Sn修饰SBA-15、MCM-41催化剂的制备及顺酐酯化性能

以SBA-15和MCM-41分子筛为载体,负载无水四氯化锡,制备了SnCl4-SBA-15和SnCl4-MCM-41催化剂,考察了不同锡与硅物质的量比对催化顺酐与正丁醇酯化反应的影响。结果表明,SnCl4-SBA-15表现出比SnCl4-MCM-41更高的催化性能,顺酐转化率为99.8%,副产物较少,马来酸二丁酯的产率最高可达91.3%。采用X射线衍射、N₂物理吸附、傅立叶红外光谱和紫外-可见漫反射技术对催化剂进行表征,结果显示, SnCl₄-SBA-15具有较高的比表面积,较大的孔容和孔径,更有利于催化反应的进行。     

Different dispersions of group II catalysts over SBA-15 and MCM-41: Effects on transesterification reactivity

Activities of CaO catalysts on SBA-15 and MCM-41 have been compared in transesterification and SBA-15 supported samples are invariably more active than those on MCM-41. Increased activity is not due to diffusional effects (as measured using substrates of differing size) but rather to increased dispersion of CaO on SBA-15 (as measured using NOx TPD). The effect, i.e. increased reactivity of SBA-15 supported catalysts being related to increased dispersion, is also noted in supported BaO catalysts while supported MgCO₃ catalysts show little variation in dispersion (or in reactivity) as a function of the support used.     

Characterisation and catalytic properties of MCM-41 and Pd/MCM-41 materials

Pure silica MCM-41 mesoporous molecular sieve material was synthesised and characterised by in situ synchrotron XRD, TEM, TGA/DTA and DRIFTS techniques. In situ energy dispersive XRD (EDXRD) confirmed the exact nature of the pore diameter of MCM-41 and the change in crystal structure on calcination. The IR band at 1057 cm^-1 of as-synthesised MCM-41 was shifted by 14 cm^-1 on heating to 673 K due to increased condensation of silanol groups to form Si-O-Si bridges. Calcined MCM-41 materials were used to support Pd, and the catalytic activities for 1-hexene and benzene selective hydrogenation were investigated. The Pd/MCM-41 catalyst showed high activity in hydrogenation of 1-hexene at an inlet reaction temperature of 298 K, but did not show any activity in hydrogenation for benzene. TEM results for the reduced Pd/MCM-41 catalysts revealed that the average Pd particle size was around 2-2.5 nm and these particles were located in the pores of MCM-41 and showed good distribution. TPR measurements showed that about 70% of palladium oxide (PdO) loading in the calcined catalysts was reduced at sub-ambient temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

有序介孔分子筛SBA-15/MCM-41在电催化方面的应用

介绍了有序介孔材料的分类与发展,针对目前电催化领域存在的问题,综述了介孔分子筛SBA-15/MCM-41材料在电催化方面的应用。     

MCM-41 catalyzed rapid and efficient one-pot synthesis of polyhydroquinolines via the Hantzsch reaction under solvent-free conditions

A one-pot four-component reaction of aldehydes, 5,5-dimethyl-1,3-cyclohexanedione, ethyl acetoacetate and ammonium acetate has efficiently been carried out in the presence of 1 mol% of MCM-41 as a heterogeneous catalyst in a solvent-free media at 90 °C to form the corresponding polyhydroquinoline derivatives via the Hantzsch reaction. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction time (15–25 min), milder conditions and the remarkable reusability of the catalyst, MCM-41.     

MCM-41 catalyzed rapid and efficient one-pot synthesis of polyhydroquinolines via the Hantzsch reaction under solvent-free conditions

A one-pot four-component reaction of aldehydes, 5,5-dimethyl-1,3-cyclohexanedione, ethyl acetoacetate and ammonium acetate has efficiently been carried out in the presence of 1 mol% of MCM-41 as a heterogeneous catalyst in a solvent-free media at 90 °C to form the corresponding polyhydroquinoline derivatives via the Hantzsch reaction. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction time (15–25 min), milder conditions and the remarkable reusability of the catalyst, MCM-41.     

Selective benzylic oxidation of alkylaromatics over Cu/SBA-15 catalysts under solvent-free conditions

With the purpose of benzylic oxidation of alkylaromatics into corresponding ketones selectively under solvent-free conditions, cheap, simple and versatile Cu/SBA-15 catalyst system with the Cu loading of 5, 10, 15 and 20% has been prepared by impregnating SBA-15 support. Among Cu/SBA-15 catalysts, 10%Cu/SBA-15 exhibited superior activity and selectivity.     

Room temperature blue-green photoluminescence of MCM-41, MCM-48 and SBA-15 mesoporous silicas in different conditions

The photoluminescence (PL) properties of siliceous MCM (MCM-41 and MCM-48) and SBA-15, no Na-containing MCM-41, and modified SBA-15 by silylation were comparatively investigated in dry and damp conditions, displaying the highest PL intensity of MCM-48. The PL intensity of MCM-41 is lower than that of SBA-15 in dry conditions, but reverse in damp conditions. In comparison with that of Na-containing MCM-41, the PL intensity of MCM-41 without Na⁺ is stronger. The PL intensity of modified SBA-15 by silylation is decreased in dry conditions, and however, against moisture and degradation in damp conditions. Twofold coordinated silicon centers in the tested samples are responsible for the blue-green bands at 440 nm. The shoulder peaks around 460–490 nm occurred in damp conditions are assigned to peroxy free radicals.     

Sulfonic acid functionalised SBA-15 as catalysts for Beckmann rearrangement and esterification reaction

Hybrid inorganic–organic solid acid materials SBA-15–Ph–SO₃H were synthesized by the directly co-condensation method under the acid medium. The resulting materials perform well both in the liquid phase Beckmann rearrangement (The yield is 32.3%) and esterification reaction (The yield is 95.5%). And more, the catalysts show the different catalytic performance in these two reactions.     

The use of palladium nanoparticles supported with MCM-41 and basic (Al)MCM-41 mesoporous sieves in microwave-assisted Heck reaction

A series of supported catalysts has been obtained by grafting of chemically generated palladium nanoparticles onto basic, Cs⁺ ion-exchanged molecular sieves (Al)MCM-41 and onto the non-basic, parent material MCM-41. Catalytic activity of the catalysts has been investigated in the Heck reaction between bromobenzene and butyl acrylate under microwave irradiation. The activity of the bifunctional catalysts (Pd@Cs⁺-(Al)MCM-41) and the activity of Pd@MCM-41 combined with sodium acetate as an external base were considerably higher under microwave irradiation than activities observed for the same catalytic systems under the conventional heating. The Pd@MCM-41/NaOAc system showed higher conversions than the bifunctional catalysts presumably due to a different nature and accessible amount of the base. On the other hand, microwave irradiation seems to increase the rate of aggregation of the metallic particles and thus also catalyst deactivation as compared with the usual heating.     

Green Synthesis for MCM-41 and SBA-15 Silica Using the Waste Mother Liquor

Silicon - In an attempt to synthesize silicas with respect to green chemistry, the synthesis of MCM-41 and SBA-15 silicas by a low-cost approach through the recycling of waste mother liquors was...     

Restrictive diffusion and hydrodesulfurization reaction of dibenzothiophenes over NiMo/SBA-15 catalysts

Macromolecular organosulfur compounds encountered resistance when diffusing in catalyst pore channels during the hydrotreating process. Quantitative insights into the effects of the catalyst pore size and the reactant molecule size on the diffusivities can guide the optimization of the catalyst structures. Herein, a heavy oil macromolecular dibenzothiophene compound, 2,8-di-(4-pentyl phenyl)dibenzothiophene (2,8-DPPDBT), was synthesized. Three NiMo-supported SBA-15 based catalysts with different pore sizes, but similar active phase dispersions were controllably fabricated. The reaction network of 2,8-DPPDBT HDS was proposed. The diffusion behaviors of 2,8-DPPDBT, along with 2,8-dimethyl dibenzothiophene (2,8-DMDBT) and dibenzothiophene (DBT) in three SBA-15 pore channels, were systematically investigated through the reaction kinetic method. A restrictive factor, F(λ), was correlated by F(λ) = (1 − λ)^8.5 to determine the relationship between the effective diffusivity and the ratio of the molecule-to-pore size (λ). This empirical correlation provided sound theoretical guidance on the design of highly efficient heavy oil hydrodesulfurization catalysts.     

Co掺杂对Ce/MCM-41和Ce/SBA-15催化剂催化氧化甲苯性能的影响

以分子筛为载体,采用等体积浸渍法制备Ce/SBA-15、Ce/MCM-41、Ce Co/SBA-15和Ce Co/MCM-41催化剂。用N2吸附-脱附、X射线衍射、扫描电子显微镜、H2程序升温还原、X射线光电子能谱和傅立叶变换红外光谱等对载体和催化剂进行表征,并考察催化剂催化氧化甲苯的活性。结果表明,与载体相比,随着Ce和Co的浸渍,催化剂的比表面积和孔容下降,但仍然保持了载体的有序介孔结构。引入的Ce和Co没有进入分子筛骨架,而是以立方相固溶体形式存在于分子筛表面和孔道中。催化剂催化氧化甲苯活性顺序依次为:Ce Co/SBA-15>Ce Co/MCM-41>Ce/MCM-41>Ce/SBA-15。共浸渍Ce和Co的催化剂活性明显优于只浸渍Ce的催化剂,活性与其还原性能直接相关,Ce Co/SBA-15催化剂具有最低的还原温度和最好的供氧能力,从而表现出最优的催化性能。     

Cerium-containing MCM-41 materials as selective acylation and alkylation catalysts

The synthesis of Ce–MCM-41, Al–MCM-41 and Ce–Al–MCM-41-type mesoporous materials was carried out hydrothermally by refluxing the gel with magnetic stirring under atmospheric pressure for 24–36 h. The samples were characterized thoroughly in order to obtain the structural and textural properties, which reveal the presence of well-ordered M41S-type materials. The Ce–MCM-41 samples were used for catalytic acylation of alcohols, thiols, phenols and amines show good activity and selectivity including high chemoselectivity towards selective monofunctional acylation of bifunctional compounds. Quite importantly the acylation of bulky molecules such as cholesterol, ergesterol and β-sitosterol could be achieved using Ce–MCM-41 as solid catalyst. The presence of Ce along with Al in Ce–Al–MCM-41 was found to have synergistic effect as Ce–Al–MCM-41samples were more active catalysts for alkylation of naphthalene compared to either Ce–MCM-41 or Al–MCM-41 with comparable Si/Al or Si/Ce molar ratio.     

Peculiarities of functionalization of mesostructured silicates MCM-41 and SBA-15 by a sulfide modifier

The synthesis and physical-chemical characteristics of sorbents based on mesoporous silicates MCM-41 and SBA-15 with grafted sulfide functional groups are described. Similar experiments were performed on silica gels for the comparison. For the above materials, the X-ray and texture characteristics before and after functionalization, as well as the grafted groups content and the sorption parameters of sorbents, have been determined using physical-chemical methods. The effect of the different conditions of the modification process on the grafting density of sulfide groups has been investigated. The evaluation of the sorption capacity of the obtained materials with respect to Pd(II) ions has been performed: the capacity is around 0.55 mmol/g, the recovery degree is 98–99% and the distribution coefficient is 26000 cm³/g.     

Methanol synthesis over Pd/SiO2 with narrow Pd size distribution prepared by using MCM-41 as a support precursor

All silicious MCM-41 was investigated as a support or a support precursor for Pd/SiO₂ and prepared catalysts were tested for methanol synthesis from CO and H₂. The methods of Pd loading on the MCM-41 were impregnation, seed impregnation and chemical vapor deposition (CVD). For both impregnations, most Pd existed outside of the pore as large particles, and only a small part of Pd was inserted into the pore of MCM-41 retaining the initial structure. On the contrary, in the catalyst prepared by CVD method, the MCM-41 structure was completely destroyed to become amorphous SiO₂. Yet the average Pd particle size in this catalyst was smaller and its distribution was narrower than those of the catalysts prepared by impregnation methods. In the methanol synthesis from CO hydrogenation the catalyst prepared by CVD showed higher methanol selectivity than other MCM-41-derived catalysts. This result was considered to be due to the more uniform distribution of the Pd particle size.     

An efficient oxidation of cyclohexane over Au@TiO2/MCM-41 catalyst prepared by photocatalytic reduction method using molecular oxygen as oxidant

Cyclohexane oxidation using molecular oxygen as oxidant is one of the most challenge subjects. A novel photocatalytic reduction method to prepare Gold nanoparticles Au@TiO₂/MCM-41 was proposed. The prepared samples were characterized by XRD, N₂ adsorption isotherm, FT-IR, TEM and EDS. The results showed that gold nanoparticles were well-dispersed on TiO₂/MCM-41, and TiO₂ was dispersed on the surface of the support and the gold existed as Au⁰. Newly-developed catalyst was promising for the cyclohexane oxidation, achieving a turnover frequency (TOF) as high as 29,145 h^− 1 with 9.87% conversion of cyclohexane.     

MCM-41和SBA-15动态吸附VOCs特性和穿透模型

采用模板剂法制备了具有规整孔道的MCM-41和SBA-15介孔分子筛,考察了两种介孔分子筛动态吸附甲苯、邻二甲苯、均三甲苯的特性.结果表明,MCM-41平均孔径小,孔壁叠加作用力强,更适合吸附中、低浓度的VOCs,对芳烃类VOCs为典型的I型吸附等温线;SBA-15具有微孔和介孔共存的特点,平均孔径大,对大分子和高浓度...     

2-Aminopyridine functionalized cellulose based Pd nanoparticles: An efficient and ecofriendly catalyst for the Suzuki cross-coupling reaction

A palladium catalyst supported on 2-aminopyridine functionalized cellulose was synthesized and fully characterized by inductively coupled plasma atomic emission spectroscopy, transmission electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectrometry. This catalyst can be applied in the Suzuki cross-coupling reaction of aryl halides with arylboronic acids in 50% ethanol to afford biaryls in good yields, and easily recycled by simple filtration after reaction without the loss of metal Pd.

Open image in new window

     

Nanofibrous ultrahigh molecular weight polyethylene synthesized using TiCl<Subscript>4</Subscript> as catalyst supported on MCM-41 and SBA-15

Nanofibrous ultrahigh molecular weight polyethylene (UHMWPE) was synthesized via Ziegler–Natta catalyst anchoring on MCM-41 and SBA-15 as supported catalysts, respectively. These supported catalysts exhibited high activity at different temperatures and Al/Ti ratios, and showed different polymerization kinetics behaviors which were well explained by their different pore structures. The ultrahigh molecular weight of polyethylene might be due to the restrained spaces of the supported catalysts mesopores prohibiting the polymer chains transfer reaction. The obtained nanofibrous morphology might be for the high enough stress generated in the mesopores extruding the polymer out to form.