共沸剂对碳酸二甲酯-甲醇共沸物分离效率的影响

采用正庚烷、正己烷、环己烷、1,2-二氯乙烷、四氯化碳和苯等共沸剂，较系统地考察了共沸剂及回流比对碳酸二甲酯（DMC）-甲醇（CH3OH）共沸物共沸精馏分离效果的影响。结果表明，采用共沸精馏法可以高效分离DMC-CH3OH共沸物，通过调控回流比以及共沸剂可以有效改变分离后釜液中组分的组成。采用相同共沸剂下，当回流比为7∶1和8∶1时DMC-CH3OH共沸物的分离效果较好。相同回流比7∶1下，采用不同共沸剂共沸精馏DMC-CH3OH混合物得到DMC的质量分数和收率顺序为：1,2-二氯乙烷＞四氯化碳＞环己烷＞苯＞正己烷＞正庚烷。     

掺锑氧化锡纳米晶体的制备及性能研究

以SnCl4.5H2O和SbCl3乙醇溶液为原料,用离子交换除氯水解法制备得到无氯离子的前驱体掺锑氢氧化锡胶体沉淀。采用了乙酸异戊酯有机溶剂作脱水剂以消除掺锑氢氧化锡胶体干燥过程中硬团聚的形成,并和常用的正丁醇共沸溶剂进行了粉体性能的比较。用BET、XRD和TEM等方法对前驱体和掺锑氧化锡纳米粉体进行表征。结果表明,乙酸异戊酯溶剂比正丁醇溶剂更有效防止了粉体干燥过程中硬团聚的形成;将乙酸异戊酯干燥所得掺锑氢氧化锡干粉经热处理后得到了高比表面积的掺锑氧化锡纳米粉体,并对晶粒的生长过程进行了研究。     

Influence of Drying Processes on Agglomeration and Grain Diameters of Magnesium Oxide Nanoparticles

Magnesium hydroxide precipitate was prepared using magnesium chloride and urea as starting materials via a homogenous precipitation method. Before it was calcined to obtain magnesium oxide nanoparticles, the precipitate was pretreated and dried using different pretreatments and drying methods. The as-prepared magnesium oxide nanoparticles were characterized by transmission electron microscope and X-ray diffraction. The results show that when drying methods (except for supercritical CO2 extraction drying) are the same, grain diameters and agglomeration of magnesium oxide nanoparticles exhibit a similar trend and depend on pretreatment. The agglomeration of magnesium oxide nanoparticles is relevant with drying methods when pretreatments are same. The agglomeration of magnesium hydroxide particles is mostly induced by capillary pressure or surface tension.     

木糖醇缩醛类凝胶因子的合成及其凝胶性能的研究

以取代的苯甲醛和木糖醇为原料,环己烷为溶剂和夹带剂,甲醇为促进剂,十二烷基苯磺酸为催化剂,用共沸脱水法合成了5个木糖醇缩醛衍生物:1,3∶2,4-二(对甲基苄叉)-D-木糖醇(Ⅰ),1,3∶2,4-二(间甲基苄叉)-D-木糖醇(Ⅱ),1,3∶2,4-二(邻甲基苄叉)-D-木糖醇(Ⅲ),1,3∶2,4-二(3,4-二甲基苄叉)-D-木糖醇(Ⅳ),1,3∶2,4-二苄叉-D-木糖醇(Ⅴ)。将木糖醇缩醛衍生物用作低相对分子质量(以下简称分子量)有机凝胶因子,比较了其凝胶性能,取代基以空间位阻的形式影响凝胶因子分子的自组装,并能增强凝胶因子分子之间的相互作用。溶剂通过范德华力参与了凝胶三维网络的构建,提高网络的强度。红外光谱测试表明,凝胶形成过程中生成的氢键是该类凝胶因子自组装的驱动力。     

Effect of solvent exchange on the stability of sterically functionalized magnetite nanoparticles in poly(methyl methacrylate) solutions and resulting spray dried composites

In this study highly filled nanoparticle–polymer composites consisting of the polymer poly(methyl methacrylate) and magnetite nanoparticles are synthesized via the solution and spray drying method. The synthesis process is carried out for two different solvents, dichloromethane and ethyl acetate, and the resulting suspensions and composites are compared to each other. The preparation of the composites consists of the following steps: First the magnetite nanoparticles are precipitated in an aqueous phase. In the next step the nanoparticles are coated with ricinoleic acid for stabilization and are transferred to the organic solvent dichloromethane. In a rotating evaporator the solvent dichloromethane is exchanged with ethyl acetate. Finally, the nanoparticles in the respective solvent and dissolved polymer are mixed and spray dried.     

一步沉淀法制备表面疏水性纳米氢氧化镁

以油酸为改性剂,采用化学沉淀法一步制备了表面疏水性的氢氧化镁纳米粒子,研究了合成条件对氢氧化镁团聚和形态的影响。XRD证明所制备的氢氧化镁纯度高,平均晶粒尺寸为16nm;FT-IR表明油酸分子已键合在纳米氢氧化镁表面;TEM显示,所制备的纳米氢氧化镁表面形态呈针状或片状,在甲苯中分散性好。计算得到制备的纳米氢氧化镁活化指数可达98.9%,粒子表面呈疏水性。     

Synthesis and Characterization of Coralline Magnesium Oxide Nanoparticles

Magnesium oxide (MgO) nanoparticles were prepared using sol–gel process. The nanoparticles were then dried using a supercritical drying process. The particles were characterized for surface morphology, crystal structure, and surface functionality. The nanoparticles show a coralline structure with an average particle size of 200–300 nm with a surface area of 257 m²/g. The X-ray diffraction spectra of these materials are also obtained. The MgO particles, when contacted with a model explosive component 2, 4 dinitrotoluene in water at 50°C, showed a concentration reduction of 96%.     

聚酯丙烯酸UV树脂的合成

采用端羟基聚酯与丙烯酸在适当的条件下合成出性能优异的聚酯丙烯酸UV树脂。聚酯(双端羟基)与丙烯酸反应过程中产生水,决定了合成工艺不同于其他UV树脂的合成。分别讨论了聚酯树脂,聚酯丙烯酸UV树脂合成过程中温度、共沸溶剂、催化剂等对树脂性能的影响。得出如下结论:聚酯的合成在180℃进行,二甲苯为共沸溶剂,H3PO4为催化剂;聚酯丙烯酸UV树脂的合成在110~120℃进行,甲苯为共沸溶剂,催化剂为对甲苯磺酸。并讨论了阻聚剂在UV树脂合成过程中的作用。     

丙酮-四氢呋喃-水混合物的清洁分离工艺的概念设计

引言 四氢呋喃（THF）既是一种性能优良的贵重有机溶剂,又是一种重要的有机合成中间体,因此在制药、涂料、皮革等领域应用广泛．当四氢呋喃用作溶剂时,由于其不被消耗,往往需要进行回收．但四氢呋喃易与水、丙酮等其他极性溶剂形成共沸物,而生产中又常需要四氢呋喃的纯度足够高,进而增加了分离提纯难度．     

三苯基膦稳定金纳米粒子的合成及其特性研究

在水/乙醇混和体系中制备了三苯基膦稳定的金纳米粒子(GNPs)溶液。GNPs的粒径为5 nm,在548 nm有典型的表面等离子吸收。在不使用其它相转移分子的情况下,GNPs可以容易地转移到有机溶剂如二氯甲烷中,并得到可再分散于有机溶剂或水中的固体粉末,为制备可应用于不同的物理化学环境中的表面功能化GNPs提供了优异的初始化合物。     

The effect of donor-acceptor interactions on the mechanical properties of wood

This paper explores the empirical correlations between the mechanical properties of solvent-treated wood and solvent parameters. Wood beams (10 inch x 0.7 inch x 0.4 inch) of lauan, birch, and Douglas fir were soaked in five solvents (benzene, dioxane, methanol, dimethyl sulfoxide, and distilled water) for 4 months at room temperature (23°C) and then mechanically tested in bending. The acoustic emission (AE) energy (related to failure energy), the modulus of rupture (MOR), and the modulus of elasticity (MOE) of the specimens were determined. It was found that all of these properties of the specimens decreased with the solvent strength parameter which was related to acceptor number (AN), donor number (DN) and molecular volume (MV ). The linear correlation of the AE energy of the specimens with the solvent parameter (AN + DN)^1/2 was verified. Alternative relationships between the AE energy, MOR or NIOE of the specimens and the modified solvent strength parameters, 2.5 DN + AN or DN/MV^1/3, were explored. The microstructures of fracture surfaces of lauan specimens were examined by scanning electron microscopy (SEM) and showed dramatic changes when the solvent strength increased, such as microfibril pull-out and a decrease in roughness of the fracture surfaces of cell walls. All these observations reflected the changes in mechanical properties and the mean AE energy qualities of the specimens.     

萃取精馏分离乙酸甲酯-甲醇溶剂

用汽液平衡装置对萃取精馏分离乙酸甲酯-甲醇极性共沸体系的溶剂选择进行了实验研究.结果表明:被分离物系的分离效果随溶剂比(质量比)的增大而增大;二元混合溶剂(二甲基亚砜DMF+N,N-二甲基甲酰胺DMSO)和三元混合溶剂(N-甲基吡咯烷酮NMP+DMF+DMSO)的分离效果优于单一溶剂(DMF),且DMF和DMSO的摩尔...     

Aerosol Synthesis of Lipid Nanoparticles: Relating Crystallinity to Simulated Evaporation Rates

The degree of crystallinity of nanometer size lipid matrices governs drug loading and release rates. Recently, droplet-phase aerosol synthesis was used to prepare lipid nanoparticles of stearic acid and achieve control over their crystallinity using precursor solvents with differing vapor pressures. The present work aims at examining relationships between solvent evaporation rate and extent of evaporative cooling, during drop evaporation, on the crystallinity of the resulting lipid nanoparticles. A stationary drop model was developed to study evaporation of submicron-sized solution drops, of stearic acid in organic solvents, by including mechanisms of solvent vapor pressure depression by the solute, heat and mass transfer between the drop ensemble and suspending gas, Kelvin (curvature) effect, noncontinuum vapor transfer effects, and changes in activity coefficients of solute and solvent with changing concentrations. It was found that increasing estimated evaporation rates correlated with decreasing measured crystallinity. Higher evaporation rates also led to greater evaporative cooling and lower drop temperatures. The rate of change of supersaturation in solution drops under fast evaporation was shown to be an order of magnitude higher than that for slow evaporation. The modeled evaporation rate and drop temperature depend primarily on vapor pressure and enthalpy of vaporization of the precursor solvent. This suggests that selection of precursor solvents, with desired physical properties, can be used to control crystallinity, and related drug release behavior of lipid nanoparticles made through aerosol synthesis routes.

Copyright 2012 American Association for Aerosol Research     

萃取精馏过程中萃取剂选择及萃取条件研究

采用改进的UNIFAC模型,借助于MATLAB计算软件,编制了相应的计算程序,用于萃取精馏过程中萃取剂的选择、萃取性能的考察以及萃取条件的影响研究。通过对甲醇-乙酸甲酯共沸体系在不同萃取剂和不同萃取条件下相对挥发度的计算,选择出适宜的萃取剂,并讨论了温度和溶剂比对相对挥发度的影响。     

Reactions of unsaturated fatty alcohols. VII. Polymerization of vinyl ethers catalyzed by stannic and ferric chlorides

Summary Variables affecting the use of stannic chloride as a catalyst for initiating polymerization of conjugated and nonconjugated soybean vinyl ether were studied. Molecular weight of the polymers increased with an increase in catalyst and a decrease in initiation temperature, and it decreased when the amount of moisture in the solvent, the amount of free fatty alcohol in the monomer, or the ratio of solvent to monomer was increased. Aromatic and aliphatic hydrocarbon solvents were superior to halogenated solvents for conducting polymerizations. Similar results were obtained with nonconjugated monomers except that viscosities of the polymers were considerably lower than those of polymers of the same molecular weight obtained from conjugated monomer. To obtain polymers suitable for film-forming studies (4,000–6,000 molecular weight) polymerization is initiated preferably at 25°C. with 3 ml. of anhydrous toluene used per gram of monomer and 4.8 mmoles of stannic chloride per mole of monomer. Monomer purity should be at least 98%. Ferric chloride hexahydrate initiated polymerization at 25°, but polymerization was incomplete, and the polymers had relatively low molecular weights. Presented in part at the fall meeting, American Oil Chemists' Society, Chicago, Ill., Oct. 20–22, 1958. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

SnO2纳米粒子的溶剂热制备及光致发光性质

以SnCl4·5H2O为原料,乙二胺为溶剂,用溶剂热法在180℃合成了SnO2纳米粒子,用XRD和TEM对其结构和形貌进行了表征,对SnO2纳米粒子的红外谱图、漫反射谱图以及光致发光性能进行了分析,探讨了乙二胺辅助合成SnO2纳米粒子的化学原理和生长机制。结果表明,用乙二胺辅助成长法合成的SnO2纳米粒子的粒径在40nm左右,粒径分布均匀,分散性较好。SnO2纳米粒子光致发光在340、432和672nm处有3个强峰,在472和540nm处有2个弱峰,其中340nm处的峰为紫外近带边激子发射峰,432、472和540nm处的峰是由氧缺陷引起的,672nm处的峰归因于表面态的氧缺陷引起的能带中深能级跃迁。     

Granulometric synthesis and characterisation of dispersed nanosilica powder and its application in cementitious system

Abstract

Dispersed, spherical particles of nanosilica with controllable size have been synthesised using a metal alkoxide, i.e. tetraethoxysilane, as starting material, ammonia as base catalyst and non-ionic surfactant as template by sol–gel method. Size of particles and dispersivity were controlled by varying the surfactant chain length and temperature conditions of the reaction mixture. Silica nanoparticles were synthesised using a series of non-ionic surfactants, namely Polyoxyethylene (20) sorbitan monolaurate (Tween 20) and Polyoxyethylene (80) sorbitan monooleate (Tween 80), at different reaction temperatures of 25, 50, 70 and 90°C. The particle size of silica nanoparticles gradually decreased with increasing carbon chain length of the surfactant and at higher temperature particle size became larger. Furthermore, these silica nanoparticles are incorporated into the cementitious system to improve the mechanical properties and reduce calcium leaching in the hydration process. Addition of silica nanoparticles into cement paste improves the microstructure of the paste, and calcium leaching is significantly reduced as silica nanoparticles react with calcium hydroxide, thereby forming a denser calcium–silicate–hydrate gel structure. Synthesised silica nanoparticles and microstructure of cement paste incorporated with silica nanoparticles were analysed using scanning electron microscopy, powder X-ray diffraction, infrared spectroscopy (IR), ²⁹Si MAS NMR and thermogravimetry analysis for morphological and mineralogical attributes.     

Predicting hydrogen-bond strengths from acid-base molecular properties. The pK(a) slide rule: toward the solution of a long-lasting problem

Unlike normal chemical bonds, hydrogen bonds (H-bonds) characteristically feature binding energies and contact distances that do not simply depend on the donor (D) and acceptor (:A) nature. Instead, their chemical context can lead to large variations even for a same donor-acceptor couple. As a striking example, the weak HO-H...OH(2) bond in neutral water changes, in acidic or basic medium, to the 6-fold stronger and 15% shorter [H(2)O...H...OH(2)](+) or [HO...H...OH](-) bonds. This surprising behavior, sometimes called the H-bond puzzle, practically prevents prediction of H-bond strengths from the properties of the interacting molecules. Explaining this puzzle has been the main research interest of our laboratory in the last 20 years. Our first contribution was the proposal of RAHB (resonance-assisted H-bond), a new type of strong H-bond where donor and acceptor are linked by a short pi-conjugated fragment. The RAHB discovery prompted new studies on strong H-bonds, finally leading to a general H-bond classification in six classes, called the six chemical leitmotifs, four of which include all known types of strong bonds. These studies attested to the covalent nature of the strong H-bond showing, by a formal valence-bond treatment, that weak H-bonds are basically electrostatic while stronger ones are mixtures of electrostatic and covalent contributions. The covalent component gradually increases as the difference of donor-acceptor proton affinities, DeltaPA, or acidic constants, DeltapK(a), approaches zero. At this limit, the strong and symmetrical D...H...A bonds formed can be viewed as true three-center-four-electron covalent bonds. These results emphasize the role PA/pK(a) equalization plays in strengthening the H-bond, a hypothesis often invoked in the past but never fully verified. In this Account, this hypothesis is reconsidered by using a new instrument, the pK(a) slide rule, a bar chart that reports in separate scales the pK(a)'s of the D-H proton donors and :A proton acceptors most frequently involved in D-H...:A bond formation. Allowing the two scales to shift so to bring selected donor and acceptor molecules into coincidence, the ruler permits graphical evaluation of DeltapK(a) and then empirical appreciation of the D-H...:A bond strength according to the pK(a) equalization principle. Reliability of pK(a) slide rule predictions has been verified by extensive comparison with two classical sources of H-bond strengths: (i) the gas-phase dissociation enthalpies of charged [X...H...X](-) and [X...H...X](+) bonds derived from the thermodynamic NIST Database and (ii) the geometries of more than 9500 H-bonds retrieved from the Cambridge Structural Database. The results attest that the pK(a) slide rule provides a reliable solution for the long-standing problem of H-bond-strength prediction and represents an efficient and practical tool for making such predictions directly accessible to all scientists.     

Synthesis of new functionalized polymers and their use as stabilizers of Pd,Pt, and Rh nanoparticles. Preliminary catalytic studies

Polymers I ‐ X with functionalized main chain were synthesized from commercial polymers containing reactive groups, anhydride (for Gantrez), or carboxylate (for polyacrylates) moieties, to be used as stabilizers of metallic nanoparticles. ¹H HRMAS, ¹³C MAS NMR, IR, and GPC techniques were applied to characterize the new polymers. Metal transition nanoparticles stabilized with these polymers were prepared in organic solvents (Pd and Pt) and also in water/ethanol medium (Rh), under hydrogen atmosphere. TEM analysis revealed the formation of small nanoparticles, in the range ～ 3–20 nm, depending on the solvent, metal precursor, metal concentration, and polymer nature. Preliminary catalytic applications, C? C couplings using palladium and hydrogenations using platinum and rhodium systems in organic and also aqueous medium, were tested. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Impact of solvent on Co/SiO2 activity and selectivity for the synthesis of n-butylamine from butyronitrile hydrogenation

The impact of solvent on Co(9.8%)/SiO₂ activity and selectivity for the synthesis of n-butylamine from butyronitrile hydrogenation was investigated using methanol, benzene, toluene and cyclohexane as solvents. In non-polar solvents, the yield of n-butylamine increased from 60% to 79% following the order cyclohexane < toluene < benzene. Nevertheless, the highest n-butylamine yield (91%) was obtained in methanol, a protic solvent. The solvent effect on the catalyst performance was interpreted by considering: i) the solvent–catalyst interaction strength and ii) the solvent polarity and its ability for H-bond formation with n-butylamine.