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Monodisperse spherical periodic mesoporous organosilicas (PMOs) with ethane integrated in the framework were synthesized and their application as stationary phase for chromatographic separation is demonstrated. The ethane-PMOs were prepared by condensation of 1,2-bis(triethoxysilyl)ethane (BTSE) in basic condition using octadecyltrimethylammonium chloride (C(18)TMACl) as template and ethanol as co-solvent. The morphology and mesoporous structure of ethane-PMOs were controlled under different concentrations of sodium hydroxide (NaOH) and EtOH. The results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), nitrogen sorption measurement, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis showed that ethane-PMOs have spherical morphology, uniform particle distribution, highly ordered pore structure, high surface area and narrow pore-size distribution. The column packed with these materials exhibits good permeability, high chemical stability and good selectivity of mixtures of aromatic hydrocarbons in normal phase high-performance liquid chromatography (HPLC). 相似文献
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Qi Wei Li Liu Zuo-Ren Nie Hui-Qiao Chen Jing-Xia Zou 《Journal of Sol-Gel Science and Technology》2007,44(2):105-110
Fluorocarbon groups were used to modify the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation
of 1,2-Bis(triethoxysilyl)ethane (BTESE) and trifluoropropyltrimethoxysilane (TFPTMS) in the presence of Poly(ethylene glycol)-B-Poly(propylene
glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The functionalized materials were investigated
in detail by means of XRD, TEM, FT-IR, solid-state NMR, and N2 adsorption. The effect of fluorocarbon groups concentration on the mesoscopic order and pore structure of the functionalized
materials was also studied. The results show that bridging groups in the framework do not cleave and fluorocarbon groups are
attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The samples functionalized
with 20% TFPTMS remain desired mesoporous architecture, with a narrow pore size distribution centered at 4.1 nm, a large surface
of 834 m2/g and a pore volume of 0.91 cm3g−1, without pronounced change compared to the pure periodic mesoporous organosilica. Unfortunately the functionalized materials
become structurally disordered with increasing amount of fluorocarbon groups. 相似文献
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Borah P Ma X Nguyen KT Zhao Y 《Angewandte Chemie (International ed. in English)》2012,51(31):7756-7761
Selective benzene hydroxylation: A periodic mesoporous organosilica embedded with a vanadyl(IV) acetylacetonate complex has been synthesized through a co-condensation method. This system is a catalyst for direct hydroxylation of benzene to phenol, presenting a selectivity of 100?% towards the phenol formation as well as an excellent catalytic recyclability (see scheme). 相似文献
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George W. Scherer 《Journal of Sol-Gel Science and Technology》1994,3(1):31-40
The permeability (D) of a gel can be determined by analysis of its thermal expansion kinetics: as the gel is heated, the expanding liquid stretches the solid network like a spring; during an isothermal hold, the liquid drains out and the gel returns to its initial dimensions at a rate that depends on D and the elastic modulus of the network. However, if the network is too rigid or D is too high, the dilatation of the network may be too small to measure easily. The measured expansion increases with the viscosity of the pore liquid, so D is easier to measure after the gel is rinsed in a higher alcohol. For example, a thermally aged silica gel that shows no measurable expansion in ethanol exhibits a large thermal strain after the pore liquid is changed to 1-octanol. It is important to demonstrate that the same permeability is obtained regardless of the liquid employed (i.e., that flow in the small pores of the gel does not give rise to liquid-specific effects), so we examine the thermal expansion of a silica gel rinsed successively in ethanol, 1-octanol, and 1-decanol; the gel is compliant enough so that D is measurable in all these liquids. The permeability is found to be the same, but the expansion is much more easily measured for the more viscous alcohols. 相似文献
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《Journal of Saudi Chemical Society》2020,24(10):777-784
A series of periodic mesoporous organosilica supported benzotriazolium ionic liquids were synthesized and tested as effective and practical heterogeneous catalysts in the condensation reaction of diphenylethanedione, aromatic aldehydes and ammonium acetate. The catalyst PMO@ILBF4(1.0) showed brilliant catalytic activity for the synthesis of 2,4,5-trisubstituted imidazoles with good to high yields. We also found that the catalytic activity could be significantly influenced by the loading levels and functional anions of the benzotriazolium-cation ionic liquid, probably due to an intensification of intramolecular synergistic effect. Furthermore, the multifunctional catalyst PMO@ILBF4(1.0) could be easily recovered by filtration and recycled for six times with no significant loss in activity, indicating its excellent stability and reusability. This method provides an efficient and environmentally-friendly procedure for the production of 2,4,5-trisubstituted imidazoles. 相似文献
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制备高碳醇Cu-Fe系催化剂的比表面积、孔结构和孔径分布 总被引:14,自引:0,他引:14
用ASAP-2000型物理吸附仪,研究了制备高碳醇Cu-Fe系催化剂的比表面积、孔结构、孔容积和孔径分布等.结果表明,随着焙烧温度的提高,比表面积下降;在相同的焙烧温度下,组成和沉淀过程的pH值也影响其表面积大小.催化剂的活性与反应可利用的表面积相关.根据吸附-脱附等温线,确定了催化剂的孔结构及孔径分布的变化规律.数据表明,孔径分布和孔容积对催化剂的活性至关重要,平均孔径(4V/A,根据BET)可作为衡量Cu-Fe系催化剂活性高低的一个参数.焙烧温度的选择是使催化剂具有适宜的孔径分布和较大的孔容积,因而具有较高活性的重要条件 相似文献
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The synthesis and catalytic application of a novel MgO containing periodic mesoporous organosilica with ionic liquid framework (MgO@PMO‐IL) is described. The prepared MgO@PMO‐IL was characterized by Fourier transform‐infrared spectroscopy, N2 adsorption/desorption, transmission electron microscopy, field emission‐scanning electron microscopy, thermogravimetric and inductively coupled plasma analyses. This nanocatalyst was successfully applied as a highly efficient and recoverable catalyst for the synthesis of novel spirooxindole‐furan derivatives via the three‐component reaction of 1,3‐dicarbonyl compounds, N‐phenacyl pyridinium salts and isatin derivatives. The products were achieved in high to excellent yields with a simple work‐up procedure and short reaction times, and the catalyst could be recovered through a simple filtration process and successfully reused seven times without any significant decrease in its efficiency. 相似文献
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Periodic mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) was prepared and used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography–mass spectrometry (GC–MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n = 3), expressed as relative standard deviation (R.S.D.%), was between 4.3% and 9.7% for the test compounds. The detection limits for the studied compounds were between 4 and 9 pg mL−1. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis. 相似文献
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论文提出用积分渐进展开解析气相色谱重叠峰,该方法有3个主要步骤:首先将谷峰或肩峰分成两个积分区域,得到一个子区域的积分方程和一个重叠峰面积的代数方程;然后用数值积分求出这两个方程计算中所需要的峰面积,再用积分渐进公式将积分方程展开成代数方程;最后,将这两个方程与峰高约束方程联立后,得到一个非线性代数方程组,用Gauss-Seidel迭代可以快速求解方程组,方程收敛的最大迭代次数不超过20次。仿真和实验结果表明,解析的峰高和峰面积误差均很小,峰面积最大误差低于6.44%,峰高的最大误差约为6.80%。由于该算法精度高,效率高,所以这个方法可以用于气相色谱重叠峰和一般色谱峰的实时在线解析。 相似文献
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Hartlen KD Athanasopoulos AP Kitaev V 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):1714-1720
Highly monodisperse spherical silica nanoparticles with diameters ranging from ca. 15 to 200 nm were prepared using an environmentally friendly water-based synthesis. The size of the spheres can be precisely controlled by using a facile regrowth procedure in the same reaction media. Furthermore, these monodisperse silica spheres can be successfully used as seeds in the well-established St?ber silica preparation. The regrowth approach allows for easy incorporation of functional additives. High monodispersity and charge stabilization renders these nanoparticles highly suitable for close-packed array formation and colloidal templating. 相似文献
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An analytical method based on high-performance liquid chromatographic (HPLC) with ultraviolet (UV) detection was developed for determination of scopolin in rat plasma using aesculin as internal standard (IS). After protein precipitation of plasma sample with methanol, the supernatant was directly injected and analyzed. Chromatographic separation was achieved on a C18 column using methanol and distilled water (22:78, v/v) containing 0.2% (v/v) glacial acetic acid as mobile phase with a column temperature of 30 degrees C. The UV detector was set at 338 nm. The calibration curve was linear over the range of 0.105-13.125 microg/mL with a correlation coefficient of 0.9998. The retention times of aesculin and scopolin were 10.4 and 12.8 min, respectively. The recoveries for plasma samples of 0.105, 4.725 and 13.125 microg/mL were 91.08, 95.30 and 96.10%, respectively. The RSD of intra- and inter-day assay variations was less than 7.35%. The lower limit of detection was 0.03 microg/mL .This HPLC assay is a simple, sensitive and accurate and was successfully applied to the pharmacokinetic study of scopolin in rats. 相似文献
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Shunsheng Cao Xin Jin Xinhua Yuan Weiwei Wu Jie Hu Weichen Sheng 《Journal of polymer science. Part A, Polymer chemistry》2010,48(6):1332-1338
This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010 相似文献
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Te-Fang Yang Zhong-Nian Zhang Chih-Hao Tseng Li-Hsun Chen 《Tetrahedron letters》2005,46(11):1917-1920
Formyl borneol, a [2.2.1]-bicyclic carbinol, reacts with various Grignard reagents to produce corresponding alkyl [3.2.1]-bicyclic diols, which can be converted to new highly substituted cyclopentanes, and further to 3-acyl-bornylenes. These ring expansion-alkylation reactions are highly selective. Reaction of formyl isoborneol with methyl magnesium bromide gave ring expansion-only and alkylation-only products. 相似文献
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Pore Geometry and Surface Engineering of Covalent Organic Frameworks for Anhydrous Proton Conduction
Liqin Hao Shuping Jia Xueling Qiao En Lin Yi Yang Prof. Yao Chen Prof. Peng Cheng Prof. Zhenjie Zhang 《Angewandte Chemie (International ed. in English)》2023,62(6):e202217240
Developing new materials for anhydrous proton conduction under high-temperature conditions is significant and challenging. Herein, we create a series of highly crystalline covalent organic frameworks (COFs) via a pore engineering approach. We simultaneously engineer the pore geometry (generating concave dodecagonal nanopores) and pore surface (installing multiple functional groups such as −C=N−, −OH, −N=N− and −CF3) to improve the utilization efficiency and host–guest interaction of proton carriers, hence benefiting the enhancement of anhydrous proton conduction. Upon loading with H3PO4, COFs can realize a proton conductivity of 2.33×10−2 S cm−1 under anhydrous conditions, among the highest values of all COF materials. These materials demonstrate good stability and maintain high proton conductivity over a wide temperature range (80–160 °C). This work paves a new way for designing COFs for anhydrous proton conduction applications, which shows great potential as high-temperature proton exchange membranes. 相似文献