Thermophysical and Spectroscopic Studies of Pure 1-Butyl-3-methylimidazolium Tetrafluoroborate and Its Aqueous Mixtures

Intermolecular interactions in the aqueous mixtures of the room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), have been studied. The thermophysical properties: density ρ, speed of sound u, specific conductivity κ and refractive index n _D have been measured over the whole composition range at different temperatures (293.15–323.15 K) and are discussed. The results from thermophysical measurements are explained with the help of spectroscopy. In order to interpret the nature of molecular interactions occurring between [BMIM][BF₄] and water molecules, as well as to identify the moieties in which interactions are taking place, ¹H, ¹³C NMR and FT-IR spectra of the solutions have been studied. Excess molar volume V ^E, excess molar isentropic compressibility $ K_{S}^{\text{E}} $ , partial molar excess volume $ V_{i}^{\text{E}} $ , partial molar excess isentropic compressibility $ K_{S,i}^{\text{E}} $ , deviation in specific conductivity ?κ, and deviation in refractive index ?R have also been determined and analyzed to have a better understanding of the interactions taking place between the different components. Additionally, the excess ultrasonic speed u ^E and excess isentropic compressibility $ k_{S}^{\text{E}} $ , in terms of volume fractions, have been calculated and analyzed. It has been observed that temperature has a significant effect on the thermophysical properties of the studied system. Spectroscopic measurements confirm the disruption of ion-pair interactions of [BMIM][BF₄] and hydrogen-bonded network of water in the aqueous mixture of [BMIM][BF₄].     

Study on the Morphology Feature of 1-Butyl-3-methylimidazolium Tetrafluoroborate Based Ionic Liquid Reverse Microemulsions

The micromorphology of 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄)-in-cyclohexane and bmimBF₄-in-triethylamine ionic liquid microemulsions was investigated by two-dimensional NMR and freeze-fracture transmission electron microscopy. The reverse micelles of Triton X-100/cyclohexane were destroyed by adding bmimBF₄ and reverse microemulsions were induced to form by successively adding bmimBF₄. However, no micelles appeared in triethylamine. But if adding bmimBF₄ to a certain extent, a reverse microemulsion was also formed. The driving force of such aggregations could be attributed to the presence of different types of interactions between Triton X-100 and bmimBF₄. A staggered arrangement of surfactant led to the irregular droplet structure and large aggregate size.     

由四氟硼酸1-丁基-3-甲基咪唑鎓/十二烷基苯磺酸钠/水形成的双水相体系的热力学研究

在298.15 K下使用目测法和浊度法绘制了四氟硼酸1-丁基-3-甲基咪唑鎓([Bmim]BF4)/十二烷基苯磺酸钠(SDBS)/水组成的三元体系相图,得到了一个靠近离子液体和水一侧的狭窄双水相(ATPS)区域。从双水相区域周围选择不同组成的样品,用等温滴定微量热(ITC)方法测定了这些样品中逐滴加入纯水后体系热量的变化,发现随样品中水含量的增加,量热曲线上分别出现了较弱的吸热和放热过程,而且这两个过程的位置与三元相图中双水相的形成和消失的位置基本吻合,这说明ITC对于双水相体系的热力学研究是一种可行有效的方法。实验结果表明,双水相的形成是一个吸热过程(ΔH0),而消失是放热过程(ΔH0)。由于双水相的形成是等温等压下的热力学自发过程(ΔG0),因此可以判断该体系中双水相的形成是一个熵驱动过程,而消失是一个熵-焓共驱过程。     

1-丁基-3-甲基咪唑四氟硼酸盐的热稳定性、平衡蒸汽压和标准蒸发焓

利用非等温、等温热重分析(TG)法,研究了高纯氮气气氛下1-丁基-3-甲基咪唑四氟硼酸盐([bmim][BF4])离子液体的热稳定性、平衡蒸汽压和标准蒸发焓.非等温热重(TG)曲线表明[bmim][BF4]的初始分解温度(Tonset)和最大分解速率对应的温度(Tm)分别为697和734K.然而长期等温TGA研究表明,[bmim][BF4]的最高可使用温度约为513K.另外,利用基于TG的蒸发技术研究了[bmim][BF4]的平衡蒸汽压(pe)与温度的关系并计算了标准蒸发焓.在503-543K温度范围内,离子液体[bmim][BF4]的pe和温度的关系是:lgpe=(16±1)+(-6.85±0.25)×103/T.[bmim][BF4]的标准蒸发焓为(131±5)kJ·mol-1.     

嵌段共聚物L64在1-丁基-3-甲基咪唑四氟硼酸盐离子液体中形成的层状液晶

利用偏光显微镜(POM)、小角X射线散射(SAXS)及傅里叶变换红外(FTIR)光谱技术研究了嵌段共聚物PluronicL64(PEO13PPO30PEO13)(PEO:聚氧乙烯;PPO:聚氧丙烯)在室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐[Bmim][BF4]中的聚集行为.绘制了L64/[Bmim][BF4]体系的相图,当L64浓度介于40%-65%(w,质量分数)之间时,L64可与[Bmim][BF4]形成层状液晶.SAXS结果表明,液晶层间距随L64浓度的增加而降低.温度对液晶微结构影响较大,液晶层间距随温度的升高而增大,极性头截面积则减小.并且,在一定温度范围内,升温可使体系的有序性增强.但是,随温度的进一步升高,[Bmim][BF4]与PEO链段之间的氢键被破坏,双折射现象消失,液晶有序性降低.此外,分析了层状液晶的形成机理,[Bmim][BF4]与L64分子间的氢键作用力、静电作用力以及疏溶剂力是液晶形成的驱动力.     

甲醇对1-丁基-3-甲基咪唑四氟硼酸离子液体结构与性质影响的模拟研究

采用分子动力学模拟方法研究了298.15 K、0.1 MPa下摩尔分数为0.1-0.9 的甲醇对1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])结构与性质的影响. 获得了体系的密度、径向分布函数、配位数、自扩散系数、粘度和电导率, 模拟得到的密度值与实验值符合较好. 结果显示: 体系各组分之间的径向分布函数随甲醇摩尔分数的增加呈规律性变化; 体系内阴阳离子的自扩散系数随着甲醇摩尔分数的增加不断增大; 甲醇的加入削弱了阴阳离子之间的相互作用, 体系粘度随着甲醇摩尔分数的增加逐渐减小, 电导率不断增大. 分析空间分布函数得到体系中各组分的三维空间分布情况.     

Solvent Effect on the Enthalpy of Solution and Partial Molar Volume of the Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate

Enthalpies of solution and partial molar volumes of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined in 15 solvents of different polarity. Very large differences of the enthalpies of solution (????_sol H _IL=38.9?kJ?mol^?1) and partial molar volumes (??V _IL=43 cm³?mol^?1) are nearly the same as observed for lithium perchlorate solutions. These results clearly indicate that the low values of the macroscopic polarity parameters of [bmim]BF₄ do not correspond with the large differences of the intermolecular interactions in IL solutions. The values of the partial molar volume of the cation, $V_{[\mathrm{bmim}]^{+}}$ , were estimated for the first time. The changes of the partial molar volumes, V _IL, reflect mainly the changes of anion volume, $V_{\mathrm{BF}_{4}^{-}}$ . The rate of the Diels?CAlder reaction of 9,10-dimethylanthracene with maleic anhydride in the [bmim]BF₄ medium was nearly the same as in common molecular solvents.     

Effect of Amino Acids on the Phase Behavior of Aqueous Biphasic Systems Composed of 1-Butyl-3-methylimidazolium Tetrafluoroborate and Sodium Citrate

Ionic liquids (ILs) based aqueous biphasic systems (ABSs) have been successfully applied to the extraction and purification of biomolecules. Although much research has focused on the effect of ILs on the phase formation, there are few reports that describe the phase behavior of quaternary IL-based ABS systems using amino acids (AAs) as additives. Here, 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim]BF₄) formed an ABS with sodium citrate (Na₃C₆H₅O₇) with the aid of AAs. The phase behavior and physical properties of the ABS were investigated at 298 K. The capacity of the AA to create the ABS (area of biphasic region) increases with increasing in solubility and decrease with the molecular weight of the ILs and follows the trend glycine?>?l-alanine?≈?l-lysine?>?l-threonine?>?l-proline?≈?l-arginine?>?none. Moreover, the pH of the top and bottom phases containing l-proline as additive are nearly neutral; l-threonine, glycine, and l-alanine result in mildly acidic environments, while l-arginine and l-lysine provide basic pH conditions. The results show that the effects of the addition of the AAs can be considerable and important in the simulation, design calculation and pH control of ABS for efficient separation and extraction processes.     

Effect of Lithium Tetrafluoroborate on the Solubility of Carbon Dioxide in the Ionic Liquid 1-Butyl-3-Methylimidazolium Tetrafluoroborate

In this work, the phase behavior of the ternary system of carbon dioxide +1-butyl-3-methylimidazolium tetrafluoroborate?+?lithium tetrafluoroborate has been investigated. Mixtures of known concentrations of the salt, ionic liquid and carbon dioxide were prepared and their bubble point pressures were measured at different temperatures. Results are reported for this ternary system, at carbon dioxide concentrations of 20.2, 27.6 and 35.2?mol-% and salt concentrations of 0.0, 6.0, 11.5, 16.3 and 21.1?mol-% (on a carbon-dioxide free basis) and within temperature and pressure ranges of 293.15?C358.15?K and 1.2?C11.3?MPa, respectively. It was observed that the addition of the salt increased the bubble point pressure and its effect was concentration-dependent, i.e. at higher concentrations of the salt, higher pressures are required. This behavior is greater at higher temperatures.     

1-乙基-3-甲基咪唑四氟硼酸盐离子液体的量子化学研究

The results of the quantum chemistry study of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM+BF4-) were reported. The ab initio method and density functional theory (B3LYP method) was used to optimize the stable structure of the gas phase ion pair at the level of 6-311++G** basis set, respectively. An IR spectra for EMIM+BF4- were obtained through the vibrational analysis. The changes of atomic charge assignments have been investigated using the Natural Bond Orbital method. The computational results show that there exist hydrogen bonds and other weak interactions between the cation and the anion. Using counterpoise correction method to estimate the basis set superposition error, the interaction energy between the cation and anion is 346.78 kJ/mol.     

Formation of 1-Butyl-3-methylimidazolium Bis(2-ethyl-1-hexyl)sulfosuccinate Stabilized Water-in-1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide Microemulsion and the Effects of Additives

A new strategy is proposed here to formulate a bis(2-ethyl-1-hexyl)sulfosuccinate (AOT^?) stabilized water-in-ionic liquid microemulsion without any additives. Replacing the inorganic counter ion Na⁺ by the organic 1-butyl-3-methylimidazolium ([Bmim]⁺) ion greatly improves the solubility of AOT^? in hydrophobic 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim]Tf₂N) (IL) and favors the formation of water-in-IL (W/IL) microdroplets. The existence of the W/IL microdroplets has been confirmed by dynamic light scattering, Fourier transform infrared absorption spectroscopy and ultraviolet–visible absorption spectroscopy. Also, presented for the first time are the effects of salts and alcohols on the microstructure and water solubilization capacity of the ternary H₂O/[Bmim]AOT/[Bmim]Tf₂N system. For inorganic salts, larger concentrations of the salt and higher charge density of the cation result in smaller microdroplet size and weak water solubilization capacity. For 1-hexanol, a high concentration of this alcohol results in small microdroplet size but high water solubilization capacity. Analyses indicate that the salts compress the electric double layers of W/IL microemulsions, decrease the size of the microdroplets and consequently reduce the water solubilization capacity; the alcohol, however, facilitates the aggregation of AOT^?, increases the number of W/IL microdroplets, and therefore improves the water solubilization capacity of the system.     

离子液体1-烷基-3-甲基咪唑四氟硼酸盐在水溶液中的聚集行为

采用等温滴定量热法、静态荧光猝灭法和电导法系统研究了典型离子液体1-烷基-3-甲基咪唑四氟硼酸盐([Cnmim][BF₄])在水溶液中的聚集行为, 获得了胶束形成的临界胶束浓度(cmc), 摩尔焓变(ΔH_mic), 摩尔吉布斯自由能变(ΔG_mic), 摩尔熵变(ΔS_mic)以及不同浓度时[Cnmim][BF₄]胶束的平均聚集数等基本参数. 发现这类离子液体的聚集为熵驱动, 阳离子的烷基链越长, ΔG_mic越负, 聚集更容易发生. 此外, 结合[C_nmim]X (X=Cl^-, Br^-)的相关研究发现, 阳离子相同时, 体积越大和疏水性越强的阴离子与头基的结合能力越强, 能有效地降低头基之间的静电排斥, 降低cmc, 利于胶束的形成. 对于[C₁₂mim][BF₄], 添加剂β-环糊精(β-CD)的加入可使cmc增大, ΔH_mic和ΔS_mic减小, 而KBF₄则可使cmc和ΔH_mic减小, ΔS_mic增大.     

1-丁基-3-甲基咪唑六氟磷酸盐+水+醇体系的相行为

在298.15 K, 常压下研究了1-丁基-3-甲基咪唑六氟磷酸盐([bmim][PF₆])+水+甲醇、[bmim][PF₆]+水+乙醇、[bmim][PF₆]+水+2-丙醇、[bmim][PF₆]+水+1-丙醇三元体系的相行为. 结果表明, 对于含甲醇、乙醇和2-丙醇的体系, 醇在水+醇溶液中摩尔分数分别为0.55-1.00、0.40-0.75 和0.35-0.50 时, 醇的水溶液与[bmim][PF₆]可以互溶. 而水+1-丙醇体系没有此类现象. 这说明, 这类三元系的相行为不但取决于醇分子的大小, 而且取决于其结构.     

氯化钽在离子液体1-丁基-3-甲基咪唑六氟磷酸盐中电化学行为

采用循环伏安法,研究了0.25 mol/L TaCl₅在离子液体1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF₆)中的电化学行为。 实验结果表明,电沉积钽是受扩散控制、两步骤的不可逆电极反应过程,首先是Ta(Ⅴ)还原为Ta(Ⅲ),其次是Ta(Ⅲ)还原为金属钽和形成其它低价钽氯化物。 Ta(Ⅴ)/Ta(Ⅲ)和Ta(Ⅲ)/Ta在离子液体[Bmim]PF₆中的阴极传递系数分别为0.155和0.406。 Ta(Ⅴ)在离子液体[Bmim]PF₆中的扩散系数为1.629×10^-9 cm²/s。 在100 ℃和-1.25 V条件下,采用恒电势法在铂片上电沉积钽,扫描电子显微镜照片和EDS分析表明,沉积物为钽和钽的低价氯化物。     

微波辐射一锅法合成1-羧甲基-3-甲基咪唑四氟硼酸离子液体

以N-甲基咪唑为原料,微波辐射一锅法合成了1-羧甲基-3-甲基咪唑四氟硼酸离子液体,其结构经1HNMR和IR表征。     

Diffusion dynamics of 1-Butyl-3-methylimidazolium chloride from cellulose filament during coagulation process

The diffusion dynamics of 1-Butyl-3-methylimidazolium chloride ([BMIM]Cl) during coagulation process of cellulose filaments with H₂O as non-solvent were investigated in detail. The diffusion coefficients of [BMIM]Cl was calculated based on the Fick’s second law of diffusion according to the experimental data. Several factors which affect the coagulation process including polymer concentration, concentration and temperature of coagulation bath were discussed respectively. It is found that the diffusion rate of [BMIM]Cl decreased with the increasing polymer content in the spinning solutions and the initial concentration of [BMIM]Cl in the coagulation bath, while the diffusion coefficients increased largely with the coagulation temperature becoming higher. The diffusion coefficients of [BMIM]Cl is relatively lower, in contrast with the conventional solvent in the solution spinning process, which is coordinate with the result of polyacrylonitrile [BMIM]Cl system by Zhang et al. (Polym Eng Sci 48(1):184–190, 2008). Compared with the diffusion process of N-methylmorpholine-N-oxide (NMMO) from cellulose filament, the diffusion coefficients of [BMIM]Cl is lower, which suggested a stronger coagulation and washing conditions should be taken to produce regenerated cellulose fiber with [BMIM]Cl as solvent.     

Fractionation of Wood with Binary Solvent 1-Butyl-3-methylimidazolium Acetate + Dimethyl Sulfoxide

It is suggested to use a binary solvent, 1-butyl-3-methylimidazolium acetate + dimethyl sulfoxide, for full dissolution of wood, followed by its separation into the polysaccharide and lignin components. The optimal conditions of the wood treatment process were determined (temperature 120°C, processing duration 6 h). A scheme is suggested for double-stage fractionation of the lignin?cellulose biomass. The scheme is based on the successive precipitation of the dissolved components with acetone and water. The isolated polysaccharide and lignin fractions constituting, combined, 70% of the initial mass of wood were characterized by IR and NMR spectroscopy, exclusion chromatography, electron microscopy, and functional analysis. It was found that the polysaccharide fraction has the form of amorphous cellulose (2% degree of crystallinity) containing about 15% lignin. The isolated lignin contains no significant admixtures of polysaccharides, has a mass-average molecular mass of about 5 kDa, and is close to organosolvent lignins. It was found that the lignin fraction contains up to 35% residual ionic fluid. A suggestion is made about the possibility of chemical binding between lignin and butyl-3-methylimidazolium cations.     

Synthesis of Cellulose Long-Chain Esters in 1-Butyl-3-methylimidazolium Acetate: Structure-Property Relations

In this study, we prepared cellulose long-chain esters homogeneously in 1-butyl-3-methylimidazolium acetate, using cotton linter as the raw material, long-chain fatty acid as the esterification agent and paratoluensulfonyl chloride as the co-reactant. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction were used to characterize the product. The maximum degree of substitution was found to be 1.53 when the molar ratio of cellulose, lauric acid and paratoluensulfonyl chloride was 1 : 6 : 6, provided that the reaction temperature was 60°C and the reaction time was 24 h. The mechanical property of the free-film made of cellulose laurate was also tested. It was found that the toughness of cellulose laurate was much better than that of cellulose acetate.     

负载1-丁基-3-甲基咪唑氯的固体炭磺酸催化水解纤维素

纤维素作为可再生资源,其催化水解得到的平台化合物对缓解能源压力具有重要的意义。 本文以生物质竹子为原料选择700 ℃预碳化、150 ℃磺化得到的固体炭磺酸为基体,负载1-丁基-3-甲基咪唑氯后得到离子液体功能化固体炭磺酸催化剂。 结果表明,催化剂最优条件下水解纤维素得到的总还原糖产率相对于固体炭磺酸提升了15.2%,循环使用后,依然表现出良好的催化性能。     

Volumetric Properties of Binary Mixtures of the Ionic Liquid 1-Butyl-3-Methylimidazolium Tetrafluoroborate with Aniline

The densities of binary mixtures of an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF₄], with an aromatic compound, aniline, have been determined over the full range of compositions and over the temperature range 298.15 to 313.15 K at atmospheric pressure using a vibrating-tube densimeter (DMA4500). Excess molar volumes ( V_m^EV_{\mathrm{m}}^{\mathrm{E}} ) have been obtained from these experimental results, and were fitted by the fourth-order Redlich–Kister equation. In addition, partial molar volumes, apparent molar volumes and partial molar volumes at infinite dilution have been calculated for each component. Our results show that values of V_m^EV_{\mathrm{m}}^{\mathrm{E}} decrease slightly when the temperature increases in this system. The results have been interpreted in terms of ion-dipole interactions and structural factors of the ionic liquid and the organic molecular liquid.