Frontiers in Materials (Aug 2018)
Catalyst Screening for Oxidative Coupling of Methane Integrated in Membrane Reactors
Abstract
Increased availability of methane from shale gas and stranded gas deposits in the recent years may facilitate the production of ethylene by means of potentially more competitive routes than the state-of-the-art steam cracking processes. One appealing route is the oxidative coupling of methane (OCM), which is considered in this work for the production of ethylene by means of the use of catalytic membrane reactors (CMR) based on Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) ceramic material. In a first approach, a screening of 15 formulations as catalysts for the ethylene-ethane production was conducted on CMR consisting of disk-shaped planar BSCF membranes. At 900°C, the maximum C2 selectivity was 70%, reached with Ba0.5Sr0.5FeO3−δ and La0.5Ce0.1Sr0.4Co0.8Fe0.2O3−δ catalysts. On the other hand, low CH4 conversions (XCH4) resulted in C2 yields below 3%. Operation at 1,000°C significantly shifted XCH4 for all the activated membranes due to the decrease in CH4/O2 ratios, thus obtaining C2 yields close to 9% and productivities of ca. 1.2 ml·min−1·cm−2 with Ce0.9Gd0.1O2−δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ impregnated with Mn-Na2WO4 catalysts. The performance of OCM reaction was also studied in a tubular catalytic membrane reactor. Tubular configuration improved C2 yield by minimizing CH4/O2 ratios up to 1.7, obtaining a maximum of 15.6% at 900°C with a BSCF capillary membrane activated with a packed bed of 2 wt% Mn/5 wt% Na2WO4 on SiO2 catalyst.
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