Enhancing Catalytic Performance for Benzene Alkylation with Ethanol over Fe-Substituted ZSM-5 Nanosheets by Controlling Diffusion and Acidity

The high-efficiency production of ethylbenzene via benzene-ethanol alkylation is a promising strategy for optimizing resource integration between the petrochemical and coal chemical sectors. Herein, the diffusion properties and acidity of ZSM-5 nanosheets were effectively tailored via modulation of the b-axis thickness and in situ Fe-isomorphous substitution. A comprehensive range of physicochemical analysis revealed that the sample with a 40 nm b-axis thickness exhibited a significant increase in both specific surface area and total pore volume, and meanwhile, partial Fe isomorphous substitution within the ZSM-5 framework facilitated a moderate decrease in Brønsted acid sites without significantly sacrificing total acid sites. Thanks to the well-balanced acidic density, types, and strength to inhibit the side reactions during benzene alkylation with ethanol, as well as the enhanced mass transfer facilitated by the thin b-axis, the optimized Fe-substituted nanosheet catalyst, featuring a b-axis thickness of around 40 nm and an Fe/Fe + Al ratio of 0.33, demonstrated exceptional catalytic performance. This catalyst achieved a benzene conversion of 68.5% and ethyl selectivity of 99.0% at a low benzene-to-ethanol ratio (1:1) with a weight hourly space velocity (WHSV) of 4 h^–1, Additionally, this catalyst also could exhibit exceptional stability, maintaining its catalytic activity over 182 h even at a high WHSV of 12 h^–1. This study proposes an efficient strategy for synergistic optimization involving mitigating mass-transfer influence and in situ modulating acidity, offering valuable insights into rational design of high-performance zeolite catalysts for benzene-ethanol alkylation.