Immobilization of Metalloporphyrin on Functionalized Magnetic Nanoparticles as a Catalyst in Oxidation of Cyclohexene: Novel Modified Fe3O4 Nanoparticles with Triethoxysilane Agent

Magnetic nanoparticles, Fe₃O₄, have been prepared and functionalized by (N-(3-(triethoxysilyl)propyl)isonicotinamide) and characterized by infrared spectroscopy, thermal analysis (TGA/DTA), X-ray powder diffraction, scanning electron microscopy, elemental analysis and BET surface area measurement. The functionalized Fe₃O₄ nanoparticles were used as a support to anchor metalloporphyrin. Application of immobilized metalloporphyrin as a heterogeneous catalyst in the oxidation of cyclohexene was explored. Effect of various parameters such as solvent and temperature on immobilization process and also various parameters (solvent, time, oxidant and axial group effect) on oxidation of cyclohexene has been investigated. The result showed that the immobilized metalloporphyrin on functionalized magnetic nanoparticles is an efficient and reusable catalyst for oxidation of cyclohexene.     

Synthesis of ZnFe2O4 Nanoparticles Confined Within Nanoporous Silica Using Trinuclear Oxo-centered Complex: Inorganic Complexes as a Precursor for the Preparation of Magnetic Nanoporous Silica

MCM-48 Nanoporous silica (Mobil Composition of Matter, #48) was synthesized and functionalized by pyridine groups. The formation of this functionalized nanoporous silica was confirmed by elemental analysis, low angle x-ray powder diffraction and N₂ adsorption. The trinuclear oxo-centered Fe₂Zn(μ₃-O)(CF₃COO)₆(H₂O)₃ cluster was synthesized and immobilized inside the pyridine functionalized MCM-48 pores. The immobilization of this cluster was confirmed by IR spectroscopy and flame atomic adsorption spectroscopy. Fe₂ZnO₄ nanoparticles were confined within the nanoporous silica pores by thermolysis of the immobilized Fe₂Zn(μ₃-O)(CF₃COO)₆(H₂O)₃ cluster and were characterized by high angle X-ray powder diffraction and high resolution transmission electron microscopy. This method is suitable for the one-pot preparation of Fe₂ZnO₄ confined nanoporous silica.     

Total Oxidation of Naphthalene Using Mesoporous CeO2 Catalysts Synthesized by Nanocasting from Two Dimensional SBA-15 and Three Dimensional KIT-6 and MCM-48 Silica Templates

Ceria catalysts have been prepared by a nanocasting procedure using SBA-15, MCM-48 and KIT-6 silica-based templates, and investigated for the total oxidation of naphthalene. In all cases cubic fluorite CeO₂ was prepared, and the structure of the template was replicated when SBA-15 and MCM-48 were used. The KIT-6 template was not replicated by the nanocasting synthesis, but in all cases mesoporous CeO2 was obtained with high surface areas (91–190 m² g^?1). All of the catalysts demonstrated high activity for naphthalene oxidation to CO₂, and the most active was the catalyst prepared from the KIT-6 template. The high activity was attributed to the small crystallite size of the CeO₂, combined with high surface area and the highly accessible catalyst surface.     

Ti-containing MCM-41 catalysts for liquid phase oxidation of cyclohexene with aqueous H2O2 and tert-butyl hydroperoxide

Framework Ti-substituted and Ti-grafted MCM-41 mesoporous material has been prepared by direct hydrothermal synthesis and a post-synthesis grafting method. The materials have been tested as catalysts for cyclohexene oxidation with aqueous H₂O₂ and tert-butyl hydroperoxide (TBHP). With aqueous H₂O₂ in methanol, the major products were cyclohexene diol and its methyl ethers. No cyclohexene oxide was produced. Titanium leaching was a serious problem, and the catalyst lost its activity irreversibly after only one cycle of reaction. With TBHP, the selectivity for cyclohexene oxide was near 100%, titanium leaching was negligible, and the catalyst could be repeatedly used after regeneration without suffering significant activity loss. However, the reaction rate was lower than when H₂O₂ was used. Framework substituted material and catalysts prepared by Ti-grafting onto a MCM-41 support behaved similar, but the Ti-grafted MCM-41 is somewhat more active. The turnover frequency (TOF) per mole of Ti decreases with an increase of Ti content in the catalyst. This is caused by a reduced Ti dispersion within the silica matrix. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ti接枝MCM-48对苯羟化反应的化学亲和选择性及化学稳定性研究

合成了具有较好长程结构和孔结构的Si MCM - 48,以合成后表面接枝改性的方法制备了表面Ti含量不同的Ti接枝MCM - 48催化剂 ,通过X射线衍射 (XRD)、低温N2 吸 -脱附、X射线光电子能谱 (XPS)及原子吸收光谱等对催化剂作了表征 ,Ti接枝MCM - 48仍具有良好的长程有序结构和孔结构 ,其比表面积高于 95 0m2 ·g-1,孔径分布窄 ,随Ti接枝量提高 ,最可几孔径由 2 5nm逐渐降低至 1 9nm。将Ti接枝MCM - 48催化剂用于苯羟化反应 ,研究了其苯羟化性能和结构稳定性 ,结果发现 :Ti接枝MCM - 48对苯羟化反应具有一定活性 ,苯酚选择性高于80 % ,且随表面Ti含量增加 ,苯转化率和苯酚选择性提高。反应后催化剂的孔结构、比表面及孔径分布未受到影响 ,长程有序结构稍有改变     

Gas transport behavior of DMDCS modified MCM-48/polysulfone mixed matrix membrane coated by PDMS

Mesoporous MCM-48 silica was synthesized by templating method and the structure of particles was characterized by XRD, TEM and N₂ adsorption techniques. The surface modification of particles in order for introducing into PSF matrix was performed by dimethyldichlorosilane (DMDCS) silylation agent. SEM images of as-synthesized and modified MCM-48/PSF MMMs indicate that in the modified MCM-48 silica particles adhered well to the PSF matrix and that the synthesized MMMs were defect free. The incorporation of MCM-48 particles in to the PSF matrix and also surface coating of these MMMs by polydimethylsiloxane (PDMS) were performed. The quality of surface coating was investigated by SEM images and permeability tests. For all gases tested (N₂, CO₂, CH₄ and O₂), the permeabilities increased in proportion to the weight percent of MCM-48 present in the film and the calculated CO₂/CH₄ and O₂/N₂ selectivities of PDMS coated membranes showed enhancement in ideal and actual selectivities both.     

Synthesis, characterization and catalytic properties of MCM-36 pillared via the MCM-56 precursor

Pillared layered MCM-36 zeolite (MCM-36-I) was successfully synthesized from MCM-56 precursor with polymeric silica as the pillaring agent. The structure and properties of the sample was characterized by means of N₂ adsorption, XRD, TEM and IR spectroscopy of pyridine adsorption. The results showed that MCM-36-I has higher external surface area and more Brönsted acidic sites on external surface than that on the MCM-36 sample (MCM-36-II) which was synthesized from layered MCM-22 precursor. The catalytic properties of these samples were tested for alkylation of benzene with isopropanol. Compared with MCM-36-II catalyst, MCM-36-I showed higher conversion of benzene and selectivity to cumene. This should be mainly assigned to the fact that MCM-36-I possesses larger amount of accessible Brönsted acid sites which located on the external surface than that of MCM-36-II.     

MCM-48 supported chromium catalyst for trichloroethylene oxidation

MCM-48 supported chromium (Cr/MCM-48) catalyst was prepared by introduction of chromium chloride during gel-preparation for the hydrothermal synthesis of MCM-48. Based on the N₂ adsorption/desorption isotherm, BET, pore size distribution, XRD, FTIR, TGA, and DTA data, Cr/MCM-48 was found to have high surface area (832 m²/g), uniform pore size distribution (24 Å), mesoporous structures similar to MCM-48 itself, and incorporation of about 3 wt% of Cr component in the mesoporous framework. Cr/MCM-48 was very active for the oxidative destruction of trichloroethylene (TCE), which is a typical chlorinated volatile organic compound (CVOC); 100% conversion of TCE was achieved at 350°C. Based on the TGA of trichloroethylene/water adsorption study, it was found that MCM-48 had high adsorption capacity (>0.25 g TCE/g catalyst). In addition, the hydrophobicity of the adsorptive properties of Cr/MCM-48 materials could be modified. The high adsorption capacity and catalytic activity of Cr/MCM-48 material make it suitable for adsorption/catalysis bifunctional systems for energy-saving treatment of low concentration of VOC or CVOC.     

Synthesis of mesoporous carbon supports via liquid impregnation of polystyrene onto a MCM-48 silica template

Mesoporous MCM-48 was synthesised and used as a template to synthesise mesoporous carbon materials. Polystyrene, the carbon source, together with sulfuric acid and toluene were added to the template (160 °C for 6 h) and this procedure generated a low surface area carbon supported/MCM-48 material. A repeat addition and carbonisation step was needed to form the precursor carbon/MCM-48 material that was pyrolysed at 900 °C to generate graphitic mesoporous carbon materials, characterised by XRD, HR-TEM, Raman spectroscopy and surface area analysis. The effect of the amount of polystyrene as well as the role of the pyrolysis temperature on the final product was investigated. This synthesis methodology can readily be controlled to produce partially ordered graphitic mesoporous carbon supports with predictable pore width and surface area.     

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.     

Hydrocracking of petroleum gas oil over NiW/MCM-48-USY composite catalyst

MCM-48-USY composite materials were prepared by coating USY zeolite by a layer of MCM-48 mesoporous material at different meso/microporous ratios (SiO₂/USY ratios of 0.1, 0.2, 0.3, 0.4, 0.5) and used as support for nickel and tungsten. The NiW/MCM-48-USY catalysts were prepared using the incipient wetness method. The prepared catalysts were characterized by TPD-TGA acidity, TGA thermal stability, BET surface area, pore volume, pore size, XRD, SEM and TEM and then tested for hydrocracking of petroleum gas oil at reaction temperature of 450 °C, contact time of 90 min and catalyst to gas oil ratio of 0.04. In all prepared samples, the catalyst activity and properties were improved with increasing SiO₂/USY ratio and found that maximum values of a total conversion and liquid product (total distillate fuels) were obtained at SiO₂/USY ratio of 0.5. Finally, the obtained results from hydrocracking of gas oil over composite MCM-48-USY catalysts were compared with those obtained over physically mixed USY and MCM-48 catalysts.     

Fe(III)-salim anchored MCM-41: synthesis,characterization and catalytic activity towards liquid phase cyclohexane oxidation

Abstract  

A novel organic–inorganic hybrid catalyst [MCM-41-Fe^III(salim)] was synthesized by covalently anchoring Fe^III(salim) complex into the pore channels of MCM-41. The material was synthesized by the co-condensation of tetraethyl orthosilicate (TEOS) and the precursor of salicylaldehyde modified with 3-aminopropyl triethoxysilane in the presence of cetyltrimethyl ammonium bromide (CTAB). The Fe(III)-salicylideneimine MCM-41 mesoporous silica was generated (in situ) by taking MCM-41-salimH (I) and FeCl₃ in ethanol solution. The immobilization of the complex on the functionalized silica was confirmed by small angle X-ray diffraction (XRD), N₂ adsorption–desorption, electron paramagnetic resonance (EPR), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance UV–vis spectroscopy. Solid state CP-MAS NMR spectroscopy of ²⁹Si (²⁹Si CP-MAS NMR) showed a highly condensed siloxane network. Catalytic activity of the supported catalyst was examined by the oxidation of cyclohexane. Cyclohexane was successfully oxidized in good conversion (68%) to cyclohexanone, as a major product with 72% selectivity using tert. butylhydroperoxide as oxidant and acetonitrile as solvent. The catalysts can be reused up to three cycles without losing much of its activity.     

Synthesis,characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using co-templates of gemini surfactant [C₁₈H₃₇N(CH₃)₂(CH₂)₃-N(CH₃)₂C₁₈H₃₇]²⁺ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 ?. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520–600 cm⁻¹ in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N₂ adsorption data showed that the material had a much higher specific surface area (1 200 m²/g) than the conventional MCM-48(1 100 m²/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(1): 105–108 [译自: 燃料化学学报]     

Synthesis,characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using cotemplates of gemini surfactant [C₁₈H₃₇N(CH₃)₂(CH₂)₃N(CH₃)₂C₁₈H₃₇]²⁺ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 Å. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520 600 cm^-1 in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N2 adsorption data showed that the material had a much higher specific surface area (1 200 m₂/g) than the conventional MCM-48(1 100 m₂/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules.     

Microporosity in Mesoporous SBA-15 Supports: A Factor Influencing the Catalytic Performance of Immobilized Metalloporphyrin

MnTMPyP cationic metalloporphyrin was immobilized by means of ion exchange on a series of aluminated SBA-15 mesoporous silica supports prepared by different methods. The solids were characterized with XRD, HRTEM, HRSEM, chemical analysis, and nitrogen sorption isotherms. The catalysts were tested in the reaction of cyclohexene oxidation with iodozobenzene. It was found that immobilization significantly enhances catalytic activity as compared to the homogeneous system. In contrast to previously investigated metalloporphyrin catalysts immobilized on aluminated HMS, MCM-41 or FSM-16 type supports, where too narrow pores limited the formation of epoxide and enhanced allylic oxidation, the use of aluminated large pore SBA-15 solids favoured the epoxidation pathway and resulted in yields significantly higher than in the case of homogeneous reaction. The catalysts showed important differences in the level of allylic oxidation. Analysis of various factors potentially influencing the product distribution demonstrates that the key role in determining the contribution of allylic oxidation is the microporosity nature of the support, in particular, the lack or presence of supermicropores capable of accommodating metalloporphyrin species. The MnTMPyP centres confined in supermicropores experience steric limitations, which do not allow for the formation of epoxide and favour allylic oxidation.     

Preparation and catalytic properties of a new dioxomolybdenum(VI) complex covalently anchored to mesoporous MCM-48

Reaction of the solvent adduct MoO₂Cl₂(THF)₂ with the 1,4-diazabutadiene ligands RNC(Ph)C(Ph)NR [R = (CH₂)₂CH₃, (CH₂)₃Si(OMe)₃] leads to complexes of the type MoO₂Cl₂(LL) in good yields at room temperature within a few minutes. The complex bearing the trimethoxysilyl groups was immobilized in the ordered mesoporous silica MCM-48 by covalent bonding. Solid state MAS NMR spectroscopy (¹³C, ²⁹Si) confirms that the structural integrity of the complex was retained during immobilization, except for loss of methoxide groups due to the reaction with surface silanols. Powder X-ray diffraction (XRD) and N₂ adsorption studies of the derivatized material indicate that the textural properties of the support were preserved during the grafting experiment and that the channels remained accessible. The modified material is active and selective in the epoxidation of cyclooctene at 55 °C using tert-butyl hydroperoxide as the oxidant. Stability was checked by recycling the solid catalyst several times. Some activity is lost from the first to second runs, but thereafter stabilizes. The catalytic behavior of the heterogenized catalyst was also compared with that observed in homogeneous phase for the complex with R=(CH₂)₂CH₃.     

含氟体系中合成条件对MCM-48分子筛结构性能的影响

在合成过程中引入F~-可以缩短MCM-48分子筛的晶化时间,考察以正硅酸乙酯(TEOS)为硅源、十二烷基三甲基溴化铵(CTAB)为模板剂的合成体系中加入F~-后,n(CTAB)∶n(Si)、晶化时间和晶化温度等合成条件对MCM-48结构性能的影响。XRD、N_2吸附脱附和TEM等表征结果表明,在n(CTAB)∶n(Si)=0.65、晶化温度120℃和反应时间24 h条件下,合成的MCM-48分子筛结晶度较高,比表面积为1 305 m~2·g~(-1),平均孔径3.416 nm,为MCM-48分子筛的适宜合成条件。     

Preparation of Titanium Oxide Supported MCM-48 by the Designed Dispersion of Titanylacetylacetonate

Titaniumoxide supported MCM-48 was prepared by a novel synthesis method, utilizing titanylacetyl-acetonate as the Ti source. The process consists of an adsorption and subsequent thermolysis of the Ti-complex. The interaction of the complex with the surface was studied by FTIR, TGA and chemical analysis. Further characterization was done by XRD, Raman, UV-DR and N₂ adsorption measurements. The Ti-complex is irreversibly adsorbed on the MCM-48 surface by a hydrogen bonding mechanism independent of the Ti loading. During calcination, the supported TiO(acac)₂ complex is converted towards supported titaniumoxide, whereby the Ti atoms are partly incorporated into the pore walls of MCM-48. The adsorption of TiO(acac)₂ is an efficient way to create supported titaniumoxides with a high surface area.     

Synthesis and characterization of tungsten-incorporated mesoporous molecular sieve MCM-48 by one step

Tungsten-substituted mesoporous MCM-48 materials are successfully synthesized at 393 K by a one-step co-condensation sol–gel method. The prepared samples with different Si/W ratios are characterized by X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), diffuse reflectance UV–visible spectroscopy and FT-IR, and the results indicate the presence and good dispersion of tungsten species inside the silica pores, the Si/W ratio is controlled above 28. When the Si/W ratio is less than 28, though no bulk tungsten is detected outside the MCM-48 mesoporous silica, the pore structure order becomes worse.     

MCM-48负载SO42-/ZrO2定位催化硝化合成3,4-二甲基硝基苯

采用液相沉积法制备了由MCM–48介孔分子筛负载SO42－／ZrO2的催化剂,探讨了催化剂表面的成酸过程和催化定位硝化反应机理,并以邻二甲苯和硝酸定位硝化反应为探针反应,考察了催化剂的性能;用酸碱滴定、TEM、N2吸附-脱附和Hammett指示法表征了固体超强酸。结果表明,固体超强酸保持了MCM-48的介孔结构,BET表面积高达208 m2/g,表面含有质子酸和路易斯酸中心,且具有强酸性（H0＜－13.75）;得到适宜的工艺条件：催化剂培烧温度500 ℃,反应温度60 ℃,n(硝酸)/n(邻二甲苯)＝2.5,m(邻二甲苯)/m(催化剂)＝25,反应时间3 h,产物收率为91.8%,含量达到82.1%。