Microwave-Assisted Esterification of Oleic Acid Using an Ionic Liquid Catalyst

The combination of 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO₄) ionic liquid (IL) and microwave heating was used to esterify oleic acid as a green approach in biodiesel synthesis. To compare the heating systems, conventional heating and the ultrasonic method were employed but the microwave method was found to be more effective. H₂SO₄ and 1-methyl imidazole hydrogen sulfate ([Hmim]HSO₄) were also used in the esterification of oleic acid and their catalytic activities were compared to that of [Bmim]HSO₄. ILs provided some advantages such as reusability, easy recyclability, and very stable activity. There was only a small decrease in the catalytic activity of [Bmim]HSO₄ after four successive applications, which means that ILs can be reused, contrary to homogeneous catalysts. The combination of IL catalysts and microwave irradiation proved to be a potential alternative method for biodiesel production.     

Efficient Heterogeneous Asymmetric Catalysis of the Mukaiyama Aldol Reaction by Silica‐ and Ionic Liquid‐Supported Lewis Acid Copper(II) Complexes of Bis(oxazolines)

Lewis acid complexes based on copper(II) and an imidazolium‐tagged bis(oxazoline) have been used to catalyse the asymmetric Mukaiyama aldol reaction between methyl pyruvate and 1‐methoxy‐1‐trimethylsilyloxypropene under homogeneous and heterogeneous conditions. Although the ees obtained in ionic liquid were similar to those found in dichloromethane, there was a significant rate enhancement in the ionic liquid with reactions typically reaching completion within 2 min compared with only 55 % conversion after 60 min in dichloromethane. However, this rate enhancement was offset by lower chemoselectivity in ionic liquids due to the formation of 3‐hydroxy‐1,3‐diphenylbutan‐1‐one as a by‐product. Supporting the catalyst on silica or an imidazolium‐modified silica using the ionic liquid or in an ionic liquid‐diethyl ether system completely suppressed the formation of this by‐product without reducing the enantioselectivity. Although the heterogeneous systems were characterised by a drop in catalytic activity the system could be recycled up to five times without any loss in conversion or ee.     

Mixtures of Ionic Liquids and Water as a Medium for Efficient Enantioselective Hydrogenation and Catalyst Recycling

In a screening of ligands, ionic liquids and reaction conditions in the Rh‐catalyzed hydrogenation of enamides, a novel multi‐phase reaction system consisting of an ionic liquid (IL) and water (wet ILs) was found to give the most promising results. In many cases such IL/water combinations were superior compared to conventional organic solvents and biphasic ILs/organic co‐solvents media with respect to catalytic performance as well as to catalyst separation and recycling. So far, the best results were obtained with Rh‐ferrocenyl‐diphosphine catalysts (>99% ee). Generally, somewhat lower ees were observed at higher pressure. However, this effect was less pronounced with wet ILs than with conventional solvents. It is shown that IL/water combination allow repeated catalyst recycling without significant loss of activity and that industrially relevant turnover numbers of >10,000 can be obtained.     

离子液体-水复配吸收剂捕获CO2性能

基于绿色合成方法制备出亲水性离子液体(ILs)[NH₂-C₃mim][Br],从有效降低CO₂吸收-解吸操作成本出发,采用ILs-H₂O复配吸收剂,开展了常温加压CO₂吸收及吸收剂常温减压解吸再生实验。结果表明,比CO₂吸收量(基于复配吸收剂或离子液体组分)随复配吸收剂中ILs组分浓度而变;吸收初期,CO₂吸收速率随吸收剂配比变化显著;以CO₂高吸收率和吸收剂低成本为目标,优选出新型水基复配吸收剂(离子液体与水质量比为1.38:1)。分别以水基离子溶液、改良热钾碱液和活化复配醇胺液为吸收剂,在自行搭建的超重力场强化吸收-连续逆流接触(加热或减压)解吸再生台架实验装置上进行了CO₂捕获与吸收剂再生连续化实验。结果表明,在超重力场作用下,改良热钾碱液和活化复配醇胺液对CO₂有较好的捕获,吸收率分别在98%、96%和90%以上,3种吸收剂经加热或减压解吸再生后均可循环回用,水基离子溶液吸收剂在常温减压下解吸更具有实际可操作性。     

离子液体的性质及其在催化反应中的应用

在对离子液体的国内外研究现状综合分析的基础上, 对离子液体的结构–性能关系和性质变化规律进行了探讨, 系统地介绍了离子液体作为溶剂或催化剂在催化反应中的应用, 特别是在金属催化、生物催化、反应–分离耦合方面的进展. 在含微量水或无水离子液体中酶能够保持高的活性和选择性，有望在生物催化方面带来突破性进展. 超临界CO2/离子液体及离子液体/水/有机相提供了一种新的反应–分离耦合模式, 将进一步推动绿色化学的发展.     

离子液体在生物催化中的应用

近年来,离子液体(ILs)以其独特的优势成为生物催化反应研究的热点,尤其是作为生物催化反应的溶剂或共溶剂的研究更是备受关注.许多酶能在ILs或其形成的两相体系或单相体系中保持催化活性.如目前研究最多的脂肪酶,有多种能在ILs中表现出活性稳定、反应选择性提高、产率提高等优良特性;某些蛋白酶在ILs中稳定性提高,具有酯酶的活性;β-半乳糖苷酶在ILs中的催化产率提高;全细胞在ILs中的催化反应效果也较好;但是也有某些酶,如纤维素酶、某些过氧化物酶等在ILs中活性会降低或丧失.因此有关这一方面的研究还有待进一步深入.     

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。     

离子液体结构对Diels-Alder反应的影响

综述了不同结构离子液体对Diels-Alder反应的影响,总结了大量国内外有关离子液体中Diels-Alder反应. 分别从极性、酸性和黏度的角度分析了离子液体结构变化对Diels-Alder反应产物选择性或反应速率的影响. 讨论了离子液体中所能形成的氢键种类、咪唑类阳离子C(2)位取代情况、离子液体的Lewis酸性或Br?nsted酸性、离子液体黏度和反应体系黏度等因素的影响. 采用量子化学密度泛函理论计算了反应活化能、反应物的亲电性和过渡态C?C键长. 结果表明,离子液体的独特结构能降低反应活化能,同时增加反应过程中成键的不协同性. 指出未来的发展方向是通过对离子液体物理性质更深入的研究,基于反应机理合成功能化离子液体,进一步优化反应,发展新型、高效、绿色的Diels-Alder反应,从而扩大其应用.     

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     

碱性离子液体催化单糖脱水制5-羟甲基糠醛

离子液体作为一种新型的环境友好溶剂和液体酸碱催化剂用于单糖脱水制备5-羟甲基糠醛日益成为研究热点,受到广泛重视。以典型的OH-为阴离子的碱性离子液体为催化剂,研究了其对果糖/葡萄糖转化为5-羟甲基糠醛反应的影响。结果表明,在二甲基亚砜中,160℃反应6 h,果糖转化率达90.4%,5-羟甲基糠醛收率为83.3%,5-羟甲基糠醛选择性为92.1%。这一新的碱性离子液体催化单糖脱水的体系,取代了传统酸性催化剂的使用,具有高效、环保、经济的特点,为5-HMF规模化生产奠定了基础。     

Efficient synthesis of benzophenone derivatives in Lewis acid ionic liquids

Benzophenone and its derivatives were prepared via Friedel–Crafts acylation reactions using ionic liquids (ILs) of BmimCl–FeCl₃, BmimCl–AlCl₃ and BmimCl–ZnCl₂ as dual catalyst–solvent. Among them, BmimCl–FeCl₃ showed much higher catalytic activity than that observed for the other two ILs, and in conventional organic solvents. In these reaction systems, good to excellent yields (up to 97%) of acylation products were obtained in a short reaction time. This method features high yield, a simple product isolation procedure, ILs reusability and reduced waste discharge, thus rendering this catalytic system both efficient and environmentally friendly.     

离子液体催化α-烯烃聚合的研究进展

离子液体催化剂具有易分离、可回收、能循环使用等优点，在α-烯烃聚合领域表现出巨大的潜力。本文首先介绍了离子液体的基本物化性质，简述了离子液体催化α-烯烃聚合的反应机理。之后以阳离子结构为基础，详细回顾了路易斯酸型离子液体在α-烯烃聚合反应中的应用，并对其催化活性和产物性质进行了分析。最后，对新型类离子液体催化剂的研究也进行了总结。从报道的结果来看，离子液体催化剂和类离子液体催化剂都已经能够实现较高的产物转化率，但是产物的选择性有待提高，仍然需要更多的实验探索。尽管短时间内还无法取代传统催化剂，但它们已经表现出巨大的应用前景，是未来的研究热点之一。     

Asymmetric Carbon‐Carbon Bond Forming Reactions Catalysed by Metal(II) Bis(oxazoline) Complexes Immobilized using Supported Ionic Liquids

A series of bis(oxazoline) metal(II) complexes has been supported on silica and carbon supports by non‐covalent immobilisation using an ionic liquid. The catalytic performance of these solids was compared for the enantioselective Diels–Alder reaction between N‐acryloyloxazolidinone and cyclopentadiene and the Mukaiyama‐aldol reaction between methyl pyruvate and 1‐methoxy‐1‐trimethylsilyloxypropene. In both reactions the enantioselectivity was strongly influenced by the choice of support displaying enantioselectivies (ee values) up to 40% higher than those conducted under homogeneous reaction conditions.     

负载型离子液体催化剂在催化反应中的应用

负载型离子液体催化剂具有高催化活性、易于分离和环境友好型等特点。综述不同种类负载型离子液体催化剂在不同催化反应中的应用,并展望负载型离子液体催化剂在催化领域的发展方向。     

酸性离子液体催化aldol反应研究

以甲酰胺和氯丙酮等为原料合成了离子液体4-甲基-3-丁基噻唑硫酸氢盐。以aldol反应为探针,探究了离子液体催化苯甲醛与丙酮的缩合反应,并对催化剂用量、醛酮比、反应时间和催化剂重复利用等进行了考察。优化工艺条件为:n(苯甲醛)∶n(丙酮)=1.0∶1.8,催化剂用量3%(n/n),反应时间1.5 h,苄叉丙酮的收率达81.2%,催化剂重复使用5次仍可保持较高催化效果。     

含离子液体乙腈-正丙醇体系的等压汽液平衡

常压(101.3 kPa)下, 测定了如下体系的汽液平衡数据:乙腈-正丙醇-氯化1-苄基-3-甲基咪唑([BzMIM][Cl])、乙腈-正丙醇-溴化1-苄基-3-甲基咪唑([BzMIM][Br])、乙腈-正丙醇-溴化1-己基-3-甲基咪唑([HMIM][Br]), 考察了3种离子液体对乙腈-正丙醇体系相平衡行为的影响。实验结果表明, 3种离子液体都能够提高乙腈对正丙醇的相对挥发度, 3种离子液体提高相对挥发度的顺序为 [BzMIM][Cl] > [BzMIM][Br] > [HMIM][Br]。用NRTL模型对测得的汽液平衡数据进行了关联, 关联结果与实验结果具有良好的一致性。     

基于COSMO-SAC模型的离子液体萃取剂的选择

COSMO-SAC模型是计算无限稀释活度因子的一种有效方法,只需知道分子结构,即可进行有机物或离子液体的无限稀释活度因子计算。COSMO-SAC模型中最耗时的计算步骤是产生σ-图谱(σ-profile)的量子化学计算。利用Materials Studio软件中的DMol3模块,建立了包含32种离子液体阴离子和191种离子液体阳离子的σ-图谱数据库。利用σ-图谱数据库和COSMO-SAC模型,针对离子液体液液萃取过程,提出了离子液体萃取剂的计算机辅助分子设计方法。以乙醇-乙酸乙酯体系为研究对象,选择了适宜的离子液体萃取剂,采用乙醇-乙酸乙酯-离子液体三元体系的液液平衡文献数据进行了验证。     

硅胶固定化离子液体的合成与催化醚化性能

室温离子液体是近年来开发并逐渐应用于有机反应中的绿色溶剂和新型催化剂。将离子液体固定于固相载体上可大大减少离子液体在使用过程中的流失。以硅胶为载体,KH-560为偶联剂合成了烷基硅烷化环氧硅胶,再与N-甲基咪唑在浓硫酸作用下制备硅胶固定化离子液体。探讨了在H 促进下的离子液体对醚化反应的催化性能。实验表明,当仅用浓硫酸催化合成正丁醚时,其产率为34%,当体系中仅加入0.5g离子液体和少量浓盐酸时产率则提高至42%,合成固定化离子液体易回收,可重复利用,当重复使用5次后,正丁醚的产率仍可达37.5%。     

木质纤维素基平台化合物催化转化制备液体燃料及燃料添加剂

随着不可再生的石化资源的不断消耗以及生态环境的不断恶化,可再生资源和能源的开发和利用受到越来越多的重视。木质纤维素是地球上最丰富的可再生生物质资源,蕴藏量和产量巨大,具有广阔的开发利用前景。本文在介绍国内外木质纤维素资源开发利用研究的基础上,结合当今世界生物质能领域的研发现状,分别概述了经由呋喃类化合物及乙酰丙酸等木质纤维素基平台化合物分子,制备液体燃料和燃料添加剂的最新研究进展。在总结归纳合成途径的同时,分析了现阶段面临的主要问题及可能的解决办法,以期能为木质纤维素类生物质能源化利用的研究提供有益的参考与借鉴。     

First Bovine Serum Albumin‐Promoted Synthesis of Enones,Cinnamic Acids and Coumarins in Ionic Liquid: An Insight into the Role of Protein Impurities in Porcine Pancreas Lipase for Olefinic Bond Formation

During studies on exploiting the catalytic promiscuity of crude porcine pancreas lipase (PPL) in ionic liquid for CC bond formations, bovine serum albumin (BSA) was found to be competing for these reactions. After a detailed investigation, we establish that these transformations are possible by unspecific protein catalysis rather than catalytic promiscuity of “PPL” – a first insight into the role of protein impurities in crude enzyme. Thus, a novel and highly efficient, environmentally friendly approach involving synergistic catalysis by bovine serum albumin‐1‐butyl‐3‐methylimidazolium bromide (BSA‐[bmim]Br) has been developed for the synthesis of (E)‐α,β‐unsaturated compounds including a one‐pot cascade synthesis of cinnamic acids and coumarins via aldol, Knoevenagel and Knoevenagel–Doebner condensations.