Effect of Mesopores in ZSM-5 on the Catalytic Conversion of Acetic Acid, Furfural, and Guaiacol

Abstract

Biomass can be converted into renewable aromatic hydrocarbons through catalytic pyrolysis using ZSM-5 catalysts. Recent studies have found that the mesoporous ZSM-5 catalyst has a higher catalytic efficiency than the conventional microporous catalyst. To further investigate the effect of mesopores in ZSM-5 on the catalytic pyrolysis of biomass, three types of bio-oil model compounds (acetic acid, furfural, and guaiacol) are selected for conversion on synthetic mesoporous and commercial microporous ZSM-5 catalysts. Results show that the mesoporous catalyst exhibits a higher catalytic efficiency for aromatics production compared to the microporous catalyst, especially for guaiacol. However, the carbon yield of benzene, toluene, and xylene decreases as the molecular weight of the reactant increases. Large mesopores (16–45 nm) in the mesoporous catalyst provide more channels for the transportation of phenolic reactants, which can generate aromatics and also coke deposition through multistage cracking in the small mesopores (2–5 nm). Additionally, the reactants undergo condensation reactions on the microporous catalyst surface directly to form coke and block the pore inlet. This study indicates that the mesoporous structure in the ZSM-5 catalyst mainly improves the catalytic conversion efficiency of macromolecules. Therefore, exploring a better structure of hierarchical mesopores suitable for the catalytic conversion of biomass will be the focus of future work.