Tailored core-shell ZSM-5@Silicalite-1 zeolite catalysts for enhanced aromatic product formation in microwave-assisted pyrolysis of water hyacinth

This study successfully synthesizes core-shell ZSM-5@Silicalite-1 catalysts with controlled morphology and acidity by modulating the shell/core mass ratio. The catalyst with a shell/core mass ratio of 2, which exhibits a balanced core-shell structure, proves optimal for microwave-assisted catalytic fast pyrolysis of water hyacinth. Through this microwave-assisted catalytic pyrolysis process, a bio-oil yield of 35.6 wt% can be obtained from water hyacinth. The silicalite-1 shell effectively passivates external acid sites, suppressing coke formation and directing reactions towards the internal ZSM-5 core. As a result, the core-shell ZSM-5@Silicalite-1 reduces coking by 66.7 % and boosts the aromatics yield by 45.5 %. This leads to enhanced production of valuable aromatic hydrocarbons while mitigating catalyst deactivation. Moreover, water hyacinth pyrolysis achieves 19.5 % monocyclic aromatic selectivity via this tailored catalyst. The integrated “deoxygenation-aromatization” pathway, facilitated by Brønsted acid sites and the hydrocarbon pool mechanism, substantially improves bio-oil quality and monocyclic aromatic hydrocarbon selectivity. The catalyst with a shell/core mass ratio of 2, with its tailored porosity and acidity, demonstrates superior performance in cracking complex biomass components. The findings underscore the potential of core-shell zeolites in biomass valorization, offering a promising strategy for sustainable energy production and addressing environmental challenges associated with invasive aquatic plants like water hyacinth.