Comparative study on oxygen permeation and oxidative coupling of methane on disk-shaped and tubular dense ceramic membrane reactors

Oxygen permeation and oxidative coupling of methane (OCM) on fluorite-structured Bi_1.5Y_0.3Sm_0.2O_3-δ (BYS) membrane reactors of disk-shaped and tubular geometries were studied at high temperatures (800-900 °C). Their oxygen fluxes under an oxygen partial pressure gradient of air/helium are similar and in the range of (1-3) × 10^-8 mol/cm²·s at 900 °C. The highest C₂ yields obtained in the tubular and disk-shaped BYS membranes are 22% and 10.4%, respectively. The oxygen permeation fluxes through both the disk-shaped and tubular BYS membrane reactors under OCM reaction conditions are 1-2 orders of magnitude higher than those under oxygen permeation conditions with He as the purge. Oxygen permeation flux through the tubular BYS membrane is an order of magnitude smaller than that through the disk-shaped membrane under the OCM reaction conditions. The results show that the membrane geometry and downstream flow conditions have a significant effect on the reaction results. The tubular geometry gives more favorable results in terms of C₂ yield and selectivity.