Method for crystallizing and purifying 3-chlorophthalic anhydride

The invention relates to a method for crystallizing and purifying 3-chlorophthalic anhydride. The method comprises the following steps of mixing a chlorophthalic anhydride mixture containing the 3-chlorophthalic anhydride with a mixed solvent under a stirring action, heating to 55 to 65 DEG C, and completely dissolving the mixture; cooling the material to 5 to 15 DEG C in a cooling crystallization manner so as to obtain crystal suspension of the 3-chlorophthalic anhydride; performing filtering, solvent washing and drying treatment on the suspension so as to obtain a 3-chlorophthalic anhydride crystal product. The method disclosed by the invention has the advantages that the purity and yield of the crystallization product are effectively guaranteed by means of selecting the type and composition proportion of the mixed solvent and controlling the crystallization operation conditions at the same time by utilization of the difference of dissolvability of the 3-chlorophthalic anhydride and other chlorophthalic anhydride products in different solvents; the 3-chlorophthalic anhydride crystallization product with the purity of 99.0 percent or higher and the crystallization yield of 70.8 percent or higher can be obtained; the effects of low operation temperature, less energy consumption, strong operability and higher industrial application value are achieved, and the obtained 3-chlorophthalic anhydride product is high in purity and yield.