Thirty-five doped and undoped rare earth oxide catalysts were synthesized and tested under identical conditions for the oxidative coupling of methane. While La₂O₃ was found to be the most active, La₂O₃ doped with Sr was found to be the most selective. High resolution low energy ion scattering (HR-LEIS) showed that doping with Sr above 2 mole % led to migration of Sr to the surface of the catalyst producing surface (Sr/La) ratios of 2.7 – 4.4 from bulk (Sr/La) ratios of 0.053 and 0.13, respectively. Operando Raman analysis run under OCM conditions identified La₂O₃ and SrCO₃ as the predominant lanthanum and strontium phases during reaction. A bilayer structure comprising a thermally stable Sr-doped La₂O₃ base covered with a mostly amorphous Sr phase containing SrCO₃, SrO and SrO₂ was proposed. Selectivity to C₂+ for this structure increased with surface Sr content; and SrO₂ is believed to be responsible for this effect.

合成了35种掺杂和未掺杂的稀土氧化物催化剂，并在相同条件下对甲烷的氧化偶联进行了测试。虽然发现La ₂ O ₃活性最高，但发现掺杂Sr的La ₂ O ₃最具选择性。高分辨率低能离子散射（HR-LEIS）表明，当Sr的掺杂量大于2摩尔％时，Sr迁移至催化剂表面的生成量（Sr / La）从体积比（Sr / La）为2.7 – 4.4。比分别为0.053和0.13。在OCM条件下进行的Operando拉曼分析确定了La ₂ O ₃和SrCO ₃作为反应过程中主要的镧和锶相。提出了一种双层结构，该双层结构包括热稳定的掺杂有Sr的La ₂ O ₃基层，该基层覆盖有大部分为非晶态的Sr相，其中含有SrCO ₃，SrO和SrO ₂。该结构对C ₂ +的选择性随表面Sr含量的增加而增加。SrO ₂被认为是造成这种效应的原因。