Perovskite hollow fibre membranes in the partial oxidation of methane to synthesis gas in a membrane reactor

A membrane reactor with perovskite hollow fibres in combination with a commercial steam reforming catalyst is used to produce in a long term scale synthesis gas with a methane conversion of about 96%, a CO selectivity of 95% and at a H2/CO ratio of 2. By having the whole perovskite hollow fibre at 875°C and adding steam, Ba carbonate and coke formations, respectively, could be avoided.

Fig. 3. Selectivities for CO and CO2 in a packed bed reactor with the Ni steam reforming catalyst used in the membrane reactor at low CH4 conversions at 820°C. However, two problems had to be solved: (1) Coke deposition occurs during the POM and results in a mechanical blocking of the reactor after ca. 50 h time on stream. By using methane/ steam mixtures as feed, coke deposition could be avoided completely. (2) The BaCoxFeyZrzO3-d hollow fibre was destructed by Ba carbonate formation in the cold region (about 600°C) of the reactor. Carbonate formation could be stopped for thermodynamic reasons by having the whole perovskite fibre in the hot zone of the oven at 875°C which requires a novel hot In perovskite membrane reactors the methane is not really partially oxidized but gaseous oxygen is released from the perovskite surface and oxidizes the methane. This oxidation is accelerated by a Ni-based steam reforming catalyst. CO is the primary product which is immediately oxidized to CO2. The total oxidation products H2O and CO2 become catalytically reduced by non-reacted CH4 by steam and dry reforming using the same Ni-based steam reforming catalyst.