离子液体在生物柴油合成中的应用研究进展

离子液体具有较强的催化能力、较强的溶解能力、较低的蒸气压等特性,其在生物柴油合成中的应用近年来受到人们的持续关注。本文介绍了离子液体不仅可作为酶催化合成生物柴油的绿色溶剂,作为酯交换反应合成生物柴油的催化剂,还可作为催化剂载体,并可以实现离子液体在生物合成应用中的循环利用。提出了今后应加强对离子液体中固定化脂肪酶催化合成生物柴油的传质过程和催化作用机制及离子液体的循环利用进行研究。     

离子液体催化二氧化碳合成环状碳酸酯的研究进展

概述了以离子液体作为催化剂或作为反应介质,用CO2合成环状碳酸酯的研究进展。离子液体是固定CO2产生环状碳酸酯的适宜催化剂和溶剂,离子液体的话性可以通过添加本身并无活性或低活性的Lewis酸性金属卤化物或金属配合物得到改善。使用离子液体使得合成过程变得更加绿色和简单,因为产品易分离,催化剂可以循环利用,而且不必使用挥发性有害的有机溶剂。     

“绿色”溶剂离子液的研究进展

近年来，离子液由于其独特的优点, 在生物催化及化学合成领域越来越受到青睐。由于缺乏蒸气压，离子液作为绿色溶剂有很大潜能。此外，离子液不像极性有机溶剂那样会使酶失活，因而简化了类似含有糖类这样极性底物的反应。在离子液中，生物催化反应表现出较高的选择性、较快的反应速率和较高的酶稳定性。但这些溶剂还存在着离子液的纯化、控制水活性和pH、高粘度以及产品分离等问题。     

离子液体支撑液膜应用研究进展

离子液体作为一种新型绿色介质,受到研究学者的广泛关注。离子液体具有不易燃、无味、无污染、无蒸汽压、可循环使用等独特性质,被广泛应用于化学化工过程中。离子液体用于膜分离技术具有不易挥发、稳定性好的特点,近来对离子液体在支撑液膜方面的研究备受关注,离子液体支撑液膜在污染性气体的吸收分离方面具有高选择性、高渗透性等优势,在有机物的分离方面具有分离效果明显、耐用性强等优势,在化学反应方面具有催化效率高、可循环使用等优势,本文介绍了离子液体支撑液膜的常用制备方法和膜基材料的选择,探讨了离子液体支撑液膜的稳定性和分离选择性的影响因素,对离子液体支撑液膜在气体分离、有机物的分离、化学反应等方面的应用研究进行了综述。     

Investigation of enzymatic biodiesel production using ionic liquid as a co‐solvent

In this study, the lipase catalysed esterification reaction for biodiesel production was investigated in the presence of the ionic liquid [BMIM][PF₆]. Unlike regular organic solvents, many ionic liquids have no vapour pressure, and are therefore considered non‐volatile. When used in systems with enzyme catalysts, ionic liquids may enhance their activity, selectivity, and stability. The use of an enzyme (lipase) as a catalyst, and the ionic liquid as a solvent/immobilization agent also represents an environmentally friendly, “green” technology. Methyl acetate was used as the acyl acceptor as opposed to the more commonly used methanol due to the negative effects methanol and the glycerol by‐product has on lipase enzyme activity. The results of this research indicate that methyl oleate (i.e., biodiesel) was successfully produced, with an 80% overall biodiesel yield in the presence of ionic liquid, at a 1:1 ratio (v/v) to the amount of oil. This verified that the presence of an ionic liquid, at a specified amount, improved the activity of the lipase and the overall biodiesel yield. Results also indicate the addition of ionic liquid facilitated the separation of the methyl esters from the triacetylglycerol by‐product. The best conditions investigated was found to be: 14:1 molar ratio between oil and acyl acceptor; 20% (w immobilised lipase/w of oil; and a temperature in the range of 48–55°C. However, additional purification is required in order for the produced biodiesel to meet ASTM standards.     

Enhancement of activity and selectivity in lipase‐catalyzed transesterification in ionic liquids by the use of additives

BACKGROUND: Seven ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium cation in combination with hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions were tested as reaction media for lipase-catalyzed transesterification in low water conditions. With the aim of improving the activity and/or selectivity of the lipase, various treatments were applied to ionic liquid media such as equilibration with aqueous solutions of salts, NaHCO₃ or Na₂CO₃, or the addition of a catalytic amount of a non-reactive organic base to the reaction mixture, triethylamine. RESULTS: The treated ionic liquids were shown to be excellent media for lipase-catalyzed ester synthesis by transesterification compared with conventional organic solvents, such as n-hexane. All treatments were found to enhance the synthetic activity of the enzyme, the best results being achieved with the addition of triethylamine. The addition of a catalytic amount of this base to the ILs resulted in a significant increase in both the synthetic activity and selectivity values. For instance, the synthetic activity in [emim⁺][TfN₂⁻] was enhanced more than 12 times and the selectivity increased from 86% to 95% when triethylamine was used. CONCLUSION: These treatments could be easy-to-use approaches to improve the efficiency of enzymatic reactions in ionic liquids when the reaction does not proceed smoothly. Copyright © 2007 Society of Chemical Industry     

Selective dimerisation of 1-butene in biphasic mode using buffered chloroaluminate ionic liquid solvents — design and application of a continuous loop reactor

The dimerisation of 1-butene using (cod)Ni(hfacac) as catalyst has been investigated in different chloroaluminate ionic liquids. Systems prepared by buffering an acidic ionic liquid with weak organic bases proved to be very suitable solvents for the reaction. The reaction takes place in biphasic reaction mode with facile catalyst separation and catalyst recycling. The high intrinsic dimer linearity of catalyst is maintained, but with significant enhancement of catalyst activity and of the selectivity to the dimer product over that observed in toluene solvent. For further investigation, a continuous reactor was designed. Our results in continuous mode show the general technical applicability of the selective Ni-catalysed dimerisation in chloroaluminate ionic liquids using a loop reactor concept.     

离子液体支撑液膜的研究及应用进展

回顾了目前为止离子液体支撑液膜的制备方法、离子液体结构、支撑膜结构对离子液体支撑液膜稳定性的影响因素,介绍了其在有机物分离、气体分离、分离反应耦合方面的应用。由于传统的单元操作很难满足污染和对过程集成的要求,对离子液体支撑液膜在未来实现清洁生产的发展方向进行了展望。     

离子液介质中生物催化与生物转化的研究进展

Ionic liquids have negligibly low vapor pressure, high stability and polarity. They are regarded as green solvents. Enzymes, especially lipases, as well as whole-cell of microbe, are catalytically active in ionic liquids or aqueous-ionic liquid biphasic systems. Up to date, there have been many reports on enzyme-exhibited features and enzyme-mediated reactions in ionic liquids. In many cases, remarkable results with respect to yield, catalytic activity, stability and (enantio-, regio-) selectivity were obtained in ionic liquids in comparison with those observed in conventional media. Accordingly, ionic liquids provide new possibilities for the application of new type of solvent in biocatalytic reactions.     

Ionic liquids in separations

Ionic liquids are liquids composed completely of ions. In the past two decades, ionic liquids have been widely used as "green solvents" replacing traditional organic solvents for organic synthesis and catalysis. In addition, ionic liquids are playing an increasingly important role in separation science. In this Account, the application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.     

离子液介质中生物催化与生物转化的研究进展

Ionic liquids have negligibly low vapor pressure, high stability and polarity. They are regarded as green solvents. Enzymes, especially lipases, as well as whole-cell of microbe, are catalytically active in ionic liquids or aqueous-ionic liquid biphasic systems. Up to date, there have been many reports on enzyme-exhibited features and enzyme-mediated reactions in ionic liquids. In many cases, remarkable results with respect to yield, catalytic activity, stability and (enantio-, regio-) selectivity were obtained in ionic liquids in comparison with those observed in conventional media. Accordingly, ionic liquids provide new possibilities for the application of new type of solvent in biocatalytic reactions.     

离子液体一步法催化合成4-乙酰胺基苯亚磺酸

离子液体作为一类同时具备优良溶剂性能与催化活性的新兴绿色催化剂，在各类反应当中有着广泛的应用。开发了以乙酰苯胺和SO₂为原料，采用离子液体一步法催化原料亚磺化反应合成4-乙酰胺基苯亚磺酸的新工艺，其中离子液体在反应过程中同时作为溶剂与催化剂。考察了多种离子液体一步法合成4-乙酰胺基苯亚磺酸，确定三乙胺盐酸盐/AlCl₃为最适宜离子液体，并进一步考察了三乙胺盐酸盐/AlCl₃自身物质的量配比、反应温度和反应时间等条件对其催化性能的影响；同时探讨了离子液体在反应中真正起催化作用的活性组分是[Al₂Cl₇]^-。离子液体一步法催化合成4-乙酰胺基苯亚磺酸最适宜反应条件为：反应温度为90℃、反应时间为4 h、n（三乙胺盐酸盐）：n（AlCl₃）=0.55：1.00（记为0.55Et₃NHCl/AlCl₃）。在最适宜反应条件下，液相收率达到89.55%。通过IR、LC-MS和¹H NMR等分析对产物结构进行了鉴定。     

Lipase-Catalyzed Esterification

Lipases are versatile catalysts. In addition to their natural reaction of fat hydrolysis, lipases catalyze a plethora of other reactions such as esterification, amidation, and transesterification of esters as well as organic carbonates. Moreover, lipases accept a wide variety of substrates while maintaining their regioselectivity and stereoselectivity. Lipases are highly stable even under adverse conditions such as organic solvents, high temperatures, and so forth. Applications of lipases include production of food additives, chiral intermediates, and pharmaceutical products. Among these, synthesis of various chiral intermediates in pharmaceutical industry and cocoa butter substitutes is being commercially exploited currently.

Lipase-catalyzed esterification and transesterification in anhydrous media (e.g., organic solvents and supercritical fluids) has been an area of major research activity in the past decade or so. Absence of water eliminates the competing hydrolysis reaction. Moreover, substrate specificity, regioselectivity, and stereoselectivity of the enzyme can be controlled by varying the reaction medium. Although organic solvents, which are generally used for lipase-catalyzed reactions, are nearly anhydrous; they contain water in trace quantities. This water content can be controlled over a range and has a profound effect on the activity of lipases. Water not only affects the enzyme but also acts as a competing nucleophile. Enzyme activity has been correlated with thermodynamic activity of water in the medium rather than with the concentration of water. Because lipases are not soluble in most organic solvents, the method of preparation of the enzyme has a strong influence on the enzymatic activity. The major factors are the pH of the aqueous solution in which the enzyme last existed, additives used during preparation, and method of removal of water (e.g., freeze-drying, evaporation, extraction of enzyme into solvent, etc.). Immobilization of lipases allows easy recovery and reuse of the enzyme. Various immobilization techniques have been studied for lipases and some of them have been shown to enhance the activity and stability of the enzyme. Enzyme stability is an important parameter determining the commercial feasibility of the enzymatic process. Various factors, such as temperature, reaction medium, water concentration, as well as the method of preparation, affect the stability of the lipases.

This review deals with fundamental as well as practical aspects of lipase catalysis. A discussion has been presented on various factors affecting lipase activity and stability. Moreover, a brief account of current and potential applications of lipases has been given.     

Ionic-liquid-supported synthesis: a novel liquid-phase strategy for organic synthesis

Soluble ionic liquids have recently been used as supports for catalyst/reagent immobilization and synthesis in homogeneous solution phase. The wide range of ionic liquid supports available makes their use as supports compatible with most common chemistries. The solubility properties of these ionic liquid supports can be tuned by the variation of cations and anions to make them phase separate from less polar organic solvents and aqueous media. The ionic-liquid-supported species can therefore be purified from the reaction mixture by simple washings. Ionic-liquid-supported catalysts and reagents have been prepared and used, and they are easily recovered and reused. Parallel and combinatorial libraries of small molecules have been synthesized. Ionic-liquid-supported synthesis (ILSS) has been applied to the preparation of oligopeptides and oligosaccharides. The comparison of ILSS with solid-phase synthesis, soluble-polymer-supported synthesis, and fluorous phase synthesis has been highlighted where applicable.     

Fischer–Tropsch synthesis in a slurry mode using ionic liquids

The activity of a sodium salt of 4,5-dicarboxyphthalocyanine of cobalt has been studied in Fischer–Tropsch synthesis in a slurry mode (autoclave) using ionic liquids and a mixture of the ionic liquid with perfluorodecaline as solvents. The addition of perfluorodecaline to the reaction mixture resulted in a dramatic increase of the yield of liquid products.     

Enzymatic ring‐opening polymerization (ROP) of polylactones: roles of non‐aqueous solvents

Aliphatic polyesters such as polylactides (PLAs) and other polylactones are thermoplastic, biodegradable and biocompatible polymers with the potential to replace petro‐chemical‐based synthetic polymers. A benign route for synthesizing these polyesters is through the enzyme‐catalyzed ring‐opening polymerization (ROP) reaction; this type of enzymatic process is very sensitive to reaction conditions such as solvents, water content and temperature. This review systematically evaluates the crucial roles of different solvents (such as solvent‐free/in bulk, organic solvents, supercritical fluids, ionic liquids, and aqueous biphasic systems) on the degree of polymerization and polydispersity. In general, many studies suggest that hydrophobic organic solvents with minimum water contents lead to efficient enzymatic polymerization and subsequently high molecular weights of polyesters; the selection of solvents is also limited by the reaction temperature, e.g. the ROP of lactide is often conducted at above 100 °C, therefore, the solvent typically needs to have its boiling point above this temperature. The use of supercritical fluids could be limited by its scaling‐up potential, while ionic liquids have exhibited many advantages including their low‐volatility, high thermal stability, controllable enzyme‐compatibility, and a wide range of choices. However, the fundamental and mechanistic understanding of the specific roles of ionic liquids in enzymatic ROP reactions is still lacking. Furthermore, the lipase specificity towards l ‐ and d ‐lactide is also surveyed, followed by the discussion of engineered lipases with improved enantioselectivity and thermal stability. In addition, the preparation of polyester‐derived materials such as polyester‐grafted cellulose by the enzymatic ROP method is briefly reviewed. © 2017 Society of Chemical Industry     

Improved activity and stability of pseudomonas capaci lipase in a novel biocompatible ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate

BACKGROUND: Enzymes may exhibit enhanced activity, stability and selectivity in ionic liquids, depending on the properties of the liquid. The physical–chemical properties of ionic liquids, however, may be modified by altering the anion or cation in the ionic liquid. This feature is a key factor for realizing successful reactions. In this work, a new ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [i‐C₄mim][PF₆]), was synthesized and investigated as a novel medium for the transesterification reaction of 2‐phenylethanol with vinyl acetate catalyzed by pseudomonas capaci lipase. As contrasts, the reaction was also carried out in two reference solvents; the isomeric ionic liquid [i‐C₄mim][PF₆], 1‐butyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [C₄mim][PF₆]), and hexanes. RESULTS: As reaction medium, [i‐C₄mim][PF₆] was best among the three solvents. The initial reaction rate, the equilibrium conversion of 2‐phenylethanol and the half‐lifetime of the lipase in [i‐C₄mim][PF₆] medium were about 1.5, 1.2 and 3‐fold that obtained in [C₄mim][PF₆] medium, respectively. The lipase in [i‐C₄mim][PF₆] medium was recycled 10 times without substantial diminution in activity. CONCLUSION: The ionic liquid [i‐C₄mim][PF₆] has good biocompatibility, and can be used widely as green media in various biocatalysis reactions to improve the activity and stability of enzymes. Besides hydrophobicity and nucleophilicity, the spatial configuration of ionic liquids is also considered a key factor effecting the behaviour of the enzyme in ionic liquids. Copyright © 2008 Society of Chemical Industry     

用于ATRP反应体系的配位离子液体的合成

在微波反应器中通过有机多胺与氯化1-氯乙基-3-甲基咪唑离子液体[CeMIM]Cl的烷基化反应, 合成了具有配位功能离子液体[N₃MIM]Cl, 以替换传统的有机配体, 与催化剂CuBr配位形成催化体系, 催化离子液体中的原子转移自由基聚合(ATRP)。研究了反应工艺对离子液体合成的影响, 结果发现采用微波反应器加热, 反应时间短, 产物收率高。当反应物配比1.5:1、反应温度为75℃、微波反应3 h时, 产物[N₃MIM]Cl的收率达98.6%。采用电喷雾质谱和红外光谱测定离子液体结构, 证明该离子液体为[N₃MIM]Cl。将所合成配位离子液体替代有机配体, 用于离子液体中MMA的ATRP反应, 结果表明:配位离子液体可提高催化剂在离子液体中的溶解性, 使过渡金属催化剂容易与聚合产物分离。     

离子液体和有机溶剂中薄荷醇催化选择性酯化

研究了离子液体和有机溶剂中(dl)-薄荷醇立体选择性酯化反应。结果表明,在疏水性离子液体[BMIM][PF6]和正己烷介质中的薄荷醇酯化率较高。通过对反应温度、孵育时间和回收次数等影响因素的测定,发现离子液体[BMIM][PF6]作为酶催化反应介质具有比正己烷更大的优势。尤其是酯酶在离子液体中孵育60 d后表现出的活性增大为原来的2.5倍,而正己烷中的酶活性则在两天内变为原来的60%。此外,离子液体在回收利用中表现的优势更说明它作为绿色溶剂替代传统有机溶剂的巨大潜力。     

Enzyme‐catalyzed regioselective synthesis of sugar esters and related compounds

In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry