CMC和CTAB双模板法合成具有稳定结构的MCM-41中孔分子筛

以羧甲基纤维素和十六烷基三甲基溴化铵为双模板,制备出了具有更高稳定性并且具有高度有序二维六方结构的MCM-41介孔分子筛.透射电镜和X射线衍射结果表明,以双模板制备的MCM-41介孔分子筛具有高度有序的二维六方(p6mm)孔道结构.此外,以双模板制备的MCM-41介孔分子筛焙烧前后的X射线衍射结果表明,在焙烧过程中其晶胞收缩比例为3.1%.与以纯表面活性剂为模版制备的MCM-41介孔分子筛(晶胞收缩比例为9.7%)相比,双模板制备的MCM-41介孔分子筛具有更高的稳定性能. MCM-41介孔分子筛稳定性能的提高可能是由于在硅物种、表面活性剂以及羧甲基纤维素在自组装过程中,羧甲基纤维素表面丰富的羟基与硅物种Si-(OH)x的相互作用促进了Si-(OH)x的缩聚.     

KIT-1介孔分子筛的化学修饰及吸附性能

介孔分子筛MCM-41具有较大、可调的孔径和较高的比表面积，其骨架组成具有较强的可调变性．为该材料的应用提供了很大的空间。但全硅MCM-41分子筛在潮湿空气中，即使在室温条件下也会发生水解反应，使其介孔结构遭到破坏。前人已针对MCM-41分子筛稳定性不足的问题相继合成了稳定性较高的介孔分子筛KIT-1,     

负载Co介孔分子筛催化热解乙醇制备纳米碳管

以硅酸钠为原料,CTAB为模板剂,水热法合成MCM-41介孔分子筛,采用浸渍法制备负载钴的介孔分子筛(Co/MCM-41),并将其作为催化剂,CVD法热解无水乙醇制备CNTs.利用XRD、TEM、比表面积和孔径分布测定和Raman光谱等方法对所合成的介孔分子筛和纳米碳管进行了表征.结果表明:所制备的Co/MCM-41样品具有典型的MCM-41的介孔结构;当热解反应温度为750℃下所制备出的纳米碳管的品质最好.     

介孔分子筛MCM-41的水热稳定性

介孔分子筛MCM-41在催化、吸附分离以及化学组装制备先进材料等方面具有潜在的巨大应用价值,但MCM-41的低水热稳定性使其在催化研究领域中的应用受到了极大的限制。因此,提高介孔分子筛的水热稳定性具有十分重要的科研和实际应用意义。笔者对介孔分子筛MCM-41低水热稳定性的原因作了简要分析,并系统地介绍了近几年来在提高介孔分子筛水热稳定性方面的研究工作。     

席夫碱修饰的介孔分子筛MCM-41催化有机反应的研究进展

介孔分子筛MCM-41在催化、吸附和分离等方面具有优异的性能,而席夫碱在催化、生物活性和医药等方面也表现出很好的活性,席夫碱配合物修饰的介孔分子筛MCM-41催化有机反应的应用已成为有机化学研究的热点之一.针对近年来席夫碱修饰的介孔分子筛MCM-41在烯烃的氧化、醇的氧化、Suzuki偶联、不对称催化及其它反应中的应用研究进行了综述.     

微介孔复合分子筛合成及其在汽车冷启动尾气控制中的应用

分别采用稀溶液和浓溶液双模板剂两步水热合成法,以二氧化硅微硅粉和铝酸钠为硅源和铝源,第一步获得β分子筛晶种,第二步以β分子筛晶种为结构单元组装形成兼具MCM-41分子筛和β分子筛结构特点的复合型分子筛β/M(其中β是指β分子筛,M是指MCM-41介孔分子筛).采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、氮气吸附(BET)和高分辨透射电镜(HRTEM)对样品的物相结构和微观形貌进行了表征,并对复合分子筛的合成过程进行了分析.结果表明:复合分子筛β/M的形成是微孔β结构和介孔MCM-41结构的竞争生长过程,β分子筛晶种的晶化时间和晶粒度大小对β/M复合分子筛的结构有重要影响.此外,我们以甲苯为探针分子,比较研究了三类分子筛β/M、MCM-41和β的原样以及经高温水热处理后样品的吸附性能,结果表明:β/M复合分子筛的热稳定性优于介孔分子筛MCM-41,其甲苯吸附容量比MCM-41和β分子筛的高,其中以浓溶液法合成的复合分子筛吸附容量最高.     

杂原子介孔MCM-41分子筛的制备及其对含喹啉模拟柴油的吸附脱氮性能

制备了介孔MCM-41分子筛和三种杂原子(Zn、Ba和Ce)介孔MCM-41分子筛,通过X射线衍射(XRD)、红外光谱(FT-IR)、低温N_2吸附-脱附等手段对其进行表征,研究了几种介孔分子筛对氮含量为1732μg/g含喹啉模拟柴油的吸附脱氮性能。结果表明,所制备的几种分子筛均具有典型的介孔结构,且杂原子已进入到分子筛骨架中。利用Materials Studio软件构建介孔分子筛模型,模拟的XRD谱图与实验结果基本相符;进一步模拟了喹啉分子在杂原子介孔分子筛团簇上的吸附,计算了吸附能及被吸附分子和吸附中心的距离(d_((N-M)))。几种分子筛的吸附脱氮性能顺序依次为Zn-MCM-41 Ce-MCM-41 Ba-MCM-41 MCM-41;Zn-MCM-41的吸附性能最好,吸附能最大,吸附分子和吸附中心的距离d_((N-M))最小。吸附时间对杂原子介孔分子筛的吸附脱氮性能具有较大影响,而吸附温度的影响相对较小;Zn-MCM-41、Ba-MCM-41和Ce-MCM-41分子筛的最佳吸附时间分别为40、10和30 min,最佳吸附温度分别为40、30和40℃。     

负载型铜系分子筛催化剂在苯酚羟基化反应中的应用

以介孔分子筛MCM-41、MCM-48和AIMCM-41以及微孔分子筛Naβ和MOR为载体,分别采用有机官能团化法和分步水热合成法制备了系列负载型催化剂,考察了其在苯酚羟基化反应中的活性;得到了不同载体类型、不同负载方法及不同助剂与反应活性的对应关系．结果表明：以微孔分子筛为载体的催化剂对副产物有明显的抑制作用．介孔分子筛AIMCM-41,MCM-41,MCM--48为载体时,催化剂在苯酚羟基化反应中的活性顺序为AIMCM-41〉MCM-48〉MCM-41,助剂镧和钴的引入可以有效抑制副产物的产生．     

氨水介质中含Ti的MCM-41介孔分子筛的合成

 在氨水介质中采用TiCl3和正硅酸乙酯合成了含Ti量不同的MCM-41介孔分子筛. 该方法可避免使用昂贵的辅助模板剂,也不需要加入醇来调节水解速度,因而合成过程相对简单、易于控制. 采用XRD和N2吸附-脱附等技术对介孔分子筛的结构进行了表征. 结果表明,合成的MCM-41介孔分子筛的六方介孔有序性好,结晶度高. UV-Vis光谱表明,Ti-MCM-41在200～300 nm间出现了四个清晰可辨的吸收峰,说明Ti原子以多种状态存在于介孔分子筛骨架中.     

Hβ/MCM-41复合分子筛催化剂上苯甲醚与乙酸酐酰化反应研究

以β沸石为硅源,制备了不同硅铝比的Hβ/MCM-41复合分子筛,考察了该复合分子筛对苯甲醚与乙酸酐酰化反应的催化效果,并与介孔MCM-41、微孔Hβ分子筛的催化效果进行了比较,研究了分子筛硅铝比、酸性及孔道结构对酰化反应催化性能的影响。结果表明,对于苯甲醚和乙酸酐酰化反应,Hβ/MCM-41复合分子筛具有较好的催化稳定性,反应过程中的积炭量较少,积炭的碳氢比较低。该复合分子筛不仅具有微孔沸石的强酸性,而且具有较大孔径的介孔,产物分子能及时从孔道中扩散出来,催化活性位不易中毒失活。     

Metastability of MCM-41 and Al-MCM-41

The apparent stability of MCM-41 and Al-MCM-41 in water was appraised in a series of solubility experiments. MCM-41 is a siliceous, mesoporous material of hexagonal symmetry and exceptionally high surface area first synthesized in 1992. The dissolution experiments were carried out at several solid/water ratios: 1/200, 1/100, and 1/75. Results indicated that MCM-41 and Al-MCM-41 are more soluble than amorphous silica at ambient temperatures. Using standard thermodynamic data, a minimum Gibbs free energy of formation of -847.9 kJ/mol for MCM-41 was calculated compared to -848.85 kJ/mol for amorphous silica and -856.3 kJ/mol for quartz. X-ray diffraction (XRD) analyses of recovered solids indicated a progressive loss of crystallinity in MCM-41 and Al-MCM-41 over the 79 day dissolution experiment. BET nitrogen surface area analyses of recovered solids revealed no appreciable change in the surface area of either material after 79 days of reaction in water. Field emission scanning electron microscope (SEM) images taken of the 79 day MCM-41 sample showed some degradation of the initial structure-fine, worm-like particles.     

Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Br?nsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.     

Deactivation of silica supported Pd catalysts during liquid-phase hydrogenation

Summary Large pore MCM-41 was found to provide a better stabilization of Pd particles than amorphous SiO₂ during liquid phase hydrogenation. Pd/large pore MCM-41 exhibited higher hydrogenation activities as well as lower amount of metal loss by Pd leaching.     

高纯度中孔分子筛MCM-41的合成与表征

用不同pH值的混合物制备了不同孔径的全硅MCM-41和不同金属离子取代的M-MCM-41(M=Al,Mn,Fe和V)分子筛.这些试样均呈现MCM-41的X射线粉末衍射特征峰和Ⅳ型氮气吸附等温线,但混有不同含量的无定形氧化硅.样品中MCM-41晶体的含量与溶胶的pH值和所用表面活性剂的碳链链长有关.骨架硅的金属离子取代降低了MCM-41的有序度,并且(100)面衍射峰强度从Al到V依次减弱.     

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.     

苯乙酮氢转移反应中ZrO2/MCM-41和ZrO2/AC的催化性能对比

采用浸渍法制备了分别以活性炭(AC)和全硅MCM-41介孔分子筛负载的ZrO2催化剂,并对其进行了XRD、氮气吸附-脱附、X射线光电子能谱、差热-热重分析和吡啶吸附原位红外光谱等表征,考察了其在以异丙醇为氢源还原苯乙酮为α-苯乙醇的Meerwein-Ponndorf-Verley(MPV)反应中的催化活性,并与水合ZrO2进行对比.研究了载体对催化剂活性的影响.结果表明,ZrO2经MCM-41负载后,与载体发生强相互作用,可能形成Si—O—Zr键,ZrO2在载体表面呈高分散的无定形态,Zr—OH数目显著增加,L酸性增强,并形成B酸中心,使催化剂活性显著高于水合ZrO2;ZrO2负载在AC上后,与载体未发生强相互作用,ZrO2在载体表面未呈高分散状态,增加的Zr—OH数目相对较少,L酸性较弱,未形成B酸中心,催化活性未明显增加,但在较高焙烧温度(400～600℃)下,其仍能保持稳定的催化活性,这可归因于ZrO2/AC中AC孔道疏通及AC石墨层对苯乙酮上苯环的吸附作用,使活性位附近的反应底物浓度显著增大.     

A novel method for synthesis of mesoporous ZSM-5 from iron ore tailings

Mesoporous ZSM-5 was prepared from iron ore tailings (IOT) using a two-step process. Mesoporous MCM-41 was first synthesized using cetyltrimethylammonium bromide (CTAB) as mesoporous template and IOT as silica source. The CTAB in the as-synthesized MCM-41 was used as the mesoporogen to produce the mesoporous ZSM-5, by recrystallizing the amorphous walls of MCM-41 with tetrapropylammonium bromide (TPABr) as the structure-directing agent via solid-phase conversion. To evaluate the textural properties of mesoporous ZSM-5, the as-synthesized samples were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ²⁹Si, ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy, and nitrogen adsorption. The results show that phase separation between the surfactant and zeolite crystals was avoided in the solid-phase conversion process, which transforms the as-synthesized MCM-41 to mesoporous zeolite. Therefore, the synthetic route presented herein provides a novel method for the synthesis of mesoporous ZSM-5 from IOT.

     

杂原子介孔Co-MCM-41分子筛的制备及其吸附脱氮性能

采用水热法合成了介孔MCM-41和Co-MCM-41分子筛,并利用XRD、FT-IR、低温N₂吸附-脱附和NH₃-TPD等方法对合成的分子筛进行了表征。考察了晶化时间、晶化温度、陈化时间对合成介孔Co-MCM-41分子筛的影响,确定较适宜的合成条件为陈化时间1 h,晶化温度110 ℃,晶化时间2 d。XRD 和FT-IR表征结果说明,Co原子已经进入MCM-41的骨架。MCM-41和Co-MCM-41的平均孔径均为2.82 nm,BET比表面积分别为986.42和 637.69 m²/g,孔容分别为0.762 1和0.537 2 m³/g。NH₃-TPD的表征结果表明,MCM-41和Co-MCM-41的酸性都较弱,但Co-MCM-41的酸性明显强于MCM-41。在此基础上,利用合成的MCM-41和Co-MCM-41吸附脱除氮含量为1 737.35 μg/g的模拟燃料中的喹啉。喹啉分子尺寸的模拟结果为0.711 6 nm × 0.500 2 nm,说明其可以很容易地进入MCM-41和Co-MCM-41的介孔孔道中。Co-MCM-41分子筛的氮脱除率明显高于MCM-41,这是由于其较强的酸性及与喹啉之间的化学吸附,而且,Co-MCM-41吸附脱氮具有较好的再生性能。     

改性Ni-B合金的制备及其催化糠醛加氢性能的研究

非晶态合金是一类介于晶态和无定形物质之间的特殊材料,其组成元素之间以金属键相连并在几个晶格常数范围内保持短程有序而长程无序,这种独特结构使其具有优良的催化性能,并大多被用于加氢反应例如,苯加氢制环己烷[1,2],硝基苯加氢制苯胺[3,4],环戊二烯选择加氢[5],腈类加氢[6,     

有机官能团化介孔分子筛固载铑膦配合物的制备及其对己烯-1氢甲酰化的催化性能

 制备了表面有机官能团化的MCM-41和MCM-48介孔分子筛以及SiO2等载体固载铑膦配合物催化剂,考察了所制备催化剂对液相己烯-1氢甲酰化的催化性能,并用X射线衍射、BET、红外光谱和原子吸收光谱等技术对载体和催化剂的组成和结构进行了表征. 结果表明,固载化铑膦配合物对烯烃氢甲酰化的催化性能与有机官能团的种类及载体的结构有关; 固载于含胺基和腈基有机官能团化介孔分子筛载体的铑膦配合物表现出较高的催化活性和稳定性.