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

Janik, M. J., Pennsylvania State University
Krcha, M. D., Pennsylvania State University
Li, R., Louisiana State University
Dooley, K. M., Louisiana State University

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.