SCR of NO by propene

Zhang, RD Villanueva, A Alamdari, H Kaliaguine, S. SCR of NO by propene over nanoscale LaMni.xCuxOs perovskites, Appl. Catal, A General, 2006, Volume 307, Issue I, 85-97. 

Studies with Au-based catalysts have focused on SCR of NO by propene [61,96,489,492,493], carbon monoxide [78,489,494] and hydrogen [4,5,83,489]. Urea [97], methane [495] and other hydrocarbons [489,496,497] have also been used. SCR using the first three reagents will be discussed here. 

Catalysts containing niobia supported on various oxides have been the subject of considerable recent interest [1-4]. The molecular structures and reactivity of niobium oxides supported on alumina, titania, zirconia and silica have been intensively investigated over the last few years. Niobia supported on silica has been shown to be active for the dehydrogenation and dehydration of alcohols, photo-oxidation of propene and oxidative decomposition of methyl tertiary butyl ether. Titania supported niobia is active for the selective catalytic reduction (SCR) of NO by NH3. 

It is believed that SCR by hydrocarbons is an important way for elimination of nitrogen oxide emissions from diesel and lean-burn engines. Gerlach etal. [115] studied by infrared in batch condition the mechanism of the reaction between nitrogen dioxide and propene over acidic mordenites. The aim of their work was to elucidate the relevance of adsorbed N-containing species for the F>cNOx reaction to propose a mechanism. Infrared experiments showed that nitrosonium ions (NO+) are formed upon reaction between NO, NOz and the Brpnsted acid sites of H—MOR and that this species is highly reactive towards propene, forming propenal oxime at 120°C. At temperatures above 170°C, the propenal oxime is dehydrated to acrylonitrile. A mechanism is proposed to explain the acrylonitrile formation. The nitrile can further be hydrolysed to yield... 

Figure 10.6 shows typical results observed for the NO SCR with n-octane over a supported Pt catalyst. As noted, the NO conversion fairly closely follows hydrocarbon oxidation at low temperature and presents a maximum at intermediate temperature after which combustion of the hydrocarbon with O2 occurs. It can also be observed that appreciable amounts of NgO are formed during NO reduction. Even a lower Ng selectivity is apparently achieved when employing propene as reductant. This relatively poor behavior in terms of Ng selectivity appears independent of the support employed, in spite of the fact that overall NO conversions appear affected by this param-... 

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