钨对VO_x/TiO_2催化燃烧氯苯的作用

Effect of W addition on VO_x/TiO_2 catalyst for catalytic combustion of chlorobenzene

采用等体积浸渍法(VOx和WOx的添加采用共浸渍)制备不同钨添加量的VOx-WOx/TiO2(VW/Ti)催化剂。采用XRD和EDS对VW/Ti催化剂样品进行表征,并考察催化剂催化燃烧氯苯的活性。结果表明,钨添加前,VOx/TiO2催化剂中TiO2以锐钛矿相和金红石相共存,锐钛矿相为主要晶相,同时还存在V2O5晶相;添加一定量钨后,催化剂中TiO2金红石相和V2O5晶相消失,W与Ti质量比0.024时,催化剂中活性组分VOx在载体TiO2表面分散最均匀,催化活性最高,T50和T90分别为226.72℃和298.67℃。W与Ti质量比0.12时,出现WO3晶相,催化活性略降。因此,适量添加钨不仅可以抑制TiO2由锐钛矿相向金红石相转变,还可以促进活性组分VOx在载体上的分散,进而改善催化剂催化降解氯苯的活性。

A series of VOx-WOx/TiO2 catalysts with five different W loadings were prepared using incipient- wetness impregnation method, and characterized by XRD, EDS. Their catalytic oxidation performance for chlorobenzene was investigated. The results of XRD characterization showed that before adding tungsten, anatase and rutile TiO2 coexisted in VOx/TiO2 catalyst with anatase TiO2 as the main crystalline phase, and there existed V2Os crystalline phase in VOx/TiO2 catalyst. The crystalline phases of rutile TiO2 and V2 O3 disappeared after adding a certain amount of tungsten. When the mass ratio of W to Ti was increased to 0. 024, the active component VOx dispersed well on the surface of the support, and the catalyst with Tso of 226.72 ℃ and T90 of 298, 67 % exhibited the highest activity for catalytic combustion of chlorobenzene. The crystalline phase of WO3 appeared with the increase of W/Ti mass ratio up to 0. 12 and the catalytic activity of the catalyst was slightly lower than that of the catalyst with W/Ti mass ratio of 0. 024. Therefore the addition of a certain amount of W to the V/Ti based catalyst could inhibit the TiO2 transition from anatase to rutile, and promote the dispersion of active component VOx on the support TiO2, and then improve the catalytic activity of the catalyst.