Selective catalytic reduction

About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.

Catalytic Reduction of Nitrogen Monoxide by Methane over Palladium-Loaded Zeolites in the Presence of Oxygen

Abstract: Palladium ion-exchanged H-ZSM-5 showed a high catalytic activity for the removal of dilute nitrogen monoxide in the presence of methane and oxygen at 350–550 °C. The presence of palladium and (protonic) acidity is essential for the high activity.

Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method

Abstract: A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

IR spectroscopic study of NOxadsorption and NOx–O2coadsorption on Co2+/SiO2catalysts

Abstract: Adsorption of nitrogen oxides (NO, NO2) and their coadsorption with oxygen on Co2+/SiO2 samples has been investigated by IR spectroscopy with a view to elucidating the mechanism of selective catalytic reduction (SCR) of NOx with hydrocarbons. A Co2+/SiO2 sample synthesized by ion exchange is characterized by a highly dispersed cobalt and a very weak surface acidity: CO is adsorbed only at low temperature (100 K) forming Co2+–CO carbonyls [ν(CO) = 2180 cm−1]. Adsorption of NO on Co2+/SiO2 leads to the formation of Co2+(NO)2 dinitrosyl complexes (1872 and 1804 cm−1) which are decomposed upon evacuation. Adsorption of NO2, as well as coadsorption of NO and O2, produce NO2 species weakly bound to the support (a band at 1681 cm−1) and N2O4 (a band at 1744 cm−1 with a shoulder at 1710 cm−1), the latter being adsorbed reversibly on both the support and the Co2+ ions. In the second case N2O4 is transformed into surface monodentate nitrates of Co2+ (a band at 1550–1526 cm−1) and partly into bridged nitrates (a band at ca. 1640 cm−1). The monodentate nitrates are stable with respect to evacuation up to 125 °C and act as strong oxidising agents: they are reduced by NO, even at room temperature, and by methane at 100 °C. In the latter case, organic nitro-compounds and isocyanate groups are registered as reaction products (probably intermediate compounds in SCR). The surface species obtained after NO and NO2 adsorption on Co2+/SiO2 prepared from cobalt acetate (active SCR catalyst) are essentially the same as those observed with the ion-exchanged sample. No monodentate nitrates, however, are formed during NO2 adsorption on a Co2+/SiO2 sample synthesized by impregnation with cobalt nitrate, which accounts for the lack of activity of this sample in the SCR.

NOx aftertreatment system and method for internal combustion engines

Abstract: A very high efficiency NO X aftertreatment system is provided for use in lean burn engines. A lean NO X adsorber is synergistically combined with a selective catalytic reduction catalyst to use the ammonia formed within the NO X adsorber, during regeneration of the NO X adsorber while periodically operating the engine in a fuel-rich combustion mode, to reduce NO X remaining in the exhaust gas stream after passage through the NO X adsorber during normal operation of the engine in a lean burn combustion mode.

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

Abstract: Newly designed and prepared vanadium complexes bearing anionic pyrrole-based PNP-type pincer and aryloxy ligands were found to work as effective catalysts for the direct conversion of molecular dinitrogen into ammonia and hydrazine under mild reaction conditions. This is the first successful example of vanadium-catalyzed dinitrogen reduction under mild reaction conditions.