共查询到20条相似文献,搜索用时 15 毫秒
1.
偶联反应一般是指C-C偶联或C-N等的偶联,像Still反应、Suzuki反应和Buchwald反应等,它们中的反应催化剂一直以来是使用均相钯配体催化剂,对于负载型钯催化剂的使用较少。将载钯催化剂用于偶联反应是有机合成反应中均相反应多相化的典型例子,且在工业化生产中较均相催化剂更具有优势。从负载钯催化剂的制备、介孔碳的制备及反应驱动力三个方面介绍了偶联反应的近期进展,并对未来发展进行了展望。 相似文献
2.
3.
金属钯催化的Suzuki偶联反应是碳一碳偶联反应中的最重要的反应之一。传统的均相催化体系具有很多的不足,如产物与催化剂不易分离、原料价格昂贵、催化剂不能重复使用等,而使用无配体负载钯的催化剂可有效地解决上述问题。综述了近些年来无配体材料负载钯催化Suzuki偶联反应的研究进展,载体包括碳材料、多孔分子筛、水滑石、高分子材料、金属氧化物、硅藻土、纤维素、磷灰石和氟硅胶等。 相似文献
4.
5.
Zhiyong Wang Yuan Pu Dan Wang Jie-Xin Wang Jian-Feng Chen 《Frontiers of Chemical Science and Engineering》2018,12(4):855
With the development of carbon catalysts, graphene-based metal-free catalysts have drawn increasing attention in both scientific research and in industrial chemical production processes. In recent years, the catalytic activities of metal-free catalysts have significantly improved and they have become promising alternatives to traditional metal-based catalysts. The use of metal-free catalysts greatly improves the sustainability of chemical processes. In view of this, the recent progress in the preparation of graphene-based metal-free catalysts along with their applications in catalytic oxidation, reduction and coupling reactions are summarized in this review. The future trends and challenges for the design of graphene-based materials for industrial organic catalytic reactions with good stabilities and high catalytic performance are also discussed. 相似文献
6.
催化裂化汽油的二次反应 总被引:4,自引:0,他引:4
从降烯烃、降硫和增产丙烯的现实需要出发,分析了FCC汽油二次反应中的理想和非理想反应.用小型提升管催化裂化实验装置考察了FCC粗汽油在REUSY、ZRP和MO-REY沸石催化剂上二次反应的产品分布和改质汽油组成;探讨了操作强度对二次反应转化率和选择性的影响.结果表明:在Y型或ZRP沸石催化剂作用下,FCC汽油二次反应不仅产生更轻的干气和富含丙烯的液化气,也产生更重的柴油和焦炭.二次反应得到的改质汽油与原料汽油相比,其烯烃含量和硫含量降低,芳烃含量和辛烷值明显提高.二次反应的转化深度和选择性取决于原料汽油的烯烃含量、催化剂沸石类型和操作强度. 相似文献
7.
钯催化剂催化卤代芳烃和芳基硼酸生成碳一碳键的Suzuki偶联反应是合成联苯化合物的最重要的途径之一。相比于传统均相钯催化剂的利用率低,污染产品等缺点,磁性钯催化剂易回收,可重复利用,具有工业化应用前景,受到了广泛的关注。综述了近年来无配体磁性钯催化剂、无包裹磁性钯配体催化剂以及以碳、氧化硅、聚合物包裹的具有核壳结构的磁性钯配体催化剂的制备及其催化Szuki偶联反应的研究进展。 相似文献
8.
A series of ZnNiMo/γ-alumina catalysts with variable Zn/(Ni + Zn) ratio were synthesized. These catalysts were characterized by chemical analysis, temperature programmed reduction (TPR) and BET surface area. After that, these catalysts were tested in the individual reactions of hydrodesulphurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of 2-methylnaphthalene (2MN). The results showed an increment of the catalytic activity, for both reactions, when the catalysts were doubly promoted with Ni and Zn in comparison to those mono-promoted catalysts. 相似文献
9.
《Reactive Polymers》1990,12(2):187-192
Macroporous styrene-divinylbenzene and 4-vinylpyridine-divinylbenzene copolymers were used as supports for an iron Fischer-Tropsch catalyst. The catalytic systems were studied in batch reactions of uniformly supported catalysts, continuous reactions of uniformly supported catalysts and continuous reactions of fully heterogenised catalysts. We have shown that the particular distribution of products and selectivity observed for the corresponding homogeneous catalytic systems are in general conserved in the supported ones. The supported induces a better selectivity in alkene synthesis, and for the fully heterogenised system there is, depending on the rate of gas flow, a relatively important selectivity in the oxy product. 相似文献
10.
This overview covers the recent achievements in the application of mesoporous molecular sieves as catalysts and catalyst supports. Main structural and textural features are outlined in relation to the novel synthesis approaches of mesoporous molecular sieves and understanding of their properties. For application of mesoporous molecular sieves as catalysts different ways of introduction of active sites on their surfaces are provided. The main part describes selected catalytic reactions catalyzed by mesoporous molecular sieves focused on very recent papers. The examples include metathesis, acylation reactions, C–C coupling reactions of Heck and Suzuki types, base-catalyzed reactions (Knoevenagel and Michael additions, Claisen-Schmidt condensation, Tischenko reaction) and last but not least immobilization of organometallic complexes for different catalytic applications including chiral catalysts. 相似文献
11.
Marcos J. Jacinto Osvaldo H.C.F. Santos Renato F. Jardim Richard Landers Liane M. Rossi 《Applied Catalysis A: General》2009,360(2):177-182
We here report the synthesis, characterization and catalytic performance of new supported Ru(III) and Ru(0) catalysts. In contrast to most supported catalysts, these new developed catalysts for oxidation and hydrogenation reactions were prepared using nearly the same synthetic strategy, and are easily recovered by magnetic separation from liquid phase reactions. The catalysts were found to be active in both forms, Ru(III) and Ru(0), for selective oxidation of alcohols and hydrogenation of olefins, respectively. The catalysts operate under mild conditions to activate molecular oxygen or molecular hydrogen to perform clean conversion of selected substrates. Aryl and alkyl alcohols were converted to aldehydes under mild conditions, with negligible metal leaching. If the metal is properly reduced, Ru(0) nanoparticles immobilized on the magnetic support surface are obtained, and the catalyst becomes active for hydrogenation reactions. 相似文献
12.
Toshifumi Fujioka Prof. Dr. Nobutaka Numoto Dr. Hiroyuki Akama Kola Shilpa Michiko Oka Dr. Prodip K. Roy Dr. Yarkali Krishna Prof. Dr. Nobutoshi Ito Prof. Dr. David Baker Prof. Dr. Masayuki Oda Prof. Dr. Fujie Tanaka 《Chembiochem : a European journal of chemical biology》2022,23(2):e202100435
Natural aldolase enzymes and created retro-aldolase protein catalysts often catalyze both aldol and retro-aldol reactions depending on the concentrations of the reactants and the products. Here, we report that the directionality of protein catalysts can be altered by replacing one amino acid. The protein catalyst derived from a scaffold of a previously reported retro-aldolase catalyst, catalyzed aldol reactions more efficiently than the previously reported retro-aldolase catalyst. The retro-aldolase catalyst efficiently catalyzed the retro-aldol reaction but was less efficient in catalyzing the aldol reaction. The results indicate that protein catalysts with varying levels of directionality in usually reversibly catalyzed aldol and retro-aldol reactions can be generated from the same protein scaffold. 相似文献
13.
Patricia Taladriz-Blanco Pablo Hervés Jorge Pérez-Juste 《Topics in Catalysis》2013,56(13-14):1154-1170
We intent to present an overview of the available catalysts for the carbon–carbon cross-coupling reactions based on supported palladium (Pd) nanoparticles (NPs). We begin this perspective with a brief introduction about the cross-coupling reactions and the mechanistic implications of using Pd NPs as catalyst, i.e. heterogeneous versus homogeneous catalysis, then we summarize some of the most versatile Pd supported catalysts as a function of its nature. The supported catalysts have been classified in inorganic, organic and hybrid supports. Finally we outline the perspectives for the development of new Pd supported catalysts. 相似文献
14.
介绍了1990年以来全世界化学工业中投入生产的新酸碱催化过程。这些过程采用的催化剂主要为沸石,杂多酸,离子交换树脂,改性氧化锆和超强碱等,涉及的反应类型包括均相和多相催化的液相和气固相反应。同时对酸碱催化未来的研究方向进行了评述。 相似文献
15.
The Role of the Support in the Oxidative Destruction of Chlorobenzene on Pt/Zeolite Catalysts: An FT-IR Investigation 总被引:1,自引:0,他引:1
The vapor-phase cyclohexane oxidative dehydrogenation has been investigated over several catalysts. A typical catalyst for total oxidation, as Mn2O3, materials applied in the field of oxide hydrogenation reactions, as silica-supported vanadia- and niobia-based catalysts, V-, Fe-, and Ce-phosphates used for partial oxidation reactions and ZSM5 zeolite, protonic and Co exchanged, have been tested. Over almost all the catalysts, benzene is the main product obtained, although cyclohexene is obtained with high selectivity at low conversion on phosphate catalysts. 相似文献
16.
New types of Lewis acids as water-compatible catalysts have been developed. Various metal salts were found to work as Lewis acid catalysts in aqueous media, and catalytic asymmetric aldol reactions in such media have been attained. Furthermore, Lewis acid-surfactant combined catalysts, which can be used for reactions in water without using any organic cosolvents, have been also developed. These investigations will contribute to reducing the use of harmful organic solvents and to develop efficient catalytic systems which cannot be realized in conventional organic solvents. 相似文献
17.
18.
19.
A core–shell Pt in ceria type of catalyst prepared by a microemulsion technique shows high activity for both water gas shift and reverse water gas shift reactions but it does not catalyze methanation from carbon oxides and hydrogen feeds at all, whereas Pt-ceria catalysts prepared by traditional methods are effective for all these reactions under comparable reaction conditions. This clearly reveals the fact that the nature of active sites for shift reactions is different from those of methanation reactions, where a special metal-support interface in catalysts created by microemulsion offers the differentiation. 相似文献