Deactivation mechanism of Ca on Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3

Recent progress of low-temperature selective catalytic reduction of NOx with NH3 over manganese oxide-based catalysts

Selective catalytic reduction with NH3 (NH3−SCR) was the most efficient approach to mitigate the emission of nitrogen oxides (NOx). Although the conventional manganese oxide-based catalyst had gradually become a kind...

Deactivation Effect of CaO on Mn-Ce/AC Catalyst for SCR of NO with NH3 at Low Temperature

In this study, the poisoning effect of CaO on activated carbon (AC)-based Mn-Ce catalysts was discussed. Loading CaO inhibited the catalytic activity of the catalyst and the NO conversion of the catalyst decreased from 69.5% to 38.2% at 75 °C. The amount of MnO2 in AC surface decreased in the process of loading CaO, which was detrimental to the Selective Catalytic Reduction (SCR) performance of the catalyst. The change of manganese oxide form inhibited generation rate for the chemisorption oxygen and NO2, which was the most critical reason for the decrease of catalytic activity. Besides, loaded CaO entered into the pores of the catalyst, which led to the blockage of the pores and further resulted in the decrease of the Brunauer-Emmett-Teller (BET) surface area and total pore volume. It also destroyed the oxygen-containing functional groups and acid site on the surface of AC. All of these caused the deactivation of Mn-Ce/AC catalyst after loading CaO.

Enhancement of the activity of Cu/TiO2 catalyst by Eu modification for selective catalytic reduction of NOx with NH3

The Cu/TiO₂ catalysts with the addition of Eu were developed by the sol-gel way for the selective catalytic reduction (SCR) of NO_x by NH₃. Activity tests revealed that CuEu/TiO₂-0.15 catalyst showed the optimal de-NO_x performance in a wide temperature range (150-300 °C), along with an admirable SO₂ tolerance. According to characterization analysis, the relationship between the NH₃-SCR performance and physicochemical characters of samples was explored. The adjunction of Eu on Cu/TiO₂ catalyst can contribute to the formation of a large amount of Cu²⁺, adsorbed oxygen, and acid sites on the catalyst surface. Moreover, the Eu addition on Cu/TiO₂ is favorable to the generation of activated NO_x and NH₃ substances adsorbed on the catalyst surface, which would conduce to the NH₃-SCR process by Langmuir-Hinshelwood (L-H) mechanism effectively.

Effect of CaCO3 on catalytic activity of Fe–Ce/Ti catalysts for NH3-SCR reaction

In the present work, fresh and Ca poisoned Fe–Ce/Ti catalysts were prepared and used for the NH₃-SCR reaction to investigate the effect of Ca doping on the catalytic activity of catalysts. And these catalysts were characterized by BET, XRD, Raman, UV-vis DRS, XPS, H₂-TPR, and NH₃-TPD techniques. The obtained results demonstrate that Ca doping could lead to an obvious decrease in the catalytic activity of catalysts. The reasons for this may be due to the smaller specific surface area and pore volume, the decreased ratio of Fe³⁺/Fe²⁺ and Ce³⁺/Ce⁴⁺, as well as the reduced redox ability and surface acidity.

In the present work, fresh and Ca poisoned Fe–Ce/Ti catalysts were prepared and used for the NH₃-SCR reaction to investigate the effect of Ca doping on the catalytic activity of catalysts.