Peng Sun,Rui-tang Guo,Shu-ming Liu,Shu-xian Wang,Wei-guo Pan,Ming-yuan Li,Shuai-wei Liu,Jian Liu,Xiao Sun
CeSmOx mixed oxide catalysts supported on TiO 2 prepared by coprecipitation method were used for selective catalytic reduction of NOx with NH 3 . The results showed that the addition of Sm could effectively enhance the low-temperature SCR activity and SO 2 /H 2 O resistance of Ce/TiO 2 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 Ce 3+ and chemisorbed oxygen species on catalyst surface, which was favorable to the generation of NO 2 . Moreover, the doping of Sm could also promote the adsorption of NH 3 and NOx species on Ce/TiO 2 catalyst. The results of in situ DRIFT study revealed that the NH 3 -SCR reaction over CeSm/TiO 2 -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 NH 3 adsorption should play a major role for the excellent low-temperature SCR performance of CeSm/TiO 2 -0.3 catalyst.
Shu-xian Wang,Rui-tang Guo,Wei-guo Pan,Ming-yuan Li,Peng Sun,Shu-ming Liu,Shuai-wei Liu,Xiao Sun,Jian Liu
It was well recognized that Pb had a poisoning effect on a SCR catalyst. In this study, the deactivation mechanism of Pb on the Ce/TiO2 catalyst was investigated based on the characterization results of TPD and in situ DRIFT studies. It was found that the addition of Pb on the Ce/TiO2 catalyst not only inhibited the adsorption and activation of NH3 species, but also led to the decrease of the activity of adsorbed NH3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O2 over the Ce/TiO2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO2 species did not decrease. Moreover, the results revealed that the NH3-SCR reaction over the Ce/TiO2 catalyst followed both the E–R and L–H mechanisms, while the NH3-SCR reaction over Ce/TiO2-Pb was mainly controlled by the L–H mechanism. The contributions of the L–H mechanism to the SCR reactions over Ce/TiO2 and Ce/TiO2-Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO2-Pb was mainly attributed to the suppressed NH3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.
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