EPOXIDATION OF FUNCTIONALIZED OLEFINS OVER SOLID CATALYSTS

Heterogeneous catalytic epoxidation of functionalized olefins in the liquid phase has been reviewed, focusing on catalyst performance and its interrelation with the crucial parameters of the catalytic systems. Efficient catalysts include supported and mixed oxides, framework-substituted (“redox”) molecular sieves, layered-type materials, heterogenized homogeneous catalysts, and some others. Among the various substrates, allylic and homoallylic alcohols, and unsaturated carbonyl compounds have received most attention so far. The great variety of available catalysts enables selective epoxidation of most substituted olefins. The mechanistic understanding of heterogeneous catalytic epoxidation is still underdeveloped, rendering catalyst design rather empirical. A considerable potential for future development lies in the area of “heterogenization” of successful homogeneous catalysts especially for asymmetric epoxidation. Crucial requirements in the development of heterogeneous catalytic epoxidation catalysts are, besides good catalytic performance and cheap oxidant, recyclability and resistance to leaching of the active component. Some of the examples shown in the literature do not fulfill the latter requirement.     

Preparation of silica-immobilized titanium-containing silsesquioxane catalysts and activity for the epoxidation of alkenes

Silsesquioxanes containing tetrapodal titanium species and alkenylsilyl groups were immobilized onto dimethylsilyl-functionalized silica having mesopores by chemical tethering via hydrosilylative reaction in the presence of a Pt catalyst. The immobilized catalysts showed higher activity than their corresponding homogeneous catalyst towards the epoxidation of cyclooctene by tert-butylhydroperoxide, probably because of the improvement of the micro-environment around the titanium center. The reaction was found to be truly heterogeneous, since no further reaction proceeded after the separation of the catalyst by filtration. These catalysts also showed excellent catalytic activity for the epoxidation using hydrogen peroxide as an oxidant, while the parent homogeneous catalysts did not show any activity at all.     

钼基催化剂在烯烃液相环氧化反应中的应用研究进展

介绍了钼络合物催化剂、固载化的钼络合物催化剂及MoO₃基的固体钼催化剂在烯烃液相环氧化反应中的应用。以有机过氧化物为氧化剂时,不同的钼基催化剂均表现出很好的催化性能,其中络合物中的配体对其催化性能有很大影响,并且可以通过引入手性配体实现对烯烃的不对称环氧化,而固体钼催化剂的性能则与载体上钼物种的种类密切相关。但绝大多数钼催化剂对H₂O₂参与的环氧化反应没有活性,开发对H₂O₂有催化活性的钼基催化剂是一个重要的研究方向。     

Asymmetric epoxidation of unfunctionalized olefins catalyzed by Mn(III) salen complex immobilized on MCM-48

Chiral Mn(III) salen complexes were supported on mesoporous molecular sieve MCM-48 and employed as catalyst in the asymmetric epoxidation of some unfunctionalized olefins. The as-synthesized catalysts showed excellent enantioselectivity than homogeneous catalysts for α-methylstyrene and the highest ee value (up to >99%) was obtained. Furthermore, these catalysts were also effective for bulkier olefins such as indene and 1-phenylcyclohexene. Compared to homogeneous counterparts, the heterogeneous catalysts are more stable and can be recycled three times without loss of enantioselectivity.     

Chiral salen Mn(III) immobilized on sulfoalkyl modified ZSP-IPPA as an effective catalyst for asymmetric epoxidation of unfunctionalized olefins

Sulfoalkyl modified zirconium poly (styrene-isopropenyl phosphonate)-phosphate (ZPS-IPPA), with special structures of new type of organic–inorganic hybrid material were designed and synthesized for immobilization of the chiral salen Mn(III) Jacobsen’s homogenous catalyst by axial coordination. All the heterogeneous chiral salen Mn(III) catalysts with different linkage lengths obtained exhibited great catalytic activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. The influence of the linkage lengths on the catalytic performance was investigated. What’s more, the catalysts were easily separated from the reaction systems and could be reused for several times without significant loss of catalytic activity.     

烯烃环氧化钼系催化剂的多相化研究进展

介绍了以有机聚合物和无机硅酸盐为载体，负载钼催化剂及其对烯烃环氧化反应催化性能的研究进展；分析了硼酸树脂、乙烯-丙烯橡胶、螯合树脂、苯并吡咯树脂、聚酰亚胺树脂、聚硅氧烷树脂、阳离子交换树脂和聚苯乙烯等有机聚合物为载体的研究情况；评价了以无机硅酸盐为载体，采用溶胶-凝胶、离子交换、同晶取代等方法负载钼对催化性能的影响；展望了多相化烯烃环氧化钼系催化剂的发展前景。     

Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodiesel

This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.     

Olefin epoxidation with metal-based nanocatalysts

Alkene epoxidations are an important class of reactions carried out in industry; however, current methods are plagued by problems, including high cost, difficulty in recovering catalysts, and generation of large quantities of acidic and chlorinated waste. In recent years, nanocatalysts have been considered as robust, heterogeneous alternatives to homogeneous catalysts. This work evaluates silver- and base metal-containing nanocatalysts as olefin epoxidation catalysts, highlighting the industrial applicability and green aspects of these catalytic systems. The nanocatalysts discussed are mostly supported or composite materials that showed (generally) good activity and selectivity for various/multiple olefin epoxidation reactions.     

Optimisation of olefin epoxidation catalysts with the application of high-throughput and genetic algorithms assisted by artificial neural networks (softcomputing techniques)

An olefin epoxidation Ti catalyst has been optimised by means of high-throughput experimentation involving materials synthesis, postsynthesis treatments, and catalytic testing. Softcomputing techniques for advanced experimental design have been used. The variables explored in the hydrothermal synthesis of Ti-silicate-based catalysts were: concentration of OH⁻, titanium, and surfactant. The probe reaction employed for the optimisation was the solvent-free epoxidation of cyclohexene, with tert-butylhydroperoxide as oxidant. The different catalyst groups detected by clustering analysis were studied by XRD and UV diffuse reflectance. Ti-mesoporous MCM-41 and MCM-48 molecular sieves were among the most active catalysts. The best performing catalysts were tested for epoxidation of different linear olefins.     

Die großtechnische Oxosynthese mit immobilisiertem Katalysator

Industrial Oxo Synthesis with Immobilised Catalyst. The use of water-soluble catalysts represents a significant advance in homogeneous catalysis; “immobilisation” of the catalyst in a second immiscible liquid phase has the effect of “heterogenisation” and allows the advantages of heterogeneous processing (long lifetimes, straightforward technology) to the combined with those of the homogeneous mode (gentle reaction conditions, high activity and selectivity). In particular, the decisive advantage of homogeneous catalysts, viz. the wide range of variation of their steric and electronic properties which can be adapted to the specific reaction at hand, can be exploited for tailoring highly effective catalysts. Moreover, the mode of action of these homogeneous catalysts remains understandable as a model and under the reaction conditions chosen – in complete contrast to the case of many heterogeneous catalytic systems. The first successful industrial application of water-soluble catalysts was in the oxo process of Ruhrchemie/Rhǒne Poulenc. The following article reports on ten years' experience with this process and the HRh(CO)[P(msulphophenyl-Na)₃]₃ catalyst.     

烯烃环氧化催化剂的研究进展

由于烯烃环氧化物在多领域的广泛应用,人们在烯烃的环氧化反应方面做了大量的工作.反应催化剂的研究无疑是工作的重中之重,因为绝大部分的烯烃环氧化反应都是需要催化剂来催化的.均相催化剂由于其不易分离、无法回收、流出液难于处理客易造成污染等缺点,不较多相催化剂研究的少.作者将主要从催化剂方面,尤其是多相催化方面介绍一下烯烃环氧化的研究进展.     

醇还原胺化反应催化剂研究进展

醇还原胺化反应是胺合成最有效、最有应用潜力的方法之一,而催化剂是还原胺化反应的关键。本文详细阐述了Ru、Ir、Pd、Cu、非金属等均相催化剂和Co、Ni、Ru、Pd等非均相催化剂在醇还原胺化反应中的研究进展,介绍了不同催化体系的催化性能和反应规律、应用特点和局限性。指出了均相催化体系的回收使用仍然是阻碍其应用的难题,研究重点应集中在高效、廉价催化体系开发、拓展应用范围和分离回收研究;非均相反应催化剂的专用性强,性能难以满足工业应用需求,加强微观结构及反应机理、高性能催化剂、高压体系中流场状态与过程研究以及提高活性、选择性和稳定性是未来的研究重点。     

Oxidative dehydrogenation of ethane and propane over Mn-based catalysts

The catalytic performances of Mn-based catalysts have been investigated for the oxidative dehydrogenation of both ethane (ODE) and propane (ODP). The results show that a LiCl/MnO_x/PC (Portland cement) catalyst has an excellent catalytic performance for oxidative dehydrogenation of both ethane and propane to ethylene and propylene, more than 60% alkanes conversion and more than 80% olefins selectivity could be achieved at 650°C. In addition, the results indicate that Mn-based catalysts belong to p-type semiconductors, the electrical conductivity of which is the main factor in influencing the olefins selectivity. Lithium, chlorine and PC in the LiCl/MnO_x/PC catalyst are all necessary components to keep the excellent catalytic performance at a low temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Über die Katalyse der PRILEŽAEV-Reaktion

About the Catalysis of the PRILEŽAEV Reaction It is shown that a catalysis of the PRILEŽAEV reaction exists. We investigated the influence of homogeneous molybdenum catalysts on the epoxidation reaction of olefins with percarboxylic acids kinetically. The second order reaction rate data show that the MoO₂(acac)₂ catalyzed cyclohexene epoxidation with peracetic acid runs two times faster than the uncatalyzed reaction and the same epoxidation of oct-1-ene runs 15 to 30 times faster. In the same way the reduction of activation parameters in the catalytic reaction proves the catalytic effect. An influence of catalyst concentration and a formation period at the beginning of the catalytic reaction were observed. The influence of the structure of olefin and of the kind of catalyst were investigated and discussed. A formulation of the transition state is given and discussed in relation to the uncatalyzed PRILEŽAEV reaction and to the Halcon reaction.     

Synthesis of layered crystalline AlSPP and its immobilized chiral salen Mn(III) catalysts applicated in the large scale asymmetric epoxidation of olefins

Chiral salen Mn(III) complex was axially immobilized onto phenoxy-modified organic polymer-inorganic hybrid material layered crystalline aluminium oligo-styrenyl phosphonate-hydrogen phosphate. The prepared catalysts exhibited excellent activities and enantioselectivities for asymmetric epoxidation of unfunctionalized olefins with m-chloroperbenzoic acid as oxidant, especially for the epoxidation of α-methylstyrene (conversion: up to 99 %; ee: exceed 99 %). A point worth emphasizing is that the heterogeneous catalysts afforded remarkable increases of conversions and ee values without adding axial base N-methylmorpholine N-oxide for the asymmetric epoxidation of olefins. The catalyst can be easily recovered and reused with slightly decrease of activity and enantioselectivity after seven cycles. Delightedly, this novel heterogeneous catalyst could also be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which provided the potentiality for application in industry.     

乙炔氢氯化反应无汞催化剂的研究进展

概括评述了前人对乙炔氢氯化反应无汞催化剂结构性能与催化活性关系的研究,并根据金属离子络合能力的差别,分析总结出了碱金属和碱土金属以及其它金属离子可能的催化反应机理。同时从非均相反应体系和均相反应体系两方面综述了国内外无汞催化剂催化乙炔氢氯化反应的研究情况,特别是对金基催化剂的研究,从催化剂的组分、催化机理、失活和再生等方面做了详细概述,对有机溶剂和离子液体做溶剂的均相体系进行了简要评述,并从组分、溶剂、载体等方面对各种无汞催化反应体系将来的开发方向进行了展望。     

杂多酸催化烯烃环氧化的研究进展

烯烃的环氧化物是应用最广泛的有机中间体,在有机合成反应中烯烃的环氧化反应占有十分重要位置。本文主要论述了以杂多酸作为催化剂,季铵盐作为相转移催化剂,以双氧水为氧化剂,在两相条件下催化烯烃环氧化的反应过程。     

工业有机废水深度处理：非均相Fenton催化剂研究进展

在众多水处理技术中,Fenton法能产生具有强氧化性的羟基自由基（·OH）,被认为是处理水中难生物降解有机污染物的有效方法。但是,传统的均相Fenton技术存在响应pH范围窄、催化剂活性组分不易回收分离、产生的铁泥会造成二次污染等问题,而非均相Fenton技术则可有效克服上述缺陷并具有良好工业应用前景。本文评述了Fenton反应,尤其是非均相Fenton技术近年来的发展情况,主要综述了其反应机理、反应活性的影响因素以及非均相Fenton催化剂研究现状。重点结合构-效关系、合成方法与反应机制探讨了国内外铁基与非铁基金属催化剂与碳基催化剂的发展进程以及其对于难降解有机物的处理效果。并总结了双氧水利用率、催化剂稳定性、反应的控速环节对非均相Fenton催化剂体系应用的影响与限制,为进一步改进催化剂的设计与制备方法提供了思路。     

Highly Enantioselective Epoxidation of Unfunctionalized Olefins Catalyzed by Chiral Jacobsen’s Catalyst Immobilized on Phenoxy‐Modified Zirconium Poly(syrene‐phenylvinylphos‐ phonate)phosphate

Chiral Jacobsen’s catalyst was axially immobilized onto phenoxy‐modified zirconium poly(styrene‐phenylvinylphosphonate)phosphate (ZPS‐PVPA). The immobilized catalysts show comparable ee values for asymmetric epoxidation of styrene and much higher ee values for α‐methylstyrene (73.7% vs. 54.0%) and indene (99.9% vs. 65.0%) than the homogeneous Jacobsen’s catalyst. Moreover, the as‐synthesized catalysts are relatively stable and can be recycled at least five times without significant loss of activity and enantioselectivity. A point worth emphasizing is that the heterogeneous catalysts afforded remarkable increases of conversion and ee values in the absence of expensive O‐coordinating axial bases for the asymmetric epoxidation of olefins, especially for the epoxidation of α‐methylstyrene (conversion: from 24.3% to 99.9%; ee: from 29.4% to 73.7%), which may overcome the last obstacle for the potential industry application of chiral Jacobsen’s catalyst.     

Ketone-catalyzed asymmetric epoxidation reactions

This Account summarizes our efforts in developing organic ketone catalysts for enantioselective and diastereoselective epoxidation of olefins. We have developed an efficient and general protocol for epoxidation of olefins using dioxiranes generated in situ from activated ketones and Oxone (2KHSO5.KHSO4.K2SO4) in a homogeneous aqueous solvent system. We have also developed chiral ketone catalysts for highly enantioselective epoxidation of unfunctionalized trans-olefins and trisubstituted olefins. Excellent diastereoselectivities have been achieved for epoxidation of substituted cyclohexenes with ketone catalysts.