Ni5Fe5/Al2O3 catalytic hydrogenolysis of lignin: mechanism investigation and selectivity regulation

Abstract

The development of novel catalysts to regulate product selectivity and insight into the mechanism of lignin hydrogenolysis are important for the comprehensive utilization of lignocellulose. Herein, we present a non-precious bimetallic catalyst Ni₅Fe₅/Al₂O₃ with improved catalytic performance relative to commercial Pd/C and Ni₁₀/Al₂O₃ for hydrogenolysis of woody sawdust. In particular, the selectivity of propylguaiacol and propylsyringol is 79.1%. We developed kinetic experimental studies on β-O-4 model compounds and directly monitored the coniferyl alcohol or sinapyl alcohol intermediates in the reaction system for the first time. This directly demonstrates the lignin hydrolysis reaction pathway with simultaneous breakage of C_α–OH and C_β–O. In the catalytic system, the reason for the difference in selectivity between Ni₅Fe₅/Al₂O₃ and other catalysts is their different hydrogenation pathways for intermediates coniferyl alcohol or sinapyl alcohol. Our work provides both an efficient catalyst and insight into understanding and regulating the mechanism of lignin hydrogenolysis.