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

摘要

The composite Ce-TiO2 support was prepared through solvothermal treament of Ce( NO3 ) 3 and butyl titanate .A series of V2 O5/Ce-TiO2 catalysts with different vanadium loadings were obtained by incipient impregnation with ammonium metavanadate solution .The catalytic properties of V2 O5/Ce-TiO2 for selective oxidation of methanol to dimethoxymethane ( DMM ) were investigated .The V2 O5/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 TiO 2 .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 V2 O5 supported catalysts , but the acidity of the catalysts decreases with the increasing of V2 O5 content.For the catalyst of 10V/1Ce-TiO2 ( The numbers 10 and 1 represent the mass percentage of V2 O5 in the catalyst and molar ratio of Ce and TiO 2 , respectively ) , the methanol conversion and DMM selectivity reach 39.6% and 99.9%, respectively , at 160 ℃.%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V2 O5／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V2 O5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V2 O5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V2 O5，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V2 O5负载量的增大而逐渐减弱。当Ce和Ti的摩尔比为0.01，V2 O5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％。