Patented Nov. 12,1946 _ . } _ UNi'i‘ED STATES PATENT OFFHQE PRODUCTION or VINYL CYANIDE Charles R. Harris, Lockport, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application January 12, 194.4, \ I SerialNo. 518,013 '1 Claims. 1 This invention relates to the production of . (Gl. 260-464) , ‘ 2 . Example vinyl cyanide and has as its object a novel meth A vertical stainless steel tube provided with an od for producing this chemical. In accordance with my invention, I_ subject \ inlet at the top and an outlet at the bottom was succinonitrlle vapor to pyrolysis at a tempera- 5 arranged to be heated in an electric furnace.‘ A layer of small porcelain Raschig rings was ture within the range of about 300-‘700° 0., whereplaced in the bottom of the tube to serve as a by I have discovered that vinyl cyanide is formed support for any desired layer of catalyst. Above in good yield by the following reaction: _ the catalyst was placed a three-inch layer (75, cc.) of glass beads. When no catalyst was used, _, CNCECHQCN CBwHCN-I-HCN The reactionis endothermic, 10- the glass beads rested on the Raschig rings. A , thermocouple was provided for measuring the In a preferred mode of practicing my inven- temperature in the catalyst layer. tion, succinonitrile is heated to form vapor which In operation the tube was heated to an inside is passed through a heated reactor or passed over 15 temperature of 300 to 700° 0-, and a slow stream any suitable heated surface. If desired, a catof molten succlnonitrile was introduced in the I alytic surface may be used, for example, a, cartop of the tube onto the glass beads. The suc bonaceous material such as coke, charcoal‘ or ‘ einonitrile was rapidly vaporized on contact with activated carbon, or alumina, silica gel or the the hot glass beads, and the vapors were immedi like. I have also found that alkali metal cy- 2o ately Subjected to the pyrolyzing temperature. anides act as catalysts‘ for the reaction. These The suceinenitrile vapors were diluted with by may be supported on granular, infusible solids drogen which was introduced in the to!) 0f the such as charcoal or the other solid materials mentioned above. For this purposeI may use the reaction tube, above the glass beads. In a series -0f runs the following catalysts were used: cyanides of sodium, potassium, lithium, cesium, 25 or rubidium, or mixtures thereof. Preferably, Run Catalyst I use a mixture of sodium and potassium cyanide containing not less than 10% of either one. Also I prefer to carry out the pyrolysis reaction at a ’ A ------ -- 300 cc. Melamine pellets. B """ " 30210:gtgfgou?ilgggeugiggiliglrggggdegovggggcgggght temperature between the melting point of the 30 G ______ __ 75 cc. of 4-8 mesh size wood charcoal impregnated with about 15% by weight of a 50-50 mixture of sodium and cyanide or cyanide mixture and about 700° C. I potassium cyanides. have obtained my best results by using glowed wood charcoal which has been impregnated with an alkali metal cyanide. 12.5 cc. of the catalyst ofrun 0. it; cc. of wood charcoal, 4-8 mesh size. _ one. ~ However, excellent yields may be obtained without the use of any catalyst, especially “at temperatures of 500-650° 0. Some formation of \ Do. ' 150 cc. of the catalyst of run 0. The following results were obtained: - ‘vinyl cyanide will occur when the succinonitrile is pyrolyzed at temperatures as low as 300° 0., but ; below this temperature the yield becomes too low 40 Run giffligglgt' _ summon. Kigali“ tegelfgaiggm to be of commercial importance. I prefer not to exceed a temperature of about 700° C. to avoid excessive, undesired decomposition reactions. I prefer to carry out the reaction in‘tlie presence of an inert diluent gas such as h drogen or nitrogen. Such gas may be mixed with suc- . era/mm. 232 315 cinonitrile vapors and the vapor-gas mixture. subjected to the pyrolyzing temperature, or the gas may be separately introduced into the reac tion space. The amount of‘ diluent gas may be 60 varied over a‘ Wide range- 9- g" from 10% to 90% 63%‘; vinylcyanide' 315 Cumin. ° 0. Percent - i;% gag ‘33;; 1:00) 6% 525 Mg 3%, 1,% W58 23.2 None 550.590 72:9 16mm. l. A process for the production of vinyl cy by Wlume °f the vamr‘ga‘s mixture' ordmm'?yanlde which comprises subjecting succinonitrile 8' mixture of about 50% (1111161115 8&8 is Preferredvapor to pyrolysis at a temperature of about 300 The following example further illustrates my 55 to 700" c. in the presence of a catalyst compris invention: in: an alkali metal cyanide on a solid support. 2,410,820 3 2. A process for the production or vinyl cy anide which comprises subjecting succinonitrile vapor to pyrolysis at a temperature of about 300 to 700° C. in the presence of a catalyst compris ing charcoal impregnated with at least one alkali metal cyanide. ‘ 4 5. A process for the production or vinyl cy anide which comprises subjecting succinonitrile vapor together with an inert gas to pyrolysis at a temperature or about 300° C. to 700° C. in the presence or a catalyst comprising an alkali metal cyanide on a solid support. 6. A process for the production or vinyl cy 3. A process for the production of vinyl cy anide which comprises subjecting succinonitrile anide which comprises subjecting succinonitrile vapor together with hydrogen to pyrolysis at 'a vapor to pyrolysis in the presence of a catalyst comprising a. carbonaceous support impregnated 10 temperature or about 300° C. to 700° C. in the presence of a catalyst comprising an alkali metal with at least one alkali metal cyanide at a tem cyanide on a solid support. perature within the range of about 300 to 700° C. '7. A process for the production of vinyl cy-' which is above the melting point of said cyanide. anide which comprises subjecting succinonitrile 4. A process for the production of vinyl cy anide which comprises subjecting succinonitrile 15 vapor together with hydrogen to pyrolysis at a temperature 01' about 500° C. to 650° C. in the vapor to pyrolysis in the presence or a catalyst presence of a catalyst comprising an alkali metal comprising charcoal impregnated with a mixture cyanide on a solid support. _ of sodium and potassium cyanides at a tempera ture within the range or 500 to 650° C. which is CHARLES R. HARRIS. above the melting point of said mixture.