| 摘要 |
Catalysts for use in the production of vinyl cyanide from hydrocyanic acid and acetylene in vapour phase reaction (see Group IV), are prepared by heating a solid porous material impregnated with one or more alkali metal cyanides at a temperature of not lower than 500 DEG C. for at least one hour. If desired the catalyst may also include other alkali metal salts such as the carbonates and chlorides or alkali metal hydroxides. Examples of solid porous materials are vegetable charcoals, activated carbon and other solid carbonaceous materials, coke, alumina, silica and porcelain, refractory materials such as carbon and silica being preferred. The material may be impregnated by means of an aqueous solution or preferably, an anhydrous ammonia solution of the cyanide or by means of the molten anhydrous cyanide. Best results are obtained using equal weights of sodium and potassium cyanides, but lithium, caesium or rubidium cyanides or mixtures thereof may be used. The heat treatment is preferably carried out at temperatures of 600 DEG to 1200 DEG C. for a period of from 10 to 50 hours in an oxidizing, reducing, or inert atmosphere. When the porous material is of carbon or other oxidizable material the heating should be carried out in a closed system such as a retort. In examples, there is described the preparation of catalysts comprising granular wood charcoal impregnated with equal weights of sodium and potassium cyanides and heated at temperatures varying from 520 DEG to 900 DEG C. in different gas atmospheres.ALSO:A process for the production of vinyl cyanide includes the steps of heating a catalyst comprising a solid, porous material impregnated with one or more alkali metal cyanides, at a temperature not lower than approximately 500 DEG C. for at least one hour (see Group III) and subsequently bringing a gaseous mixture of hydrocyanic acid and acetylene into contact with the catalyst at an elevated temperature. Examples of solid porous materials which may be used are vegetable charcoals, activated carbon and other solid carbonaceous materials, coke, alumina, silica, and porcelain, refractory materials such as silica and carbon being preferred. The material may be impregnated by means of an aqueous solution of the alkali metal cyanide or by molten anhydrous cyanide, but preferably by means of an anhydrous liquid ammonia solution of the cyanide. For best results, a mixture of sodium and potassium cyanides are employed, but if desired there may also be present other alkali metal salts such as the carbonates or chlorides or the hydroxides. The impregnated catalyst is preferably heated at temperatures of 600 DEG to 1200 DEG C. for at least 10 hours in reducing, oxidising or inert gases. When the catalyst support is of carbon or other oxidisable material, the heating should be carried out in an enclosed system such as a retort. The hot catalyst may be used directly for the reaction of hydrocyanic acid and acetylene in the conventional manner without first cooling to below the desired reaction temperature. Examples describe the preparation of vinyl cyanide using a catalyst comprising granular wood charcoal impregnated with sodium and potassium cyanides in equal weights and heated at temperatures varying between 520 DEG and 900 DEG C. in different gas atmospheres and a comparison is made between the yields obtained using such a catalyst and those obtained using the same catalyst but without prior heat treatment thereof according to the invention. |
