Synergistic effects in the oxidation of methane on strontium and lead hydroxyapatites

The oxidation of methane has been investigated on lead hydroxyapatite (PbHA p), strontium hydroxyapatite (SrHAp) and their binary mixtures at 873 K. Pb HAp showed no activity for the oxidation of methane, while SrHAp produced c arbon monoxide selectively at 2-4% conversion. On binary mixtures of the hy droxyapatites the conversion of methane and the selectivity to C-2 compound s reached values higher than those of the separate constituents of the mixt ure. With tetrachloromethane in the feed stream a similar synergistic effec t was observed with conversions of methane and selectivities to CH3Cl highe r on the binary mixtures than those on either SrHAp or PbHAp. The strontium -containing hydroxyapatite appears to play a crucial role in the activation of methane, while the presence of the lead-containing analogue is apparent ly required for the minimization of undesirable processes involving methyl radicals.