Enhancement of the low-temperature activity of Ce/TiO2 catalyst by Sm modification for selective catalytic reduction of NOx with NH3

Abstract

CeSmOx mixed oxide catalysts supported on TiO2 prepared by coprecipitation method were used for selective catalytic reduction of NOx with NH3. The results showed that the addition of Sm could effectively enhance the low-temperature SCR activity and SO2/H2O resistance of Ce/TiO2 catalyst, and the appropriate mole ratio of Sm to Ce was 0.3. Characterization results indicated that the introduction of Sm could promote the formation of Ce3+ and chemisorbed oxygen species on catalyst surface, which was favorable to the generation of NO2. Moreover, the doping of Sm could also promote the adsorption of NH3 and NOx species on Ce/TiO2 catalyst. The results of in situ DRIFT study revealed that the NH3-SCR reaction over CeSm/TiO2-0.3 catalyst was mainly controlled by the Langmuir−Hinshelwood mechanism in the low temperature range (<200°C). Thereafter, the promoted NO oxidation and the enhanced NH3 adsorption should play a major role for the excellent low-temperature SCR performance of CeSm/TiO2-0.3 catalyst.