Reduction of NO by hydrocarbons

Shimizu, K Satsuma, A Hattori, T. Selective catalytic reduction of NO by hydrocarbons on Ga203/Al203 catalysts, A/ip/. Catal, B Environmental, 1998, Volume 16, Issue 4, 319-326. 

The effect of SO2 poisoning was investigated both for the decomposition of NO and for its reduction over Cu/ZSM-5 (349). It was found that the catalytic activity for NO decomposition completely disappeared after addition of SO2. In contrast, the catalytic activity for NO reduction by propylene in the presence of O2 was only slightly lowered by the presence of SO2. This result suggests that selective reduction of NO by hydrocarbons has potential for practical applications. The O2 concentration is important for maintaining a high activity level, in particular in the presence of sulfur. O2 addition initially increases the N2 yield, but at higher O2 concentration the yield decreases. 

Sulfur Tolerance of Cu-and H-mordenite Zeolite Catalysts for the Reduction of NO by Hydrocarbons... 

Selective catalytic reduction (SCR) of NO, by hydrocarbons is under investigation as an alternative NO, removal technology. NO reduction by NHj is presently the commercial state-of-the-art technology available for reducing NO, from stationary sources and from the exhausts of lean-bum gasoline and diesel engines. A number of catalysts for the selective reduction of NO by hydrocarbons have been examined in previous studies [1-18], Transition metal ion-exchang zeolite catalysts such as mordenite and ZSM-5 are the most effective SCR catalysts. 

The possible role of isocyanate species in the reduction of NO by hydrocarbons over Cu/Cs on alumina catalysts has been reported [98]. Water inhibits the formation of isocyanate species. This effect is very small if ethyne or -heptane are the reductants. The isocyanate species were detected by means of infrared spectroscopy. The isocyanate band appeared at 2234 cm . ... 

The selective reduction of NO by hydrocarbon in an excess of oxygen was studied using a platinum catalyst doped or not with zinc. Successive impregnetion or co-impregnation of Pt and Zn on alumina were made. In some cases, in the presence of Zn, the NO conversion is increased in parallel with N2 formation. A better conversion of hydrocarbons was also observed. EXAFS experiments and N2O decomposition experiments have been carried out to explain these observations. 

The selective reduction of NO by hydrocarbons in oxygen rich atmosphere has been reported for zeolite-based catalysts, especially Cu-ZSM-5 solids (1), but their low thermal stability limits their use for treatment of emissions from Diesel and lean-bum engines. An... 

Iwamoto et al. [1, 2, 3] and Held et al. [4] independently reported tliat the selective catalytic reduction of NO by hydrocarbons, such as ethene, propene. 

Low-Temperature Selective Catatytic Reduction of NO by Hydrocarbons in the Presence of O2 and H2O... 

Wang, X. Chen, H.-Y. and Sachtler, W. M. H., Catalytic reduction of NO, by hydrocarbons over Co/ZSM-5 catalysts prepared by different methods, Applied Catalysis, B Environmental 26(4), L227-L239 (2000). 

The Cu-exchanged zeolite ZSM-5 revealed a particularly high and steady activity for the direct catalytic conversion of NO into N2 and O2 ( DeNOx activity) [8612]. The same system is also active for the selective catalytic reduction of NO by hydrocarbons in the presence of excess oxygen [95 S2, 96T1 ]. 

The selective catalytic reduction of NO by hydrocarbons over metal oxides, such us perovkite-type oxides, has attracted much attention nowadays as promising alternatives to noble metal-supported catalysts. A representative TWC reaction for the NO reduction by hydrocarbons is the NO + CsHe, which is widely investigated in several perovskites (Table 25.5). 

Hamada, H. Selective reduction of NO by hydrocarbons and oxygenated hydrocarbons over metal oxide catalysts. Catal. Today 1994, 22, 21 0. 

Evidence has been presented for the formation of surface Cu-NCO species as intermediates in the reduction of NO by hydrocarbons with H2O on mordenite-type zeolite catalysts." The complex [Cu(NCS)(p-NCS)(Hmtpo)(H20)]2, where Hmtpo = 4, 7 -5-methyl-7-oxo[l,2,4]-triazolo-[l,5-a]pyrimidine, has VasNCO at 2144 and 2110 cm due to symmetric and asymmetric bridged thiocyanato groups respectively. ... 

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