共查询到18条相似文献,搜索用时 78 毫秒
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温控配体与液/液两相催化 总被引:2,自引:2,他引:2
以作者近年的研究工作为主,对液/液两相催化研究领域取得的进展做一综述.着重介绍了以温控配体为基础的新型液/液两相催化过程温控相转移催化(thermoregulatedphasetransfercatalysis,TRPTC)和温控相分离催化(thermoregulatedphase-separablecatalysis,TPSC)的基本原理及其在高碳烯烃氢甲酰化、芳香硝基化合物的CO选择性还原及烯烃加氢等反应中的应用.基于温控配体在水中的“浊点”特性而提出的温控相转移催化概念,为从根本上解决水/有机两相催化
的适用范围受底物水溶性限制的问题提供了一条新途径.而利用温控配体在某些有机溶剂中存在临界溶解温度(CST)的特性而实现的温控相分离催化,则使在高于临界溶解温度的反应温度时为均相的反应体系,在低温(<CST)时则分成两相,催化剂自成一相,形成一种具有“均相反应、两相分离”特色的液/液两相催化新体系. 相似文献
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研究了稀土催化体系对聚对苯二甲酸乙二酯固相缩聚反应的催化效果及对所得高分子量聚酯切片性能的影响,发现稀土催化体系可明显提高聚酯固相缩聚的反应速率,稀土催化体系对聚酯固相缩聚反应的催化活性明显高于传统催化体系,其中单一稀土催化体系与混合稀土催化体系在较低温度下具有相近的催化活性,而在较高温度下单一稀土催化体系的催化活性较高;加入稳定剂,不影响稀土催化的固相缩聚反应速率,稀土催化固相缩聚得到的PET样品具有较高的结晶度和较大的晶粒尺寸,其中单一稀土催化所得样品的晶粒尺寸最大,相应地,单一稀土催化的固相缩聚反应活化能也最大;稀土催化体系催化聚酯固相缩聚反应时添加适当稳定剂,可获得与采用传统催化体系得到的PET切片相近的热稳定性。 相似文献
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金属络合物的相转移催化分析与分离 总被引:2,自引:0,他引:2
以可简单分离回收、可反复使用为目标,详细介绍了相转移催化的变化发展过 程.通过对溶剂的选择,使得催化剂选择性地溶解在某一液相中,而使产物溶解在 另一液相中,如水-有机两相催化体系;通过温度的变化,简单地实现了在较高温 度下反应为均相体系以提高催化剂的活性,而在较低温度下实现了催化剂与产物不 相溶使得催化剂得以简单分离,如温控型水-有机两相催化体系、氟-有机两相催化 体系、温控型含氟催化剂、温控型有机金属催化剂等. 相似文献
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温控非水液/液两相催化,是指一类由两种或多种液态有机物组成的催化反应体系,其特点是体系的相态变化可通过温度来调控,即体系在高温时相互混溶呈均相,低温不溶分成两相,催化剂和产物分别处于两相,从而为解决均相催化剂分离难的问题开拓了一个新方向,是液/液两相催化研究领域最引人注目的进展之一.首次以"温控"为主线将氟两相催化作为温控液/液两相催化的一个特定类型纳入"温控非水液/液两相催化"范畴,并与其它通过温度来调控的有机液/液两相和作者提出的温控相分离催化串在一起作一较为详细的评述. 相似文献
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温控相转移催化——水/有机两相催化新进展 总被引:14,自引:0,他引:14
综述了“温控相转移催化”的原理,温控膦配体的设计、合成及其在水溶性极小的底物高碳烯烃的水/有机两相氢甲酰化反应中的应用效果. 相似文献
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Although driven by different research interests, single-site catalysts and single-atom catalysts are both believed to be model systems bridging homogeneous and heterogeneous catalysis. The two concepts are similar but different. In this review, we will first explain the difference between single-atom catalysis and single-site catalysis, in terms of their goals, synthetic methods and coordination structures of corresponding catalysts. Then, we will introduce the surface organometallic chemistry method, a method traditionally used for synthesizing single-site catalyst. We will explain why it might benefit the single-atom catalysis community. At last, the choice of support to accommodate the method for synthesizing single-atom catalysts will be discussed. 相似文献
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Steven L. Regen 《Angewandte Chemie (International ed. in English)》1979,18(6):421-429
Triphase catalysis (TC) has recently been introduced as a unique form of heterogeneous catalysis in which the catalyst and each of a pair of reactants are located in separate phases. Based on this concept, new synthetic methods have been developed for aqueous phase–organic phase reactions using a solid phase catalyst. Although it is only at an early stage of development, TC shows considerable potential for practical use. Our mechanistic understanding of these highly complex catalytic systems is at present very limited and detailed examination will be required before their relationship to phase-transfer, micellar, and interfacial catalysis becomes clear. 相似文献
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本文以作者在温控水/有机两相及温控非水液/液两相催化领域的研究工作为主线,对这一领域的研究进展作一评述,重点是环绕经典水/有机两相催化体系存在“应用范围受底物水溶性限制”的根本问题展开。特别是对“温控相转移催化”作了较为详细的介绍,同时,按体系介质不同,对氟两相体系、PEG两相体系、离子液体两相体系等非水液/液两相体系以及温控相分离催化分别作了阐述。 相似文献
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以对羟基苯甲醛的钠盐为亲核取代试剂,采用相转移催化进行了大分子氯甲基聚苯乙烯的亲核取代反应,将其转变为侧链带有功能性基团醛基的聚苯乙烯;考察了反应条件(如有机溶剂的极性、催化剂种类及用量、有机相与水相之比等)对大分子相转移催化反应的影响,并根据相转移催化反应机理与相关的动力学规律进行了分析.结果表明,通过相转移催化亲核取代反应,可将氯甲基聚苯乙烯大分子链上的氯原子转化,制得侧链带有醛基的聚苯乙烯;溶剂的极性越强,负离子的反应活性也越高;催化剂季铵正离子的亲脂性越强,相转移催化反应的速率越快.当催化剂浓度较低时,四丁基溴化铵比十六烷基溴化铵的催化效果好;当催化剂浓度较高时,十六烷基溴化铵比四丁基溴化铵的催化效果好.另外,有机相与水相之比对相转移催化反应有较大的影响. 相似文献
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本文基于烃类选择氧化领域中的大量实例从起源、实现途径及应用状况几个角度对活性位分离和相间协同作用进行了评述。这两条原则已构成多相选择氧化催化的两大支柱:活性位分离是选择氧化催化剂获得选择性的必要条件,并在其他一些重要反应中起着重要的作用;相间协同则是不同晶相间发挥作用的一种方式,主要通过界面内聚和遥控机理发生作用。 相似文献
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The synthetic utility of alkyl‐onium salt compounds is widely recognized in the field of organic chemistry. Among the wide variety of onium salts, quaternary ammonium, phosphonium, and tertiary sulfonium salts have been the most useful compounds in organic syntheses. These compounds have been very useful reagents in the construction of organic building blocks. In addition, onium salts are known as reliable catalysts, which are used to promote important organic transformations by serving as phase‐transfer and ion‐pair catalysts through the activation of nucleophiles. Although phase‐transfer catalysis is a major direction for onium salt catalysis, hydrogen‐bonding catalysis of alkyl‐onium salts, which is promoted via the activation of electrophiles, has recently become a relevant topic in the field of onium salt chemistry. This Minireview introduces new possibilities and future directions for alkyl‐onium salt chemistry based on its use in hydrogen‐bonding catalysis and on its overall utility. 相似文献