Effect of phosphorus and mesopore modification on the HZSM-5 zeolites for n-decane cracking

The objective of this work is to investigate the catalytic effect of a series of modified HZSM-5 zeolites on n-decane cracking at 500 °C and atmospheric pressure. The zeolite catalysts were prepared with phosphorus and/or mesopore modification by excessive impregnation and/or hydrothermal treatment, and were characterized with various methods including SEM, TEM, XRD, FTIR, N ₂ adsorption-desorption measurement and NH ₃ -TPD. Results show that the addition of phosphorus adjusted the distribution and strength of acid sites in the zeolite crystals. The introduced mesoporous structure improved the diffusion of reactants and products in zeolite pores during n-decane cracking. With appropriate acid amounts and distribution, as well as short channels and high specific surface area, the modified HZSM-5 nanoparticles exhibited higher catalytic activity, better light olefins selectivity and longer lifetime, compared with the original HZSM-5 zeolite. The phosphorus modified HZSM-5 zeolites coupling with MCM-41 matrix was proved to be a promising catalyst for the thermal cracking of n-decane.