Promotional effect of Zr on thermal stability of CeTiOx monolith catalyst for selective catalytic reduction of NOx with ammonia

CeTiOx and CeZrTiOx catalysts were prepared by co-precipitation method and used for selective catalytic reduction of NOx by NH3 (NH3-SCR). Thermal aging of the two catalysts was conducted at various temperatures to investigate the effect of Zr on thermal stability of CeTiOx catalyst. The NH3-SCR performance of the catalysts showed that the Zr-modified catalyst exhibited better activity and N2 selectivity than CeTiOx catalyst after high temperature aging at 650, 750 and 850 °C. The XRD, Raman and H2-TPR results illustrated that the addition of Zr could prevent Ce species from sintering and inhibit the formation of rutile TiO2. The SEM images of the catalysts revealed that the aggregation of the particles with increasing calcination temperature could be inhibited by addition of Zr. From the XPS spectra of Ce3d, the ratio of Ce3+/Ce4+ of CeTiOx decreased more sharply than that of CeZrTiOx with the aging temperature, meaning that more crystal defects and oxygen vacancies were preserved after Zr addition, which led to increased catalytic performance. In addition, NH3-TPD results implied that modified catalyst possessed larger amounts of Brönsted acid sites after calcining at a same temperature, improving the activity and inhibiting the NH3 oxidation. Thus, a conclusion could be drawn that Zr addition improved the thermal stability of the CeTiOx catalyst.

Duke Scholars

Author Li Lan Molecular Genetics and Microbiology