Improved nickel nanocatalysts for selective cleavage of lignin model compounds and lignin

Abstract

The selective hydrogenolysis of lignin offers a promising avenue for converting lignin into valuable chemicals and fuels. However, the development of highly active catalysts for this process remains challenging. In this study, a series of Ni_x/Al₂O₃ catalysts were synthesized by calcining and reducing layered double hydroxides (LDHs) precursors. These catalysts were evaluated for their effectiveness in catalyzing the conversion of lignin-derived model compounds (2-phenoxy-1-phenylethanol and diphenyl ether). Remarkably, the optimized Ni₃/Al₂O₃ catalyst demonstrated exceptional performance in cleaving C–O bonds, achieving complete conversion with high selectivity for monomers product under reaction conditions of 200 °C, 1 MPa H₂, and 1 h. The catalyst's outstanding performance can be attributed to its relatively large specific surface area, Ni loading exceeding 50 wt%, well-dispersed Ni metal particles, abundant surface oxygen vacancies, and a significant number of acid sites. Additionally, the hydrogenolysis of lignin using the Ni₃/Al₂O₃ catalyst resulted in a substantial production of monophenols (15.0 wt%). This study introduces a novel approach for tailoring highly active Ni nanocatalysts and highlights the capability of Ni_x/Al₂O₃ catalysts to efficiently cleave C–O bonds in lignin under mild reaction conditions.