纳米二氧化钛的改性及光催化氧化烷烃研究

Study on the fabrication and photocatalytic properties of Nano-TiO_2 catalyst

催化剂的表面结构是影响催化反应的重要因素之一。利用原位红外(In-situFT-IR)、X射线衍射(XRD)和紫外-可见漫反射(UV-VisDRS)等现代物理技术考察了热处理改性对纳米TiO2的表面结构、晶相结构、粒子大小、比表面积和吸光性能的影响,采用In-situFT-IR光谱着重研究了纳米TiO2催化剂上环己烷光催化降解机制及催化剂的结构特性与催化反应之间的相关性。研究表明,400℃条件下热处理纳米TiO2具有最佳光催化活性,适宜的表面结构、晶相结构、吸光能力及晶化度是纳米TiO2光催化剂高催化活性的主要原因。借助In-situFT-IR光谱,观察到环己烷氧化的主要产物是CO2和H2O,同时捕捉到了中间产物CO以及乙酸,提出了环己烷光催化降解的可能机理。

It was well known that the surface structure of the catalyst was one of the most important factors to govern the catalytic activity. In-situ FT-IR, XRD and UV-Vis DRS were adopted to characterize the surface structure, phase structure, particle size, specific surface area and absorbency of UV radiation of nano-TiO2 nano-photocatalyst, which was thermal treated under programmed temperature in air atmosphere and in-situ FT-IR was used to investigate that photocatalytic degradation processes of cyclohexane over the pre-treated nano-TiO2 samples. The relationship between the surface structure of the catalyst and their photocatalytic properties were also correlated. The results indicated that the nano-TiO2 treated at 400 ℃showed the optimum photocatalytic activity. The suitable surface structure, phase structure, absorbency of UV radiation and degree of crystallization were found to be the critical factors to tail the photocatalytic activity of the samples. It could be observed from the in-situ FT-IR spectra of photocatalytic degradation of gas-phase cyclohexane species that CO2 and H2O were the major product, whereas some intermediate products CO and acetic acid were detected in the above-mentioned photocatalytic reactions. Based on the obtained results, a possible mechanism of photo-catalytic degradation of gas-phase cyclohexane species was proposed and discussed.