ES280114A1 - Procedure for the separation of cyclic dicarboxylic acids (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

"Process for the separation of cyclic dicarboxylic acids", which carry two acidic salt-forming groups, from mixtures such as especially originate in the thermal rearrangement of alkali salts of other cyclic carboxylic acids carried out at 250 to 450º C, pressures comprised between 1 and 30 atms, advantageously in the presence of catalysts, by acidification of the dissolved salt mixtures, optionally after filtering the resulting solution to isolate the catalyst, characterized in that an amount is added to the solution of cyclic monocarboxylic acids or acid salts of cyclic carboxylic acids, which must then be subjected to thermal rearrangement, at temperatures between 80 and 250º C, preferably between 100 and 180º C, that the pH of the mixture is between 4.5 and 6.5, the crystallized precipitate is separated at 20 to 30º C, this is suspended with water, and it is heated to temperatures of at least 115º C below the pressure that is formed every time, so much anhydride or free acid of the cyclic carboxylic acid is added to this suspension that it serves for the thermal transposition, that the pH of the mixture is between 2.1 and 4.5, the reaction mixture is cooled to 100 to 115º C and the crystallized cyclic carboxylic acid is removed. (Machine-translation by Google Translate, not legally binding)