一维铂纳米线阵列的模板电沉积及其表征

将一种复合无机介孔膜作为新型的模板应用于一维纳米线阵列的模板合成研究中,通过采用模板恒电位沉积的方法制备出一维铂纳米线阵列,并利用扫描电镜,透射电镜,X射线衍射,能量分布谱,选区电子衍射对该铂纳米线阵列进行了表征。结果表明:通过模板恒电位沉积的方法可以将金属铂组装在复合无机介孔膜内的二氧化硅介孔管中,除去模板后,进而得到长度为10μm的一维多晶铂纳米线(半径为3～4nm)阵列。     

ALKYLATION OF BENZENE USING BATCH AND CONTINUOUS FIXED-BED REACTORS

Alkylation reactions of benzene with propylene using heterogeneous catalysts H⁺-β zeolite, MCM-22, and ZSM-5 were studied for their affinity for cumene production. This work focused on the gas-phase reaction using different crystalline catalysts at several temperatures and amounts of reactants using both batch and continuous fixed-bed reactors. The properties of baseline commercial H⁺-β catalysts versus versions modified with Ga, La, and Pt were studied. Quantitative analysis of product mixture was performed by gas chromatography. For the batch reactor, β-zeolite produced the highest cumene yield and selectivity of 72% and 92%, respectively, at 225°C. At this temperature, a benzene:propylene dilution of 7:1 molar ratio was the optimum. For the continuous system, cumene production is favored at lower space velocities, higher benzene-to-propylene ratio, and temperatures close to 225°C. Ga modification of the H⁺-β zeolite significantly enhanced cumene yield in the continuous fixed-bed reactor at 225°C, from 27% of the unmodified β-zeolite to 36% for the Ga-modified one. The life span of modified β-catalysts was studied in the fixed-bed reactor for the first eight hours of reaction.     

晶态介孔金属氧化物的研究进展

用氧化硅介孔分子筛SBA-15,KIT-6,FDU-12和SBA-16作为模板,在其孔道中生长各种过渡金属氧化物,最终产物是晶态的介孔金属氧化物.这种材料具有广泛的应用前景.电子显微镜是研究这些新型纳米材料不可或缺的手段.本文简述介孔金属氧化物的合成和结构鉴定,以及该研究领域的最新进展.     

From Molecular Clusters to Metal Nanoparticles

Different methods to prepare supported metal nanoparticles of uniform size are discussed. (i) Supported ruthenium particles were generated from Ru and Ru-Fe bimetallic molecular metal carbonyl cluster precursors (MCC). (ii) Gold nanoparticle formation in the supercage of Y zeolite was studied on Au/NaY, Au/HY and Au-Fe/HY system. (iii) Palladium nanoparticles were grown in liquid phase then deposited on an SiO₂ support or they were grown on the support surface in a solid-liquid interfacial layer. The particle size control was more efficient in the latter two cases than in the preparation starting from MCC.     

Multiphasic Acetalization and Alkylation on Organically Modified MSU-X Silica

Mesoporous silicas were functionalized with phenyl groups and were used as solid acid catalysts in acetalization of aldehydes and ketones with ethylene glycol or methanol. It was shown that cyclohexanone as well as aromatic and linear aldehydes could be converted to the corresponding dimethylacetals in high conversion and selectivity over the catalyst. They also performed well in the isopropylation reactions of naphthalene with isopropanol.     

Dehydrogenation and aromatization of methane under non-oxidizing conditions

The dehydrogenation and aromatization of methane on modified ZSM-5 zeolite catalysts has been studied under non-oxidizing conditions with a fixed bed continuous-flow reactor and with a temperature programmed reactor. The results show that benzene is the only hydrocarbon product of the catalytic conversion of methane at high temperature (973 K). The catalytic activity of ZSM-5 is greatly improved by incorporating a metal cation (Mo or Zn). H₂ and ethene have been directly detected in the products with a mass spectrometer during TPAR. A carbenium ion mechanism for the activation of methane is suggested.     

介孔氧化铝的合成及应用

通过对介孔氧化硅合成工艺的优化与修正可以用来制备介孔氧化铝分子筛。在合成介孔分子筛的前驱物中掺杂其他金属元素而将其引入骨架或将活性组分负载到介孔分子筛的基体上,可以实现对介孔分子筛表面进行表面修饰与改性,以调变分子筛表面的酸催化性能。本文综述了介孔氧化铝合成、改性研究的历史与现状,及在酸催化过程中的应用。     

双峰纳晶介孔TiO2的制备及在染料敏化太阳电池中的应用

采用水热法,以三嵌段共聚物聚氧化乙烯-聚氧化丙烯-聚氧化乙烯(EO20PO70EO20,P123)为模板剂,钛酸四丁酯为前驱体,制备了双峰纳晶介孔TiO2,分别利用X射线衍射(XRD)、比表面积与孔径分析、场发射扫描电子显微镜(SEM)以及透射电子显微镜(TEM)对制备的介孔TiO2的相结构、比表面积、孔径和形貌进行了表征,探讨了P123用量对纳晶TiO2微结构的影响。以双峰纳晶介孔TiO2作为染料敏化太阳电池的光阳极材料组装的太阳电池的光电转化效率达5.18%,与相同条件下以P25作光阳极材料组装的电池效率(4.02%)相比提高了28.85%,初步显示了双峰纳晶介孔TiO2在太阳电池领域中的应用潜力。     

Ag担载介孔Bi2WO6的制备及其太阳光催化性能

采用硬模板法及液相沉淀法制备了介孔Bi2WO6(m-Bi2WO6)光催化剂,通过光还原沉积贵金属的方法制备了银担载的m-Bi2WO6复合纳米粒子(Ag/m-Bi2WO6),并利用氮气吸附脱附、XRD、XPS、DRS等测试技术对样品进行了表征。以RhB染料为目标降解物,考察了样品的光催化活性。结果表明,介孔结构能够提高Bi2WO6光催化剂的光催化性能;担载金属银,使得m-Bi2WO6催化剂的光催化性能得到了提高。