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Home , Cyanoacetylene

United States Patent Office Fazented Feb.3,979,424 26, 1963

2 Table I 3,079,424 Pike CESS FOR THE REPARATSN OF CYAN. Yield (perceit based on ACETYSLENE FRCS AND HYDER- R T Moe rati E. HCN) GEN CYANOE a- SP SEO E------Eawrence J. Krebaum, Texas City, Tex., assignor to No. C. CN:CH: A ES Cyano- Acrylo- (CN) Measante Chenaica Company, St. Louis, Mo., a corpo- acetylene nitrile ration of Delaware No. 33awing. Fied Oct. 24, 1960, Ser. No. 64,290 70 4:3, 5 : 0.36 4.3 38. 6 3 (Caimas. (C. 260-455.3) 85 4:1:7 0.38 3.6 3.2 6. The present invention relates to a new method for the 5.3: E. 5.5:5515:19: 835.3 33.6g 33.6: is 37 preparation of cyanoacetylene or propargyl nitrile. III SS 08: 83 : 3: 23 Cyanoacetylene, a chemical compound useful as a cyan ovinylating agent in the production of cyanovinyl mono mers, has heretofore been obtained from propiolic acid 15 It will be seen from the tabulated data that not only by converting the acid to the corresponding amide and is cyanoacetylene formed in good yields but , then dehydrating the latter with phosphorus penioxide. a valuable chemical of commerce, is also produced as is It has now been discovered that this interesting and re- . In view of the fact that it has recently been active compound can be prepared in a relatively simple determined that cyanogen will react with acetylene under manner directly from acetylene. 20 conditions similar to those in this process to yield cyano According to the invention, a mixture of acetylene and acetylene, the cyanogen made can be recycled to the re cyanide is reacted at a temperature within the action zone together with an increased amount of acetyl range from about 700 to about 1100° C. In the pre- ene to react therewith and thus produce greater amounts ferred embodiment of the process, a gaseous mixture of of cyanoacetylene by simultaneous occurrence of the acetylene and together with a diluent 25 two reactions. gas is continuously passed through a reaction zone heated Variations in procedure and reaction conditions from to reaction temperature at a rate such that the mixture those given in the example may be made without depart remains therein for the desired reaction period. The ing from the scope of the invention. For example, the gases issuing from the reaction zone are quenched as reaction may be carried out in a tubular reactor of Tapidly as possible and the cyanoacetylene is separated 30 quartz, porcelain, or any other refractory material which from the gases by condensation. The diluent gas is op- is non-catalytic and capable of withstanding the tempera tional and is used mainly to facilitate acetylene handling tures employed as well as in the silica reactor exempli because of the hazards connected therewith although fied. The gases can, if desired, be passed through a series it acts also to reduce any secondary reactions such as of reaction zones heated to reaction temperature, the mix polymerization, cracking, etc. 35 ture being cooled as it issues from each reactor to recover The invention is illustrated in the following example the cyanoacetylene and other reaction products there which, however, is not to be construed as limiting it in from. Unreacted feed materials and cyanogen can then any manner whatsoever. be recycled. While the reaction may be conducted at any tempera EXAMPLE 1. 40 ture in the range from 770° C. to 1100° C., the preferred temperatures for the reaction are those between 900° C. The experimental apparatus was comprised of a reactor and 1000 C, consisting of an empty "Wycor” (96% silica) tube hav- Reaction time, i.e., the time during which the reactant ing an effective length of 20 cm. disposed within a muffle mixture is maintained at reaction temperature in the furnace together with inlet and outlet manifolds, an HCN reaction zone, varies with the particular temperature em. vaporizer and accessory lines, a mixing chamber for the ployed. Generally, any decrease in temperature requires reactant gases, and a product gas receiver. Prior to a run, an increase in reaction time and convesely an increase in the system was warmed up while was passed temperature will necessitate a shorter reaction time. Re through it. Acetylene and HCN vapors were fed through 50 action times from about 0.05 second to about 2 seconds rotameters into the mixing chamber and then passed are satisfactory attemperatures in the range from 770c. through the reactor which had been heated to the desired to 1100° C. In the preferred temperaturer ange, reaction temperature. The effluent gas from the reactor was col- time may vary from about 1 second at 900 C. to about 0.1 second at 1000 C. lected in a heated receiver from which it was exhauste The pressure employed is preferably atmospheric but into a sample bomb. Reaction times in the reactor were 55 operation at either subatmospheric or superatmospheric varied by using tubes of various diameters, by changing pressures is feasil le. feed rates, or by adding argon as an inert diluent to the A wide range of reactant ratios can be employed. Mole reaction mixture. A series of runs was made following ratios of HCN to acetylene varying from 4:1 to 20:1 can this procedure under various conditions of temperature, be used. Preferred, however, for practical operation are reactant feed ratio, reaction time, etc. Gas Samples were 60 those in the highest end of the range, i.e., from 15:1 to obtained and analyzed by means of a mass spectrometer. 20:1. An excess of HCN appears to be desirable since Analyses were expressed on a nole percentage basis. it not only leads to better yields of cyanoacetylene but Conversions and yields calculated from the analytical also tends to reduce the formation of tar, soot and other data under the various conditions are recorded in Table I. degradative by-products. 8,079,424 3 4. Inert gaseous diluents as pointed out previously may be cyanide at a temperature within the range from about present in the reaction mixture and it is frequently de 900 C. to about 1000° C. for a period of time from sirable to eliminate hazards connected with acetylene to about 0.1 second to about 1 second while maintaining the employ diluents such as , , argon mole ratio of hydrogen cyanide to acetylene within the and the like in order to achieve the short reaction times range from about 15:1 to about 20:1, said acetylene being required. HCN is a practical diluent as well as a reactant. diluted in an amount up to about 99 mole percent of the Any amount of diluent can be employed with the mole acetylene charged with a gas which is inert under said fraction added being in the range from 0%-99% of the Teaction conditions. reaction mixture. 3. The process for producing cyanoacetylene which Recovery of the cyanoacetylene can be effected by low 0 consists essentially of passing a mixture of hydrogen cyan temerature condensation of the effluent gas mixture, fol ide and acetylene in a mole ratio within the range from lowed by fractional distillation of the liquid condensate in about 15:1 to about 20:1, said acetylene being diluted a conventional manner. Unreacted acetylene and hydro with an inert gas in an amount up to about 99 mole per gen cyanide can be recycled to the reaction zone if desired. cent of the acetylene charged of a gas which is inert What is claimed is: 5 under the reaction conditions employed, through an 1. The process for producing cyanoacetylene which empty tube maintained at a temperature from about 900 consists essentially of reacting acetylene and hydrogen C. to about 1000 C. at a rate such that the gas mixture cyanide at a temperature within the range from about is maintained at reaction temperature for a period from 770° C. to about 1100° C. for a period of time from about 0.1 second to about 1 second. about 0.05 to about 2 seconds while maintaining the mole ratio of hydrogen cyanide to acetylene within the References Cited in the file of this patent large range from about 4:1 to about 20:1. 2. The process for producing cyanoacetylene which UNITED STATES PATENTS consists essentially of reacting acetylene and hydrogen 2,847,448 Gabbett et al. ------Aug. 12, 1958