Harnessing hydrogen activation capability and Lewis acidity in bimetallic Mo-W/H-Beta catalysts for enhanced lignin depolymerization

Despite significant advances in lignin depolymerization studies, the specific combination of Mo and W in bimetallic catalysts and their impact on hydrogen activation and Lewis acidity in lignin conversion remains poorly understood, particularly in terms of the synergistic effects that enhance efficiency and selectivity. A bimetallic Mo x W y /H-Beta catalyst was synthesized via incipient wetness impregnation with the catalyst characterized using XPS, H 2 -TPR, NH 3 -TPD, and other methods. The catalyst demonstrated high activity for selective kraft lignin depolymerization due to the synergy between Lewis acid sites, hydrogen activation sites, and the Mo-W interaction on the support. The proximity of metal and acid sites facilitated effective diffusion of intermediates, leading to enhanced synergy and the eventual cleavage of etheric C–O bonds. A Liquid fuel (LF) yield of 84.3 % and 71.6 % kraft lignin conversion at 300 °C without external hydrogen. The higher heating value (HHV) increased from 25.45 MJ/kg in the original kraft lignin feed to 35.9 MJ/kg in the LF. XPS analysis showed a predominant amount of Mo 6+ on the fresh catalyst surface, with complete conversion to lower oxidation states during the reaction. This study provides insights into the structure–activity relationships of Mo-based bimetallic catalysts, highlighting the importance of hydrogen activation sites and acidic sites in kraft lignin depolymerization.