Ethane hydrogenolysis over platinum - Selection and estimation of kinetic parameters

Kinetic models are formulated to describe the essential surface chemistry i nvolved in ethane hydrogenolysis over platinum catalysts, through consolida tion of results obtained from first principles calculations and reaction ki netics studies. Quantum chemical calculations based on density functional t heory (DFT) were conducted to probe the structures and energetics of variou s adsorbed C2Hx, species on platinum, as well as activated complexes involv ed in cleavage of the C-C bond. De Donder relations were used to identify k inetic coefficients that minimize complications from unintentional compensa tion effects. Results from DFT calculations and kinetic analyses suggest th at the most abundant surface species during ethane hydrogenolysis are adsor bed atomic hydrogen and highly dehydrogenated hydrocarbon species (e.g. eth ylidyne species), whereas the primary reaction pathways for cleavage of the C-C bond on Pt take place through transition states that are more highly h ydrogenated (e.g. C2H5 and CHCH3 species). The results from DFT calculation s indicate that CPH, adsorbed species and transition states interact more s trongly with Pt(211) than with Pt(111) surfaces, in agreement with the know n structure sensitivity of ethane hydrogenolysis over Pt catalysts. (C) 200 0 Elsevier Science B.V. All rights reserved.