Direct Catalytic Conversion of Lignin to Aromatic Compounds

Large quantities of lignin are currently being generated and processed by the pulp and paper industry and with the development of Biorefineries the amount of lignin produced will dramatically increase. Lignin accounts for about 15-30% of lignocellulosic biomass, and can serve as an abundant renewable resource for production of aromatic chemicals instead of the waste disposal problem it poses today. However, due to the complex nature of lignin and the lack of suitable conversion technologies, selective lignin depolymerization to value-added products is a challenging problem. The focus of the proposed project is to address this challenge by developing a robust process for direct catalytic conversion of lignin to aromatic chemicals. Lignin, a byproduct from our ionic liquid pretreatment biorefinery, will be catalytically converted to value-added chemicals. Isolated lignin will be subjected to homogeneous catalytic hydrogenolysis in an ionic liquid media with inexpensive metal catalysts. Screening the right combination of ionic liquids for enhanced lignin dissolution and improved catalytic activity will yield phenolic compounds in higher quantities and less waste in the form of biochar. Various ILs, metals, and ligands as well as processing parameters of temperature and pressure will be investigated to establish the most promising candidates of IL, catalyst and processing conditions for production of monomeric phenols. Commercial Applications and Other Benefits: The production of value-added products from lignin would be a critical step towards an integrated biorefinery aimed at complete utilization of biomass for economical operation and multiproduct development. This substantially improves the revenues of the biorefineries and fulfills the Department of Energys goal for greener, renewable fuels and chemicals. Monomeric phenols find commercial applications in medical, pharmaceutical, polymeric and general applications. Some specific examples include: phenolic resins, bisphenol A for producing polycarbonate, and caprolactam for producing Nylon 6. Moreover, the mild processing conditions targeted for lignin valorization together with the recyclability of ionic liquids make the process much greener, renewable and sustainable.