Catalyst and process for alkenyl-pyridine production

A catalyst comprising zinc oxide together with iron oxide, chromium oxide, and one or more of the compounds:- aluminium oxide, alkaline-earth metal oxides, and alkali metal oxides, hydroxides, and salts, is employed in the production of alkenyl pyridines from alkyl pyridines (see Group IV(b)). Preferably the catalyst contains a major proportion of zinc oxide. It may be composed of ZnO (40-90%), Fe2O3 (5-45%), CaO (1-20%), Al2O3 (1-15%), alkali metal oxide (0,5-10%), and Cr2O3 (0,2-5%). The catalyst may be prepared by mixing zinc and calcium oxides with hydroxides of aluminium, chromium, and iron, which have been coprecipitated from solutions of their sulphates by means of ammonia, adding concentrated caustic potash solution, and submitting the product to oven-drying until a consistency suitable for extrusion is obtained; the mass is extruded into rods which are then cut into small cylinders and dried at 700 DEG -750 DEG C. in a stream of nitrogen.ALSO:Alkenyl-pyridines are obtained by subjecting a heated vaporized mixture of an alkylpyridine and an inert gas or steam to dehydrogenation in the presence of a catalyst based on zinc oxide together with iron oxide, chromium oxide, and one or more of the following compounds:-aluminium oxide, alkaline-earth metal oxides, and oxides, hydroxides, and salts of alkali metals. Dehydrogenation may take place at 500 DEG -800 DEG C. The alkyl-pyridine may be 2-ethyl-, 3-ethyl-, 4-ethyl-, 2-methyl-5-ethyl-, 4-methyl-5-ethyl-, 2,4-diethyl-, 2,5-diethyl-, or 2-methyl-5-propylpyridine, or it may be a butyl-pyridine. The preferred catalyst preparations are those containing a major proportion of zinc oxide. In an example, a mixture of superheated steam and vaporized 2-methyl-5-ethyl pyridine is introduced into a reactor tube and passed over a catalyst containing ZnO (80%), Fe2O3 (18%), K2O (1.2%), and Cr2O3 (0.8%); the dehydrogenation temperature is 580 DEG C. in a first test and 600 DEG C. in a second test. The effluent vapours are condensed and methyl-vinyl-pyridine is recovered from the condensate. Pyridine, picolines, 3-ethyl pyridine, and 2,5-dimethyl pyridine are obtained as byproducts. Other examples describe the use of catalysts containing calcium oxide together with the oxides of zinc, iron, chromium, and potassium, and the dehydrogenation of 4-ethyl-pyridine, and 4-methyl-5-ethyl pyridine.