Selective catalytic reduction of nitric oxide by methane in the presence of oxygen over CaO catalyst
- Univ. of Patras (Greece). Dept. of Chemical Engineering
- Univ. of Cyprus, Nicosia (Cyprus). Dept. of Natural Sciences
The selective catalytic reduction of nitric oxide by methane in the presence of oxygen was studied over CaO catalyst in the temperature range 550--850 C. The nitric oxide conversion-versus-temperature profile was found to depend on oxygen feed concentration, while the selectivity to N{sub 2} formation was found to be 100% and independent of oxygen feed concentration in the range 1--10 mol%. The kinetic study has shown that the reaction order with respect to NO and CH{sub 4} is 1.0 and 0.5, respectively. On the other hand, the reaction order with respect to O{sub 2} was found to be slightly positive for O{sub 2} feed concentrations up to 1 mol% and slightly negative at higher concentrations. The apparent activation energy of the reaction in the presence of oxygen was found to be 14.6 kcal/mol. The addition of 2.5 mol% CO{sub 2} and 5 mol% H{sub 2}O in the feed stream had a considerable inhibiting effect on NO conversion in the range 550--650 C, while a small inhibiting effect of CO{sub 2} and a positive effect of H{sub 2}O were observed in the range 700--850 C. Temperature-programmed desorption (TPD) of NO revealed the presence of two well-resolved NO peaks in the temperature range 250--650 C, a behavior also observed during a temperature-programmed oxidation experiment under O{sub 2}/He flow. However, during temperature-programmed surface reaction under CH{sub 4}/He flow the NO desorption spectrum showed a significant shift of the stronger adsorbed NO species toward lower temperatures. Preadsorbed CO{sub 2} on the CaO surface was found to largely affect the chemisorption of NO and its desorption kinetics during TPD. The amount of deposited carbon-containing species on the catalyst surface during reaction was determined with transient titration experiments and it was found to be small.
- OSTI ID:
- 350260
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 183; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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