GB609059A - Improvements in or relating to the manufacture of alkyl pyridines - Google Patents

Abstract

Alkyl pyridines are produced by passing a vaporized aliphatic carbonyl compound of the formula R-CO-R1, where R is an alkyl or alkenyl group and R1 is hydrogen, alkyl or alkenyl, in admixture with a molal excess of ammonia, at a suitable conversion temperature, over a synthetic silica gel catalyst promoted with a minor proportion of alumina. Acetaldehyde or paraldehyde yields 2- and 4-methyl pyridines. Inert diluents such as methane, ethane or nitrogen may be present. Other carbonyl compounds specified are propionaldehyde, butyraldehyde, valeraldehyde, crotonic and tiglic aldehydes, acetone and methyl ethyl ketone. Suitable catalysts are prepared as described in U.S.A. Specifications 2,142,324 and 2,147,985. A hydrous silica gel is prepared from alkali silicate and acid, treated with an aluminium salt solution, washed and dried. The hydrous alumina which is adsorbed by the silica is generally not in excess of 10 per cent, usually 0.1-2 per cent by weight of the catalyst. Reaction conditions are generally within the ranges 500-1200 DEG F., pressure from atmospheric to 500 p.s.i., and contact time 0.1-5 secs. In examples, acetaldehyde and ammonia in 1 : 3 molar ratio are passed with nitrogen over a synthetic gel containing 1.5 per cent alumina and 98.5 per cent silica gel at 800-950 DEG F. and atmospheric pressure or 100 p.s.i. to yield 2- and 4-methyl pyridines and homologues.