Kinetics of carbon monoxide oxidation with Sn 0.95 M 0.05 O 2−δ (M = Cu, Fe, Mn, Co) catalysts

Base metal substituted Sn0.95M0.05O2−δ (M = Cu, Fe, Mn, Co) catalysts were synthesized by the solution combustion method and characterized by XRD, XPS, TEM and BET surface area analysis. The catalytic activities of these materials were investigated by performing CO oxidation. The rates and the apparent activation energies of the reaction for CO oxidation were determined for each catalyst. All the substituted catalysts showed high rates and lower activation energies for the oxidation of CO as compared to unsubstituted SnO2. The rate was found to be much higher over copper substituted SnO2 as compared to other studied catalysts. 100% CO conversion was obtained below 225 °C over this catalyst. A bifunctional reaction mechanism was developed that accounts for CO adsorption on base metal and support ions and O2 dissociation on the oxide ion vacancy. The kinetic parameters were determined by fitting the model to the experimental data. The high rates of the CO oxidation reactions at low temperatures were rationalized by the high dissociative chemisorption of adsorbed O2 over these catalysts.