Promotion by strontium fluoride of neodymium oxide catalysis of the oxidative coupling of methane

Abstract

Catalytic performance measurements showed that CH₄ conversion and C₂ selectivity were higher over SrF₂/Nd₂O₃ catalyst than over pure Nd₂O₃ for the oxidative coupling of methane (OCM). XRD indicated that there was some exchange of F⁻ and O²⁻, leading to the formation of tetragonal and rhombohedral NdOF phases during the catalyst preparation. After a certain amount of SrF₂ was added to Nd₂O₃, the increase in surface basicity and conductivity, as well as the role of F⁻ on the dispersion of surface active sites, would be favourable to a decrease in the secondary deep oxidation of methyl radicals and C₂ hydrocarbons, giving improved C₂ selectivity. Since there is a certain correlation between methane conversion and C₂ selectivity for an oxygen-limited OCM reaction, methane conversion is also expected to increase with the increase in C₂ selectivity.