Mechanistic cause of hydrocarbon specificity over Cu/ZSM-5 and Co/ZSM-5 catalysts in the selective catalytic reduction of NO{sub x}
- Northwestern Univ., Evanston, IL (United States); and others
The nature of adsorbed nitrogen oxide complexes (NO{sub y}) has been identified by FTIR spectroscopy. Nitrito groups are most prominent on Co/ZSM-5. These complexes are stable at 150{degrees}C in He but are reduced upon exposure to either C{sub 3}H{sub 8} or CH{sub 4} leading to the formation of N{sub 2}. Conversely, Cu/ZSM-5 forms nitro and nitrate groups which are stable at 200{degrees}C. At this temperature these complexes are chemically reduced to N{sub 2} upon exposure to CA yet remain inert to CH{sub 4}. At higher temperatures, thermal decomposition yields NO/NO{sub 2}, O{sub 2}, and H{sub 2}O. The specific rate of NO reduction over Cu/ZSM-5 decreases with Cu loading indicating that isolated Cu{sup 2+}{center_dot}NO{sub 2} complexes pay a significant role in the mechanism. The hydrocarbon specificity of these complexes thus matches the known catalytic specificity of NO, reduction over Cu/ZSM-5 and Co/ZSM-5. The mechanistic cause for the catalytic specificity of the ZSM-5 hosted metals in NO, reduction thus is traced back to the structure and reactivity of the specific NO{sub y} adsorption complexes which these metals produce upon interacting with NO + O{sub 2}. The consumption of CH{sub 4} when feeds containing NO, CH{sub 4} and O{sub 2} are exposed to Cu/ZSM-5 can be attributed to nonselective combustion with adsorbed oxygen and not to reactions with NO{sub y}. 26 refs., 8 figs., 3 tabs.
- OSTI ID:
- 223993
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 158; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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