Big basic nitrogen compounds (BNC) molecules poisoned the active sites on external surface of the catalyst, while small BNC molecules entered pore channels of the catalyst, both caused deactivation of the active sites.

• 大分子碱性氮化物可以毒化催化剂外表面活性中心，小分子碱性氮化物可以进入催化剂孔道，造成催化剂活性中心全部失活。