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91.
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Hsu‐Chin Hsiao Hung‐Shan Weng 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2001,76(9):959-965
As the second part of a series of studies on the synthesis of n‐butyl phenyl ether (ROPh) by tri‐liquid‐phase catalysis, this work examines the factors affecting the reaction between n‐butyl bromide (RBr, organic substrate) and sodium phenolate (NaOPh, aqueous nucleophile) with poly(ethylene glycol)‐600 (PEG‐600) as a phase‐transfer catalyst. The reaction is performed in a batch reactor at 45–85 °C for 2 h while the agitation speed is fixed at 1000 rpm. Experimental results indicate that the individual mole fractions of NaOPh and PEG‐600 slightly affect the reaction, while the total amount of these components exerts significant influence. When the mole fraction of PEG‐600 is 0.5, the reaction rate and the conversion of RBr are the highest. No byproducts are formed in the course of the reaction. The system using a non‐polar organic solvent might obtain a higher conversion compared with a weakly polar one owing to a higher concentration of PEG‐600 in the third liquid phase. Furthermore, adding NaOH facilitates the reaction to obtain a higher reaction rate than adding other kinds of salt because the addition of a base results in the formation of a third liquid phase. The catalytic ability of PEG with average molecular weight of 600 gmol?1 is far higher than that with average molecular weight of 200, 400 and 1000 because PEG‐600 possesses an appropriate chain length which can tightly associate with Na+ to form the complex of PEG‐600‐Na+OPh? for reacting with RBr. In addition, this nucleophilic substitution reaction is found to be pseudo‐first‐order with respect to RBr. © 2001 Society of Chemical Industry 相似文献
93.
梯形试体三向千斤顶直剪试验法 总被引:2,自引:0,他引:2
介绍一种研究岩体软弱结构面抗剪强度的新的试验方法---梯形试体三向千斤顶直剪试验法。工程实践证明 ,新方法是可行的 ,对类似工程地质条件下的抗剪强度研究具有参考价值 相似文献
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影响热硫化硅橡胶生胶质量的主要因素 总被引:1,自引:1,他引:0
讨论了三官能链节、端羟基、三甲胺和挥发分含量及摩尔质量分布对热硫化硅橡胶生胶质量的影响,以及控制和预防的方法。 相似文献
99.
Haiqiao Wang Qingjiang Sun Yongfang Li Lian Duan Yong Qiu Xiaoyu Li 《Polymer International》2003,52(3):343-346
A new electroluminescent copolymer [poly(1,5‐di(3,5‐dimethyloxystyrylene)naphthalene‐block‐tri(ethylene oxide)) (DSN–TEO)], containing alternating rigid, conjugated light‐emitting units and flexible tri(ethylene oxide) ionic conductive units, was synthesized via the Wittig reaction. The polymer has fairly good solubility in chloroform, tetrahydrofuran, toluene, etc, and excellent film‐forming ability. The decomposition temperature and the glass transition temperature were 409 °C and 42.2 °C, respectively. A light‐emitting diode (LED) device with configuration ITO/PEDOT–PSS/DSN–TEO/Ca(Al) and light‐emitting electrochemical cell (LEC) device with ITO/DSN–TEO + PEO (LiTf)/Al were prepared, and the photoluminescence and electroluminescence (EL) properties were investigated. Efficient blue‐green light emission (EL maximum emissive wavelength at 508 nm) was found with onset voltage at 6 V. The maximum light efficiency was 0.107 cd A?1 at 20 V for LED, and the onset voltage 2.5 V and the maximum light efficiency was 4.2 cd A?1 at 2.8 V for LEC, respectively. The response time of the LEC was less than 5 s. The EL efficiency of LEC device was improved by 44 as compared with the relative LED device. © 2003 Society of Chemical Industry 相似文献
100.
1550nm光传输技术已成为广电网络传输的主流技术,用1550nm光传输系统组网有结构简单、应用方便、可靠性高、投资少等特点,是目前广电双网双改较理想的传输方案。根据1550nm光传输技术CIN指标的计算,前端和分前端以及光节点的实用组网方式,并结合EPON、EoC、IPQAM技术,为加快广电农网双改建设提供了理论和实践依据。 相似文献