Non-precious metal catalysts supported by activated carbon and TiO2–SiO2: Facile preparation and application for highly effective hydrodeoxygenation of syringol–a lignin-derived model compound

Abstract

Non-precious metal catalysts (10 wt% loading) over activated carbon (AC) and TiO2–SiO2 supports prepared via incipient wetness impregnation and spray pyrolysis were characterized using various analytical techniques. AC with a higher surface area displayed a better ability than TiO2–SiO2 in syringol conversion and hydrocarbon product selectivity. Compared to Fe and NiFe catalysts, the Ni catalyst showed more effective hydrodeoxygenation performance in terms of syringol conversion, selectivity, and the yield of oxygen-free products (mainly alkylbenzenes via transalkylation reactions). The deoxygenation ability was confirmed via the moisture and COx release. The highest syringol conversion (99.91%) could be obtained using 10 wt% Ni/AC. Generally, syringol hydrodeoxygenation in a fixed-bed reactor followed the main reaction pathway of the hydrogenolysis of CAr–OC(sp3) and CAr–OH rather than the hydrogenation of the benzene ring, producing p-xylene, phenol, and cresols as the major products. Besides metallic catalysts and supports, the reaction temperature and the total flow rate of the H2/Ar mixture on hydrodeoxygenation performance were also investigated. Our study provides a promising potential in the utilization of non-precious metals and biomass-derived AC to remove oxygen from bio-oil model compounds, contributing to the development of sustainable renewable energy.