焙烧温度对V_2O_5/CNTs-TiO_2催化剂脱氯性能的影响

Influence of Calcination Temperature on Dechlorination Performance of V_2O_5/CNTs-TiO_2 Catalysts

用浓硝酸纯化改性碳纳米管(CNTs),以钛酸四丁酯为原料,通过溶胶-凝胶法制备碳纳米管-氧化钛(CNTs-Ti O2)复合载体并浸渍制得V2O5/CNTs-Ti O2催化剂,重点考察了制备过程中焙烧温度对催化剂催化氧化活性的影响.利用扫描电镜(SEM)、X射线衍射(XRD)仪、X射线光电子能谱(XPS)仪和紫外-可见(UV-Vis)分光光度计等对催化剂材料的结构、形貌和表面化学性质进行了表征分析.结果表明,硝酸处理后的碳纳米管纯度和石墨化程度增加,450°C焙烧温度制备得到的催化剂活性组分分散度好,V2O5/CNTs-Ti O2催化剂中钒钛氧均以有利于催化反应的价态存在;催化剂表面活性氧的含量最高,催化剂表现出很好的电子迁移与氧移动的能力,从而提高催化剂的催化活性.实验表明,在250°C、催化剂用量为0.2 g、N2(80%)+O2(20%)下催化降解六氯苯(HCB)的效率可达到94.78%左右,并在24 h内保持很好的稳定性.

Carbon nanotubes（CNTs） pretreated with concentrated HNO3 and tetrabutyl titanate were used as raw materials to prepare CNTs-TiO2 composite supports by the sol-gel method. Vanadium was then dipped into the CNTs-TiO2 composite support to synthesize the V2O5/CNTs-TiO2 catalyst. The influence of calcination temperature on the active species of the catalyst and the catalytic oxidation performance for degradation of hexachlorobenzene（HCB） were investigated. The synthesized catalysts were characterized using scanning electron microscopy（SEM）, X-ray diffraction（XRD）, and ultraviolet-visible（UV-Vis） spectroscopy. The surface chemical properties were analyzed by X-ray photoelectron spectroscopy（XPS）. The results indicated that the modified carbon nanotubes have high purity and graphitization degree. The effect of calcination temperature on the active components and the activity of the catalyst were investigated. The results showed that calcination at 450 ℃ favored the dispersion of the active species of the catalyst and the formation of catalytic oxidation valences of V^5＋ and Ti^4＋ in the V2O5/CNTs-TiO2 catalyst. The presence of V^5＋ and Ti^4＋ increased the concentration of the surface oxygen of the catalyst, resulting in a higher catalytic activity because of promotion of the electron mobility and oxygen transfer： 94.78% of HCB can be conversed with a loading of 0.2 g of the catalyst in an atmosphere of N2（80%） ＋ O2（20%） at 250 ℃. The conversion of HCB remained above 90% during a 24 h batch test, which showed a stable catalytic performance.