Kwang Hee Park

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

TiO2-supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wet-impregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH3 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 Mn4+, 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/TiO2 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 NO2 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 (MnOx). 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/TiO2 catalysts.

A Study on the Reaction Characteristics of Vanadium-Impregnated Natural Manganese Oxide in Ammonia Selective Catalytic Reduction

ABSTRACT This study investigated the effect of adding vanadium (V) to natural manganese oxide (NMO) in ammonia (NH3) selective catalytic reduction (SCR). The addition of V to NMO decreased the catalytic activity at low temperatures by blocking the active site. However, the enhancement of catalytic activity was achieved by controlling NH3 oxidation at high temperatures. From the NH3 temperature programmed desorption and oxygen on/off test, it was confirmed that the amount of Lewis acid site and active lattice oxygen of the catalyst affects the catalytic performance at low temperature IMPLICATIONS Recently, NMO and manganese oxide have been reported as SCR catalysts. They usually have only reported the reaction characteristics and catalytic activity on the NH3 SCR over NMO or manganese/metal oxide catalysts. There are no studies about the effect of addition of V to NMO. Therefore, this study investigates the catalytic activity and reaction characteristics on the NH3 SCR over NMO and V/NMO, and a new application is proposed based on the conclusions of this study.

Influence of dry ball milling on the mechanochemical synthesis of V 2 O 5 /TiO 2

Among methods of changing variables influencing catalyst activity, mechanochemical treatments is known to change catalyst characteristics. Characterization of catalyst was carried out by XRD, Raman, H2-TPR and XPS. The catalyst increased monomeric species is changed redox characteristic. Accordingly, the mechanochemical method can lower temperature for reoxidation by oxygen, and thus it is believed to inhibit the decline of SCR reaction activity at low temperature.