Secondary Reactions of Methyl Radicals with Lanthanide Oxides: Their Role in the Selective Oxidation of Methane

Article abstract of DOI:10.1021/j100345a012

Reactions between methyl radicals and certain members of the lanthanide oxide series have been studied by using a matrix isolation electron spin resonance technique.Methyl radicals react extensively with the lanthanide-metal oxides CeO2, Pr6O11, and Tb4O7, all of which have multiple cationic oxidation states.By contrast, the oxides La2O3, Nd2O3, Sm2O3, Eu2O3, and Yb2O3 react with CH3^. radicals to only a small extent.Consistent with this observation, the former group of oxides is ineffective in the generation of CH3^. radicals which emanate into the gas phase.The reaction of CeO2 with CH3^. radicals is strongly inhibited by the addition of Na2CO3, and consequently radical production is enhanced.This effect is manifested in the catalytic properties of CeO2, which is a complete oxidation catalyst in its pure form but becomes a good catalyst for the oxidative coupling of methane following the addition of Na2CO3.