Effect of Calcination Temperature on the Activation Performance and Reaction Mechanism of Ce-Mn-Ru/TiO₂ Catalysts for Selective Catalytic Reduction of NO with NH₃.

ABSTRACT: In this study, anatase TiO₂-supported cerium, manganese, and ruthenium mixed oxides (CeO _x -MnO _x -RuO _x /TiO₂; CMRT catalysts) were synthesized at different calcination temperatures via conventional impregnation methods and used for selective catalytic reduction (SCR) of NO _x with NH₃. The effect of calcination temperature on the structure, redox properties, activation performance, surface-acidity properties, and catalytic properties of the CMRT catalysts was investigated. The results show that the CMRT catalyst calcined at 350 °C exhibits the most efficient low-temperature (<120 °C) denitration activity. Moreover, the selective catalytic oxidation (SCO) reaction of ammonia is intensified when the reaction temperature is >200 °C, which leads to a decrease in the N₂ selectivity of the CMRT catalysts and further results in an increase in the production of NO and N₂O byproducts. X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy show that the CMRT catalyst calcined at 350 °C contains more Ce⁴⁺, Mn⁴⁺, Ru⁴⁺, and lattice oxygen, which greatly improve the catalyst's ability to activate NO that promotes the NH₃-SCR reaction. The Ru ⁿ⁺ sites of the CMRT catalyst calcined at 250 °C are the competitive adsorption sites of NO and NH₃ molecules, while those of the CMRT catalyst calcined at 350 and 450 °C are active sites. Both the Langmuir-Hinshelwood (L-H) mechanism and the Eley-Rideal (E-R) mechanism occur on the surface of the CMRT catalyst at the low reaction temperature (100 °C).

SUBMITTER: Ren Z 

PROVIDER: S-EPMC7774282 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature