Kinetics of low temperature co oxidation over activated carbon supported Pt-SnOx catalysts

Abstract

This experimental study comprises a kinetic study of low-temperature CO oxidation both in the absence and presence of H2 over air-oxidized activated carbon supported 1wt.%Pt-0.25wt.%SnOx catalyst prepared by the sequential impregnation method. Kinetic experiments were conducted at 383 K and atmospheric pressure, and different sets of CO and O2 concentrations each at different space times and catalyst loadings were used. Molar reactant concentrations in the feed were varied between 1-10 per cent CO and 1-4 per cent O2 in the absence of hydrogen. The effect of the presence of H2 in the feed on CO oxidation rates was also investigated. In preferential CO oxidation experiments, the H2 concentrations used were between 10-45 per cent. Experimental rate data were used to estimate kinetic parameters of the power law model by using the method of initial rates. The investigation of power law kinetics gave reaction orders of 0.87 and 0.13 with respect to carbon monoxide and oxygen, respectively, and a reaction rate constant of 1.37 μmol.mg-1.min-1.atm-1 at 383 K. The variance of experimental error was found to be 0.017 (μmol.g-1.s-1)2 for this rate expression, and the agreement between experimentally measured and model predicted rates was good. Finally, the addition of H2 to the feed did not alter reaction kinetics, but an almost four fold enhancement was observed in CO oxidation rates over 1wt.%Pt-0.25wt.%SnOx/AC2 at all the feed H2 concentrations studied.