Organosilane-assisted synthesis of reduced a-axis ZSM-23 with enhanced performances in catalytic cracking of n-hexane

Abstract

ZSM-23 zeolite with a reduced a-axis is synthesized using trimethoxy[3-(phenylamino)propyl]silane (TPPS) and applied in n-hexane cracking. Once nuclei are formed, TPPS primarily attaches to the ends of rod-like ZSM-23 crystals, effectively hindering elongation growth and significantly promoting the diffusivity of ZSM-23 zeolite. The carbonium pathway is favored over the carbenium pathway in n-hexane cracking when reduced a-axis ZSM-23 is applied, leading to higher ethene yield instead of propene. The fast diffusion also shifts deactivation from an inside-out process to an outside-in one due to the different precursors for carbon deposition. The obtained short a-axis ZSM-23 exhibits excellent catalytic performances in n-hexane cracking, displaying better activity (98.4% vs. 86.4%) and greater stability (2400 min vs. 120 min) than traditional ZSM-23. These findings deepen the understanding of organosilane’s role in unidimensional zeolite synthesis and unveil the structure-performance relationship and deactivation mechanism in n-hexane cracking.