Catalytic Cracking Of C₄ Alkenes To Propene/ethene

Catalysts design and reaction conditions optimization were investigated systemically for the process of C₄ alkene catalytic cracking, an effective way enhancing propene production.The equilibrium constant of each reaction for butene conversion, along with the effects of temperature and pressure on each reaction, were calculated thermodynamically. According to that, the possibility and feasibility to increase the selectivity of propene in C4 alkene cracking were discussed. These results provided guidance for catalysts design and reaction conditions optimization in C₄ alkene cracking.The catalytic performance of the zeolites with various structures and pore diameters were tested in the process and it was found that: ZSM-5 and MCM-22 exhibited better shape-selectivity for propene plus ethene and the best stability among the zeolites studied; the small-pore SAPO-34 zeolite was the most "shape-selective" for propene and ethene; the large-pore zeolites, the small-pore zeolites and the zeolites with one-dimensional structure all exhibited poor stability due to the covering of the acid sites or channel blockage by the coke.On ZSM-5 zeolite with higher Si/Al₂ ratio, higher selectivities of propene/ethene and better stability were gained, resulted from its lower acidity suppressing the secondary reaction of the alkenes and the coking reaction. High silica ZSM-5 with smaller particles gave better stability in the process. The means modifying the ZSM-5 zeolite by K addition or steaming treatment were introduced to the process of catalyst preparation for C₄ alkene cracking. The catalysts modified to a...