共查询到18条相似文献,搜索用时 171 毫秒
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负载固相的催化剂因其简便的分离循环操作以及可观的催化性能而广受关注,但存在反应活性较差、金属流失量较大、催化剂制备成本较高等问题。本文首先从不同负载材料的角度综述了近年来该类催化剂最新的研究进展,主要探讨了载体的表面性质、催化剂的制备方法、膦配体等对催化性能的影响;最后介绍了新型的单原子催化剂所取得的突破性进展。分析表明:具有"类均相"特点的多孔有机聚合物的催化活性很好,而超支化聚合物功能化的磁性纳米催化剂的稳定性更佳。另外还对负载型铑催化剂未来的研究方向进行了展望:需要进一步加深对多孔有机聚合物的化学结构的理解,以便对其更好地表征;借助一些先进的表征技术如高角环状暗场扫描透射电镜和密度泛函理论的计算来深入研究载体结构对单原子催化剂的催化性能的影响。 相似文献
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利用浸渍法制备了两种二氯二茂钛(Cp2TiCl2)/坡缕石黏土负载型催化剂Cat-A 和Cat-B,并进行了乙烯淤浆聚合评价。对热活化黏土进行表征的结果表明,坡缕石黏土在热活化过程中由于配位结晶水的脱除表面主要由Lewis酸性位占据。黏土载体所具有的表面酸性使其具有完全不同于硅胶载体的负载茂金属催化剂聚合行为。在相同的聚合条件下,直接负载型催化剂的活性高于载体化学修饰型催化剂,甚至高于均相Cp2TiCl2催化剂。直接负载催化剂所得聚合产物的分子量和熔点低于载体化学修饰催化剂,且其产物性质受温度影响更为显著。以硅胶负载型茂金属催化剂作为对比,分析了表面具有较强Lewis酸性的载体活性中心性质,以此解释了直接负载型催化剂的乙烯聚合特性。对直接负载型催化剂不同时间段的聚合产物形态进行了扫描电镜观察,发现最终聚合产物中聚合物“纤维”和“纤维”聚集体形态的形成,并进一步分析了聚合物形态演化过程的特点。 相似文献
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文章介绍了茂金属催化剂载体的研究新进展,着重介绍了无机载体和有机载体用于茂金属催化剂负载化的研究现状。分别陈述了无机和有机载体的一些常见载体类型,例如硅胶载体和聚苯乙烯载体;并对比了无机载体和有机载体的颗粒形态,强度,表面基团等物理化学性质的差异。研究表明,载体材料本身结构及其物理化学性质对聚合活性,聚合物形态和堆积密度有着直接的作用。进一步探索载体的结构性能与聚合动力学的关系,将对对进一步提高聚合活性,改善聚合物颗粒形态具有深远的意义。 相似文献
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因催化剂与产物不易分离的问题,氢甲酰化反应催化剂固载化研究受到广泛关注。本文从分子筛、二氧化硅、碳材料、金属氧化物、磁性纳米粒子、有机聚合物和离子液体这些不同负载材料的角度综述了过去十年来的相关研究结果,并对不同载体的优缺点和发展前景进行了简要分析。固载型催化剂分为3种不同的构建方式:载体与配体连接、载体与金属连接以及载体同时与配体和金属连接。第3种构建方式制备的催化剂更稳定,常在二氧化硅作为载体中使用。第一种构建方式为催化剂制备提供了多样性,在无机物和有机物作为载体中都有广泛使用,其中,含磷的有机聚合物在提供良好催化剂效果的同时,也提高了催化剂的稳定性,对未来的研究方向有一定的指导意义。 相似文献
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多孔碳纳米球由于可实现尺寸、形貌、孔结构以及表面基团等的可控合成制备,其负载/镶嵌的金属粒子又兼具高活性和高热稳定性等,在多相催化领域中受到越来越多的关注。本文追溯了多孔碳纳米球形貌调控的发展历程及其负载金属催化剂在催化反应领域中的应用。归纳了不同形貌的多孔碳纳米球及其制备方法和原理,详细对比了各个方法的优缺点;阐述了多孔碳纳米球负载金属催化剂的性能和碳球结构与形貌之间的构效关系;总结了目前碳球作为催化剂载体亟需解决的问题是碳球的多孔结构及其负载尺寸可控和空间匀称分布的金属粒子的可控合成,并展望了其发展方向是进一步研究和探索结构可调、经济可行的碳纳米球制备方法,真正实现工业化应用。 相似文献
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烯烃配位聚合非茂前过渡金属催化剂研究进展 总被引:2,自引:0,他引:2
介绍了非茂前过渡金属催化剂作为高效烯烃聚合催化剂的发展和应用情况。根据催化剂中配位原子的性质将非茂前过渡金属催化剂分为配住原子为N、配住原子为O、配位原子为N和O的三大类进行讨论。重点评述了配体空间结构和电性能对催化活性及聚合物性能的影响。 相似文献
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Wenbin Lin 《Topics in Catalysis》2010,53(13-14):869-875
This paper provides a brief overview of recent progress in the design and synthesis of chiral metal–organic frameworks (CMOFs) and their applications in heterogeneous asymmetric catalysis. Catalytically active CMOFs can be synthesized using two distinct strategies, either by post-synthetic activation of pre-synthesized porous MOFs or by directly linking well-designed catalytically competent bridging ligands with metal ion or metal cluster nodes. Heterogeneous asymmetric catalysis with very high activity and enantioselectivity has been achieved with CMOFs. The intrinsic tunability of CMOFs promises to lead to the design and synthesis of a variety of practically useful heterogeneous asymmetric catalysts for many organic transformations. 相似文献
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G. Borisov 《Advanced Synthesis \u0026amp; Catalysis》1971,313(3):529-545
Phosphorus-containing polymers are known to have valuable properties, primarily the ability of self-extinction. Most favorable results were obtained with substances including phosphorus and chlocrine in their molecules. However, up to now attention was given predominantly to polymers having C O P bonds. The present paper describes the synthesis of phosphorus and phosphorus and chlorine containing polymers with C P bonds using methylol derivatives of phosphorus. Bis-(p-carbomethoxyphenoxymethyl) methylphosphinoxide was used as a phosphine oxide derivative. This phosphorus-containing dicarboxylic acid was reacted with glycols to give phosphorus-containing polyesters and copolyesters. With glycols in excess the reaction led to phosphorus-containing and mixed oligomers which after reaction with diisocyanates yielded polyurethanes, copolyurethanes and urethane block copolymers. Esterification of bis(hydroxymethyl)phosphonic acid with acrylic and methacrylic acid yielded monomers which, when subjected to polymerisation, gave phosphorus-containing polyesteracrylates and methacrylates and, in addition, could be copolymerised with acrylic and methacrylic acid. Mono- and dicondensation products of hypophosphorous acid with chloral, being considered as chlorine-containing methylol derivatives of phosphinic and phosphonic acids, led to polyurethanes. 相似文献
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Prof. Amarajothi Dhakshinamoorthy Assoc. Prof. Sergio Navalón Prof. Abdullah M. Asiri Prof. Hermenegildo Garcia 《ChemMedChem》2020,15(23):2236-2256
Confinement of Au nanoparticles (NPs) within the porous materials with few nanometers (2-3 nm) has been a well established research area in the past decades in heterogeneous catalysis mainly due to the unique behaviour of Au NPs than its bulk counterpart. In this aspect, Au NPs encapsulated within the pore volumes of metal−organic frameworks (MOFs) have been intensively explored as heterogeneous solid catalysts for wide range of reactions. In recent years, Au NPs confined within the porous MOFs along with the photosensitizer or drug have been effectively used for the treatment of tumor cells through the generation of reactive oxygen species via cascade reactions. This work highlights the benefits of MOFs pores in the preparation of nanomedicine with high efficiency by assembling Au NPs, photosensitizer/drug with the combination of laser either for imaging or treatment of tumor cells. Further, the existing literature is grouped based on the nature of porous materials employed in the preparation of nanomedicine. The final section comments on our view on future developments in the field. 相似文献
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Carbon aerogels for catalysis applications: An overview 总被引:4,自引:0,他引:4
Carbon aerogels are nanostructured carbons obtained from the carbonization of organic aerogels, which are prepared from the sol-gel polycondensation of certain organic monomers. These materials have a great versatility both at the nanoscopic level in terms of their pore texture and at the macroscopic level in terms of their form. Thus, the surface area, pore volume, and pore size distribution are tuneable surface properties related to the synthesis and processing conditions, which can produce a wide spectrum of materials with unique properties. In addition, carbon aerogels can be obtained in the form of monoliths, beads, powders or thin films. All these properties make them promising materials for application in adsorption and catalysis. Metal-doped monolithic organic aerogels can be easily prepared by following three main strategies: by addition of the metal precursor to the initial mixture, by ion-exchange or by deposition of the metal precursor on the organic or the carbon aerogel by one of various methods. These metal-doped carbon aerogels have been used as catalysts and as electrodes for electrical double-layer capacitors. This article shows the preparation of metal-doped carbon aerogels, their physico-chemical surface properties and their applications as catalysts in various reactions. 相似文献
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Kirill I. Zamaraev 《Topics in Catalysis》1996,3(1-2):1-76
The possibilities of molecular design in the development of new catalysts and catalytic technologies are discussed with the
data obtained recently at the Boreskov Institute of Catalysis as particular examples. Examples from the following areas are
presented: homogeneous catalysis with metal complexes, heterogeneous catalysis with anchored metal complexes, heterogeneous
catalysis with catalysts prepared via anchored metal complexes and organometallics, catalysis of olefin polymerization, catalysis
by metals, catalysis by oxides, catalysis by zeolites, catalysis by heteropolyacids, catalysis with nontraditional oxidants
and biomimetic catalysis. 相似文献
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A conceptually new strategy for chiral catalyst immobilization, self-supported catalysts, in heterogeneous asymmetric catalysis is highlighted in the present article. Various homochiral metal-organic polymers with diverse structures have been designed and readily prepared through coordination assembly of modular polytypic/polyfunctional ligands and metal ions without using any supports. These polymers have been successfully employed as chiral catalysts in a variety of heterogeneous asymmetric ractions, including hydrogenation, epoxidation, sulfoxidation, carbonyl-ene reactions, diethylzinc addition, and Michael addition. The self-supported heterogeneous chiral catalysts showed activity and enanioselectivity comparable or even superior to those obtained with their corresponding homogeneous counterparts, and could be readily recovered and reused several times without significant loss of activity or enantioslectivity. 相似文献
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《Journal of Industrial and Engineering Chemistry》2014,20(6):3947-3959
A variety of metal oxides catalysts are used in heterogeneous catalysis for chemical processes and have now been developed for their catalytic performance and durability. The heterogeneous catalysis is the most important technology in chemical industry as well as other environmental, energy applications, etc. This review examines recent advances at the preparation and applications of metal oxide particles, especially pertaining to catalytic enhancements for current and future chemical process such as Fischer–Tropsch process, alkylation, and transesterification and environmental applications such as the oxidation of volatile organic compounds and the reduction of NOx. 相似文献