New approaches to supramolecular transition metal catalysis

The combination of molecular recognition, phase transfer catalysis and transition metal catalysis in one and the same water–soluble catalyst leads to new perspectives, including increased activity, novel substrate selectivity and the possibility of simple catalyst recovery. For example, Rh–complexes of β–cyclodextrin modified diphosphanes function as supramolecular catalysts in aqueous two–phase hydrogenation and hydroformylation. Metal–containing dendritic compounds constitute another new class of supramolecular catalysts which are easily recycled. This revised version was published online in June 2006 with corrections to the Cover Date.     

铑催化剂催化烯烃不对称加氢反应研究进展

不对称催化氢化反应具有完美的原子经济性和清洁高效等特点,是最受青睐的不对称合成方法之一。C=C、C=O、C=N的不对称加氢反应仍主要依赖过渡金属催化剂。过渡金属催化剂,尤其是铑催化剂,催化碳碳双键的不对称加氢反应仍是一个不断发展的领域。本文对近年来利用铑催化剂催化烯烃进行不对称氢化反应的研究进展进行了综述,着重介绍了铑-双膦配体催化体系催化烯烃不对称加氢反应的催化机理,以及铑催化剂在烯胺、不饱和羧酸及衍生物、烯醇酯和非官能团烯烃不对称氢化中的应用,并通过对现有文献的总结指出了今后铑催化剂催化烯烃氢化反应的研究重点,即:①铑-单膦配体催化烯烃不对称氢化反应的作用机理须待提出;②非官能化底物不对称催化氢化反应的手性配体亟待拓宽。     

贵金属催化剂理性设计在选择性加氢反应中的研究进展

从多相催化的特征出发,综述了多相催化理性设计中典型调控理论和方法的研究进展。同时,以芳香硝基化合物及不饱和醛/酮选择性加氢反应为特征反应,从多相催化剂表面的电子效应、几何效应、界面效应和协同效应等角度进行了全面综述。指出了筛选合适的载体、合成特定尺寸形貌的活性中心、调控金属-载体强相互作用是开发更高效的多相选择性加氢催化剂的重要方向,调控金属-载体强相互作用,优化活性中心的电子效应、空间效应和界面效应,微调N=O及C=O不饱和键的吸附与活化,是实现高效选择性加氢催化体系的理论设计的重要手段。进一步优化氢气的活化裂解方式、活性氢的稳定与迁移,可抑制选择性加氢的副反应。     

Attempts to Fill the Gap Between Enzymatic, Homogeneous, and Heterogeneous Catalysis

Bio-inspired and single site metal complex catalysts have been discussed to direct towards a rational design of solid heterogeneous catalysts. When concepts derived from catalytic antibodies, molecular imprinting and molecular recognition, and site isolation and modification by appropriate ligands are combined, with new techniques to prepare, tailor made solid materials, catalysts can be prepared that improve reaction rate and selectivity by increasing the concentration and activation of reactants in the vicinity of the active sites, and by stabilizing transition states or intermediate products. It is also shown that enzymatic, homogeneous and hetergeneous catalysts can be combined to perform “one-pot” cascade reactions.     

铑催化高碳烯烃氢甲酰化合成高碳醇进展

介绍了近年来铑／膦催化高碳烯烃氢甲酰化的研究和开发进展。特别是以ＴＰＰＯ／Ｒｈ为催化剂的Ｍｉｔｓｕｂｉｓｈｉ Ｋａｓｅｉ工艺和水／有机两相为主的各种两相催化技术。近年的进展表明,通过创新膦配体以及采用两相催化体系,有望使更有效,更经济的铑催化工艺在高碳烯烃氢甲酰化的应用中取得突破。     

Thermoregulated phase transfer ligands and catalysis. III. Aqueous/organic two-phase hydroformylation of higher olefins by thermoregulated phase-transfer catalysis

A series of poly(ethylene oxide)-substituted triphenylphosphines, Ph_3−mP[C₆H₄-p-(OCH₂CH₂)_nOH]_m (PEO-TPPs; 1a m=1, 1b m=2, 1c m=3; N=m×n=8–25), have been prepared by the ethoxylation of mono-, di-, and tri-p-hydroxytriphenylphosphines. PEO-TPPs demonstrate an inverse temperature-dependent solubility in water, and possess distinct cloud points range from 26°C to 90°C.

Based on the clouding property of PEO-TPPs, a new line of aqueous/organic two-phase catalysis termed the thermoregulated phase-transfer catalysis (TRPTC) has been described. That is, the catalyst transfers into the organic phase to catalyze a reaction at a higher temperature, and returns to the aqueous phase to be separated from the products at a lower temperature. Application of this novel strategy to the rhodium-catalyzed two-phase hydroformylation of higher olefins gave desirable results with an average turnover frequency of 180 h⁻¹ for 1-dodecene. The TRPTC is suitable for carrying out a reaction with extremely water-immiscible substrate in the aqueous/organic two-phase system. Thus, the application scope of the classical two-phase catalysis has been widened.     

Molecular-Level Characterization of Heterogeneous Catalytic Systems by Algorithmic Time Dependent Monte Carlo

Monte Carlo algorithms and codes, used to study heterogeneous catalytic systems in the frame of the computational section of the NANOCAT project, are presented along with some exemplifying applications and results. In particular, time dependent Monte Carlo methods supported by high level quantum chemical information employed in the field of heterogeneous catalysis are focused. Technical details of the present algorithmic Monte Carlo development as well as possible evolution aimed at a deeper interrelationship of quantum and stochastic methods are discussed, pointing to two different aspects: the thermal-effect involvement and the three-dimensional catalytic matrix simulation. As topical applications, (i) the isothermal and isobaric adsorption of CO on Group 10 metal surfaces, (ii) the hydrogenation on metal supported catalysts of organic substrates in two-phase and three-phase reactors, and (iii) the isomerization of but-2-ene species in three-dimensional supported and unsupported zeolite models are presented.     

离子液体在两相催化中的研究进展和应用前景

介绍了近年来离子液体用于液液两相催化加氢、氧化、Heck反应、氢酯化和羰化反应的研究进展,特别是结合离子液体在高碳烯烃氢甲酰化和低碳烯烃齐聚中试成果和已经实现工业应用的实例,从绿色化工的角度对其在化学工业中的应用前景进行了评述。     

Preparation of recoverable Ru catalysts for liquid-phase oxidation and hydrogenation reactions

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.     

我国合成气一步法制低碳烯烃催化剂研究新进展

合成气一步法制低碳烯烃作为优势明显的非石油路线替代技术,至今仍未工业化的一个关键问题即催化剂的选择性较差。本文介绍了近十年来关于该催化剂的研究进展,分析了活性组分、助剂、载体及制备工艺分别对催化剂结构与性能的影响,认为Fe系与Co系是最有应用前景的催化剂,碱金属、碱土金属、过渡金属、稀土金属及非金属在调变催化剂酸碱性与电性上各自表现出不同的正作用,抑制了低碳烯烃的二次加氢副反应。分子筛等载体的表面性质与孔道结构可控,方便低碳烯烃从催化剂中扩散移除。浸渍、沉淀、溶胶-凝胶、熔融、水热、微波、超临界、真空干燥等工艺的改进或结合更有利于活性组分的分散和超细颗粒的形成。指出催化剂配合适宜的工艺及反应器才能发挥最大效能,才有可能突破F-T合成中低碳烯烃收率低的ASF规律的限制,实现合成气一步法制低碳烯烃的产业化推广。     

络合浸渍法制备Ni/ZrO_2催化剂及其催化顺酐液相加氢性能

分别以柠檬酸、乙二胺、乙酰丙酮以及乙二胺四乙酸二钠为络合剂,采用络合浸渍法制备Ni质量分数为10%的Ni/ZrO_2催化剂,考察催化顺酐液相加氢性能,并利用XRD、H2-TPR、H2-TPD等对其进行表征。结果表明,各络合剂对催化剂中金属-载体相互作用、活性金属分散度以及C=O加氢活性的影响均不相同。引入乙酰丙酮的Ni/ZrO_2-AC催化剂具有最高的活性金属分散度和C=O加氢活性,表现出最高的γ-丁内酯选择性,该催化剂在反应温度210℃、氢压5 MPa条件下反应3 h,顺酐转化率约100%,γ-丁内酯选择性47.0%。     

过渡金属催化剂加氢脱硫作用机理研究

从过渡金属催化剂的活性相结构和反应物在催化剂表面活性位上的吸附—催化反应机理两个方面阐述了过渡金属催化剂的催化作用研究进展,并对过渡金属催化剂催化机理研究存在的争议和未来的研究方向进行了分析。     

钌基催化剂用于直接法合成气制低碳烯烃反应

以γ-Al₂O₃为载体,通过等体积浸渍法制备钌基催化剂,用其进行催化CO加氢,研究制低碳烯烃反应中钌基催化剂的催化性能,考察催化剂的焙烧温度、工艺条件及碱金属助剂Na对钌基催化剂CO加氢反应的影响。结果发现,焙烧温度400 ℃制备的钌基催化剂具有最大的比表面积,在反应温度220 ℃、反应压力1.0 MPa和空速1 500 mL·(h·g)^-1条件下,可以保证较高的CO转化率及低碳烯烃选择性。碱金属助剂Na提高了催化剂催化活性,Na质量分数为4%6%时,钌基催化剂表现出最佳的CO转化率及低碳烯烃选择性。     

On the activity, longevity and recyclability of Mn(II) and Co(II) substituted AlPO-18 catalysts for the conversion of methanol to light olefins

The influence of the degree of substitution of the cobalt and manganese ions into AlPO-18 structure was investigated for the conversion of methanol to light olefins (MTO) at 350 °C. The results show that the activity for methanol conversion increases with transition metal content up to 2 at.% for conversion of methanol after 2 h on stream. These catalysts show good stability for this reaction after regeneration suggesting that there is no leaching of the active metal centres.     

Heterogeneous enantioselective hydrogenation over cinchona alkaloid modified platinum: mechanistic insights into a complex reaction

Modification of a metal surface by a strongly adsorbed chiral organic molecule has proven to be an interesting strategy for heterogeneous chiral catalysis. Platinum chirally modified by cinchona alkaloids, successfully applied for the enantioselective hydrogenation of alpha-ketoesters, is probably the most prominent catalyst based on this concept. Despite considerable research efforts toward understanding of this complex catalytic system, the proposed mechanistic models are still debated. Here we discuss how enantiodifferentiation can be induced on a catalytically active surface and validate the models proposed for the platinum-cinchona system in the light of the existing molecular knowledge.     

Platinum group metals as catalysts in enantioselective 1-phenylpropane-1,2-dione hydrogenation

Different γ-Al₂O₃ supported Ir, Pd, Ru, Rh and Pt catalysts were tested in enantioselective 1-phenylpropane-1,2-dione hydrogenation using cinchona alkaloid modifiers. Activity and enantioselectivity over Ir and Ru catalysts were low. Pd catalyst was active in the hydrogenation of 1-phenylpropane-1,2-dione, however, the enantioselectivity over this catalyst was almost negligible. Over Pd hydrogenation proceeded mainly via hydrogenation of the C₁O₁ carbonyl group, which is attached to the phenyl ring. Hydrogenation over Pd did not proceed in the second hydrogenation step via an enol form as found for ethyl pyruvate hydrogenation over Pd. The structure-selectivity relationship and solvent effects are similar over Pt and Rh in the first hydrogenation step. However, in the second hydrogenation step of hydroxyketones to diols large mechanistical differences between Pt and Rh were observed. Although the activity over Rh catalysts was lower than over Pt after optimization the best result obtained with Rh/γ-Al₂O₃ (5754 Lancaster) was 60% ee in toluene at maximum yield of 28%, which makes Rh a promising metal for enantioselective hydrogenation.     

A comparison between β- and USY-zeolite-based hydrocracking catalysts

Two series of zeolite-based hydrocracking catalysts were prepared to study the effects of the support type, preparation method and metal loading on catalyst properties and hydrocracking activity for hydrotreated vacuum gas oil (HT-VGO). The support used was γ-Al₂O₃ and β-zeolite in the first series and γ-Al₂O₃ and USY-zeolite in the second series. Nickel and tungsten were loaded as active metals on these supports. The prepared catalysts were characterized as to their surface area, pore volume, thermal stability, reducibility and acidity characteristics. The characterization results revealed that catalysts displayed significant differences in properties dependent on the preparation method and the type of support used. Catalysts from both series showed promising results for HT-VGO hydrocracking in the batch reactor. A correlation exists between the reducibility of oxidic form and the hydrogenation activity of the sulfided form of the catalysts. The higher the reducibility, the higher the hydrogenation activity. Catalysts prepared on mixed supports gave higher amounts of saturates.     

Investigation of factors influencing sodium sulfide oxidation in the presence of polymeric heterogeneous catalysts of transition metal oxides

The activity of heterogeneous catalysts of transition metal oxides and their mixtures deposited on the polymeric matrix in the oxidation of sodium sulfide was investigated. It is shown that mixtures of manganese oxide and other transition metal oxides have high catalytic activity. It was evident that the positive synergistic effect occurred in the combined action of two or more catalytically active transition metal oxides, and the maximum effect was observed in the mixture of three catalytic agents of transition metal oxides. Catalytic mechanism of transition metal oxides for sulfide oxidation was studied. The kinetics of formation of products of sodium sulfide oxidation was studied in the presence of heterogeneous catalysts based on phthalocyanine cobalt and transition metal oxides. The dependence of the rate of formation of products of sodium sulfide oxidation on alkali concentration was investigated. Some factors influencing the oxidation rate such as sulfide, oxygen and alkaline concentrations, antioxidant and oxidation products were investigated.     

New catalytic systems for selective oxidation of aromatic compounds by hydrogen peroxide

Some new water-soluble catalytic systems based on iron complexes of polyethylene oxide and block copolymers of ethylene oxide and propylene oxide functionalized by catechol or β-cyclodextrin have been developed. These complexes were examined as catalysts for biomimetic hydroxylation of benzene and phenol by hydrogen peroxide. It is shown that the introduction of β-cyclodextrin into the polyethylene oxide molecule is favourable for rate and selectivity of hydroxylation of aromatic compounds in a two-phase system.     

过渡金属硫化物催化稳态活性相

过渡金属硫化物（TMS）是清洁燃料油生产最为常用的催化剂,有关它的催化活性相及其作用机理一直以来是催化研究的重点和热点。本文一方面强调研究TMS催化稳定态活性相的重要性;另一方面综述了催化稳定态中碳的存在形式及其作用,对新提出的MoSxCy和CoMoC（或NiMoC）模型进行了阐述和讨论,指出传统CoMoS相可能并不是稳定态的催化活性相,而只是其前体,并认为过渡金属碳化物与TMS等加氢处理催化剂很可能具有统一的类MoSC催化稳态活性相结构。