Simplified kinetic models of methanol oxidation on silver

Recently the authors developed a microkinetic model of methanol oxidation on silver [A. Andreasen, H. Lynggaard, C. Stegelmann, P. Stoltze, Surf. Sci. 544 (2003) 5-23]. The model successfully explains both surface science experiments and kinetic experiments at industrial conditions applying physically realistic parameters. Unfortunately the rate expression based on this microkinetic model is complex and impractical to apply for reactor engineering purposes. In this paper the rate expression is simplified by a number of approximations to make it suitable for practical applications without loosing significant accuracy. This is achieved by converting from a statistical thermodynamic description to a classical thermodynamic description resulting in a reduction of model parameters from more than 100 to a total of only 26. Further, other assumptions are applied including the most abundant reaction intermediate (MARI) approximation and the irreversible step (IS) approximation. This leads to further reduction in model complexity and in number of parameters. Computations verify that the performance of the model is preserved despite the reduction of the vast amount of parameters.