OXIDATIVE COUPLING OF METHANE OVER VARIOUS METAL-OXIDES SUPPORTED ON STRONTIUM CARBONATE CATALYSTS

The oxidative coupling of methane was studied over unsupported SrCO3 and 20 kinds of (10 mole%) metal oxides (Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Pb, La, Y, Zr, V, Cr, Mo, Fe, Co, Ni, and Ag) supported on SrCO3. The prepared catalysts were composed of microparticles of diameters ranging from 0.3 to 100 μm, and were considered to be covered by the oxides added. In general, the oxygen and methane conversions at 1023 or 1073 K increased with an increase of the surface area of the doped catalysts. C2 selectivity at 1023 K decreased with an increase of methane conversion on the surface area, except for Fe-, Co-, Ni-, Cr-, and Ag-doped catalysts, which produced quite low C2 selectivity. These results suggest that the catalytic activity or selectivity of catalysts other than Fe, Co, Ni, Cr, and Ag do not differ remarkably from each other at high temperatures (1023 and 1073 K), although there is a trend that Li, Cs, and La oxides are more active and K, Cs, and Y oxides are more selective. Doped oxides were not very effective on SrCO3 but were quite effective on MgO, which can incorporate added cations in the lattice. These results suggest that there is very little interaction between the additives and SrCO3. The XRD study also disclosed that the SrCO3 crystal was not affected by the doping. © 1991.