Solar Enriched Biofuels Via Oxidizable Metal Catalysts

One of the fundamental challenges in the production of liquid fuels and chemicals from biomass is the necessary upgrading of biomass feedstocks and products to reduce their oxygen content. This is particularly true for the oxygen-rich bio-oils generated in fast pyrolysis and hydrothermal liquefaction processes. In this study, a novel reactor scheme is presented for bio-oil upgrading in which the bio-oil is deoxygenated with hydrogen produced in situ through the oxidation of a metal species with water. In a process similar to chemical looping, the formed metal oxide is then recycled by reduction in a high-temperature solar-thermal electrolytic process, yielding the original metal reactant. We compare thermodynamic trends of many metal/metal oxide (M/MO) pairs and present a volcano plot based on this analysis, allowing for optimized metal selection. Additional parameters in M/MO selection are discussed, including phase, change in oxidation state and global availability. Finally, the formation of an oxide layer on metal surfaces is modeled computationally using density functional theory calculations for the most promising M/MO pairs.