温度对吡啶离子液体性质影响的分子动力学模拟研究

运用分子动力学模拟方法研究了温度对三种吡啶离子液体[BPy][BF_4]、[HPy][BF_4]、[OPy][BF_4]热力学性质的影响,得到了每个体系的密度、自扩散系数、电导率和黏度等.研究结果表明:随着温度升高,同一种离子液体的密度减小,阴阳离子的自扩散系数明显增大,电导率升高,而黏度降低.在同一温度下,随着阳离子上烷基链的增长,离子液体的密度减小,但热力学性质的变化规律并不完全同步.烷基链长最短的[BPy][BF_4]的自扩散系数和电导率在每个温度下均为最大,而黏度最小;但烷基碳链更长的[OPy][BF_4]和[HPy][BF_4]的各种性质相差不大,甚至当温度大于323 K时,烷基链较长的[OPy][BF_4]的自扩散系数比[HPy][BF_4]的大.     

紫外光谱法检测水中咪唑类离子液体的含量

介绍了用紫外光谱测定水中离子液体含量的方法.测定了7种离子液体([C4 mim][c1]、[C4 mim][BF4]、[C4 mim][PF6]、[c5 mim][Cl]、[C6 mim][BF4]、[C8 mim][Cl]和[C8mIm][BF4])的最大吸收波长,并且绘制了校准曲线.结果表明,在实验试剂用量范围内.离子液体在波长211nm附近的吸光度与浓度呈线性关系,其线性相关系数均大于0.999.说明用紫外光谱法检测水中离子液体含量简单、快速且测定结果准确可靠.     

离子液体[BMP][Tf2N]基本物性的实验研究

针对离子液体[BMP] [Tf_2N]的物性数据缺乏的问题,本文在101.325 KPa下对[BMP] [Tf_2N]在温度范围为278.15～338.15 K的黏度和温度范围为298.15～338.15 K的密度、电导率进行了实验测定,结果表明:黏度、密度和电导率均受温度的影响较大,当压力一定时,[BMP] [Tf_2N]的黏度、密度随温度的升高而减小;而电导率随温度的升高而增大;通过选择分别用Arrhenius方程、自然对数方程和VFT方程关联[BMP] [Tf_2N]的黏度、密度和电导率;结果表明:模型值与实验值的最大相对误差和平均相对误差分别是2.25%和0.94%;5.74%和5.399;4.41%和4.24%。     

液体工质对气液热声发动机性能影响的实验研究

采用气液耦合振动是降低热声发动机谐振频率和提升其压力振幅的一种有效途径。为了研究液体工质对于气液热声发动机性能的影响,本文针对水、室温离子液体[EMIM][BF₄]、20%氯化钾溶液、40%和50%甲酸钾溶液五种液体工质进行了实验研究和分析。实验数据显示,在相同加热功率下,采用50%甲酸钾溶液时系统谐振频率最低,而水工质对应的谐振频率最高;40%甲酸钾溶液的压力振幅最大,而采用离子液体[EMIM][BF4]时系统压力振幅最小。研究结果表明:采用密度较大的液体工质可获得较低的谐振频率,而密度大、黏度小的液体工质则有利于获得更大的压力振幅。     

基于变压红外光谱研究离子液体[MPIM][I]与石墨烯氧化物之间的相互作用

本研究利用红外光谱研究不同压力下离子液体1-Methy1-3-propylimidazolium iodide([MPIM][I])与石墨烯及其氧化物的相互作用.结果表明,[MPIM][I]对压力的变化具有高敏感度,咪唑环与烷基链在0.4 GPa时产生相变化,可明显观察到吸收峰的裂解,且连续加压会导致咪唑环与烷基链的振动频率蓝移.[MPIM][I]与石墨烯作用时加压至2.5 GPa也未观测到相变化的产生,且咪唑环与烷基链的振动频率蓝移趋势也不明显;[MPIM][I]与石墨烯氧化物作用时咪唑环与烷基链的结果与添加石墨烯时几乎相同.石墨烯氧化物具有羟基、羧基、环氧基等共价键结在其表面,这些羟基会扰动[MPIM][I]中的咪唑环与烷基链,导致在常压下振动频率发生蓝移,进而表明石墨烯表面的官能基团会与离子液体产生相互作用.     

离子液体[EMIm]Ac比热容、导热系数及黏度的研究

本文通过实验研究,测定在一定温度范围内,离子液体[EMIm]Ac及摩尔分数分别为0.8、0.6、0.4和0.2的[EMIm]Ac水溶液的比热容、导热系数及黏度。实验结果表明:比热容和黏度受温度影响较大,比热容随温度升高而增大;黏度随温度升高而急剧减小;导热系数受温度影响较小;添加水后,随着水含量的增加即水溶液摩尔分数的减小,比热容增大,相比于纯离子液体,比热容最高增加70%;导热系数最高增加35%;其黏度急剧减小,最高减小82%。本文的研究结果为[EMIm]Ac及其水溶液在吸收式制冷方面的应用研究提供了可靠的数据。     

从常温常压到超临界乙醇的分子动力学模拟

采用分子动力学方法系统地研究了从常温常压到超临界状态乙醇的热力学性质、结构性质和动力学性质.模拟发现随着温度的升高,体系焓值增大,乙醇分子间的氢键作用减弱,自扩散系数增大;随着压强的增大,乙醇分子间的氢键作用增强,自扩散系数减小;乙醇自扩散系数在液相区随温度变化不明显,在气相区随压强增大很快减小,超临界区乙醇的自扩散系数比液相区大十几倍.温度和压强对乙醇自扩散系数的影响可通过密度来体现.与常温常压相比,超临界条件下的乙醇体系因密度涨落存在分子聚集现象,且在低密度区域更显著;乙醇分子间的氢键作用明显减弱,结     

离子液体[BMIM][BF_4]水溶液比热容及热工特性分析

离子液体在化工和能源领域应用研究中,其比热及热工特性尤为重要,然而目前相关的比热数据较缺乏.研究主要对离子液体[BMIM][BF4]及其水溶液的比热容进行了测定.测试系统采用耐驰DSC204HP低温高压差热仪,测试精度较高且稳定可靠.实验测试的温度范围为273.15K~423.15K,测试的离子液体摩尔浓度分别为1.0...     

离子液体[Emim]Br水溶液的密度和超额体积

离子液体作为一种新的环境友好的溶剂,拥有作为吸收式工质对的优良特性.本文对离子液体[Emim]Br及其水溶液的热力学性质进行了研究,使用DMA-55型精密数字密度计测定了[Emim]Br-水二元混合物在298.15 K,308.15K和318.15 K三个温度下全浓度范围内的密度数据,关联得出密度与组成和温度的关系式.计算了三个温度下混合物的超额体积,并用六参数Redlich-Kister方程进行关联.     

离子液体[mmim]DMP-甲醇溶液热物性实验研究

分别采用比重瓶、乌氏黏度计和DSC等设备实验测定了不同浓度的离子液体[mmim]DMP-甲醇溶液在293.15～353.15 K温度范围内的密度、黏度和定压比热容.结果表明:其密度、黏度均随离子液体含量的增大而增大,随温度的升高而降低,而比热容却相反;密度与温度的函数关系符合经典线性经验方程式;黏度可采用Arrheni...     

芘在离子液体及常规溶剂中的激光闪光光解研究

利用纳秒级时间分辨激光光解装置,以Nd:YAG激光器三倍频后的355 nm激光作为激发光源,研究了芘在常规溶剂乙腈、丙酮、环己烷、1-丁基-3-甲基咪唑六氟磷酸离子液体([Bmim][PF6])、N-丁基吡啶四氟硼酸离子液体([BuPy][BF4])以及三乙基庚基铵双三氟甲磺酰亚胺(R4NNTf2)的瞬态光解行为,比较...     

Thermodynamic and transport properties of spiro-(1,1')-bipyrrolidinium tetrafluoroborate and acetonitrile mixtures:A molecular dynamics study

Organic salts such as spiro-(1,1')-bipyrrolidinium tetrafluoroborate([SBP][BF4]) dissolved in liquid acetonitrile(ACN) are a new kind of organic salt solution,which is expected to be used as an electrolyte in electrical double layer capacitors(EDLCs).To explore the physicochemical properties of the solution,an all-atom force field is established on the basis of AMBER parameter values and quantum mechanical calculations.Molecular dynamics(MD) simulations are carried out to explore the liquid structure and physicochemical properties of [SBP][BF4] electrolyte at room temperature.The computed thermodynamic and transport properties match the available experimental results very well.The microscopic structures of [SBP][BF4] salt solution are also discussed in detail.The method used in this work provides an efficient way of predicting the properties of organic salt solvent as an electrolyte in EDLCs.     

离子液体中聚氧化乙烯(PEO)相变过程中的氢键效应

我们把Flory-Huggins模型推广应用到聚合物/离子液体体系,研究聚氧化乙烯(PEO)在离子液体[EMIM][BF_4]中相变过程中的氢键效应,理论模型考虑了三种类型氢键(Ⅰ型:PEO-[EMIM]~+氢键,Ⅱ型:PEO-[BF_4]~-氢键和Ⅲ型:[EMIM]~+-[BF_4]~-氢键)的形成,分析了三种类型的氢键分数随温度、 PEO体积分数的变化.研究发现,三种类型的氢键分数随温度的升高而减少.在较小PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数轻微地减小;在较大PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数急剧减少.Ⅲ型氢键分数随着PEO体积分数的增加而急剧降低.由于三种氢键效应,第二维里系数A_2随温度的增加而减小.通过计算分析不同分子量的PEO在[EMIM][BF_4]中的相图发现,在PEO体积分数较低的条件下,Ⅰ型、Ⅱ型和Ⅲ型氢键是PEO相变的主要驱动力;在PEO体积分数较高的条件下,Ⅰ型和Ⅱ型氢键在PEO相变过程中起到主导作用.     

N-丁基吡啶四氟硼酸盐/水二元体系的分子动力学模拟研究

利用分子动力学模拟方法研究了离子液体N-丁基吡啶四氟硼酸盐([BPy]BF₄)与Tip4p模型水分子的二元体系的微观结构.比较了各组分间的径向分布函数，结果表明随着离子液体比例的增加，水与阴离子、水与阳离子头部吡啶环、阳离子头部与阴离子上相关原子间的径向分布函数峰值都呈现递增的趋势，而阳离子上丁基链末端碳原子间的径向分布函数没有明显变化；空间分布函数则直观地反映出阴离子主要分布在阳离子的吡啶环周围，水分子在阴离子周围近似呈均等分布，且几率随离子液体比例增大而增加；另外还探讨了不同离子液体比例下的二元体系中氢键的数目和寿命，结果均呈现一定规律的变化.     

Mesoporous Silica Materials Synthesized via Sol-Gel Methods Modified with Ionic Liquid and Surfactant Molecules

采用离子液体1-甲基-3-丁基咪唑四氟硼酸盐改性的溶胶-凝胶法以及表面活性剂十六烷基三甲基溴化铵进一步改性的溶胶-凝胶法制备介孔二氧化硅. 通过X射线衍射、氮气吸附脱附和扫描电子显微镜对所制备的样品进行表征. 结果表明,与仅用离子液体为模板制备的介孔二氧化硅相比,采用表面活性剂和离子液体的混合物为模板制备的介孔二氧化硅具有较小的孔径和较规则的孔结构. 说明利用该方法制备介孔二氧化硅,表面活性剂的加入会在一定程度上影响所制介孔二氧化硅的微结构.     

NMR Self-diffusion Study of Amino Acid Ionic Liquids Based on 1-Methyl-3-Octylimidazolium in Water

In comparison with the conventional ionic liquids, water-miscible amino acid ionic liquids (AAILs) are considered as more biodegradable and biocompatible, less toxic, and as able to enhance the biomaterials stability. An application of some long-chain ionic liquids in catalysis, extraction, etc. requests the detailed analysis of ionic and water transport properties of their diluted aqueous solutions close to the area of its critical micelle concentration (cmc). In this work, the molecular transport properties of two 1-methyl-3-octylimidazolium-based AAILs, [C₈mim][Val], and [C₈mim][Leu] (with anions of l-Leucine or l-Valine), in the aqueous solutions were studied by measuring the self-diffusion coefficients and the solution’ viscosities in the temperature ranges 273–343 K at the AAIL’s concentrations below and above its cmc. The data on self-diffusion coefficients of water molecules and cations/anions of AAILs are discussed in terms of activation energies and of hydration effects. Above the cmc, the [C₈mim][Val] molecules demonstrate the strengthening effect on the solvent structure, while the molecules of [C₈mim][Leu] have structure-destructive effect. The results obtained for the relative dynamic viscosities show a decrease of micellar size with increasing temperature. In addition, it was found that the degrees of counterion binding for both AAILs are higher than for 1-methyl-3-octylimidazolium halides.     

Structure,thermodynamic and transport properties of imidazolium-based bis(trifluoromethylsulfonyl)imide ionic liquids from molecular dynamics simulations

Molecular dynamics (MD) simulations have been performed in order to investigate the properties of [C _n mim⁺][Tf₂N^?] (n?=?4,?8,?12) ionic liquids (ILs) in a wide temperature range (298.15?498.15?K) and at atmospheric pressure (1 bar). A previously developed methodology for the calculation of the charge distribution that incorporates ab initio quantum mechanical calculations based on density functional theory (DFT) was used to calculate the partial charges for the classical molecular simulations. The wide range of time scales that characterize the segmental dynamics of these ILs, especially at low temperatures, required very long MD simulations, on the order of several tens of nanoseconds, to calculate the thermodynamic (density, thermal expansion, isothermal compressibility), structural (radial distribution functions between the centers of mass of ions and between individual sites, radial-angular distribution functions) and dynamic (relaxation times of the reorientation of the bonds and the torsion angles, self-diffusion coefficients, shear viscosity) properties. The influence of the temperature and the cation's alkyl chain length on the above-mentioned properties was thoroughly investigated. The calculated thermodynamic (primary and derivative) and structural properties are in good agreement with the experimental data, while the extremely sluggish dynamics of the ILs under study renders the calculation of their transport properties a very complicated and challenging task, especially at low temperatures.