Carbon Materials as Catalyst Supports and Catalysts in the Transformation of Biomass to Fuels and Chemicals

Carbon plays a dual role as a catalyst or a catalyst support for chemical and enzymatic biomass transformation reactions due to its large specific surface area, high porosity, excellent electron conductivity, and relative chemical inertness. Advantageously, carbon materials can be prepared from residual biomass, an attractive property for decreasing the so-called "carbon-footprint" of a biomass transformation process. Carbon can be chemically functionalized and/or decorated with metallic nanoparticles and enzymes to impart or improve novel catalytic activity. Sulfonated porous carbon materials exhibit high reactivity in diversified catalytic reactions compared to their nonporous counterparts. However, the SO3H groups prevent the incorporation of hydrophobic molecules into the bulk, thereby causing hydrophobic acid-catalyzed reactions to proceed only on the surface. Metal and enzymatic catalysts on carbon supports have significant advantages over other oxide materials for different types of reactions. The future success of biorefinery will require the design of a new generation of multifunctional catalysts, possibly derived from emerging carbon materials such as graphene, carbon nanotubes, and carbon monoliths, for the selective processing of carbohydrates and lignin. The most achievable and economical way is to convert lignocellulosic biomass directly, rather than pure cellulose, hemicellulose, or lignin using multifunctional catalysts.