Microkinetic model for WGS over ionic platinum substituted ceria under r-WGS conditions

Water Gas Shift reaction (WGS) is limited by the thermodynamic equilibrium constraint at higher temperatures. This is predominantly observed in the reactant feed consisting of reverse WGS (r-WGS) conditions. In order to understand the intrinsic kinetics of the WGS and to propose a robust rate expression having wider validity, we have developed a plausible microkinetic model for dual site carboxyl mechanism. Using the reaction route analysis (RR) analysis, a robust analytical expression has been developed for the intrinsic rate using the concept of step reversibility. The validity of the kinetic parameters and the rate expression developed has been tested against the experimental data obtained for WGS over r-WGS conditions. From the results obtained, it was found that the formation of carboxyl intermediate is the rate determining step of the system. The CO conversion profile obtained from the simulations predicted the experimentally observed trend to reasonable accuracy even at higher temperatures thus validating the kinetic parameters. In addition to the above, the kinetic parameters also predicted the theoretical equilibrium CO conversion at higher temperatures, thus demonstrating the robustness of the rate expression and kinetic parameters proposed in this study.