GB800847A - Process for the hydrogenation of aliphatic mono- and dicarboxylic acids - Google Patents

Abstract

A catalyst for the hydrogenation of aliphatic mono- and di-carboxylic acids and esters thereof comprises a Zn-Cu-Al alloy surface-etched with caustic alkali, the Zn content being 5-40 per cent and the Al and Cu contents each 30-60 per cent. The preferred composition is Zn20, Cu40, Al40. The catalyst is made by melting the constituents together in an inert atmosphere, grinding to any desired size from lumps to powder, and heating to 50-100 DEG C. with caustic soda or caustic potash solution for 10-120 minutes. The activated catalyst is then washed with water and another solvent (e.g. methanol) and dried away from air. The catalyst becomes inactive in use and can be regenerated 10-20 times by the same process as above. Examples are given of the preparation of typical catalysts.ALSO:Aliphatic mono- and di-hydric alcohols are made by hydrogenating saturated monocarboxylic acids of 2-18 carbon atoms or dicarboxylic acids of 2-12 carbon atoms, or esters thereof, at 180-350 DEG C. and 100-500 atmos. in the presence of a Zn-Cu-Al alloy surfaceetched with caustic alkali; the Zn content of the alloy is 5-40 per cent and the Al and Cu contents are each 30-60 per cent, the preferred composition being Zn 20, Cu 40, Al 40. The process may be intermittent or continuous, the latter employing the catalyst in lump form. The preheated acid or ester is dissolved in e.g. methanol, passed with hydrogen over the heated catalyst, and the gaseous products separated and recycled. If the catalyst is in powder form it is separated by filtration or centrifuging before the product solidifies. When the catalyst becomes inactive it can be re-etched with caustic alkali. The products may be converted into the corresponding chlorinated hydrocarbons. Examples show the hydrogenation of (1) dimethyl adipate to hexanol-1 and hexanediol-1 : 6; (2) adipic acid to hexanediol-1 : 6; (3) sebacic acid to decanol-1 and decanediol; (4) dimethyl pimelate to heptanediol-1 : 7; (5) dimethyl succinate to butanediol-1 : 4; (6) methyl stearate to stearyl alcohol and octadecane; (7) beef tallow to a fatty alcohol mixture.