五氧化二钒/铈改性二氧化钛催化甲醇高选择性氧化制备二甲氧基甲烷

通过溶剂热法制备Ce掺杂的TiO₂,利用等体积浸渍法制得一系列V₂O₅/Ce-TiO₂催化剂,并用于甲醇选择性氧化制二甲氧基甲烷(DMM)。 采用XRD、UV-Vis、 H₂-TPR、NH₃-TPD等技术手段对催化剂进行了表征。 结果表明,Ce掺杂改性后的TiO₂负载V₂O₅更有利于催化剂表面钒氧物种的分散,且钒氧物种主要以孤立的和聚合态的形式存在,没有形成V₂O₅晶相结构。 Ce掺杂改性后,改变了TiO₂载体与钒氧物种间的作用力,Ce掺杂量越大,钒氧物种的还原温度逐渐向高温移动,使得催化剂的氧化还原能力减弱。 Ce改性的TiO₂负载V₂O₅,Ce的改性量对催化剂的酸性质几乎没有影响,但是催化剂的酸性却随着V₂O₅负载量的增大而逐渐减弱。 当Ce和Ti的摩尔比为0.01,V₂O₅的负载量为10%所得催化剂10V/1Ce-TiO₂具有较为适宜的氧化还原性和酸性,在反应温度160 ℃时,甲醇的转化率为39.6%,DMM的选择性高达99.9%。

Oxidation of Methanol to Dimethoxymethane over Vanadium Pentoxide/Cerium-Titanium Dioxide with High Selectivity

The composite Ce-TiO₂ support was prepared through solvothermal treament of Ce(NO₃)₃ and butyl titanate. A series of V₂O₅/Ce-TiO₂ catalysts with different vanadium loadings were obtained by incipient impregnation with ammonium metavanadate solution. The catalytic properties of V₂O₅/Ce-TiO₂ for selective oxidation of methanol to dimethoxymethane(DMM) were investigated. The V₂O₅/Ce-TiO₂ catalysts were characterized by XRD, UV-Vis, H₂-TPR, and NH₃-TPD. The results show that the dispersion of vanadium species is improved on the surface of Ce modified TiO₂. The interaction between vanadium species and supports is changed. The reduction temperature increases with the increasing Ce content. The Ce content in modified TiO₂ does not affect the acidity of the V₂O₅ supported catalysts, but the acidity of the catalysts decreases with the increasing of V₂O₅ content. For the catalyst of 10V/1Ce-TiO₂(The numbers 10 and 1 represent the mass percentage of V₂O₅ in the catalyst and molar ratio of Ce and TiO₂, respectively), the methanol conversion and DMM selectivity reach 39.6% and 99.9%, respectively, at 160 ℃.