Surface Science and Modeling Studies of Endothermic Fuels Catalysis.

A description is provided of experimental results from surface science studies and insight from theoretical and modeling studies for new catalysts for endothermic fuels. Our work has focused on providing fundamental information concerning the thermochemistry, kinetics and mechanism of the dehydrogenation of methylcyclohexane MCH to toluene over Pt and Pt alloys or intermetallic compounds. Chemisorption and adsorption kinetics measurements reveal that alkali adatoms or alloys of Pt can promote selectivity in dehydrogenation reactions that yield benzene or toluene. In addition, a new apparatus with a reaction antechamber was constructed that allows catalytic reaction rates to be measured on surfaces that are thoroughly characterized by surface analytical methods. Ab-initio calculations were performed for simple models of alloy catalysts, e.g., Pt2, Pt3, PtZr, Pt3Zr, Zr-H, Pt-H, Zr-CH3, and Pt-CH3. Quasiempirical valence bond QVB calculations were done for the dehydrogenation of MCH on Pt. In addition, new tools were developed for treatments of electron correlation required for these bimetallic catalysts. Two computer programs were also developed to predict accurately the barriers and calculate the pre-exponential factors that appear in the Arrhenius expression for the rate constant in order to predict kinetics from first principles. Hydrocarbon dehydrogenation, Endothermic reactions, Heterogeneous catalysis, Surface chemistry, Dehydrogenation of methylcyclohexane, Catalysis by Pt, Ab initio electronic structure.