Upgrading of Biomass Pyrolysis Oil Quality Via the Coupled Process of Small Molecule Catalytic Activation and Biomass Pyrolysis

Abstract

Currently, the comprehensive utilization of biomass has attracted significant attention, and fast pyrolysis is increasingly regarded as one of the most promising technologies for biomass conversion. In this study, a fixed-bed reactor was employed to investigate the effects of rice husk pyrolysis under various atmospheres (H₂, CH₄, H₂-CH₄) and catalysts conditions. The results indicate that the bio-oil yield reached 37.30 wt% at 500 ℃ for 30 min under an H₂-CH₄ (11:5) mixed atmosphere. Among the metal-modified HZSM-5 catalysts with different zinc loadings, the variant containing 5% Zn demonstrated superior catalytic performance. This improvement was attributed to the uniform crystalline morphology and hierarchical porous structure of HZSM-5, which facilitate biomass pyrolysis. Furthermore, ¹³CH₄ isotope tracer experiments combined with nuclear magnetic resonance (NMR) analysis of bio-oil confirmed that the small-molecule gases produced reactive •CHₓ and •H radicals via catalytic activation. These radicals participated in the biomass pyrolysis reaction and promoted the formation of phenolic compounds.