Method of making halophthalic acids and halophthalic anhydrides

A method of preparing a halophthalic anhydride, said method comprising the steps of:

• Step (A) contacting in a liquid phase reaction mixture at least one halogen-substituted ortho-xylene with oxygen and acetic acid at a temperature in a range between about 120° C. and about 220° C. in the presence of a catalyst system,
• said catalyst system consisting essentially of a source of cobalt ion, a source of manganese ions, and a source of bromide ions,
• said reaction mixture being characterized by an initial molar ratio of cobalt ion to halogen-substituted ortho-xylene of less than about 2%, an initial molar ratio of manganese ion to halogen-substituted ortho-xylene of less than about 1.5%, and an initial molar ratio of bromide ion to halogen-substituted ortho-xylene of less than about 0.5%,
• said oxygen being present in an amount corresponding to a partial pressure of oxygen in a range between about 0.0001 and about 15 bar,
• to provide a first product mixture comprising less than 10 percent halogen-substituted ortho-xylene starting material, a halophthalic acid product, and less than about 10,000 parts per million halobenzoic acid by-product and les than 1000 parts per million halophthalide based on a total amount of halophthalic acid present in the first product mixture;
• Step (B) stripping water and acetic acid from the first product mixture;
• Step (C) effecting ring closure of the halophthalic acid to afford a second product mixture comprising a halophthalic anhydride, a halobenzoic acid, and the catalyst system;
• Step (D) perform a first “evaporative separation” of the second product mixture to afford a third product mixture comprising a halophthalic anhydride and a halobenzoic acid, and a residual catalyst mixture comprising a halophthalic anhydride;
• and
• Step (E) perform a second “evaporative separation” of the third product mixture to afford a purified halophthalic anhydride comprising less than about 500 parts per million of a halobenzoic acid and less than 500 parts per million halophthalide.