OXYGEN-TRANSPORT BY OXYGEN POTENTIAL GRADIENT IN DENSE CERAMIC OXIDE MEMBRANES

Numerous studies have been conducted in recent years on the partial ox idation of methane to synthesis gas (syngas: CO + H-2) with air as the oxidant. In partial oxidation, a mixed-oxide ceramic membrane selecti vely transports oxygen from the air; this transport is driven by the o xygen potential gradient, Of the several ceramic materials we have tes ted, a mixed oxide based on the Sr-Fe-Co-O system has been found to be very attractive. Extensive oxygen permeability data have been obtaine d for this material in methane conversion experiments carried out in a reactor, The data have been analyzed by a transport equation based on the phenomenological theory of diffusion under oxygen potential gradi ents. Thermodynamic calculations were used to estimate the driving for ce for the transport of oxygen ions, The results show that the transpo rt equation deduced from the literature describes the permeability dat a reasonably well and can be used to determine the effective or ambipo lar diffusion coefficients and the associated activation energy of oxy gen ions in the ceramic membrane material.