Catalytic hydrogenolysis of lignin β-O-4 aryl ether compound and lignin to aromatics over Rh/Nb₂O₅ under low H₂ pressure

The increasing risk of fossil fuels depletion due to surging energy demand has accelerated the search of alternative renewable sources. Lignin, one of the major components of lignocellulosic biomass, is the only abundant renewable natural resource for aromatic compounds. In this work, the effects of metals and process parameters were discussed via the catalytic hydrogenolysis of β-O-4 lignin model compound, 2-phenethyl phenyl ether. The best results were obtained over Rh/Nb₂O₅ with an overall conversion of 99.3% and exceptional selectivity of 98.9% to aromatic products when the hydrogenolysis was carried out at 260 °C and 0.1 MPa H₂ for 4 h. The high efficiency is mainly attributed to the cooperation between Rh and NbOx at the perimeter sites, in which Rh particles are responsible for the dissociation of H₂ and NbOx for activating C–O bonds. With respect to depolymerize of ash wood lignin, the liquid products were mostly aromatics over Rh/Nb₂O₅ under 0.1 MPa H₂. The results achieved in this work provide a promising prospect towards valorization of lignin into production of valuable aromatic compounds under low hydrogen pressure.