Effect of zirconium on the structure and activity of Cu/Ti1−xZrxO2 catalysts for selective catalytic reduction of NO with C3H6

Abstract

Mixed oxides of 5 wt% Cu/Ti1−xZrxO2 (x = 0, 0.3, 0.5, 0.7, 1.0) were synthesized using the impregnation–urea coprecipitation method and the catalysts prepared were assessed for the selective catalyst reduction (SCR) of NO with C3H6. A significant improvement of the catalytic activity was found over the Zr-doped catalysts with the highest N2 yield of 67.2% achieved over Cu/Ti0.7Zr0.3O2 at 275 °C. Based on the characterizations using BET, ICP, XRD, H2-TPR, FTIR of adsorbed pyridine, XPS, and TEM, the enhanced SCR activity of Cu/Ti0.7Zr0.3O2 was attributed to the large surface area, appropriate structural disorder, abundant Lewis acid sites, increase in the amount of active sites, and greater lattice oxygen mobility. The specific physico-chemical properties were caused by the distortion of the crystal structure and the change of the electron charge density (ECD) due to the introduction of Zr species. The generation of mixed Ti–O–Zr bond was beneficial for the adsorption of NO and the oxidation of NO to NO2, which favored the SCR reaction.