The catalytic properties for the oxidative coupling of methane (OCM) of La0.8Sr0.2CoO3 (LSC) and SrCo0.8Fe0.2O3 (SCF) in solid solution were studied and compared with those of 5 wt% Li/MgO, using a steady/unsteady state packed-bed reactor and a transient microbalance. The results of the steady-state cofeed experiments show that LSC possesses OCM catalytic properties similar to those of Li/MgO in terms of C2 yield and selectivity at temperatures of around 800°C. The former gives a larger C2 space time yield than the latter. SCF exhibits poor OCM catalytic properties at 700-850°C. To further examine the suitability of LSC as a membrane material for use in a dense membrane reactor for OCM, the instant OCM selectivity and activity and oxygen consumption rate for LSC and 5% Li/MgO on exposure to pure methane in cyclic feed mode were measured respectively at 850°C and 800°C. For both materials, the unsteady-state cyclic feed operation gives smaller initial OCM activity and larger initial C2 selectivity than the cofeed steady state operation. Li/MgO quickly loses its OCM activity and selectivity in the unsteady state operation due to rapid consumption of the active sites. Up to 5 min of methane run time, LSC maintains appreciable OCM activity with poorer C2 selectivity as compared to the steady state cofeed operation. The surface of LSC membrane allow oxygen partial pressure may become nonselective for OCM in membrane reactor applications.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry