Enhanced catalytic cleavage of C-O and C-C bonds of raw biomass into lignin monomers and glucose

Abstract

Reductive catalytic fractionation (RCF) of lignocellulose has been considered to be a promising strategy for the separation and subsequent upgradation of biomass constituents. However, the recalcitrant C-C bonds in lignin were the major limitation to produce aromatic monomers in high yield for the hydrogenolysis of lignocellulosic biomass under mild conditions. Herein, an efficient approach was developed to catalytic in-situ hydrogenolysis of solid biomass into lignin monomers and glucose using Ni-Al catalyst with Ni2Al3 alloy phase. 62.9 wt% of aromatic monomers yield was achieved with the degree of delignification up to 89.8 %. Two-dimensional heteronuclear single quantum correlation nuclear magnetic resonance (2D HSQC NMR) spectrum emerged that the C-O and C-C bonds involving β-O-4, β-β and β-5 linkages were all catalytically broken. Moreover, the cellulose was recovered with the cellulose retention and purity of 80.1 % and 88.2 %, respectively, which was further enzymatically hydrolyzed to glucose with the yield of 92 %. Overall, the efficient fractionation and transformation of biomass constituents were realized simultaneously.