Synthesis and characterization of mesoporous molecular sieves

In the synthesis of mesoporous molecular sieves of the type MCM-41, different cationactive surfactants and sources of silicon were used. Moreover, Al-MCM-41 samples with different content of aluminium were synthesized. MCM-41 and Al-MCM-41 were synthesized at elevated temperature in stainless-steel autoclaves. Prepared mesoporous molecular sieves were characterized by powder X-ray diffraction (XRD), physical adsorption of nitrogen at the temperature of −197°C, sorption capacity of benzene, and by infrared spectroscopy (FTIR). Acidity was measured for Al-MCM-41 by temperature programmed desorption of ammonia (TPDA) and by FTIR of adsorbed pyridine. Acid catalytic activity of Al-MCM-41 was tested by isomerization of o-xylene. Influence of the synthesis reproducibility, surfactant used, source of silicon, synthesis time, source of aluminium, and Si to Al mole ratio on the properties of mesoporous molecular sieves were evaluated.     

外围为柔性链状取代基团Ni-酞菁配合物的合成及其在MCM-41中的装载

合成了外围具有柔性链状基团的2（3）,9（10）,16（17）,23（24）-四-（N,N-二乙胺基乙氧基）Ni-酞菁配合物（2）．以正硅酸乙酯为硅源,十六烷基三甲基溴化铵为模板剂,水热法将该Ni-酞菁配合物（2）装载到MCM-41中．利用UV-Vis-NIR,FT-IR,XRD,TEM,FESEM及N2吸附-脱附等温线对制备的样品进行了表征．研究表明制备的样品中Ni-酞菁配合物（2）主要以单体和二聚体的形式存在于MCM-41中．通过不同制备酞菁浓度的装载研究表明,较高制备酞菁浓度有利于制备结晶度及孔道有序性较高的介孔分子筛样品．     

ZSM-5/MCM-41复合分子筛的合成与表征

以碱处理的ZSM-5浆液为硅铝源,通过水热自组装过程合成了介孔-微孔复合孔道结构的分子筛,并采用XRD、BET、HRTEM、Py-IR和水热处理等手段对合成分子筛进行了表征。结果表明,碱处理ZSM-5时的苛刻程度是影响复合分子筛合成的重要因素,适宜的碱处理条件为NaOH浓度1 mol/L、80℃时处理1 h。表征结果表明,复合分子筛具有规整互通的微孔-介孔梯级复合孔道结构,孔容、比表面积和平均孔径分别为0.63 mL/g,684 m²/g和3.76 nm,属典型的MCM-41结构;与MCM-41相比,复合分子筛的B酸(尤其是强B酸)酸量明显增强,水热稳定性显著提高。     

Synthesis of binaphthols over mesoporous molecular sieves

Mesoporous aluminosilicates (Al-containing NaMCM-41) were applied as catalyst supports for oxidative coupling of β-naphthol and substituted β-naphthols due to their remarkable features such as surface area, ordered mesopores and high thermal stability. The NaMCM-41 supported copper catalysts prepared by impregnation method, and Cu-NaMCM-41 was prepared by incorporating copper during synthesis. Oxidative coupling of β-naphthol reaction was studied using molecular oxygen as oxidant. The copper supported NaMCM-41 catalysts were prepared with different Si/Al ratios and calcined from 120 to 420 °C were observed to show varied product selectivity. The NaMCM-41 supported copper catalysts and Cu-NaMCM-41 were more active than the corresponding Cu/Fe supported on NaY zeolite. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), UV–DRS, ICPMS and BET surface area techniques and the reaction products were confirmed by ¹H-NMR, FTIR and HRMS. An attempt has been made to explain the product selectivity of the catalysts discussed with the above techniques. The high dispersion of Cu⁺² species observed in the catalysts having high Si/Al ratios in NaMCM-41 support and catalysts that are calcined at low temperatures, i.e. less than 420 °C, yielded an unexpected product perylene diol. A comparatively low dispersion of Cu⁺² species, noticed in catalysts having low Si/Al ratios and calcined at high temperatures, yielded binapthol as the coupled product. The effect of the variation of catalyst and the solvent are also studied.     

Al-MCM-41介孔分子筛催化对甲酚叔丁基化反应的研究

2-叔丁基对甲酚是一种有机中间体,在有机合成领域中占有重要地位,被广泛应用于表面活性剂、高档酚类抗氧化剂2246和2246-S、紫外线吸收剂UV-326等的生产[1]。特别是近十年来,以抗热老化为特征的功能性高档酚类抗氧化剂在国内外相继问世,它们对于提高聚合物材料的成型加工性能、     

以伯胺为模板剂合成含铁介孔分子筛FeHMS

以非离子型表面活性剂伯胺为模板剂合成了含铁介孔分子筛FeHMS,并对其结构和形态进行了表征。发现FeHMS的颗粒比SiHMS小,粒子表面更为光滑。除了2.5nm的介孔外,FeHMS还原10nm左右的孔。FeHMS介孔分子筛在脱除模板剂之前,铁主要处于四面体配位状态的骨架位,经焙烧脱除模板剂之后,部分铁由骨架位迁移到孔壁表面。用酸化的乙醇溶液抽提脱除模板剂,能更有效地让铁保留在四面体配位状态的骨架位上。高温脱除模板剂后,孔壁表面的铁物种处于一种高分散的状态。此外还研究了HMS类介孔分子筛材料的水热稳定性,发现铁的引入可改善介孔分子筛材料的水热稳定性。     

Anchoring of 1,8-naphthalimide derivative into mesoporous MCM-41 molecular sieves

The fluorescent dye molecules, 4-piperidine-1,8-naphthalimide, were successfully fixed into the amino modified pore channel of mesoporous MCM-41 type materials by in situ reaction of 4-piperidinyl-1,8-naphthalic anhydride with the amino group. The formation of amide bonds on the pore surface was verified by infrared spectra. The maximum fluorescence emission peak of this hybrid material has a red shift of 13 nm compared to that of a naphthalimide derivative in ethanol solution. Moreover, the fluorescence intensity of dye molecules grafted into Ce-doped MCM-41 is higher than that in pure silica MCM-41. This phenomenon is attributed to the inhibited internal electron transfer from piperidine to naphthalimide groups by Ce⁴⁺, thus improving the fluorescence intensity of the naphthalimide group. The unique fluorescence behavior of the 1,8-naphthalimide derivative doped hybrid mesoporous material makes it a good candidate for the metal ions microdetection.     

NbMCM-41 mesoporous molecular sieves in oxidative dehydrogenation of ethane and propane

It has been evidenced that the dissolution of niobium in silica mesoporous matrix significantly increases the catalytic effectiveness in the oxidative dehydrogenation of alkanes as compared with unsupported Nb₂O₅. This revised version was published online in June 2006 with corrections to the Cover Date.     

Zr-MCM-41的合成及其表征

以Zr(NO3)4·3H2O为锆源，通过直接合成法得到了Zr-MCM-41介孔材料，考察了不同Zr/Si摩尔比对样品的影响，其中Zr/Si的摩尔比最大为0.25。随着Zr/Si的摩尔比的增加，2θ=2°附近的100晶面的衍射峰强度逐渐降低，当Zr/Si摩尔比大于0.25后得不到介孔Zr-MCM-41材料。对所得样品采用XRD、TG-DTA、N2吸附 脱附几种分析方法进行了表征。     

Characteristics of molecular sorption on template containing mesoporous molecular sieves of type MCM-41

Template containing materials of type MCM-41 have properties of microporous substances. On absorption into the micropores of such materials the dependence of the characteristic absorption energies on the molecular mass of the sorptive is extreme, and the specific absorption volume decreases with increased molar volume of the sorptive. A model is proposed to explain the peculiarities of the absorption properties of the template containing materials. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 6, 367–372, November–December, 1999.     

Effect of rehydration on the porosity of MCM-41 mesoporous molecular sieves

In distinction from aluminosilicates, the porosity of the detemplated silicous MCM-41 is significantly reduced after several cycles of dehydration-rehydration. The stability of Si-MCM-41 is not changed by absorption-desorption of nonpolar hexane. An explanation is proposed for the effect of rehydration on the porosity of MCM-41. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 50–55, January–February, 1999.     

Synthesis and characterization of highly ordered mesoporous thin films with -COOH terminated pore surfaces

Highly ordered mesoporous inorganic-organic hybrid thin films with covalently bonded carboxylic acid (-COOH) terminal groups on the pore surfaces were synthesized by evaporation induced self-assembly of tetraethoxysilane, organosilanes, and a nonionic surfactant followed by acid hydrolysis and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, surface acoustic wave (SAW) based N2 sorption, and thermogravimetric analysis (TGA) techniques.     

Effect of titanium on the structure and properties of mesoporous MCM-41 molecular sieves

Mesoporous MSM-41 titanium silicate molecular sieves with high titanium content were synthesized. The hexagonal structure along with high specific surface and pore volume are retained up to Si/Ti≥5. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 177–182, May–June, 1999.     

介孔分子筛研究新进展

介孔分子筛材料作为催化剂或催化剂载体为有机大分子参与反应提供了有利的空间构型和择形活性中心,在石油加工工业中具有潜在的应用优势。但由于介孔分子筛材料的水热稳定性比较低,且酸性较弱,极大地影响了其在催化领域中的广泛应用。本文综述了近年硅基介孔分子筛的改性研究进展,重点讨论了在提高介孔分子筛酸性和水热稳定性方面的研究工作。     

Titanium-containing silica mesoporous molecular sieves

An analysis was made of the conditions for the synthesis of titanium-containing mesoporous silica molecular sieves and their effect on the stereochemical structure, the coordination of the titanium, and the catalytic characteristics. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 3, pp. 135–158, May–June, 2000.     

Liquid-phase synthesis of isopulegol from citronellal using mesoporous molecular sieves mcm-41 and zeolites

Isopulegol (IPG) was synthesized from citronellal (CTN) at atmospheric pressure and 40~60°C in a batch reactor by using mesoporous molecular sieves MCM-41 as well as zeolites HZSM-5 and Hβ. The catalysts were characterized by the methods of XRD, N₂ adsorption, ²⁷Al and ²⁹Si MAS-NMR and TPD of ammonia. Under our reaction conditions, Al-MCM-41 was found to be the best catalyst; it exhibited much higher activity, despite slightly lower IPG selectivity. The catalytic results depend on a variety of factors, viz. the acidity, the pore size and the pore channel of catalysts. The reaction paths were proposed and the kinetic parameters for competitive first order reactions of CTN were estimated. This revised version was published online in June 2006 with corrections to the Cover Date.     

Characterization of CoMCM-41 mesoporous molecular sieves obtained by the microwave irradiation method

CoMCM-41 mesoporous molecular sieves with different amounts of cobalt were synthesized via the microwave irradiation method. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), temperature programmed reduction (TPR), transmission electron microscopy (TEM) and N₂ adsorption-desorption technique, and thermal and hydrothermal stabilities of synthesized CoMCM-41 samples were also investigated. Results show that these synthesized materials have typical mesoporous structure of MCM-41. Also, specific surface area and pore volume of synthesized CoMCM-41 decrease with increasing amount of cobalt added, and mesoporous ordering also decreases. When the molar ratio of SiO₂:CoO in the starting material is 1.0:0.05, mesoporous ordering of synthesized CoMCM-41 is the best among the four doping contents. On the other hand, results of thermal and hydrothermal tests show that CoMCM-41 after calcination at 750 °C for 3 h or hydrothermal treatment at 100 °C for 5 days still retains mesostructure. However, mesoporous framework is entirely damaged after calcination at 850 °C for 3 h.     

Synthesis of highly dispersed ceria-zirconia supported on ordered mesoporous alumina

Highly dispersed ceria-zirconia supported on ordered mesoporous alumina, showing higher thermal stability up to 900 °C, has been successfully synthesized via a sol-gel process associated with P123 as the template in ethanol solvent.     

Textural and structural properties and surface acidity characterization of mesoporous silica-zirconia molecular sieves

Homogeneous mesoporous zirconium-containing MCM-41 type silica were prepared by supramolecular templating and their textural and structural properties were studied using powder X-ray diffraction, N₂ porosimetry, atomic force microscopy, EXAFS, XPS, and UV-VIS-NIR diffuse reflectance spectroscopy. Their acid properties were also studied by using IR spectroscopy and by the use of catalytic tests such as the decomposition of isopropanol and the isomerization of 1-butene. The materials prepared show a good degree of crystallinity with a regular ordering of the pores into a hexagonal arrangement and high thermal stability. The specific surface area of the prepared materials decreases as the zirconium content rises. Zirconium atoms are in coordination 7 to 8 and located at the surface of the pores such that a high proportion of the oxygen atoms bonded to zirconium corresponds to surface non-condensed oxygen atoms. Both facts are responsible for the acid properties of the solids that show weak Brønsted and medium strong Lewis acidity.     

Chiral ruthenium porphyrin encapsulated in ordered mesoporous molecular sieves (MCM-41 and MCM-48) as catalysts for asymmetric alkene epoxidation and cyclopropanation

Encapsulation of chiral ruthenium porphyrin [RuII(D4-Por*)CO] in modified mesoporous silica supports such as MCM-41 and MCM-48 achieves active catalysts for asymmetric epoxidation of alkenes by 2,6-dichloropyridine N-oxide and intramolecular cyclopropanation, which is the first example of chiral metalloporphyrin supported on ordered molecular sieves.