EXAFS characterization of Ti/Al2O3 supports and Co/Ti/Al2O3 catalysts

The structure of Ti/Al₂O₃ supports (0–14 wt% Ti) and Co/Ti/Al₂O₃ catalysts (3 wt% Co) was examined by EXAFS. The results indicated that the Ti was present primarily as a highly dispersed surface phase. The Ti EXAFS results indicated that the Ti species were octahedrally coordinated. Evidence of Ti—Ti interactions was found for all loadings (2–14 wt% Ti) suggesting that the Ti surface species are present as small clusters of TiO₂.The Co EXAFS results showed evidence for several structurally different Co surface phases as a function of Ti loading. Evidence of a Co species interacting with the Ti surface phase was observed for the 3% Co/2% Ti-3%Co/6%Ti catalysts. At the highest loadings studied, 3%Co/8%Ti and 3%Co/14%Ti, evidence was found for a CoTiO₃-like phase.     

Effect of synthesis temperature on the preparation of titanium dioxides by the hydrothermal method. photocatalytic activity

Summary TiO₂ nanoparticles were prepared by the hydrolysis of titanium tetraisopropoxide (TTIP) using TMA (tetramethylamine) as a peptizer in the hydrothermal method. The photocatalytic degradation of Orange II has been studied in a batch reactor under UV light. The particle size was similar to that from hydrothermal treatment at 120-170^oC, but it increased to 23 nm at 200^oC. The titania particles prepared at 170^oC and calcined at 600^oC showed the highest activity in the photocatalytic decomposition ofOrange II.     

锐钛矿型纳米TiO2粉体的精细结构及其光催化降解苯酚的活性

  摘要：以Ti（SO4）2·4H2O和尿素为原料，以聚乙二醇－1000为空间构 造剂，制备了不同粒径的具有高热稳定性的锐钛矿型纳米TiO2粉体，并 用XRD，BET和EXAFS技术对其晶相、粒径大小、比表面积及中心Ti原子 的K－边精细结构进行了表征，对其光催化降解苯酚反应的活性进行了 考察．结果表明，未经任何热处理的TiO2粉体即为锐钛矿型晶相，控制 焙烧温度可以达到控制其粒径及比表面积的目的．经850℃焙烧5h的样 品仍保持锐钛矿型晶相，未出现向金红石型晶相转变的迹象．随着纳米 TiO2晶粒的增大，Ti原子局域结构的有序度增强，边前结构A1，A2和A 3三个特征峰的强度增强，各壳层的配位数均呈增大的趋势．粒径处于 15～20nm的锐钛矿型TiO2粉体对光催化降解苯酚表现出较高的活性．     

Electrochemical analysis of the sol-gel synthesis of phosphonate-modified titania through the diffusion of a functionalised ferrocene

Titanium oxide/phenylphosphonate hybrids were prepared by a two-step sol-gel processing, in the presence of ferrocenylphosphonic acid as an electrochemical probe. We showed that as expected the diffusion of the redox species was related to the kinetics of the sol-gel polymerization. The probable passage through cluster Ti₄O(OⁱPr)₈(PhPO₃)₃ has been confirmed by the electrochemical response under partial hydrolysis conditions.     

可见光照射下染料茜素红的光催化降解机理

研究了 可见光（ ≥４２ ０ ｎ ｍ ） 照射下 染料茜素 红在空气 饱和 的 Ｔｉ Ｏ２ 水溶 液中 发生 的光 催化降解过 程． 借 助紫外 、核磁、顺 磁、红外 、色质 联用等手 段,发现 染料茜素 红的光 催化 降解 过程 符合 Ｌａｎｇ ｍ ｕｉｒ Ｈｉｎｓｈｅｌｗ ｏｏｄ 模型,在 降解过程 中产 生了 过氧 化 物． 核磁 、红 外和 色质联 用等 结 果证 实,主要降解 中间产 物为邻苯 二甲酸 ． Ｃ Ｏ Ｄ 测试 结 果表 明, 其矿 化产 率 达３ ０ ％ , Ｅ Ｓ Ｒ 结 果证 实, 在降解过程 中有 ⒒ Ｏ Ｈ 自由基 生成,说 明其与 染料的降 解机理有 密切联 系．     

95 ℃水溶液体系中TiCl4溶胶水解法制备纯金红石纳米粉体(英)

Titanium dioxide (TiO2) nanoparticles of rutile phase were synthesized by hydrolysis of TiCl₄ at 95 ℃ in aqueous solution. The samples as prepared and calcined at 500 ℃ were characterized by XRD, TG-DTA and TEM. The sample as prepared was of imperfect rutile structure, and its morphology was rod-like with a diameter of 10～20 nm, a length of 20～80 nm and an aspect ratio of 2～4. The structure of the sample calcined at 500 ℃ was a perfect rutile one, and its morphology was rod-like with a diameter of 15～25 nm, a length of 25～105 nm and an aspect ratio of 2～4. These results indicate that calcination temperature has a positive effect on the structure and the size of rutile nanocrystals, and has no effect on the aspect ratio of rutile nanocrystal. A model for the formation mechnism of rutile nanocrystal in aqueous solution under hydrolysis conditions has been proposed.     

Preparation and photocatalytic behavior of TiO2-carbon nanotube hybrid catalyst for acridine dye decomposition

A new kind of hybrid catalyst, TiO₂-carbon nanotubes, was prepared via sol-gel method for the first time. Its photocatalytic activity in the photodegradation of acridine dye aqueous solution at low concentration was tested. There was no measurable effect on the formation of crystalline phase of TiO₂ catalyst with the addition of 10 wt.% carbon nanotubes to TiO₂ samples. AFM photograph of TiO₂-carbon nanotubes sintered at 300°C showed that the carbon nanotubes were enwrapped by TiO₂, which greatly increased the adsorbing ability of the catalyst and was in favor of photocatalytic reaction. Compared with naked TiO₂ powder the hybrid catalyst prepared in this way showed high efficiency in the photodecomposition of acridine dye.     

纳米TiO2-SiO2复合光催化剂的超临界流体干燥法制备及其光催化性能研究

本文以廉价无机盐Na₂SiO₃·9H₂O和TiCl₄溶液为原料,采用化学包覆结合超临界流体干燥(SCFD)法制备纳米级TiO₂-SiO₂复合光催化剂。利用XRD、TEM、NMR等手段对复合粉体进行了表征。结果表明,采用超临界流体干燥法可直接制得锐钛矿型TiO₂-SiO₂纳米复合光催化剂,其中SiO₂以单分散、无定形形式存在。以苯酚和邻苯二酚紫光催化降解为反应模型,考察了TiO₂-SiO₂复合光催化剂的催化性能。证明掺入适量SiO₂的TiO₂-SiO₂纳米复合光催化剂既减少了TiO₂的用量、降低了成本,又在某种程度上提高了TiO₂的光催化活性。SiO₂的引入可以有效抑制纳米粒子粒径的长大和晶相的转变,增强了二氧化钛纳米粒子的热稳定性。二氧化硅的最优掺杂量为15%(质量分数)。     

Titania on Silica. A Comparison of Sol-Gel Routes and Traditional Methods

Titania on silica samples have been prepared by: i) precipitation-deposition from a solution of TiCl₃ onto the surface of a commercial silica, and ii) base catalysed hydrolysis-condensation of TEOS followed by reaction with Ti isopropoxide. These samples were characterised by nitrogen and hydrogen adsorption, X-ray diffraction, FTIR, temperature programmed reduction, transmission electron microscopy and catalytic activity in butane-hydrogen conversion. The sol-gel preparation produced a better titania dispersion due to the formation of stabilising Ti-O-Si bonds. Upon these samples was then introduced Ir. Strong metal-support interactions between Ir and titania have been observed after high temperature reduction, causing a significantincrease in butane dehydrogenation activity relative to hydrogenolysis.It appears that using sol-gel chemistry useful supports for catalytic metals containing Si-O-Ti linkages can be produced and in future may be optimised for other metal-oxygen metal pairs.     

模板剂及Ni掺杂对中孔TiO2材料性能的影响

1992年美国Mobil公司首次报道了以离子型表面活性剂为模板剂通过水热法合成了中孔二氧化硅及硅铝材料，由于此类材料具有较大的孔径和比表面积以及优良的吸附性能，在较大的分子或基团的反应中具有较大的优势，引起了催化、吸附分离、无机合成及材料科学等许多领域研究者的广泛关注，许多不含硅的具有半导体性能的中孔氧化物材料在光催化、气体传感、局部氧化、完全燃烧、NOx降解、加氢脱硫等方面显示出优良的性能，二氧化钛是一类应用很广的氧化物。