Roles of bimetallic catalysts and mesoporous supports in enhancing product selectivity in lignin hydrogenolysis and catalyst stability

Abstract

Research into the catalytic hydrogenolysis of lignin focuses mainly on model compounds, leaving the process and mechanism of actual lignin hydrogenolysis ambiguous. There is limited exploration of the internal chemical bonding and degradation pathways of lignin, with concurrent hydrogenolysis and recondensation processes posing a significant challenge. Preventing repolymerization of lignin fragments during the reaction remains challenging, and some described reaction processes in existing literature are purely theoretical speculations, lacking substantial evidence. Additionally, separation and purification of the resulting chemicals remain extremely difficult. To overcome these confines, research on bimetallic catalysts is needed, with the role of supports into consideration. The catalyst support provides better stability for the active sites, selectivity, increased surface area, and better thermal/mechanical stability for the chosen catalyst. The synergistic effect of bimetallic catalysts will lead us to higher activity, selectivity, and stability. The characteristics of mesoporous support, such as suppression of repolymerization, increased surface area, enhanced catalytic activity, controlled product selectivity, and well-ordered pore structure, make them a better choice for lignin hydrogenolysis. This review focuses on the past findings using single metal catalysts and moving to the latest effective findings using bimetallic catalysts and mesoporous support.