Enhancement of Activity and Sulfur Resistance of CeO2 Supported on TiO2-SiO2 for the Selective Catalytic Reduction of NO by NH3

A series of novel metal-oxide-supported CeO2 catalysts were prepared via the wet impregnation method, and their NH3-SCR activities were investigated. The Ce/TiO2-SiO2 catalyst with a Ti/Si mass ratio of 3/1 exhibited superior NH3-SCR activity and high N-2 selectivity in the temperature range of 250-450 degrees C. The characterization results revealed that the activity enhancement was correlated with the properties of the support material. Cerium was highly dispersed on the TiO2-SiO2 binary metal oxide support, and the interaction of Ti and Si resulted in greater conversion of Ce4+ to Ce3+ on the surface of the catalyst compared to that on the single metal oxide supports. As a result of in the increased number of acid sites on Ce/TiO2-SiO2 that resulted from the addition of SiO2, the NH3 adsorption capacity was significantly improved. All of these factors played significant roles in the high SCR activity. More importantly, Ce/TiO2-SiO2 exhibited strong resistance to SO2 and H2O poisoning. After the addition of SiO2, the number of Lewis-acid sites was not decreased, but the number of Bronsted-acid sites on the TiO2-SiO2 carrier was increased. The introduction of SiO2 further weakened the alkalinity over the surface of the Ce/TiO2-SiO2 catalyst, which resulted in sulfate not easily accumulating on the surface of the Ce/TiO2-SiO2 catalyst in comparison with Ce/TiO2.