共查询到20条相似文献,搜索用时 78 毫秒
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高分子负载锰卟啉的合成及其催化烯烃环氧化反应研究 总被引:8,自引:0,他引:8
本文用羟基取代四苯基卟啉锰通过醚键与聚苯乙烯树脂键联,合成了一类高分子负载化锰卟啉化合物。经ESR、IR、UV-vis散射光谱等测定证实其结构。本文同时考察了它们对烯烃环氧化反应的催化活性,结果表明,负载化金属卟啉在催化烯烃环氧化反应中能集均相和多相催化的优点于一体,不仅催化剂稳定性增强,而且易于分离和重复使用。 相似文献
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μ-氧代四苯基双核金属卟啉仿生催化剂的研究进展 总被引:3,自引:0,他引:3
综述了国内外及本课题组有关μ-氧代四苯基双核金属卟啉仿生催化剂合成及应用的最新研究进展和成果. 重点介绍了μ-氧代四苯基双核金属卟啉的合成方法, 即两步合成法、柱色谱分离法、一步合成法、自氧化法以及本课题组最新开发的一锅法. 其中一步合成法和自氧化法由于具有适用范围广、收率高等优点, 将成为μ-氧代四苯基双核金属卟啉的主要合成方法. 而一锅法尽管目前收率尚较低, 但由于其完全去掉了中间反应产物的分离和提纯以及原料和溶剂的损失, 而使工艺流程得到大大简化、能耗显著降低, 将成为一种极有发展潜力的合成方法. 系统地阐述了μ-氧代四苯基双核金属卟啉在仿生催化领域中的应用. 尤其是以μ-氧代四苯基双核金属卟啉为催化剂、O2或空气为氧化剂的催化氧化反应, 具有催化剂用量少、氧化剂清洁且廉价易得、无需助催化剂和共还原剂、反应条件温和等优点, 将成为未来仿生催化氧化领域研究的前沿和热点. 相似文献
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Heterogeneous and homogeneous nucleation processes of strontium sulphate have been studied, using a homogeneous precipitation technique together with electronic particle counting. Four different heterogeneous nucleation processes were observed in solutions purified by conventional filtration. In solutions purified by continued circulation through a fibre-glass filter mat, homogeneous nucleation was observed at supersaturations about 10.75. The rate of homogeneous nucleation was found to depend on the 27th power of the sulphate concentration, indicating that the nucleus contains 52 ions. The results support the theory of homogeneous nucleation presented by Nielson. 相似文献
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Based on the synthesis and characterization of side-chain liquid crystal polysiloxanes containing p-methoxyl phenyl benzolate, the homogeneous electrorheological (ER) liquid and its smart damper were fabricated. The properties of the homogeneous ER liquid and its smart damper were tested. The results indicated that the homogeneous ER liquid with significant ER effect at room temperature is obtained by mixing the side-chain liquid crystal polysiloxanes containing p-methoxyl phenyl benzolate and silicone oil. Its shear stress reached 1550Pa at electrical field strength (E) of 2.2 kV/mm and shear rate of 300 s-1. The damping forces of the smart damper based on the homogeneous ER liquid enhanced if E and oscillation frequency increased. Consequently, an effective way for semi-active control using the smart damper based on the homogeneous ER liquid was put forward to reduce the seismic responses of the structures. 相似文献
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Mónica García‐Mota Noemí Cabello Dr. Feliu Maseras Prof. Antonio M. Echavarren Prof. Javier Pérez‐Ramírez Prof. Nuria Lopez Dr. 《Chemphyschem》2008,9(11):1624-1629
The development of new sustainable chemical processes requires the implementation of ultra‐selective reaction processes. The enormous selectivity found for gold‐based catalysts when applied in several reactions has opened new frontiers. For instance, the selective activation of alkynes is a common feature for both homogeneous and heterogeneous gold catalysts. Herein, we employ experimental and theoretical methods to assess the similarities and differences in the performance of homogeneous and heterogeneous gold catalysts. Alkynophilicity, the selective activation of alkynes, is found to have a thermodynamic origin in the heterogeneous case and a kinetic one for homogeneous catalysis. Complex enyne rearrangements require the more active homogeneous (single gold) catalyst because it has more electrophilic character than its heterogeneous (nanoparticle) counterpart. 相似文献
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《Journal of membrane science》2003,211(1):71-90
Video-microscopy flow-visualization (VMFV) is adapted to study the development of macrovoid (MV) pores in the dry-casting of cellulose acetate (CA)/acetone/water solutions. Particle tracer velocities provide the first direct evidence for the presence of solutocapillary-driven convection that can enhance mass-transfer to a MV. Three phases of MV development are observed: fast initial growth, slow growth, and collapse. During the latter, MVs were observed on occasion to initiate far from the demixing front. These studies have led to a significantly modified hypothesis for MV development. Extremely rapid initial MV growth is thought to occur owing to coalescence of dispersed phase microdroplets. To ensure net mass-transfer to a growing MV, it is postulated that a homogeneous supersaturated solution layer must exist between the demixed fluid layer and the homogeneous stable solution layer. Fast growth also involves convective mass-transfer to the MV whose surface is initially entirely immersed in this homogeneous supersaturated solution layer. Slow growth involves net transport that results from both convective mass-transfer to the MV across the portion of its surface in contact with the homogeneous supersaturated solution layer, and convective mass-transfer from the portion of its surface that extends into the homogeneous stable solution layer. Active collapse is thought to occur owing to skin formation at the MV surface. Passive collapse occurs when the convective mass-transfer from the MV in the homogeneous stable solution layer exceeds that entering the MV in the homogeneous supersaturated solution layer. 相似文献
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Stasiak M Studer A Greiner A Wendorff JH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(21):6150-6156
This paper describes a polymer fiber-based approach for the immobilization of homogeneous catalysts. The goal is to generate products that are free of catalysts which would be of great importance for the development of optoelectronic or pharmaceutical compounds. Electrospinning was employed to prepare the non-woven fiber assembly composed of polystyrene. The homogeneous catalyst scandium triflate was immobilized on the polystyrene fibers during electrospinning and on corresponding core shell fibers using a fiber template approach. An imino aldol and an aza-Diels-Alder model reaction were carried out with each fibrous catalytic system. This resulted in the immobilization of homogeneous catalysts in a polymer environment without loss of their catalytic activity and may even be enhanced when compared with reactions carried out in homogeneous solutions. 相似文献
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M. N. Zafar A. H. Atif M. F. Nazar S. H. Sumrra Gul-E-Saba R. Paracha 《Russian Journal of Coordination Chemistry》2016,42(1):1-18
This review provides a broad overview of the literature related to the importance of pyridine and related ligands in homogeneous catalysis. In particular, it describes the various ways by which this ligand can stabilised the metal within a complex for homogeneous catalysis. We surveyed the important transition metal homogenous catalysts containing pyridine and related ligand acting as backbone for other ligands in homogeneous catalytic reactions explicitly from 2011 up to early 2014 and summarized their comparative catalytic activities. 相似文献
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I. Ružić 《Journal of Electroanalytical Chemistry》1985,189(2):221-228
The improved “Heterogeneous Equivalent” method for simulation of very fast first and pseudo-first order homogeneous reactions coupled with electrode reaction has been extended for the treatment of moderately fast and slow homogeneous reactions. New algorithms have been developed avoiding the simulation of homogeneous kinetics through finite difference approximation. Instead, the analytical expression for the term containing the kinetic parameter has been included in combination with other constant parameters (such as the diffusion coefficient). 相似文献
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Charles Vriamont Prof. Michel Devillers Prof. Olivier Riant Prof. Sophie Hermans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12009-12017
A new pyrene‐tagged gold(I) complex has been synthesised and tested as a homogeneous catalyst. First, a simple 1,6‐enyne was chosen as a model substrate for cyclisation by using different solvents to optimise the reaction conditions. The non‐covalent immobilisation of our pyrene‐tagged gold complex onto multi‐walled carbon nanotubes through π–π stacking interactions was then explored to obtain a supported homogeneous catalyst. The heterogenised catalyst and its homogeneous counterpart exhibited similar activity in a range of enyne cyclisation reactions. Bearing in mind that π–π interactions are affected by temperature and solvent polarity, the reuse and robustness of the supported homogeneous catalyst was tested to explore the scope and limitations of the recyclability of this catalyst. Under the optimised conditions, recyclability was observed by using the concept of the boomerang effect. 相似文献