Practical ruthenium/lipase-catalyzed asymmetric transformations of ketones and enol acetates to chiral acetates

Ketones were asymmetrically transformed to chiral acetates by one-pot processes using a lipase and an achiral ruthenium complex under 1 atm of hydrogen gas in ethyl acetate. Molecular hydrogen was also effective for the transformation of enol acetates to chiral acetates without additional acyl donors with the same catalyst system.     

CO2吸附活化的研究进展

本文分析讨论了CO₂ 在金属催化剂和金属氧化物催化剂上吸附活化的机理及活化吸附态的反应性能, 提出了CO₂ 作为一种温和氧化剂在化工生产中加以综合利用的有效途径。     

Multicatalytic processes using diverse transition metals for the synthesis of alkenes

A series of cascade processes for the synthesis of alkenes from alcohols is described. Each individual step is catalyzed with a specific transition metal complex. The oxidation-methylenation one-pot procedure took place in the presence of a palladium and a rhodium catalyst to produce the desired terminal alkenes in high yields. A methylenation-ring-closing metathesis allowed the synthesis of cyclic alkenes from carbonyl derivatives, using the second-generation metathesis catalyst. Finally, an oxidation-methylenation-RCM process that involves up to three different transition metal catalysts in the same vessel is presented.     

CO2吸附活化的研究进展

本文分析讨论了CO₂ 在金属催化剂和金属氧化物催化剂上吸附活化的机理及活化吸附态的反应性能, 提出了CO₂ 作为一种温和氧化剂在化工生产中加以综合利用的有效途径。     

Nanoinks in inkjet metallization — Evolution of simple additive-type metal patterning

Recent advances in the development of stable dispersions of nanophase metal particles have allowed the direct fabrication of metal patterns (e.g., printed circuits, RFID tags, touch screens, etc.) by simple additive type inkjet processes. Such processes replace the more costly and less environmentally friendly subtractive lithographic type photoprocesses involving selective etching of photoresists and metal layers and more complex additive type process using photocatalysts for patterned metal deposition by electroless plating processes and inkjet patterning of metal catalyst or catalyst precursor for subsequent metallization by electroless plating. The recent development of electrohydrodynamic jet printing (e-jet printing), in which the ink drop is ejected under the influence of an electric field, has allowed a significant resolution increase vs. conventional inkjet printing with a piezoelectric head (printing resolution of ca. 100 nm for e-jet printing vs. ca. 20 μm for inkjet printing).     

Ionic liquids as a medium for enantioselective catalysis

Over the last years, interest involving ionic liquids (ILs) used as reaction medium for homogeneous enantioselective catalysis has exponentially expanded. In many cases, the use of ILs provides several advantages over reactions in organic solvents in terms of activity and enantioselectivity. Even more important, the catalyst immobilization in IL can avoid its leaching and consequently favour its recycling. This review deals with recent advances in the investigation of these new solvents in asymmetric catalysis. We go over enzymes, chiral organocatalysts and metal complexes containing chiral ligands used in enantioselective processes using ionic liquids, with special emphasis on the catalyst reuse and also the separation of organic products.     

Dry Reforming of Methane Over Cobalt Catalysts: A Literature Review of Catalyst Development

Dry reforming of methane produces syngas with desirable H₂/CO ratio. Besides noble metal catalysts, the cobalt catalyst performs good activity in this reaction. However, carbon deposition and catalyst deactivation are becoming the main problems inhibiting the scale up of this process into industrial application. Recently, many scientists were trying to increase the activity as well as the stability toward coking by using variants of support, promoter, and combination of metal series catalyst. This paper presents a recent technology of methane dry reforming over cobalt metal-base catalyst, covering the catalyst activity and their resistance of catalyst deactivation.     

多相催化时空演变的全生命周期表征策略

可持续发展的化学工业需要新型高效的催化材料和催化过程,尤其需要生态友好、本质安全的新催化过程,其本质是提高合适反应器内催化剂的选择性、活性和稳定性.因此,通过原位技术实时表征反应状态下的催化剂结构并同步测试催化性能,有助于全面研究真实反应条件下催化剂及其表面物种随时间的演变过程,深入理解催化剂构效关系的本质,为开发新一代催化技术提供科学依据.迄今,在实际催化体系中实现催化剂从活化、运行到失活的全生命周期表征仍存在巨大挑战.本文综述了分子筛、金属、金属氧化物三类典型催化剂在甲醇制烯烃、费托合成、丙烷脱氢等催化反应中的全生命周期时空演变,分析了所采用的表征研究策略,以期为新型工业催化的应用基础研究提供启示.据文献报道,甲醇制烯烃反应案例主要利用了原位紫外-可见光谱和固态核磁共振光谱等获得SAPO-34分子筛催化剂从诱导期、自催化期到失活期的表面烃池物种性质和动态演变;费托合成反应案例主要利用了同步辐射X射线衍射计算机断层扫描和X射线吸收光谱等技术研究单个毫米级Co/γ-Al2O3催化剂颗粒在还原条件和费托合成条件下的催化剂结构演变;丙烷脱氢反应案例主要结合原位的紫外-可见和拉曼光纤探头分析了CrOx/Al2O3催化剂在700 ml固定床反应器中不同床层积炭的时空演变.这些研究案例表明,因受限于表征仪器的时空分辨率和适用工况,多数重要的催化反应尚未完全实现工业条件下的全生命周期表征;但通过合理简化非关键变量,可以获得近似工业条件下的多相催化时空演变规律,这些原位表征研究拓展了多相催化的新认识新发现.着眼未来,近似工业反应条件的原位表征、多尺度的原位表征装置设计、反应条件下的计算模拟等策略将在催化研发中发挥重要作用.这些全生命周期表征策略反映了催化研究范式的转变,但将其应用于工业实践仍面临许多科学和工程的挑战.从实际应用角度看,还需综合考虑原位表征技术的成本、安全性和准确性,重视催化剂颗粒及反应器尺度的原位表征,不断推进新型催化剂的研发.     

The Effect of the Surface Oxygen Concentration of Catalysts on Activation of Methane

The improvement of synthesis gas production process is a very important research field in natural gas industry. Recent years, many researchers have suggested that catalytic partial oxidation of methane could be an attractive alternative as a process for synthesis gas production owing to its many advantages. So, it is very important to study the activation over supported metal catalyst. Activation of methane over supported metal catalysts was investigated using MS-pulse techniques in the absence of gaseous oxygen.     

Perfluorinated membranes as catalyst supports

The perfluorinated polymer Nafion and porous PTFE/Nafion composite membranes have been employed as supports for nickel complexes or for platinum and palladium metal particles. The resultant materials have been employed as catalysts in various olefin conversion processes. Supported platinum and palladium metal systems were evaluated as catalysts for the hydrogenation of cyclohexene. Rates of reaction are better than those of commercially available catalysts; turnover numbers in excess of 6000 have been obtained with no poisoning apparent. Catalysts may be regenerated many times. The reduction rate approaches a limit at high pressures of hydrogen and has an activation energy of 13 kJ mol^?1 in neat cyclohexene. Nafion was employed as a strong acid cocatalyst to activate and then support a nickel complex catalyst. The resultant catalyst was active for double-bond-shift isomerization.     

The versatility of metal halide-quaternary ammonium salt catalysts for organic processes. From homogeneous to glass-encapsulated ion pairs

Ion pairs generated from transition metal halides and quaternary onium salts are versatile catalysts for many organic processes. Under phase transfer conditions, RhCl₃- and/or PtCl₄-Aliquat 336^® catalyze (a) double bond migration in allylic compounds, (b) disproportionation of cyclic 1,3-dienes, (c) selective transfer reduction of alkenes, alkynes, α,β-carbonyl compounds, and aroyl chlorides by polymethylhydrosiloxane, (d) hydrogenation of double, triple, and aromatic C-C bonds at room temperature, (e) cyclooligomerization of mono-, di-, and triacetylenes, and (f) addition of water, sulfur, and carbon monoxide to alkynes. In processes (a)-(c) the metal catalyst can be recovered in the aqueous phase by treatment of the reaction mixture with lipophilic anions. Two alternative methods for the recovery of the ion pair catalysts have been investigated. One is based on catalyst encapsulation in sol-gel matrices and the other employs polystyrene-supported ion pairs.     

Steering Site-Selectivity in Transition Metal-Catalyzed C−H Bond Functionalization: the Challenge of Benzanilides

Selective C−H bond functionalization catalyzed by metal complexes have completely revolutionized the way in which chemical synthesis is conceived nowadays. Typically, the reactivity of a transition metal catalyst is the key to control the site-, regio- and/or stereo-selectivity of a C−H bond functionalization. Of particular interests are molecules that contain multiple C−H bonds prone to undergo C−H bond activations with very similar bond dissociation energies at different positions. This is the case of benzanilides, relevant chemical motifs that are found in many useful fine chemicals, in which two C−H sites are present in chemically different aromatic fragments. In the last years, it has been found that depending on the metal catalyst and the reaction conditions, the amide motif might behave as a directing group towards the metal-catalyzed C−H bond activation in the benzamide site or in the anilide site. The impact and the consequences of such subtle control of site-selectivity are herein reviewed with important applications in carbon-carbon and carbon-heteroatom bond forming processes. The mechanisms unraveling these unique transformations are discussed in order to provide a better understanding for future developments in the field of site-selective C−H bond functionalization with transition metal catalysts.     

The Novel Process for Diphenyl Carbonate and Polycarbonate Production

We developed a novel process for production of diphenyl carbonate (DPC) and polycarbonate (PC), which achieved smaller energy consumption, lower environmental load than conventional processes. DPC is produced from phenol and carbonyl dichloride using a new nitrogen containing catalyst without the use of organic solvent. Transesterification of DPC and bisphenol-A to produce PC is performed in the presence of an alkali metal compound catalyst controlling the amount of branching structures and the polymer molecular weight based on the kinetics. The first commercial plant based on this process started in 2000.     

Highly efficient Pt/TiO2 photocatalyst prepared by plasma-enhanced impregnation method

Highly efficient Pt/TiO₂ photocatalyst has been prepared using plasma-enhanced impregnation method. Impregnated 0.5 wt%Pt/TiO₂ was treated by plasma followed with thermal calcinations and hydrogen reduction. The catalyst characterizations show that Pt is highly dispersed with a size of 3–5 nm. UV–Vis reflection spectrum suggests it a high photosensitivity in near UV region. Such plasma prepared catalyst exhibits a much higher activity and better metal stability for hydrogen generation from methanol/water mixture, compared to the catalyst prepared conventionally. This highly efficient photocatalyst should have extensive applications in photocatalytic processes.     

Synthesis of five-membered N-heterocycles using silver metal

The heterocyclic chemistry field has been revolutionized using transition metal catalyst in recent years. Various research groups have focused on the development of general protocols to achieve better functional group compatibilities and greater levels of molecular complexity under mild reaction conditions using easily available starting substrates. These methods afford many advantages as compared to alternative pathways involved in the synthesis of heterocyclic compounds. In this review article, we have concentrated on the synthesis of nitrogen-containing five-membered heterocylces in the presence of silver catalyst.     

Recent Developments on Catalytic Applications of Nano-Crystalline Magnesium Oxide

Nanocrystalline metal oxides, MgO, CuO, ZnO, TiO₂ as catalysts or catalyst supports have been received much attention in the recent years, especially nanocrystalline magnesium oxide (NAP-MgO) has been used as a recyclable catalyst for Wittig, Wadsworth–Emmons, aza-Michael, Baylis–Hillman, Strecker, Aldol, Claisen-Schmidt condensation and other useful organic reactions. In general, it is reported that nanocrystalline magnesium oxide shows better activity in many organic reactions. These high reactivities are due to high surface areas combined with unusually reactive morphologies. The nanomaterials were also explored as supports to make supported metal catalysts for the organic reactions. The higher activity of these catalysts was studied partly to understand the mechanism of the reaction, the putative reaction pathways were preliminarily presented with the help of spectroscopic support, XPS, silicon, and phosphorus NMR spectroscopy. The catalysts are recovered and reused for several cycles. These catalytic systems are expected to contribute to the development of benign chemical processes.     

Recent advances on the use of active anodes in environmental electrochemistry

Active anodes, especially those consisting of metal mixed oxides (MMOs) containing Ru and/or Ir oxides, have been applied in the treatment of wastewater, especially when chloride ions are present. Their characteristics continuously drive the study of applications of these materials, be they in the degradation of different organic molecules, the preparation of new electrode materials and in the association of various processes to increase pollutant removal. Thus, this brief review aims to present some of the recent advances in the application of active anode materials in environmental electrochemistry. Focussing on the 2018–2020 period, it is possible to note many applied studies, using commercially available materials, covering a wide range of target pollutants. Still other studies aim to modify the catalyst surfaces to increase the mineralization capacity, and the use of these anodes in the production of free chlorine species to mediate indirect organic reduction is observed.     

Encapsulation of transition metal catalysts by ligand-template directed assembly

Encapsulated transition metal catalysts are presented that are formed by templated self-assembly processes of simple building blocks such as porphyrins and pyridylphosphine and phosphite ligands, using selective metal-ligand interactions. These ligand assemblies coordinate to transition metals, leading to a new class of transition metal catalysts. The assembled catalyst systems were characterized using NMR and UV-vis spectroscopy and were identified under catalytic conditions using high-pressure infrared spectroscopy. Tris-3-pyridylphosphine binds three mesophenyl zinc(II) porphyrin units and consequently forms an assembly with the phosphorus donor atom completely encapsulated. The encapsulated phosphines lead exclusively to monoligated transition metal complexes, and in the rhodium-catalyzed hydroformylation of 1-octene the encapsulation of the catalysts resulted in a 10-fold increase in activity. In addition, the branched aldehyde was formed preferentially (l/b = 0.6), a selectivity that is highly unusual for this substrate, which is attributed to the encapsulation of the transition metal catalysts. An encapsulated rhodium catalyst based on ruthenium(II) porphyrins and tris-meta-pyridyl phosphine resulted in an even larger selectivity for the branched product (l/b = 0.4). These encapsulated catalysts can be prepared easily, and various template ligands and porphyrins, such as tris-3-pyridyl phosphite and ruthenium(II) porphyrins, have been explored, leading to catalysts with different properties.     

锌-空气电池双功能催化剂研究进展

锌-空气电池因其拥有理想的能量密度和功率密度,并有望在能源转化与储存领域的广泛应用,引起国内外研究者的高度关注. 其中,空气电极作为氧催化反应的核心区域,更是整个锌-空气电池研究的重点. 近年来,非贵金属双功能催化剂及其电极以其高活性、低成本以及种类丰富等特点取得了较多的研究成果. 本文综述了非贵金属氧化物催化剂、碳基催化剂、碳载过渡金属化合物复合材料以及自支撑电极在锌-空气电池中的反应机制和研究进展,提出了高效双功能催化剂的构建策略,并对双功能催化剂/电极的发展趋势进行了展望.     

Synthesis of Novel Chiral Dibenzo [ a, c ] cycloheptadiene Bis(oxazoline) and Catalytic Asymmetric Reactions

Over the last decade, C2-symmetric chiral oxazoline metal complexes have been recognized as an effective classof chiral catalyst in a variety of transition metal catalyzed asymmetric reactions. [1] High catalytic activities and enantiomeric excesses have been obtained using C2-symmetric chiral ligands in conjunction with suitable transition metal ion, for example, the hydrosilylation of ketone, allylic alkylation, Michael addition, Diels-Alder cycloaddition, and cyclopropanation. Thus, the design and synthesis of new chiral oxazoline ligands have inspired many scientists to work with great efforts.