Temperature-programmed reduction and XRD studies of the interactions in supported rhodium catalysts and their effect on partial oxidation of methane to synthesis gas
In the present paper, comprehensive temperature-programmed reduction and X-ray diffraction studies were conducted, with particular emphasis on the effect of calcination temperature on the interactions between rhodium oxide and support. The formation of a compound between rhodium and support oxide is strongly dependent on the nature of the support and the calcination temperature. No such compounds were formed over {gamma}-Al{sub 2}O{sub 3} and SiO{sub 2} supported Rh catalysts even after a calcination at a temperature as high as 950 C. However, LaRhO{sub 3}, MgRh{sub 2}O{sub 4}, YRhO{sub 3}, and RhTaO{sub 4} could be formed over La{sub 2}O{sub 3}, MgO, Y{sub 2}O{sub 3}, and Ta{sub 2}O{sub 5} supported catalysts after their calcination at suitable temperatures. The ease of formation of these compounds decreased in the sequence MgO > La{sub 2}O{sub 3} {much{underscore}gt} Y{sub 2}O{sub 3} {ge} Ta{sub 2}O{sub 5}. The lower reducibilities of these compounds compared to that of Rh{sub 2}O{sub 3} brought evidence of increased Rh-O bond strength. In other words, the formation of these compounds after calcination is an indication of strong interactions between rhodium and support. At a reaction temperature of 750 C, La{sub 2}O{sub 3} and MgO provided stable catalytic activities and selectivities during 100 h of reaction, whereas deactivation was observed over the Y{sub 2}O{sub 3} and Ta{sub 2}O{sub 5} supported catalysts. However, because compounds between the latter two supports and Rh{sub 2}O{sub 3} could be formed at higher temperatures, reactions at higher temperatures have also been carried out. It was found that the stability of the 1 wt% Rh/Ta{sub 2}O{sub 5} could be notably improved at a reaction temperature of 900 C, and that the stability of the 1 wt% Th/Y{sub 2}O{sub 3} could be improved at a reaction temperature of 850 C.
- Research Organization:
- State Univ. of New York at Buffalo, Amherst, NY (US)
- OSTI ID:
- 20017452
- Journal Information:
- Journal of Catalysis, Vol. 190, Issue 1; Other Information: PBD: 15 Feb 2000; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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