GB847621A - Process for the manufacture of aliphatic dicarboxylic acids - Google Patents

Abstract

Aliphatic dicarboxylic acids are obtained by treating an aqueous solution or suspension of an alkali metal salt or alkaline earth metal salt of an aliphatic a -hydroxy- or a , a 1-dihydroxy dicarboxylic acid with hydrogen at an elevated temperature under superatmospheric pressure in the presence of a hydrogenation catalyst, e.g., Raney nickel or Raney cobalt. In the preferred procedure the catalyst is added to an aqueous solution or suspension of the alkali metal or alkaline earth metal salt and the mixture is treated with hydrogen at above 240 DEG C. and under a pressure of 100 to 300 atmospheres until no more hydrogen is absorbed. The catalyst is then filtered off and the filtrate acidified with sulphuric acid until a weakly acid reaction to Congo red is obtained and the whole is then extracted with ether. The lower fatty acids formed as by-products are removed from the ethereal extract and the dicarboxylic acids obtained in relatively pure state. Examples are given for the production of adipic acid from the calcium and sodium salts respectively of a , a 1-dihydroxyadipic acid and of glutaric acid from the sodium salt of a -hydroxy glutaric acid. Some valeric acid and tetrahydrofuran 2, 5-dicarboxylic acid are obtained as by-product in the example in which the calcium salt of a , a 1-dihydroxyadipic acid is used.