Effect of Phosphorus Modification of Zn-ZSM-5 Catalyst on BTX Formation from Bio-ethanol

This study investigated the effect of phosphorus (P) modification on Zn-ZSM-5 zeolite catalyst for the conversion of bio-ethanol to benzene, toluene, and xylenes (BTX). Characterization using XRD, N2 adsorption, SEM, and pyridine-adsorbed FT-IR, as well as fixed-bed catalytic tests, demonstrated that P-modification maintains zeolite crystallinity as well as improving hydrothermal stability and suppressing coke formation. P-modified Zn-ZSM-5 catalyst with a P/Al molar ratio of 1.1 maintained 95 % of its initial BTX yield after 40 h of continuous operation and exhibited significantly reduced coke formation rates. A slight decrease in surface area was observed after P-modification, likely due to a modest loss of crystallinity, with limited contribution from partial pore blockage by phosphate species. FT-IR analysis showed that Zn introduction reduced the amount of Brønsted acid sites and increased that of Lewis acid sites, whereas P selectively interacted with the Zn-derived Lewis acid sites without significantly affecting Brønsted acidity. Repeated reaction-regeneration cycles further confirmed the excellent reusability and maintenance of acid sites on the P-modified catalyst. These results indicate that P-modified Zn-ZSM-5 is a highly effective and durable catalyst for the sustainable production of BTX from bio-ethanol.