A Study on the Structure and Catalytic Ativity of CaO -La₂O₃ Catalysts

The C₂ selectivity of catalyst La₂O₃ in oxidative coupling of methane （OCM） may be enhanced by doping a small amout of CaO. Studies by various experimental techniques, such as determination of lattice parameters, Raman spectroscopy and measurement of fluorescence emission of Eu³⁺ indicated that part of La³⁺ ions was substituted by Ca²⁺ ion in La₂O₃ lattice and coordination symmetry of La³⁺ was increased, as a result, a P-type semiconductor was formed. Based on the determination of ionic conductivity and XPS, an evidence was gained that the entrance of Ca2-ion into La₂O₃ lattice causes the formation of adsorbed oxygen species （i. e. O^-） which is benefit to the enhancement of C₂ selectivity in OCM reaction.