| Popis: |
A series of NaCl/B2O3/Fe2O3 catalysts having a B/Fe atomic ratio from 0 to 0.3 and 0.25 of Na/Fe atomic ratio were prepared for the oxidative coupling of methane (OCM). It was noted that NaCl and B2O3 show a synergetic effect: NaCl/Fe2O3 produces mainly CO2, but B2O3/Fe2O3 and B2O3/NaCl have poor activity. NaCl/B2O3/Fe2O3 catalyst has however high activity and selectivity. When the addition of B2O3 approaches 15 (at)%, the C-2 yield and selectivity reach their maxima, 17% and 75% respectively. The C2H4/C-2 ratio is as high as 76%. XRD, XPS, H-2-TPR, O-2-TPD and In - situ Mossbauer were employed to investigate the properties of the catalysts. Results show there is a synergetic effect between NaCl and B2O3 and FeOx surface. B2O3 modifies the redox ability of Fe2O3. The NaCl modified B2O3/FeOx has high reduction and lattice oxygen evaporation rates at 750 degrees C. The high activity and selectivity of the NaCl/B2O3/FeOx catalyst are closely related with this synergetic effect. |
