Synthesis and thermodynamic properties of a metal-organic framework: [LaCu6(μ-OH)3(Gly)6im6](ClO4)6

A metal-organic complex, which has the potential property of absorbing gases, [LaCu₆(μ-OH)₃(Gly)₆im₆](ClO₄)₆ was synthesized through the self-assembly of La³⁺, Cu²⁺, glycine (Gly) and imidazole (Im) in aqueous solution and characterized by IR, element analysis and powder XRD. The molar heat capacity, C_p,m, was measured from T = 80 to 390 K with an automated adiabatic calorimeter. The thermodynamic functions [H_T − H_298.15] and [S_T − S_298.15] were derived from the heat capacity data with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimetry (DSC).     

烯烃在HZSM-5分子筛上原位芳构化反应的研究

烯烃在ZSM-5分子筛上转化成芳烃的反应是一个非常复杂的反应,既包括聚合裂解反应,又包括氢转移、脱氢环化反应,同时也包括烷基转移和脱烷基等反应,对于这一复杂反应的机理研究较少.Vedrine等人[1]认为烯烃首先在酸性位上通过氢转移生成戊二烯正碳离子,接着环化以及扩环反应生成     

Physicochemical properties of Ti-grafted SBA-15

Partial oxidation of n-heptane to syngas at 400–450°C was investigated over Rh and Rh-Ni based catalysts. The Rh/-Al₂O₃ catalyst exhibited much better catalytic activity than the Rh-Ni/-Al₂O₃ catalyst. A combination of the Rh-based catalyst with the WGS reaction catalyst (Fe₃O₄—Cr₂O₃) increases the hydrogen selectivity but has no distinct effect on shifting the balance of the partial oxidation of n-heptane.This revised version was published online in December 2005 with corrections to the Cover Date.     

Interaction of the important species HNO and HFSO2 in the atmosphere: Theoretical study of the N?H and S?H blue‐shifted hydrogen bonds

Ab initio molecular orbital and density functional theory (DFT) in conjunction with different basis sets calculations were performed to study the N? H…O and S? H…O blue‐shifted H‐bonds in the HNO…HFSO₂ complex. The geometric structures, vibrational frequencies, and interaction energies were calculated by both standard and CP‐corrected methods. Natural bond orbital (NBO) analysis was used to investigate the origin of blue‐shifted H‐bonds, showing that the decrease in the σ*(N? H) and σ*(S? H) is due to the electron density redistribution effect. The structure reorganization effect on the blue‐shifted hydrogen bonds was discussed in detail. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

负载型双噁唑啉催化剂上的不对称Diels-Alder反应

 分别以乙烷桥键磺酸官能化的有机-无机杂化介孔材料、十二钨磷酸铯、活化硅胶以及SBA-15为载体,通过非共价键作用制备了负载型双噁唑啉催化剂,并将该催化剂用于催化3-((E)-2-丁烯酰基)-1,3-噁唑啉-2-酮和环戊二烯的不对称Diels-Alder反应. 研究表明,催化剂的性能取决于载体本身以及载体表面阴离子的性质. 以SBA-15为载体时产物的对映体选择性较低,可归因于载体表面较低的羟基浓度.     

A preliminary study on fabrication of nanoscale fibrous chitosan membranes in situ by biospecific degradation

A new approach for in situ fabrication of nanoscale fibrous chitosan membrane by biospecific degradation under physiological situation was studied. The chitosan binary blend membranes were fabricated by solvent casting of chitosan solution containing highly deacetylated chitosan (HDC) and moderately deacetylated chitosan (MDC) with different ratio. The biodegradation process was performed in PBS (pH 7.4) containing lysozyme at the temperature of 37 °C. Experimental results from weight loss, reducing sugar in surrounding media, FT-IR, X-ray diffraction, gel permeation chromatography (GPC) and SEM throughout the study showed that the biospecific degradation by lysozyme had removed MDC component selectively. When the ratio of MDC in the binary blend membranes amounted to 0.5, nanoscale domains of HDC and MDC were obtained, and thus a nanoscale fibrous structure was fabricated after biospecific degradation of MDC. This nanofibrous structure and the biospecific degradation of chitosan membranes can have potential advantages and interesting implications in tissue engineering and drug delivery.     

后处理法合成高热稳定性的中孔Ti-P-Al材料

 以阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)为模板剂,采用水热合成法制备了中孔氧化钛原粉,再采用磷酸和氯化铝溶液依次对中孔氧化钛原粉进行后处理,得到了具有高热稳定性的中孔Ti-P-Al材料. 通过粉末X射线衍射、透射电子显微镜和氮物理吸附等方法对样品进行了表征. 结果表明,反应凝胶组成对样品的中孔结构有较大的影响,当反应凝胶配比为Ti(SO4)2∶CTAB∶H2O=1∶0.54∶430, 温度为363 K, 处理时间为10～20 min时,所得的TiO2原粉具有较规整的中孔结构. 此样品经过0.25 mol/L的磷酸处理后有序性有较大程度的提高. 将磷酸处理过的样品进一步用氯化铝溶液处理,得到了中孔结构的Ti-P-Al材料,此材料经过873 K焙烧后仍具有典型的中孔特征,其比表面积为 382 m2/g, 孔径为3.13 nm.     

Thermodynamic properties of hydrated sodium l-threonate Na(C4H7O5)·H2O(s)

Low-temperature heat capacities of the compound Na(C₄H₇O₅)·H₂O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are Δ_transH_m = (5.75 ± 0.01) kJ mol⁻¹ and Δ_transS_m = (18.47 ± 0.02) J K⁻¹ mol⁻¹. The enthalpy and entropy of the dehydration are Δ_dH_m = (15.35 ± 0.03) kJ mol⁻¹ and Δ_dS_m = (41.35 ± 0.08) J K⁻¹ mol⁻¹. Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (III) have been fitted to polynomial equations.     

弛豫理论对离子交换毛细管电色谱中峰压缩现象的研究

 在毛细管电色谱中,由于溶质在输运过程中所具有的电性质,常会产生一些特殊的现象。这些现象,如离子交换毛细管电色谱中产生超高柱效峰的现象,已经不能用一般的色谱理论加以解释。基于弛豫理论所建立的基本模型,在考虑溶质在两相中皆有可能发生正、反向迁移的情况下,得到了流出曲线一阶原点矩和二阶中心矩的理论表达式,并通过对溶质在两相中电扩散速率与电泳速率、电渗流速率关系的分析结果证实:溶质在固定相表面的电扩散行为可以使其保留变弱,出峰加快;而这种电扩散导致的超常柱效峰的出现具有不稳定性,只有在多方面因素综合影响匹配的情况下才可能出现。     

PPh3催化Mannich反应机理的密度泛函研究

通过密度泛函理论研究了PPh3催化苯胺、苯甲醛和乙酰乙酸乙酯三组分Mannich反应的机理.计算结果表明该机理主要分3个步骤进行:PPh3催化乙酰乙酸乙酯发生酮式-烯醇式互变异构得到烯醇;烯醇辅助苯胺和苯甲醛缩合并脱水生成亚胺;亚胺和烯醇通过加成反应生成β-氨基羰基化合物.通过详细的机理研究,发现烯醇从亚胺的背面进攻其亲电C原子的过渡态的相对能量更低,容易得到反式的产物,对实验观察到的非对映选择性进行了合理的解释.