Oxygen permeation and oxidative coupling of methane in yttria doped bismuth oxide membrane reactor

The performance of the oxidative coupling of methane (OCM) in the membrane reactor made of BY25 was studied. Oxygen permeation flux through BY25 membrane was ~ 1 x 10^-8 mol/sq cm/sec at 850°C with an activation energy of ~ 70 kJ/mol.The oxygen pressure dependency of permeation flux was consistent with the power law with the exponent of 0.25 on oxygen partial pressure. The rate-limiting step for oxygen permeation was the bulk diffusion of the electron-holes. Considerably higher C₂ selectivity (~ 80%) was attained for OCM in the BY25 membrane reactor than in the cofeed reactor packed with the pellets of the same BY25 (~50%) at the same C₂ yield (~ 5%). The membrane reactor proved to be effective in improving C₂ selectivity. After OCM, the BY25 membrane remained in good integrity although the reaction formed some impurity phases on the membrane surface exposed to the methane stream.