Promotional effects of Zr on K + -poisoning resistance of CeTiO x catalyst for selective catalytic reductionof NO x with NH 3

CeTiO x and CeZrTiO x catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NO x by NH 3 (NH 3 -SCR). Various amounts of KNO 3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K + -poisoning resistance of the CeTiO x catalyst. The NH 3 -SCR performance of the catalysts showed that the NO x removal activity of the Zr-modified catalyst after poisoning was better than that of the CeTiO x catalyst. Brunauer-Emmett-Teller data indicated that the Zr-containing catalyst had a larger specific surface area and pore volume both before and after K + poisoning. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO 2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO 3 was inhibited. The Ce 3 d X-ray photoelectron spectra showed that the Ce 3+ /Ce 4+ ratio of CeZrTiO x decreased more slowly than that of CeTiO x with increasing K + loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH 3 -SCR performance; the temperature-programmed desorption of NH 3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K + -poisoning resistance of the CeTiO x catalyst.