GB806619A - A process for the preparation of unsaturated aliphatic alcohols - Google Patents

Abstract

Catalysts for use in the catalytic hydrogenation of unsaturated acids and their esters to the corresponding alcohols contain zinc with vanadium or chromium and, if desired, one or more other metals from Group II of the Periodic Table. Suitable catalysts are, for example, zinc - chromium, zinc - barium - chromium, zinc - cadmium - chromium, zinc - magnesium - chromium, zinc - vanadium, zinc-barium - chromium - cadmium, zinc - cadmium-vanadium, and zinc - cadmium - barium - vanadium. In the preparation of the catalysts, the chromium is put in as free chromic acid or chromate and the vanadium as free vanadic acid or vanadate. In the examples: (a) a zinc barium-chromium catalyst is prepared by reacting zinc oxide and barium oxide with chromic acid; the chromate mixture obtained is dried, heated in a furnace and reduced with hydrogen to the corresponding metals; (b) a zinc-chromium catalyst is formed by the process of (a) using zinc oxide and chromic acid; and (c) a zinc-vanadium catalyst is formed by the process of (a) using zinc oxide and vanadic acid.ALSO:A mono-unsaturated aliphatic alcohol is continuously prepared by the catalytic reduction of a free unsaturated fatty acid or its ester formed with a monohydroxy alcohol containing from 1 to 4 carbon atoms by passing the acid or ester with 50 to 500 times the quantity of hydrogen theoretically required for the reduction and 1 to 5 times the amount by volume, based on the volume of the starting material, of an alcohol containing from 1 to 4 carbon atoms over a large quantity of a zinc-containing catalyst which contains also vanadium or chromium and if desired one or more other metals from Group II of the Periodic Table, at a pressure above 100 atm. excess pressure and temperature in the range 250-350 DEG C. Suitable catalysts are, for example, zinc - chromium, zinc - barium - chromium, zinc - cadmium - chromium, zinc - magnesium - chromium, zinc - vanadium, zinc-barium - chromium - cadmium, zinc - cadmium vanadium and zinc-cadmium-barium-vanadium catalysts. Poly-unsaturated fatty acids or mixtures of such acids or their esters, such as linseed oil fatty acids, soya oil fatty acids or the methyl esters of the latter acids are converted by the process into mono-unsaturated alcohols. Since, however, the poly-unsaturated fatty acids or their esters are inclined to polymerize and consequently damage the hydrogenation catalyst it is advisable that these starting materials should be hardened under mild conditions up to an iodine value of 90 to 100 before the catalytic reduction. In the examples: (a) sperm oil fatty acid, methanol and hydrogen are passed continuously over a zinc-barium-chromium catalyst (obtained by reacting zinc oxide and barium oxide with chromic acid and reducing the resulting chromates with hydrogen to the corresponding metals) at 285 DEG C. and 250 atm. excess pressure to give a mixture of unsaturated fatty alcohols; (b) oleic acid, methanol and hydrogen are passed continuously over a zinc-barium-chromium catalyst at 280 DEG C. and 260 atm. excess pressure to give oleyl alcohol; (c) tallow fatty acid, butanol and hydrogen are passed continuously over a catalyst, prepared from zinc oxide and chromic acid, at 275 DEG C. and 260 atm. excess pressure to give a mixture of unsaturated fatty alcohols corresponding to tallow fatty acid; and (d) methyl esters of sperm oil fatty acids, methanol and hydrogen are passed continuously at 275 atm. excess pressure and 310 DEG C. over a catalyst prepared from zinc oxide and vanadic acid to give a mixture of unsaturated fatty alcohols corresponding to sperm oil fatty acids.