andthe >small portion f
layers. The lower layer being principally water
of water remaining in the- nitrile removed by 'l is withdrawnv and discarded. The acrylonitrile
distillation. This procedure has the advantage of . is removed from the upper xylene layer bydis
- reducing the -volume of the fore-runnings toa
tillation. .The _still residue of polymer and xylene
very considerable extent.
.
„
is illtered and the-'latterreturned to the cycle. f
f Referring to the accompanying drawings,
Fig. 1 .is a diagrammatic ilow sheetvof a pre
Thelnitial acrylonitrile layer containing from>
4 to 5% of water is fractionated in _a fractionat
ing still operating with substantially total reflux
50 of thev nitrile. `The water and nitrile form an
azeotropic mixture in _the reñux column. Over
- ferred method of> carrying out theinvention;
-ll'lg. 2 shows a modi?ed method, and
Fig. 3 illustrates still another alternative sys
i
.
tem.
.
A
.
As shown in Fig. l, afquantity of 'a crude oleflnic ,_ .
' nitrile. such as, for example, a crude product of
' acrylonitrile and water produced, for instance,
. aA temperature range of >from ,70 to 75° C. thisk
reilux mixture is condensed at the reñux head
and allowed to stratify'into two layers. The
uppernitrile layer is returned to the still while
1 2,404,163
.
3
the lower water layer is withdrawn and returned
to an initial'water layer containing some acrylo
nitrile. A small amount of nitrile polymer forms
«during the fractionation. The acrylonitrile from
the xylene extraction ‘of the initial water layer is
moving the lower water layer displaced by the
hydrocarbon solvent and returning the same to
a subsequently produced initial water layer con
taining nitrile, distilling the major portion of the
remaining water from the hydrocarbon solvent
added _to the still content. A fraction of ïwet
nitrile mixture and returning said water distil
acrylonitrile is then removed at a temperature
late to the above mentioned and subsequently
of -from 75 to 77°_ C. and returned to an initial
produced initial water layer containing nitrile,„
acrylonitrile layerl containing water. The dry
subsequently fractionally distilling a. wet nitrile
acrylonitrile is distilled from the polymer residue 10 fraction from the hydrocarbon solvent-nitrile
at a temperature of from 77 to 78° C.
\
mixture and returning said nitrile fraction to a
- In reiining a crude oleñnic nitrile such as,
subsequently produced initial nitrile layer con
for example, crude acrylonitrile, as illustrated by ' taining water, thereafter fractionally distilling
the ilow sheet of Fig. 3, the .crude product is al
the dry oleiinic nitrileffrom the hydrocarbon sol
lowed to separate into two layers. The lower
vent-polymer residue, ~separating the polymer and
layer of 'water containing some nitrile is with
hydrocarbon solvent, and returning -the latter to
drawn and discarded. The upper acrylonitrile
the .cycle for extraction of nitrile from a subse
layer containing some ,water is fractionated in a
quently produced and initial lower layer predom
fractionating still operating with substantiallyy
inantly water but containing some nitrile.
total reñux of the nitrile. The water _and acrylo 20 2. A method of refining crude acrylonitrile
nitrile form an azeotropic mixture in the reflux
containing water which comprises separating the
column. Over a temperature range of from 70
to'75° C. this mixture is condensed at the reflux
product into two layers, the upper of which is pre- i
dominantly acrylonitrile containing some water
while the lower layer is predominantly water con
head and allowed to stratify into two layers. The
upper nitrile layer flows back into the still while 25 taining same acrylonitrile, extracting the acrylo
the lower water layer is withdrawn and discarded.
nitrile from the said lower layer by means of
A fraction of wet acrylonitrile is then removed at
xylene, combining the xylene extract and upper
a temperature of from 75 to 77°C. and returned
acrylonitrile layer, permitting the mix to stratify.
to an initial acrylonitrile layer containing water.
removing the lower water layer displaced by the
" The dry acrylonitrile is distilled from the polymer 30 xylene> and returning the same to a subsequently residue at a temperaturev of from '77 to 78° C.
produced initial water layer containing acryloni
In employing theprocedure outlined by the flow
sheet of Fig. 3, a crude crotonic nitrile-water mix
ture, _produced for instance by the dehydration of
trile, distilling the major portion ofthe remain
ing water from Vthe xylene-acrylonitrile mixture
at a temperature of from 70 to 75° C., and re
propylene cyanohydrin, is` permitted to separate 35 turning the said water distillate to the above
into two layers. The lower layer of water con
taining some crotonic nitrile is withdrawn and
andy subsequently produced initial water layerl
containing acrylonitrile, subsequently fraction
discarded. The upper layer which is predomi
ally distilling awet acrylonitrilel fractionv from
nantly crotonic nitrile containing some water is
the xylene-acrylonitrile mixture at a tempera
dried by azeotropic distillation from a fractionat 40 ture of from 75 to '77? C., and returning said
ing still. The water and crotonic nitrile form
acrylonitrile fraction to a subsequently produced
an azeotropic mixture boiling ata temperature
yof about 85° C. which is condensed at the reflux
initial acrylonitrile layer containing water,
thereafter fractionally distilling the dry acrylo
head of the still and permitted'to stratify into
nitrile from the xylene-polymer residue at a
two layers. \The upper crotonic nitrile layer is re 45 temperature of from 77 to 78° C., separating the
turned to the still while the lower water layer is
polymer and'xylene and returning _the latter to >
removed and discarded. The cis- and trans-cro
the cycle for extraction of acrylonitrile from a
tonic nitrile isomers are thereafter fractionally
subsequently Iproduced and initial ylower layer
predominantly
distilled from the stillcontent at the tempera- .
tures of 107.5-108.5° C. and 119.0-120.5° C. re
spectively.
50
acrylonitrile.
water
_
but
containing
,
.
,
some
._
3. A method `of reilning a crude oleflnic nitrile
containing water which comprises separating the
`
Oleñnic nitrile solventswhich'are immiscible
with water, such as benzene, toluene, xylene and _ product into two layers, the upper of which is pre
the like are suitable for the extraction of the
dominantly nitrile containing some water while
oleiinic nitrile from the water layer.
55 the lower la'yer is predominantly water contain
Other members of the oleiinic nitrile series _in
ing some nitrile, extracting the nitrile from said
similar crude form maybe refined according `to
lower layer by means of a hydrocarbon solvent,
the method herein described, using appropriate
distilling the nitrile from the hydrocarbon solvent,
temperatures dependent upon the nitrile chosen.
separating the still residuev of polymer and hy
While the invention has been described with 60 drocarbon solvent and returning the latter to the
particular reference to specific embodiments,_it
cycle, distilling the major portion of "the water
from tlieinitially produced upper nitrile layer
and returning said` water distillate to a subse
is to be understood that it is not to be limited
thereto but is to be construed broadly and re
stricted solely by the scope of the appended
claims.
We claim:
"
_
quently produced initial water layer containing
65 nitrile, adding to the nitrile layer remaining from
1
_
yl. 'Avmethod of refining a crude oleñnic nitrile
containing' water which comprises separating the
product into two layers, -the upper of which ‘is
predominantly nitrile containing some water \
while the lower layer is predominantly water con
taining some nitrile, extracting the nitrile from
said lower layer by means of a hydrocarbon sol
vent, combining the solvent extract and upper
nitrile layer, permitting the mix to stratify, re 75
the major water removal step, the nitrile from the
hydrocarbon solvent extract to form a-nitrile mix
ture, subsequently fractionally distilling a wet
nitrile fraction from the said nitrile mixture and
returningsaid nitrile fraction to an initial nitrile
layer containing water, thereafter fractionally
distilling the dry oleiinic nitrile from the polymer
residue.
_
_
4. A method of refining crude acrylonitrile con
taining water which comprises separating the`
2,404,163
product into two layers, the upper of which is
predominantly acrylonitrile containing some
water while the lower layer is predominantly wa
ter containing some acrylonitrile, extracting the
acrylonitrile from the said lower layer by means
of xylene, distilling the acrylonitrile from the
xylene, separating the still residue of polymer and
xylene and returning the latter to the cycle, dis
tilling the major portion of the water from the
upper acrylonitrile layer at a temperature of from
'I0 to 75° C. and returning said water distillate to
a subsequently produced initial water layer con
taining acrylonitrile, adding to the remaining
acrylonitrile layer the acrylonitrile from the
xylene extract to form an acrylonitrile mixture,
subsequently fractionally distilling a. wet acrylo
nitrile fraction from the acrylonitrile mixture at
a temperature of from 75 to 77° C. and returning
said acrylonitrile fraction to an initial acrylo
layer, returning the wet nitrile layer to the distil
land for recycling and finally collecting the sub
stantially dehydrated nitrile.
9. A method of refining a crude acrylonitrile
containing water to remove water therefrom
which comprises distilling therefrom an azeo
tropic mixture of the acrylonitrile and water, con
densing the distillate, permitting the condensed
distillate to stratify into an upper wet acryloni
trile layer and a lower water layer, separating
off the water layer, returning the wet acryloni
trile layer to the distillandv for recycling and ñ- ~
nally collecting the substantially dehydrated
acrylonitrile.
10. A method of refining a crude crotonic ni
trile containing water to substantially dehydrate
the same which comprises distilling therefrom an
azeotropic mixture of the crotonic nitrile and wa
ter, condensing the distillate, permitting the con
nitrile layer containing water, thereafter frac 20 densed distillate to stratify into an upper wet
tionally distilling the dry acrylonitrile from the
crotonic nitrile layer and a lower water layer,
polymer residue at a temperature of from 77 to
separating olf the water’layer, returning the wet
'78° C.
-
5. A method of refining a crude oleñnic nitrile
crotonic nitrile layer to the distilland for re
cycling and finally collecting the substantially de- ,
containing water which comprises separating the 25 hydrated crotonic nitrile.
product into two layers, the upper of which is
11. In the method of refining a crude oleiinic
predominantly nitrile containing some water
nitrile vcontaining water to substantially dehy
while the lower layer is predominantly water con
drate the mixture, the process which comprises
taining some nitrile, distilling from the upper
placing the crude nitrile in a still provided withnitrile layer an azeotropic mixture of nitrile and 30 a fractionating column and a condenser, distilling
water, subsequently fractionally distilling a wet
an azeotropic mixture of nitrile and water from
nitrile fraction therefrom and returning the same
the crude nitrile, passing the vapor distillate
to a subsequently produced initial nitrile layer
through the fractionating column and into the
containing water, thereafter 4distilling the dry
condenser, condensing the distillate,-' allowing the
oleñnic nitrile from the polymer residue.
distillate t0 stratify into an upper nitrile layer
6. A method of refining crude acrylonitrile con
substantially saturated with water,A and a lower
taining water which comprises separating the
water layer, drawing oif the water layer, and re
product into two layers, the upper of which is
turning the wet nitrile to the fractionating col
predominantly acrylonitrile containing some wa
umn, and finally collecting the substantially de
ter while the lower layer is predominantly water 40 hydrated nitrile.
containing some acrylonitrile, distilling from the
12. In the method of refining a crude acrylorii
upper acrylonitrile layer an azeotropic mixture of
trile containing water to substantially dehydrate
acrylonitrile and water until the distillate tem
the mixture, the process which comprises placing
perature has risen from 70° C. to '75°> C., subse
the crude acrylonitrile in a still provided with a
quently fractionally distilling a wet acrylonitrile 45 fractionating column and a. condenser, distilling
fraction therefrom at a temperature of from
an azeotropic mixture of acrylonitrile and water
'l5-77° C. and returning the same to a subse
from the crude acrylonitrile, passing the vapor
quently produced initial acrylonitrile layer con
distillate through the fractionating column and
taining water, thereafter distilling the dry acrylo
into the condenser, condensing the distillate, al
nitrile from the polymer residue at a temperature 50 lowing the distillate to stratify into an upper
acrylonitrile layer substantially saturated with
of from 77 to '78° C.
'1. A method of refining crude crotonic nitrile
water, and a lower water layer, drawing ofi` the
containing water which comprises separating the
water layer, and returning the wet acrylonitrile
product into two layers, the upper of which is
to the fractionating column, and finally collecting
predominantly crotonic nitrile containing some 55 the substantially dehydrated acrylonitrile.
water while the lower layer is predominantly wa
13. In the method of refining a crude crotonic
ter containing some crotonic nitrile, distilling
nitrile 4containing water to substantially dehy
from the upper crotonic nitrile layer an azeotropic
drate the mixture, the yprocess which comprises
mixture of crotonic nitrile and Water until the
placing the crude crotonic nitrile in a still pro
crude crotonic nitrile is substantially dehydrated, 60 vided with a fractionating column and a con
subsequently distilling a wet crotonic nitrile frac
denser, distillìng an azeotropic mixture of crotonic
tion therefrom to remov.. the remaining Water
nitrile and water from the crude crotonic nitrile,
and returning this fraction to a subsequently pro
passing the vapor distillate through the frac
duced initial crotonic nitrile layer containing wa
tionating column and into the condenser, con
ter, and thereafter fractionally distilling the cis 65 densing the distillate, allowing the distillate to
and trans-crotonic nitrile isomers at the tempera
stratify into an upper crotonic nitrile layer sub
tures of 107.5-108.5° C. and 119.0-120.5° C. respec
stantially saturated with water, and a lower water
tively.
°
layer, drawing olf the water layer, and returning
8. A method of refining a crude oleñnic nitrile
the wet crotonic nitrile to the fractionating col
containing water to remove water therefrom 70 umn, and iinally collecting the substantially de
which comprises distilling therefrom an azeo
hydrated crotonic nitrile.
'
tropic mixture of the nitrile and water, condens
ing the distillate, permitting the condensed dis
tillate to stratify into an upper wet nitrile layer
and a lower water layer. separating et! the water 76
ERWIN L. CARPENTER.
HAaoLD s. DAVIS.
oscm F. Winsum/IAN.
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