Effect of auxiliary chemicals on preparation of silica MCM-41

Silica MCM-41 materials were prepared hydrothermally by using 1,3,5-trimethylbenzene (MS) or 1,3,5-triisopropylbenzene (TI) as an auxiliary chemical. The BJH poressize of MCM-41 increased up to 12 nm with increasing amounts of MS. However, MCM-41 materials prepared with MS displayed irregular pore arrangements and a half of these materials exhibited low thermal and hydrothermal stabilities. On the other hand, MCM-41 materials prepared with TI as an auxiliary chemical displayed regular pore arrangements and high thermal and hydrothermal stabilities, but their BJH pore sizes did not go over 4.0 nm (intrinsic value; ca. 5 nm). MCM-41 prepared with TI together with a small amount of MS (TI/MS/SiO₂=1.5/0.5/1) displayed regular pore arrangements and high thermal and hydrothermal stabilities. Its BJH pore size was 4.7 nm (intrinsic value; ca. 6 nm).     

Surfactant effects on the physical properties of mesoporous silica and silicates

Mesostructured silicas and silicates have been synthesized using hydrogels with molar composition: M:26.0SiO₂:5.2(C₂H₅)₄NOH:7.5[CH₃(CH₂)₁₅N(CH₃)₃]₂O:790H₂O, where M=0, Zr(OC₃H₇)₄ or Ti(OC₄H₉)₄. In all preparations, colloidal silica (Ludox) was used as the source of silica. The hydrothermal transformation at 110°C of these gels produced solids with the hexagonal structure typical of MCM-41 type materials. The effects of chain length and surfactant terminal alkyl groups on the properties of mesoporous materials containing Ti or Zr, have been investigated by using different surfactants such as cetyl trimethyl ammonium bromide and chloride, cetyl dimethyl ethyl ammonium bromide, and myristyl trimethyl ammonium bromide. When the surfactant's carbonyl chain decreased to 14 from 16 carbon atoms, a reduction in unit cell dimension and average pore diameter was observed in the mesoporous silicas, titaniumsilicates and zirconiumsilicates under study. Replacement of methyl groups with ethyl groups on the surfactant hydrophobic head, had no measurable effects on crystals' properties. However, a surfactant with a bulky aromatic head group, such as cetyl pyridinium chloride, inhibited crystallization. In general, the use of bromide in place of chloride salts yielded more ordered MCM-41 type crystals. The high thermal stability (to 800°C), surface area (1000–1500 m²/g), pore volume (0.90–1.20 cm³/g) and uniform mesoporosity (with pore diameter in the 2.9 nm–3.6 nm range), of these metalsilicates could be of particular interest in the preparation of catalysts requiring siliceous metal supports.     

The Synthesis and Application of the Mesoporous Molecular Sieves MCM-41 — A Review

We report a “delayed neutralization” process for the preparation of highly-ordered aluminosilicate MCM-41 molecular sieves with high thermal and hydrothermal stability, and sharp pore size distribution. However, the structural order and pore size are dependent on the carbon chain length. In the mixture surfactant systems, the pore size of the MCM-41 materials could be fine-tuned. The pore size can be extended from 2.5 to 4.5 nm by adding a suitable amount of hydrocarbons. The tubular morphology of the MCM-41 material of 0.3 to 10 micrometers diameter, where the wall consists of coaxial cylindrical pores of nanometers MCM-41, can be obtained by careful control of the surfactant-water content and the rate of condensation of silica. An optimum condition for automatic synthesis of the hierarchical TWT structure has been accomplished. The addition of 1-alkanols as cosurfactant would not only improve the order of the MCM-41 hexagonal structure but also promote the formation of micrometer-sized hierarchical materials, for example: tubules-within-tubule and uniform-sized hollow spheres of diameter 5.0 ± 1.0 μm. However, the inside of the micron spheres has intricate structures possessing various topological genus ranks. The MCM-41 is a good supporter for Molybdenum oxide catalysts. The rate of deactivation in the catalytic reaction of ethyl-benzene dehydrogenation to styrene increases in the order: M_T < M_P < SiO₂. The physically mixed samples have higher catalytic activity than impregnated ones.     

Study of the Adsorption Properties of MCM-41 Molecular Sieves Prepared at Different Synthesis Times

The variation of surface properties of SiMCM-41 and AlMCM-41 nanoporous materials as function of synthesis time was examined. The main properties studied were: surface area, pore diameter, pore volume, mesoporous parameter, and wall thickness. Siliceous MCM-41 molecular sieves were synthesized starting from hydrogels with the following molar compositions: 4.58SiO₂:0.435Na₂O:1 CTMABr:200 H₂O for SiMCM-41, and 4.58SiO₂:0.485 Na₂O:1 CTMABr:0.038 Al₂O₃:200 H₂O, for AlMCM-41. Cetyltrimethylammonium bromide (CTMABr) was used as the structural template. The crystallographic parameters were obtained from XRD data and by nitrogen adsorption using the BET and BJH methods. The results obtained showed a significant variation of the surface properties of the MCM-41 materials as a function of the synthesis time reaching silica wall thickness of ca. 2 nm on the fourth day.     

水热法合成MCM-41分子筛时添加辅助烃的影响

０前言中孔ＭＣＭ－４１分子筛是Ｍｏｂｉｌ公司１９９２年开发的一种具有２－１０ｎｍ孔径的新型分子筛材料。由于其独特的孔径范围和表面特性,相关研究已经成为国际分子筛研究领域的热点课题,对它的合成、表征和催化作用已进行了许多研究［１～７］。Ｍｏｂｉｌ公司的...     

Phase behavior of binary system of bromobenzene–chlorobenzene confined in SBA-15 and MCM-41

Phase behavior of binary system of bromobenzene-chlorobenzene（C6H₅Br-C₆H₅Cl） confined in SBA-15 and MCM-41（pore diameter 8 nm,3.8 nm,respectively） has been investigated by means of differential scanning calorimetry（DSC）.Phase diagram of C₆H₅Br-C₆H₅Cl system confined in SBA-15 is a type of the complete miscible both in liquid and solid state,the same phase behavior as the bulk system.However,the phase diagram comprises only one boundary line,which is shifted down 22-36 K with respect to the bulk system.C₆H₅Br,C₆H₅Cl or the mixture within nanopores of MCM-41 is nonfreezing.The different phase behavior of the system confined in SBA-15 and MCM-41 is thought mainly due to the relative size of pore to molecule.     

MCM-41分子筛的合成及129Xe核磁共振的研究

Purely siliceous MCM-41 with a narrow pore-size distribution, different pore size, high surface area was synthesized . As prepared, calcined and catalytically tested MCM-41 materials have been comprehensively characterized by N₂ adsorption/desorption at 77K and ¹²⁹Xe NMR. By adding mesitylene during the synthesis, the pore size of MCM-41 was enlarged to 5.2nm. The chemical shift in ¹²⁹Xe NMR spectroscopy of adsorbed xenon indicates that the MCM-41 is one dimensional pore channels .     

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.     

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.     

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）。     

Syntheses of polycarbonate and polyurethane precursors utilizing CO2 over highly efficient, solid as-synthesized MCM-41 catalyst

As-synthesized MCM-41 was used as a reusable, heterogeneous catalyst for the eco-friendly synthesis of cyclic carbonate precursors of polycarbonates via a cycloaddition reaction of CO₂ with epoxides. This catalyst is also efficient for the synthesis of alkyl and aryl carbamate precursors of polyurethanes via the reaction of amines, CO₂ and alkyl halides. Both these reactions were carried out under mild conditions and without using any solvent or co-catalyst. CO₂ is utilized as a raw material replacement for toxic phosgene in the conventional synthesis of these chemicals.     

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。     

Influence of alkyl chain length of alpha olefin sulfonates on surface and interfacial properties

Alpha olefin sulfonates (AOS) with various alkyl chain lengths have been used to investigate the influence of alkyl chain length on the interfacial properties at air–water, liquid paraffin–water, and parafilm–water interfaces. It was found that the critical micelle concentration decreased with increasing alkyl chain length, while the efficiency of reducing surface tension was inverse relationship with alkyl chain length. The diffusion coefficient obviously reduced with an increase of surfactant concentration and alkyl chain length. The C_14-16AOS shows better wettability and emulsification than C_16-18AOS and C_20-24AOS. For foaming properties, the foamability and foam stability dramatically decreased with increasing alkyl chain length.     

中孔沸石新材料MCM－41──Ⅰ．合成、酸性及稳定性

中孔沸石新材料ＭＣＭ－４１──Ⅰ．合成、酸性及稳定性赵修松，王清遐，徐龙伢，谢紊娟（中国科学院大连化学物理研究所，大连１１６０２３）李新生（中国科学院大连化学物理研究所催化基础国家重点实验室，大连１１６０２３）关键词ＭＣＭ－４１沸石，合成，酸性，稳定...     

杂原子介孔Ce-MCM-41分子筛的制备及其吸附脱除甲硫醚性能

以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯(TEOS)为硅源,硝酸铈为铈源,采用水热法合成了杂原子介孔分子筛Ce-MCM-41。XRD和FT-IR表征结果表明,当加入的Ce/Si物质的量比小于0.04时合成了规整有序的介孔结构,并将Ce原子引入到MCM-41骨架中。N₂吸附-脱附测试获得MCM-41和Ce-MCM-41(Ce/Si物质的量比为0.04)的平均孔径分别为2.82和2.46 nm,孔容分别为0.762 1和 0.689 4 m³/g,BET比表面积分别为986.42和756.8 m²/g。NH₃-TPD表征结果表明,Ce-MCM-41的酸性要明显强于MCM-41,但两种分子筛的酸性均较弱。利用合成的MCM-41和Ce-MCM-41吸附脱除甲硫醚浓度为58 μg(甲硫醚)/g的甲硫醚/氮气混合气中的甲硫醚。甲硫醚分子尺寸的模拟结果为0.464 8 nm,可以很容易地进入分子筛的介孔孔道中。由于Ce-MCM-41分子筛具有较多的酸量,其硫吸附容量7.52 mg(S)/g明显高于MCM-41的4.57 mg(S)/g。MCM-41和Ce-MCM-41都具有较好的再生性能,再生3次后硫吸附容量仍可恢复到初始容量的80%,分别为3.52和 5.86 mg(S)/g。     

Effect of structural variation within cationic azo-surfactant upon photoresponsive function in aqueous solution

The cationic azo-surfactants possessing different spacers and tail alkyl chain lengths have been synthesized by azocoupling ofp-alkylaniline orop-ethoxyaniline with phenol, followed by alkylation and quaternalization with dibromoalkane and trimethylamine, respectively. These surfactants showed a good solubility in water. A reversibletrans-cis isomerization of the azosurfactants by photoirradiation was assessed by UV-Vis absorption spectra. Due to a difference in HLB between thetrans- andcis-surfactants, the observed critical micelle concentration (CMC) values and the electric conductivity of the surfactant solution at above the CMC were significantly affected by the photoinducedtrans-cis isomerization. The azo-surfactants bearing moderate alkyl chain lengths such as surfactants 6 (R₂=C₂H₄, R₃=C₄H₉) and 9 (R₂=C₄H₈, R₃=C₂H₅) were found to be effective to achieve large CMC changes (3.6 mmol/L for 6 and 5.9 mmol/L for 9) by UV-light irradiation. The replacement of the tail chain species also affected the photoresponsive function. The surfactant 12, possessingp-ethoxy group as the tail chain, was found to form a stable micelle aggregation as compared with the structurally related surfactant 10 having ethyl unit as its tail group, but it exhibited a large CMC change (5.3 mmol/L) by UV-light irradiation.     

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。     

The Synthesis and Characteristics of Vanadoaluminosilicate MCM-41 Mesoporous Molecular Sieves

A series of vanadoaluminosilicate MCM-41 mesoporous molecular sieves with various compositions have been hydrothermally synthesized. Hexadecyltrimethylammonium bromide was used as a surfactant in the synthesis. The samples were characterized with nitrogen sorption, X-ray diffraction, differential thermal analysis, thermogravimetric analysis, Fourier transform-Infrared spectroscopy, UV-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, and solid state NMR. The solid products had the MCM-41 structure and contained only atomically dispersed vanadium and aluminum consistent with framework vanadium and aluminum. The samples were hydrophobic and contained large amount of surfactant in the as-synthesized samples. The surfactant could be removed upon calcination at 450°C. N₂ sorption measurements and TEM demonstrate the high mesoporosity of [V, Al]-MCM-41. The incorporation of vanadium and aluminum into MCM-41 decreased the surface area to some extent. The morphologies of all the samples were the agglomerate of plates. ²⁹Si MAS NMR shows that the pore wall is amorphous. ²⁷Al MAS NMR shows that all of aluminum species were tetrahedrally coordinated even after calcination at 550°C.     

MCM-41-anchored sulfonic acid (MCM-41-SO3H): An efficient heterogeneous catalyst for green organic synthesis

MCM-41-anchored sulfonic acid (MCM-41-SO₃H) used as a solid acid catalyst has been reported in recent years for various synthetic protocols. The superior advantage of MCM-41-SO₃H is that it can be recovered and reused several times without loss of its efficiency. In this tutorial review, we attempt to give an overview of the use of MCM-41-SO₃H as a solid and heterogeneous catalyst in the synthesis of various organic compounds that have industrial and pharmaceutical applications.     

Synthesis of Amphoteric Surfactants via Esterification Process

This article describes the synthesis of a novel amphoteric surfactant through esterification of 2‐hydroxy‐N,N,N‐trimethylethanaminium chloride with maleic acid alkyl ester of C₈, C₁₀, and C₁₂ chain length in the presence of base. Maleic acid alkyl esters were synthesized by the reaction of maleic anhydride with alkyl alcohol. Surface‐active properties were studied by different techniques such as surface tension and foaming property. Critical micelle concentrations (CMCs) were found by using surface tension values to learn the effect of chain length on CMC of synthesized surfactants. The best result obtained has minimal coproducts, an environmentally safer route, and a very good CMC value of surfactants.