竹炭负载纳米TiO2吸附与降解甲苯的研究

以竹炭为载体,采用浸渍.焙烧法制备竹炭/纳米TiO2材料(竹炭-TiO2材料),利用SEM和EPR对竹炭及竹炭-TiO2材料进行表征,并分别在紫外灯、日光灯、白炽灯以及自然光照射条件下研究了竹炭-TiO2材料对甲苯的净化效果.结果表明:竹炭的孔隙主要以200nm左右的大孔为主,有利于TiO2在其表面和边沿的负载;竹炭-TiO2材料自旋数由8.7×1013(竹炭)增加到8.9×1017,氧化-还原能力显著提高;竹炭-TiO2材料对甲苯具有良好的净化能力,紫外光照射条件下,12 h净化率达94.50%,CO2增加量达122 mg/m3;在可见光条件下,12 h净化率为76.80%,CO2增加量为60mg/m3,CO2的增加可能是由于载体竹炭扩展了二氧化钛的光谱响应范围.     

Visible light induced electron transfer process over nitrogen doped TiO(2) nanocrystals prepared by oxidation of titanium nitride

Nitrogen doped TiO(2) nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO(2) nanocrystals can be clearly attributed to the change of the additional electronic (N(-)) states above the valence band of TiO(2) modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO(2) nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO(2).     

Catalytic conversion of 1,2-dichlorobenzene over mesoporous V2O5/TiO2 prepared from spray pyrolysis

Mesoporous V2O5/TiO2 particles were prepared by spray pyrolysis and applied to the catalytic oxidation of 1,2-dichlorobenzene (1,2-DCB). Two different precursors (alkoxide and nanoparticles) for the TiO2 support were used to determine the effects on the texture properties and the catalytic activity of the mesoporous V2O5/TiO2 particles. The 5 wt% V2O5/TiO2 particles had the largest surface area (173 m2/g) and 4.7 nm in average pore size. The catalytic activity of the V2O5/TiO2 particles depended strongly on the loading quantity of vanadium, whereas the P25-derived samples showed no significant change in catalytic activity with weight% of vanadium. The surface area of the V2O5/TiO2 particles prepared using the alkoxide precursor was larger than that of the particles prepared using P25 nanoparticles. The P25-derived V2O5/TiO2 particles, however, showed a higher catalytic activity compared with those alkoxide-derived, which is due to the difference in the vanadium quantity exposed to the pore surface. It was confirmed that the 10 wt% V2O5/TiO2 particles prepared by spray pyrolysis had an excellent activity for the oxidation of 1,2-DCB, particularly at temperatures below 300 degrees C.     

H2还原预处理CuO/γ-Al2O3催化剂对其催化燃烧甲苯活性的影响

用浸渍法和H2还原预处理法制备两种CuO/γ-Al2O3催化剂,并用N2吸附脱附、XRD、TPR和CO化学吸附对经H2还原处理前后的催化剂进行表征,比较两种催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,与浸渍法制备的CuO/γ-Al2O3催化剂相比,经H2还原预处理,再次焙烧后得到的CuO/γ-Al2O3/HR催化剂对甲苯催化燃烧活性明显提高。XRD和TPR分析表明,H2还原预处理提高了催化剂表面活性组分CuO的分散度、还原能力,同时,还降低了CuO的晶体尺寸,从而提高了催化剂催化氧化甲苯的活性。     

Properties of TiO(x) films prepared by electron-beam evaporation of titanium and titanium suboxides

The titanium suboxides TiO, Ti2O, and Ti3O5 are widely used to produce films of titanium dioxide by reactive evaporation. If they are evaporated in high vacuum, however, they yield absorbing TiO(x) films with a transmission color varying between blue and gray. We investigated the specific properties of these TiO(x) film. TiO, Ti2O3, Ti3O5, and titanium metal were evaporated in high vacuum upon glass substrates at 25 degrees and 250 degrees C. Differences in chemical composition, transmission and reflection, color, stress, and abrasion resistance of these fims, depending on the starting material and the substrate temperature, were evaluated.     

Comparison of nano-particulate TiO2 prepared from titanium tetrachloride and titanium tetraisopropoxide

Nanocrystalline titanium dioxides (TiO₂) prepared from (a) titanium tetrachloride (TiCl₄) and (b) titanium tetraisopropoxide (TTIP) have been compared. The effect of the reaction parameters on the phase formation of TiO₂ was investigated systematically. For TiO₂ prepared by hydrolysis of TiCl₄, the crystal phase changed with the speed of TiCl₄ addition and slow addition favoured the formation of rutile. For TiO₂ prepared by hydrolysis of Ti(OC₃H₇)₄, the reduction in hydrolysis rate associated with lower reaction temperatures promoted rutile formation. For both TiCl₄ and TTIP derived samples, increasing the anatase content decreased the measured rate of photocatalytic oxidation of isopropanol to acetone.     

Decomposition of TiO2-SnO2 solid solutions

Decomposition of TiO₂-SnO₂ solid solutions was studied using large-angle X-ray diffraction, transmission electron microscopy, electron diffraction, and small-angle X-ray scattering. Particular attention was devoted to the initial stages of decomposition of homogeneous solid solutions, so as to determine whether or not decomposition in the system can occur spinodally. All of our results indicate that alloys within the spinodal can decompose by a continuous and spontaneous process, i.e. spinodal decomposition does occur, whereas alloys outside the spinodal decompose by a discontinuous and non-spontaneous process, i.e. decomposition occurs by nucleation and growth.     

A new process for titanium aluminides production from TiO2

This paper describes a new process for producing titanium aluminides, in particular TiAl, from TiO2 raw material. On the basis of obtained results, the non-completed reaction of TiO2 with Al and Ca in a special reaction vessel results in the production of granulates of titanium aluminides especially Ti3Al and other Ti- Al phases as the metallic product and Ca12Al14O33 as the non-metallic product. By adding KClO4 in the mixture, a nearly completed reaction can be carried out. The products of this reaction are titanium aluminide particularly TiAl as the metallic part and CaAl4O7 （grossite） as the non-metallic slag part. Both product and slag are produced in a separated form. This process, called KRH-method is described in this article. The scanning electron microscopic microstructure of metallic part of the product shows different phases： the matrix phase is TiAI, where the needle form precipitation is TiAl2 and the plate form precipitation includes TiAI and Ti3Al phases. The microstructure of the remelted metallic part indicates dendritic phase with a lamellar structure comprising of TiAl and Ti3Al phases. The interdendritic phase of TiAI is also seen.     

Photocatalytic degradation of gaseous toluene over ZnAl2O4 prepared by different methods: a comparative study

The development of a "green" treatment process for typical indoor pollutants such as toluene is greatly desirable. In this study, ZnAl(2)O(4) nanoparticles were prepared via three different routes, i.e., solvothermal, citrate precursor and hydrothermal methods. Their structural properties were systematically investigated by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), energy-dispersive X-ray spectra (EDX), Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy (FT-IR) techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic performances of the ZnAl(2)O(4) samples and nanostructured TiO(2) samples were comparatively studied by the degradation of gaseous toluene under UV lamp irradiation in in situ FTIR reactor. The results indicated that the sample synthesized by facile solvothermal method exhibited about 90% photocatalytic efficiency of toluene. The toluene was mineralized into carbon dioxide and water as the major species. The photocatalytic oxidation of gaseous pollutant over UV-illuminated ZnAl(2)O(4) is a promising technique for air purification.     

Improved catalytic capability of mesoporous TiO2 microspheres and photodecomposition of toluene

A series of mesoporous titanium dioxide microspheres were calcined at various temperatures to improve their photocatalytic activity. The prepared catalysts were characterized by XRD, SEM, TEM, TG-DTA, UV-vis, and N(2) adsorption-desorption measurements, and their photocatalytic performances were investigated by photooxidation of gaseous toluene. As the results revealed, calcination temperatures obviously influenced the surface morphology and photocatalytic activity of the mesoporous TiO(2) microspheres. The noncalcined samples had a mesoporous structure of the anatase phase. The sample calcined at 400 °C showed a superior photocatalytic performance, which had a reaction rate constant 2-fold higher than that of P(25). The enhanced photoreactivity is possibly due to the synergetic effects of the mesoporous structure and light-transmittance ability of the catalysts. Two new reaction intermediates were discovered as well, and a tentative degradation pathway was proposed.     

乙二醇法制备负载型钴基-堇青石催化剂及其催化燃烧甲苯的活性

用乙二醇法和浸渍法制备两种负载在堇青石上的钴基负载催化剂,并用XRD、XPS、TPR和TPD对制备的催化剂进行表征,比较两种催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,与浸渍法制备的Co/cord催化剂相比,乙二醇法制备的催化剂Co/cord-EG对甲苯催化燃烧活性明显提高。应用乙二醇法制备Co/cord-EG负载型催化剂,Co元素主要以Co2+存在于载体表面;而传统浸渍法制备的Co/cord催化剂,Co元素是以Co2+与Co3+的两种化学状态存在于载体表面。应用乙二醇法制备Co/cord-EG负载型催化剂,有助于在载体表面形成比较均匀的吸附活性位。应用乙二醇法制备的Co/cord-EG催化剂,催化活性组分能在载体表面上以更小颗粒而且更高的分散度存在,从而能明显提高其催化活性。     

Synthesis of titanium dioxide (TiO2) nanomaterials

Titanium dioxide (TiO2) is a promising material for many emerging applications. Even more promising are the benefits offered by the material when its length scale is reduced to the nanometer range. Nanomaterials usually exhibit unique properties resulting from either the extremely large surface area-to-volume ratio or the quantum confinement effect of energy carriers. In this article we present an overview of recent progress in the synthesis of TiO2 nanomaterials. The topics include synthesis of TiO2 nanoparticles, nanorods, nanowires, nanotubes, and mesoporous/nanoporous materials using different preparation approaches such as sol-gel, sol, hydrothermal, solvothermal, and vapor deposition. The applications of TiO2 nanomaterials are also briefly summarized.     

Ti（SO4）2为钛源电沉积法制备TiO2薄膜的研究

以Ti(SO4)2为钛源采用阴极电沉积法在导电玻璃上生成TiO2薄膜。采用单因素法分析了电压、pH、时间等因素对阴极电沉积TiO2薄膜的影响,确定了电沉积液最佳配方和工艺条件,并采用XRD、SEM、TG-DTA等分析手段进行了表征。实验结果表明:阴极电沉积法制备TiO2薄膜的最佳配方及工艺条件为10mL Ti(SO4)2,3mLH2O2,2mLHNO3,8mL NH3.H2O,20mL H2O,pH为1.5,电压为3.5V,沉积时间为20min。在此条件下,在导电玻璃上能够形成一层均匀TiO2薄膜,经XRD检测该膜层晶型为锐钛矿,该膜层可应用于染料敏化太阳能电池、光催化等领域。     

Microwave-assisted preparation of nanocluster rutile TiO2 from titanium slag by NaOH-KOH mixture activation

Rutile titanium dioxide is widely used in coatings, cosmetics, paper products, and other industries as the source of white inorganic pigment. The common preparation methods of rutile from titanium slag include the molten salt method, hydrochloric acid method, oxidation–reduction method, etc. In this paper, the NaOH-KOH sub-molten salt method was used to activate titanium slag. After a series of subsequent leaching processes and an attached roasting process with the assistance of microwave technology, a nanocluster was formed by nanorods with a diameter below 100 nm and a length below 500 nm. It is found that titanate changes to the stable metantitanate at a temperature of 80 °C in the process of acid leaching. Moreover, the relationship between the concentration of sub-molten salt, calcination temperature, and titanium leaching rate was analysed by kinetics. The results show that the leaching rate of titanium reached the peak when the mixed alkali concentration was 15 mol/L, and the leaching rate of titanium reached the maximum value when the roasting temperature was 450 °C. According to the Arrhenius equation, the activation energy of titanium slag in the NaOH-KOH sub-molten salt system was 130.8 kJ/mol. The pre-exponential factor was 5.44 × 10^-4 m²/s, and a chemical reaction process controlled the whole process.     

提拉法制备高透光率超亲水性TiO2薄膜及性能分析

采用溶胶-凝胶法结合提拉工艺在载玻片上制备TiO2薄膜,分别以不同温度(200℃、250℃、300℃、350℃、400℃、450℃、500℃)对薄膜进行退火处理2h.用X射线衍射及扫描电镜测试样品的微观结构和表面形貌,用紫外-可见分光光度计和接触角测量仪分别测试薄膜的透射光谱和水接触角.结果表明,所有样品均为透明薄膜,在可见光范围内平均透光率均大于70％;薄膜光学带隙随退火温度升高依次降低;水接触角随退火温度升高依次减少,当退火温度为450℃和500℃时,水接触角分别为2.5°和2°,薄膜表现为超亲水性.     

Dielectric and microstructural properties of sintered BaTiO3 ceramics prepared from different TiO2 raw materials

BaTiO₃ ceramics, sintered from powders previously synthesized using TiO₂ of different characteristics, have been studied. The microstructural development depended on the crystalline nature and impurity types and levels, when the same sintering schedules were applied. Anatase leads to BaTiO₃ powders which showed a controlled grain growth after sintering. Rutile with very low impurity levels gave materials in which a non-uniform grain growth was promoted. Dielectric constant and loss tangent were measured and correlated with the density and microstructure. From these correlations, it seems that the raw materials' nature has a greater effect on the dielectric properties that the sintering schedule of a given material.     

Thermochromism of vanadium–titanium oxide prepared from peroxovanadate and peroxotitanate

Vanadium–titanium complex oxides were prepared through a new synthetic route from peroxovanadate and peroxotitanate solutions, and their thermochromism were investigated. Reflectance spectra for V_0.48Ti_0.52O₂ pellet showed a reversible reflectivity increase in the wavelength region of 700–1,000 nm above 45 °C. The reflectivity was increased gradually from 45 °C to ca. 80 °C unlike the conventional VO₂ which shows an abrupt increase at 67 °C. The mechanism was discussed using powder XRD patterns, SEM images and element distribution maps.     

Formation process of mixed silicon and titanium carbide from copyrolysis of polysilane and metallic titanium: Part II

In part I we reported a copyrolysis of polysilane with metallic tungsten [1]. Now copyrolysis of chlorine containing polysilane with metallic titanium addition in the range of 0–10 at % Ti was performed. A significant decrease of the mass loss during the polysilane pyrolysis was observed. Also the specific surface area, gas evolution and occuring phase formation changes. The titanium forms preferently carbides and temporary silicides depending on the applied pyrolysis temperature. The reactions are controlled by transport phenomena of carbon and titanium. In the end of the process silicon carbide (SiC) and titanium carbide (TiC_x) are stable.     

Oxidation of gas phase trichloroethylene and toluene using composite sol-gel TiO2 photocatalytic coatings

The previously developed composite sol-gel (CSG) process is proposed for the deposition of thick (10-50 microm) porous films of photocatalytic TiO2. The CSG titania was developed by binding pre-calcined TiO2 particles with TiO2 sol. It had relatively high surface area (15-35 m2/g) and good resistance against mechanical stress and abrasion. Photocatalytic activity tests were carried out on trichloroethylene (TCE) and toluene, and compared with those of standard Degussa P-25 titania. The CSG photocatalyst provided good photo-efficiency in removing both pollutants from contaminated air streams. When compared with P-25 titania, the CSG photocatalyst showed a similar photo-efficiency with first-order kinetic rate constants not significantly different from that of P-25. For both photocatalysts the rate of photocatalytic oxidation of TCE was significantly greater than that obtained for toluene. Overall, the combination of better mechanical integrity, resistance against abrasion, and comparable photocatalytic efficiency of the CSG titania versus that of P-25 titania, make the composite sol-gel (CSG) photocatalyst a viable alternative for industrial applications where long term stability, superior mechanical properties, and good photo-efficiency are of critical value.