Syntheses of high molecular weight aliphatic polyesters in 1-alkyl-3-methylimidazolium ionic liquids

High molecular weight aliphatic polyesters were synthesized, for the first time, in 1-alkyl-3-methylimidazolium ionic liquids via two-step polycondensation. An oligoester with diol/diacid ratio higher than unity was essential for achieving high molecular weight product. Moreover, the molecular weight of the resulting polyesters was found to depend on the activity of the catalyst in the ionic liquids and the miscibility of aliphatic polyester/ionic liquid. The former factor was dominated by the anion of the ionic liquids. The latter factor could readily be tuned by varying the anion and/or the cation of the ionic liquids. A clear correlation was found between the miscibility of aliphatic polyester/ionic liquid and the extent to which their solubility parameters matched.     

咪唑型室温离子液体介质中甲苯氯甲基化反应的研究

在溴化N,N-二烷基咪唑型室温离子液体反应介质中,尝试了甲苯、多聚甲醛和氯化氢气体的氯甲基化反应。以[C5mim]Br为催化剂,考察了反应温度、反应时间和离子液体用量对反应转化率的影响,获得的较佳反应条件为:反应温度65℃,反应时间10h,离子液体催化剂用量为甲苯物质的量的4%,在此条件下甲苯的转化率为82.6%,单氯甲基化选择性为100%。随着溴化N,N-二烷基咪唑型室温离子液体烷基链的增长,甲苯转化率有所提高;以溴化N-十二烷基-3-甲基咪唑离子液体为催化剂时,甲苯转化率可达90%,单氯甲基化选择性为100%。反应结束后产物与离子液体自动分层,便于分离。离子液体催化剂重复使用6次,甲苯转化率保持恒定。     

离子液体对Rh(PPh_3)_3Cl催化烯烃硅氢加成反应的影响

对二烷基咪唑类离子液体作为烯烃与三乙氧基氢硅烷硅氢加成反应的介质进行了研究.研究发现,二烷基咪唑类离子液体组成的阴、阳离子不同对烯烃与三乙氧基氢硅烷的反应有一定影响.离子液体为二烷基咪唑六氟磷酸盐时,咪唑环上取代烷基链长的增加,苯乙烯和三乙氧基氢硅烷加成反应中β加成物/α加成物的比值也随之增加.同时,二烷基咪唑类离子液体的阴离子件质也亢接影响了硅氢加成反应的发生.以[Bmim]PF6作为反应溶剂,反应完成后,离子液体催化剂体系可以比较容易地与产物分离,并可以重复使用.     

Alkylation of anthracene to 2-isopropylanthracene catalyzed by Lewis acid ionic liquids

Alkylation of anthracene with 2-chloropropane to 2-isopropylanthracene catalyzed by various Lewis acidic ionic liquids (ILs), such as [Emim]Cl-AlCl₃, [Emim]Cl-FeCl₃, [Emim]Cl-ZnCl₂, [Bmim]Cl-AlCl₃, and [Omim]Cl-AlCl₃ ([Emim]⁺=1-ethyl-3-methylimidazolium cation, [Bmim]⁺=1-butyl-3-methylimidazolium cation, [Omim]⁺=1-octyl-3-methylimidazolium cation,), was investigated. [Emim]C1-A1C1₃ ionic liquid was found to be the most active catalyst in the alkylation. The yield of 2-isopropylanthracene was up to 74.5% and the selectivity of 2-isopropylanthracene was up to 82.9%. The [Emim]C1-A1C1₃ ionic liquid catalyst showed good catalytic activity after running for 6 times. Ease of product separation and the recycling performance of the ionic liquid catalyst is expected to contribute to the development of clean and environmentally friendly strategy for the synthesis of 2-isopropylanthracene.     

室温离子液体1-丁基-3-甲基咪唑六氟磷酸盐的合成研究

由1-甲基咪唑和溴代正丁烷合成了中间体溴化1-丁基-3-甲基咪唑,讨论了温度和反应自身放热对此步反应的影响。中间体再经过阴离子交换,得到了标题化合物,收率为92％。产物的结构经IR和^1HNMR确认。     

微波法合成离子液体1-丁基-3-甲基咪唑四氟硼酸盐的研究

由1-甲基咪唑和溴代正丁烷通过微波法合成了中间体溴化1-丁基-3-甲基咪唑,考察了微波功率和反应时间对此步反应产率的影响。中间体经阴离子交换,得到标题化合物。产物的结构和纯度通过IR1、HNMR和离子选择电极表征。     

Cycloaddition of carbon dioxide to butyl glycidyl ether using imidazolium salt ionic liquid as a catalyst

The catalytic performance of imidazolium salt ionic liquids in the cycloaddition of carbon dioxide to butyl glycidyl ether (BGE) was investigated. The catalytic activity was tested with different imidazolium salt ionic liquids at 60–140 °C under 0.62–2.17 MPa of CO₂ pressure. The imidazolium salt ionic liquid with the cation of bulkier alkyl chain length and with more nucleophilic anion showed higher conversion of BGE. High carbon dioxide pressure and high reaction temperature up to 140 °C was favorable for the high reactivity of the catalyst. The presence of zinc bromide co-catalyst enhanced the reactivity of the imidazolium salt ionic liquid. Kinetic studies with a semi-batch reactor revealed that the reaction could be considered as first order with respect to the concentration of BGE, and the activation energy was estimated as 22.6 and 22.8 kJ/mol for 1-ethyl-3-methylimidazolium chloride (EMImCl) and 1-butyl-3-methylimidazolium chloride (BMImCl), respectively.     

硅胶固定化咪唑酸性离子液体的合成及在酯化反应中的应用

为了减少离子液体用量,缩短反应时间,提高酯化反应的催化效率,该文以硅胶为原料与-γ(2,3-环氧丙氧基)丙基三甲氧基硅烷(KH-560)反应,合成了环氧基硅烷化硅胶,再与1-甲基咪唑硫酸氢盐发生开环反应,制备了一种硅胶固定化1-甲基咪唑硫酸氢盐离子液体。探讨了该离子液体在无机酸促进下对合成乙酸乙酯反应中原料摩尔比、酸的用量及离子液体用量等因素对反应的影响。实验表明,当n(乙醇)∶n(乙酸)=1.5∶1,该固定化离子液体用量为1.00 g,盐酸用量为2.0 mL时,乙酸乙酯的最高产率可达90.0%。固定化离子液体重复使用5次,酯的产率由90.0%降至85.1%。将该固定化离子液体应用于催化乙酸异戊酯、苯甲酸乙酯、草酸二乙酯、乙酸正丁酯和马来酸二乙酯的合成,酯的产率比仅用盐酸单组分催化分别提高了20.4%、25.6%、28.2%、22.3%和16.1%。通过简单滤除就可实现离子液体与产物的分离。     

Salting-out in Aqueous Solutions of Ionic Liquids and K3PO4: Aqueous Biphasic Systems and Salt Precipitation

The salting-out effect produced by the addition of potassium phosphate, K₃PO₄ to aqueous solutions of water-miscible ionic liquids, viz. 1-ethyl-3-methylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium methyl sulfate, or 1-alkyl-3-methylimidazolium chloride (alkyl = butyl, octyl or decyl) is investigated. The effects are analyzed using both the corresponding temperature–composition pseudo-binary and composition ternary phase diagrams. Different regions of liquid-liquid and solid-liquid phase demixing are mapped. The phase behavior is interpreted taking into account the complex and competing nature of the interactions between the ionic liquid, the inorganic salt and water. In the case of solutions containing 1-octyl- or 1-decyl-3-methylimidazolium chloride, the smaller magnitude of the salting-out effects is explained in terms of the possibility of self-aggregation of the ionic liquid.     

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     

Application of Ionic Liquids in the Microwave-Assisted Extraction of Proanthocyanidins from Larix gmelini Bark

Ionic liquid based, microwave-assisted extraction (ILMAE) was successfully applied to the extraction of proanthocyanidins from Larix gmelini bark. In this work, in order to evaluate the performance of ionic liquids in the microwave-assisted extraction process, a series of 1-alkyl-3-methylimidazolium ionic liquids with different cations and anions were evaluated for extraction yield, and 1-butyl-3-methylimidazolium bromide was selected as the optimal solvent. In addition, the ILMAE procedure for the proanthocyanidins was optimized and compared with other conventional extraction techniques. Under the optimized conditions, satisfactory extraction yield of the proanthocyanidins was obtained. Relative to other methods, the proposed approach provided higher extraction yield and lower energy consumption. The Larix gmelini bark samples before and after extraction were analyzed by Thermal gravimetric analysis, Fourier-transform infrared spectroscopy and characterized by scanning electron microscopy. The results showed that the ILMAE method is a simple and efficient technique for sample preparation.     

The use of microwave irradiation for the easy synthesis of graphene-supported transition metal nanoparticles in ionic liquids

Stable ruthenium or rhodium metal nanoparticles were supported on chemically derived graphene (CDG) surfaces with small and uniform particle sizes (Ru 2.2 ± 0.4 nm and Rh 2.8 ± 0.5 nm) by decomposition of their metal carbonyl precursors by rapid microwave irradiation in a suspension of CDG in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The graphene-supported hybrid nanoparticles were shown to be active and could be re-used at least 10 times as catalysts for the hydrogenation of cyclohexene and benzene under organic-solvent-free conditions with constant activities up to 1570 mol cyclohexane × (mol metal)⁻¹ × h⁻¹ at 4 bar and 75 °C.     

介孔载体负载的碱性离子液体催化合成碳酸丙烯酯

采用后嫁接法将碱性离子液体1-丁基-3-甲基咪唑的氢氧化物(［Bmim］OH)分别负载到介孔硅胶、MCM-41分子筛和SBA-15分子筛上制备了非均相负载型离子液体,采用傅立叶变换红外光谱、N2吸附-脱附、元素分析和热重分析等手段对其表征,发现离子液体以共价键嫁接到硅胶上,且有较好的热稳定性。在无溶剂和温和的条件下,以非均相负载型离子液体为催化剂,研究了环氧丙烷与CO2环加成合成碳酸丙烯酯的反应,结果表明,3种非均相负载型离子液体均具有较好的催化性能,其中,［Bmim］OH/SiO₂的催化性能最好,在最优条件下,环氧丙烷转化率可达99.1%,反应后催化剂经过滤即可分离回收利用,多次使用仍保持较高的反应活性。     

Synthesis of 2-Methyl-4-methoxyaniline from o-Nitrotoluene Using Pt/C and Acidic Ionic Liquid as Catalyst System

2-Methyl-4-methoxyaniline (MMA) was synthesized by one-pot method through the hydrogenation and Bamberger rearrangement of o-nitrotoluene in methanol using acidic ionic liquid and 3% Pt/C as catalyst system. The effects of ionic liquid type, dosage of ionic liquid and 3% Pt/C, reaction temperature and reaction pressure on o-nitrotoluene conversion and MMA selectivity were investigated. The results indicated that the imidazolium-based acidic ionic liquid which contains SO₃H-functionalized cation showed higher selectivity to MMA than other acidic ionic liquids used in this work. Using 1-(propyl-3-sulfonate)-3-methylimidazolium hydrosulfate ([HSO₃-pmim][HSO₄]) as the acid catalyst, the selectivity to MMA was as high as 67.6% at 97.8% of o-nitrotoluene conversion. As 3% Pt/C increased from 0.01 g to 0.025 g, the selectivity to MMA decreased from 73.4% to 62.5%, because of the hydrogenation of intermediate o-methyl-phenylhydroxylamine to o-toluidine becoming more dominant. An increase in hydrogen pressure also had obviously dramatic effect in lowering the MMA selectivity. After easy separation from the products, the catalyst system could be reused at least 3 times.     

PEO-imidazole ionic liquid-based electrolyte and the influence of NMBI on dye-sensitized solar cells

1-Oligo(ethylene oxide)-3-methylimidazolium iodide (PEOMImI) was synthesized and applied to dye-sensitized solar cells (DSSCs) by blending it with different 1-alkyl-3-methylimidazolium iodides used as ionic liquid electrolytes. The 1-propyl-3-methylimidazolium iodide (PMII) blend enabled the DSSC to attain a higher solar energy conversion efficiency of 4.52% under a light intensity of 100 mW cm⁻². The addition of N-methylimidazole (NMBI) to the electrolytes increased the conversion efficiency as compared to DSSCs based on NMBI-free electrolytes. The addition of both 1-allyl-3-methylimidazolium iodide (AMII) and NMBI enabled DSSCs to reach their highest solar energy conversion efficiency of 6.14% under a light intensity of 100 mW cm⁻². The ionic conductivity and diffusion coefficient of the triiodide were found to be augmented dramatically after adding NMBI, which leads to an increase in the photocurrent density. The enhancement mechanism of NMBI in the electrolyte was investigated by Raman spectroscopy and differential scanning calorimetry, and it was mainly due to the enhancement of electron exchange in electrolytes.     

[bmim][BF_4]、[bmim][PF_6]离子液体及其与DMF二元体系在293.15～338.15K下的粘度

为获得离子液体与有机物物理性质的数据,常压下,293.15～338.15 K温度范围内,分别测定了1-丁基-3-甲基咪唑四氟硼酸盐（[bmim][BF4]）、1-丁基-3-甲基咪唑六氟磷酸盐（[bmim][PF6]）2种咪唑类离子液体以及它们和N,N-二甲基甲酰胺（DMF）构成的2个二元体系的粘度,采用Vogel-Tamman-Fulcher（VFT）方程和Arrhenius-like方程对所测粘度数据进行关联。结果表明,同一温度下,3种纯溶液粘度大小顺序依次为：DMF〈[bmim][BF4]〈[bmim][PF6]。[bmim][BF4]、[bmim][PF6]离子液体及其与DMF构成的二元体系的粘度均随着温度的升高和DMF摩尔分率的增加而降低。实验条件下,DMF＋[bmim][BF4]和DMF＋[bmim][PF6]二元体系的粘度变化范围分别为1.26～125.5 MPa·s和1.11～165.7 MPa·s。VFT方程对于DMF-[bmim][BF4]与DMF-[bmim][PF6]体系的关联结果比Arrhenius-like方程较好,其总平均绝对误差、总平均相对误差、以及总平均标准方差分别为0.561 9 MPa·s和0.918 6 MPa·s、0.026 8 MPa·s和0.020 9 MPa·s、0.725 5 MPa·s和1.125 1 MPa·s。     

Effect of immobilization of titanocene catalyst in aralkyl imidazolium chloroaluminate media on performance of biphasic ethylene polymerization and polyethylene properties

1-(2-Phenylethyl)-3-methylimidazolium and 1-benzyl-3-methylimidazolium chloroaluminates, [Ph-C₂mim][AlCl₄] and [Bzlmim][AlCl₄], were applied as media of the Cp₂TiCl₂ catalyst for biphasic ethylene polymerization. The studied aralkyl ionic liquids ensure greater stability of the catalyst at higher temperatures and more regular morphology of the produced polyethylene than analogous 1-n-alkyl-3-methylimidazolium chloroaluminates. The alkylaluminium compound participates in the termination reaction of the polymer chain. The catalyst is stable and enables recycling of the ionic liquid phase in the consecutive polymerization reactions. The [Ph-C₂mim][AlCl₄] ionic liquid and AlEt₂Cl alkylaluminium compound turned out to be the most suitable for the biphasic process. The influence of the kind of ionic liquid, alkylaluminium compound (AlEt₂Cl and AlEtCl₂), activator/catalyst molar ratio, reaction temperature, reaction time and catalyst recycling on the polymerization performance as well as polyethylene properties such as molecular weight (M _w ), polydispersity, melting temperature, crystallinity degree, bulk density and particle size is presented.     

Measurement and correlation of vapor-liquid equilibria for a binary system containing 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate and carbon dioxide

Using a high-pressure variable-volume view cell, the vapor-liquid equilibria of the binary system CO₂ and 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate ([BMIM][TDfO]) were determined. The CO₂ mole fraction ranged from 0.104 to 0.952 over a temperature range of 298.2-323.2 K. Both the Peng-Robinson and Soave-Redlich- Kwong equations of state were applied with two different mixing rules to correlate with the experimentally obtained results. Increasing the alkyl chain length in perfluorinated sulfonate anion mother structure from methyl to hexyl markedly increased the CO₂ solubility. To investigate the effect of the number of fluorine atoms in the anion on the phase behavior of imidazolium-based ionic liquid, these experimental results were then compared with those reported in previous experimental studies of 1-alkyl-3-methylimidazolium cations-including ionic liquid+CO₂ binary system.     

碱性离子液体催化Knoevenagel反应研究

合成了碱性离子液体1-丁基-3-甲基咪唑([bmim]OH),研究了其在苯甲醛与氰乙酸乙酯或丙二腈的Knoevenagel反应的应用。实验结果表明:在无溶剂条件下,反应物的物质的量比为1:1,离子液体占反应物的摩尔分数为20%,室温下搅拌,反应时间只需10~30min,产率可达到85%~95%,后处理简单方便,离子液体可重复使用5次。     

High-pressure phase equilibria for the synthesis of ionic liquids in compressed CO2 for 1-hexyl-3-methylimidazolium bromide with 1-bromohexane and 1-methylimidazole

The use of carbon dioxide in the synthesis of ionic liquids (ILs) has many advantages over conventional solvents. Here, the high-pressure phase equilibria (including CO₂ solubility, volume expansion, and mixture critical points) are measured and modeled for the system involved in the synthesis of a model imidazolium ionic liquid 1-hexyl-3-methylimidazolium bromide ([HMIm][Br]) from 1-bromohexane and 1-methylimidazole. The global phase behavior of 1-methylimidazole was investigated and found to be a Type V system (or potentially IV) from the classification of Scott and van Konynenburg with regions of vapor–liquid equilibrium, vapor–liquid–liquid equilibrium, liquid–liquid equilibrium, an upper and lower critical endpoint and mixture critical points. The solubility and volume expansion of CO₂ in 1-methylimidazole, 1-bromohexane, a 1:1 mixture of 1-methylimidazole and 1-bromohexane and [HMIm][Br] was determined at 313.15 K and 333.15 K for pressures ranging from 10 to 160 bar. The solubility of CO₂ and the volume expansion increases in the order of [HMIm][Br]  1-methylimidazole < 1:1 mixture of reactants < 1-bromohexane. The Peng–Robinson equation of state with van der Waals 2-parameter mixing rules was used with estimated critical properties to well correlate the vapor–liquid equilibrium. The results have important ramifications on the kinetics and process constraints of an actual IL synthesis with CO₂.