Mechanistic investigation of the Zn/Pd/C catalyzed cleavage and hydrodeoxygenation of lignin

While current biorefinery processes use lignin only for its heat value, the conversion of lignin to high value chemicals is an area of increasing interest. Herein we present a detailed mechanistic study of the hydrodeoxygenation (HDO) of lignin by using a synergistic Pd/C and Zn-II catalyst through use of both lignin model compounds and lignocellulosic biomass. Spectroscopic data coupled with the study of lignin model compounds suggest that Zn-II activates and facilitates removal of the hydroxyl group at the C. position of the beta-O-4 ether linkage. Activation is proposed to occur through formation of a six-membered ring complex of ZnII coordinated to the oxygen atoms at C alpha and C gamma of the lignin model compound guaiacylglycerol-beta-guaiacyl. [GRAPHICS] .