Na-W-Mn/SiO_2催化剂活化甲烷的研究 Ⅰ.活性中心的结构

Study on Methane Activation over Na W Mn/SiO_2 Catalysts I. Structure of the Active Center

制备了不同 Na、W、Mn组分的 Na- W- Mn/ Si O2 催化剂 ,并进行了甲烷氧化偶联反应催化性能的评价和XPS、XRD、L RS表征 .研究结果表明 ,Na不但有强的表面富集能力 ,而且可以使 Mn向表面发生迁移 .首次发现 Na2 W2 O7也是活化甲烷的活性相 .活化甲烷的活性中心是 Na- O- Mn和 Na- O- W结构单元 ,且 Na- O-Mn主要存在于催化剂的表面 ,Na- O-

Na W Mn/SiO 2 catalysts containing different amounts of sodium, tungsten and manganese were prepared and their catalytic performance for oxidative coupling of methane (OCM) have been evaluated. Structural properties of the catalysts were characterized using XPS, XRD and LRS. The experimental results indicate that sodium component is not only enriched on the catalyst surface, and it promotes the migration of manganese to the catalyst surface. The Na 2W 2O 7 crystal line phase, which is found the first time in these catalysts, is an active phase for methane activation. Both Na-O-Mn and Na-O-W are the active centers of the catalysts for methane activation. Na-O-Mn exists on the catalyst surface, and Na- O-W exists deep underneath the catalyst surface.