A physical mixture of Ru/C and Nb2O5 is an effective catalyst for upgrading lignin monomers to a clean cut of hydrocarbon liquid fuel. The reaction solvent is water with a small amount of methanol additive. The hydrodeoxygenation (HDO) was evaluated by using dihydroeugenol (DHE) as an exemplary model lignin monomer. Under optimized conditions, 100% conversion of DHE and very high selectivity to propyl cyclohexane (C9 hydrocarbon) was achieved. The Nb2O5 was calcined at low temperature (450 °C) and was shown to contain acid sites that enhance the production of fully deoxygenated product. The methanol additive serves as hydrogen source for the Ru/C catalyzed reduction of the aromatic ring. In addition, when a substrate mixture of DHE, isoeugenol and 4-allylsyringol simulating lignin products was employed, 100% conversion to propyl cyclohexane (76%) and propyl benzene (24%) was observed, thereby suggesting the general applicability of this catalyst system for funneling lignin monomers into a clean slate of hydrocarbon liquid fuels. This study sheds light on the function of each catalyst component and provides a simple and green utilization of biomass monomers as a feedstock for renewable hydrocarbon fuels.

One-pot funneling of lignin monomers to C9 hydrocarbons catalyzed by bifunctional heterogeneous catalysis

ACS Spring 2022

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