Ruthenium-Loaded Heteroatomic Zeolite for Selective Hydrodeoxygenation Reaction in Aqueous Medium

Abstract

Catalytic hydrodeoxygenation (HDO) is critical for bio-oil upgrading, yet the selective cleavage of stable C(sp²)-OH bonds in lignin-derived substrates under aqueous conditions remains a challenge. Here, we report a heteroatomic zeolite catalyst, Ru_FA/SAPO-34-Nb, featuring few-atom Ru clusters on a Nb(V)-modified SAPO-34 framework, which achieves highly efficient HDO of lignin-derived creosol (2-methoxy-4-methylphenol) in water. Under mild conditions (250 °C, 7 bar H₂, 24 h), this catalyst delivers quantitative conversion of creosol to toluene (99.2% conversion, 99.6% selectivity), fully preserving the aromaticity of lignin-derived feedstocks─a key requirement for sustainable production of chemicals. Synchrotron X-ray diffraction, X-ray absorption spectroscopy, and inelastic neutron scattering, combined with theoretical modeling, elucidate the cooperative mechanism: the Nb(V) sites selectively cleave the strong C-O bonds, while the few-atom Ru cluster generates hydrogen species with an exceptionally low rotational barrier of 65 cm^-1. This synergistic interaction enables the direct and selective HDO of C(sp²)-O bonds without saturation of the aromatic ring. This work establishes a promissing strategy for aqueous-phase HDO catalysis and provides a general approach for designing bimetallic zeolite catalysts to convert lignin-derived compounds to value-added aromatic chemicals, advancing sustainable biorefinery processes.