Oxidative coupling of methane over the oxides of Group IIIA, IVA, and VA metals

Abstract

The conversion of methane to C/sub 2/ hydrocarbons by oxidative coupling was studied on the oxides of group IIIA (3), IVA (4), and VA (5) metals over a temperature range of 550-700/sup 0/C. The effect of the preparative method of the catalyst, of alkali promoters, and of supports was investigated in more detail with bismuth oxide. The addition of alkali, up to a concentration of 8 x 10/sup 20/ ions/g, promoted alumina-supported Bi/sub 2/O/sub 3/ catalysts, and a maximum was observed for the total carbon conversion and the C/sub 2/ selectivity at Bi/sub 2/O/sub 3/ concentrations of 3-10 wt % in the Bi/sub 2/O/sub 3/-K/sub 2/CO/sub 3/-Al/sub 2/O/sub 3/ catalysts. It was also found that the yield of C/sub 2/ hydrocarbons on the Bi/sub 2/O/sub 3/ catalysts strongly depended on the support: alumina was most efficient, followed by magnesia, while Bi/sub 2/O/sub 3/ supported on silica and titanium oxide was inactive under the present conditions. When supported on alumina and promoted by potassium, Bi/sub 2/O/sub 3/ was most active and selective followed by SnO/sub 2/ and PbO in that order but Ga/sub 2/O/sub 3/, In/sub 2/O/sub 3/, Tl/sub 2/O/sub 3/, GeO/sub 2/, and Sb/sub 2/O/sub 4/ gave practically no C/submore » 2/ hydrocarbons at 640/sup 0/C. The results of the present study and of the hydrogen-exchange reaction between CH/sub 4/ and CD/sub 4/ suggest that the Bi/sub 2/O/sub 3/-K/sub 2/CO/sub 3/-Al/sub 2/O/sub 3/ catalysts catalyze the oxidative coupling reaction as bifunctional catalysts.« less