Partial oxidation of methane to synthesis gas over MgO- and SiO{sub 2}-supported rhodium catalysts
- State Univ. of New York, Amherst, NY (United States). Dept. of Chemical Engineering
The partial oxidation of methane over MgO- and SiO{sub 2}-supported rhodium catalysts was investigated, using a CH{sub 4}/O{sub 2} mixture with a molar ratio of 2.1/1 as feed gas. At 750 C and atmospheric pressure, the 1% Rh/MgO catalyst exhibited a very high stability at the high gas hourly space velocity of 720,000 ml/g h, its catalytic activity and selectivity remaining constant and high after an induction time up to 100 h of reaction. In contrast, the 1% Rh/SiO{sub 2} catalyst deactivated rapidly. To explain the above results, the reaction behaviors of CH{sub 4} and CH{sub 4}/O{sub 2} (2/1) over the oxidized catalysts 1% Rh(O)/MgO and 1% Rh(O)/SiO{sub 2} were studied in a pulse microreactor. No carbon deposition occurred during the reaction of CH{sub 4} with the MgO-supported rhodium catalyst, even after the catalyst was almost completely reduced. In contrast, a notable amount of surface carbon was generated during the reaction of CH{sub 4} with the SiO{sub 2}-supported rhodium catalyst, even after the catalyst was almost completely reduced. In contrast, a notable amount of surface carbon was generated during the reaction of CH{sub 4} with the SiO-supported rhodium catalyst. During the reaction of CH{sub 4}/O{sub 2} (2/1) over the oxidized catalysts, the rhodium oxide supported on SiO{sub 2} was easily reduced by CH{sub 4}, while the reduction of rhodium oxide supported on MgO occurred with some difficulty. This implies much stronger interactions between rhodium oxide and MgO than between the former and SiO{sub 2}. Temperature-programmed reduction experiments also revealed much stronger interactions between rhodium and magnesium oxide and that two kinds of rhodium compounds were present in the oxidized MgO-supported rhodium catalyst. X-ray powder diffraction enabled the authors to identify Rh{sub 2}O{sub 3} and MgRh{sub 2}O{sub 4} in precalcined 10% Rh(O)/SiO{sub 2} and 10% Rh(O)/MgO, respectively. It is suggested that the strong interactions between rhodium and magnesium oxide (especially the formation of MgRh{sub 2}O{sub 4}) are responsible for the high stability of the MgO-supported rhodium catalysts.
- OSTI ID:
- 687734
- Journal Information:
- Journal of Catalysis, Vol. 186, Issue 1; Other Information: PBD: 15 Aug 1999
- Country of Publication:
- United States
- Language:
- English
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