Synthesis of ZSM-48 zeolites and their catalytic performance in C4-olefin cracking reactions Original Research Article

ZSM-48 zeolite samples with a series of SiO2/Al2O3 ratios were synthesized in the hydrothermal system of Na2O–SiO2–Al2O3–H2N(CH2)6NH2 (HDA). The samples were characterized by X-ray powder diffraction, N2 adsorption, scanning electron microscopy, temperature-programmed desorption of ammonia, thermo-gravimetric analysis and chemical analysis. Both the OH−/SiO2 and SiO2/Al2O3 ratios played key roles for the formation of pure ZSM-48. C4-olefin cracking reactions were carried out on these ZSM-48 zeolites to produce propylene. Compared with currently used HZSM-5 zeolite, HZSM-48 zeolite exhibits a more excellent selectivity for the aimed olefins, especially for those with lower SiO2/Al2O3 ratios. The difference of catalytic performance of HZSM-48 and HZSM-5 zeolites for the cracking of C4-olefin can be attributed to their different acidities. The influences of reaction temperature and liquid hour space velocity on the catalytic performance of the HZSM-48 catalysts were investigated. The reasons for the deactivation of HZSM-48 zeolite in C4-olefin cracking reactions were also studied.