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- Härelind Ingelsten, Hanna, 1973, et al.
(författare)
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Mechanistic Study of the Influence of the Surface Acidity on Lean NO2 Reduction by Propane in HZSM-5
- 2005
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 232:1, s. 68-79
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the mechanism of lean NO x reduction by propane, over acidic zeolites (HZSM-5), and the influence of surface acidity. In situ FTIR measurements of ammonia adsorption indicate a higher number of Brønsted acid sites for a sample with a low SiO 2 /Al 2 O 3 ratio. The activity for NO x reduction and the selectivity for N 2 formation correlate well with the Brønsted acidity. Step-response experiments with NO 2 and propane show the formation of surface-bound NO + , isocyanate, unsaturated hydrocarbons, and amine species. Formation of the latter two seems to be closely related to the Brønsted acidity. In the NO 2 reaction with propane, the NO + species seem to play a vital role, probably reacting with carbenium ions (from propane cracking) to form isocyanates, which may be hydrolysed to amine species. Step-response experiments with isopropylamine and NO 2 indicate a fast reaction, where the amine and NO + species react over Brønsted acid sites. Hence, amine species are possible reaction intermediates in the lean reduction of NO 2 by saturated hydrocarbons, such as propane, over HZSM-5. © 2005 Elsevier Inc. All rights reserved.
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| 2. |
- Zhao, Dongmei, 1963, et al.
(författare)
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Catalytic and mechanistic study of lean NO2 reduction by isobutane and propane over HZSM-5.
- 2006
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Ingår i: Journal of Molecular Catalysis A: Chemical. - : Elsevier BV. - 1381-1169. ; 249:1-2, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- saturated hydrocarbons, propane and isobutane, has been investigated over acidic zeolite HZSM-5. The activity for NO2 reduction and the selectivity for N-2 formation correlate well with the intracrystalline acidity (Bronsted acid sites) of the zeolite. Isobutane is a more efficient reducing agent than propane due to its tertiary hydrogen being more readily activated than the secondary hydrogen in propane. In situ DRIFT step-response experiments with NO2 and isobutane show formation of surface bound NO+, isocyanate, unsaturated hydrocarbons and amine species. The NO+ species seems to play an important role in the reduction of NO2 probably by reacting with alkenes formed from carbenium ion adsorbates. These species likely form isocyanates, amine species and finally nitrogen.
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