Methane to syngas conversion: Part I. Equilibrium conditions and stability requirements of membrane materials

Thermodynamic data have been used to predict the dependence of methane conversion on temperature and oxygen partial pressure in mixed conducting membrane reactors, and the corresponding fractions of water vapor, H2, CO and CO2. The relations between methane conversion, gas composition and oxygen partial pressure were also used to formulate the oxygen balance in mixed conducting membrane reactors, with tubular reactor and continuous stirred tank reactor (CSTR) configurations. A single dimensionless parameter accounts for the combined effects of geometric parameters of the membrane reactor, the permeability of the membrane material, and flow rate at the entry of the reactor. Selected examples were calculated to illustrate the effects of steam to methane and inert to methane ratios in the gas entering the reactor. The values of oxygen partial pressure required to attain the highest yield of CO and H2 were also used to estimate the stability requirements to be met by mixed conducting membrane materials. Suitable membrane designs might be needed to bridge the difference between the conditions inside the reactors and the stability limits of known mixed conductors.