High activity in catalytic cracking of large molecules over a novel micro-micro/mesoporous silicoaluminophosphate

A novel micro-micro/mesoporous silicoaluminophosphate ZSM-5-SAPO-5/MCM-41 (define as MZS-5) composite material with regular spherical morphology was synthesized through a novel process of the self-assembly of CTAB surfactant micelles with silica-alumina source which originated from the alkaline treatment of ZSM-5 zeolite. The physical properties of the MZS-5 composite material were characterized by XRD, FT-IR, Nitrogen adsorption–desorption, SEM and Py-FTIR techniques. Catalytic tests showed that the MZS-5 composite catalyst exhibited higher catalytic activity compared with the conventional microporous ZSM-5, SAPO-5 zeolite and mesoporous Al-MCM-41 molecular sieve for catalytic cracking of 1,3,5-triisopropylbenzene (TIPB). The remarkable catalytic reactivity of TIPB molecules was mainly attributed to the presence of the hierarchical zeolite structure. In the MZS-5 structure, the mesopores provided pathways for transportation of larger molecules and the microporous ZSM-5 and SAPO-5 zeolite provided acidic sites for catalytic activity. A novel micro-micro/mesoporous silicoaluminophosphates MZS-5 catalyst exhibited higher catalytic activity than microporous ZSM-5, SAPO-5 and mesoporous Al-MCM-41 for catalytic cracking of 1,3,5-triisopropylbenzene due to its hierarchical porosity.