title: Analysis of reaction schemes using maximum rates of constituent steps.
abstract: We show that the steady-state kinetics of a chemical reaction can be analyzed analytically in terms of proposed reaction schemes composed of series of steps with stoichiometric numbers equal to unity by calculating the maximum rates of the constituent steps, rmax,i, assuming that all of the remaining steps are quasi-equilibrated. Analytical expressions can be derived in terms of rmax,i to calculate degrees of rate control for each step to determine the extent to which each step controls the rate of the overall stoichiometric reaction. The values of rmax,i can be used to predict the rate of the overall stoichiometric reaction, making it possible to estimate the observed reaction kinetics. This approach can be used for catalytic reactions to identify transition states and adsorbed species that are important in controlling catalyst performance, such that detailed calculations using electronic structure calculations (e.g., density functional theory) can be carried out for these species, whereas more approximate methods (e.g., scaling relations) are used for the remaining species. This approach to assess the feasibility of proposed reaction schemes is exact for reaction schemes where the stoichiometric coefficients of the constituent steps are equal to unity and the most abundant adsorbed species are in quasi-equilibrium with the gas phase and can be used in an approximate manner to probe the performance of more general reaction schemes, followed by more detailed analyses using full microkinetic models to determine the surface coverages by adsorbed species and the degrees of rate control of the elementary steps.
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706.
authors.forename: Ali Hussain
authors.initials: AH
authors.lastname: Motagamwala
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706 jdumesic@wisc.edu.
authors.forename: James A
authors.initials: JA
authors.lastname: Dumesic
keywords: catalysis; chemical kinetics; microkinetics