A Vibrational Spectroscopic Study of Ion Solvation in Lithium Perchlorate/Propylene Carbonate Electrolyte

Abstract

The infrared (IR) and Raman spectra of propylene carbonate (PC) containing various concentrations of LiClO₄ have been measured and analyzed. The difference in spectra of PC with and without LiClO₄ was attributed to the interaction of the PC molecules and lithium ions. This interaction occurs mainly on the carbonyl oxygen atom of the PC molecule. The ring deformation, symmetric ring deformation, carbonyl stretching and stretching of ring oxygens for PC are sensitive to this interaction. The solvation number of Li⁺ is also calculated. On the other hand, the structure of the ClO^? ₄ is also affected by PC molecule, forming the solvent separated ion pairs.     

超临界条件下碳酸乙烯酯的均相催化合成

合成了几种四齿Schiff碱铝配合物，并用其在超临界条件下均相催化二氧化碳和环氧乙烷反应合成碳酸乙烯酯。其中，以轴向为乙氧基链的Schiff碱铝配合物的催化活性最高。在一定条件下，由于环氧乙烷与超临界二氧化碳具有混溶性，使得环加成反应在超临界条件下比非临界条件下进行得更快，反应温度对催化活性有很大影响。碱性配体对1－甲基咪唑的存在能有效地提高这些铝配合物的催化性能。同时，基于低温下的一些光谱数据，提出了可能的反应机理。     

Transesterification of Ethylene Carbonate with Dimethyl Terephthalate over Various Metal Acetate Catalysts

IntroductionDimethyl carbonate(DMC) is known to be a novelbuilding block in organic synthesis. As an environmen-tally benign compound and a unique intermediate,DMC has attracted much attention[1,2]. Among the va-rious methods for synthesizing DMC, the tra…     

A New Process for Synthesis of Dimethyl Carbonate from Ethylene Carbonate and Methanol without any Catalyst under Supercritical Conditions

Dimethyl carbonate was synthesized by transesterification reaction between ethylene carbonate and methanol under supercritical conditions without any catalyst. Experimental results showed that the residence time and the molar ratio of methanol to ethylene carbonate all can affect the conversion of ethylene carbonate. When the molar ratio of methanol to ethylene carbonate was 8:1, 81.2% conversion can be achieved at 9.0 MPa and 250℃ after 8 h.     

不同催化剂上碳酸乙烯酯与对苯二甲酸二甲酯的酯交换反应

 将碳酸乙烯酯与甲醇酯交换合成碳酸二甲酯的反应和乙二醇与对苯二甲酸二甲酯酯交换合成聚对苯二甲酸乙二醇酯(PET)的反应偶合,建立了同时合成碳酸二甲酯和PET的新方法. 探索了有机锡、钛酸酯、乙酸盐和金属氧化物等不同催化剂对合成碳酸二甲酯和PET的影响. 二丁基氧化锡的催化效果最佳,其碳酸二甲酯的收率达68.4%.     

Dielectric Spectroscopic and Molecular Simulation Evidence for Aggregation of Surfactant-stabilized Calcium Carbonate Nanocolloids in Organic Media

Dielectric spectroscopy carried out on overbased phenate micelle particles of nominal diameter 2 nm containing calcium carbonate cores in hydrophobic liquids indicates that the micelles are strongly aggregated. Mean cluster sizes in excess of 10³individual micelles are typically found in toluene. The level of association is a little higher in dodecane which is chemically closer to engine oil, the usual solvent for these systems. The mean aggregate size increases dramatically with concentration above an effective solids volume fraction of 0.1 on treating the micelles as spheres. Aggregate size also depends on the level of overbasing, with lower levels of overbasing giving more micelles in the cluster. Molecular dynamics simulations of individual micelle particles reveal them to have large dipole moments originating mainly from the amorphous carbonate cores. Dipoles of magnitude 20D are typical for a range of different surfactant types used in the model. The magnitude of the dipole depends somewhat on the chemical composition of the stabilizing surfactant shell. Monte Carlo simulations of two phenate nanocolloids taking into account all atom and charge pair interactions show these particles to have a strong short-range coulombic attraction of typically −25k_BTatT= 298 K in the favored “side-by-side” relative arrangement. This attraction could be responsible for the strong level of association inferred from the dielectric spectroscopy experiments.     

多种谱学方法研究环氧乙烷/四氢呋喃共聚醚的热氧降解

采用电子自旋共振（ESR）、傅里叶变换红外光谱（FT－IR）和多种核磁共振（NMR）技术研究了环氧乙烷／四氢呋喃共聚醚的热氧降解,表 征了近20种产物结构碎片,并对EO和THF两种链节的降解作了定量讨论。共聚醚的氧化降解发生在醚键氧碳上,遵循自由基氧化机理,最后形成大量的甲酸酯、碳酸酯等酯类以及甲基、亚甲二氧基和醇,此外还检测到过氧化氢和半缩甲醛结构。分析表明共聚醚中THF链节的降解程度明显大于EO链节,而且降解容易发生在两种链节交替连接处。抗氧剂2,6－二叔丁基－4－甲基酚（BHT）不仅降低了共聚醚的氧化降解程度,还改变了降解产物的结构分布,显著抑制了碳酸酯和亚甲二氧基结构的生成,相对增加了羟基和端甲基结构。     

Vibrational Spectroscopic Study on Ion Solvation and Association of Lithium Perchlorate in 4-Methoxymethyl-ethylene Carbonate

Solvation interaction and ion association in solutions of lithium perchlorate/4-methoxymethyl-ethylene carbonate （MEC） have been studied by using Infrared and Raman spectra as a function of concentration of lithium perchlorate. The splitting of ring deformation band and ring ether asymmetric stretching band, and the change of carbonyl stretching band suggest that there should be a strong interaction between Li^＋ and the solvent molecules, and the site of solvation should be the oxygen atom of carbonyl group. The apparent solvation number of Li^＋ was calculated by using band fitting technique. The solvation number was decreased from 3.3 to 1.1 with increasing the concentration of LiClO4/MEC solutions. On the other hand, the band fitting for the ClO4^- band revealed the presence of contact ion pair, and free ClO4^- anion in the concentrated solutions.     

基于反应力场分子模拟的乙烯燃烧自由基与氮气相互作用研究

采用反应力场分子动力学(ReaxFF-MD)方法, 模拟了富燃料条件下乙烯在空气中的燃烧以及燃烧产生的自由基与氮气的相互作用. 采用ReacNetGenerator程序提取反应网络, 结合自编后处理程序确定反应网络上的相关反应, 分析了乙烯燃烧的反应路径, 以及自由基与N₂的相关反应和NO的生成路径. 结果表明, 乙烯燃烧路径与已报道的通过乙烯燃烧反应机理模拟得到的燃烧路径一致, 说明用ReaxFF-MD方法模拟乙烯高温燃烧有效而可靠; 乙烯在富燃料条件下燃烧产生的CH, C₂H, C₂, C₂O自由基是瞬发型NO生成的重要反应物. 这些自由基与N₂的反应和NO的生成路径, 为构建乙烯和大分子碳氢燃料燃烧氮氧化物排放的反应机理提供了重要参考.     

氟分子与乙烯反应的直接动力学模拟

Direct dynamics within the framework of DFT was used to study the long-time puzzling mechanism of the reaction between F2 and ethylene. Three types of reactions are widely accepted : F atom elimination reaction, HF elimination reaction and the addition reaction. Several reaction mechanisms have been proposed, but only the radical mechanism can reasonably explain the initial reaction at low temperature. In this article, our calculations support the radical mechanism and the reaction mechanisms of the three reactions, and they are described in detail by trajectory simulation. The reactions in a cryogenic matrix with the reaction mechanism were also discussed.     

CO2和环氧乙烷直接制备碳酸乙烯酯的研究进展

本文综述了利用CO₂和环氧乙烷（EO）直接催化合成碳酸乙烯酯（EC）的研究进展,详细讨论了各种催化剂活化EO和CO₂,完成环加成反应的催化机理,并展望了该领域的研究前景。     

含稀土的钛系催化剂进行乙烯聚合动力学及ZnCl2调节分子量的研究

以SN-1催化剂进行乙烯常压聚合动力学研究表明,催化剂高效的主要原因是活性中心浓度明显增大、表观活化能△E较低。研究了ZnCl₂对乙烯聚合反应的影响。发现ZnCl₂能有效地降低聚乙烯的分子量,并能显著地提高催化效率,当ZnCl₂浓度过大时,则对聚合反应有抑制作用。     

Structural Dynamics of Chloromethanes through Computational Spectroscopy: Combining INS and DFT

In this work, the structural dynamics of the chloromethanes CCl₄, CHCl₃ and CH₂Cl₂ were evaluated through a computational spectroscopy approach by comparing experimental inelastic neutron scattering (INS) spectra with the corresponding simulated spectra obtained from periodic DFT calculations. The overall excellent agreement between experimental and calculated spectra allows a confident assignment of the vibrational features, including not only the molecular fundamental modes but also lattice and combination modes. In particular, an impressive overtone sequence for CHCl₃ is fully described by the simulated INS spectrum. In the CCl₄ spectrum, the splitting of the ν3 mode at ca. 765–790 cm⁻¹ is discussed on the basis of the Fermi resonance vs. crystal splitting controversy.     

Vibrational Spectroscopic and Mechanical Investigation of Carbon Nanotube-Reinforced Styrene-Butadiene Rubbers

This paper reports investigations carried out on elastomeric matrices based on a styrene-butadiene copolymer filled with multiwall carbon nanotubes. Stress-strain measurements of the composites demonstrate that carbon nanotubes bring significantly improvements in the mechanical properties with regard to the pure polymer. Raman spectroscopy, which is one of the most extensively employed methods for the characterization of carbon materials, has been applied for the analysis of the dependence of the Raman spectra on the nanotube content and on application of an uniaxial deformation. The results reveal a negligible stress transfer suggesting a weak interface between the tubes and the polymer chains.     

Supramolecular Interactions of Nonsteroidal Anti‐inflammatory Drug in Nanochannels of Molecular Containers: A Spectroscopic,Thermogravimetric and Microscopic Investigation

Supramolecular host–guest complexation between the nonsteroidal anti‐inflammatory drug indomethacin (IMC) and molecular containers were investigated. The weakly fluorescent drug molecule becomes highly fluorescent on complexation with different molecular containers, and time‐resolved fluorescence emission spectroscopy reveals that the lifetime components of IMC significantly increase in the presence of molecular containers, compared with the lifetimes in neat water. The respective solid host–guest complexes were synthesised and characterised by Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopic analysis. Microscopy techniques were used to analyse modifications of the surface morphology, owing to the formation of supramolecular complexes. The effect of the molecular container on the optical properties of IMC has also been investigated to determine the effect of nanochannels of different size and structure.     

Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly（ethylene terephthalate）： I. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

Dimethyl carbonate (DMC) is a new building block of organic synthesis, as an environmentally benign compound and unique intermediate, it has been attracted much attention. Among the various methods for synthesizing DMC, transesterification of ethylene car…     

Study on the Forming Mechanism and Preparation of Different Morphology of Barium Carbonate Crystals with Diethyl Carbonate as Raw Material

Different morphologies of BaCO3 crystals with dendritic structure,spinous sphere structure,and spike-,flower-and rod-like structures were prepared with(C2H5)2CO3 and BaCl2.2H2O as raw materials by homogeneous precipitation method.The crystals have been characterized by SEM,FT-IR and XRD,indicating that the different morphology of BaCO3 crystals belongs to the orthorhombic crystal system with uniform distribution and integral shapes.The effect of reaction conditions and the possible formation mechanism on the morphology of BaCO3 crystals have been discussed.     

Shock Tube Measurement of Ethylene Ignition Delay Time and Molecular Collision Theory Analysis

In this study, 75% and 96% argon diluent conditions were selected to determine the ignition delay time of stoichiometric mixture of C₂H₄/O₂/Ar within a range of pressures (1.3-3.0 atm) and temperatures (1092-1743 K). Results showed a logarithmic linear relationship of the ignition delay time with the reciprocal of temperatures. Under both two diluent conditions, ignition delay time decreased with increased temperature. By multiple linear regression analysis, the ignition delay correlation was deduced. According to this correlation, the calculated ignition delay time in 96% diluent was found to be nearly five times that in 75% diluent. To explain this discrepancy, the hard-sphere collision theory was adopted, and the collision numbers of ethylene to oxygen were calculated. The total collision numbers of ethylene to oxygen were 5.99×10³⁰ s^-1cm^-3 in 75% diluent and 1.53×10²⁹ s^-1cm^-3 in 96% diluent (about 40 times that in 75% diluent). According to the discrepancy between ignition delay time and collision numbers, viz. 5 times corresponds to 40 times, the steric factor can be estimated.     

Validation by Molecular Dynamics of the Major Components of Sugarcane Vinasse,On a Surface of Calcium Carbonate (Calcite)

There is ongoing interest in the alcohol industry to significantly reduce and/or add value to the liquid residue, vinasse, produced after the distillation and rectification of ethanol from sugar cane. Vinasse contains potassium, glycerol, and a protein component that can cause environmental issues if improperly disposed of. Currently, some industries have optimized their processes to reduce waste, and a significant proportion of vinasse is being considered for use as an additive in other industrial processes. In the manufacture of cement and asphalt, vinasse has been used in the mixtures at low concentrations, albeit with some physical and mechanical problems. This work is the first molecular approximation of the components of the sugar cane vinasse in an industrial context, and it provides atomic details of complex molecular events. In the current study, the major components of sugar cane vinasse, alone or complexed on the surface of calcium carbonate, were modeled and simulated using molecular dynamics. The results showed that the protein component, represented by the mannoprotein Mp1p, has a high affinity for forming hydrogen bonds with potassium and glycerol in the vinasse. Additionally, it provides atomic stability to the calcium carbonate surface, preserving the calcite crystalline structure in the same way potassium ions interact with the carbonate group through ion–dipole interactions to improve the cohesion of the modeled surface. On the contrary, when the glycerol molecule interacts with calcium carbonate using more than two hydrogen bonds, it triggers the breakdown of the crystalline structure of calcite expanding the ionic pair.