Strong-metal-promoter oxide interactions induced by calcination in V, Nb, and Ta oxide promoted Rh/SiO{sub 2} catalysts
- Institut fuer Physikalische Chemie, Muenchen (Germany)
- Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); and others
The influence of the calcination temperature on the structure of Rh/SiO{sub 2} catalysts promoted by Vb transition metal oxides has been studied. Calcination at T > 973 K leads to the formation of crystalline RhXO{sub 4} mixed oxides with increasing abundance in the order RhTaO{sub 4} < RhNbO{sub 4} < RhVO{sub 4}. Their reduction at T = 773 K yields highly dispersed Rh{degrees} metal particles which seem to be embedded in a matrix of partially reduced promoter oxide. The presence of Vb metal oxides enhances the noble metal dispersion as compared to unpromoted Rh/SiO{sub 2} catalysts. Calcination at T = 773 K establishes an interaction between Rh{sub 2}O{sub 3} and promoter oxide which manifests itself in a decreased CO-chemisorption capacity after low temperature reduction (LTR = 523 K). This calcination induced metal-promoter interaction decreases with increasing atomic number of the promoter element. 46 refs., 10 figs., 5 tabs.
- OSTI ID:
- 563477
- Journal Information:
- Journal of Catalysis, Vol. 167, Issue 2; Other Information: PBD: 15 Apr 1997
- Country of Publication:
- United States
- Language:
- English
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