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以二氧化硅担载铁氧化物（１ｗｔ％ Ｆｅ／ＳｉＯ２）为探针，结合ＸＲＤ、ＸＡＮＥＳ以及ＥＸＡＦＳ分析结果首次从表面配位几何的观点讨论了钠助剂对Ｆｅ／ＳｉＯ２催化剂结构及其甲烷氧化偶联反应性能所产生的影响。ＸＲＤ分析表明，Ｆｅ／ＳｉＯ２经８００℃焙烧后仍保持无定形特征，添加钠助剂并经８００℃焙烧后，Ｎ２Ｆｅ／ＳｉＯ２已转化为α－方石英结构。Ｆｅ／ＳｉＯ２的ＥＸＡＦＳ拟合结果显示，铁中心被５个近邻氧环绕，平均Ｆｅ－Ｏ键长为０．１９４ｎｍ。与Ｆｅ／ＳｉＯ２相比，Ｎａ－Ｆｅ／ＳｉＯ２的径向结构函数谱中最强峰的相对强度提高了１／４，表明形成了一个更加密集的Ｆｅ－Ｏ壳层。拟合结果表明围绕中心铁原子０．１８９ｎｍ处平均有４．１个氧近邻。Ｆｅ－Ｋ边ＸＡＮＥＳ谱表明钠的参与使催化剂的活性组分由配位不饱和的八面体位逐渐向四配位四面体位迁移。甲烷氧化偶联反应结果显示，添加钠助剂后甲烷转化率有所下降，但是Ｃ２烃的选择性提高了近４２个百分点，ＣＯｘ的选择性则明显下降。说明钠的引入使催化剂的表面结构发生变化，所形成的多数四面体／少数八面体混合结构有效地抑制了甲烷的深度氧化，乙烯乙烷的选择性明显提高。
The effects of sodium promoters on the structure of Fe / SiO2 catalyst and its methane were discussed for the first time from the viewpoint of surface coordination geometry with the XRD, XANES and EXAFS results using silica supported iron oxide (1wt% Fe / SiO2) as probe. Oxidative coupling reaction of the impact. The results of XRD showed that amorphous Fe / SiO2 remained amorphous after calcined at 800 ℃. After addition of sodium promoter and calcination at 800 ℃, N2Fe / SiO2 was transformed into α-cristobalite. The EXAFS fitting results of Fe / SiO2 show that the iron center is surrounded by 5 nearby oxygen and the average Fe-O bond length is 0.194 nm. Compared with Fe / SiO2, the relative intensity of the strongest peak in the radial structure function spectrum of Na-Fe / SiO2 is increased by 1/4, indicating that a more dense Fe-O shell is formed. The fitting results show that there are an average of 4.1 oxygen neighbors around 0.189 nm of the central iron atom. The XANES spectra on the Fe-K side show that the participation of sodium causes the active component of the catalyst to migrate gradually from the coordinately unsaturated octahedral sites to the tetradentate tetrahedral sites. Methane oxidative coupling reaction results showed that methane conversion rate decreased with the addition of sodium promoter, but the selectivity of C2 hydrocarbons increased by nearly 42%, while the COx selectivity decreased significantly. It shows that the introduction of sodium changes the surface structure of the catalyst. The majority of tetrahedron / minority octahedron mixed structure effectively inhibits the deep oxidation of methane and the selectivity of ethylene ethane is obviously increased.