Preparation of cyclic anhydrides of aromatic dicarboxylic acids

Claim 1

PROCESS OF PREPARING A CYCLIC ANHYDRIDE OF AN AROMATIC DICARBOXYLIC ACID WHICH COMPRISES REACTING UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AT A TEMPERATURE OF AT LEAST ABOUT 250* C. A MONOHALOGENATED AROMATIC COMPOUND OF THE FORMULA R-X WHERE R IS A CARBOCYLIC AROMATIC RADICAL OF 1 TO 3 SIX-MEMBERED NUCLEI FREE FROM FUNCTIONAL GROUPS WHICH EVOLVE GAS IN THE ZEREWITINOFF TEST FOR ACTIVE HYDROGEN, AND X IS A HALOGEN OF ATOMIC NUMBER BETWEEN 17 AND 53 DIRECTLY ATTACHED TO ANNULAR CARBON OF AN AROMATIC RING, SAID ANNULAR CORBON BEING ADJACENT TO AN UNSUBSTITUTED ANNULAR CARBON OF SAID AROMATIC RING, WITH CARBON MONOXIDE AND, IN AN AMOUNT CORRESPONDING TO AT LEAST ONE ATOM OF ALKALI METAL PER TWO MOLES OF SAID AROMATIC COMPOUND, A NORMAL ALKALI METAL SALT IN AN ACID FROM THE GROUP CONSISTING OF CARBONIC AND PHOSPHORIC ACIDS, IN THE PRESENCE OF NICKEL CARBONYL AS A CATALYST.