Anti-toxic stability: The ability of catalyst to resist deactivation of adsorbed active poisons is called anti-toxic stability, these poisons refer to compounds containing sulfur, phosphorus, halogens and arsenic, which may be impurities in raw materials, or by-products or intermediate compounds produced in the reaction; various catalysts have different anti-toxic resistance to various harmful impurities, and the same catalyst has different anti-toxic resistance to the same impurity under different reaction conditions.