Reductive catalytic fractionation of lignin in birch sawdust to monophenolic compounds with high selectivity

Reductive catalytic fractionation (RCF) has emerged as a novel biorefinery strategy for the efficient fractionation and utilization of lignocellulosic biomass. Herein, hydrogenolysis of lignin in birch sawdust in the presence of noble metal based catalysts (Ru/C, Pd/C, Pt/C) were investigated. The total yield of monophenolic compounds was 41.4 wt% (TOF, 5.28 h(-1)) and the selectivity towards 4-propyl guaiacol and 4-propyl syringol reached 82.8 % with 5 % Ru/C under optimized conditions. The cleavage of beta-O-4 and alpha-O-4 (cyclic) aryl ether linkages in the trimers and tetramers resulted in the formation of lignin-derived dimers, which were quantified by the derivatization method. The high surface area of catalysts with the highly dispersed and small sized metallic particles contributed to the degradation of higher molecular weight oligomers. The catalysts could promote the cleavage of C-O-C ether bonds and hydrogenation of unsaturated side-chain C=C bonds to obtain propyl-substituted monophenolic compounds with high selectivity.