用变阱宽方阱链流体状态方程模拟离子液体相行为

An equation of state (EOS) for square-well chain fluids with variable range (SWCF-VR) developed based on statistical mechanics for chemical association was employed for the calculations of pressure-volume-temperature (pVT) and phase equilibrium of pure ionic liquids (ILs) and their mixtures. The new molecular parameters for 23 ILs were obtained by fitting their experimental density data over a wide temperature and pressure ranges. The molecular parameters of ILs composed of homologous organic cation and an identical anion such as [Cxmim][NTf2] are good linear with respect to their molecular weight, indicating that the molecular pa-rameters of homologous substances, subsequently pVT and vapor-liquid equilibria vapor-liquid equilibria (VLE) can be predicted using the generalized parameter when no experimental data were available. The new set of parameters were satisfactorily used for calculations of the property of solvent and ILs mixture and the solubility of gas in various ILs at low pressure only using one tem-perature-independent binary interaction parameter.     

Hydrogen bond promoted thermal stability enhancement of acetate based ionic liquid

Acetate-based imidazolium ionic liquids(ILs) are of great importance and widely applied in biomass processing and engineering but under stability issue due to the structure self–rearrangement induced by C_2–H deprotonation, by which the IL based biomass processing will be challenging. Herein, we demonstrated that the thermal stability of normal acetate-based imidazolim [C_8C_1Im][OAc] could be significantly improved by changing its cation and anion environment with the presence of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide IL([C_4C_1Im][NTf_2]). When the molar fraction of [C_8C_1Im][OAc] was 0.3, the thermal stability of [C_8C_1Im][OAc] could be significantly improved(ΔT5%dec= + 43 °C). Detailed information obtained from thermal gravimetric analysis(TGA) and nuclear magnetic resonance(NMR) revealed that the addition of [C_4C_1 Im][NTf_2]played a significant role in enhancing the thermal stability of [C_8C_1Im][OAc]. It was proposed that the formation of an anion–π~+ structure network between [C_8C_1 Im][OAc] and [C_4C_1Im][NTf_2] via strong hydrogen bond interactions greatly affects the environment of hydrogen atom in the imidazolium ring of each IL.     

Mechanistic study on the cellulose dissolution in ionic liquids by density functional theory☆

Ionic liquids (ILs) have attracted many attentions in the dissolution of cellulose due to their unique physicochem-ical properties as green solvents. However, the mechanism of dissolution is stil under debate. In this work, com-putational investigation for the mechanisms of dissolution of cellulose in [Bmim]Cl, [Emim]Cl and [Emim]OAc ILs was performed, and it was focused on the process of breakage of cel ulose chain and ring opening using cel obiose as a model molecule. The detailed mechanism and reaction energy barriers were computed for various possible pathways by density functional theoretical method. The key finding was that ILs catalyze the dissolution process by synergistic effect of anion and cation, which led to the cleavage of cellulose chain and formation of derivatives of cel ulose. The investigation on ring opening process of cellobiose suggested that carbene formed in ILs played an important role in the side reaction of cellulose, and it facilitated the formation of a covalent bond between cel-lulose and imidazolium core. These computation results may provide new perspective to understand and apply ILs for pretreatment of cellulose.     

Quality Control of 1-Alkyl-3-methylimidazolium Ionic Liquid Precursors with HPLC

A high performance liquid chromatography (HPLC) method was proposed to monitor the synthesis and purification of the 1-alkyl-3-methylimidazolium ionic liquid precursors from alkylation of 1-methylimidazole with alkyl halides and determine the purity of final products. The results showed that separation of 1-methylimidazole from the precursors could be obtained under the HPLC performance conditions such as cation exchange column, acetonitrile/KH2PO4 aqueous solution and 209 nm wavelength. The content of unreacted 1-methylimidazole in the precursors could be easily calculated from their corresponding HPLC peak areas with the calibration curve of 1-methylimidazole. The retention times of the 1-alkyl-3-methylimidazolium ionic liquid precursors decreased with their increasing alkyls, and the ionic liquids with the same cation and different anions had almost the same retention times.     

Understanding the interfacial behaviors of benzene alkylation with butene using chloroaluminate ionic liquid catalyst: A molecular dynamics simulation

To better understand the benzene alkylation with chloroaluminate ionic liquids(ILs) as catalyst, the interfacial properties between the benzene/butene binary reactants and chloroaluminate ILs with varying cation alkyl chain length and different anions were investigated using molecular dynamics(MD) simulations. The results indicate that ILs can obviously improve the interfacial width, solubility and diffusion of reactants compared to H₂SO₄. The longer alkyl chains of cations...     

借助变阱宽方阱链流体状态方程模拟非电解质体系表面张力和粘度(英文)

The equation of state(EOS)for square-well chain fluid with variable range(SWCF-VR) developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids(ILs).A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation(AAD)of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.     

Molecular dynamics simulation for the binary mixtures of high pressure carbon dioxide and ionic liquids简

Molecular dynamics simulation with an all-atom force field has been carded out on the two binary sys- tems of [bmim][PF6]-CO2 and [bmim][NO3]-CO2 to study the transport properties, volume expansion and micro- structures. It was found that addition of CO2 in the liquid phase can greatly decrease the viscosity of ionic liquids （ILs） and increase their diffusion coefficient obviously. Furthermore, the volume expansion of ionic liquids was found to increase with the increase of the mole fraction of CO2 in the liquid phase but less than 35% for the two simulated systems, which had a significant difference with CO2 expanded organic solvents. The main reason was that there were some void spaces inter and intra the molecules of ionic liquids. Finally, site to site radial distribution functions and corresponding number integrals were investigated and it was found that the change of microstructures of ILs bv addition CO2 had a great influence on the orooerties of ILs.     

Research progress in ionic liquids catalyzed isobutane/butene alkylation

The complicated reaction mechanism and the character of competitive reactions lead to a stringent requirement for the catalyst of C4 alkylation process. Due to their unique properties, ionic liquids (ILs) are thought to be new potential acid catalysts for C4 alkylation. An analysis of the regular and modified chloroaluminate ILs, novel Br?nsted ILs and composite ILs used in isobutane/butene alkylation shows that the use of either ILs or ILs coupled with mineral acid as homogeneous catalysts can help to greatly adjust the acid strength. By modifying the struc-tural parameters of the cations and anions of the ILs, the solubility of the reactants could also be adjusted, which in turn displays a positive effect on improving the activity of ILs. Immobilization of ILs is an effective way to mod-ulate the surface adsorption/desorption properties and acid strength distribution of the solid acid catalysts. Such a process has a tremendous potential to reduce the deactivation of catalyst and enhance the activity of the solid acid catalyst. The development of novel acid catalysts for C4 alkylation is a comprehensive consideration of acid strength and its distribution, interfacial properties and transport characteristics.     

Molecular Simulation on Microstructure of Ionic Liquids in Capture of CO_2

Molecular dynamic simulation is used to study the microstructure of four kinds of ionic liquids (ILs), [Emim]PF6, [Emim][Tf2N], [PC6,6,6,14]PF6 and [PC6,6,6,14][Tf2N] in the capture process of CO2. Radial distribution function (RDF) and spatial distribution function (SDF) are used to analyze the microscopic properties of these systems. The calculated results show that the space distribution of CO2 around ILs determines the capability of ionic liquids for capturing CO2. Based on the analysis of SDF, CO2 and PF6- are overlapped partially around [Emim]+ in [Emim]PF6-CO2 mixture. When the anion is [Tf2N]-, cations are mainly distributed on one side of [Tf2N]- near N atom, and CO2 is concentrated on two sides near the fluoroalkylgroup (?CF3), and there is little overlapped district between cation and CO2. In [PC6,6,6,14]PF6-CO2 mixture, layered structure is found and CO2 is much nearer to PF6- than [PC6,6,6,14]+. Based on the analysis of RDF, in the phosphonium-based ILs, the highest distribution densities of anions and CO2 around cations are about 6 and 3 times as their average ones respectively, while in the imidazolium-based ILs, they are about 3 and 2 respectively, this means that the distributions of CO2 and anions around the imidazolium-based ILs are more evenly distributed than those around the phosphonium-based ILs.     

The second evolution of ionic liquids: from solvents and separations to advanced materials--energetic examples from the ionic liquid cookbook

In this Account of the small portion of the recent research in ionic liquids (ILs) by the Rogers Group, we fast forward through the first evolution of IL research, where ILs were studied for their unique set of physical properties and the resulting potential for tunable "green solvents", to the second evolution of ILs, where the tunability of the cation and anion independently offers almost unlimited access to targeted combinations of physical and chemical properties. This approach is demonstrated here with the field of energetic ionic liquids (EILs), which utilizes this design flexibility to find safe synthetic routes to ILs with high energy content and targeted physical properties.     

Physical and electrochemical properties of room-temperature dicyanamide ionic liquids based on quaternary phosphonium cations

The physicochemical and electrochemical properties of room temperature ionic liquids based on quaternary phosphonium cations together with a dicyanamide anion are presented in this report. The most dicyanamide-based phosphonium ionic liquids prepared were hydrophilic, except ionic liquids containing a long alkyl chain in the phosohonium cation. It was found that asymmetric phosphonium cations gave low-melting salts in combination with a dicyanamide anion. The dicyanamide-based phosphonium ionic liquids exhibited relatively low viscosities and high conductivities when compared to those of the corresponding ammonium ionic liquids. Particularly, the ionic liquids containing a methoxy group in the phosphonium cations indicated very low viscosities. Comparatively good electrochemical stability of the dicyanamide-based phosphonium ionic liquids was confirmed by voltammetric measurements. The thermogravimetric analysis suggested that the dicyanamide-based phosphonium ionic liquids showed higher thermal stability than those of the corresponding ammonium ionic liquids, indicating an improving effect of the phosphonium cations on the thermal stability.     

Synthesis and physical property characterisation of phosphonium ionic liquids based on P(O)2(OR)2 and P(O)2(R)2 anions with potential application for corrosion mitigation of magnesium alloys

Phosphonium cation based ionic liquids (ILs) have become of interest due to their unique chemical and electrochemical stability as well as their promising tribological properties. At the same time, interest has also grown in the use of phosphate and phosphinate based ionic liquids for corrosion protection of reactive metals. In this work we describe the synthesis and characterization of six novel ionic liquids based on the tetraalkylphosponium cation coupled with organophosphate and organophosphinate anions and their sulfur analogues. The conductivity and viscosity of these ILs has been measured and discussed in terms of the nature of the interactions, effect of anion basicity and the extent of ionic character. The reaction of the IL with a ZE41 magnesium aerospace alloy surface is also demonstrated.     

Studies on Thermal Properties of Selected Aprotic and Protic Ionic Liquids

Abstract

We describe herein the thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) investigations of the thermal properties of selected room-temperature ionic liquids (RTILs). The dependence of the thermal properties on both cation and anion structures of RTILs was systematically studied. The ionic liquids (ILs) investigated here include 28 different imidazolium-based ILs, 22 ammonium-based ILs, and 16 amide-based ILs. In general, these three cation classes exhibit different thermal behaviors but follow a quite systematic trend as expected from the corresponding structural variation. The ILs with bromide as the conjugate anion have lower thermal stabilities than those with bis(trifluoromethane sulfonyl) imide or bis(perfluoroethyl sulfonyl) imide as the conjugate anion. The mass of TGA samples and scan rate were found to have a systematic effect on the decomposition temperature of ILs, highlighting the caution needed in reporting TGA results.     

Anion-based regulating mechanism of structural and diffusive property of ionic liquids

Understanding the regulating mechanism of diffusive properties of ionic liquids (ILs) is vital for their practical chemical engineering applications. Herein, we investigate the regulating mechanism of three properties, the structural, thermodynamical, and diffusive properties, of imidazole ILs with 18 kinds of anion via molecular dynamics simulations combined with theoretical analysis. It shows that the radial distribution function and coordinate number for these 18 ILs are similar to each other. However, the vibrational spectrum and diffusive property change greatly with the anion structure, in which the self-diffusive coefficient (SDC) even changes by an order of magnitude. Furthermore, free energy and entropy have an exponential relationship with SDC, while other structural properties or cation–anion correlations cannot be directly related to SDC. These quantitative relationships suggest that entropy or free energy can serve as the key indicators in designing functional ILs for high-performance applications in the chemical engineering field.     

Ionic Liquids as Size‐ and Shape‐Regulating Solvents for the Synthesis of Cobalt Nanoparticles

Over the last few years, ionic liquids (ILs) have emerged as an important class of reaction media for the synthesis of nanoparticles. The formation and stabilization of nanoparticles was investigated in different ILs to elucidate the effect of the chemical nature of the IL anion, cation and alkyl side chain of the imidazolium. In this context, Co₂(CO)₈ was employed as a precursor and thermally decomposed to the metallic cobalt nanoparticles in a series of selected ILs, where either the IL cation or anion was varied while keeping all of the other parameters constant. The results show that both the molecular volume of the anion and cation and the steric configuration are important aspects to control the formation and stability of nanoparticles in ILs.     

Bis(trifluoromethylsulfonyl)imide Ionic Liquids Applied for Fine-Tuning the Cure Characteristics and Performance of Natural Rubber Composites

The goal of this work was to apply ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide anion (TFSI) for fine-tuning the cure characteristics and physico-chemical properties of elastomer composites based on a biodegradable natural rubber (NR) matrix. ILs with TFSI anion and different cations, such as alkylpyrrolidinium, alkylammonium, and alkylsulfonium cations, were applied to increase the efficiency of sulfur vulcanization and to improve the performance of NR composites. Thus, the influence of ILs on the vulcanization of NR compounds, as well as crosslink density and physical properties of NR vulcanizates, including tensile properties, thermal stability, and resistance to thermo-oxidative aging was explored. The activity of ILs seems to be strongly dependent on their cation. Pyrrolidinium and ammonium ILs effectively supported the vulcanization, reducing the optimal vulcanization time and temperature of NR compounds and increasing the crosslink density of the vulcanizates. Consequently, vulcanizates with these ILs exhibited higher tensile strength than the benchmark without IL. On the other hand, sulfonium ILs reduced the torque increment owing to the lower crosslinking degree of elastomer but significantly improved the resistance of NR composites to thermo-oxidation. Thus, TFSI ILs can be used to align the curing behavior and performance of NR composites for particular applications.     

Ionic liquids based on guanidinium cations and TFSI anion as potential electrolytes

Sixteen new guanidinium salts based on small cations and TFSI⁻ anion were prepared and characterized. Physical and electrochemical properties of these products, including melting point, thermal stability, viscosity, conductivity and electrochemical window were investigated. Reducing symmetry of cations can reduce the melting points, and 12 products are liquids at room temperature. The viscosities of cg22TFSI, cg12TFSI and cg13TFSI were 45, 46 and 52 mPa s at 25 °C, respectively. Electrochemical and thermal stabilities of these ILs permitted them to become promising electrolytes used in electrochemical devices.     

螯合型离子液体：合成、性质以及应用

配位型离子液体在过去一段时间内得到了广泛的关注。其中,螯合型离子液体因其存在多个配位点,因而可以通过螯合作用增强金属与配体的相互作用。根据金属在分子中所处的位置,可以将螯合型离子液体分为4种类型：阳离子螯合型离子液体、阴离子螯合型离子液体、阴阳离子螯合型离子液体和中性螯合型离子液体。对近年来报道的螯合型离子液体的合成、物理性质及其应用进行了综述,阐述了其存在的问题、面临的挑战和今后研究的方向。     

PEG基功能化离子液体的脱硫性能

合成一系列含有长醚链的PEG基咪唑对甲苯磺酸盐(PEG基功能化离子液体), 检测其脱硫与再生性能, 并测定其脱硫过程中物性(密度、黏度和表面张力)变化。结果表明, PEG基功能化离子液体具有良好的脱硫与再生性能, 而且该离子液体的脱硫性能随醚链增长而增强, 20℃时SO₂与离子液体摩尔比达到5.51以上, 吸收的SO₂在80℃条件下可彻底解吸。由¹H NMR图谱和Raman光谱分析结果表明, PEG基咪唑功能化离子液体对SO₂的吸收为物理吸收。脱硫后的PEG基功能化离子液体密度增大, 表面张力减小, 黏度较脱硫之前显著降低。