共查询到18条相似文献,搜索用时 578 毫秒
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纳米碳纤维负载钯催化剂在Heck反应中的应用——载体相互作用的影响 总被引:1,自引:0,他引:1
使用多元醇还原法制备了均匀分散的钯纳米颗粒.将钯纳米颗粒负载于板式、鱼骨式和管式纳米碳纤维,得到稳定、可重复使用的非均相催化剂.实验结果表明,钯纳米胶粒同载体之间的电位差对钯在载体上的负载量、粒子大小以及Heck反应中钯的溶失量有很大的影响.在制备过程中,增加钯纳米胶粒同纳米碳纤维表面的电位差能够大大降低钯在Heck反应中的流失.催化剂的反应活性随钯粒子的增大而降低. 相似文献
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壳聚糖基聚合物负载钯配合物的制备及对Heck反应催化性能 总被引:9,自引:0,他引:9
以壳聚糖为基本原料制得壳聚糖缩水杨醛负载钯配合物(S-CTS-Pd)和交联壳聚糖缩水杨醛负载钯配合物(CL-S-CTS-Pd)两种催化剂,利用XPS、TG、DTA等手段对其进行了表征.两种催化剂不需在惰性气体氛围中就能有效地催化芳基碘与丙烯酸、苯乙烯的Heck反应,高产率地得到反式肉桂酸、1,2二苯乙烯,芳基碘上吸电子和供电子取代基的存在对反应没有明显影响.与S-CTS-Pd相比,CL-S-CTS-Pd在较低的温度或较少的催化剂用量下,对Heck反应仍有较高的催化活性.负载催化剂CL-S-CTS-Pd重复使用性能的研究表明,在催化碘苯与丙烯酸反应重复10次后,肉桂酸的产率仍达75.3%. 相似文献
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胺基化树脂负载Pd(0)对Heck反应催化性能的研究 总被引:7,自引:0,他引:7
将氯球用胺化剂、乙二胺、胍进行胺化后负载氯化钯, 在乙醇溶液中用硼氢化钾还原, 制备了含胺功能基树脂负载钯(0)的催化剂; 研究了催化剂对含各种取代基碘代苯与丙烯酸的Heck芳基化反应催化性能. 结果表明, 该类催化剂具有良好的催化活性和重复使用性能, 其中用乙二胺功能化树脂负载的Pd(0)催化剂在90 ℃重复使用17次时能保持良好的催化活性. 催化剂反应前后的SEM形貌图和过滤液的活性试验表明催化剂活性组分Pd(0)在反应中有沥取(leaching)现象. 相似文献
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钯负载介孔氧化锆基复合催化材料的合成与表征 总被引:1,自引:0,他引:1
利用表面活性剂辅助模板及适当后处理工艺实现了少量贵金属氧化钯及稀土氧化铈在有序介孔氧化锆孔道中或孔道表面的均匀分散/负载. 借助XRD, TEM, EDS等分析手段进行样品结构表征; 同时针对不同催化体系探讨了丙烯催化氧化以及Heck反应的催化性能. 研究结果表明, 贵金属钯/稀土氧化铈负载的有序介孔氧化锆体系对丙烯氧化具有良好催化活性, 钯直接负载介孔氧化锆的体系具有优异的Heck反应催化选择性及较少的催化剂使用量. 相似文献
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Some efficient polymer‐supported palladium catalysts have been synthesized. Their catalytic effects were evaluated in the Heck reaction of iodobenzene with acrylates or styrene. High catalytic activities were achieved with turn over frequencies (TOF) up to 28000 and 6250, respectively. For the reaction of iodobenzene with styrene, high stereoselectivity was obtained. Additionally, the catalysts could be recovered by a simple filtration progress and can be reused for at least 5 times with a slow progressive decrease in activity. 相似文献
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Jianmin Zhou Yulin Yang Lan Zhao Xiaokun Li Renxian Zhou Xiaoming Zheng 《Frontiers of Chemistry in China》2009,4(2):142-148
Using MCM-41 as the supporter, a series of MCM-41 supported amino-palladium complexes has been prepared and characterized
by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy), etc. The XRD and XPS results indicate that the Pd coordinates
with the -NH2 groups on the MCM-41 surface, and the structure of MCM-41 has been not damaged. Its catalytic performance for Heck arylation
of alkene with aryl iodide shows that the catalysts have high activity and stereoselectivity in 70–90°C. The product of Heck
reaction is in E form. And the effect of the preparation condition of catalyst on the catalytic performance was examined.
Translated form Chinese Journal of Organic Chemistry, 2008, 28(5) (in Chinese) 相似文献
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Two carbon nanotube supported palladium catalysts were prepared using a chemical reduction technique (Pd/CR‐CNT) and a conventional impregnation method (Pd/CNT) respectively, and their catalytic performances for Heck reaction were investigated. The catalysts were characterized by TEM and XPS techniques and the products were characterized by 1H NMR. Research results showed that the (Pd/CR‐CNT) catalyst showed a better catalytic activity than the (Pd/CNT) catalyst, owing to better dispersion of palladium nanoparticles and stronger interaction between the active palladium species and carbon nanotube. Meanwhile, the product yield maintained 99.93% of its initial value at five‐times re‐use, compared with that at the first time use. The catalyst prepared with the chemical reduction method represented a better reusing performance. 相似文献
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Novel palladium catalysts immobilized on functionalized chlorinated polyvinylchloride nanofiber mats
Well-defined chlorinated polyvinylchloride (CPVC) nanofiber mats were fabricated by electrospinning, and then chemically modified with 1,3-propanediamine (CPVC–NH) and glutaraldehyde (CPVC–NOH) to immobilize palladium active species. The chemical modification could significantly improve the tensile strengths of the CPVC nanofiber mats. Adsorption of Pd(II) ions showed that the treatment of fiber mats with glutaraldehyde decreases it schelating ability. Transmission electron microscopy and X-ray diffraction analysis indicated that palladium species were dispersed more homogeneously on the CPVC–NH fibers than on the CPVC–NOH fibers. Results of Mizoroki–Heck reaction showed that the catalytic activity of Pd catalyst supported on CPVC–NOH fibers was superior to that of the Pd catalyst supported on CPVC–NH fibers. Thus, chemical modification of supporting materials with suitable chelating groups is an efficient way to control the catalytic performance of supported Pd catalysts. 相似文献