INSITU FT-IR STUDY OF COPPER-CHROMIUM OXIDE CATALYSTS IN CO OXIDATION

CO adsorption and CO oxidation by O2 were studied over alumina-supported copper and copper-chromium oxide from 300 to 673 K. After evacuation at room temperature, Cu+-CO and carbonate-like complexes were observed on copper-containing catalysts upon CO adsorption. Both the copper and the chromium oxide species were easier to reduce on CuO*Cr2O3/Al2O3 compared with CuO/Al2O3 and Cr2O3/Al2O3 owing to the presence of a mixed oxidic phase. CO can react directly from the gas phase with oxygen at the surface under formation of a CO2 surface species as a reaction intermediate. This indicates an Eley-Rideal mechanism. CO2 adsorption results in bands similar to those observed upon CO and upon CO and O2 admission. CO2 inhibits the CO oxidation reaction in two ways - via the more weakly, reversibly bound CO2 and via the more strongly, irreversibly held carbonates.