Process for carboxylation of naphthoic acid to naphthalene dicarboxylic acid

A two step process for increasing the yield of a desired aromatic dicarboxylic acid which comprises:

• a) selectively carboxylating an aromatic mono-acid by the steps of:
• mixing an aromatic monoacid with excess base to form a solid salt;
• drying said salt;
• and
• reacting said salt in the presence of a catalyst selected from an oxide of a metal of Group IB, IIB, or IIIA of the Periodic Table at a temperature above about 350° C. to produce an intermediate containing an isomer of the desired aromatic dicarboxylic acid, the isomer containing a carboxyl group contributed by the base;
• and subsequently
• b) reacting said intermediate in the presence of a disproportionation catalyst at a temperature above about 420° C. to form the desired aromatic dicarboxylic acid.