Collaborative Research: SusChEM: Rational design of non-precious metal catalysts for a future biorefining industry

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The use of biomass such as waste wood products and corn stalks is attractive as a potential source of fuel and chemical feedstocks. Heterogeneous catalysts are often used in the transformation of biomass to useful chemicals, but the most effective known catalysts are composed of rare and expensive platinum group metals. Dr. Heyden of the University of South Carolina and Dr. Chen of Columbia University are collaborating to develop a cheap and abundant material, molybdenum carbide (Mo2C) as a replacement for platinum. They are studying how the catalytic properties of Mo2C can be enhanced by the addition of iron, copper, cobalt and nickel for sustainable chemistry of biomass transformation. The team is elucidating the underlying science needed for the development of highly selective, non-precious metal catalysts for upgrading a specific chemical derived from biomass called glycerol (C3H8O3). Glycerol has been identified as one of the top twelve building block chemicals that can be derived from sugar and converted to high-value bio-based chemicals and materials. Also, glycerol is a major by-product of the biodiesel production by transesterification of vegetable oils and the diversification of products derived from glycerol has been identified as a key issue for biodiesel production. A major focus of their research lies in evaluating the degree of the surface oxidation due to the presence of oxygen in the glycerol and in water, and in developing the understanding of how oxygen modification of the catalyst affects the reaction. Research activities also form broader impacts through the establishment of summer research internships for undergraduate students in the laboratories of Drs. Chen and Heyden, who mentor students to encourage them to pursue graduate studies and careers in renewable energy and chemical production. Drs. Chen and Heyden are also actively engaged in integrating research results into the undergraduate and graduate chemical engineering curriculum at Columbia University and the University of South Carolina.With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Chen of Columbia University and Dr. Heyden of the University of South Carolina are developing highly selective, non-precious metal catalysts for the hydrodeoxygenation (HDO) of biomass-derived polyols. Current HDO catalysts are primarily based on platinum-group metal catalysts, but their high costs and limited abundance are potential concerns for the production of cost-effective, biomass-based fuels and chemicals. In particular, molybdenum carbide (Mo2C) is highly selective for C-O/C=O bond cleavage (C = carbon and O = oxygen) and can furthermore be modified by non-precious 3d-metals (iron, cobalt, nickel, and copper) to enhance the catalytic activity, selectivity, and stability for targeted HDO reactions. To identify the active sites in Mo2C and 3d-metal modified Mo2C and the reaction mechanism of the HDO of biomass-derived polyols on these active sites, Drs. Chen and Heyden apply a combined computational and experimental research approach that is based on density function theory (DFT) calculations on single crystal model surfaces. They also use ultrahigh vacuum (UHV) experiments on single crystal model surfaces to validate DFT-predicted trends, reactor evaluations over the corresponding powder catalysts, microkinetic reactor modeling under various experimental reaction conditions, and systematic correlation of experimental data with computational models. Knowledge from the proposed research provides guidelines for designing non-precious metal catalysts for the selective transformation of glycerol in particular and of biomass-derived molecules in general. Broader impacts in education are included by integrating research findings into undergraduate and graduate electives in the core chemical engineering curriculum at Columbia University and the University of South Carolina.