(345c) Density Functional Theory Evaluation of M-Doped Ceria for Desulfurization and Hydrocarbon Conversion

Biomass conversion to liquid fuels may be accomplished through gasification to syngas followed by fuel synthesis processes, enabling a renewable energy source of liquid fuels. Prior to fuel synthesis catalysts, the syngas must be cleaned of sulfur and tar species. In a Department of Energy forecast for 2012, approximately 50% of the cost to produce ethanol from biomass is involved in syngas cleanup. Ceria-based mixtures have shown promise in both desulfurization and hydrocarbon conversion. Our goal is to design a ceria-based catalyst that can reform the large hydrocarbons into CO and H₂ and remove sulfur at high temperatures, thus making biomass gasification-based processes viable for sustainable liquid fuel production. Density functional theory (DFT+U) is used to generate composition-function relationships for H₂S adsorption and hydrocarbon conversion. Mn-doped CeO₂ has been shown experimentally to absorb H₂S and reform hydrocarbons. The transferability of DFT+U to Mn-doped CeO₂ is also examined. Methane adsorption energy correlates with oxygen vacancy formation energy for M-doped CeO₂. Dopants in CeO₂ can alter the reducibility of the ceria atoms or become the reduction center. The methane conversion rate follows a volcano relationship with surface reducibility.