Process for the preparation of cyclic dicarboxylic acids

Claim 1

IN A PROCESS FOR PREPARING AROMATIC CARBOXYLIC ACIDS, SAID CARBOXYLIC ACIDS CONTAINING TWO ACID GROUPS IN THE 1,4 POSITION ON THE AROMATIC NUCLEUS WHEREIN ONE OF SAID ACID GROUPS IS A CARBOXYL GROUP AND THE OTHER IS AN ACID GROUP SELECTED FROM THE GROUP CONSISTING OF CARBOXYL AND PHENOLIC HYDROXYL GROUP, BY HEATING ALKALI SALTS OF AROMATIC CARBOXYLIC ACIDS WHICH CONTAIN ACID GROUPS IN OTHER THAN THE 1,4 POSITION ON THE AROMATIC NUCLEUS WHEREIN ONE OF SAID ACID GROUPS IS A CARBOXYL GROUP AND THE OTHER IS AN ACID GROUP SELECTED FROM THE GROUP CONSISTING OF CARBOXYL AND PHENOLIC HYDROXYL GROUPS, UNDER CONDITIONS OF TEMPERATURE AND PRESSURE UNDER WHICH SAID SALTS ARE CON VERTED INTO ALKALI METAL SALTS OF THE CARBOXYLIC ACIDS TO BE PREPARED, THE IMPROVEMENT WHICH COMPRISES SEPARATING THE ACID PRODUCT AND RECOVERING THE ALKALI METAL VALUES IN A FORM DIRECTLY REUSABLE IN THE PROCESS BY THE STEPS COMPRISING DISSOLVING THE SALT OBTAINED FROM THE HEAT TREATMENT IN A SOLVENT SELECTED FROM THE GROUP CONSISTING OF WATER, LOWER ALIPHATIC ALCOHOLS, KETONES AND ETHERS, TREATING SAID SALTS IN SOLUTION WITH CARBON DIOXIDE, SEPARATING AT LEAST A MAJOR PART OF THE LIQUID FROM THE RESULTING SOLIDSLIQUID MIXTURE, TREATING THE RESULTING SOLIDS-LIQUID MIXTURE WITH AN AROMATIC CABOXYLIC ACID, THE SALTS OF WHICH HAVE SERVED AS STARTING MATERIALS, AND SEPARATING THE LIBERATED CARBOXYLIC ACID AS A SOLID FROM THE MIXTURE.