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 TiO 2 -supported cerium, manganese, and ruthenium mixed oxides (CeO x −MnO x −RuO x / TiO 2 ; CMRT catalysts) were synthesized at different calcination temperatures via conventional impregnation methods and used for selective catalytic reduction (SCR) of NO x with NH 3 . 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 lowtemperature (<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 2 selectivity of the CMRT catalysts and further results in an increase in the production of NO and N 2 O 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 4+ , Mn 4+ , Ru 4+ , and lattice oxygen, which greatly improve the catalyst's ability to activate NO that promotes the NH 3 -SCR reaction. The Ru n+ sites of the CMRT catalyst calcined at 250 °C are the competitive adsorption sites of NO and NH 3 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).

Synthesis and Characterization of Titanium Dioxide Hollow Nanofiber for Photocatalytic Degradation of Methylene Blue Dye

“…The crystallite size of THNF increased from 15.67, 21.45 to 30.03 nm as the calcination temperature increased. Higher calcination temperature had reduced the activation energy, thus promoting the crystal growth rate [ 27 ]. It was commonly known that the surface area is inversely proportional to the crystallite size because there is a greater proportion of crystals and more area to occupy [ 28 ].…”

Ce–Mn Oxide Nanocomposites for Catalytic Removal of H2S

“…In view of that Ce 4+ in octahedral anti-prismatic configuration shares structural similarity with Mn 3+ in distorted octahedral configuration, and the radius of Ce 4+ is larger than that of Mn 3+ , the incorporation of Ce 4+ into MnO 2 would induce the distortion of the crystal lattice and create more defects, which modulates the surface acidity, oxygen mobility, and redox property of catalysts. , Moreover, the formation of uniform Ce–Mn solid solution favors the dispersion of active sites on the surface and the enhancement of porosity . In the light of the advantages of Ce–Mn composite oxides, their catalytic performance has been explored in various applications, such as high-temperature gasifier effluent desulfurization, adsorption of mercury, and catalytic reduction of NO with NH 3 . It is found that the catalytic performance of Ce–Mn composite oxides was generally related to the valence state of Mn, Ce, and the distribution of oxygen species, which could be tuned by regulating the composition ratios or constructing a core–shell structure. , However, the synergistic effect of Ce–Mn on the catalytic activity and selectivity of the H 2 S-SCO reaction is yet to be revealed.…”

Shear Stress on the Structure Control of a Supported Fly Ash‐Based Catalyst and Its Application in SCR* Denitration

“…It is gradually applied in flue gas denitration. [16] In recent years, fly ash combined with other substances as a denitration carrier has been studied by scholars in recent years. When fly ash is used as a carrier for denitration without modification, the denitration efficiency is relatively low, mainly due to the lack of effective active components.…”

“…Fly ash has a wide range of sources and has certain physical properties. It is gradually applied in flue gas denitration [16] . In recent years, fly ash combined with other substances as a denitration carrier has been studied by scholars in recent years.…”