Purification of recirculated stream for isophthalic acid production

Claim 1

IN THE METHOD IN WHICH ISOPHTHALIC ACID IS PREPARED IN A REACTION ZONE BY THE OXIDATION OF METAL XYLENE IN ASOLVENT CONTAINING A SOLUBLE COBALT CATALYST, AND IN WHICH METHOD A STREAM OF SOLVENT CONTAINING DISSOLVED CATALYST IS RECIRCULATED TO THE REACTION ZONE AFTER APPROPIATE PURIFICATION OF THE RECIRCULATED STREAM, THE IMPROVEMENT WICH INCLUDES THE STEPS OF: A. PROVIDING IN THE REACTIO ZONE ACETIC ACID SOLVENT AND COBALT ACETATE CATALYST AND SUPPLYING TO SUCH REACTION ZONE OXYGEN AND METAL XYLENE, SAID METAL XYLENE CONTAINING A SMALL AMOUNT OF ORTHOXYLENE, OXIDIZING META XYLENE TO ISOPHTHALIC ACID AND WITHDRAWING APRODUCT STREAM COMPRISING ISOPHTHALIC ACID, ACETIC ACID, COBALT ACETATE, SECONDARY PRODUCTS, CONTAMINANTS COMPRISING ORTHOPHTHALIC ACID, ORGANIC ACIDS, AND OTHER COMPONENTS, B. SEPARATING ISOPHTHALIC ACID FROM SAID PRODUCT STREAM TO PROVIDE A DEPLETED STREAM FROM WHICH THE ISOPHTHALIC ACID HAS BEEN SUBSTANTIALLY COMPLETELY DEPLETED, C. SUBJECTING AT LEAST A PORTION OF THE DEPLETED STREAM TO FLASH DISTILLATION TO STRIP THEREFROM A SUBSTANTIAL PORTION OF THE ACETIC ACID, WATER, AND VOLATILLIZABLE CONPONENTS AS AN OVERHEAD STREAM AND TO PROVIDE A STREAM OF STRIPPED BOTTOM SOLUTIO CONTAINING ACETIC ACID, WATER COBALT ACETATE, COBALT ORTHOPHTHALATE, ORTHOPHTHALIC ACID, ORHER ORGANIC ACIDS, AND OTHER COMPONENTS, D. DIRECTING THE STRIPED-BOTTOMS STREAM TO A PRECIPITATION ZONE FOR TREATMENT FOR A PERIOD OF ABOUT 0.5 HOURS LESS AT A TEMPERATURE OF AT LEAST ABOUT 75*C. WITH A AQUEOUS SOLUTION CONTAINING ABOUT 5 WEIGHT PER CENT SODIUM CARHONATE, THE FINAL AMOUNT OF SLDIUM CARBONATE BEING AT LEAST 10% IN EXCESS OF THE STOICHIOMETRIC AMOUNT NECESSARY TO REACT WITH ALL OF THE ACID ANIONS IN THE STRIPPED BOTTOM SOLUTION TO FORM A SOLUTION CONTAINING SODIUM ACETATE, SODIUM ORTHOPHTHALATE, OTHER SODIUM SALTS, AND OTHER CIMPONENTS, SAID SOLUTION CONTAINING A DISPERSION OF A PRECIPITATE COMPRISING COBALT CARBONATE, SAID PRECIPITATE BEING FREE FROM AROMATIC ACIDS, E. RECOVERING THE PRECIPITATE FROM THE TREATED MIXTURE BY FILTRATION TO PROVIDE A FILTRATE CONTAINING ALL OF THE ORTHOPHTHALIC ION FROM THE STRIPPED BOTTOMS SOLUTON AND CONTAINING OTHER COMPONENTS DERIVED FROM THE STRIPPED BOTTOMS SOLUTION, F. WASHING THE PREIPITATE COMPRISING COBALT CARBONATE WITH WATER TO REMOVE WATER SOLUBLE COMPONENTS COMPRISING SODIUM SALTS, G. TRASFERRING THE WASHING PRECIPITATE TO A CATALYST REGENERATION ZONE IN WHICH THE PRECIPITATE COMPRISING CLBAT CARBONATE IS CONVERTED TO CATALYTICALLY ACTIVE COBALT ACETATE BY REACTION OF THE PRECIPTATE WITH A STREAM OF ACETIC ACID, THE THUS PREPARED SOLUTION OF COBALT ACETATE IN A ACETIC ACID BEING COMPLELY FREE FROM CATALYTICALLY POISONOUS QUANTITIES OF ORTHOPHTALIC ACID, H. PREPARING A SOLUTION OF COBALT ACETATE IN PARTIALLY DRIED ACETIC ACID SUITABLE FOR RECYCLING BY REMOVAL OF WATER FROM AT LEAST A PORTION OF THE DEPLETED STREAM OR STREAMS DERIVED FROM THE DEPLETED STREAM, SAID RECYCLED SOLUTION OF PARTIALLY DRIED ACETIC ACID CONTAINING ALL OF THE COBALT ACETATE OF STEP (G), AND CHARGING THE RECIRCULATED SOLUTION OF CATALYTICALLY ACTIVE COBALT ACCETATE IN PARTIALLY DRIED ACETIC ACID TO THE REACTION OF STEP (A).