Improving the K resistance effectively of CeO2-TiO2 catalyst by Nb doping for NH3-SCR reaction

The role of Nb doping in improving anti-K poisoning ability of CeO2-TiO2 catalyst was investigated by SCR activity evaluation, BET, XRD, XPS, NH3-TPD, H2-TPR and in situ DRIFTs. The catalytic activity of the Nb-modified CeO2-TiO2 catalyst was vastly superior to that of the CeO2-TiO2 catalyst in the presence of K. The doping of Nb could enhance the BET surface area and alleviate the surface crystallinity of the CeO2-TiO2 catalyst both before and after the introduction of K. In addition, the smaller decrease in the ratio of Ce3+/Ce4+, surface chemisorbed oxygen, Brønsted acidity and redox property was observed on the Nb-modified CeO2-TiO2 catalyst in the presence of K. The results of in situ DRIFTs indicated that all of the reactions were controlled by combined E-R and L-H mechanisms on the fresh and K-poisoned catalysts. The addition of Nb could enhance the adsorption of NO and NH3, but not all NOx adsorbed species were reactive in the NH3-SCR reaction for K-poisoned CeO2-TiO2. All the above factors contributed to enhance its K-poisoning resistance of CeO2-TiO2 due to the doping of Nb.