环己烷催化氧化制环己酮的MCM-41催化剂研究

以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,采用水热合成法制备纯MCM-41分子筛和掺杂不同金属离子的MCM-41分子筛,并采用等体积浸渍法将一定量的金属离子负载在纯MCM-41分子筛内表面上,制备了负载型和掺杂型2类不同的MCM-41分子筛催化剂.分别考察了负载和掺杂的金属种类、金属Cr负载和掺杂量等对环己烷氧化制环己酮中的催化活性和选择性的影响.研究表明:采用掺杂制备的MCM-41分子筛催化剂活性明显高于负载型MCM-41分子筛催化剂;Cr掺杂量增加,虽然环己烷氧化转化率增加,但产物选择性下降;掺杂Cr的MCM-41分子筛催化剂,用于环己烷氧化制环己酮,在Si与Cr摩尔比为50以下、反应温度75℃、H2O2与环己烷摩尔比为1.2的条件下,环己烷的转化率可达60%左右,环己酮和环己醇的总选择性可达94%以上.     

Methanol oxidation on LaCo mixed oxide supported onto MCM-41 molecular sieve

Lanthanum cobaltate LaCoO_x supported onto MCM-41 mesoporous molecular sieve was prepared by in-situ oxidative decomposition of mixed LaCo citrate complexes inside the mesopores of this support. The prepared materials were characterized by EDX, EPR and UV-Vis DRS techniques as well as by N₂-BET measurements. The nanosized LaCoO_x particles within the mesopores of MCM-41 matrix contains cobalt atoms in lower than Co(III) average oxidation state. Also, the supported cobaltate does not form short-range order species of LaCoO₃ but presents as the highly disordered, oxygen deficient Co oxide nanophase. Catalytic activity in MeOH oxidation was tested using both conventional fixed-bed flow system and “operando” mode of DRIFT technique. The very high activity of MCM-41-supported cobaltate is not only due to highly dispersed LaCoO₃ phase but also because of rather low oxidation state of Co.     

Iron, cobalt or nickel substituted MCM-41 molecular sieves for oxidation of hydrocarbons

A series of mesoporous Fe-MCM-41, Co-MCM-41 and Ni-MCM-41 catalysts with different quantity of the metal incorporated in the framework were synthesized and characterized (as-synthesized samples and those after reaction) by X-ray diffraction pattern (XRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of the incorporated metal on the MCM-41 surface hydroxyl groups has been evidenced. The catalytic activity and selectivity of these catalysts in liquid phase oxidation of 1-hexene, styrene and benzene with hydrogen peroxide were studied. The structure and morphology of the catalysts before and after reaction were also compared. The results show a high activity and selectivity of catalysts having higher Co content to benzaldehyde from styrene or phenol from benzene, and a low activity of all prepared catalysts in the oxidation of the 1-hexene. The activity and efficiency of H₂O₂ increases with the metal content and depend on the reaction parameters such as temperature, molar ratio of the reactants and the solvent, and the nature of the reactor.     

Mesoporous (Cr)MCM-41 and (Cr)MCM-48 Molecular Sieves: Promising Heterogeneous Catalysts for Liquid Phase Oxidation Reactions

Chromium-containing mesoporous MCM-41 and MCM-48 silicate molecular sieves were synthesized and characterized. Unlike the chromium-containing microporous materials, the mesoporous analogues show significant activity for the chosen (ethylbenzene oxidation) reaction even after several recycling or washing treatments.     

Catalytic Oxidation of Alkylaromatics over Mesoporous (Cr)MCM-41

Liquid-phase catalytic oxidation of certain alkylaromatics over mesoporous (Cr)MCM-41 molecular sieves in the presence of chlorobenzene and tertiary butylhydroperoxide showed high substrate conversion and excellent product selectivity. The high catalytic activity of the materials is attributed to the complete oxidation of chromium ions to hexavalent chromium and the absence of pentavalent chromium in the mesoporous matrix.     

Synthesis of a siliceous MCM-41 using C22TMACL template and preparation of heterogenized new chiral salen complexes

Purely siliceous MCM-41 has been prepared under both mild and acidic conditions by a solvent evaporation method using C₁₆TMABr and C₂₂TMACl surfactant as templates. A hydrothermal synthesis was also carried out by utilizing a method of adjusting the gel pH to 10. The mesoporous samples synthesized in ethanol solvent by using this evaporation method showed a fully disordered pore system, but those obtained in the hydrothermal synthesis had highly ordered pores. The chiral salen Mn(III) complexes were immobilized on the siliceous MCM-41 by a new grafting method using 3-aminopropyltrimethylsilane and diformylphenols. These ligands on MCM-41 were stable during the reactions. High enantioselectivities were displayed in the epoxidation of styrene by using these heterogenized salen complexes.     

Immobilization of a zirconium complex bearing bis(phenoxyketimine) ligand on MCM-41 for ethylene polymerization

A novel zirconium complex bearing bis(phenoxyketimine) ligand (1) bis((3,5-di-tert-butyl-C₆H₂-2-O)PhCN(2,4-di-fluoro-C₆H₃))ZrCl₂ (2) was prepared and successfully immobilized on a mesoporous molecular sieve MCM-41 in chemical method. Results of slurry polymerization of ethylene with MCM-41-supported catalyst (MC) indicated that the morphologies of polyethylene obtained differed greatly in heptane and toluene. Homogeneous catalyst 2 exhibited a very high initial activity in ethylene polymerization at room temperature resulting in great viscosity of the system. When immobilized on MCM-41, MC showed a smooth yet highly active kinetic behavior. With MAO as the cocatalyst, the effects of Al/Zr molar ratio and polymerization temperature on catalytic activity and properties of polyethylene obtained were investigated. The results showed that polyethylene obtained with MC possessed higher molecular weight (M_n) and broader molecular weight distribution (M_w/M_n) than those formed with its homogeneous counterpart.     

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。     

Mercapto-Functionalized MCM-41 Anchored Palladium(0) Complex as an Efficient Catalyst for the Heterogeneous Suzuki Reaction

Mercapto-functionalized MCM-41 anchored palladium(0) complex is an efficient catalyst for the heterogeneous Suzuki reaction of arylboronic acids with aryl halides. Our system not only solves the basic problems of catalyst separation and recovery but also avoids the use of phosphine ligands.     

新型纳米MCM-41合成研究

本实验合成未脱除模板剂的MCM-41分子筛,然后进行焙烧使模板剂炭化,生成碳纳米丝,留在孔道中。对MCM-41进行XRD检测,考察了晶化温度、晶化时间、硅铝比、水量等各因数的影响。结果表明,强酸性介孔晶体分子筛的生成,受铝含量的影响很大,模板剂的用量增加也有利于产物的生成,受水含量的影响不大。在实验的基础上,对一些不理想的步骤也提出了一些改进方法。     

制备条件对介孔分子筛MCM-41形貌的影响研究

本文以正硅酸乙酯(TEOS)为硅源,十六烷基三甲基溴化铵(CTAB)为介孔模板剂制备MCM-41介孔分子筛,通过改变制备体系条件来调控MCM-41的形貌,考察了制备体系水用量、制备体系氨水用量、TEOS滴加速率对所得MCM-41产物形貌的影响。结果表明:制备体系水用量和氨水用量增大会使所得产物由棒状向球形颗粒转变,TEOS滴加速率加快有利于形成尺寸均匀的棒状MCM-41。最后对MCM-41形貌演变过程进行了分析。     

不同负载方式Fe/改性MCM-41催化剂的制备及其降解亚甲基蓝性能研究

以自制二元共聚物聚[苯乙烯—3-（甲基丙烯酰氧）丙基三甲氧基硅烷]改性MCM-41,并以其为载体分别采用浸渍负载活性金属、原位负载活性金属和NaBH₄还原负载活性金属的方式制备铁基异相催化剂。研究了3类催化剂降解亚甲基蓝的性能差异。结果显示,在3种催化剂中,浸渍负载活性金属制备的催化剂具有最好的催化活性,25 min时亚甲基蓝去除率为81.2%。同时采用XRD、TEM、FTIR、XPS、压汞测试等手段分析了催化剂具有优异性能的原因。表征结果表明:Fe与改性MCM-41间的相互作用及催化剂孔结构,两者的协同作用是催化剂具有优异性能的原因。     

Oligomerization of propene on an alumoxane-grafted MCM-41 host with bis(cyclopentadienyl)zirconium dimethyl (Cp2Zr(CH3)2)

The anchoring of alumoxane, synthesized by the in situ hydrolysis of trimethylaluminum, on the internal pore walls of a mesoporous MCM-41 support generates a highly active and selective host for bis(cyclopentadienyl)zirconium dimethyl (Cp₂Zr(CH₃)₂) in the oligomerization of propene. The regioselective preference of the immobilized metallocene is preserved and a typical Flory–Schulz distribution for the propene oligomers is obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

苯乙烯在MCM-41介孔材料中聚合的研究

The polymerization of styrene in the media of MCM-41 is carried out by means of host-guest polymerization of styrene in MCM-41 mesoporous material with the aim to investigate the effects of interface and confinement of MCM-41 on host-guest interactions. Detailed physical properties of the mesoporous MCM-41 material containing polystyrene is characterized by XRD(X-ray diffraction), FT-IR(Fourier transform infrared), TGA(thermal gravimetric analysis), and nitrogen adsorption-desorption isotherms. We also find a great increase in the glass transition temperature of guest polystyrene influenced by the confined geometry of the host by differential scanning calorimetry(DSC).     

脱硫催化剂(四羧基酞菁铝键合MCM-41)的制备及催化活性研究

为了降低油品中的含硫化合物,合成了四羧基酞菁铝,然后将其键合在MCM-41的表面,通过红外光谱进行了表征,最后以四羧基酞菁铝键合MCM-41作为脱硫催化剂,测定了它去除乙硫醇的催化活性。结果表面:脱硫催化剂(四羧基酞菁铝键合MCM-41)对乙硫醇的去除率可以达到97.8%,而且反应速率快,持续时间长,具有良好的催化活性。     

Adsorption of Bovine Serum Albumin and lysozyme on siliceous MCM-41

The adsorption of Bovine Serum Albumin (BSA) and lysozyme on MCM-41 was studied. In particular, characteristics important to the use of this adsorbent as a chromatographic support for protein separations have been examined. These include the effects of external surface area, solution conditions (pH), and rate of adsorption. Comparative studies were performed on MCM-41 of three pore sizes (24.8 Å, 36 Å, 53.5 Å). It has been shown that differences in external surface area can strongly influence the adsorption capacity. This implies that adsorption on the external surface can be misinterpreted as adsorption in the pores of MCM-41. Thus, high adsorption capacities may not necessarily mean high molecular-sieving capacities. This paper also reports a dependence of protein uptake rates on solution conditions. Calorimetry suggests that under certain solution conditions the adsorption of BSA is a combination of two sequential energetic events. These are postulated to be BSA adsorption followed by reorientation/reconformation of the adsorbed protein on the surface. The slow second step affects the attainment of equilibrium.     

杂原子MCM-41分子筛的合成及对环己烷氧化的研究

用十六烷基三甲基溴化铵为模板剂,水玻璃为硅源,在合成过程分别加入Cr3+、Co2+、Fe3+杂原子,在150℃晶化48h,水热合成了Cr-MCM-41、Co-MCM-41、Fe-MCM-41等杂原子分子筛。考察了时间、温度、催化剂用量、过氧化氢用量及催化剂再生等因素对环己烷氧化反应的影响。最佳反应条件为:温度100℃;环己烷30mmol,Cr-MCM-41为催化剂,用量0 12g;n(H2O2)/n(C6H12)=1;反应时间16h,环己烷的转化率可达28 6%,产物的酮醇摩尔比为1 89。     

Ag-BiVO4／MCM-41制备表征及光催化性能研究

采用浸渍法将Ag-BiVO4固载于MCM-41介孔分子筛上,制备了Ag-BiVOdMCM-41新型复合可见光催化荆,用IR、XRD、SEM等分析测试手段对其进行了结构和性能表征。分析表明：Ag-BiVO4光催化剂为单斜耜结构,复合光催化剂具有较大的比表面积。在λ〉400nm的可见光照射下,以降解亚甲基蓝溶液进行了光催化剂的光催化性能评价。实验结果表明,Ag—BiVO4/MCM-41具有高的可见光催化活性,且具备良好的吸附性能和高的光催化效率。     

脱硫催化剂(2-羧基酞菁钯键合MCM-41)的合成及表征

为了降低空气中逐渐增多的硫化物,首先合成了2-羧基酞菁钯,然后将其键合在MCM-41的表面,运用红外光谱、粉末衍射、扫描隧道显微镜对其进行了表征,最后测定了它的催化活性。结果表明:当MCM-41表面键合2-羧基酞菁钯之后,对噻吩的去处率达到了98%。     

不同碱介质对合成硅基MCM-41的影响

研究了在较高的硅／表面活性剂物质的量比(10)体系中，采用不同的碱介质(氨水、乙二胺、三乙醇胺／NaOH)来合成MCM-41。通过XRD，N2吸附一脱附等表征手段，分析了不同碱介质体系对制备MCM-4l的影响。结果显示。弱碱介质(NH3，EDA)有利于提高MCM-41的热稳定性；而采用混合碱质(三乙醇胺／NaOH)，则可在一定程度上改善MCM-41的水热稳定性，但随着三乙醇胺量的增加，材料的孔径会相应的减小。