Purified terephthalic acid (PTA) is an important product in aromatic chain, which is mainly used to produce polyethylene terephthalate (PET). China implements a licensing system for purified terephthalic acid, that is, the state implements a licensing system for the production, storage, use, management and transportation of dangerous chemicals. Without permission, no unit or individual may produce, store, use, manage and transport dangerous chemicals. Therefore, purified terephthalic acid is a licensed chemical product.