模板剂对全硅MCM-41介孔分子筛结构的影响

分别采用十六烷基三甲基溴化铵和十六烷基三乙基溴化铵作为模板剂,硅溶胶为硅源,用水热晶化法在碱性（NaOH）介质中合成了MCM-41介孔分子筛样品.通过XRD、N2吸附-脱附、TG-DTA、IR等测试手段对这两种样品进行了对比表征分析.考察了两种不同模板剂对其晶体结构、比表面及孔径大小的影响.实验结果表明,相对于十六烷基三甲基溴化铵做模板剂,采用大头基的十六烷基三乙基溴化铵可以合成较大孔径和孔容（分别为4.72 nm和1.14 cm3•g-1）的MCM-41介孔分子筛,而且具有较窄的孔径分布,因此对于合成大孔径的介孔分子筛MCM-41,十六烷基三乙基溴化铵是一种很好的模板剂.     

非水介质中合成介孔分子筛MCM-41

首次采用十六烷基三甲基溴化铵为模板剂、正硅酸乙酯为硅源, 分别使用无机和有机弱碱, 溶剂热晶化法在非水甘油介质中合成了介孔分子筛MCM-41, 通过XRD, N₂吸附-脱附, TG-DTG, IR, SEM等测试手段对样品进行了表征分析, 结果表明在甘油体系中得到的样品具有优良的孔结构性质. 相比于氢氧化钠, 以有机弱碱(无水乙二胺、三乙胺)作为碱源, 可以得到有序性更好、结晶度高的样品, 样品具有较窄的孔径分布.     

辅助有机胺对介孔分子筛MCM-41合成及其性质的影响

采用阳离子表面活性剂十六烷基三甲基溴化铵为模板剂、硫酸铝为铝源、硅溶胶为硅源，分别使用中等链长的有机胺和正己烷作为辅助添加剂，用水热晶化法在碱性介质中合成了介孔分子筛MCM-41，通过XRD、N2吸附-脱附、SEM测试手段对得到的样品进行了对比表征分析。实验结果表明，除三乙胺外，向反应体系中加入适量的三正丙胺、三正丁基胺、三正辛胺和二异丁胺后，均能够使介孔 MCM-41的d100值和孔径增大，且具有较大的BET表面积（>1 000 m2/g）和孔容（>1 cm3/g）；加入正己烷后，也可以使得MCM-41孔径变大，但是和加入有机胺相比较，合成的样品具有较小的BET表面积（887.3 m2/g）和孔容（0.81 cm3/g）。     

Sorption on as-synthesized MCM-41

Mesoporous materials MCM-41 with the hexagonal arrangement of pores were obtained using dodecyltrimethylammonium bromide and octadecyltrimethylammonium bromide as templating surfactants. Adsorption of toluene and propan-1-ol on the as-synthesized MCM-41 silica samples was investigated using the TG-DTG, DTA and DSC techniques. The sorption mechanism of used adsorptives is discussed in terms of hydrophobicity of pore interior filled with template as well as pore dimensions.     

以混合表面活性剂为模板可控合成MCM-48和MCM-41分子筛

利用阳离子和三嵌段共聚物混合表面活性剂为模板,在水热条件、碱性介质中可控合成出MCM-48和MCM-41分子筛。在固定P123(聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物):TEOS(正硅酸乙酯)(物质的量的比)为0.01875的体系中,调节CTAB(十六烷基三甲基溴化铵)∶TEOS(正硅酸乙酯)物质的量比值m,当m在0.12~0.13范围合成出MCM-48分子筛;当m在0.04~0.08范围合成出MCM-41分子筛。通过XRD,TEM,N2物理吸附,IR等方法进行了表征。结果表明:聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物(P123)的加入可以更大程度地降低合成介孔材料所需阳离子表面活性剂的用量;可控合成的介孔材料具有高比表面积、高度有序的孔道结构、较集中的孔径分布。     

A Novel Method for the Synthesis of Mesoporous Molecular Sieve MCM-41

Using glycerol, glycol and water as solvent, cetyltrimethylammonium bromide (CTAB) as template, tetraethyl orthosilicate (TEOS) as silica source, ethylenediamine (EDA) as base source, mesoporous molecular sieve MCM-41 has been synthesized at room temperature, characterized by X-ray power diffraction and N2 adsorption. Compared with the samples synthesized by glycol and water, the samples synthesized by glycerol have larger pore diameter and high surface areas. Thus glycerol is an efficient solvent for preparing larger pore mesoporous MCM-41.     

MCM-41介孔材料负载金属的一步法合成及其对酯化反应的催化作用

以增溶了茂金属的十六烷基三甲基溴化铵(CTAB)胶束为模板, 采用一步法合成了介孔表面负载有金属(铁、钛和锆)的介孔材料MCM-41, 通过等离子体电感耦合发射光谱仪(ICP-AES)测定铁、钛和锆负载量(质量分数)分别为1.71%、0.95%和0.81%. 通过X射线衍射(XRD)图谱和N₂吸脱附等温线可知, 负载金属的介孔材料M-MCM-41(T) 仍具有较高的比表面以及规整的六方有序孔道结构, 去除模板剂的焙烧温度对孔道结构有一定影响. 由一步法合成的金属负载介孔材料对乙酸正丁酯的酯化反应具有很高的催化活性, 其中Fe-MCM-41在单位时间单位金属催化生成的产物量(TOF)为55643 g·h^-1·g^-1, 而Zr-MCM-41的TOF高达125320 g·h^-1·g^-1. 与纯茂金属相比, 由茂金属合成的金属负载介孔材料可显著提高酯化反应的催化活性.     

One pot synthesis of ordered mesoporous organosilica particles bearing propyl-, octyl- and hexadecyl-chains

New hybrid organic–inorganic materials exhibiting ordered mesoporous structures have been synthesized by co-condensation of tetraethoxysilane and various alkyltrimethoxysilanes with increasing length of the hydrocarbon chain (propyl, octyl, hexadecyl), in water–ethanol solution containing ammonia, in the presence of a cationic surfactant (cetyltrimethylammonium bromide) as templating agent. The obtained hybrid materials were characterized by using several physico-chemical techniques, such as X-ray diffraction, N₂ adsorption, ²⁹Si MAS NMR, SEM and elemental analysis. It was shown that the direct synthesis procedure allows obtaining ordered hybrid mesoporous silica with various contents of organic functions, from 5 to 20 %. Moreover, increasing the chain length of the organic group, from propyl to octyl and hexadecyl leads to a change of the pore structure from hexagonal p6mm MCM-41 type architecture to cubic Ia3d MCM-48 type mesostructure.     

Three-dimensional mesoporous gallosilicate with Pm3n symmetry and its unusual catalytic performances

Three-dimensional, mesoporous-cage-type, GaSBA-1 materials with different n(Si)/n(Ga) ratios have been successfully prepared for the first time by using a low hydrochloric acid to silicon (n(HCl)/n(Si)) molar ratio in the synthesis gel by templating with cetyltriethylammonium bromide as the structure-directing agent in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques including X-ray diffraction (XRD), N(2) adsorption, high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, energy dispersive spectroscopy, elemental mapping, and (29)Si magic-angle-spinning NMR spectroscopy. XRD and nitrogen adsorption results reveal that the structures of the GaSBA-1 materials resemble that of SBA-1, which possesses a cubic, three-dimensional, cage-type structure with open windows. In addition, the specific surface area and the specific pore volume of the GaSBA-1 materials are much higher than those of the SBA-1 silica, which are very important for the catalytic applications. The amount of Ga cation in the SBA-1 silica framework has been found to play a critical role in controlling the morphology and the pore diameter of the materials. Finally, the catalytic activity in the tert-butylation of phenol with tert-butanol as the alkylating agent has been investigated and the results are compared with those of other mesoporous catalysts such as AlMCM-41, FeMCM-41, FeAl-MCM-41, and FeSBA-1. Moreover, the effect of various reaction parameters such as the reaction temperature, reactant feed ratio, and time-on-stream on the phenol conversion in the tert-butylation of phenol over GaSBA-1 catalysts has been demonstrated. Among the catalysts examined, GaSBA-1(17), in which the number in the parenthesis denotes the n(Si)/n(Ga) ratio, showed remarkable activity with a high conversion of phenol and selectivity to 4-tert-butylphenol; it was found to be superior over other mesoporous catalysts used in the study.     

CMC和CTAB双模板法合成具有稳定结构的MCM-41中孔分子筛

以羧甲基纤维素和十六烷基三甲基溴化铵为双模板,制备出了具有更高稳定性并且具有高度有序二维六方结构的MCM-41介孔分子筛.透射电镜和X射线衍射结果表明,以双模板制备的MCM-41介孔分子筛具有高度有序的二维六方(p6mm)孔道结构.此外,以双模板制备的MCM-41介孔分子筛焙烧前后的X射线衍射结果表明,在焙烧过程中其晶胞收缩比例为3.1%.与以纯表面活性剂为模版制备的MCM-41介孔分子筛(晶胞收缩比例为9.7%)相比,双模板制备的MCM-41介孔分子筛具有更高的稳定性能. MCM-41介孔分子筛稳定性能的提高可能是由于在硅物种、表面活性剂以及羧甲基纤维素在自组装过程中,羧甲基纤维素表面丰富的羟基与硅物种Si-(OH)x的相互作用促进了Si-(OH)x的缩聚.     

氮气在MCM－41分子筛中的吸附：实验和分子模拟

用美国Micromeritics公司生产的ASAP2010物理吸附仪测定了低温（77 K） N_2在MCM-41分子筛中的吸附等温线，获得了表征MCM-41特征的BET比表面、BJH孔 容和平均孔径。同时用巨正则Monte Carlo（GCMC）模拟方法考究了N_2在MCM-41中 的吸附，得到了N_2在MCM-41中的模拟吸附等温线，分析了流体在MCM-41分子筛中 的微观结构。GCMC模拟中MCM-41介孔材料模型化为圆柱孔，N_2模型化为Lennard- Jones（LJ）球。N_2和MCM-41介孔墙壁间的相互作用采用Tjatjopoulos-Feke- Mann（TFM）势能模型进行表征。通过使模拟和实验结果有一个好的吻合，确定了 一组有效的MCM-41分子筛的势能参数（σ_(ww) = 0.265 nm，∈_(ww)/k = 190 K ）。这为以后其他吸附质在MCM-41中吸附的预测奠定了基础、提供了依据。     

MCM-41分子筛合成与模版剂回收新方法

研究了以溴代十六烷基吡啶（CPBr）为模板剂,正硅酸乙酯（TEOS）为硅源,在强酸性介质中形成MCM-41介孔分子筛六方晶相的过程中,HCI／TEOS对分子筛结构的影响．发现随HCI／TEOS提高,分子筛结晶度、晶胞参数、孔道壁厚明显增加,孔径呈减少趋势．同时还发现包结于分子筛孔道中的CPBr100％可以通过丙团／水混合溶剂萃取回收．据此,本文对MCM-41分子筛的“S X-I ”超分子组装机理及分子筛孔道内模板剂的存在状态进行了进一步探讨．     

Hydrogen bonding of water confined in mesoporous silica MCM-41 and SBA-15 studied by 1H solid-state NMR

The adsorption of water in two mesoporous silica materials with cylindrical pores of uniform diameter, MCM-41 and SBA-15, was studied by 1H MAS (MAS=magic angle spinning) and static solid-state NMR spectroscopy. All observed hydrogen atoms are either surface -SiOH groups or hydrogen-bonded water molecules. Unlike MCM-41, some strongly bound water molecules exist at the inner surfaces of SBA-15 that are assigned to surface defects. At higher filling levels, a further difference between MCM-41 and SBA-15 is observed. Water molecules in MCM-41 exhibit a bimodal line distribution of chemical shifts, with one peak at the position of inner-bulk water, and the second peak at the position of water molecules in fast exchange with surface -SiOH groups. In SBA-15, a single line is observed that shifts continuously as the pore filling is increased. This result is attributed to a different pore-filling mechanism for the two silica materials. In MCM-41, due to its small pore diameter (3.3 nm), pore filling by pore condensation (axial-pore-filling mode) occurs at a low relative pressure, corresponding roughly to a single adsorbed monolayer. For SBA-15, owing to its larger pore diameter (8 nm), a gradual increase in the thickness of the adsorbed layer (radial-pore-filling mode) prevails until pore condensation takes place at a higher level of pore filling.     

Pore curvature effect on the stability of Co-MCM-41 and the formation of size-controllable subnanometer Co clusters

Samples of Co-MCM-41 with different pore diameters have been synthesized using organic templates with different alkyl chain lengths. The reducibility of cobalt in these highly stable samples was investigated by TPR and X-ray absorption spectroscopy. We have found that the reducibility correlates strongly with the pore diameter of the MCM-41, with the cobalt incorporated in the smaller pore MCM-41 being more resistant to complete reduction. It is proposed that the distribution of cobalt ions in the pore wall is affected by both the preparation procedure and the pore diameter. The size of the metallic Co clusters formed after different reducing treatments correlates linearly with the pore size, giving direct evidence for the effect of the radius of curvature on reducibility. Complete cobalt reduction after TPR causes an inverse variation of the cluster size with the pore size, resulting from differences in the density of Co clusters and from differences in the rate of Co migration and aggregation outside the pores of MCM-41 with different pore sizes.     

A study of freezing-melting hysteresis of water in different porous materials. Part II: surfactant-templated silicas

The freezing-melting hysteresis of water in mesoporous silicas MCM-48, MCM-41 and SBA-16 has been studied by NMR cryoporometry. The hysteresis in MCM-48 was found to exhibit nearly parallel branches, matching type H1 hysteresis that had been observed earlier in controlled pore glass. The same type of hysteresis is observed in two of three different-sized MCM-41 under study (a pore diameter of 3.6 and 3 nm), superimposed with a secondary, extremely broad, type H3 hysteresis. No hysteresis was found in the smallest MCM-41 with a pore diameter < 3 nm. Finally, water in SBA-16 exhibits type H2 hysteresis with the freezing branch being essentially steeper than the melting one, which is attributed to a pore blockage upon freezing, similar to what we observed earlier in Vycor porous glass. The data were analyzed using the model of curvature-dependent metastability of a solid phase upon melting; the validity of this model has been discussed.     

中孔硅酸盐材料MCM-41的合成与表征研究(英文)

以十六烷基三甲基溴化铵为模板剂,硅酸钠为硅源,铝酸钠为铝源,在水热条件下成功地合成出了ＭＣＭ－４１中孔硅酸盐材料。采用ＸＲＤ、低温Ｎ２吸附脱附等测试手段对合成的ＭＣＭ－４１样品进行了表征。通过优化合成条件,合成出孔径３.２ ｎｍ、比表面９０４ｍ２／ｇ和孔壁厚约１.４６ ｎｍ的ＭＣＭ－４１分子筛。催化活性测定采用微反应活性实验来评价其活性和选择性。     

以CTMABr和CTMAOH为共模板剂合成MCM-41

采用共模板剂水热合成了MCM-41.分别用X射线粉末衍射(XRD)、固体核磁共振(²⁷AlMASNMR)和N₂吸附等温线技术考察了用该方法和传统方法所制备的Si-MCM-41和Al-MCM-41样品的晶相结构、孔结构以及Al在分子筛中的化学环境.结果表明,用共模板剂方法合成的MCM-41样品,其纯度和孔径均一性显著提高,特别是当样品中Al含量较高时,仍可保证Al原子以四配位结合在MCM-41的硅骨架上.还就采用共模板剂的理论依据进行了讨论.     

以离子液体为模板剂合成MCM-41的研究——不同扩孔剂对介孔分子筛MCM-41孔径结构的影响

以离子液体为模板剂, 正硅酸乙酯为硅源, 研究了扩孔剂三甲苯, 癸烷, 以及三甲苯与癸烷1∶1的混合物对介孔分子筛MCM-41结构的影响, 采用XRD以及氮吸附-脱附分析技术对合成的介孔分子筛MCM-41进行了表征.结果表明: 三种扩孔剂中以三甲苯与癸烷1∶1的混合物效果最优, MCM-41的孔径可达到4.5 nm, 并且可以提高介孔分子筛的比表面积与结晶度.扩孔剂的最佳添加量为: 扩孔剂与模板剂之比等于1.0;最佳晶化温度120 ℃.     

Remarkable effect of pore size on the catalytic activity of mesoporous silica for the acetalization of cyclohexanone with methanol

The catalytic activity of mesoporous silica (MCM-41) for the acetalization of cyclohexanone shows a volcano-shaped dependence on the pore diameter. The diameter of the cyclohexanone molecule is ca. 0.75 nm, while its acetalization with methanol was well accelerated on MCM-41 with a pore diameter of approximately 1.9 nm, and smaller or larger pores were not suitable for the catalysis. The catalytic activity was independent of the Al concentration.     

New Routes to the Synthesis of Mesoporous Materials and Their Properties

The factors that influence the hydrothermal synthesis of MCM-41 were investigated, and it was found that compared with those from high H₂O/SiO₂ systems(designated MCM-41-A), the products from low H₂O/SiO₂ systems(designated MCM-41-B) exhibited a less-defined X-ray powder diffraction (XRD) pattern with a broader main reflection peak at a lower 2θ diffraction angle. MCM-41-B possesses a smaller surface area but a larger pore size than MCM-41-A. New routes including direct thermal treatment, room-temperature crystallization and microwave heating were developed for the formation of MCM-41, and the properties of the products prepared from these new routes were compared with those of the MCM-41 hydrothermally synthesized. The pore sizes of MCM-41 materials are uniformly distributed with an effective pore diameter that falls into the range of 2-4 nm, where as the products from wet-gel thermal treatment possess two kinds of mesopores:the well-defined smaller pores distributed at 3 nm and the larger one within 8-20 nm. The MAS NMR spectroscopy revealed that after calcination to remove the organic template in Al-containing MCM-41, a small part of the tetrahedrally-coordinated framework aluminum atoms became octahedrally-coordinated and a considerable amount of Si-OH species were generated.