GB494236A - Improvements in or relating to the manufacture of adiponitrile - Google Patents

Abstract

Adiponitrile is obtained by passing a gaseous mixture of ammonia and adipic acid, or a derivative thereof which will react with ammonia to form adipamide, over a dehydration catalyst at a temperature between 320-400 DEG C. and at such a rate that the time of contact of the reactants with the catalyst is between 1 and 10 seconds, preferably 5 seconds. For example, a stream of ammonia is passed at a measured rate through a preheater 2 at about 500 DEG C. and into a vaporizing chamber 5 maintained at about 325-350 DEG C. Adipic acid, molten, powdered or in solution, is fed in through inlet 6 and evaporated by the ammonia stream. The mixture is then swept over into the catalyst chamber 10 through a heated transfer line 8. This chamber is maintained at 325-350 DEG C. The <PICT:0494236/IV/1> products are passed through cooling coil 13 and into separators 14. The oil layers are removed through outlets 15 and distilled to obtain pure adiponitrile. The aqueous layers are extracted to recover dissolved nitrile. Ammonia-acid molecular ratios of 4 : 1 to 24 : 1, preferably 6 : 1 to 16 : 1, are employed. Suitable catalysts are selected from the oxides and salts of elements of the 4th, 5th, 6th, 7th, and 8th groups, e.g. the dehydrating oxides of aluminium, silicon, tungsten, titanium, or molybdenum, preferably in the form of hard non-porous gels. Phosphoric, phosphotungstic and phosphomolybdic acids may also be used, preferably on supports, e.g. pumice, silica gel or kieselguhr. Other catalysts or promoters may be added, and spent catalysts may be revived by treatment with oxygen-containing gases. The preferred catalyst is silica gel. The apparatus should preferably be made of or lined with nickel, aluminium or its alloys, stainless steel containing molybdenum or copper-silicon-manganese alloys. A thin layer of carbonaceous material deposited on the metallic surface minimizes corrosion and adverse effects on the reaction. Other derivatives of adipic acid which may be used include adipamide, adipimide, adipic esters, o -cyanovaleric acid, adipamic acid and o -cyanovaleramide. Ordinary, increased or reduced pressure may be used. Examples describe the reaction between ammonia and adipic acid or adipamide, using ammonia-acid ratios of 16 : 1 and 8 : 1 and a silica gel catalyst and contact times of 5, 3,2, and 5,9 seconds. The product contains also cyclopentanone and tarry residue.