GB427631A - Improvements in and relating to the manufacture of organic acids from aldehydes and primary alcohols - Google Patents

Abstract

Organic acids are produced by treating a mixture of the vapour of an aldehyde or alcohol and at least an equal volume of steam with a dehydrogenation catalyst mixed with a partially hydrolyzable organic salt of an amphoteric base or magnesium with an organic acid. The aldehyde combines with water to form an aldehydrol which reacts with the basic salt of the organic acid to form a salt which is dehydrogenated to the normal salt, and this by hydrolysis yields the free acid and the basic salt. The dehydrogenation catalyst may be copper, silver, cobalt, zinc, palladium, or the platinum metals; the basic salt may be a salt of copper, beryllium, magnesium, zinc, aluminium, gallium, lanthanum, the yttrium metals, zirconium, cerium, the cerium metals, chromium uranium, manganese, iron, cobalt and nickel. Hydration catalysts may be added in small quantity, such as the oxides, borates or phosphates of thorium, vanadium, tungsten, molybdenum, and uranium, but an inert siliceous support in itself possesses hydrative effect and when used these additions may be omitted. The hydrogen liberated should be removed for instance by withdrawal through a permeable membrane or "thimble" which may be made of partially fused earthy material such as sillimanite or porous metals, and the withdrawal may be assisted by a vacuum pump. When an alcohol is used as initial material, it is first dehydrogenated to aldehyde by the action of the dehydrogenation catalyst. Small yields of acids may be obtained by starting with acetylene or ethylene and steam, an initial hydration to aldehyde or alcohol being first effected. The process may be effected at, below, or above atmospheric pressure. In examples: (1) pumice is shaken with washed hydroxides of copper, manganese, and chromium, dried in air and treated with a current of air or oxygen at 270--300 DEG C. and then with hydrogen; vapour of 20 per cent acetic acid is then passed through until at least half the maximum quantity of acid is bound; acetaldehyde and steam are then passed through at 250--280 DEG C.; (2) a catalyst is prepared as above from hydroxides of copper, manganese, and aluminium, ethyl alcohol and steam being passed over; (3) the catalyst of example 2 is modified by replacing the alumina by chromium hydroxide, the acid employed being propionic acid, and propyl alcohol and steam are passed through; (4) the catalyst is that employed in example 3, but in which benzoic acid has been used, and benzyl alcohol and steam are passed through. In each case the corresponding acid is obtained. The process is suitable for the production of formic acid from methyl alcohol.ALSO:Catalysts for the conversion of aldehydes or alcohols and steam into acids comprise a dehydrogenating catalyst such as copper, silver, cobalt, zinc, palladium and the platinum metals, mixed with a partially hydrolyzable organic salt of an amphoteric base or of magnesium. The basic salt may be a salt of copper, beryllium, magnesium, zinc, aluminium, gallium, lanthanum, the yttrium metals, zirconium, cerium, the cerium metals, chromium, uranium, manganese, iron, cobalt, and nickel. Hydration catalysts may be added in small quantity, such as the oxides, borates or phosphates of thorium, vanadium, tungsten, molybdenum, and uranium, but an inert siliceous support itself posseses hydrative effect and when used these additions may be omitted. In examples (1) pumice is shaken with washed hydroxides of copper, manganese, and chromium, dried in air, and treated with a stream of air or oxygen at 270--300 DEG C., and then with hydrogen; vapour of 20 per cent acetic acid is passed through until at least half of the maximum quantity of acid is bound; (2) the catalyst is prepared as above from the hydroxides of copper, manganese, and chromium; (3) and (4) the catalyst of Example 2 is modified by replacing the alumina by chromium hydroxide, the acid employed being propionic and benzoic acid respectively.