吡啶氮桥联双环三唑鎓盐的合成及其在催化苯偶姻缩合、酯交换反应中的应用

合成了12个吡啶氮桥联的双环三唑鎓盐2a～2l卡宾催化剂前体,用于催化苯偶姻缩合反应和酯交换反应,考察了反应条件对催化反应的影响,并与其它三唑鎓盐的催化活性进行了比较.结果表明,在较低催化剂用量下,催化剂2c表现出优良的催化活性,分离产率最高分别达到98%和93%.     

超声作用下KF/CaO催化酯交换反应制备生物柴油

等体积浸渍法制备了KF/CaO固体碱催化剂,用于催化大豆油与甲醇酯交换反应制备生物柴油,在反应体系中引入超声作为辅助条件。研究表明,KF/CaO催化活性高。在超声的辅助作用下,酯交换反应速率加快,生物柴油的收率提高。实验考察了反应条件对产品中脂肪酸甲酯含量的影响。醇油摩尔比为12∶1,反应温度65℃,催化剂与大豆油的质量比为3%,反应1 h,超声频率20 kHz,超声声强1.01 W/cm2,在此反应条件下,产品中脂肪酸甲酯的质量分数达到99.6%。     

TiO2／Al2O3负载量对气相酯交换合成碳酸甲丙酯的影响

采用XRD、N2 physical adsorption、XPS、NH3-TPD和吡啶吸附IR等技术,对碳酸二甲酯和丙醇气固相合成碳酸甲丙酯的TiO2/Al2O3催化剂进行了表征.实验结果表明,TiO2/Al2O3表面的Lewis酸中心是反应的催化活性位,酸性主要来源于Al2O3,TiO2起修饰作用,有利于选择性生成碳酸甲丙酯.随着Ti负载量的增加,TiO2在Al2O3表面由高度分散状态向晶态转变,其比表面积逐渐降低,但是TiO2/Al2O3的表面酸性质没有受到显著影响,L酸量先是增加,而后略有下降.当Ti负载量为5%时,DMC的转化率及MPC的选择性分别达到54.3%和88.1%.     

环戊二烯掺杂乙烷桥联有序介孔材料的制备、表征及应用

 以单硅酯 (2-(环戊基-1,3-二烯基) 乙基) 三乙氧基硅烷 (TEECp) 和含有亚乙基桥键的硅酯 1,2-二 (三乙氧基硅基) 乙烷为硅源, 以三嵌段共聚物 P123 为模板剂, 通过调节 TEECp 预水解时间, 采用共聚法合成了环戊二烯掺杂乙烷桥联材料 (Cp-PMO), 并采用小角 X 射线衍射、N2 物理吸附、透射电镜、红外光谱和热重等技术对样品进行了表征. 结果表明, 环戊二烯基被成功引入到乙烷桥联材料中, 所得 Cp-PMO 样品具有高度有序的二维六方介孔孔道, 热稳定性较高; 随着材料中环戊二烯含量的增加, 其有序性降低, 孔径、比表面积和孔体积均有所减小, 孔壁逐渐增厚. 在乙酸乙酯与正丁醇的酯交换反应中, Cp-PMO 样品表现出较高的催化活性. 当该样品中环戊二烯含量为 30% 时, 乙酸乙酯转化率和乙酸丁酯收率分别可达 19.3% 和 10.6%.     

A phosphorus‐containing thermotropic liquid crystalline copolyester with low mesophase temperature and high flame retardance

A novel phosphorus‐containing thermotropic liquid crystalline copolyester with flexible spacers (P‐TLCP‐FS) was synthesized by melt transesterification from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), ethylene glycol, and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (AODOPB). The chemical structure and properties of the obtained P‐TLCP‐FS were characterized by Fourier‐transform infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance spectroscopy (¹H‐NMR), inherent viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TGA), polarizing light microscopy (PLM), and X‐ray diffraction (XRD) analysis. P‐TLCP‐FS had inherent viscosities of 0.92–1.12 dL/g and exhibited low and wide mesophase temperatures, ranging from 185 to 330 °C, which can match with the processing temperatures of most conventional polymers and high flame retardancy with a limiting oxygen index value of 70% and UL‐94 V‐0 rating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5752–5759, 2008     

Trinuclear tin salicylaldoximate cluster‐catalyzed selective acylation of alcohols

The reactivity and catalytic potential of the tin salicylaldoximate cluster [(Me₂Sn)₂(Me₂SnO)(OCH₃) (HONZO)(ONZO)] ( 1 ), with HONZOH = o‐HON?CH? C₆H₄OH, on the acylation reaction of various alcohols with ethyl acetate is reported. The catalyst is active toward primary and unhindered secondary alcohols, but inefficient toward tertiary and secondary bulky alcohols and phenols. A possible mechanism for the transesterification reaction catalyzed by 1 , accounting for the influence of steric factors, is proposed. Copyright © 2005 John Wiley & Sons, Ltd.     

酯交换法制备生物柴油的研究进展

作为一种对环境友好的可再生燃料生物柴油,对解决日益枯竭的石油资源和由石化柴油燃烧带来的环境问题具有重要意义.综述了运用酯交换反应制备生物柴油的几种方法的研究进展,对其优、缺点和研究趋势进行了归纳总结和展望.     

Catalysts derived from waste slag for transesterification

MgO-CaO/SiO2 solid catalysts derived from waste slag (WS) of metal magnesium plant were prepared. The catalytic performances were evaluated in the transesterification of rapeseed oil with methanol to biodiesel in a 500 mL three-necked reactor under atmospheric pressure. The basic strengh of the catalyst reached 22.0 measured by indicators accroding to Hammett scale. The results show that the MgO-CaO/SiO2 is an excellent catalyst for transesterification, and the conversion of rapeseed oil reach 98% under the optimum condition.     

Chemical reactions between immiscible polymers in the melt: Transesterification of poly(ethylene-co-methyl acrylate) with mono-hydroxylated polystyrenes

This article presents a unique example dealing with how chemical reactions between immiscible polymers in the melt behave differently than they would do in solution. Specifically, a model reaction was chosen: the transesterification between poly(ethylene-co-methyl acrylate) (EMA) and polystyrene mono-hydroxylated at the chain end (PSOH). It was carried out in the melt in a batch mixer. The overall rate of this reaction has a similar dependence of temperature, composition of reactants, and the nature and concentration of catalyst as in solution. The reactivity of PSOH decreases drastically with increasing molecular weight, and it becomes very weak when the molecular weight exceeds 8000 g/mol. As opposed to a reaction in solution or in a homogeneous melt, mechanical mixing increases the reaction rate since it generates interfacial area and reduces the diffusion length. The EMA-g-PS graft copolymer formed at the interfaces reduces the interfacial tension, and increases the miscibility of the reaction mixture. However, its occupation of the interfaces reduces contact between the reactive moieties, thus decreasing the overall reactivity. More importantly and much to our surprise, adding 1 to 2 wt % of an inert solvent increased greatly the overall reaction rate. While an increased interfacial mixing and diffusion by the presence of minor amounts of solvent are thought to be the major factors contributing to the drastic increase in reactivity, numerous questions still remain. Nevertheless, this study clearly showed that as opposed to a reaction in solution, mechanical mixing and the presence of minor amounts of solvent are two additional and critical means to control chemical reactions between immiscible polymer melts. © 1995 John Wiley & Sons, Inc.