Journal of Molecular Catalysis A-Chemical, Vol.163, No.1-2, 91-103, 2000
Ethane hydrogenolysis over platinum - Selection and estimation of kinetic parameters
Kinetic models are formulated to describe the essential surface chemistry involved in ethane hydrogenolysis over platinum catalysts, through consolidation of results obtained from first principles calculations and reaction kinetics studies. Quantum chemical calculations based on density functional theory (DFT) were conducted to probe the structures and energetics of various adsorbed C2Hx, species on platinum, as well as activated complexes involved in cleavage of the C-C bond. De Donder relations were used to identify kinetic coefficients that minimize complications from unintentional compensation effects. Results from DFT calculations and kinetic analyses suggest that the most abundant surface species during ethane hydrogenolysis are adsorbed atomic hydrogen and highly dehydrogenated hydrocarbon species (e.g. ethylidyne species), whereas the primary reaction pathways for cleavage of the C-C bond on Pt take place through transition states that are more highly hydrogenated (e.g. C2H5 and CHCH3 species). The results from DFT calculations indicate that CPH, adsorbed species and transition states interact more strongly with Pt(211) than with Pt(111) surfaces, in agreement with the known structure sensitivity of ethane hydrogenolysis over Pt catalysts.