Oxidative coupling of methane in Ba0.5Sr0.5Co0.8Fe0.2O3−δ tubular membrane reactors

A dense membrane tube made of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) was prepared by plastic extrusion from BSCF oxide synthesized by the complexing EDTA-citrate method. The membrane tube was used in a catalytic membrane reactor for oxidative coupling of methane (OCM) to C2 without an additional catalyst. At high methane concentration (93%), about 62% C2 selectivity was obtained, which is higher than that achieved in a conventional reactor using the BSCF as a catalyst. The dependence of the OCM reaction on temperature and methane concentration indicates that the C2 selectivity in the BSCF membrane reactor is limited by high ion recombination rates. If an active OCM catalyst (La-Sr/CaO) was packed in the membrane tube, C2 selectivity and CH4 conversion increased compared to the blank run. The highest C2 yield in the BSCF membrane reactor in presence of the La-Sr/CaO catalyst was about 15%, similar to that in a packed-bed reactor with the same catalyst under the same conditions. However, the ratio of C2H4/C2H6 in the membrane reactor was much higher than that in the packed-bed reactor, which is an advantage of the membrane reactor.