Efficient hydrodeoxygenation of lignin-derived oxygenates over Ni/Al2O3-C catalyst under mild conditions

Abstract

Hydrodeoxygenation (HDO) is a crucial technique for upgrading biomass-derived compounds, playing a significant role in the advancement of sustainable energy technologies. Under harsh reaction conditions, conventional HDO catalysts often suffer from reduced efficiency due to particle aggregation. This study presents a highly efficient Ni/Al₂O₃-C catalyst that mitigates this issue by stabilizing Ni metal particles and enhancing metal-support interactions. Characterization of the catalyst was carried out using XRD, TEM, and CO-TPD, which revealed that the incorporation of Al species improved metal dispersion and reduced the size of the Ni particles. Guaiacol, a phenolic compound derived from lignin, was chosen to evaluate the HDO performance under mild conditions. The optimized Ni/3Al₂O₃-5C catalyst achieved a guaiacol conversion of 99.9 % with a cyclohexane selectivity of 99.8 % at 210 °C. The outstanding performance is attributed to the high hydrogenation capacity of the small Ni particles and the acid sites on the carbon surface. Metal-support interactions stabilize the Ni particles, preventing leaching and deactivation. The catalyst has also exhibited comparable effectiveness in the HDO of both lignin-derived compounds and lignin-oils, confirming its adaptability across various substrates. The study demonstrates that Al₂O₃-C plays a crucial role in enhancing both the structural stability and catalytic efficiency of HDO catalysts, offering a promising approach for upgrading biomass-derived compounds.