全硅MCM-41中孔分子筛的合成

在碱性条件下,采用水热晶化法,以水玻璃为硅源,表面活性剂十六烷基三甲基溴化铵为结构模板剂,成功合成出全硅MCM－41中孔分子筛。采用X射线衍射分析研究了合成条件(pH值）、凝胶配比（表面活性剂／SiO2、H2O/SiO2）和凝胶后处理条件（老化时间、晶化温度、晶化时间和焙烧温度）对MCM－41结构的影响。结果表明全硅MCM－41的合成条件为pH10.5-12.5,表面活性剂／SiO20.05-0.7,H2O/SiO2 40－200,老化时间长对合成晶形较的全硅MCM－41有利。晶化温度70℃-100℃,晶化时间24小时,焙烧温度540℃－740℃。     

氧化硅有序介孔材料MCM-41的微波水热合成及用于组装ZnO纳米粒子

与传统水热合成工艺相比,采用微波水热合成新工艺可以快速合成比表面积大、孔体积和孔径大、孔径分布范围更窄、孔洞呈六方排布的有序介孔材料MCM-41.微波水热合成工艺合成的MCM-41具有合成效率高、成功率高等特点,为此类介孔材料商业化提供了高效的技术手段.采用传统水热工艺合成MCM-41通常需要48～72 h,而采用微波水热合成技术仅需要30 min.采用X射线粉晶衍射(XRD),氮气吸附等技术手段对合成MCM-41材料的物相、比表面积、孔体积、孔径等进行了表征.采用微波水热合成MCM-41的工艺参数为:微波处理的温度120 ℃,时间30 min,微波辐射功率500 W,经过滤、洗涤、干燥、焙烧等处理后,得到的MCM-41具有六方排布的孔系,晶格常数a0=4.4nm,比表面积可达1113 m2/g,平均孔径为2.7 nm,与选用同样配方采用传统水热合成工艺合成的MCM-41的性能相当,却极大提高了合成效率.采用微波水热合成工艺,同样可以合成立方晶系的MCM-48和六方晶系的SBA-15等介孔氧化硅分子筛材料.此外,在微波合成的MCM-41中采用液相工艺成功组装了ZnO纳米粒子,并对组装在MCM-41中的纳米ZnO粒子进行了光催化降解苯酚的实验研究.     

Nitridation of Amorphous Silica with Ammonia

The reaction between amorphous silica and ammonia in the temperature range 200° to 1230°C has been investigated. The reaction process was monitored with respect to the nitrogen content of the reaction product, the specific surface area of the amorphous nitrided silica, and the decomposition of ammonia. A surface reaction was observed at temperatures between 300° and 500°C, but in agreement with other studies bulk reaction only occurred above 800°C, reaching its maximum rate at about 1000°C. It is suggested that the decomposition of ammonia, which also becomes important above 800°C, is essential for the bulk nitridation reaction. At temperatures above 1050°C the nitridation yield decreases, until gas-phase reaction between SiO( g ) and N₂ or NH₃ becomes dominant at 1230°C, leading to the formation of α-Si₃N₄.     

Well-Dispersed Gallium-Promoted Sulfated Zirconia on Mesoporous MCM-41 Silica

Gallium-promoted sulfated zirconia (SZ) was confined inside pure-silica MCM-41 (abbreviated as SZGa/MCM-41), where the latter served as a host material. It was prepared by direct dispersion of metal sulfate in the as-synthesized MCM-41 materials, followed by thermal decomposition. The SZGa/MCM-41 catalysts were characterized by XRD, N₂ adsorption, HRTEM, DRIFT, NH₃-TPD, and TPR. The experimental results showed that the ordered porous host structure was still maintained in the catalyst. SZ was in meta-stable tetragonal phase and highly dispersed on the interior surface of MCM-41 even at a high loading of 50 wt%. Additionally, a small fraction of SZ nanoparticles on the external surface of MCM-41 was obtained. The catalytic activity of SZGa/MCM-41 was examined in n-butane isomerization. In comparison to SZ/MCM-41 without promoter, the catalytic activities of the Ga-promoted catalysts were greatly improved. The reason proposed for the higher activity of the Ga-promoted catalysts was that Ga enhances the oxidizing ability of the catalysts.     

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。     

Separation and Recovery of Tetramethyl Ammonium Hydroxide with Mesoporous Silica Having a Hexagonal Structure (MCM-41)

Separation and recovery of tetramethyl ammonium hydroxide (TMAH) was investigated using several types of MCM-41 (mesoporous silica having hexagonal structure) adsorbents. The MCM-41s were prepared by hydrothermal synthesis with structure-directing agents with different alkyl chains. The prepared MCM-41s were characterized with X-ray diffraction, transmission electron microscope, nitrogen gas adsorption, and zeta potential, and then used for adsorption of TMAH. The adsorption of TMAH with MCM-41s increased with pH up to pH ≈ 10 and then decreased as the MCM-41 dissolved. The adsorption of TMAH progressed via the Langmuir mechanism. The maximum adsorption corresponded to the pore diameter and the pore volume of the MCM-41s. MCM-41 also possesses selectivity for TMAH against phenol. The chromatographic operation was conducted using granulated MCM-41 to avoid excessive pressure-drop through the packed column and quantitative adsorption-elution processing of TMAH could be achieved.     

Thermochemical Nitridation of Microporous Silica Films in Ammonia

Microporous silicon dioxide thin Films were deposited on silicon substrates from a solution of tetraethoxysilane, ethanol, and water. These were converted to dense oxynitrides through a high-temperature reaction with ammonia. The ammonia treatments yielded amorphous, compositionally homogeneous films with overall nitrogen contents ranging up to 40 mol%. For ammonia treatments below 800°C, nitrogen was incorporated into the films as an amine species, whereas higher temperature treatments produced a nitride material.     

全硅介孔分子筛MCM-41的表面修饰及其疏水性

在极性溶剂(丙酮)或非极性溶剂(甲苯)中,用三甲基氯硅烷对全硅介孔分子筛MCM-41进行了表面修饰。利用IR、XRD和低温N2吸附-脱附等手段对样品进行了结构分析;并通过测定样品在水或正庚烷饱和蒸汽中的吸附量,研究了它们的疏水性。实验结果表明,表面改性后的MCM-41仍保持完好的介孔结构,由于有机官能团接枝在MCM-41的内表面,占据了孔道内部空间,使其比表面积、孔容和孔径都减小。样品的疏水性与其硅烷化程度成正关系,且在非极性溶剂中表面修饰的样品表现出更好的疏水性能。     

Mechanical Stability of Mesoporous Materials, MCM-48 and MCM-41

The structural collapse of mesoporous molecular sieves, MCM-48 and MCM-41 materials by mechanical compression was found to occur mechanochemically through hydrolysis of Si–O–Si bonds. Their ordered structures were retained by compressing the well-dried samples under dry N2. Trimethylsilylation of mesoporous materials proved effective in eliminating their instability to compression through enhancing hydrophobicity.     

介孔分子筛MCM-41的发展现状

介孔分子筛MCM-41具有较大的比表面积、良好的吸附容量以及热稳定性,成为人们研究的热点。介绍了MCM-41的制备方法、制备机理以及MCM-41的改性。     

介孔分子筛MCM-41的合成探索

以正硅酸乙酯(TEOS)为硅源、十六烷基三甲基溴化铵(CTAB)为模板剂,利用水热合成法制备了介孔氧化硅MCM-41,并采用TEM、XRD、N2吸附-脱附等测试手段对产物进行了表征。结果表明,合成的介孔材料为高质量的MCM-41。     

Nitridation of MgO-loaded MCM-41 and its beneficial applications in base-catalyzed reactions

Nitrogen-containing MgO-MCM-41 solid base material is prepared by nitridation of MgO-loaded mesoporous MCM-41. The ordered mesoporous structure and high surface area of MCM-41 are well preserved after MgO impregnation and nitridation, as proved by the XRD, TEM and nitrogen adsorption/desorption analysis. FTIR spectra the bridging -NH- groups and terminal -NH₂ groups are incorporated into the framework of MgO-MCM-41 by nitridation, and the base strength is expected to be enhanced due to the replacement of oxygen by nitrogen with lower electronegativity. FTIR spectra with the adsorption of different probe molecules, e.g. CO, CD₃CN and ¹³CO₂, are employed for the characterization of surface acidic-basic properties of MgO-MCM-41 before and after nitridation. It is revealed that the acidic hydroxyls in MgO-MCM-41 are greatly reduced through nitridation process. Compared with MgO-MCM-41, the nitridized MgO-MCM-41 material exhibits improved basic catalytic performances in Knoevenagel condensation reaction, Claisen-Schmidt reaction and dehydrogenation reaction of 2-propanol.     

Selective Synthesis of 1-butene through Positional Isomerisation of 2-butene over Mesoporous Silica MCM-41

A highly selective and active catalyst for the positional isomerisation of 2-butene into 1-butene has been developed by using a mesoporous silica, MCM-41. The yields of 1-butene as well as total conversion decrease when aluminium or lanthanum was added to the MCM-41 even though the amounts of acid sites increase. FT-IR spectra proved that the H site due to the silanol group may act as an active site for the positional isomerisation of 2-butene to 1-butene.     

低质量分数表面活性剂作模板合成MCM-41中孔分子筛

以硅酸钠为硅源,表面活性剂十六烷基三甲基溴化铵(CTMABr)为结构模板剂,用水热晶化法在w(CTMABr)=1%～3%下制备全硅MCM-41中孔分子筛。采用染料吸附脱色实验比较了原料配比、反应体系pH值、晶化时间、晶化温度、脱模温度对MCM-41合成的影响。结果表明,合成MCM-41中孔分子筛时表面活性剂CTMABr质量分数必须达到1%以上;pH=10～12;晶化温度以125℃左右为好;前驱体脱模温度控制在600～800℃。在较优的工艺条件w(CTMABr)=1 5%、pH=11、晶化温度125℃、晶化时间24h、脱模温度640℃下得到了具有完美晶型结构、BET比表面积=1370m2/g、平均孔径3 28nm的全硅MCM-41中孔分子筛。     

Mesoporous silica MCM-41 with rod-shaped morphology: Synthesis and characterization

A new synthesis route has been established to prepare highly pure mesoporous silica material (Si-MCM-41) with rod-like morphology. To improve the stability and to bring about the long range ordering in the mesoporous material, a series of tetra-alkylammonium salts has been employed in the new procedure in addition to the surfactant, cetyl-trimethylammonium bromide. The mesoporous silica materials have been characterized by small-angle X-ray diffraction (SAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ sorption and solid state ²⁹Si NMR measurements. The XRD study revealed that an excellent long range structural ordering of mesoporous material can be achieved using tetra-butylammonium bromide as a promoter. SEM study showed that rod-shaped single crystal like particles were formed in hydrothermal synthesis. TEM study revealed the presence of hexagonal voids on the face of the rod-shaped particles while nitrogen sorption study establishes the mesoporosity of the material. A high degree of cross-linking of -Si-O-Si- networks in the mesoporous silica has been evidenced in ²⁹Si NMR study.     

MCM-41介孔分子筛研究进展

介绍了介孔材料的定义,总结了MCM-41介孔分子筛的合成方法,针对其目前存在的孔径较小及酸性较小的缺点,综述了国内外对MCM-41介孔分子筛的孔径扩大分的最新研究进展。     

Immobilization of Uranyl Schiff Base in Mesoporous MCM-41

A uranyl Schiff base complex [UO₂{ OC₆H₄N = C(H)C₆H₄O} H₂O] has been immobilized inside the periodic mesopore channels of MCM-41 by the impregnation route. The samples have been characterized by XRD, N₂ adsorption/desorption, TG-DTA, DR UV-vis, ²⁹Si MAS NMR and FTIR techniques. While the host is found to retain its structural integrity, the surface area and the pore volume decrease considerably as a result of the intrapore confinement of complex molecules. The spectroscopy results indicate that the complex molecules are anchored with the silanol groups of MCM-41 via hydrogen bonding.     

MCM-41中孔分子筛的改性及其应用

综述了MCM—41中孔分子筛的合成方法,影响因素,重点介绍了儿种中孔分子筛改性方法,并强调了其有机改性。同时概述MCM—41在精细合成催化,分子吸附及分子组装方面的应用及发展状况,对其应用前景也作了相应分析。     

Mesoporous Silica Nanoparticles (MCM-41) Coated PEGylated Chitosan as a pH-Responsive Nanocarrier for Triggered Release of Erythromycin

A pH-responsive drug delivery system based on core shell structure of mesoporous silica nanoparticle (MSN) and chitosan-PEG copolymer was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM) techniques. In order to improve compatibility MSN and drug, mesoporous nanosilica was modified by 3-aminopropyl triethoxysilane. The release of erythromycin (a macrolide antibiotic) as a model drug was investigated in two pHs, 7.4 and 5.5.     

锆掺杂MCM-48氧化硅的合成及其表征

以正硅酸乙酯为硅源,丙醇锆为锆源,十六烷基三甲基溴化铵为模板剂,通过水热合成法制备Zr-MCM-48介孔材料,提高材料的耐碱性能.利用XRD、N2吸附-脱附、XPS等手段对产物进行了结构和性能的分析.XRD检测显示当Zr/Si物质的量比小于0.1时,可以获得长程有序的MCM-48结构.N2吸附-脱附实验、XPS测试等证实Zr已经掺入MCM-48骨架中.稳定性实验结果表明Zr/Si物质的量比为0.03时,Zr-MCM-48材料的耐碱性能明显增强,进一步表明Zr掺入了MCM-48材料的骨架中.