A basic comprehensive study on synergetic effects among the metal oxides in CeO2-WO3/TiO2 NH3-SCR catalyst

Two Ce-W-Ti mixed oxide catalysts were prepared by wet impregnation (CeW/Ti-I) and mechanical mixing (Ce/W/Ti-M) methods. CeW/Ti-I catalyst exhibits over 80% NOx conversion and nearly 100% N-2 selectivity at 200-550 degrees C. The superior catalytic performance is associated with the high dispersion of active CeO2 and acidic WO3 on TiO2 and the synergistic effects among different components. The X-ray Diffraction, Raman spectroscopy, Nitrogen physisorption, X-ray photoelectron spectroscopy, H-2 temperature-programmed reduction, temperature-programmed desorption of ammonia and infrared spectroscopy were performed. It is found that the formation of solid solutions, as well as the high specific surface area, would increase the amounts of Ce3+, oxygen vacancies and acid sites in the catalyst. These broaden the operating temperature window of NH3-SCR reaction and enhance the N-2 selectivity by facilitating fast SCR reaction at low temperatures and inhibiting the unselective oxidation of NH3 at high temperatures.

Automated summary

The study found that the formation of solid solutions and high specific surface area in catalysts would increase the amounts of Ce3+, oxygen vacancies, and acid sites, broadening the operating temperature window of NH3-SCR reaction. This enhances N-2 selectivity by promoting fast SCR reaction at low temperatures and inhibiting the unselective oxidation of NH3 at high temperatures.