Kinetic study of selective CO oxdidation on Au/ Al2O3 catalyst

Abstract

Kinetic study of selective CO oxidation was performed over Au/Al2O3 catalyst prepared using homogeneous deposition-precipitation method. First, the alternative models proposed for the similar catalytic systems in the literature were examined, and the reaction rate equations in terms of elementary reactions were built. Only the single-site mechanisms proceeding on Au surface were considered since the Al2O3 support is belived to be inert for CO oxidation. It was also assumed that the presence of H2, H2O and CO2 in the feed stream affected the rate parameter, but not the reaction mechanism. The rates of CO consumption were evaluated in a microflow reactor operating in differential mode using ten set of CO and O2 concentrations both in the absence and presence of 10 per cent H2O and 25 per cent CO2 for two residence times at the temperatures ranging from 90°C to 130°C. The kinetic parameters were estimated using experimental data for all plausible mechanisms proposed. Finally, the model discrimination was performed for the most plausible models using the experimentally measured and calculated data. The monofunctional mechanism based on the adsorption of O2 and CO on the gold sites seems to represent the experimental data best. Finally, the effects of temperature on the rate of CO consumption was investigated using simplified one-site and power law models at temperatures ranging 90°C to 130°C both in the absence and presence of H2O and CO2, and the activation energies were calculated using Arrhenius plot.