CO oxidation and oxygen-assisted CO adsorption/desorption on Ag/MnO x catalysts

Abstract

A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid medium. The surface structure of the catalysts was characterized by N 2 adsorption, XRD and TEM experiments. The catalysts showed excellent catalytic activity for CO oxidation. The adsorption and oxidation of CO on a 1.0% Ag/MnO x catalyst between 393 and 493 K were studied by means of single pulse experiments in a TAP reactor. The adsorption of CO was reversible at these temperatures and CO 2 was formed in an oxidation reaction of CO and lattice oxygen. Curve fitting to the experimental TAP response curves of the reactant and product was used to determine the kinetic parameters for the elementary steps. The activation energies were 83 kJ/mol for CO desorption, 31 kJ/mol for CO 2 desorption, and 116 kJ/mol for the surface CO oxidation by lattice oxygen. In addition, the effect of coadsorbed O 2 on CO adsorption was studied by the TAP technique. Below 353 K, there was a sharp increase, by about one order of magnitude, in the rate constant of CO adsorption promoted by the presence of coadsorbed O 2.