Патент USA US3069468код для вставки
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).