A study on the structure of tungsten by the addition of ceria: Effect of monomeric structure over W/Ce/TiO2 catalyst on the SCR reaction

Abstract In this study, we investigated the structural characteristics of catalysts and selective catalytic reduction (SCR) reaction activities depending on the Ce valence state and Ce content of the Ce/TiO2 support in order to examine the influence of the W structural characteristics of W/Ce/TiO2 catalyst on SCR reaction. Raman, X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR) were performed in order to investigate the physicochemical characteristics of the catalyst. NH3-temperature programmed desorption (NH3-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) experiments were performed to investigate the reaction characteristics of the catalyst. As a result, SCR reaction activity was excellent when the W structure was present as monomeric W, and that this structure was formed by Ce2(WO4)3 compound, which was a binding species of WO42- monomeric W and Ce3+. In addition, the high Ce4+ ratio of the Ce/TiO2 increased the formation of monomeric W, which was found to be optimal when the loading of Ce was 10 wt.%. Finally, the catalyst having the structure of monomeric W showed higher SCR reaction activity at low temperature because of increased NO adsorption and formation of unstable NOx adsorption species.