Study of a Fe–zeolite-based system as NH3-SCR catalyst for diesel exhaust aftertreatment

Emissions of Regulated Pollutants and PAHs from Waste-cooking-oil Biodiesel-fuelled Heavy-duty Diesel Engine with Catalyzer

“…The mean increases of NO x (ULSD = 5.21 g/BHP-hr) were 0.384%, 0.960%, 0.960%, and 1.15% for WCOB5, WCOB10, WCOB20, and WCOB30, respectively, when compared with the NO x value for ULSD. The problem of high NO x emissions from biodiesel-diesel engines can be mitigated by the use of low-temperature combustion or selective catalytic reduction (He and Yu, 2005;Kelly et al, 2006;Ciardelli et al, 2007;Dong et al, 2008;Fang et al, 2008;Grossale et al, 2008).…”

Kinetic Modeling of Dynamic Aspects of the Standard NH3-SCR Reaction Over V2O5-WO3/TiO2and Fe-Zeolite Commercial Catalysts for the Aftertreatment of Diesel Engines Exhausts

“…The presented models implement kinetic schemes derived from an extensive investigation of reactivity, chemistry and catalytic mechanism of all the main SCR reactions over commercial V 2 O 5 -WO 3 /TiO 2 and Fe-zeolite catalysts performed in our laboratories during the last few years [2][3][4][5][6][7][8][9][10][11][12][13][14].The related rate expressions were fitted to transient data collected over powdered catalysts in the chemical regime, and in their global form allow the kinetic analysis of the full NH 3 -NO/NO 2 SCR reacting system.…”

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

“…Previously, Long and Yang [20,24] studied the influence of Si/Al ratio on SCR activity over Fe-ZSM-5 catalysts and found that the NO conversion was increased with the decrease of the Si/Al ratio. They considered that the increase of SCR activity of Fe-ZSM-5 with low Si/Al ratio corresponded to the enhancement of Brønsted acidity induced by aluminium sites (Al-OH), since the NH 4 + species adsorbed on Brønsted acid sites directly participated in the SCR reaction to reduce NO x [20,24]. However, recent studies reached some different conclusions on the roles of acid sites of Fe-ZSM-5 catalysts for the NH 3 -SCR reaction.…”

“…Due to the different Cu species and surface acidity of the parent zeolites, there are also various reaction pathways and reaction intermediates reported in the literature. For example, Richter et al [84] concluded that the NH 4 + species formed on Brønsted acid sites were responsible for the conversion of NO x to N 2 , and the oxidation of NO to NO 2 was the rate-limiting step over metal-exchanged zeolite catalysts. Sjövall et al [12] reported that the NH 3 -SCR mechanism over Cu-ZSM-5 catalysts involved reactions between adsorbed NO 2 and NH 3 , the formation of HNO 2 and HNO 3 and their final reduction to N 2 and H 2 O. Grossale et al [76] reported that surface nitrates played a key mechanistic role over Cu-zeolites in the presence of NO 2 via NO 2 disproportionation.…”

“…The first commercial NH 3 -SCR catalysts were vanadium-based materials, which have been applied in stationary deNO x systems [4]. However, many problems exist when vanadium-based catalysts are used for diesel emission control, mainly owing to the toxicity of the V 2 O 5 active phase, the poor thermal stability of TiO 2 and the easy sublimation of V 2 O 5 [5].…”