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Eriksson KL Chow WW Puglia C Bäckvall JE Göthelid E Oscarsson S 《Langmuir : the ACS journal of surfaces and colloids》2010,26(21):16349-16354
With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost. 相似文献
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V. G. Gandhi A. B. Deshpande S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1974,12(6):1173-1179
Methyl methacrylate was polymerized at 40°C with VOCl3–AlEt2Cl catalyst system in n-hexane. The rate of polymerization was proportional to catalyst and monomer concentration at Al/V ratio of 2 and overall activation energy of 9.25 kcal/mole support a coordinate anionic mechanism of polymerization. The catalytic activity and stereospecificity of this catalyst system is discussed in comparison with that of VOCl3–AlEt3 catalyst system. 相似文献
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钯系催化剂的氨中毒研究 总被引:5,自引:0,他引:5
考察了CO常压气相偶联合成草酸酯反应体系中在不同氨含量下P\r\nd系催化剂活性随反应时间的变化.结果表明,随着氨含量的增加,催\r\n化剂活性降低的速率加快,氨含量不超过0.54%时,仅引起催化剂活\r\n性下降,但不会造成催化剂完全失活;当氨含量达1.16%时,催化剂\r\n活性随反应时间迅速下降,直至完全失活.同时,观测了催化剂氨中毒\r\n的不可逆性.利用XPS和TEM表征手段探讨了Pd系催化剂氨中毒机理,并\r\n分析了在工业生产条件下催化剂氨中毒不可逆性的原因. 相似文献
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Pd(OAc)_2/HQ/FePc、Pd(OAc)_2/FePc 催化烯烃氧化合成酮的研究 总被引:2,自引:0,他引:2
考察了在乙腈酸性水溶液中Pd(OAc)2/氢醌(HQ)/酞青铁(FePc)和Pd(OAc)2/FePc对环己烯、环戊烯、苯乙烯、正癸烯氧化合成相应酮的催化活性.实验结果表明,两类催化体系对环戊烯的酮基化均呈现出较高的催化活性,环戊酮收率可达98%.在其它烯烃的氧化反应中,三元催化体系Pd(OAc)2/HQ/FePc的催化活性高于二元的Pd(OAc)2/FePc.这表明,在Wacker类催化体系中,电子传递体的作用是很重要的.对催化体系中各组分的作用进行了讨论,并给出了可能的催化作用机理. 相似文献
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Dual Catalysis Sees the Light: Combining Photoredox with Organo‐, Acid,and Transition‐Metal Catalysis
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Dr. Jun‐Long Li Prof. Dr. Frank Glorius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):3874-3886
The photoredox activation of organic substrates with visible light is a powerful methodology that generates reactive radical species under very mild conditions. When combined with another catalytic process in a dual catalytic system, novel, visible‐light‐promoted transformations have been realized that do not proceed using either catalyst in isolation. In this minireview, the state of the art in organic reactions mediated by dual catalytic systems merging photoredox activation with organo‐, acid or metal catalysis is discussed. 相似文献
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以金属有机化合物甲基三氧化铼(MTO)为催化剂, 双氧水为氧化剂新型化学方法合成环氧大豆油. 详细考察了催化剂在双氧水、溶剂和助剂等因素下的催化性能. 研究了该催化体系在其他油脂环氧化中的应用, 环氧产物的选择性在99%以上. 采用红外光谱法(IR)对产品进行表征. 通过紫外-可见分光光度法(UV-Vis)对催化剂的研究, 发现催化剂(MTO)在催化环氧化过程中形成催化中间体, 且催化活性很高. 对催化剂和双氧水相互作用机理及新型环氧化反应的机理进行了初步研究. 相似文献
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Akira Akimoto Masaaki Ohtsuru 《Journal of polymer science. Part A, Polymer chemistry》1975,13(3):549-558
The effect of the catalytic amount of H2O was investigated with the EtnAlCl3-n-VOCl3 catalyst system on the alternating copolymerization of acrylic monomers with diolefins and styrene. The presence of the catalytic amount of H2O produced an improvement in the yield and in the molecular weight as well as the structure of copolymer with the EtnAlCl3-n-VOCl3 catalyst system. The efficiency of the aluminum components in the EtnAlCl3-n-VOCl3 system appears with AlEt3 and especially with Et1.5AlCl1.5. The catalytic activity was found to depend upon the H2O EtnAlCl3-n molar ratio and was also affected by the order of mixing of the catalyst components and the monomers. Effective catalyst could be prepared when the catalyst components (except VOCl3) were premixed without presence of monomers. The possible catalytic behavior of H2O was discussed. 相似文献
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Through tuning the surface wettability of interfacially active TiO2 particles, a pH-responsive Pickering emulsion system is formed, as in situ separation and recycling of the nano-catalysts system. 相似文献
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M. Foà F. Francalanci A. Gardano G. Cainelli A. Umani-Ronchi 《Journal of organometallic chemistry》1983,248(2):225-230
Catalysts consisting of tetracarbonyl cobaltate anion supported on commercially available anion exchange resins are readily prepared. Carbonylation of organic halides using this heterogenized catalyst leads either to acids or esters depending on the conditions. Some features of this catalytic system and the possible reaction mechanism are discussed. 相似文献
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A cross-linked polymer-supported ionic liquid immobilized palladium catalyst, which is prepared by reaction of the Pd(OAc)2 with copolymer of 3-butyl-1-vinylimidazolium iodide and divinylbenzene, was well characterized and employed as an effective heterogeneous catalyst for carbonylative Sonogashira coupling reaction of aryl iodides with terminal alkynes in water, affording the corresponding α,β-alkynyl ketones in good to excellent yields. The catalytic system not only solves the basic problem of homogeneous palladium catalyst recovery and reuse but also avoids the use of toxic phosphine ligands. The stability of supported palladium was also discussed. 相似文献
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铜基催化剂用于一氧化碳催化消除研究进展 总被引:1,自引:0,他引:1
催化消除CO主要包括CO的完全氧化(CO-COOX)和优先氧化(CO-PROX).首先,结合本课题组的相关研究,按照催化剂体系介绍了Cu基催化剂在CO-COOX中的活性物种和组分之间的相互作用.其次,对用于富氢气氛下CO-PROX的Cu基催化剂进行了系统的分类总结,重点阐述了CuO-CeO2催化剂的制备方法、助剂改性、载体调变以及过渡金属离子掺杂(CuO/Ce1-xMxO2)、反相结构(CeO2/CuO)等方面对CO-PROX催化性能的影响.最后,总结了Cu基催化剂在CO-PROX中存在的问题,并展望了未来的研究趋势. 相似文献
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本文研究了对-甲苯磺酰氯、偶氮苯和四氢呋喃三种添加剂。对乙丙共聚反应的活化作用,实验结果表明,偶氮苯的活化作用最显著,能提高催化效率10倍左右,对-甲苯磺酰氯提高3-6倍,四氢呋喃提高1-2倍。 本文对活化机理作了较详细的探讨,讨论了各种活化剂对聚合反应的影响、活化剂对聚合反应动力学行为的影响,并研究了活化剂与催化剂各组分之间的反应。对上述三种活化剂提出了两种可能的活化途径。对-甲苯磺酰氯和偶氮苯的作用主要是使失去活性的V2+氧化成有活性的V3+化合物,从而增加了活性中心浓度使催化效率提高。而四氢呋喃主要是使V3+化合物稳定而延长活性寿命来提高催化效率。最后还提出了前两种活化剂氧化V2+化合物可能的反应历程。 相似文献
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A. W. Lancer Jr. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):775-787
This paper describes a new catalytic process for linear alpha-olefins by oligomerization of ethylene using a soluble alkyl aluminum chloride-titanium tetrachloride catalyst. Important catalytic and polymerization variables, such as catalyst activity, selectivity to linear products, and molecular weight, are discussed. An ionic mechanism is proposed to explain the unusual features of this new process. 相似文献
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研究了Co(naph) 2 Al(i Bu) 2 Cl催化体系的相态 .通过Tyndall效应、电镜观察和超过滤实验 ,证明了Co(naph) 2 Al(i Bu) 2 Cl催化体系在溶有丁二烯的苯溶剂中以纳米级小颗粒分散 ,在较佳配比时 ,粒径在 1~10 0nm之间 ,为胶体催化剂 ,属于高度分散的多相催化体系 .催化剂的活性位位于胶粒表面 ,催化剂颗粒是无定形的 .以较佳配比得到的催化剂颗粒较小、分布均匀 ,催化丁二烯聚合反应活性高 .归纳出胶体催化剂的制备特点为外观类似于均相催化体系 ,但是制备方法 (各组分配比、加入顺序、陈化等 )对催化活性有明显的影响 .并给出将胶体催化动力学作均相动力学近似的条件 ,在聚合反应初期 ,且单体浓度比烷基铝以及其他填加物浓度大 2~ 3数量级 相似文献
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Xiao Li ZHEN Jian Rong HAN Ru Hong KANG* Xing Mei OUYANG Department of Essential Education Hebei Science 《中国化学快报》2001,(4)
Catalytic dehalogenation of organic halides is of great value to the organic synthesis and for the preventing of environmental pollution. Although, in recent years, there are many reports describing dehalogenation of organic halides in the literature1,2,3, most of them were carried out in the organic system,only few examples4,5 of dehalogenation were carried out in aqueous system. The toxic aryl halides may contaminate and harm human being seriously through food chain. Therefore, it is of utmo… 相似文献