Partial oxidation of methane to synthesis gas over rhodium catalysts

• Published in: Catalysis today 1998-04, Vol.40 (2), p.157-170
• Main Authors: Heitnes Hofstad, K, Hoebink, J.H.B.J, Holmen, A, Marin, G.B
• Format: Article
• Language: English
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/S0920-5861(98)00004-2

The partial oxidation of methane to synthesis gas has been studied using the temporal-analysis-of-product (TAP) set-up on different Rh catalysts. Rh sponge diluted with either SiC or α-Al 2O 3, and 0.3 wt% Rh/α-Al 2O 3 were investigated using pulses and continuous flow of methane and oxygen. The effect of introducing a support in the catalyst system was given special concern. Blank experiments on the α-Al 2O 3 support showed no activity for the partial oxidation of methane in the 673–1123 K range. Oxygen multipulse experiments on the 0.3 wt% Rh/α-Al 2O 3 and on the pure support showed that α-Al 2O 3 is not inert concerning adsorption, desorption and storage of oxygen. Totally oxidized catalysts show low activity because of few sites for methane dissociation. Mainly, total oxidation products CO 2 and H 2O are formed. The formation of these products partially reduces the catalyst whereupon with time-on-stream a steep discontinuity is observed in the methane and oxygen conversion as reduced metal sites largely increase the rate of methane dissociation. The discontinuity is followed by a continuous change in the product distribution from CO 2 and H 2O towards CO and H 2. The time-on-stream, before an active catalyst was obtained, increased with increasing amount of oxygen in the feed. The time before obtaining an active catalyst also depended on the catalyst system and changed in the following way: Rh sponge mixed with SiC