NOx

About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.

Impact of nitrogen oxides on the environment and human health: Mn-based materials for the NOx abatement

Abstract: An overview is given of the impact of nitrogen oxides on the environment and human health including the low-temperature selective catalytic reduction of NOx by ammonia (NH3-SCR) over manganese-based materials. The review gives a comprehensive overview of NH3-SCR chemistry including the impacts of NOx, stringent regulations, limitations on NOx emissions and aspects of the reaction mechanism over Mn-based catalysts using isotopic labeled and in situ FT-IR studies. The review attempts to correlate catalyst activity and stability with the acidity, manganese oxidation state, surface texture, and structural morphology. Prospectively, low-temperature SCR of NOx over Mn-based catalysts opens up novel views to mitigate NOx and help us design the next generation industrial catalysts.

Improvement of Activity and SO2 Tolerance of Sn-Modified MnOx–CeO2 Catalysts for NH3-SCR at Low Temperatures

Abstract: The performances of fresh and sulfated MnOx–CeO2 catalysts for selective catalytic reduction of NOx by NH3 (NH3-SCR) in a low-temperature range (T < 300 °C) were investigated. Characterization of these catalysts aimed at elucidating the role of additive and the effect of sulfation. The catalyst having a Sn:Mn:Ce = 1:4:5 molar ratio showed the widest SCR activity improvement with near 100% NOx conversion at 110–230 °C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO2. NH3-TPD characterization showed that the low-temperature NH3-SCR activity is well correlated with surface acidity for NH3 adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnOx–CeO2, Sn-modified MnOx–CeO2 showed remarkably improved tolerance to SO2 sulfation and to the combined effect of SO2 and H2O. In the presence of SO2 and H2O, the Sn-modified MnOx–CeO2 catalyst gave 62% and ...

Manganese oxide-based catalysts for low-temperature selective catalytic reduction of NOx with NH3: A review

Abstract: Selective catalytic reduction (SCR) technology has been widely used for the removal of NOx from flue gas. However, it is still a challenge to develop novel low-temperature catalysts for SCR of NOx, especially at temperatures below 200 °C. This paper reviewed the recent progress on the Mn-based catalysts for low-temperature SCR de-NOx with NH3. Catalysts were divided into four categories, single MnOx, Mn-based multi-metal oxide, Mn-based multi-metal oxide with support, and Mn-based monolith catalyst. In the section of single MnOx, the effects of several factors, such as Mn oxidation state, crystallization state, specific surface area and morphology on catalytic activity were systematically reviewed. In the section of multi-metal oxide catalysts, the various roles played by the components of catalysts were intentionally summarized from four aspects, improving de-NOx efficiency, enhancing N2 selectivity, improving resistance to SO2 and H2O, extending operation temperature window, respectively. Moreover, the newly emerging morphology-dependent nanocatalysts were highlighted at the end of this section. In the introduction of supported metal oxide catalysts, the effects of supports were systematically analyzed according to their types, such as Al2O3, TiO2, carbon materials, etc. Considering the actual operation, Mn-based monolith catalysts were also introduced with regard to monolith supports, such as ceramics, metal wire mesh, etc. Subsequently, NH3-SCR mechanisms at low temperature, including E-R and L-H mechanisms, were discussed. At last, the perspective and the future direction of low-temperature SCR of NOx were proposed.