Phthalic anhydride, also known as phthalic anhydride or PA, is an important organic chemical raw material widely used as a plasticizer, unsaturated polyester resin (UPR), alcohol acid resin, and amino resin coating material. In addition, it is also used in the production of dyes to synthesize anthraquinone and other compounds. Benzoic anhydride is also a raw material for the production of saccharin, used in the pesticide industry to produce imidacloprid, and in the pharmaceutical industry to produce laxatives such as phenolphthalein. At room temperature, phthalic anhydride crystallizes as a flaky white solid. The industrial production of phthalic anhydride adopts the ortho xylene method and the industrial naphthalene method.