环己烯分子氧氧化多相催化剂研究进展

根据催化剂主组分的不同,综述了国内外环己烯分子氧氧化多相催化剂的研究进展;主要介绍了钴系、锰系、铁系及镍系催化剂在环己烯分子氧氧化中的应用及其优缺点.指出负载型纳米金催化剂与传统的钴、锰催化剂相结合制备双活性中心催化剂在环己烯分子氧氧化中有较好的应用前景.     

Nickel-impregnated zirconium-doped mesoporous molecular sieves as catalysts for the hydrogenation and ring-opening of tetralin

Catalysts based on nickel supported on zirconium-doped mesoporous silica, with nickel loadings of 15 and 30 wt.%, have been prepared, characterized and tested in the hydrogenation of tetralin at high hydrogen pressures (6.0 MPa). The zirconium-doped mesoporous silica, used as support, is revealed as appropriate for attaining a high loading of metallic nickel with a suitable degree of dispersion, although the large metallic particles are located on the external surface of the support. These catalysts are very active in the hydrogenation of tetralin at 350 °C, specially that with the highest nickel content, with no deactivation by coke deposition. Concomitantly, the mild acidic nature of these catalysts favor the ring-opening of the tetralin molecules, up to 28% of cracking products at moderate temperatures are detected and the amount of volatile compounds is almost negligible under these experimental conditions.     

Vanadium, niobium and tantalum modified mesoporous molecular sieves as catalysts for propene epoxidation

SBA-3 mesoporous molecular sieves doped with transition metal ions (Fe, V, Nb and Ta) have been applied for selective oxidation of propene towards propylene oxide in the presence of N₂O as an oxidant. The kind and amount of applied modifiers significantly affected the catalytic activity. V/SBA-3 was found to be the most active among the catalyst under study. In spite of relatively high selectivity towards propylene oxide (reaching up to 23%), the main oxidation product was still propionaldehyde. Surprisingly, CO_x was not formed over V, Nb and Ta modified SBA-3 catalysts. Additional modification of V containing samples (V/SBA-3) with iron complexes resulted in the further increase in the catalysts activity for epoxidation reaction. A PO selectivity of about 20% could be achieved at a propylene conversion of 17% over mixed Fe/V/SBA-3 catalytic system.     

Novel mesoporous polyoxometalate hybrid catalysts for heterogeneous oxidation of thioethers

K₆P₂W₁₈O₆₂ and K₁₄[NaP₅W₃₀O₁₁₀] polyoxometalate salts are synthesized and immobilized within MCM-48, SBA-3, SBA-15 and NH₃⁺ functionalized mesoporous silicas. The newly designed hybrid materials are studied as catalysts for oxidation of thioethers. Preyssler complex is found to be a more active catalyst compared to its Dawson analog. Texture and chemical composition of the silica framework is shown to have indispensable effect on oxidation efficiency, stability, and reusability of catalysts. Catalysts with larger pores are proved to be more proper for the oxidation of relatively large thioethers and functionalization improves catalyst's properties.     

分子筛催化合成正丁酸乙酯的研究

分子筛催化剂作为一种化工新材料在近年来得到了快速发展和广泛应用。正丁酸乙酯是一种重要的香料和用途较广泛的化工产品，本实验用硫酸特殊处理过的人造沸石作催化剂，合成了正丁酸乙酯。同时考察了合成条件对正丁酸和无水乙醇酯化反应的影响。适宜的条件为催化剂用量2g，n（正丁酸）：n（无水乙醇）=1：1，5，带水剂环己烷用量为10mL，反应温度为75℃～80℃，反应时间为3h。在此条件下正丁酸的转化率在80％以上。该催化剂可以重复使用。     

酞菁铜/介孔分子筛复合催化剂催化氧化巯基乙醇的研究

采用浸渍法将α-八-(异戊氧基)酞菁铜分别负载在SBA-15和MCM-41介孔分子筛上,制备了CuPc/SBA-15和CuPc/MCM-412种复合催化剂。通过紫外-可见吸收光谱、红外光谱和N2吸附方法对催化剂的结构和组成进行了表征。测试了2种催化剂对巯基乙醇的催化氧化性能,并考察了温度对催化氧化活性的影响。实验结果表明,在pH=11时,CuPc/SBA-15催化氧化巯基乙醇的转化率高于CuPc/MCM-41;随着温度的升高,CuPc/SBA-15对巯基乙醇的转化率逐渐增大,并计算了CuPc/SBA-15催化反应在25℃时的活化能Ea为30.50kJ/mol。     

用富含介孔的硅基材料合成微孔-介孔复合分子筛

以富含介孔的硅基材料为硅源,四乙基氢氧化铵为模板剂,NaAlO2为铝源,调节投料硅铝的摩尔比(n(SiO2)/n(Al2O3)),通过半固相原位合成法,制备了具有不同晶型的微孔-介孔复合分子筛。采用X射线衍射仪分析样品组成,扫描电镜观测样品晶体形态,使用容量吸附分析仪测量样品孔结构。结果表明,所得样品具有微孔-介孔复合结构,在较低硅铝摩尔比条件下(n(SiO2)/n(Al2O3)=20~50),产物主要为β微孔-介孔复合分子筛;硅铝摩尔比较高时(n(SiO2)/n(Al2O3)200),合成产物为ZSM-5微孔-介孔复合分子筛。     

Novel utilization of mesoporous molecular sieves as supports of cobalt catalysts in Fischer–Tropsch synthesis

Mesoporous molecular sieves (MCM-41 and SBA-15) with different pore diameters have been studied as supports of high loading of Co catalysts, and the performances in FT synthesis have been examined with a fixed bed stainless steel reactor at 2.0 MPa for the purpose of efficient production of C₁₀–C₂₀ fraction as the main component of diesel fuel. The method of exchanging template ions in uncalcined MCM-41 with Co²⁺ ions is effective for holding 10–20% Co within the mesopores while keeping the structure regularity of MCM-41 to some extent, compared with the conventional impregnation method using calcined MCM-41. At 523 K, CO conversion and selectivity to C₁₀–C₂₀ hydrocarbons are both higher at larger loading of 20% Co for the exchanged catalysts with pore diameters of 2.7–2.9 nm. When four kinds of 20% Co/SBA-15 with the diameters of 3.5–13 nm, prepared by the impregnation method using an ethanol solution of Co acetate, are used in FT synthesis at 523 K, the catalyst with the diameter of 8.3 nm shows the largest CO conversion, which is higher than those over MCM-41 supported Co catalysts. At a lower temperature of 503 K, however, the acetate-derived Co is almost inactive. In contrast, the use of Co nitrate alone or an equimolar mixture of the acetate and nitrate as Co precursor drastically enhances the reaction rate and consequently provides high space–time yield (260–270 g C/kg_cat h) of C₁₀–C₂₀ hydrocarbons. The X-ray diffraction and temperature-programmed reduction measurements show that the dependency of the catalytic performance of 20% Co/SBA-15 on its precursor originates probably from the differences in not only the reducibility of the calcined catalyst but also the dispersion of metallic Co. Catalyst characterization after FT synthesis strongly suggests the high stability of the most effective Co/SBA-15 in the dispersion and reducibility of the oxide species and in the mesoporous structure.     

Titanium substituted hexagonal mesoporous aluminophosphates: Highly efficient and selective heterogeneous catalysts for the oxidation of phenols at room temperature

A remarkable para-selectivity was achieved, for the first time, for the oxidation of phenol over novel titanium substituted hexagonal mesoporous aluminophosphate molecular sieves at room temperature, and that the catalysts also showed excellent activity for alkyl substituted phenols.     

Aerosol-assisted synthesis of hierarchical porous titanosilicate molecular sieve as catalysts for cyclohexene epoxidation

Hierarchical titanosilicate composites (HTS) have been synthesized by an aerosol spray method, by which TS-1 nanoparticles were assembled with cetyl trimethyl ammonium bromide and tetraethylorthosilicate/tetra-n-butyl titanate to form a hierarchical porous composites with a core–shell structure. The structure, porosity, morphology and composition of the materials were characterized by X-ray diffraction, nitrogen adsorption isotherm, Raman spectroscopy, electron microscopy and X-ray fluorescence spectroscopy. The hierarchical porous molecular sieve combines the advantages of TS-1 and Ti-KIT-1, and shows high activity and selectivity to epoxide in cyclohexene epoxidation with H₂O₂. The yield of cyclohexene oxide on HTS is much higher than those on TS-1 and Ti-KIT-1. The selectivities to cyclohexene oxide and 1,2-cyclohexanediol can be adjusted by varying the titanium contents of the HTS samples.     

Copper-cationic salphen catalysts for the oxidation of cyclohexene by oxygen

The modified copper-cationic salphen catalysts were synthesized and used in the allylic oxidation of cyclohexene to 2-cyclohexen-1-ol and 2-cyclohexen-1-one with oxygen under mild conditions. Compared with their unmodified counterpart, the catalytic activities of modified catalysts are improved. The type of counteranion could affect the reactivity of catalyst, which offers an opportunity to improve the catalysts via changing counteranions to optimize the selectivity. The cation–anion interaction can be adjusted by different solvents, which in turn influences the catalyst reactivity. Furthermore, these novel catalysts can be reused without sacrificing the activity.     

以离子液体为模板剂合成MCM-41介孔分子筛

以离子液体1-十六烷基-3-甲基溴代咪唑为模板剂,合成介孔分子筛MCM-41。考察了不同硅源[、C16mim]Br/SiO2配比、pH值、晶化时间等条件对合成MCM-41的影响。采用XRD和低温氮吸附对产物进行表征,结果表明该方法合成的样品具有较大比表面积和规整介孔孔道结构。     

Metal complexes of 2-methylimidazole encapsulated in zeolite-Y as efficient and reusable catalysts for oxidation of phenol and benzyl alcohol

Copper(II), ruthenium(III) and zinc(II) complexes of 2-methylimidazole (2-MeImzlH) encapsulated in the supercages of zeolite-Y have been synthesized and characterized by various physicochemical measurements. The catalytic potential of these complexes were tested for the oxidation of phenol and benzyl alcohol using 30 % H₂O₂ as an oxidant. Various parameters, such as concentration of oxidant and catalyst, reaction time, temperature of the reaction, volume of solvent and type of solvents have been optimized to obtain the maximum transformation of phenol to catechol and hydroquinone. The catalytic activity of zeolite encapsulated complexes followed the order: [Cu(2-MeImzlH)]-Y (72.5 %) > [Ru(2-MeImzlH)]-Y (57.8 %) > [Zn(2-MeImzlH)]-Y (43.2 %) after 5 h of reaction time. Oxidation of benzyl alcohol catalyzed by these encapsulated complexes gave only benzaldehyde as the product. The zeolite-encapsulated complexes could be easily separated after the reaction and reused. The neat complexes gave low conversions as compared to the encapsulated catalysts and decomposed. The catalytic activity of zeolite encapsulated complexes was found to be better than their respective non-encapsulated complexes and metal exchanged zeolites.     

沸石分子筛封装纳米金属催化材料的研究进展

综述了近几年国内外沸石分子筛封装纳米金属催化材料的研究进展。重点介绍了在沸石晶体中固定活性金属位置,有效地将纳米粒子的高活性和沸石选择性、稳定性的优点结合,在一系列反应中提高催化性能。在沸石晶体中固定独立的金属位点、金属团簇的合成策略、催化性能和机理研究等。特别是金属纳米粒子被高比表面积沸石分子筛封装后解决了金属纳米粒子的聚集和烧结问题。并介绍了沸石分子筛封装纳米金属催化材料目前的局限性和未来的发展前景。     

沸石分子筛封装纳米金属催化材料的研究进展

综述了近几年国内外沸石分子筛封装纳米金属催化材料的研究进展。重点介绍了在沸石晶体中固定活性金属位置,有效地将纳米粒子的高活性和沸石选择性、稳定性的优点结合,在一系列反应中提高催化性能。在沸石晶体中固定独立的金属位点、金属团簇的合成策略、催化性能和机理研究等。特别是金属纳米粒子被高比表面积沸石分子筛封装后解决了金属纳米粒子的聚集和烧结问题。并介绍了沸石分子筛封装纳米金属催化材料目前的局限性和未来的发展前景。     

新型中孔分子筛研究进展

中孔分子筛已成为人们研究的一个重要课题。目前，人们用不同的表面活性剂，根据不同的组装路线合成出了M41S、SBA-n系列、HMS、KIT-1、MSU-x、MSU-V、MSU-G、MSU-S和 MSU-H等中孔分子筛。对目前的中孔分子筛的研究情况进行了综述，分析了合成路线及合成所用的不同的表面活性剂，对今后的研究方向作了展望。     

Catalytic behavior of vanadium substituted mesoporous molecular sieves

A series of V-MCM-41 samples with different pore sizes has been systematically investigated with both gas and liquid phase reactions. Methanol oxidation has been performed in the gas phase on these catalysts. Turnover frequencies are normalized by oxygen uptake measured under reaction conditions. A strong effect of pore size on the catalytic activity was observed in the form of a “volcano curve” and may be correlated with a variation in the local bond angle of Si–O–V. Considering this effect, the catalytic activity may be ‘tuned' to maximum by varying the pore size. As expected, the same effect was observed in the liquid phase oxidation of cyclohexene. In order to interpret the pore size effect, the reaction rates of both the gas phase and liquid phase oxidation were then correlated with the variation of edge energies of V K-edge XANES on these MCM-41 catalysts. Additional reactions were performed in the liquid phase to compare the activity of V-MCM-41 with that of crystalline vanadium and titanium silicalite zeolites. The possible causes of the difference in the catalytic behaviors of these materials is also discussed.     

Redox behavior and selective oxidation properties of mesoporous titano- and zirconosilicate MCM-41 molecular sieves

Mesoporous titano- and zirconosilicate molecular sieves, Ti-MCM-41 and Zr-MCM-41, respectively, with Si/M ratios in the range from 11 to 96 (M=Ti or Zr), have been synthesized by the hydrothermal method and characterized by XRD, XRF, N₂ adsorption and diffusive reflectance UV–Vis (DRUV–Vis), FT-IR and electron spin resonance (ESR) spectroscopic techniques. The redox behavior and selective oxidation properties of these materials have been investigated. ESR of samples reduced with LiAlH₄ (298 K) and H₂ (673–873 K) reveals two types of metal ion species: species I^′ located inside the pore walls and species I^′′ located at the pore surface. The reduced species I^′′ are highly reactive towards oxygen and form M(O₂^−·) radicals. The M(O₂^−·) radicals were also observed when the samples were reacted with aqueous H₂O₂ or tert-butylhydroperoxide (TBHP). ESR studies reveal that Ti-MCM-41 is easier to reduce and reoxidize than Zr-MCM-41. The DRUV–Vis spectra are consistent with a monoatomic dispersion of the metal ions. In the samples with high metal loading the presence of a nanocrystalline metal oxide phase cannot be ruled out. Both Ti-MCM-41 and Zr-MCM-41 catalyze the hydroxylation of 1-naphthol with aqueous H₂O₂ and the epoxidation of norbornylene with TBHP.     

SBA-15锚定的钌杂多酸催化剂的合成及其催化正十六烷氧化

利用(3-氨丙基)三乙氧基硅烷(apts)将钌金属杂多酸[X₂W₂₀O₇₀(RuY)₂]^10-(其中,X为锑或铋,Y为苯或对异丙基苯甲烷)固定在介孔的SBA-15上可得到一系列性能优良的SBA-15锚定的钌杂多酸催化剂。采用XRD、N₂吸附-脱附实验和FT-IR红外光谱对此类催化剂进行表征,并检测其对正十六烷氧化的催化性能。结果表明,以空气为氧化剂,在无任何溶剂的条件下,该锚定的钌杂多酸催化剂遵循传统的自由基自氧化机理,将正十六烷烃氧化成各种醇类和酮类,显示出优良的催化性能。因此,这类多相催化剂对环境友好的烷烃氧化反应具有较高的应用价值。