Noble-metal catalyzed hydrodeoxygenation of biomass-derived lignin to aromatic hydrocarbons

Conversion of biomass derived lignin to liquid fuels has the promising potential to significantly improve carbon utilization and economic competitiveness of biomass refineries. In this study, an aqueous phase catalytic process was developed to selectively depolymerize the lignin polymeric framework and remove oxygen via hydrodeoxygenation (HDO) reactions. Efficient methods (ethanol and dilute alkali extraction) for selectively producing reactive lignin oligomers with high yields from corn stover were established. Characteristic structural features of the technical lignins employed for hydrocarbon production were elucidated with the aid of advanced analytical techniques, such as 2D HSQC NMR spectroscopy and gel permeation chromatography (GPC). Combinations of noble metal catalysts in the presence of various solid acid zeolites were tested for HDO activity of the oligomeric technical lignins predominantly containing 8-0-4' inter-unit linkages. Results showed 35%-60% conversion of lignin with 65%-70% product selectivity for aromatic hydrocarbons (e.g. toluene) under various HDO conditions in the presence of noble metals (Ru. Rh and Pt) over Al2O3 (or C) supports and solid acid zeolites (e.g., NH4+ Z-Y 57277-14-1) catalyst matrices.