Investigation of the effect of Cu addition on the SO2-resistance of a CeTi oxide catalyst for selective catalytic reduction of NO with NH3

A series of characterizations including TEM–EDS, XRD, FTIR, SO2 + O2 TPD, XPS, H2-TPR and NH3-TPD has been carried out to explore the mechanism of the promoting effect of Cu addition on the SO2-resistance of the CeTi oxide catalyst. SO2 had been found to strongly interact with surface cerium oxygen and result in the reduction of Ce4+ to Ce3+ on the CeTi oxide catalyst. The Cu atoms in the CeCuTi oxide catalyst will preferentially interact with SO2 and preserve the adjacent Ce4+. The redox ability of the CeTi catalyst was found to significantly decrease due to the sulfation by SO2. Due to the formation of CuSO4 and the preserved Ce4+, the reducibility of the CeCuTi catalyst has not significantly decreased like the CeTi catalyst but slightly decreased to an adequate level for SCR reaction after sulfation. The surface acidities of CeTi and CeCuTi were both enhanced by sulfation. The preservation of the redox ability and the increase of surface acidity after sulfation had caused CeCuTi to be a high SO2-resistance catalyst for SCR reaction. A graphical description of the effect of the Cu addition on the SO2-resistance of a CeTi oxide catalyst has also been proposed.