Effect of inductively coupled plasma surface treatment on silica gel and mesoporous MCM-41 particles

Silica gel and MCM-41 synthesized mesoporous materials were treated with either oxygen（O_2）,hexamethyldisiloxane（HMDSO） and organic vapors like ethanol（Et OH）,and acrylonitrile（AN）inductive plasma.The radiofrequency power for the modification was fixed to 120 W and30 min,assuring a high degree of organic ionization energy in the plasma.The surface properties were studied by infrared spectroscopy（FTIR）,scanning electron microscopy,x-ray photoelectron spectroscopy and dynamic light scattering technique was used for characterizing size distributions.When the silica and MCM-41 particles were modified by AN and HMDSO plasma gases,the surface morphology of the particles was changed,presenting another color,size or shape.In contrast,the treatments of oxygen and Et OH did not affect the surface morphology of both particles,but increased the oxygen content at the surface bigger than the AN and HMDSO plasma treatments.In this study,we investigated the influence of different plasma treatments on changes in morphology and the chemical composition of the modified particles which render them a possible new adsorbent for utilization in sorptive extraction techniques for polar compounds.

Facile H2O2 Hydrothermal Synthesis of Bimodal Mesoporous Silica MCM-48 Spheres

The ordered bimodal mesoporous silica MCM-48 spheres were facile synthesized by mild- temperature post-synthesis H2O2 hydrothermal treatment of as-synthesized MCM-48. The results showed that H2O2 is indispensable for simultaneously removing organic templates and forming ordered bimodal mesoporous silica MCM-48 spheres. The bimodal mesoporous MCM-48 was characterized by X-ray diffraction, transmission electron micrographs, FT-IR, and N2 adsorption-desorption, and a possible mechanism was proposed for the formation of bimodal mesoporous MCM-48.

Synthesis and Characterization of Mesoporous Materials MCM-41 Incorporated by Yttrium, Neodymium and Samarium

Using cetyl-trimethyl-ammonium bromide （CTMAB） as template and tetraethylortho-silicate （TEOS） as silica source, the MCM-41 mesoporous materials incorporated in framework by Y, Nd and Sm were synthesized by hydrothermal synthesis method. The structure, morphology of materials and the state of Y, Nd, Sm in materials were investigated by means of XRD, nitrogen adsorption-desorption, SEM, IR spectrometry, TG-DTA. The XRD results indicate that the samples possess the mesoporous MCM-41 structures with ordered hexagonal arrangements. Y, Nd and Sm ions can get into the framework of mesoporous materials. Nitrogen adsorption desorption isotherms show that the samples have typical mesopores characteristics. SEM micrographs reveal that incorporated sampies show a spherical morphology and the diameters are averagely 0. l0 to 0.15 μm. In IR spectrum of samples, there are the feature adsorption peaks about Si-O-Ln（Ln=Y, Sm, Nd）at 960-985 cm^-1, which affirm that Y, Nd, Sm ions locate in the framework of several mesoporous materials. Results from TG-DTA analysis suggest that two different template sorption sites exist in the framework of YMCM-41, SmMCM-41, NdMCM-41, which powerfully proves that the presence of Y, Nd and Sm in Si framework of the materials.

Thin Film of Mesoporous MCM-41 Grown on Indium-Tin-Oxide Glass Substrate

From a basic solution containing celyltrimethylammonium cations as the template, thin film of mesoporous MCM-41 has been grown on the surface of a pre-treated indium-tin-oxide conducting glass substrate. The channel axis of the film is oriented parallel with the surface plane of the substrate, and the film is stable after careful removal of template in vacuum.

Synthesis and Characterization of Mesoporous Silicon Oxynitride MCM-41 with High Nitrogen Content

Mesoporous silicon oxynitrides MCM-41 were synthesized successfully. The resulting materials not only have high nitrogen contents and good structural characteristics of MCM-41 (high surface area, narrow pore size distribution and good order), but also are amorphous. The composition and structure of the materials were investigated by CNH element analysis, XPS, Si MAS NMR, XRD, HRTEM and N-2 sorption, respectively. Mesoporous silicon oxynitrides MCM-41 with a high nitrogen content are still non-crystal (amorphous).

Removal of Fluoride from Water Using Mesoporous MCM-41: An Optimization Approach Using Response Surface Methodology (RSM)

Fluoride above 1.5 mg·L-1 is injurious to health. Removal of fluoride from water using mesoporous MCM-41 as a strong adsorbent material has been attempted. Characterization using transmission electron microscopic study of calcined MCM-41 showed the regular hexagonal array of mesoporous channels with an average size of 20 nm and the surface area (BET study) of 1306.96 m2·g-1. The average pore size of the particles was found to be 14.21 nm. A study on the effect of contact time on the removal of fluoride revealed that more than 85% uptake of fluoride onto MCM-41 was achieved at a contact time of 120 min. From the Langmuir adsorption study, the maximum sorption capacity of fluoride was found to be 63.05 mg/g at 301 K. From the thermodynamic study, the +ΔHo value of 2.29 kJ·mol-1 indicated the endothermic nature of the removal process. Application of Response Surface Model suggested that 77.88% of fluoride removal can be achieved at fluoride concentration of 10 mg·L-1, pH (6.3), and contact time of 120 min.

Synthesis and Characterization of Mesoporous Materials MCM-41 Incorporated by Yttrium, Neodymium and Samarium

Using cetyl-trimethyl-ammonium bromide （CTMAB） as template agent and tetraethylorthosilicate （TEOS） as silica Source, the MCM-41 mesoporous materials were synthesized with Y, Nd and Sm incorporated in the framework under hydrothermal conditions. The structure and the micro-morphology of the materials and the state of Y, Nd and Sm were investigated through the analyses of XRD, nitrogen adsorption-desorption isotherm, SEM, IR and TG-DTA. The XRD resuits indicate that the synthetic samples are of typical structure of mesoporous MCM-41 with ordered hexagonal arrangements, and Y, Nd and Sm can be incorporated into the framework of these mesoporous materials. Nitrogen adsorption-desorption isotherms show that the samples possess the typical mesopores character. SEM micrographs reveal that the incorporated samples show a well-defined spherical morphology with the diameter ranging 0.10 - 0.15μm. The occurrence of two different template sorption sites in the framework as revealed by TG-DTA analysis further suggests the presence of Y, Nd and Sm in siliceous framework.

Large Pore Mesoporous MCM-41 Templated from Cetyltriethylammonium Bromide

Following hydrothermal synthesis process, MCM-41 was synthesized by using cetyltriethylammonium bromide as templating agent. The experimental results showed that MCM-41 with pore diameter in the range of 4-7 nm can be obtained by adjusting nsurf/nsi. It was proved that cetyltriethylammonium bromide is an effective templating agent for increasing pore diameter of molecular sieve MCM-41.

Synthesis of Mesoporous Molecular Sieve MCM-41 in Extremely Dense System

Mesoporous molecular sieve MCM-41 has been synthesized in the extremely dense system (with H2O/Si<10) and characterized by XRD, N-2 adsorption isotherm as well as probe reactions of cracking of cumene and isomerization of o-xylene.

Simultaneous Removal of Surfactant Template from MCM-41 and Implantation of Transition Metal Complexes into Mesopores with Supercritical Fluid

The simultaneous removal of up to 92% of the surfactant template and chemical implantation of transition metal complexes into mesopores has been successfully achieved by treating as-synthesized pure siliceous MCM-41 with supercritical CO2 modified with CH2Cl2/MeOH mixture, resulting in the formation of functionalized material with uniform pore structure.

Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Brφnsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.

Preparation,Characterization and Catalytic Activity of Palladium Nanoparticles Embedded in the Mesoporous Silica Matrices

Novel in-situ reduction approach was applied for the synthesis of palladium nanoparticles in the pores of mesoporous silica materials with grafted siliconhydride groups. Matrices possessing different structural properties (MCM-41, SBA-15 and Silochrom) were used. Samples were studied by nitrogen adsorption-desorption method, low-angle X-ray diffraction, transmission electron microscopy (TEM) and FT-IR/PAS spectroscopy. The temperature-programmed oxidation (TPO) and reduction (TPR) methods were applied to examine reducibility of palladium species. Palladium containing catalysts were tested in methane oxidation reaction. It was demonstrated that relatively large pores in SBA-15 type silica facilitated formation of well-dispersed palladium nanoparticles confined in the pores channels. In the case of MCM-41 support, metallic palladium nanoparticles were formed on the external surface. The obtained materials showed high catalytic activity. Lower activity of the samples containing small crystallites located in the pore volume at high temperatures was related to worse accessibility of active sites to the reation mixture.

Synthesis of Mesoporous Material from Chrysotile-Derived Silica

Mesoporous MCM-41-type molecular sieves were synthesized using calcined and leached chrysotile and cetyltrimethylammonium bromide as the silica source and structure directing agent, respectively. Powder X-ray diffraction (XRD), N2 isothermal adsorption-desorption, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the samples. The calcined and leached chrysotile can be employed as an inexpensive silica source for the formation of low-order MCM-41 mesoporous materials.

水玻璃为原料在开放体系中快速合成介孔材料MCM-41

A convenient and economic method for preparing highly ordered MCM 41 was studied in an open vessel by using waterglass as the silicon source. XRD, nitrogen adsorption and TEM show that the product has a highly ordered structure and the hexagonal arrangements of uniformly size pores distribution.

以硅溶胶和三氯化钛为原料合成Ti-MCM-41分子筛 Ⅰ.Ti-MCM-41分子筛的合成

以硅溶胶和TiCl3 水溶液为原料 ,采用水热合成方法制备了结晶度和长程有序性较高的中孔Ti MCM 41分子筛 .钛的加入提高了中孔分子筛的长程有序性 .辅助模板剂的选择对分子筛的合成很重要 ,其中以四甲基氢氧化铵和四乙基氢氧化铵作辅助模板剂的效果较好 .四甲基氢氧化铵的用量对分子筛的结晶度和长程有序性也有影响 ,用量过高和过低都会降低分子筛的结晶度 .合成的分子筛中的钛含量 (摩尔分数 )可以达到 3 75 % ,进一步增加钛的含量 。

MCM-41中孔SiO_2分子筛合成新方法

以溴代十六烷基吡啶（CPBr）为模板剂，正硅酸乙酯（TEOS）为硅源，在优化的操作条件下通过S＋X-I+路径合成了高结晶度的MCM－41中孔SiO2分子筛，并提高了其收率；以TG－DTA结果为基础，对分子筛脱模板剂的过程进行了优化，同时以XRD对合成物系中CPBr；TEOSHCl，H2O相对含量对MCM－41分子筛晶相结构的影响以及该结构的形成过程进行了分析，发现MCM－41结构沿S＋X-I+路径的形成经过了Lamellar→Hexagonal相转移历程.

铕配合物[C_5H_5NC_(16)H_(33)][Eu(TTA)_4]在改性介孔材料Si-MCM-41孔道中的组装研究

It was proved by ICP, fluorescence spectra and N 2 adsorption that the rare earth complex [C 5H 5NC 16H 33] [Eu(TTA) 4] is in the channel of Si-MCM-41 in the course of assembly. The rare earth complex of 67.9% is in the channel, suggesting that the assembly of the complex molecular on the mesoporous MCM-41 was carried out mainly in the channel.

反应介质对MCM-41介孔分子筛合成的影响研究

采用正硅酸乙酯为硅源 ,表面活性剂十六烷基三甲基溴化铵为结构模板剂 ,用水热晶化法在碱性介质 (NaOH)和用室温直接法酸性介质 (HCl)中 ,分别合成出MCM 41介孔分子筛样品 ,通过XRD、IR、TG、N2 等温物理吸附等测试手段对这两种样品进行对比表征分析 ,考察了不同反应介质对其晶体结构。

硅源对纯硅MCM-41介孔分子筛结构性能的影响

分别采用正硅酸乙酯(TEOS)、气相法白炭黑、硅溶胶为硅源,十六烷基三乙基溴化铵(CTEAB)为结构导向剂,在100℃用水热晶化法在碱性(NaOH)介质中反应5d,合成出MCM-41介孔分子筛样品。通过XRD、N2吸附-脱附测试手段对不同硅源合成的样品进行了对比表征分析,实验结果表明,相对于TEOS作为硅源,气相法白炭黑和硅溶胶制得的MCM-41具有较大的孔径(>4nm)和孔容(>1cm3/g)以及高的比表面积(1000m2/g),在制备大孔径的介孔MCM-41时,气相法白炭黑和硅溶胶是两种比较好的硅源。

ZrO_2/MCM-41催化的苯乙酮氢转移反应

通过浸渍法分别制备了硅胶(SiO2)、全硅MCM-41介孔分子筛负载ZrO2催化剂,考察其在以异丙醇为氢源,苯乙酮的氢转移反应中的催化性能,并与纯ZrO2进行对比,同时对各催化剂进行XRD、N2吸附-脱附、XPS、吡啶原位吸附红外等表征分析。结果表明:与纯ZrO2相比,负载型催化剂活性明显增加,归因于ZrO2与载体发生强相互作用,形成Si-O-Zr键,使催化剂表面的Zr-OH数目显著增加,出现B酸中心,且L酸中心强度增强。ZrO2/MCM-41的催化活性优于ZrO2/SiO2,可归因为前者中ZrO2的分散程度较高。ZrO2/MCM-41的最佳ZrO2负载量为5%(wt);最佳反应时间8 h;最佳异丙醇和苯乙酮摩尔比为10:1。苯乙酮含吸电子取代基后转化率升高,而含供电子取代基后转化率降低。5%ZrO2/MCM-41的催化活性随重复使用次数增加而逐渐降低。