镍(II)配合物官能化的MCM-41催化分子氧环氧化苯乙烯

制备了镍(II)席夫碱配合物官能化的MCM-41多相催化剂MCM-41-Ni.利用X射线粉末衍射、氮气物理吸附脱附、红外光谱、热重、电感耦合等离子体原子发射光谱、元素分析和透射电镜等方法对催化剂进行了表征.以氧气为氧化剂,MCM-41-Ni在催化环氧化苯乙烯的反应中表现出较高的催化活性;苯乙烯的转化率为95.2%,环氧苯乙烷的选择性为66.7%.系统地研究了反应温度、催化剂用量、溶剂以及反应时间对反应性能的影响.催化剂经过4次循环仍然表现出较好的稳定性和催化活性.     

Characterization and optimization of mesoporous magnetic nanoparticles for immobilization and enhanced performance of porcine pancreatic lipase

In this paper, Fe₃O₄ nanoparticles coated with mesoporous silica were prepared successfully, noted as Fe₃O₄ at the mobile composition of matter No. 41 (MCM-41). Also, Fe₃O₄ at MCM-41 was grafted by both 3-aminopropyltriethoxysilane (APTS) and 3-chloropropyltriethoxysilane (CPS), noted as Fe₃O₄ at MCM-41/APTS and Fe₃O₄ at MCM-41/CPS. The compounds were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, thermogravimetry and N₂ adsorption/desorption. Then, the enzyme, porcine pancreas lipase (PPL), was immobilized onto these modified nanoparticles by covalent attachment, physical adsorption and cross-linking, noted as Fe₃O₄ at MCM-41/CPS-PPL, Fe₃O₄ at MCM-41-PPL and Fe₃O₄ at MCM-41/APTS-PPL, respectively. The results showed that Fe₃O₄ at MCM-41/CPS was the best nanomaterial for PPL immobilization, exhibiting enhanced immobilization efficiency (maximum 96%), maximum relative activity (up to 96%), high stability and reusability (83% 56 days and 86.7% ten cycles). Additionally, it offered some other advantages, such as easy recycling and reuse, complying with the trend of green chemistry. Therefore, Fe₃O₄ at MCM-41/CPS in combination with a relevant method can be proposed for commercial applications.     

Readily accessible mesoporous silica nanoparticles supported chiral urea-amine bifunctional catalysts for enantioselective reactions

The main objective of this study is to develop readily accessible and recyclable solid catalysts for enantioselective reactions. To achieve this, magnetic MCM-41 and non-magnetic SBA-15 mesoporous supports were prepared, then mesoporous silica supported chiral urea-amine bifunctional catalysts were synthesized by grafting of chiral urea-amine ligand onto SBA-15 and magnetic MCM-41. The magnetic and non-magnetic supports and so-prepared solid catalysts were characterized by using different methods such as N₂ sorption measurements, Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope-energy dispersive X-ray analysis (FESEM-EDX), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Results showed that (1R, 2R) or (1S, 2S)-1,2-diphenylethane-1,2-diamine was successively immobilized onto magnetic MCM-41 and SBA-15 pores. The heterogeneous chiral solid catalysts and their homogenous counterparts exhibited high activities both enantioselective transfer hydrogenation reaction (up to 99% conversion and 65% ee) and enantioselective Michael reaction (up to 98% conversion and 26% ee). Moreover, the SBA-15 supported solid catalysts were separated from the reaction mixture by simple filtration, whereas the magnetic MCM-41 supported solid catalysts were separated by simple magnetic decantation and reused in three consecutive catalytic experiments.     

Mesoporous materials incorporating a zinc(II) complex: Synthesis and direct luminescence quantum yield determination

New luminescent inorganic–organic hybrid materials incorporating the luminescent zinc(II) complex ZnL₂ (λ_em = 457 nm and Φ_em = 4.4% reference values for ZnL₂; HL = chelating ligand resulting from the reaction between salicylaldehyde and 3-aminopropyltriethoxysilane), covalently bonded to different types of mesoporous silica hosts (namely MCM-41, MCM-48 and SBA-15), were prepared via both the methods of grafting post-synthesis (GPS) and one-pot synthesis (OPS). The products obtained, which form the GPS [(GPS)(Zn/MCM-41), (GPS)(Zn/MCM-48), (GPS)(Zn/SBA-15)] and the OPS [(OPS)(Zn/MCM-41), (OPS)(Zn/MCM-48), (OPS)(Zn/SBA-15)] series, contain the ZnL₂ guest covalently bonded to the silica framework through silicon–oxygen bonds formed when the silane group is placed at the periphery of the Zn(II) coordination sphere. GPS and OPS materials were characterized by powder X-ray diffraction, N₂ adsorption/desorption, thermogravimetric analysis (TGA) and UV/vis spectroscopy. For the new mesoporous materials the emission quantum yield (EQY) was measured by means of an integrating sphere combined with a spectrofluorimeter. The ZnL₂ loading (measured by the ZnL₂/SiO₂ ratio calculated from TGA data) for MCM-41 appears to be independent of the synthesis procedure, whereas, for both MCM-48 and SBA-15, the ZnL₂/SiO₂ ratio of the materials obtained via OPS is about four times higher than products obtained from GPS. The ZnL₂ loaded GPS and OPS series show λ_em maxima at about 485 and 455 nm, respectively. Moreover, with reference to EQY (GPS)(Zn/SBA-15) and (OPS)(Zn/SBA-15), although featuring ZnL₂/SiO₂ ratios of 0.13 and 0.45, respectively, they showed similar EQY values: 2% and 5%. On the contrary, (GPS)(Zn/MCM-41) and (OPS)(Zn/MCM-41) which give similar ZnL₂/SiO₂ ratios (0.09 and 0.14) exhibit very different EQY, i.e. 2% and 22%, respectively.     

Degradation and adsorption of rhodamine B and phenol on TiO<Subscript>2</Subscript>/MCM-41

TiO₂/MCM-41 composites with various titania content were prepared by loading titania into the mesopores of MCM-41 molecular sieves by sol-gel method, and were used as photocatalysts to degrade Rhodamine B (RhB) and phenol. The efficiency of organic contaminants removal was increased significantly compared with pure TiO₂. Ti/Si ratio, namely, the content of TiO₂ was determined by ICP-AES method. TiO₂/MCM-41 composites were characterized by X-ray diffraction, UV-Vis absorption spectroscopy and N₂ adsorption techniques. Experimental results demonstrated that most of the RhB was adsorbed instead of being degradated by TiO₂/MCM-41 due to the large specific surface area of MCM-41, while most of phenol was degradated. It turned out that the TiO₂/MCM-41 with the highest Ti/Si ratio of 0.8220 (wt) had the highest catalytic activity.     

(MCM-41)-La_2O_3纳米复合材料的制备、表征及光学性质

借助水热法,以正硅酸乙酯为硅源,十六烷基三甲基溴化铵为模板剂,在碱性条件下制备了纳米MCM-41分子筛。通过固相热扩散法将La2O3组装到MCM-41介孔孔道中,制备出含La2O3不同浓度的(MCM-41)-La2O3主-客体纳米复合材料。采用化学分析、粉末XRD、FTIR、77K低温N2吸附-解吸附、固体扩散漫反射吸收光谱、拉曼光谱、扫描电镜和发光光谱对主-客体复合材料进行表征。粉末XRD结果表明,La2O3组装到MCM-41分子筛的孔道后并未破坏分子筛骨架,在所制备的(MCM-41)-La2O3主-客体纳米复合材料中MCM-41骨架结构仍然具有较高的有序性,并且,随着植入客体材料浓度的增加复合材料的有序度有所降低。红外光谱表明所制备的纳米复合材料主体分子筛骨架完好;低温氮气吸附-解吸附技术表明La2O3已经部分地占据了MCM-41分子筛孔道,导致分子筛的比表面积和孔体积都有所降低;固体扩散漫反射吸收光谱表明吸收光谱的吸收峰发生了蓝移现象,并表现出量子限域效应,说明La2O3已经组装到了MCM-41分子筛的孔道中;拉曼光谱表明所制备的复合材料没有出现新的特征峰,表明La2O3已经组装到了MCM-41分子筛的孔道中;扫描电镜表明(MCM-41)-La2O3样品的外观非常规整,主要呈现的是球状结构,La2O3含量为10%时,(MCM-41)-La2O3的平均粒径为(114±10)nm。发光光谱研究结果表明,所制备的复合材料(MCM-41)-La2O3样品在396nm处具有较好的发光性质,因而具有作为发光材料潜在应用前景。     

Preparation of Solid Superacid Catalysts and Oil Oxidative Desulfurization Using K<Subscript>2</Subscript>FeO<Subscript>4</Subscript>

A \(\rm{SO_4^{2-}}\)/MCM-41 superacid catalyst was prepared by impregnation and characterized by various methods. A novel procedure for oxidative desulfurization of simulated light fuel oil using K₂FeO₄ over \(\rm{SO_4^{2-}}\)/MCM-41 was developed. Fourier transform infrared spectroscopy (FTIR) and low-angle X-ray diffractometry (XRD) show that the material synthesized by the precipitation-sol-hydrothermal method is mobil composition of matter no. 41 (MCM-41). Thermogravimetry/differential thermal analysis (TG-DTA) shows that when the calcination temperature is higher than 300°.     

Surface characterization and catalytic evaluation of copper-promoted Al-MCM-41 toward hydroxylation of phenol

The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6 wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption–desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and ²⁹Si and ²⁷Al magic-angle spinning–nuclear magnetic resonance (MAS–NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS–NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H₂O₂ as the oxidant at 80 °C. The effects of reaction parameters such as temperature, catalyst amount, amount of H₂O₂, and solvent were also investigated. Sample containing 4 wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity.     

Synthesis,characterization of Nafion-functionalized MCM-41 and its catalytic application in preparation of CL-20 via HNO3 electrolyte involved nitration of TAIW

Hybrid organic–inorganic MCM-41 (Mobil Composition of Matter No. 41) silicas functionalized with Nafion (perfluoroalkylsulfonic acid analogous) were prepared and characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and N₂ adsorption analysis. The Brønsted acidity was determined by UV spectrophotometer. The prepared catalyst (SA/MCM-41) exhibited high catalytic activity in the nitration of TAIW (tetraacetylhexaazaisowurtzitan) aiming at synthesizing CL-20 (hexanitrohexaazaisowurtzitane), with the yield up to 93%. The leaching problem was not observed after several runs, demonstrating that the catalyst could be recycled and reused without losing activity.     

A spectroscopic study of the interaction of octacarboxylic metal phthalocyanine with bovine serum albumin

The interaction of octacarboxylic metal phthalocyanines (MPc(COOH)₈, M =?Al(III) and Co(II) with bovine serum albumin (BSA) has been studied. From the binding isotherm based on spectrophotometric titration, the association constant and a number of ligands per binding site were calculated at 25°C. By using the well studied Hemin chloride (HE), Ibuprofen(IB) and L-tryptophan (TRP) as competitive ligands, the binding sites of AlPc(COOH)₈ were found to be on domain I and II of BSA, while on domain I for Co(COOH)₈.     

Synthesis of MCM-41 supported amino-palladium complex and its catalytic performance for heck reaction

Using MCM-41 as the supporter, a series of MCM-41 supported amino-palladium complexes has been prepared and characterized by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy), etc. The XRD and XPS results indicate that the Pd coordinates with the -NH₂ groups on the MCM-41 surface, and the structure of MCM-41 has been not damaged. Its catalytic performance for Heck arylation of alkene with aryl iodide shows that the catalysts have high activity and stereoselectivity in 70–90°C. The product of Heck reaction is in E form. And the effect of the preparation condition of catalyst on the catalytic performance was examined. Translated form Chinese Journal of Organic Chemistry, 2008, 28(5) (in Chinese)     

Comparison of catalytic pyrolysis of biomass with MCM-41 and CaO catalysts by using TGA–FTIR analysis

Pyrolysis of corncob with and without catalyst was investigated using thermogravimetry analyzer coupled with Fourier transform infrared spectroscopy (TGA–FTIR). The effects of two completely different catalysts, acid catalyst (MCM-41) and base catalyst (CaO), on the formation characteristics and composition of pyrolysis vapor were studied. The results show that these two catalysts give different product distributions. For catalytic run with MCM-41, the molality of carbonyl compounds decreases 10.2%, while that of phenols, hydrocarbons and CH₄ increases 15.32%, 4.29% and 10.16% compared with non-catalytic run, respectively. The increase of phenols exhibits in a wide temperature range from about 295 °C to 790 °C in the catalytic run with MCM-41 catalyst. However, the use of CaO in pyrolysis of corncob leads to a huge change of product distribution. The molality of acids decreases 75.88%, while the molality of hydrocarbons and CH₄ increases 19.83% and 51.05% compared with non-catalytic run, respectively. CaO is very effective in deacidification and the conversion of acids promotes the formation of hydrocarbons and CH₄. Catalytic pyrolysis of corncob with CaO shows two main weight-loss stages. The first stage is from 235 °C to 310 °C with a weight loss of 31%. The second stage is from 650 °C to 800 °C with a weight loss of 21%.     

Preparation of non-valence compounds of zinc(II) with 1,2- and 1,4-benzenedicarboxylic acids via self-assembly

Nanostructured non-valence compounds based on coordination compounds of zinc(II) with phthalic and terephthalic acids have been prepared. The purity and composition of prepared compounds have been elucidated from X-ray diffraction analysis, IR spectroscopy, elemental analysis, and thermogravimetry studies; thermal decomposition of the non-valence compounds has been studied as well. The prepared self-assembled compounds are co-precipitated with one water molecule and 1.5 acetic acid molecules per unit of the dicarboxylic acid: [Zn₄(OH)₆·o-C₆H₄(COO)₂]·H₂O·1.5CH₃COOH and [Zn₄(OH)₆·p-C₆H₄(COO)₂]·H₂O· 1.5CH₃COOH.     

Co-templating synthesis of highly dispersed 1D ZnO nanostructures in amorphous SiO2 under hydrothermal condition

One-dimensional (1D) ZnO nanostructures were grown in amorphous SiO₂ matrix by a co-templating method under hydrothermal condition. Using ethylenediamine (EDA) groups grafted mesoporous silica MCM-41 as a co-template, the growth of 1D ZnO nanostructures was oriented by soft EDA groups and confined inside the hard mesochannels of MCM-41. The microstructure and morphology of the 1D-ZnO-nanostructures/SiO₂ composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). All these results indicate that the 1D ZnO nanostructures were synthesized and highly dispersed in the amorphous SiO₂ matrix. Blue-shifted exciton absorption was observed from the co-templating synthesized sample.     

Heterogenization of [Ti(η-C5HMe4)Cl3] on to MCM-41 and organomodified MCM-41 to form epoxidation catalyst

This paper describes the heterogenization of a tetramethylmonocyclopentadienyl titanium (IV) trichloride complex, [Ti(η⁵-C₅HMe₄)Cl₃] onto mesoporous MCM-41. Its immobilization has been performed via a straightforward grafting process of the organometallic precursor in the pores of an MCM-41 host material and by reaction with previously organomodified MCM-41 material with a hydroxyl triazine based compound. Applying all-silica MCM-41 hosts, stable and heterogeneous liquid-phase epoxidation catalysts are obtained. Powder X-ray diffraction and nitrogen adsorption-desorption analysis indicated that the structural integrity of the support has been preserved during the titanium complex immobilization. These materials have been also extensively characterized using diffuse reflectance UV-vis, ¹³C and ²⁸Si MAS NMR and FT-IR spectroscopy. With these techniques the strong adsorption of the intact catalytic complex within an all-silica MCM-41 host is demonstrated. These materials have been tested as catalyst for the epoxidation of aliphatic and aromatic alkenes with TBHP as oxidant exhibiting a significant selectivity toward the epoxide with negligible leaching of titanium species. The conversion values are moderated, being the olefin trend reactivity 1-octene > cyclohexene > styrene.     

Bifunctional metal-free KAUST Catalysis Center 1 (KCC-1) as highly active catalyst for syngas production via methane partial oxidation

The metal-free KAUST Catalysis Center 1 (KCC-1) was synthesized through microemulsion method with microwave assistance and was assessed for methane partial oxidation (MPO) under various operating conditions. The electronic spin resonance spectroscopy, pyridine-probed infrared spectroscopy, and temperature-programmed desorption of oxygen measurement indicated that the concentration of BrØnsted acid sites and oxygen vacancies in KCC-1 were at least 2-fold higher than its counterparts, which benefited MPO activity via the promotion of adsorption and dissociation of gaseous reactants. The principal species detected by post-reaction X-ray photoelectron spectroscopy (XPS) was surface-adsorbed oxygen species; its relative percentages among all oxygen species reduced in the order spent KCC-1 (77.1%) > spent MCM-41 (Mobil Composition of Matter number 41; 41.4%) > spent SiO₂ (?). The catalytic performance followed the same trend, suggesting that the surface-adsorbed oxygen species was the key factor for MPO process. Additionally, the carbon deposition rate increased in the order SiO₂ (16.8 mol/g_cat/s) > MCM-41 (11.7 mol/g_cat/s) > KCC-1 (7.7 mol/g_cat/s), consistent with the results of post-reaction Raman measurements. By coupling the in situ Fourier-transform infrared and XPS results, it is suggested that the high concentration of oxygen vacancies in KCC-1 contributed to activate the CH₄ molecules on acid sites via different O1-assisted kinetically relevant C–H bond activation mechanism for combustion-reforming pathway; meanwhile it provided an excellent adsorption-desorption cycle of O^2? species to inhibit the carbon deposition, thus creating a bifunctional reaction mechanism in MPO reaction.     

Chloro-Modified Magnetic Fe3O4@MCM-41 Core–Shell Nanoparticles for L-Asparaginase Immobilization with Improved Catalytic Activity,Reusability, and Storage Stability

This paper describes a new support that permits to efficient immobilization of L-asparaginase (L-ASNase). For this purpose, Fe₃O₄ magnetic nanoparticles were synthesized and coated by MCM-41. 3-chloropropyltrimethoxysilane (CPTMS) was used as a surface modifying agent for covalent immobilization of L-ASNase on the magnetic nanoparticles. The chemical structure; thermal, morphological, and magnetic properties; chemical composition; and zeta potential value of Fe₃O₄@MCM-41-Cl were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction patterns (XRD), and zeta-potential measurement. The immobilization efficiency onto Fe₃O₄@MCM-41-Cl was detected as 63%. The reusability, storage, pH, and thermal stabilities of the immobilized L-ASNase were investigated and compared to that of soluble one. The immobilized enzyme maintained 42.2% of its original activity after 18 cycles of reuse. Furthermore, it was more stable towards pH and temperature compared with soluble enzyme. The Michaelis–Menten kinetic properties of immobilized L-ASNase showed a lower V_max and a similar K_m compared to soluble L-ASNase. Immobilized enzyme had around 47 and 32.5% residual activity upon storage a period of 28 days at 4 and 25 °C, respectively. In conclusion, the Fe₃O₄@MCM-41-Cl@L-ASNase core–shell nanoparticles could successfully be used in industrial and medical applications.

     

Oxidative dehydrogenation of ethylbenzene to styrene with CO2 over Al-MCM-41-supported vanadia catalysts

Catalytic performance of Al-MCM-41-supported vanadia catalysts (V/Al-MCM-41) with different V loading was investigated for oxidative dehydrogenation of ethylbenzene to styrene (ST) with CO₂ (CO₂-ODEB). For comparison, pure silica MCM-41 was also used as support for vanadia catalyst. The catalysts were characterized by N₂ adsorption, X-ray diffraction (XRD) pyridine-Fourier-transform infrared spectroscopy, H₂-temperature-programmed reduction, thermogravimetric analysis (TGA), UV-Raman, and diffuse reflectance (DR) UV–vis spectroscopy. The results indicate that the catalytic behavior and the nature of V species depend strongly on the V loading and the support properties. Compared with the MCM-41-supported catalyst, the Al-MCM-41-supported vanadia catalyst exhibits much higher catalytic activity and stability along with a high ST selectivity (>98%). The superior catalytic performance of the present V/Al-MCM-41 catalyst can be attributed to the Al-MCM-41 support being more favorable for the high dispersion of V species and the stabilization of active V⁵⁺ species. Together with the characterization results of XRD, TGA, and DR UV–Vis spectroscopy, the deep reduction of V⁵⁺ into V³⁺ during CO₂-ODEB is the main reason for the deactivation of the supported vanadia catalyst, while the coke deposition has a less important impact on the catalyst stability.     

Adsorption of diazinon and fenitothion on MCM-41 and MCM-48 mesoporous silicas from non-polar solvent

The adsorption of two common organophosphorus pesticides, diethoxy-[(2-isopropyl-6-methyl-4-pyrimidinyl)oxy]-thioxophosphorane (diazinon) and dimethoxy-(3-methyl-4-nitrophenoxy)-thioxophosphorane (fenitrothion), by MCM-41 and MCM-48 mesoporous silicas at room temperature was investigated. UVvis and IR spectroscopy, small-angle X-ray diffraction, and the specific surface area analysis (S _BET) were used to study the adsorption behavior of diazinon and fenitrothion. The results show that the MCM-41 and MCM-48 mesoporous silicas adsorb diazinon more efficiently than fenitrothion. The extraction of adsorbed materials from the adsorbents with polar solvents and subsequent analysis by ³¹P NMR showed that the adsorption of diazinon and fenitrothion on mesoporous silicas is destructive and non-destructive, respectively. Nitrogen adsorption measurements showed that the specific surface area of both silicas decreases after the adsorption of pesticides, and the larger effect is observed for diazinon. The article is published in the original.     

镍磷物质的量比对负载型Ni2P/MCM-41催化剂结构及加氢脱硫性能的影响

以MCM-41为载体,采用一种简捷、温和法制备了负载型Ni₂P/MCM-41催化剂。用H₂程序升温还原(H₂-TPR)、X射线衍射(XRD)、N₂吸附比表面积测定(BET)和X射线光电子能谱(XPS)分析对催化剂进行了表征。以1%(质量分数)二苯并噻吩(DBT)的十氢萘溶液为原料,在连续固定床反应装置上,研究了初始Ni/P物质的量比对催化剂HDS活性的影响,并考察了催化剂的稳定性。结果表明,初始Ni/P物质的量比为1/2和1/3的前驱体,在390 ℃下还原时得到单一的Ni₂P相。初始Ni/P物质的量为1/2时,得到的催化剂活性最好。在反应温度340 ℃、压力3.0 MPa、氢/油体积比500、质量空速2.0 h^-1时,DBT的转化率接近100%。