Isotopic study of NO{sub x} decomposition over Cu- or Co-exchanged ZSM-5 zeolite catalysts
- SRI International, Menlo Park, CA (United States)
The decomposition of NO{sub x} over Cu{sup 2+}- and Co{sup 2+}-exchanged ZSM-5 zeolites was investigated using isotope labeled {sup 15}N{sup 18}O and temperature-programmed desorption (TPD) technique. The authors found that formation of NO{sub 2} intermediates is responsible for enhancing the rate of NO{sub x} decomposition when the catalysts were treated in both {sup 15}N{sup 18}O and O{sub 2}. Co-adsorption of {sup 15}N{sup 18}O and O{sub 2} led to a dramatic increase in the amount of NO{sub x} and O{sub 2} adsorbed. The surface NO{sub x} species decomposed or desorbed to form NO, O{sub 2}, N{sub 2}, and NO{sub 2} during the TPD. This results in formation of equal amounts of {sup 15}N{sup 16}O and {sup 15}N{sup 18}O in NO products and 50% {sup 15}N{sup 16}O {sup 18}O, 25% {sup 15}N{sup 16}O{sub 2}, and 25% {sup 15}N{sup 18}O{sub 2} in NO{sub 2} products. In the absence of O{sub 2}, formation of N{sub 2}O was observed at <300{degrees}C but not NO{sub 2}. For Cu-NaZSM-5, its N{sub 2}O products are exclusively {sup 15}N{sub 2}{sup 18}O, suggesting that lattice oxygen is not involved in the formation of N{sub 2}O (it is derived solely from {sup 15}N{sup 18}O) and the isotope exchange between {sup 15}N{sub 2}{sup 18}O with the zeolite lattice oxygen ({sup 16}O) is not significant. However, for Co-ZSM-5, formation of either N{sub 2}O or NO{sub 2} is negligible with {sup 15}N{sup 18}O treatment. 17 refs., 10 figs., 3 tabs.
- DOE Contract Number:
- FG03-94ER81772
- OSTI ID:
- 476834
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 165; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
Similar Records
Decomposition of NO over [Co]-ZSM-5 zeolite: Effect of co-adsorbed O{sub 2}
The high dispersion of CuCl{sub 2} in ZSM-5 by using microwave method