Oxidative Coupling of Methane over Various Barium Salts Mixed with CaO: The Relation with Their Surface Basicities

Article abstract of DOI:10.1246/bcsj.65.2251

Oxidative coupling of methane to ethane and ethylene was carried out over barium salts mixed with CaO catalysts prepared by a wet-mixing method.The mixing effect of the barium salts on the C2 yield at 800 deg C was remarkable in the following order: BaBr2>BaCl2>>BaI2, Ba(OH)2, BaF2>BaC2O4, Ba(NO3)2>BaCO3, BaSO4>Ba3(PO4)2(>CaO).The high C2 yield of the BaCl2/CaO catalysts was kept relatively long, and was nearly constant (19-20percent) over a range of 5 to 30 molpercent BaCl2.Measurements of the temperature-programmed desorption of the used barium salt/CaO catalysts showed that a catalyst with the high C2 selectivity and high C2 yield tended to have large CO2 desorption peaks at higher temperatures; they were also well-dispersed with barium ions.In the case of BaCl2/CaO catalysts (2.5-40 molpercent BaCl2), a large desorption peak of CO2 was observed at around 730 deg C, that was associated with their high C2 yields.The role of basic sites resulting from the desorption of CO2 is discussed.