NaCl和B_2O_3在修饰FeO_x催化剂中的协同作用

Synergetic Effect between NaCl and B_2O_3 in Modified FeO_x Catalysts

应用连续催化反应，XPS，XRD，H2－TPR,O2－TPD和In－situMossbauer谱等方法表征了一系列组成不同的NaCl／B2O3／Fe2O3催化剂．结果表明NaCl与B2O3在修饰FeOx催化剂上存在明显的协同作用，B2O3调变了FeOx的还原能力，NaCl修饰了B2O3／FeOx使之具有很高的还原速度与晶格氧气化速度．催化剂的催化性能同这种协同作用密切相关．

A series of NaCl/B2O3/Fe2O3 catalysts having a B/Fe atondc ratio from 0 to 0.3 and 0.25 of Na/Fe atomic ratio were prepared for the oaldative 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 C2 yield and selectivity reach their maxima, 17% and 75% respectively. The C2H4/C2 ratio is as high as 76%. XRD, XPS, H2-TPR, O2-TPD and In - situ Mossbauer were employed to investigate the properties of the catalysts. Results show there is a syn ergetic effect between NaCl and B2O3 on FeOx surface. B2O3 modifies the redox ability of Fe2O3. The NaCl modified B2O3/FeOx has high reduction and lattice oxygen evaporation rates at 750℃. The high activity and selectivity of the NaCl/B2O3/FeOx catalyst are closely related with this synergetic effect.