Lignin as a polymer of monomeric aromatic products retains great potential to be the source of valuable fuels and chemicals. As the only nature source of aromatics, lignin composes up to 25% of the plants’ total mass. Nevertheless, lignin is still of low utility, and is considered a waste product by biorefinery and paper pulp industry only for its heating value, due to its inherent complex structure and underdeveloped lignin valorization technologies. Hydrodeoxygenation of lignin into aromatic products was studied by using earth abundant nickel catalyst under relatively mild conditions. High value monomeric aromatic compounds were obtained as products with 69% yield under optimal conditions. Carbohydrates were left as solid residue after lignin depolymerization reactions, and subjected to further utilization by using iron salts as catalyst to produce other useful chemicals.<br/>Mechanistic studies on lignin model compounds were performed to help understand hydrodeoxygenation of lignin complex, and to help design more efficient catalysts in depolymerization of lignin. In this work, lignin beta-5 model compounds with different functional groups have been synthesized and studied. Hydrodeoxygenation reactions of these model compounds were performed using heterogeneous nickel catalyst under mild conditions to study reaction mechanism. Heterogeneous catalyst has the advantage in easy separation from reaction media and the capability to be recycled. Benzylic ether C-O linkage was observed to be selectively cleaved without aromatic ring being hydrogenated. Deuterium labeling reactions were performed and kinetic isotopic effect was stydied to better understand the reaction mechanism.

Total utilization of biomass, lignin and carbohydrate: Using earth abundant nickel catalyst

254th National Meeting (2017)

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