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Патент USA US3069468

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United States Patent Otilice
1
3,,llb9?58
Patented Dec. 18, 1952
2
surprisingly 0:,8-dichloropropionitrile readily is dehydro~
chlorinated to yield amounts of from about 30 to about
65% of B-chloroacrylonitrile, based upon the weight of
a,,8—dichloropropionitt'ile starting material. In general,
Glenn
Frigate,
C. Morrison,
'ltepney Depot,
Newfoundland,
Conn” NHL,
torsandto Wesley
American
Cyanamitl Company, New ‘i’otlr, N. 1., a corporation
cracking temperatures of from about 475° C. to about
706° ‘C. are satisfactory and no particular advantage
is apparently seen to be derived from employing tem
of Maine
peratures above about 700° C. Preferably, however,
No Drawing. Filed .lan. 7, i960, ?ler. No. $59
pyrolysis temperatures of from about 550° C. to about
2 Claims. (Cl. 26tl-465.7)
10 650° C. are employed for optimum yield. While the
The present invention relates to B-chloroacrylonitrile.
thermal cracking of emit-diehloropropionitrile may be
More particularly, this invention relates to a novel method
accomplished merely by subjecting the same: to tempera
for the preparation of ,8-chloroacrylonitrile.
tures in excess of about 475° C. it is also within the
It is known that B-chloroacrylonitrile or Z-chloro-vinyl
scope of this invention to employ a catalyst, e.g., one
cyanide (Cl—Cl-l:CH-—CN) may possibly be obtained 15 of the weakly acidic or neutral absorbent types, in the
as a ‘by-product of the catalytic vapor phase chlorination
process but the use or" such catalysts is not absolutely
of acrylonitrile at temperatures between about 200° C.
necessary since the present pyrolysis procedure affords
and 550° C. However, since the principal product, oc
high yields of ,o-chloroacrylonitrile even Without the use
chlo-roacrylonitrile or l-chlorovinyl cyanide is only pro
of catalytic masses.
duced in an amount of about 40% based upon the re 20
The thermal cracking or pyrolysis may be carried out
acted acrylonitrile the process does not afford too suit
in any suitable pyrolytic reaction apparatus which will
able 2. method for the preparation of ,B-chloroacrylo
afford proper temperature control, for example, in a
nitrile.
'
heated tube.
Such a heated tube may be constructed
Another method which has been employed for the
of thermally resistant glass, quartz or the like. Pro~
preparation of ?-chloroacrylonitrile involves the reaction 25 longed preheating of the starting material, oa?-CllChlOI‘O
of acetylene with cyanogen chloride. The use of certain
propionitrile should be avoided. Otherwise, substantial
catalysts such ‘as cuprous chloride and alkali and alkaline
earth metal cyanides is preferred in such a method in
order to obtain somewhat better yields than those re
sulting merely from the reaction of cyanogen chloride
and acetylene in an inert solvent such as hexane.
in any event, however, neither known method for the
production of ?-chloroacrylonitrile may be considered to
be especially advantageous since the former method, at
amounts of a-cbloroacrylonitrile may be obtained.
It
' generally de rable to vent the hydrogen chloride lib
erated from the cracked a?-dicbloropropionitrile since
it‘ it is allowed to remain in contact with the ,B-chloro
acrylonitrile it may possibly cause regeneration of sale
dichloropropionitrile. Collection of the products may
be accomplished by any convenient and desirable means,
e.g., a series of ice traps and/or suitable solvent vessels.
best, affords only small yields of B-chloroacrylonitrile 35 it may sometimes be necessary to add an inhibitor or
while the latter process, although an improvement to
mild neutralizing agent to the product collection trap in
some degree over the former, nonetheless provides low
order to forestall or retard polymerization of the prod
yields and conversions.
ucts or regeneration of a,B-dichloropropionitrile. The
In view of t.e disadvantages of the methods of the
crude reaction mixture may be readily separated, e.g.,
prior art, the need has long existed for a simple process 40 by fractional distillation, to yield the desired ?-chloro
for the preparation of [3-chloro-acrylonitrile. The desira
acrylonitrile. Both a.-chloro-acrylonitrile which is also
bility of such a process has become more signi?cant
obtained ‘and may be recombined with hydrogen chloride
since ?-chloroacrylonitrile is particularly useful in the
to form a,/3~-dichloropropionitrile and unreacted u,?-di
formation of resinous and rubber like copclymers with
chloropropionitrile may be subsequently recycled through
LS-butadiene, acrylonitrile, styrene and other like ethyl
enically unsaturated compounds. Moreover, B—cl1loro
acrylonitrile may be readily hydrolyzed in a co-nven
the reactor.
The starting material, esp-(llchloropropionitrile, is
readily prepared by reaction of chlorine and acrylonitrile
tionsl procedure to produce ,d-chloroacrylic acid and may
be hydrogenated to yield B-chloropropionitrile which in
preferably in the presence of a solvent such a pyridine
at temperatures of from about 10° to about 50° C. Of
turn may ‘be dehydrochlorinated to acrylonitrile. Addi 50 course, other methods for the preparation or" 0c,?—dl
tional uses for ?-chloroacryloni ‘ile will also be readily
chloropropionitrile are well known and these include the
apparent to those skilled in the art.
reactions of chlorine and acrylonitrile at room tempera
it has now been discovered that B-chloroacrylonitrile
ture in the presence of liglt both in the presence of
may be readily prepared excellent yield by thermally
and in the absence of a solvent.
cracking a,,6-dichloropropicnitrile at certain preferred
Examples of preferred methods of practicing our in
temperature conditions. In accordance with the present
invention, ahoedichloropropionitrile, which is obtained as
a reaction product of acrylonitrile and chlorine, is sub
vention are set forth hereinafter but it is to be under
stood that the examples are merely illustrative and are
not to be construed as limiting the scope of this in
jected to temperatures in excess of 475° C. for a mini
mum period of actual contact time. The resultant B
vention.
chioroacrylonitrile is then easily distilled or otherwise
separated from the crude reaction mixture. As a result
of our simple expeditious process B-chloroacrylonitrile
is obtained in markedly improved yield as compared
with that of prior art processes and is substantially free
of contaminating by-products resulting from the pyrolysis
rocedure.
The temperature at which mld-dichloropropionitrile is
pyrolyzed is critical only insofar as it should be at
least 475° C.
Example 1
into a bo-rosilicate glass tube (42 mm. x 40 cm.)
maintained at a. temperature of 605° C. is ted 3880
grams of a,,G-dichloropropicnitrile at the rate of 130
grams/hour.‘ The liquid products are collected in a
trap at 25° C. and the gaseous materials such as hydrogen
chloride are vented to the atmosphere. Vapor phase
chromatographic analysis shows the ratio of materials
in the crude product to be: B-chloroacrylonitrile: 63; ot
Below 475° C., only relatively small 70 chloroacrilonitrile: 31; w?-dichloropropionitrile: 5.
The ratio of ?-chloroacrylonitrile to a-chloroacrylonitrile
amounts of ?chloroacrylonitrile are produced. How
ever, at thermal cracking temperatures above 475° C.
is thus 2.0/
On distillation there is isolated 920
A,
3
propionitrile at a temperature in excess of about 475°
grams (33%) ,B-chloroacrylonitrile B.P. 117—l44° C. and
405 grams (15%) of u-chloroacrylonitrile Bl). 87—90° C.
The procedure of Example I is followed and results
C. and recovering ,B-chloroacrylonitrile.
2. A method for preparing ?-chloroacrylonitrile which
consists essentially of heating a,,8-dichloropropionitrile
obtained in the various runs wherein different conditions
are employed appear in the following table:
to a temperature within the range of from about 475°
a, B-Dichloropropionitrilc iced
Example
Size of reactor
2.
28 mm.><30 cm...
l
Vapor phase chromatographic
analysis of crude product
Reactor
Rate of
Contact
Grams temp, ° 0. feed, grams/ time, Sec-s.
hour
75
75
75
75
75
400
400
400
400
400
465
495
525
555
575
590
600
620
27
8
8
8
13
130
160
130
195
15
42
44
46
31)
21
17
21
20
From the results ‘appearing in the examples herein
above it will be observed that when the pyrolysis of “,5
dichloropropiouitrile is conducted within the preferred
critical temperature ranges, the ratio of fi-chloroacrylo
nitrile to a-chloroacrylonitrile varies from about 1.3 to 25
about 2.0 of the B-compound to 1.0 of the OL-COmPQllnd
Below temperatures of about 475° 0., however, on
chloroacrylonitrile is preferentially obtained. Thus, the
thermal cracking of a,?-dichloropropionitrile affords ‘an
easy method for production of B-c‘nloroacrylonitrile in
yields hitherto not considered possible.
We claim:
1. A method for preparing B-chloroacrylonitrile which
consists essentially of thermally crackling a,?-dichloro
B-Chloroacrylonitrile
21
30
52
56
59
60
64
6O
62
Ratio of B
chloroacry
lonitrile to
a-Chloro- a,?-Dichlo- a-chloroaery
acryloni- ropropiolonitrile in
trile
nitrile
product
27
32
39
38
37
33
32
34
35
44
37
9
7
4
7
5
3
3
.8/1. 0
.9/1. 0
1.3/1.0
1.5/1.0
1. 6/1. 0
1.8/1. 0
2.0/1.0
1.8/1.0
1.8/1.0
C. to about 700° C., condensing the products obtained
thereby and frac-tionating said products to separate 5
chloroacrylonitrile.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,231,363
2,298,739
2,437,998
Long _______________ __ Feb. 11, 1941
Lichty et al ___________ .._ Get. 13, 1942
Cliiford et al _________ __ Mar. 16. 1948
OTHER REFERENCES
Brintzinger et aL: Angew. Chem., A60, pages 311-621
(1948).
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