Asymmetric Heterogeneous Catalysis: Science and Engineering

Asymmetric heterogeneous catalysis is a vivid branch of catalysis, remaining, however, largely a domain of organic chemists. The view towards asymmetric heterogeneous catalysis adopted in this review is mainly from catalytic science and engineering. Not only reaction mechanisms, but also catalytic properties, kinetic regularities, as well as chemical engineering aspects, are covered with the main focus on recent developments.     

Recent Aspects of Asymmetric Catalysis by Immobilized Chiral Metal Catalysts

In this paper, we have reviewed recent achievements in the field of asymmetric catalysis by metal complexes immobilized onto inorganic and organic supports. Besides allowing for facile catalyst recovery and reuse, immobilized metal complexes show a number of diverse applications and unique performances.     

负载型金催化剂在多相催化中的应用

文章综述了近年负载型金催化剂在环境保护及化学工业方面的应用研究进展,包括CO的常温催化氧化、卤代有机化合物的消除、氮氧化物的还原、丙烯的选择性氧化和氢氧直接氧化法合成双氧水。     

羰基化反应多相催化剂的研究进展

综述了国内外羰基化反应中多相催化剂的研究现状、技术特点及最新进展,指出了羰基化反应多相催化剂的研究方向。     

高通量筛选技术在多相催化研究中的应用

通过对组合催化研究的关键因素－－催化剂高通量筛选技术的评价分析认为：在对已有的催化体系和催化剂优化的同时,如何高校研制开发新筛选检测技术,诸如反应器设计和检测器的选择,是组合催化研究的主导思想,对此的深刻理解和运用将增强实验室的创新能力。     

Ceria-Supported Vinylpyridine Polymers: Synthesis,Characterization and Application in Catalysis

A simple, one-step synthesis of 4-vinylpyridine polymer crosslinked with 2% divinylbenzene [poly(4vp-dvb)] anchored with ceria nanocrystals via in situ reactions that involve simultaneous formation of the polymer and ceria nanocrystals is presented. The polymer support is formed by free radical suspension polymerization of the monomers, while ceria nanocrystals are generated from CeCl₃·7H₂O by the homogeneous precipitation method in a single pot. The polymer supports were characterized by XRD, TEM, SEM, ESCA, and TGA and then tested for their ability as heterogeneous recyclable catalysts in a Biginelli reaction. The catalytic activities of these supports were found to be far superior to the two-step conventional one and simultaneous microporous bead counterparts. Reusability is an added advantage over the other regularly used cerium-based catalysts in aqueous media. The significant increase in the catalytic activity is due to the higher Ce/N ratio and predominance of well-defined and more reactive exposed planes of ceria nanocrystals on the new supports. Such catalysts are of great importance due to environmental, practical and economical concerns.     

Towards Heterogeneous and Green Versions of Os Dihydroxylation Catalysis

Os-catalyzed dihydroxylation will find more widespread application if truly heterogeneous catalysts are available which use O₂ or H₂O₂ as terminal oxidants. This paper discusses and critically evaluates the concepts by which Os can be anchored on solid supports. New methods are also available for reoxidation of hexavalent to octavalent Os.     

Active Sites in Heterogeneous Catalysis: Development of Molecular Concepts and Future Challenges

The concept that catalytic turnover occurs at a small fraction of the surface sites dates back to the 1920s. The application of modern surface science techniques and model catalysts confirmed the presence of active sites and identified their structures in some cases. Low coordination defect sites on transition metals, steps and kinks, or open rough crystal faces that make high coordination metal sites available have been uniquely active for breaking H–H, C–H, C–C, C=O, O=O and NN bonds. Oxide–metal interfaces provide highly active sites for reactions of C–H and C=O bonds. Electron acceptor and proton donor sites are implicated in hydrocarbon conversion (acid–base catalysis), and sites where metal ion–carbon bonds can form are active for polymerization. The observations of dynamic restructuring of catalytic surfaces upon adsorption of reactants indicate that many catalytic sites are created during the chemical reaction. Similar restructuring is detected for enzyme catalysts. The high mobility of both surface metal atoms and adsorbed molecules during the catalytic process observed recently bring into focus the dynamic nature of active sites that may have a finite lifetime as they form and disassemble. The development of techniques that provide improved time resolution and spatial resolution, and can be employed under catalytic reaction conditions will provide information about the time dependent changes of active site structure and molecular intermediates at these active sites as the reaction products form.     

Combinatorial Heterogeneous Catalysis: Oxidative Dehydrogenation of Ethane to Ethylene, Selective Oxidation of Ethane to Acetic Acid, and Selective Ammoxidation of Propane to Acrylonitrile

The application of combinatorial methods to three reactions catalyzed by multimetal oxides is described. Catalysts for the oxidative dehydrogenation of ethane to ethylene were tested using a 121- or 144-channel scanning mass spectrometer primary screening reactor and a 48-channel fixed bed secondary screening reactor; catalysts for the selective oxidation of ethane to acetic acid were tested using a 256-channel massively parallel microfluidic reactor primary screen alone, and catalysts for the selective ammoxidation of propane to acrylonitrile were tested using the massively parallel microfluidic reactor and an eight-channel fixed bed secondary/tertiary screening reactor. The details regarding catalyst design, synthesis, and screening are presented. This work has resulted in both the confirmation of published results and the generation of new lead materials for all three chemistries.     

Phthalic Anhydride from o-Xylene Catalysis: Science and Engineering

Phthalic anhydride is one of the most important products of modem large-scale organic synthesis, and it has a wide application in various branches of chemical industry. It is mostly used (60% of the world production) for preparation plasticizers for PVC. The rapid development of the industrial production of polymeric materials during the last two decades increased the need of phthalic anhydride, which resulted in an increase of its production [1, 2].     

Phthalic Anhydride from o-Xylene Catalysis: Science and Engineering

Phthalic anhydride is one of the most important products of modem large-scale organic synthesis, and it has a wide application in various branches of chemical industry. It is mostly used (60% of the world production) for preparation plasticizers for PVC. The rapid development of the industrial production of polymeric materials during the last two decades increased the need of phthalic anhydride, which resulted in an increase of its production [1, 2].     

Dual Heterogeneous Catalysis for a Regioselective Three‐ Component Synthesis of Bi‐ and Tri(hetero)arylpyridines

We have designed a new, user‐friendly oxidative dual heterogeneous catalytic system capable of promoting polysubstituted pyridines as unique products from simple activated Michael acceptors, 1,3‐dicarbonyls and ammonium acetate. This metal‐free environmentally‐respectful and totally regioselective domino reaction proved to be a great strategy to access bi‐ and triaryl‐type pyridines as well as challenging bi‐ and triheteroaryl‐type pyridines in a single operation.     

Asymmetric Counteranion‐Directed Iron Catalysis: A Highly Enantioselective Sulfoxidation

A highly active and enantioselective ion‐pair sulfoxidation catalyst, consisting of an achiral iron(III)‐salen cation and a chiral phosphate counteranion, mediates the oxidization of various sulfides with high yields and enantioselectivities. The enantioselectivities observed, especially for electron‐poor substrates, represent the best results so far in manganese and iron‐salen systems. This work represents the first application of our concept of asymmetric counteranion‐directed catalysis (ACDC) to iron catalysis.     

New Developments in Advanced Synthesis & Catalysis: Growth and High‐Impact Research for Green Organic Synthesis

Advanced Synthesis & Catalysis has continued on the upward curve in 2011 and passed several milestones along the way. The submissions exceeded 1000, the number of printed pages reached 3500, and the number of published articles passed the 400 mark. With 2010 impact factors of 5.25 (2‐year IF) and 5.36 (5‐year IF) ASC continued to be at the top for green synthesis. Submissions and published papers from Europe and from Asia continue to dominate. Over one quarter of the published papers now come from China and Hong Kong. The percentage of communications continued to grow and is now 54% of the published articles. The new Editorial and Advisory Boards have settled in and with them Advanced Synthesis & Catalysis will further change and develop over the next years. The goal of Advanced Synthesis & Catalysis continues to be to publish seminal research as chemists move toward greener synthesis: “new catalytic systems effecting perfect chemical reactions that give only the desired products, with 100% selectivity and 100% yield without unwanted wastes.”     

冷冻干燥法制备壳聚糖/粘土多孔微球负载钯催化剂的性能研究

利用冷冻干燥法制备得到了具有多孔结构的壳聚糖/粘土(蒙脱土)微球负载钯催化剂,催化剂孔径尺寸较大(100μm)。该催化剂应用于典型丙烯酸丁酯与芳基碘系物的Heck反应时,有较高的催化活性。加入适量粘土使壳聚糖分子链能有效地插入到蒙脱土的片层间,良好的插层结构有助于提升催化材料的耐热性和机械性能。相应地,壳聚糖/粘土多孔微球负载钯催化剂比纯壳聚糖负载钯多孔微球催化剂有更高的重复使用性能。     

金属催化和生物催化在对映体拆分中的联合应用

随着对单一对映体化合物需求的日益增长，外消旋体向单一对映体的转化(去外消旋化过程)成为研究的主要方面之一，最近在去外消旋化过程中的生物催化和金属催化的联合作用被证明是非常有效的。动态动力学拆分和循环去外消旋化已经对这方面的研究有很大的推动作用。     

Enantioselective hydrogenation of ethyl pyruvate over Pt/alumina: systematic variation of the modifier structure

A series of enantiomerically pure amino alcohols and amines has been prepared and tested as modifiers in the enantioselective hydrogenation of ethyl pyruvate over Pt/alumina. Systematic variation of the modifier structure revealed that an extended aromatic π–system is necessary for the function of the modifier and that the enantioselectivity crucially depends on the structure of the amino function. Surprisingly simple modifiers such as 1–(1–naphthyl)ethylamine and 1–(9–anthracenyl)–2–(1–pyrrolidinyl)ethanol proved to be nearly as effective as 10,11–dihydrocinchonidine. This revised version was published online in June 2006 with corrections to the Cover Date.     

宽口径化工专业的工业催化教学探索与实践

培养宽口径化工专业人才是我国高等教育的目标,也是我国高校对人才培养的一次深入探索。我们以工业催化课程教育为落脚点,在教学过程中融入"重基础、宽口径"的教学理念,以人为本,对教学方法和内容形式进行了调整,以期对培养高素质复合型人才产生重要作用。