In situ confocal microprobe Raman spectroscopic studies on defective La-based complex oxides
- 化学化工－已发表论文 
The adsorption of O-2 over defective La2O3-based OCM catalysts with anionic vacancies, and the reaction of surface oxygen species with CH4 were studied by means of in situ confocal microprobe Raman spectra. The partially reduced oxygen species O-2(-), O-2(2-), O-2(delta-)(0<delta<1) and even the lattice oxygen ion O2- can be detected on the surface of O-2-pretreated La2O3-based catalysts. At lower temperatures (< 573 K) it is peroxide species O-2(2-) or O- that is more essential for the coupling of methane, while at higher temperatures the superoxide O-2(-) and lattice oxygen species O2- are rather important. It is easier for fluoride-containing La2O3-based catalysts to induce the oxygen species with fewer negative charges and the basicity of the catalyst surface is weakened, so that the C-2 selectivity for OCM reaction is improved.