OXIDATIVE COUPLING OF METHANE OVER AMORPHOUS LNALO3 CATALYSTS (LN = RARE-EARTH-METAL)

The oxidative coupling of methane was studied over a series of amorphous LnA1O3 catalysts (Ln = rare earth metal). The specific rate of C2 hydrocarbon formation decreased with increasing atomic number of the lanthanide, except those containing the lanthanide ions of higher fourth ionization potentials. This suggests that the basicity of the lanthanide, or the tendency to lose anions, is closely related to the formation of the active sites. Temperature-programmed desorption studies on a series of the catalysts indicated that oxygen molecules were desorbed from the catalyst during heating to reaction temperature, and that two kinds of oxygen adsorption sites were characteristic of active amorphous catalysts. The results suggest that these sites are responsible for the coupling reaction. © by R. Oldenbourg Verlag