Process for the preparation of cyclic dicarboxylic acids

Claim 1

A PROCESS FOR PREPARING SYMMETRICAL AROMATIC DICARBOXYLIC ACIDS WHICH COMPRISES THE STEPS OF FORMING A STARTING SALT OF A NON-SYMMETRICAL AROMATIC CABOXYLIC ACID BY REACTING A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NON-SYMMETRICAL AROMATIC CARBOXYLIC ACIDS AND THEIR ANHYDRIDES WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A MIXTURE OF DIFFERENT ALKALI METAL HYDROXIDES, CARBONATES AND OXALATES SAID MIXTURE CONTAINING FROM ABOUT 10 TO 70% OF A SODIUM COMPOUND, HEATING SaID FORMED ALKALI METAL SALTS IN THE PRESENCE OF A CATALYST CONTAINING A METAL SELECTED FROM THE GROUP CONSISTING OF CADINUM, ZINC AND BIVALENT IRON, IN AN INERT ATMOSPHERE AND AT A TEMPERATURE BETWEEN 340*C. AND A TEMPERATURE AT WHICH THE STARTING SALTS WILL SUBSTANTIALLY DECOMPOSE, WHEREBY SAID STARTING SALTS ARE CONVERTED INTO THE CORRESPONDING SALTS OF THE SYMMETRICAL AROMATIC CARBOXYLIC ACID TO BE PREPARED, AND LIBERATING THE FREE SYMMETRICAL AROMATIC DICARBOXYLIC ACID FROM THE PRODUCT MIXTURE BY ACIDIFICATION.