Reaction pathway analysis

Heinen M, Jusys Z, Behm RJ. 2009. Reaction pathways analysis and reaction intermediate detection via simultaneous differential electrochemical mass spectrometry (DBMS) and attenuated total reflection Bourier transform infrared spectroscopy (ATR-BTIRS). In Vielstich W, Gasteiger HA, Yokokawa H, eds. Handbook of Buel Cells. Volume 5 Advances in Electrocatalysis. Chichester John Wiley Sons, Ltd., in press. 

Reaction pathway analysis and the closely associated topic of applied chemical kinetics are at the heart of both the practice and study of chemical reactions. They often form the basis of the process engineer s conservation equations and subsequent reactor design, but also can be the starting point for fundamental mechanistic inference. This centrality of reaction pathways guarantees their relevance and motivated this ACS symposium on the topic. 

Whereas selective diffusion can be better investigated using classical dynamic or Monte Carlo simulations, or experimental techniques, quantum chemical calculations are required to analyze molecular reactivity. Quantum chemical dynamic simulations provide with information with a too limited time scale range (of the order of several himdreds of ps) to be of use in diffusion studies which require time scale of the order of ns to s. However, they constitute good tools to study the behavior of reactants and products adsorbed in the proximity of the active site, prior to the reaction. Concerning reaction pathways analysis, static quantum chemistry calculations with molecular cluster models, allowing estimates of transition states geometries and properties, have been used for years. The application to solids is more recent. 

Izzo, B. Klein, M.T. LaMarca, C. Scrivner, N.C. Hydrothermal reaction of saturated and unsaturated nitriles Reactivity and reaction pathway analysis. Ind. Eng. Chem. Res. 1999, 38, 1183-1191. 

Graham, D. J., Schulmerich, M. V. 2004. Information Content in Organic Molecules Reaction Pathway Analysis via Brownian Processing, J. Chem. Inf, Comput. Sci, 44, 1612. 

Note that H2, CO, and CH4 are shown in Table 2-1 as potentially undergoing direct anodic oxidation. In actuality, direct electrochemical oxidation of the CO and CH4 usually represents only a minor pathway to oxidation of these species. It is common systems analysis practice to assume that H2, the more readily oxidized fuel, is produced by CO and CH4 reacting, at equilibrium, with H2O through the water gas shift and steam reforming reactions, respectively. A simple reaction pathway analysis explains why direct oxidation is rarely the major reaction pathway under most fuel cell operating conditions ... 

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