Support-metal interaction studies on model supported catalysts. Final report
Support-metal interactions have been studied by incorporating silica, alumina, titania, and niobia into the surface of a clean Pt foil. Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD) of CO and H/sub 2/ were used for surface characterization. Reaction kinetics for methanation were also measured at 400 torr H/sub 2/ and 100 torr CO. While no new desorption states of CO or H/sub 2/ were ever observed for any of the oxides, our results show that we can reproduce all of the unusual support effects normally observed on titania-supported Pt. We have found that a suboxide of titania can dissolve into bulk Pt at high temperatures but segregate back to the surface at room temperature. Titania tends to form a thin oxide layer which can prevent the adsorption of CO and H/sub 2/ but actually enhances methanation on Pt. X-ray photoelectron results indicate that this titania is TiO and appears to be chemically bound to Pt. Results for niobia show that it is almost identical to titania in its effect on Pt. For silica and alumina, however, much larger quantities of oxide were necessary to prevent the adsorption of CO and H/sub 2/. This indicates that these oxides form clusters or are subsurface on Pt. There is no evidence that they interact chemically with Pt. To compare the effect of supports on different metals, we investigated titania deposition on Rh. Although there are significant differences between Pt and Rh, we observed many similarities in the character of titania on these two metals, indicating that similar phenomena are responsible for support effects in both metals. 52 refs., 21 figs.
- Research Organization:
- Pennsylvania Univ., Philadelphia (USA). Dept. of Chemical Engineering
- DOE Contract Number:
- AC21-82MC19204
- OSTI ID:
- 5932188
- Report Number(s):
- DOE/MC/19204-1769; ON: DE86009187
- Country of Publication:
- United States
- Language:
- English
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