Abstract:

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 V⁵⁺ and Ti⁴⁺ in the V₂O₅/CNTs-TiO₂ catalyst. The presence of V⁵⁺ and Ti⁴⁺ 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.

Key words: CNTs, CNTs-TiO₂ composite support, V₂O₅, Calcination temperature, Catalytic oxidation, Hexachlorobenzene