Photoinitiated polymerization in bicontinuous microemulsions: Fluorescence monitoring

The photopolymerization of bicontinuous microemulsions was simultaneously monitored with differential scanning calorimetry and fluorescence. The kinetics and mechanism of the reaction were studied throughout the entire photopolymerization reaction. The role played by the surfactant in the kinetics and morphology was studied. The nature of the surfactant changed the autoacceleration process and final conversion. The behavior was explained as a result of the differences in the interfacial properties. Anionic cetyltrimethylammonium bromide (CTAB) gave rise to a more flexible interfacial film than anionic sodium dodecyl sulfate (SDS), resulting in competition between the intramolecular and intermolecular reactions in the former systems. As cyclization did not contribute to the increase in the degree of crosslinking, SDS photopolymerization gave solids with a more rigid microstructure. Fluorescence methodology was applied to monitor bicontinuous microemulsion polymerization and to reveal the microstructure and morphology development during photopolymerization. The microemulsion composition was designed to prepare nanoporous, crosslinked materials. Even though the nanostructure of the precursor microemulsions was not retained because of phase separation during polymerization, mesoporous solids were obtained. Their morphologies depended on the nature of the surfactant, and membranes with open cells were successfully prepared with CTAB, whereas more complex morphologies resulted with SDS. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5291–5303, 2006     

在H－ZSM－5沸石上甲醇转化为汽油的初始产物分布

在Ｈ－ＺＳＭ－５沸石上甲醇转化为汽油的初始产物分布姜玄珍（浙江大学化学系，杭州３１００２７）Ｒ．Ｆ．Ｈｏｗｅ（新南威尔士大学物理化学系，澳大利亚）关键词Ｈ－ＺＳＭ－５沸石，甲醇转化汽油，产物分布以氢型ＺＳＭ－５沸石作催化剂转化甲醇为汽油（ＭＴＧ），在...     

介孔材料在烯烃环氧化中的催化应用

本文综述了介孔材料在烯烃环氧化反应中的应用,包括材料的制备方法、催化性能以及活性中心的表征。通过硅钛原子的合理匹配可以达到四配位钛的高度分散,从而提高催化活性。硅烷化处理增加材料表面的疏水性,能够大幅度提高活性和选择性。通过多种谱学和分子模拟等手段可表征骨架钛及其配位情况。     

甲酰胺对有序介孔二氧化硅形貌的影响

At room temperature and in acidic solution, ordered mesoporous silicas with particular morphology were synthesized using cetylpyridinium chloride as the template and formamide as the cosolvent. Scanning electron microscope (SEM), small angle X-ray diffraction (SXRD), and nitrogen adsorption techniques were used to characterize the as-synthesized and calcined samples. Results showed that the samples had hexagonal mesostructure analogous to MCM-41 and relatively narrow pore-size distributions (BJH). Besides, BET surface areas of the samples were in the range of 1 000～1 250 m²·g^-1 and high total pore volumes were up to 1.367 cm³·g^-1. Addition of formamide affected obviously mesostructures and the morphology of the mesoporous silica. Furthermore, with the increase of the concentration of formamide, the unit-cell constant decreased and particle shape changed from gyroids to fibers.     

立方介孔相含钇氧化硅的合成与表征

以低浓度的十六烷基三甲基溴化铵为结构导向剂,在碱性条件下通过水热法合成了具有立方结构的含钇Y MCM 48介孔分子筛材料。XRD测试表明当Y/Si<0.05时可以获得典型的长程有序介孔立方结构相,随Y/Si比的增加,晶胞参数的增大和红外吸收光谱(FTIR)的变化为Y进入介孔分子筛骨架中提供了有力证据。N2吸附-脱附实验给出这种立方介孔材料的BET表面积为1180m2·g-1,BJH平均孔径为3.4nm。紫外 可见漫反射光谱(UV vis)证明钇以一种六配位的形式存在。X射线光电子能谱(XPS)进一步证明钇以三价形式存在于立方介孔分子筛骨架中。     

Influence of hydrogen bonding on the properties of water molecules adsorbed in zeolite frameworks

Three hydrated aluminosilicate frameworks—LiABW, NaNAT, and BaEDI—are partly optimized with the periodic Hartree–Fock CRYSTAL95 code. In particular, we optimized the positions of the adsorbed water molecules including the positions of the framework cations (ABW, NAT) or part of the framework atomic positions (ABW). This allowed us to compare cation–water clusters in the gas and adsorbed states and discuss the influence of hydrogen bonding to the framework oxygen atoms or to the neighbor water molecules on the atomic properties (quadrupole coupling constant, anisotropy of electric field gradient) of the adsorbed water molecules. The LiBIK structure obtained from X‐ray diffraction is also considered to illustrate the hydrogen bonds occurring between adsorbed water molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

一种模拟沸石分子筛扩散反应的Monte Carlo方法

在考虑了沸石分子筛中吸附、脱附、扩散和反应的特点的基础上，发展了一种模拟沸石分子筛中扩菜反应的ＭｏｎｔｅＣａｒｌｏ方法。用Ｌａｎｇｍｕｉｒ吸附等温式验证了该方法的合理性，并证明了轰击频率λ代表了反应物气相压力，而吸附、脱附几率之比即为吸附平衡常数。同时，通过改变轰击频率λ和反应几率Ｐｔ，得到了吸附等温线和有效因子随Ｔｈｉｅｌｅ模数变化的曲线。