Oxidative Coupling of Methane on Calcium-Lead and Barium-Lead Hydroxyapatites

Abstract

Oxidative coupling of methane to ethylene and ethane has been investigated on binary hydroxyapatite catalysts; calcium-lead hydroxyapatite (CaHAp-PbHAp) and barium-lead hydroxyapatite (BaHAp-PbHAp) at 973 K. Although BaHAp, CaHAp and PbHAp were inactive for the oxidative coupling of methane, those binary hydroxyapatites afforded C2 compounds rather selectively. During the oxidation on CaHAp-PbHAp catalysts, those catalysts were mainly converted to Ca5 .5Pb4.5(PO4)6(OH)2 to afford great activities while an unfavorable conversion of CaHAp to Ca3(PO4)2, which was inactive for the oxidation of alkanes, was rather suppressed. In contrast, BaHAp in the BaHAp-PbHAp catalysts was extensively converted to inactive Ba3(PO4)2, resulted in the complete deactivation on BaHAp-PbHAp, particularly on PbHAp-rich catalysts.