Temperature-programmed desorption of hydrogen from platinum particles on {gamma}-Al{sub 2}O{sub 3}: Evidence of platinum-catalyzed dehydroxylation of {gamma}-Al{sub 2}O{sub 3}
- Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science
- Ford Motor Co., Dearborn, MI (United States)
Samples of Pt on {gamma}-Al{sub 2}O{sub 3} were prepared by reduction in H{sub 2} at 400 C of [PtCl{sub 2}(PhCN){sub 2}], adsorbed intact from n-pentane solution onto {gamma}-Al{sub 2}O{sub 3} powder that had been partially dehydroxylated under vacuum at 400 C. The Pt dispersion was determined to be about 0.58 by standard methods, namely, chemisorption of hydrogen, of oxygen, and of CO, titration of chemisorbed oxygen with hydrogen, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The supported Pt particles were resistant to sintering in the presence of O{sub 2} at temperatures up to 400 C, as shown by chemisorption and EXAFS data, but the latter indicated that a combination of O{sub 2} and H{sub 2} treatments at 200--400 C led to changes in particle morphology. The samples were investigated by temperature-programmed desorption (TPD) of preadsorbed hydrogen; a TPD peak centered at 120 C represents hydrogen adsorbed on Pt and confirms the value of 0.58 for the dispersion. TPD of preadsorbed H{sub 2} gave evidence of a second desorption peak, at 580 C, which was always accompanied by desorption of water at the same temperature; its presence was found to depend chiefly on the sample reduction temperature and evacuation time (it was absent when there was no Pt on the {gamma}-Al{sub 2}O{sub 3}). The desorption of H{sub 2} or D{sub 2} that had been adsorbed on Pt/{gamma}-Al{sub 2}O{sub 3} reduced with D{sub 2} or H{sub 2}, respectively, shows that hydrogen species desorbed at about 580 C originate from water (hydroxyl) species as a result of Pt-catalyzed decomposition.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-89ER45384; AC02-76CH00016
- OSTI ID:
- 684574
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 185; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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