作者: Z.Q. Yu , X.M. Yang , J.H. Lunsford , M.P. Rosynek
关键词: Methane 、 Oxidative coupling of methane 、 Chemistry 、 Calcination 、 Selectivity 、 Oxygen 、 X-ray photoelectron spectroscopy 、 Heterogeneous catalysis 、 Inorganic chemistry 、 Catalysis
摘要: Na2WO4/CeO2 is an active and selective catalyst for the oxidative coupling of methane (OCM). At 780°C using a reactant feed CH4:O2:He = 4.8:1.0:5.6, C2 selectivity in excess 70% can be achieved over 9.4 mol% at CH4 conversion 22%. By contrast, exhibited by pure CeO2 under same reaction conditions, absence Na2WO4 promoter, <10%. The promoted relatively insensitive to deactivation formation surface carbonate species. A comparable effect occurs on Pr6O11 which also nonselective promoter. Characterization X-ray powder diffraction, both after calcination use OCM 780°C, confirms that remain as discrete phases, no new bulk compounds or solid solutions are formed. photoelectron spectra demonstrate all oxygen exists lattice O2− calcined catalysts reveal evidence additional species, such O2−2 O−, might serve sites activation. Pulse experiments show species do not participate directly reaction, involved activation exist only presence gas phase oxygen. Ion scattering spectroscopy situ Raman indicate initial completely covered one more layers Na2WO4, molten state conditions.