Structrue and Characteristics of Mesoporous Silica Synthesized in Acid Medium and Its Reaction Mechanism

Structrue and pore characteristics of the mesoporous silica synthesized in acid medium were studied by means of XRD, HRTEM, BET, FT-IR, DSC-TGA, and the reaction mechanism was also investigated deeply. The results show that mesopores in the sample possess hexagonal arrays obviously, whereas the structure of silica matrix is amorphous. The results also show that the acting mode of silica and CTMA^ inside the mesopores was chemical bonding force. The structure of rnesoporous silica was mainly dependent on the aggregational condition of micelle of CTMA^ as well as their liquid- crystallized status. In addition, condensation and dehydration of silicate radicals were accompanied in the process of calcination, which resulted in the mesoporous structure ordered in local range and the pore sizes largening.     

Synthesis and characterization of bimodal mesoporous silica

Mesoporous silica with controllable bimodal pore size distribution was synthesized with cetyltrimethylammonium bromide (CTAB) as chemical template for small mesopores and silica gel as physical template for large mesopores. The structure of synthesized samples were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ adsorption-desorption measurements. The experimental results show that bimodal mesoporous silica consists of small mesopores of about 3 nm and large mesopores of about 45 nm. The small mesopores which were formed on the external surface and pore walls of the silica gel had similar characters with those of MCM-41, while large mesopores were inherited from parent silica gel material. The pore size distribution of the synthesized silica can be adjusted by changing the relative content of TEOS and silica gel or the feeding sequence of silica gel and NH₄OH.     

Different Synthesis Methods for Ordered Mesoporous Silicas And Their Characteristics Comparison

1　IntroductionInorganicmesoporousmaterialshaveahighpotentialforapplicationsinthefieldsofcatalysis,adsorption ,sepa rationprocesses,biologymaterials,novelopticalmaterialsetc.Mesoporousmaterialshaverapidlyattractedresearchinterestsinthefieldofphysics,chemistryandmaterialssince 1 990s.Oneofthemostrepresentativemesoporousmaterialsismesoporoussilicapreparedbyusingalkylquaternaryammoniumcationicsurfactantsastemplate[1 3 ].Recently ,themesoporoussilicahasbecomeoneofthemostactivefieldsofhost guestass…     

Supramolecular-templated synthesis of mesoporous silica-zirconia nanocomposite

In the past few years, mesoporous oxide materialshave attracted much research attention by many re-search groups owing to their potential technological ap-plications[1 -4]. Many synthesis strategies have beendeveloped to synthesize mesoporous silica[1 -6]. Butthe application of such pure mesoporous materials tocertain heterogeneous catalytic reactions may be limitedbecause they are catalytically inactive with uniquestructural features. The general method of introducingcatalytically active site…     

Synthesis of mesoporous carbon as electrode material for supercapacitor by modified template method

The pore structures and electrochemical performances of mesoporous carbons prepared by silica sol template method as electrode material for supercapacitor were investigated. The mean pore size and mass specific capacitance of the mesoporous carbons increase with the increase of mass ratio of silica sol to carbon source （glucose）. A modified template method, combining silica sol template method and ZnCl2 chemical activation method, was proposed to improve the mass specific capacitance of the mesoporous carbon with an improved BET surface area. The correlation of rate capability and pore structure was studied by constant current discharge and electrochemical impedance spectroscopy. A commercially available microporous carbon was used for comparison. The result shows that mesoporous carbon with a larger pore size displays a higher rate capability. Mesoporous carbon synthesized by modified template method has both high mass specific capacitance and good rate capability.     

介孔氧化硅材料的合成及应用研究

采用十六烷基三甲基溴化铵（CTAB）为模板剂，通过加入不同量的1，3，5－三甲基苯（TMB）作为增大孔径的辅助剂合成出了不同孔径大小的氧化硅粉末，XRD、N2吸附曲线等测试手段表明所合成的材料为具有MCM－41结构特征的介孔材料；以该种材料制备了超微孔领域的多孔陶瓷，同时探讨了辅助剂对材料介孔结构和陶瓷气孔率的影响。结果表明，当辅助剂摩尔比小于x=0.4时，随着辅助剂加入量的增加，介孔材料的孔径、比表面积、结晶有序度等相应增加，但当加入量超过此范围时，结晶有序度反而下降，所获得的超微孔陶瓷其最大显气孔率可达56％。     

双孔硅胶整体材料的一步法合成及结构表征

采用溶胶-凝胶（sol-gel）技术,以嵌段共聚物Pluronic F127（EO106P070EO106）为模板剂,经一步法直接合成了具大孔和介孔结构的双孔硅胶整体材料,并通过SAXD、SEM、比表面积及孔径分析等手段对其结构进行了表征,结果表明所合成的硅胶整体材料具有大孔和介孔等级结构,且介孔具有一定程度的有序性。考察了反应条件对硅胶整体材料结构的影响,实现了对硅胶整体材料大孔结构、骨架结构及介孔结构的独立调控。该类型材料的高比表面积和双孔结构尺寸范围特别适用于作为一种新型的色谱分离材料。     

介孔氧化铟纳米粒子的制备及其气敏性质

以介孔氧化硅KIT-6为硬模板制备了介孔氧化铟纳米粒子,并对其进行了X射线粉末衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、氮气物理吸附分析。介孔氧化铟纳米粒子具有高的结晶度和有序介观结构,其尺寸为100 nm左右,比表面积为82 m2/g,孔径为4.5 nm左右,孔体积为0.42cm3/g。气敏性能测试结果表明介孔氧化铟纳米粒子对乙醇具有较好的敏感度,优于体相的氧化铟颗粒,在乙醇气体检测方面有潜在的应用。     

模板剂结构和合成温度对两步法制备介孔硅结构的影响

以F108和F127为模板剂,在不添加无机盐或辅助剂情况下,采用两步法在弱酸性体系中分别制备了具有Im3m结构的SBA．16及Fm3m结构的FDU-12硅基介孔材料．采用X射线衍射（XRD）、透射电子显微镜（TEM）及氮气吸附-脱附对其进行了表征,结果显示：在此条件下制备的两种不同结构的立方介孔硅均为典型的小孔（3．57～4．26nm）厚壁（9．68～9．81nm）型硅基介孔材料．结合制备过程中反应物组成及合成温度对形成小孔厚壁型介孔材料的过程进行了讨论．对体系合成温度变化的研究表明：温度的微小变化对最终产物有序性有着很大的影响,而最终产物的结构则是由所用的模板剂结构决定的．     

脂质分子通过自组装合成不同形貌的介孔材料

主要描述了通过氨基酸分子自组装来制备四种不同形貌的介孔硅材料,并通过常用的检测仪器：电子显微镜进行结构解析。已经发现：（1）通过改变反应温度从0,10,15到20℃,可以制备得到不同形貌的介孔材料,即类似于蛋白质分子的螺旋飘带,空心球,飞碟状和手性棒状形貌的二氧化硅介孔材料;（2）在螺旋飘带和空心球形貌材料中介孔孔道排列是无序的,而在飞碟和手性棒状材料中介孔孔道是高度有序排列的;（3）螺旋飘带形貌的材料是纯左手的,而手性棒状形貌的材料是右手过剩的介孔材料。该研究将为在分子水平合成手性材料提供一种新的方法。     

Low-cost preparation of mesoporous silica with high pore volume

Mesoporous silica materials with high pore volume were successfully prepared by the chemical precipitation method, with water glass and a biodegradable nonionic surfactant polyethylene glycol （PEG）. The obtained materials were characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, thermo gravimetric analyzer and differential scanning calorimetry （TG-DSC）, nitrogen adsorption-desorption measurements, and X-ray diffraction （XRD）. The results showed that the changes of the pore parameters depended on both the surfactant content and heat treatment temperature. When the content of PEG was 10wt% and the obtained PEG/SiO2 composite was heated at 600℃, the mesoporous silica with a pore volume of 2.2 cma/g, a BET specific surface area of 361.55 m^2/g, and a diameter of 2-4 μm could be obtained. The obtained mesoporous silica materials have potential applications in the fields of paint and plastic, as thickening, reinforcing, and flatting agents.     

A comparative study of drying techniques on the morphology of porous silica gels synthesized via sol-gel process

The effect of drying techniques on the microstructure,morphology and pore structure of porous silica gels was studied in the paper.The gels were prepared by using sol-gel process and different drying routes:freeze-drying (FD),low pressure drying (LPD),high temperature drying (HTD) and chemical modification & ambient drying (CMD) techniques.Observation under pore distribution and structural properties showed that CMD technique leads to homogenous mesoporous silica material with specific surface area of 745 m2/g,and the average pore size around 20 nm,while LPD and HTD result in loosely packed particles with non-isotropic aggregation pattern.The specific surface areas of LPD and HTD samples are 419 and 513 m2/g respectively,and the pore size distribution of the samples are observed distributing widely in range of 10-100 nm.Freeze drying method is a new but prospective way to prepare mesoporous silica.The specific area of FD sample is around 500 m2/g.By the comparison for the properties of the gels,this paper wants to induce a further interest in finding a proper method to synthesize the porous silica gels for low price use.     

Effects of Assistant Agent on Mesoporous Structure of Silica MCM-41 Molecular Sieves

The nanostrutured mesoporous silica materials MCM- 41 with different pore sizes were synthesized by adding 1,3,5-trimethylbenzene (TMB) as assistant agent in the reactant mixture. The obtained samples were investigated by XRD, HRTEM, FTIR and N2 adsorptions. It is shown that the pore sizes, ordered degree and specific surface area increase effectively with the incremented addition of TMB in an appropriate range, but the (100) peak intensity of XRD pattern becomes weakened and the ordered degree decreases when the additive quantity continued to increase. With the addition of TMB in an appropriate range, the effective surfactant ion pair packing parameter, g=V/ao l, is mediated in the range of 1/3- 1/2 with the increment of V and l, indicating that mesoporons silica is a well-ordered hexagonal structure. Howvever, when the addition of TMB increases, g value becomes larger, which leads to a less long-range ordered structure for the uneven condissolution of TMB.     

介孔碳片的合成及吸附脱硫性能

采用溶胶-凝胶法,以三嵌段共聚物聚氧化乙烯氧化丙烯氧化乙烯EO27- PO61-EO27 (P104)为模板剂,蔗糖为共模板,正硅酸乙酯(TEOS)为硅源,在强酸性及无机盐存在条件下制备出介孔硅片,并以此为硬模板,通过浓硫酸处理的方法成功制备了介孔碳片.并采用扫描电子显微镜、N2吸附-脱附实验对合成的介孔碳片进行了表征...     

Preparation and characterization of 3-dimensionally ordered macroporous SiC

Compared with the non-ordered macroporous materials, 3D long range ordered macroporous materials exhibit many advanced properties, such as the uniform pore size and the high permeability, etc. Nowadays, many kinds of 3D ordered macroporous (3DOM) materials, such as oxide ceramics[1―4], carbon[5] and polymers[6,7], have been successfully fabricated. However, the developed porous materials have some drawbacks that the porous carbon and polymer cannot be used in air at high temperatures, and o…     

掺杂金属介孔分子筛MCM-48的合成及储氢研究

以十六烷基三甲基溴化铵为模板剂,正硅酸四乙酯为硅源,在碱性条件下一步法水热晶化合成掺杂金属的介孔分子筛MCM-48。采用XRD、N2吸附脱附对产品进行结构表征,结果表明金属掺杂的介孔分子筛仍保持了三维立方介孔结构,但有序性略有降低,比表面积减小。对样品进行储氢性能研究发现,纯的MCM-48氢吸附量随温度的降低而增加,在0.2MPa、-25℃时氢吸附量达0.678 8%;金属掺杂介孔分子筛中,Ni、Fe、Pd有利于提高储氢量,Zr、Mg反而使氢吸附量减小,其中Ni-MCM-48在0.2MPa、-10℃时氢吸附量最高,达到0.772 0%。     

介孔分子筛Nb2O5/SBA-15催化合成油酸甲酯

以介孔分子筛SBA-15为载体,采用浸渍法合成了Nb2O5/SBA-15催化剂。通过XRD、BET等测试手段对样品进行了分析。结果表明,负载Nb2O5的SBA-15分子筛具有高度有序的二维六方介孔结构,并且具有较大的比表面积、孔容和孔径。Nb2O5/SBA-15分子筛催化剂的酯化反应最佳反应条件为：醇酸物质的量比为2∶1,反应温度160 ℃ ,反应时间4 h,催化剂用量为原料总质量的9.10%。Nb2O5/SBA-15催化剂具有较好的稳定使用性,是一种合成油酸甲酯的理想固体酸催化剂。     

One-pot Synthesis of Mesostruetured Ag/Siliea Composite Films

Mesoporous silica films embedded with Ag nanoparticles were directly synthesized by a solgel dip-coating process, combining alkyl （ethylene oxide） surfactant as temple and tetraethoxysilane as inorganic precursor. The addition of Ag^＋ ion to the reaction sol was prior to the formation of films, followed by the heat treatment at 150℃ led to the creation ofAg nanoparticies. The formation ofAg nanoparticles and the change of its surface plasma resonance absorption were characterized by Uv-vis. The small angle XRD test indicated that the films had an ordered hexagonal mesoporous structure, of which the unit cell parameter was about 4.26 nm. The TEM images and EDS spectra of the samples have directly verified the presence of mono-dispersed Ag nanoparticles within the films, due to the confine effects of mesopores.     

镧对WO3/ZrO2固体超强酸酸强度和结构的影响

通过共沉淀法制备了合适酸强度,比表面积为175.284 3 m2.g-1,最可几孔径在5.99 nm,负载镧的WO3/ZrO2固体超强酸催化剂。用Hammett指示剂法、XRD、N2等温吸附/脱附、DTA等方法考察了负载稀土镧后对催化剂的酸强度、比表面积、孔结构和热稳定性的影响。结果发现：La能均匀掺入WO3/ZrO2固体超强酸中,且适当加入稀土元素镧不但可以提高其酸强度,而且可以稳定结构、增加比表面积。     

氧化镧复合中孔氧化物的合成、表征及催化性能

以十二烷基硫酸钠（SDS）为模板剂,尿素和乙二胺为介质,当n（La）／n（SDS）／n（CO（NH2）2）／n（H2NCH2CH2NH2）／n（H2O）=1．0：1．0：0．6：1．0：200,反应温度为80℃、反应时间为4h时,用水热法合成了氧化镧／十二烷基硫酸钠复合中孔材料（LaOS）。通过XRD,IR,TG／DTA和N2吸附脱附等方法对样品的晶体结构和表面物性进行了研究。结果表明,合成的氧化镧／十二烷基硫酸钠复合物具有典型的六方中孔结构特征,比表面积为182m^2／g,平均孔径为2．6nm。将氧化镧／十二炕基硫酸钠复合物用于催化正辛醇乙氧基化反应,当LaOS的质量分数为10％,反应温度为120℃,初始反应压力0．5MPa时,环氧乙烷的平均反应速率为3．7mol／（mol·h）。产物正辛醇聚氧乙烯醚相对分子质量分布较窄。