介孔二氧化钛的合成及应用

介孔二氧化钛特殊的结构和性能,使其在光催化,电化学器件等方面具有多种潜在的用途而备受关注,已经成为材料科学一个崭新的研究方向.本文综述了介孔二氧化钛的合成方法及应用,并对今后研究方向进行了展望.     

Kinetics of CO2 Adsorption/Desorption of Polyethyleneimine‐Mesoporous Silica

The kinetics of adsorption of CO₂ on solid sorbents based on polyethyleneimine/mesoporous silica (PEI/MPS) was studied by following the mass gain during CO₂ flow. Linear (PEI‐423) and branched (PEI‐10k) polymers were studied. The solid sorbents were synthesized by impregnating the PEI into MPS foam. The kinetics of adsorption was fitted with a double‐exponential model. In contrast, the desorption process obeyed first‐order kinetics. The activation energy of desorption of PEI‐423 was lower than that of PEI‐10k, presumably because the branched polymer required more energy to expose its nitrogen to CO₂. To increase the CO₂ sorption capacity, the MPS was treated with nonionic surfactant materials prior to impregnation with PEI. This also lowered the maximum sorption temperature and desorption activation energies.     

Filter Cake Washing of Mesoporous Particles

Particle synthesis in liquid phase usually requires a subsequent washing step in order to remove undesirable impurities such as unreacted educts, byproducts, solvents and salts. In particular, the washing of mesoporous particles is a challenging task due to large specific surface areas and void volumes. The filter cake washing of mesoporous SiO₂ particles contaminated either with an adsorbing fluorescent dye or sodium sulfate is presented. The effects of wash liquid mass flow rate, mean particle size, and mean pore size on the wash efficiency were investigated. Especially the interaction between impurities and the solid surface, and thereby the initial impurity distribution within the filter cake, led to distinctive washing behaviors.     

Study of the Preparation of Flavone Imprinted Silica Microspheres and Their Molecular Recognition Function

The aim of this study is to prepare flavone imprinted silica with good sphericity. Previous studies have demonstrated that imprinted silica can be synthesized using a simple sol‐gel method and a grinding‐sieving process. Despite the simplicity of the synthetic method, the appearance of the final product obtained is often very irregular and nonuniform. This product has many utilization issues and problems, e.g., residues and low operability. In this study, one type of novel spherical flavone imprinted silica was synthesized. A sol‐gel method and molecular imprinting technique were employed. By using luteolin as a template molecule, aminopropyltriethoxysilane (APTS) as the functional monomer, tetraethoxysilane (TEOS) as the cross‐linking agent, molecularly imprinted silica microspheres were prepared via a two‐stage reaction. The preparation conditions were monitored by the appearance of the products. SEM images show that under optimum conditions, the diameters of these microspheres are ca. 20–30 μm. The amino group adsorption peaks can be seen from the IR spectra. Results from elemental analysis indicate that 3.206 μmol of amino groups were successfully introduced into 1 g of product. This microspheric adsorbent has a high adsorption capacity to the template molecule, high adsorption selectivity and reproducibility. The adsorption capacity amounted to 32.987 mg/g and the separation factor was up to 84.3, while the adsorption capacity hardly decreased after 15 cycles.     

Structural,textural, surface chemistry and sensing properties of mesoporous Pr,Zn modified SnO2–TiO2 powder composites

Mesoporous Zn and Pr modified SnO₂-TiO₂ mixed powders (Sn:Ti:Zn:Pr contents 60:20:15:5) have been prepared by a modified sol–gel method involving Tripropylamine (TPA) as chelating agent, TritonX100 as template and Polyvinylpyrrolidone as dispersant and stabilizer, respectively. The obtained gels have been dried at different temperatures and calcined in air at 600 and 800 °C, respectively. Phase identification of the synthesized samples and their evolution with the calcination temperature has been performed by X-ray diffraction. N₂ adsorption/desorption isotherms were found to be characteristic for mesoporous materials, showing relatively low values for the specific surface area (15–32 m² g⁻¹) and nanometric sized pores. In case of the sample calcined at 800 °C, a bimodal pore size distribution can be observed, with maxima at 20 and 60 nm. SEM results demonstrate a porous nanocrystalline morphology stable up to 800 °C. The surface chemistry investigated by XPS reveals the presence of the elements on the surface as well as the oxidation states for the detected elements. At 800 °C a diffusion process of Sn from surface to the subsurface/bulk region accompanied by a segregation of Ti and Zn to the surface is noticed, while Pr content is unchanged. The sensing properties of the prepared powders for CO detection have been tested in the range of 250–2000 ppm and working temperatures of 227–477 °C.     

Effect of the Co‐SiO2 Mesoporous Layer Coating Step on the Performance of Liquid Fuel Dimethyl Amino Ethyl Azide Dehydration

A cobalt‐doped silica (Co‐SiO₂) layer was successfully synthesized in a sol‐gel process as the mesoporous layer overlaid in three‐, six‐, and ten‐step coating on a mullite support. The microporous layer was coated over the mesoporous layer in six steps by adopting the sol‐gel method. The membranes were applied in pervaporation experiments to dehydrate dimethyl amino ethyl azide (DMAZ) containing 5 wt % water. In dehydration tests, the membrane permeate flux decreased and its separation factor increased. During the first initial hours, it reached a steady state and subsequently remained constant.     

微波法合成MCM-41介孔分子筛及吸附性能研究

以十六烷基三甲基氯化铵为模板剂,在微波实验条件下合成MCM-41介孔分子筛,缩短了合成时间,降低产品成本。实验考察了多种因素对MCM-41合成的影响,并通过吸附处理亚甲基蓝溶液能力强弱,得到最佳合成条件：摩尔比1TEOS：0.2CTMACl：160H2O,pH为10,晶化时间15 min。通过红外光谱分析,MCM-41分子筛的主要特征吸收峰均已出现,说明合成分子筛MCM-41成功。     

蜂窝陶瓷载体介孔TiO2涂层的制备与表征

通过溶胶凝胶工艺制备ATS复相蜂窝陶瓷表面介孔TiO2涂层.研究了以冰醋酸为螫合剂的钛溶胶的优化配制,利用超声波振动测定涂层的结合强度,协同XRD、SEM及BET等显微表征手段对TiO2涂层进行微观分析和表征.实验表明:所制备的溶胶胶凝时间长、负载量大、比表面积大,500 ℃焙烧时,TiO2主要为锐钛矿晶型,介孔TiO2涂层与ATS复相蜂窝陶瓷具有高的结合强度.     

Synthesis,Characterization, and In Vitro Bioactivity of Sol‐Gel‐Derived Zn,Mg, and Zn‐Mg Co‐Doped Bioactive Glasses

Bioactive glasses in the systems CaO‐SiO₂‐P₂O₅‐ZnO, CaO‐SiO₂‐P₂O₅‐MgO, and CaO‐SiO₂‐P₂O₅‐MgO‐ZnO were prepared and characterized. Bioactive glass powders were produced by the sol‐gel method. The prepared bioactive glass powders were immersed in a simulated body fluid (SBF) for periods of up to 28 days at 310 K to investigate the bioactivity of the produced samples. Inductively coupled plasma (ICP) and ultraviolet (UV) spectroscopic techniques were used to detect changes in the SBF composition. X‐Ray diffraction (XRD) was utilized to recognize and confirm the formation of a hydroxyapatite (HA) layer on the bioactive glass powders. Microstructural characterizations of the bioactive glass samples were investigated by scanning electron microscopy (SEM) techniques. Density, porosity, and surface area values of bioactive glass powders were also determined in order to characterize the textural properties of the samples. The results revealed the growth of an HA layer on the surface of the bioactive glass samples. MgO in the glass sample increases the rate of formation of an HA layer while ZnO in the glass slows it down.     

室温水解法制备介孔二氧化钛的表征及应用

以氯化十六烷基吡啶为模板剂，在室温下直接合成出介孔TiO2，探讨了合成条件的影响，分别用红外光谱(FT-IR)、热分析(TG-DTA)，X射线粉末衍射(XRD)和N2吸附等温线技术对产物进行了表征．结果表明：样品经均三甲苯和磷酸处理后能有效提高比表面积和热稳定性，具有较高的光催化活性．     

金属掺杂介孔分子筛MCM-41的合成及结构表征

采用水热法合成了不同金属原子(M=Ce,Y,Nd)掺杂的MCM-41介孔分子筛M-MCM-41,采用X射线衍射(XRD)、N2吸附-脱附、透射电镜(TEM)、X射线光电子能谱(XPS)和NH3程序升温脱附(NH3-TPD)对M-MCM-41介孔分子筛的介孔结构,金属化合价态及表面酸性进行表征。结果表明,M-MCM-41介孔分子筛仍具有典型的六方介孔结构特征,样品比表面积、孔容积降低,孔径增大,引入分子筛中金属元素以M3+形态存在,金属离子的掺杂使M-MCM-41产生酸性位,对应中强酸。     

表面活性剂在有序介孔材料合成中的应用

有序介孔材料作为一种新型的纳米结构材料，在催化、分离、纳米技术、智能材料等领域有着广阔的应用前景。作为模板剂(结构导向剂)的表面活性剂在有序介孔材料的合成中起着十分重要的作用。本文对各种表面活性剂在有序介孔材料合成中的应用作了综述，分析了各种表面活性剂对有序介孔材料的合成、结构、性能的影响。     

Synthesis and Characterization of Amorphous Nano‐Alumina Powders with High Surface Area for Biodiesel Production

Nano‐alumina powders containing yttrium oxide were synthesized via the sol‐gel method using aluminum chloride hexahydrate as catalyst precursor. Fourier transform infrared analysis showed the presence of Al‐O and Al‐O‐Al bands in the powder structure and X‐ray diffraction spectra proved that the alumina was in the amorphous phase. The amorphous nano‐alumina powders were shown to be mesoporous with a high surface area, and both spherical and slit‐shaped particles were found in the calcined powder. A high percentage of conversion of oil to biodiesel was obtained in the transesterification reaction and the synthesized nano‐alumina powders could be easily regenerated for further use. The amorphous nano‐alumina powder can thus be recommended for use as active catalyst in the transesterification reaction for biodiesel production on the industrial scale.     

Synthesis and Characterization of Porous Single-Crystalline Titanium Dioxide Nanorods

Porous single-crystalline titanium dioxide (TiO₂) nanorods were prepared though a solution aggregation-based growth process followed by the calcination treatment. The products were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherm analysis. The prepared nanorods were of the single-crystalline nature and the mesoporosity characteristic. The prepared porous single-crystalline TiO₂ nanorods had high BET-specific area, 70.3 m²/g. The formation mechanism of the porous single-crystalline TiO₂ nanorods was also investigated. The solution aggregation-based growth of the nanoparticulates and the following calcination process may result in the formation of the porous single-crystalline TiO₂ nanorods.     

单分散介孔纳米载体合成及表征

通过St(o)ber法制备粒径约100 nm的SiO2纳米粒子,并以非离子表面活性剂嵌段共聚物为模板剂在纳米粒子表面再合成介孔SiO2层.在磷酸盐诱导剂的作用下可使核/壳结构的纳米粒子快速沉淀出来.再通过煅烧除去表面活性剂获得粒径均匀的球形介孔纳米载体.通过动态光散射(DLS)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、比表面积测定(BET)和氮气吸附脱附测定等技术对材料进行表征.纳米载体的平均有效粒径约为183 nm,介孔孔道为5.5 nm,具有良好的分散性(PDI:0.076),比表面积高达158.6 m2/g,孔容积0.22 cm3/g.结果表明,该法可以简单快速地制备纳米载体.     

High‐Temperature Capture of CO2 on Lithium‐Based Sorbents Prepared by a Water‐Based Sol‐Gel Technique

A convenient water‐based sol‐gel technique was used to prepare a highly efficient lithium orthosilicate‐based sorbent (Li₄SiO₄‐G) for CO₂ capture at high temperature. The Li₄SiO₄‐G sorbent was systematically studied and compared with the Li₄SiO₄‐S sorbent prepared by solid‐state reaction. Both sorbents were characterized by X‐ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. The CO₂ sorption stability was investigated in a dual fixed‐bed reactor. Li₄SiO₄‐G exhibited a special Li₄SiO₄ structure with smaller crystalline nanoparticles, larger surface area, and higher CO₂ adsorption properties as compared with Li₄SiO₄‐S. The Li₄SiO₄‐G sorbent also maintained higher capacities during multiple cycles.     

含钨介孔SiO2的合成、表征及其催化性能

分别以廉价硅酸钠与正硅酸乙酯为硅源,通过复合模板剂制备了介孔二氧化硅,并利用吸附相反应技术合成了WO3/SiO2复合催化剂。用XRD,TEM等手段对其结构进行了表征,通过油酸的催化氧化反应考察了催化剂的催化性能。     

二氧化锰的机械化学法制备及其性能

采用机械化学法制备了高比容量MnO2电容材料,考察了高锰酸钾与乙酸锰配比对产物结构及电化学性能的影响。用XRD对材料的结构进行了表征;用循环伏安、交流阻抗、恒电流充放电等方法分别研究了MnO2电极和超级电容器在6mol/LKOH水系电解液中的电化学性能。结果表明,当原料摩尔配比为1:1时,所得产物为无定型MnO2,其电极最大放电容量达到了536F/g。     

Synthesis and Characterization of Dendrimer-Templated Mesoporous Oxidation Catalysts

We report here the use of 4th and 5th generation dendrimers poly(propylene)imine (CU-D32 and CU-D64) as templating agents for the synthesis of mesoporous titanosilicate and vanadosilicate oxidation catalysts via solgel techniques. The physical properties of these mesoporous materials were characterized by TGA, BET, PXD and SEM/EDX analyses and these showed that the transition metals are evenly distributed throughout these silicates, which have interconnected spherical pores (approx. 12Å in diameter) and high surface areas of about 650m²g^–1. Kinetic studies showed that all transition metal-doped catalysts were highly selective at oxidizing cyclohexene to the corresponding epoxide. Additionally, CU-D64-templated catalysts were more catalytically active for cyclohexene epoxidation than CU-D32-templated catalysts as a result of differences in pore size. All CU-D64-templated catalysts exhibited epoxidation catalytic activity comparable to that of titanium doped MCM-41 materials.     

Preparation and Characterization of Mesoporous Zirconia Made by Using a Poly (methyl methacrylate) Template

Superfine powders of poly (methyl methacrylate) (PMMA) have been prepared by means of an emulsion polymerization method. These have been used as templates in the synthesis of tetragonal phase mesoporous zirconia by the sol–gel method, using zirconium oxychloride and oxalic acid as raw materials. The products have been characterized by infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, N₂ adsorption-desorption isotherms, and pore size distribution. The results indicate that the average pore size was found to be 3.7 nm.