Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO₂ catalysts on the low-temperature selective catalytic reduction of NO by NH₃

Abstract

TiO 2 -supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wetimpregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH 3 with respect to the Mn valence and lattice oxygen behavior. The surface and bulk properties of these catalysts were examined using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Catalysts prepared using lower calcination temperatures, which contained Mn 4þ , displayed high SCR activity at low temperatures and possessed several acid sites and active oxygen. The TPD analysis determined that the Brönsted and Lewis acid sites in the Mn/TiO 2 catalysts were important for the low-temperature SCR at 80$160 and 200$350 C, respectively. In addition, the available lattice oxygen was important for attaining high NO to NO 2 oxidation at low temperatures.Implications: Recently, various Mn catalysts have been evaluated as SCR catalysts. However, there have been no studies on the relationship of adsorption and desorption properties and behavior of lattice oxygen according to the valence state for manganese oxides (MnO x ). Therefore, in this study, the catalysts were prepared by the wet-impregnation method at different calcination temperatures in order to show the difference of manganese oxidation state. These catalysts were then characterized using various physicochemical techniques, including BET, XRD, TPR, and TPD, to understand the structure, oxidation state, redox properties, and adsorption and desorption properties of the Mn/TiO 2 catalysts.

Characterization and Catalytic Activity of Mn-Co/TiO2 Catalysts for NO Oxidation to NO2 at Low Temperature

“…oxides [19][20][21], have been reported for the low-temperature SCR reaction. As reported in the literature [22,23], Mn oxides not only acted as highly efficient SCR catalysts, but also showed certain catalytic activity for NO oxidation. The Mn-Co/TiO2 catalysts have been evaluated for the low temperature SCR reaction [19].…”

Agastache rugosa alleviates the multi-hit effect on hepatic lipid metabolism, inflammation and oxidative stress during nonalcoholic fatty liver disease

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The Role of Acidity in Terephthalic Acid Synthesis from Renewable Carbon Source

“…The low-temperature desorption peak below 300°C corresponds to the NH 4 + desorbed from Brønsted acid sites, while the Lewis acid-coordinated sites correspond to NH 3 desorbed at higher temperature. [47] In this regard, it is obvious that all samples present higher amounts of Lewis type sites, which have a major influence in oxidation reactions. Indeed, a Lewis acid site can catalyze oxidation reactions by forming an acidbase adduct either with the substrate or with the oxidizing agent, enhancing their reactivity.…”