SAPO分子筛的二甲苯异构化反应性能研究——酸性和孔结构对其催化性能的影响

Silicoaluminophosphate molecular sieves SAPO-5, SAPO-11 and SAPO-41 were synthesized and characterized by XRD, IR and pyridine adsorption IR. Their catalytic performances in isomerization of m-xylene were investigated. SAPO-11 owns the largest number of acid sites, particularly the strong Brnsted acid sites, and then exhibits the highest activity and selectivity to p-xylene; whereas low activity and selectivity were obtained over SAPO5 catalyst. The sequence of activity and the number of strong Brnsted acid sites of the SAPOs followed SAPO-5＜SAPO-41≈SAPO-11. Both SAPO-11 and SAPO-41 produce predominantly the p-xylene isomer due to their medium size pores.