Magnetic resonance studies of ammonia adsorption and decomposition of titania-supported vanadia catalysts
- Lawrence Berkeley Lab., CA (United States)
In-situ proton and deuterion single-resonance NMR techniques were used to study the adsorption and decomposition of ammonia as a function of temperature on a series of V{sub 2}O{sub 5}/TiO{sub 2} catalysts with the weight loading of vanadia ranging from 0 to 6.1 wt % (approximately one monolayer). After analysis of magnetic resonance line shapes, several different molecular species were found to be present on the catalyst surfaces. At low adsorption temperatures on the low-loading samples, the predominant adsorbed species was intact, coordinated ammonia rotating about its C{sub 3} axis. As the weight loading or adsorption temperature was increased, the adsorbed, intact ammonia exhibited an increased H-N-H angle; the total number of protons associated with intact ammonia per gram of sample decreased. At the point where intact ammonia was no longer observed, a new species was observed and assigned to NH{sub 2} moieties. On all samples, ammonium ions were observed at low adsorption temperatures (100{degrees}C) but were found to be easily removed by heating. Their concentration was greater on the higher weight loading samples. The formation of short-lived VOH groups from the protons of dissociated NH{sub 3} was inferred on the higher weight loading samples. Multiple-quantum spin-counting experiments were done to further investigate the nature of the adsorbed species and their groupings on the surfaces. 45 refs., 12 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 229933
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 14 Vol. 114; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temperature-programmed desorption/reaction and in situ spectroscopic studies of vanadia/titania for catalytic reduction of nitric oxide
{sup 15}N NMR study of the adsorption of NO and NH{sub 3} on titania-supported vanadia catalysts