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.     

气液耦合振动对热声发动机性能的影响

进行了气液耦合振动驻波型热声发动机定量模拟.重点比较分析了单纯气体振动系统和引入[EMIM][BF_4]室温离子液体作为液体活塞的气液耦合振动系统的运行参数,并考察了液体活塞的质量对热声发动机谐振频率、压力振幅以及板叠热端温度等的影响.     

高分子凝胶体积相变中的氢键作用

我们把关联模型(association models)推广应用到高分子凝胶体系,研究高分子与溶剂分子间的氢键和溶剂分子与溶剂分子间的氢键在高分子凝胶体积相变中的作用.首先通过分析凝胶体积分数与温度的关系发现,由于两种氢键作用,随着温度变化高分子凝胶出现连续、不连续体积相变,结果表明在体积相变过程中两种氢键都起着重要作用.其次,对不同氢键分数条件下的旋节线的研究发现,对于高分子凝胶体积相变中出现的UCST和LCST(上临界共溶温度和下临界共溶温度)现象也是由于高分子与溶剂分子间氢键和溶剂分子与溶剂分子间氢键共同作用的结果.     

[EMIM][A_C]在高压下的比定压热容

离子液体1-乙基-3-甲基咪唑醋酸盐([EMIM][A_C])广泛应用于化学分离过程,但其在高压下的比定压热容数据比较缺乏。本文基于流动型量热法建立了一套可适用于高压流体比定压热容测量的实验系统,温度、压力、比定压热容的扩展不确定度分别为0.05 K,13 kPa和0.98%。利用该实验系统对[EMIM][A_C]在T=(303~393)K、p=(0.1~16)MPa范围内的比定压热容进行了测量。基于测量结果,建立了一个可以精确计算[EMIM][A_C]比定压热容的新公式。     

液体离子提取烟梗木质素的研究（英文）

本文研究了在温和的条件下利用四种离子液体对烟梗木质素的提取过程,结果表明1-乙基-3-甲基咪唑磷酸二乙酯盐([EMIM][DEP])的提取效果最佳.通过80℃的热水搅拌30 min的预处理过程可以有效脱除烟梗中含有的绝大多数糖分同时疏松了烟梗的微纤维结构,在此基础上使用[EMIM][DEP]在150℃和反应时间4 h的条件下可以获得纯度90.21%的木质素,木质素的提取率达到85.38%.     

液体离子提取烟梗木质素的研究

本文研究了在温和的条件下利用四种离子液体对烟梗木质素的提取过程,结果表明1-乙基-3-甲基咪唑磷酸二乙酯盐([EMIM][DEP])的提取效果最佳. 通过80 °C的热水搅拌30 min的预处理过程可以有效脱除烟梗中含有的绝大多数糖分同时疏松了烟梗的微纤维结构,在此基础上使用[EMIM][DEP]在150 °C和反应时间4 h的条件下可以获得纯度90.21%的木质素,木质素的提取率达到85.38%.     

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][BF4]、[HPy][BF4]、[OPy][BF4]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][BF4]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][BF4]和[HPy][BF4]的各种性质相差不大,甚至当温度大于323K时, 烷基链较长的[OPy][BF4]的自扩散系数比[HPy][BF4]的大.     

基于FLUENT的液氮相变传热的数值模拟

为了给枪械中液氮相变容器结构的设计提供参考,文中采用FLUENT中mixture混合模型,通过UDF实现了密闭容器中液氮相变传热的数值模拟,分析了不同温度、传热面积和长径比对容器中压强和氮气体积分数的影响。根据数值模拟可知,随着温度和传热面积的增加,容器中压强和氮气体积分数都增大;随长径比的增大,容器中压强增大,而氮气体积分数减小。     

磁驱动斜波加载下铋的Ⅰ-Ⅱ-Ⅲ相变实验

设计了一套与磁驱动斜波加载实验装置CQ-4配套的样品预设温度系统,温度范围为室温至180℃。利用此装置联合双源光外差测速系统,完成了不同初始温度下铋的斜波压缩相变实验,并在单发实验中获得了同时含有Ⅰ-Ⅱ和Ⅱ-Ⅲ两次相变信息的速度剖面。实验结果显示,随着铋的初始温度从室温提高到148℃,Ⅰ-Ⅱ相变和Ⅱ-Ⅲ相变起始对应的特征拐点速度分别从251.6和275.7m/s下降到239.4和259.7m/s。     

基于相变材料的动力电池热管理数值模拟

锂离子动力电池经过多次充放电循环后,不可避免出现老化现象,单体电池局部温差增大,成组效应更加明显.本文建立了非均匀产热动力电池组三维模型,采用数值模拟的方法,模拟分析了基于相变材料的圆柱形LiFePO_4动力电池模块(4×6)的降温与均温性能。结果表明,相比没有填充PCM情况,填充PCM后,最高温度随时间呈现先明显增加后逐渐平缓的趋势,放电结束时明显降低,但随着导热系数的增加,最高温度降低不明显。在单体电池固有较大温差情况下,采用StyleⅠ方式排列电池正负极,降低相变温度和增加导热系数均难很好地控制电池模块温度均匀性。对于正负极出现产热不均匀的老化电池组,采用styleⅡ或styleⅢ排列方式是必要的。     

Dynamics of conformations,hydrogen bonds and translational diffusion of poly(methacrylic acid) in aqueous solution and the concentration transition in MD simulations

The dynamic behaviour of chain conformations, hydrogen bonds and translational diffusion of aqueous poly(methacrylic acid) (PMA) solution as a function of polymer volume fraction Φ_p across dilute to concentrated regimes inclusive of the pure polymer amorphous state was studied by molecular dynamics simulations. The behaviour of the relaxation time (τ) of the backbone dihedral angle auto-correlation function (ACF) reveals slower relaxation at higher level of polymer concentration and the existence of a concentration-driven relaxation transition for the aqueous polymer solution which occurs in the polymer volume fraction range, specifically 54% < Φ_p < 82% for this system. The relaxation constant τ for backbone dihedral angle exhibits a linear variation with Φ_p, indicating a first-order kinetic transition. The intermittent ACF for decay of the H-bond correlation shows that H-bonds among water molecules relax faster than those of the PMA–PMA and PMA–water type. The relaxation rate of PMA–water H-bonds shows a decrease up to Φ_p = 72% and becomes faster at Φ_p = 82% due to the confining influence of neighbouring PMA chains. PMA–water and water–water H-bond dynamics show transitions around Φ_p = 72% PMA. With increase in Φ_p PMA diffusion coefficient decreases exponentially and water diffusion coefficient decreases linearly, in agreement with experimental observations using fluorescence and nuclear magnetic resonance (NMR) spectroscopic studies.     

Research for improvement on the extract efficiency of lignans in traditional Chinese medicines by hybrid ionic liquids: As a case of Suhuang antitussive capsule

Recently, efficient extraction of natural products from traditional Chinese medicines (TCMs) by green solvents is deemed an essential area of green technology and attracts extensive attentions. In this work, a green protocol for simultaneous ultrasonic-extraction of the native compounds with different polarities of TCMs by using a hybrid ionic liquids (HILs)-water system was reported for the first time. As a case study, three superior ILs (1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), and 1-allyl-3-methylimidazolium chloride ([AMIM]Cl)) were chosen as the compositions of the HILs system, and the TCMs Suhuang antitussive capsule (SH) containing different-polarity lignans was selected. Primarily, an ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UPLC-QqQ-MS/MS) method in the multiple reaction monitoring (MRM) mode was established for qualitative and quantitative analysis of 18 lignans. After majorization by uniform design experiment, the HILs prepared with [AMIM]Cl, [EMIM][BF4], and [EMIM][OAc] at a volume ratio of 1:5:5 could simultaneously extract multi-polarity lignans compared to single IL. Subsequently, the conditions of ultrasonic extraction employing with HILs and traditional organic solvent were optimized by the response surface methodology, respectively. The results indicated that the extract efficiency of the HILs system for target compounds was significantly improved compared with the traditional organic solvent-extraction, i.e. the content of total lignans in ethanol system was up to 47 mg/g, while that in the HILs system was up to 69 mg/g, with an increasing of 47%. Additionally, ¹H-NMR and ¹³C-NMR spectra were used to characterize the hydrogen-bond interactions in the HILs-lignan mixtures. Extraction with the HILs in TCMs is a new application schema of ILs, which not only avoids the use of volatile toxic organic solvents, but also shows the potential to be comprehensively applied for the extraction of bioactive compounds from TCMs.     

Structure-dependent magnetic susceptibility of sharp poly(ethylene oxide) fractions

Nine sharp fractions of poly(ethylene oxide) (PEO) glycol with number-average molar masses (M _n) in the range from 0.6 × 10³ to 20 × 10³ (PEO-0.6 to PEO-20) were characterized by magnetic susceptibility χ measured in the temperature interval 293 K to 378 K. In contrast to the liquidlike PEO-0.6 with temperature-invariant χ, the values of χ for each of the remaining solid samples, after the initial increase, exhibited two plateaus separated by a relatively narrow temperature interval of their second increase. The jumps of χ at lower and higher temperatures were attributed to a solid-state transition of unspecific nature and to the melting of the crystal fraction, respectively.

The temperature-invariant values of χ_n in the melt state above T _m pass through a minimum for the sample PEO-2.0 and then increase again with (M_n) to a limiting value χ_∞ = ?0.622 × 10^?6. It is concluded that a considerable contribution of the molar-mass-dependent “paramagnetism” χ_P = χ ^? χ_d (where χ_d is the diamagnetic contribution estimated by Kirkwood's equation) to the total magnetic susceptibility of PEO fractions reflects distortions of the spherical symmetry of the electron shells around chain atoms resulting from the discontinuous change of both inter- and intrachain interactions as the (M_n) increases through and above the critical crossover molar mass (M_cr ) = 2 × 10³.     

Switching of hydrogen bonds of water in ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate

We have investigated temperature‐induced Raman spectral changes of deuterated water in an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]), between room temperature and 77 K. The comparison of the OH and OD stretching vibrational spectra at 77 K shows that the strength of the hydrogen bonds in [bmim][BF₄]–water mixtures strongly depends on the type of water, i.e. H₂O and D₂O. In the [bmim][BF₄]–D₂O system, remarkably strong hydrogen bonds form at low temperatures, but they switch to nearly free hydrogen bonds on heating. Copyright © 2013 John Wiley & Sons, Ltd.     

红外光谱法和量子化学法对离子液体提取水中壬基酚的机理研究

采用红外光游法和毓子化学计算法(密度泛函B3LYP方法),分别对常见离子液体1-甲基-3-丁基咪唑六氟磷酸盐和含羟基的咪唑型离子液体提取水环境中的壬基酚的提取机理进行了研究.研究结果显示常见离子液体与壬基酚相互作用前后的红外谱图上没有氢键存在的迹象,而含羟基的离子液体在与壬基酚作用后其羟基峰发生了明显的红移.量子化学计...     

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...     

1-乙基-3-甲基咪唑四氟硼酸盐离子液体的量子化学研究

采用量子化学的从头算(abinitio)和密度泛函(DFT)方法,在6311++G计算水平上研究了离子液体1乙基3甲基咪唑四氟硼酸盐在气相模型下的离子对结构.经振动分析得到了离子对的红外谱,并利用自然键轨道(NBO)分析了阴阳离子与离子对的电荷布居差异.计算结果表明,离子对中存在氢键等弱相互作用.运用Counterpoise方法消除基组重叠误差,得到阴阳离子间的相互作用能为346.78kJ/mol.     

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.