Development of hierarchical ZSM-11 for synthesis of light olefins from crude oil

Abstract

ZSM-11 is recognized as a shape-selective catalyst in various industrial processes; however, the significance of hierarchical ZSM-11 in the direct conversion of crude oil to light olefins remains unexplored. Herein, we report a template-directed hydrothermal method to synthesize hierarchical ZSM-11 zeolite with varying secondary mesopore sizes, acidities, and morphologies. The synthesis strategy controlled the development of uniform nanorods or accumulating nanosized zeolites with SiO₂/Al₂O₃ molar ratios of 30, 35, and 70. The developed two-dimensional 10-membered ring straight channels ZSM-11 catalyst were employed firstly for the steam catalytic cracking of light crude oil to produce light olefins (C₂-C₄). Amongst the various developed catalysts, ZSM-11(35), a hierarchical zeolite with SiO₂/Al₂O₃ molar ratio of 35, outperformed in terms of crude oil cracking conversion (∼66.5 %) and selectivity to C₂-C₄ light olefins (44.1 %). In comparison to diffusion over sinusoidal channels in ZSM-5, ZSM-11 zeolite with tortuous and straight channels facilitated rapid mass transport at low coke deposition.