Reduction of NO{sub x} over Fe/ZSM-5 catalysts: Adsorption complexes and their reactivity toward hydrocarbons
- Northwestern Univ., Evanston, IL (United States)
Fe/ZSM-5 prepared via sublimation catalyzes the reduction of NO{sub x} to N{sub 2} in the presence of excess O{sub 2} and H{sub 2}O. Propane, isobutane, and propene are active reductants; methane is inactive. The NO{sub x} reduction rate is negligible in the absence of O{sub 2}; it increases steeply with P{sub O{sub 2}} and passes through a maximum. The equilibrium between NO + O{sub 2} and NO{sub 2} is swiftly established over a clean catalyst, but deposits impede this reaction. NO + O{sub 2} forms chemisorption complexes, NO{sub y}, with y {ge} 2. Upon their reaction with hydrocarbon, a nitrogen-containing deposit is formed on the catalyst. It reacts with NO{sub 2}, but not with NO, releasing large quantities of N{sub 2}. N{sup 2}O seems not to be a precursor of N{sub 2}. Isotopic labeling shows that one N atom in every N{sub 2} comes from the deposit; the other comes from NO{sub 2}. Less deposit is formed with propane, more with propene. As deposits also block catalyst sites, the rate limiting step in NO{sub x} reduction depends on the nature of the hydrocarbon. Deposits are oxidized by O{sub 2} and volatilized by H{sub 2}O at high temperature; these processes contribute to the relative efficiency of different hydrocarbons in NO{sub x} reduction over Fe/ZSM-5.
- OSTI ID:
- 316309
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 180; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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