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

In this study, anatase TiO-supported cerium, manganese, and ruthenium mixed oxides (CeO -MnO -RuO /TiO; CMRT catalysts) were synthesized at different calcination temperatures via conventional impregnation methods and used for selective catalytic reduction (SCR) of NO with NH. 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 N selectivity of the CMRT catalysts and further results in an increase in the production of NO and NO 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 Ce, Mn, Ru, and lattice oxygen, which greatly improve the catalyst's ability to activate NO that promotes the NH-SCR reaction. The Ru sites of the CMRT catalyst calcined at 250 °C are the competitive adsorption sites of NO and NH 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).