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1.
Surface immobilization of active species onto mesoporous materials is gaining importance, especially in the design of functionalized mesoporous materials as a nanocatalyst through heterogenization of homogeneous catalytic systems. This article summarizes recent work on the synthesis, characterization and catalytic performance of the functionalized mesoporous catalysts performed by the present authors. A cationic rhenium(I) complex was encapsulated into mesoporous Al-MCM-41 molecular sieve using a ion-exchange method, yielding a new photocatalyst to be active for photocatalytic reduction of CO2. Surface functionalization of mesoporous silica SBA-15 with sulfonic acid groups was investigated to give a solid acid catalyst. The chemically modified Fe-containing mesoporous materials, which are active for hydroxylation of phenol, were prepared by a surface-grafting method that iron salts are immobilized onto mesoporous Si-MCM-41 with the help of 3-aminopropyltrimethoxysilane as a linker. A cobalt(III) complex was heterogenized onto mesoporous silica SBA-15 containing carboxylic groups in order to utilize as a solid catalyst for the liquid-phase oxidation of aromatic hydrocarbons.  相似文献   

2.
This paper reports an electrochemical study of ordered mesoporous silica impregnated with a cationic dye (o-toluidine blue), prepared with a non-ionic surfactant as the structure-directing agent. O-toluidine blue was chosen because of its utility as an electron transfer mediator (redox catalyst). O-toluidine blue impregnated mesoporous silica was characterized by nitrogen sorption porosimetry, small angle X-ray scattering, infrared spectroscopy, scanning electron microscopy and cyclic voltammetry using chemically modified carbon paste electrodes. Results indicate that the dye is located within the ordered mesopores of micron-sized silica spheres.  相似文献   

3.
In this work, pure MCM-41 mesoporous silica with active mesoporous sites has been successfully applied, as a highly efficient and recoverable catalyst, for the rapid and convenient synthesis of α-aminonitriles and imines. Various imines, as the intermediate of the Strecker reaction, were simply prepared from condensation of a wide range of aldehydes and amines in the presence of low loading of MCM-41 mesoporous silica under solvent-free conditions at room temperature in high to quantitative yields. Furthermore, the corresponding α-aminonitrile derivatives were prepared through the three-component Strecker reaction using trimethylsilylcyanide catalyzed by MCM-41 as a bifunctional heterogeneous mesoporous solid catalyst.  相似文献   

4.
In this paper, a facile strategy is reported for the preparation of well‐dispersed Pt nanoparticles in ordered mesoporous silica (Pt@OMS) by using a hybrid mesoporous phenolic resin‐silica nanocomposite as the parent material. The phenolic resin polymer is proposed herein to be the key in preventing the aggregation of Pt nanoparticles during their formation process and making contributions both to enhance the surface area and enlarge the pore size of the support. The Pt@OMS proves to be a highly active and stable catalyst for both gas‐phase oxidation of CO and liquid‐phase hydrogenation of 4‐nitrophenol. This work might open new avenues for the preparation of noble metal nanoparticles in mesoporous silica with unique structures for catalytic applications.  相似文献   

5.
The catalytic upgrading of a lignin-derived bio-oil model compound, the hydrodeoxygenation of guaiacol, was performed using mesoporous solid catalysts. Platinum supported on silica and mesoporous silica (SBA-15 and KIT-6) were used as catalysts. The level of platinum incorporation and aluminum grafting did not alter the physical properties of the supports, such as surface area and pore size distribution. On the other hand, these treatments drastically affected the catalytic activities. A catalyst with platinum alone converted guaiacol to oxygenate compounds. In contrast, a series of catalysts with both platinum incorporation and aluminum grafting enhanced hydrodeoxygenation by converting guaiacol into hydrocarbons (cyclohexane and benzene). A comparison of the catalyst supports revealed the ordered mesoporous silica, SBA-15 and KIT-6, with high surface area, to have a higher hydrocarbon yield than conventional silica.  相似文献   

6.
介孔硅材料由于具有大的比表面积,均一的孔结构和大的孔径,常被用于分离、吸附和催化等领域.本文综述了近年来国内外介孔硅材料及其负载型催化剂去除各类挥发性有机物(VOCs)的研究进展,主要包括烃类、甲醇、甲醛、丙酮、苯、甲苯、萘、乙酸乙酯等.讨论了介孔硅材料的结构对VOCs吸附过程的影响;介绍了不同催化剂消除各类VOCs的催化性能及反应机理,并重点评述了甲苯在不同催化剂上的研究进展.分析结果表明,介孔硅材料的表面环境、孔道结构以及宏观形貌是影响VOCs分子在介孔硅材料上吸附的主要因素;贵金属催化剂的应用需要提高其抗中毒性以及降低成本;过渡金属的研究应着重于研发高活性的负载型过渡金属复合氧化物催化剂.最后对国内外介孔硅材料及其负载型催化剂的发展进行了展望,今后催化剂的设计可以从“氧化硅载体”和“介孔孔道”两个方面展开,这将为设计合适的催化剂处理各类VOCs污染物提供一定参考.  相似文献   

7.
采用十六烷基三甲基溴化铵(CTAB)为模板剂,四乙氧基硅烷(正硅酸乙酯,TEOS)为硅源,硝酸为催化剂来制备介孔SiO2,并采用后嫁接法对介孔SiO2进行氨基化改性。利用红外光谱(IR),X射线粉末衍射(XRD),差热-热重分析(DTA-TG),扫描电镜(SEM),元素分析,微电泳法及N2吸附-脱附方法对改性前后的产物进行表征。结果表明氨基已成功嫁接到介孔SiO2孔道中,改性后的介孔SiO2有序度有所下降,但仍为介孔材料;改性之后介孔材料的孔径、比表面积、孔体积均变小。等电点由原来的2.74变为4.75。本文还以氨基修饰的介孔SiO2为载体,通过交联剂戊二醛固定诺维信(Novozymes)工业级漆酶,并采用正交设计法对固定化条件进行了优化。研究表明漆酶经固定化后,其操作稳定性比游离酶高。  相似文献   

8.
A novel magnetically separable mesoporous silica‐supported palladium catalyst was designed and prepared for the selective hydrogenation of naphthalene to tetralin, which is an important transformation from a practical viewpoint. In the catalyst, Pd nano grains were dispersed uniformly and protected within the mesoporous silica shells being coated on the Fe3O4 core, so that the durability of the catalyst could be significantly improved.  相似文献   

9.
哌啶改性氨丙基介孔分子筛的原位漫反射红外表征   总被引:1,自引:0,他引:1  
张翠  周玮  路平  刘双喜 《分子催化》2006,20(2):176-178
介孔材料具有很大的比表面和很规则的孔大小及孔形状,以化学键键合有机基团的介孔材料又兼有官能团的特性,实现了不少有机均相催化剂的固载.与广泛应用的酸性分子筛相比,人们很少关注碱性介孔材料.经过研究者们的不断工作,固体碱可以应用于Knoevenagel反应、Michael加成、单甘油脂合成反应等方面,原位红外技术具有方便、实时、准确、有效等优点.可以检测样品对气体的吸附,或者在真空、惰性等条件下对样品焙烧的情况.  相似文献   

10.
先将Pd纳米粒子负载于SiO2球表面上,再经包裹、刻蚀、硅烷化修饰,得到氟丙基功能化“蛋黄”型结构催化剂.并采用X射线衍射、透射电镜、N2吸附-脱附和热重等对催化剂进行了表征.结果表明,该催化剂在水相烯烃加氢反应中表现出较高的活性,明显高于未经氟丙基修饰的同类催化剂.该催化剂通过离心便可实现回收,多次循环使用后仍保持较高的活性.  相似文献   

11.
研究了柱层析硅胶-K2CO3固体碱催化剂的制备条件,并对其进行XRD、FT-IR和SEM表征分析。结果表明,部分K2CO3吸收空气中的CO2生成KHCO3,K2CO3与 KHCO3分散到硅胶表面,增强了催化效果。并考查了催化剂用量、醇油摩尔比、反应时间对生物柴油制备的影响。研究表明,催化剂的制备温度为120℃,催化剂用量为原料油质量的5%,醇油摩尔比为12∶1,反应温度70℃,反应时间2h,生物柴油收率可达95.2%。  相似文献   

12.
Periodic mesoporous silicas, which were prepared from silica‐surfactant mesostructured materials, have been investigated for a wide range of application due to their very large surface area, high porosity, pore size uniformity and variation, periodic pore arrangement and possible pore surface modification, after the pioneering papers on the formation of mesoporous silicas (MCM‐41 and FSM‐16). Morphosyntheses from such macroscopic morphologies as bulk monolith and film to nanoscopic ones, nanoparticles and their stable suspension, make mesoporous materials more attractive for applications and detailed characterization. Mesoporous silicas have been studied initially for such applications as adsorbent and catalyst, and more recently, optical, electronic, and bio‐related applications have been investigated. This review summarizes the studies on mesoporous silica film to highlight the present status and future of the preparation, characterization and application of the mesoporous silica film.  相似文献   

13.
Highest catalytic performance for complete oxidation of propylene and toluene was obtained by using a Pt catalyst on a mesoporous silica support with pore sizes from 20 to 50 nm and 10 to 40 nm, respectively.  相似文献   

14.
Although Au catalysts can be readily prepared on titania via the deposition-precipitation (DP) method, the direct application of the method similar to the preparation of silica-supported Au catalysts only results in diminished success. This paper reports a novel, efficient method to synthesize highly active Au catalysts supported on mesoporous silica (SBA-15) through a gold cationic complex precursor [Au(en)2]3+ (en = ethylenediamine) via a wet chemical process. The gold cationic precursor was immobilized on negatively charged surfaces of silica by a unique DP method that makes use of the deprotonation reaction of ethylenediamine ligands. The resulting mesoporous catalyst has been demonstrated to be highly active for CO oxidation at room temperature and even below 273 K, the activity of which is much superior to that of silica-supported Au catalysts previously prepared by various solution techniques. The pH value of the gold precursor solution plays a key role in determining the catalytic activity through the regulation of [Au(en)2]3+ deprotonation reaction and the surface interaction of silica with the gold precursor. This mesoporous gold silica catalyst has also been shown to be highly resistant to sintering because of the stabilization of Au nanoparticles inside mesopores.  相似文献   

15.
《Comptes Rendus Chimie》2016,19(10):1247-1253
High surface area mesoporous silica based catalysts have been prepared by a simple hydrolysis/sol–gel process without using any organic template and hydrothermal treatment. A controlled hydrolysis of ethyl silicate-40, an industrial bulk chemical, as a silica precursor, resulted in the formation of very high surface area (719 m2/g) mesoporous (pore size 67 Å and pore volume 1.19 cc/g) silica. The formation of mesoporous silica has been correlated with the polymeric nature of the ethyl silicate-40 silica precursor which on hydrolysis and further condensation forms long chain silica species which hinders the formation of a close condensed structure thus creating larger pores resulting in the formation of high surface mesoporous silica. Ethyl silicate-40 was used further for preparing a solid acid catalyst by supporting molybdenum oxide nanoparticles on mesoporous silica by a simple hydrolysis sol–gel synthesis procedure. The catalysts showed very high acidity as determined by NH3-TPD with the presence of Lewis as well as Brønsted acidity. These catalysts showed very high catalytic activity for esterification; a typical acid catalyzed organic transformation of various mono- and di-carboxylic acids with a range of alcohols. The in situ formed silicomolybdic acid heteropoly-anion species during the catalytic reactions were found to be catalytically active species for these reactions. Ethyl silicate-40, an industrial bulk silica precursor, has shown a good potential for its use as a silica precursor for the preparation of mesoporous silica based heterogeneous catalysts on a larger scale at a lower cost.  相似文献   

16.
Several mesoporous silicas with different morphologies were controllably prepared by sol-gel method with adjustable ratio of dual template,and they were further impregnated with aqueous solution of nickel nitrate,followed by calcination in air.The synthesized silica supports and supported nickel samples were characterized using N_2-adsorption/desorption,X-ray diffraction(XRD),H_2 temperature-programmed reduction(H_2-TPR),Scanning electron microscope(SEM),Transmission electron microscope(TEM) and thermo-gravimetric analysis(TGA-DTG) techniques.The Ni nanoparticles supported on shell-like silica are highly dispersed and yielded much narrower nickel particle-size than those on other mesoporous silica.The methane reforming with dioxide carbon reaction results showed that Ni nanoparticles supported on shell-like silica carrier exhibited the better catalytic performance and catalytic stability than those of nickel catalyst supported on other silica carrier.The thermo-gravimetric analysis on used nickel catalysts uncovered that catalyst deactivation depends on the type and nature of the coke deposited.The heterogeneous nature of the deposited coke was observed on nickel nanoparticles supported on spherical and peanut-like silica.Much narrower and lower TGA derivative peak was founded on Ni catalyst supported on the shell-like silica.  相似文献   

17.
A new nucleophilic catalytic system comprised of dialkylaminopyridine-functionalized mesoporous silica nanosphere (DMAP-MSN) has been synthesized and characterized. We have demonstrated that this material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability. We envision that this DMAP-functionalized mesoporous silica material can also serve as an effective heterogeneous catalyst for many other catalytic nucleophilic reactions.  相似文献   

18.
Research on Chemical Intermediates - VO2(picolinichydrazone) complex as a catalyst was stabilized on a SBA-15 mesoporous silica as a catalytic support by using (3-chloropropyl)triethoxysilane as a...  相似文献   

19.
Recent progress on the chemical immobilization of heteropolyacid (HPA) catalyst on inorganic mesoporous material is reported in this review. Mesostructured cellular foam silica, mesoporous carbon, and nitrogen-containing mesoporous carbon were used as supporting materials. The mesoporous materials were modified to have a positive charge, and thus, to provide sites for the immobilization of HPA catalyst. By taking advantage of the overall negative charge of heteropolyanion, the HPA catalyst was chemically immobilized on the surface-modified mesoporous material as a charge-compensating component. Characterization results showed that the HPA catalyst was finely and molecularly dispersed on the surface of mesoporous material via strong chemical immobilization, and that the pore structure of mesoporous material was still maintained even after the immobilization of HPA catalyst. The supported HPA catalysts were applied to the model vapor-phase ethanol conversion, 2-propanol conversion, and methacrolein oxidation reactions. The supported HPA catalyst showed a better oxidation catalytic activity than the unsupported HPA catalyst in the model reactions. The enhanced oxidation catalytic performance of the supported HPA catalyst was attributed to the finely dispersed HPA catalyst, which was chemically immobilized on the positive site of mesoporous material by sacrificing its proton (Brönsted acid site). The HPA catalyst chemically immobilized on mesoporous material served as an excellent oxidation catalyst.  相似文献   

20.
We have synthesized a series of nanocatalysts with different sizes (50-200 nm) for polymerization of 1,3-butadiene (Bd) by immobilizing salicylaldimine cobalt complexes on the mesoporous silica nanoparticles (MSNs). The prepared catalysts have been characterized by infrared (IR) spectra, thermal gravimetric analyses (TGAs), chemical composition analysis, nitrogen adsorption-desorption, scanning electron microscope (SEM), and transmission electron microscope (TEM). The nanocatalysts in combination with methylaluminoxane (MAO) show excellent catalytic efficiency in polymerization of 1,3-butadiene. The results reveal that these nanocatalysts also show higher activity than the homogeneous analog of cobalt complex and the same catalyst on bulky mesoporous silica supporting materials. The yield and the molecular weight of the poly-butadiene product depend on the particle size of the catalyst support. This catalysis process is also a facile way to directly synthesize the polymer/silica composite materials.  相似文献   

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