Biomass waste-derived biochar catalysts with Ru loading for selective and efficient transformation of lignin and its model compound

Selective transformation of lignin and its model compound is an efficient process for the valorization of lignin to valuable biofuels and chemicals. Here a series of Ru-loaded biochar (BC) catalysts from different biomass waste were developed and applied for the hydrolygenolysis of three lignin model compounds and alkaline-treated lignin, providing both maximum sustainability and economical profitability. The BC from bamboo waste with Ru loading (designated as Ru/BABC) was found to exhibit superior catalytic performance among all the carbon catalysts, giving complete conversion of model compounds and selectivities of 80.8 %, 86.0 %, 88.8 % of monocyclic products from diphenyl ether (DPE), benzyl phenyl ether (BPE) and phenethoxybenzene (PPE) respectively. Ru/BABC also exhibited excellent stability as evidenced by the 5-time recycling experiment with minimum Ru leaching. The reaction pathways for the hydrogenolysis of three model compounds were established to reveal the catalytic mechanisms of Ru/BABC and their promotions on the product selectivity. The superiority of Ru/BABC is supposed to result from its excellent porosity, a diversity of functional groups on the support and extremely high adsorption energies for the reactants which are revealed by DFT calculations. This work aims to provide some guidance for the development of BC catalysts from biomass waste, and to shed some clues on the catalytic transformation of lignin into value-added products.