Separation of Liquid Mixtures by Pervaporation

Separation of various mixtures, especially liquid mixtures, is a very necessary unit operation in industry. A large number of such techniques are available, such as distillation, adsorption, liquid-liquid extraction, and fractional crystalization [l]. The development of this type of technology became necessary to effect separation of azeotropic liquid mixtures. For liquid mixtures having components with similar boiling ranges, however, such conventional separation techniques are energy intensive and add considerably to the cost of the final product. With the advent of the necessity of reducing the energy requirements of Unit options, membrane separation has been recognized as an alternative to the conventional methods.     

液体混合物的粘度方程

本文基于Eyring纯液体粘度理论,并引进局部克分子组成概念,提出一个液体混合物粘度方程 其中 A_(ij)=exp〔-(g_(ij)-g_(ii))/RT〕 该方程被应用于近30个二元体系和5个三元体系的计算,结果表明,它对于二元实测粘度数据的关联和多元粘度～组成关系的预测都是相当有效的。 文中对方程的建立、参数的物理意义和方程的适用性进行了探讨。     

Dissolution Kinetics of Crystalline and Amorphous Silica in Hydrofluoric-Hydrochloric Acid Mixtures

The dissolution kinetics of crystalline and amorphous silica were studied as a function of time, temperature, concentration of HF, concentration of HC1, and crystallographic orientation. The results indicate that dissolution is a surface reaction-controlled process. The dissolution rate depends strongly on HF concentration and weakly on HC1 concentration. The dissolution rates depend on crystallographic direction in α-quartz and are slower than for fused silica. The rate-controlling step is thought to be a ligand exchange process at the surface.     

Structural and Mechanical Properties of Nanoporous Silica

Nanoporous silica systems with porosity between 30% and 70% were developed using two Molecular Dynamics (MD) simulation protocols to obtain structures with dissimilar pore morphologies. Short‐ and medium‐range structural characteristics including bond angle distributions and pair distribution functions were analyzed and found to be consistent with experimental results. Surface area to volume ratio and pore microstructures were characterized and compared with experimental observations. Mechanical properties including elastic, shear, and bulk moduli of these nanoporous silica systems were calculated and their change as a function of porosity was compared with experimental data and theoretical models. It was found that the elastic modulus of porous silica with 50% porosity is 5–14 GPa which is consistent with experimental results. The elastic moduli–porosity relationship was fitted by exponential and power functions, and analysis of coefficients was performed to obtain microstructure characteristics of the simulated nanoporous silica structures. This works confirms that two distinct nanoporous silica microstructures are generated with MD simulations which result in variations in mechanical properties and highlight the importance of selecting a nanoporous silica simulation method which approximates experimental systems.     

几种二元混合制冷剂的汽液平衡研究

对臭氧安全二元混合物系ＨＦＣ１２５／ＨＦＣ１４３ａ和ＨＦＣ１５２ａ／ＨＦＣ１４３ａ进行了泡点、露点实验研究和相平衡关联计算,结果表明前者为近共沸混合物,后者为非共沸混合物。给出了１０种低环害二元物系对应于ＲＫＳ、ＰＲ、ＰＴ状态方程及二次型混合规则的交互作用系数。     

Effect of Silica Packing on Ozone Synthesis from Oxygen-Nitrogen Mixtures

The effect of silica packing in an ozone generator fed with oxygen-nitrogen mixtures has been studied. The measurements were carried out in an ozone generator with a double-sided cooled discharge gap, in which silica packing has been placed. In the presence of the packing considerably higher ozone concentrations were achieved than in the ozone generator without packing. An especially clear effect of silica packing was observed in air-fed conditions. It has been found that the increase in the concentration of the obtained ozone coincides with the increase of N₂O in the post-reaction gas.     

Interaction of Silica Particles Through a Liquid

Measurements of the destruction time of the sediment column structure were carried out for different fractions of silica particles in NaCl and CaCl₂ solutions whose concentrations were varied from 0.25 M to 2.0 M. On the basis of this study, linear relationships between the reciprocal of the destruction time of the silica sediment column structure and average diameter of the silica fraction, the density and the work of cohesion of the solutions were found. From these relationships the critical values of the particle diameter, the cohesion work and density of the solutions were determined for the destruction time equal to infinity (1/t = 0). The detachment force of one particle from another, which resulted from gravitational interaction, was calculated using the above critical parameters. For the system whose components have critical values the detachment force is found to be equal to the attachment force resulting from the interfacial interaction. Next, on the basis of our earlier study and Derjaguin's approximation, the radius of the contact plane and the attachment force between two silica particles were calculated. The detachment force decreased with increasing salt concentration, but the attachment force was nearly constant. It was found that, for a given salt concentration, the relationship between the reciprocal of the destruction time and the difference between the detachment and attachment forces was also linear. It appeared that for the silica column structure having critical parameters the values of the difference between the detachment and attachment forces were negative. This means that in the calculation of the attachment force between silica particles in the studied solutions an additional interaction should be taken into account.     

二元溶液表面张力的理论推算

<正>液体表面张力是化工传递过程中的重要物理量,因此对表面张力理论计算的研究一直十分活跃.时至今日,前人已建立了许多较为出色的纯液体及液体混合物表面张力的关联计算模型,但是工业过程常需要一些能进行预测计算的模型.有关液体混合物表面张力预测计算模型的研究,前人也已做了不少工作:Sprow和Prausnitz,基于Eckert和Prausnitz的研究成果,用溶解度参数法计算表面相活度系数,结合表面张力基本方程,建立了二元溶液表面张力的理论推算式,但该推算式只适用于简单分子溶液; Go ldsact等人从表面张力基本方程出发,假定主体相、表面相均为理想溶液,得到理想溶液表面张力的理论推算式;戎宗明等直接从Gibbs-Duhem方程得到的二元溶液表面张力的推算模型,在对一般     

Liquid Chromatographic Fractionations of Mixtures of Polystyrene Oligomers

Abstract

Oligomer mixtures of 800, 2200, and 4000 molecular weight polystyrene have been fractionated using silica and bonded phase columns under similar conditions of solvent gradient and flow rate. Using a hexane tetrahydrofuran gradient, the silica and nitro phases were best in that they separated 41 and 43 oligomers, respectively. At the other extreme, a phenyl bonded phase column gave virtually no resolution using a water/THF gradient, and a cyano bonded phase column, using the earlier hexane/tetrahydrofuran system, resolved only 10 oligomers. Amino and octadecyl bonded phase columns gave results intermediate between these two extremes. The strength of the solvent used to dissolve the sample was found to be of critical importance. Use of too good a sample solvent seriously degraded the attainable resolution. When number-average and weight-average molecular weights for an 800 molecular weight polystyrene sample were calculated from the oligomer distribution, the silica column gave values which were most consistent with those reported from other methods.     

玄武岩质陶瓷釉料中硼砂─—钠长石复合添加剂的影响

在组成玄武岩 80％、高岭土 19％、膨润土 1％ (以上均为 mass％ )的釉料中,使用硼砂—钠长石部分代替玄武岩以改善釉料的耐腐蚀性、抗裂性、显微硬度等性质。替代率分别为 10％、 20％和 30％ (mass％ ),并且它们具有不同的 B2O3/钠长石 (mass％ )比分别为 1/2、 1/1和 2/1,制备上述组成的釉料,以浸釉法施在干坯上,在 1100℃～ 1200℃间烧成,分别测定了釉的耐腐蚀性、抗裂性、显微硬度、热膨胀系数和熔体的表面张力,结果表明：该种复合添加剂能显著改善釉料的上述性能,并降低烧成温度。     

Chemical Kinetics of Detonation in Some Liquid Mixtures

The main objective of this work is to study the chemical kinetics of detonation reactions in some nitroester mixtures and solutions of nitrocompounds in concentrated nitric acid. The main source of information on chemical kinetics in the detonation wave was the experimental dependence of failure diameter on composition of mixtures. Calculations were carried out in terms of classic theory of Dremin using the SGKR computer code. Effective values for the activation energies and pre‐exponential factors for detonation reactions in the mixtures under investigation have been defined.     

有机物混合液导热系数的估算

通过对液体导热系数与密度关系的分析研究,提出了估算有机物混合液导热系数的计算模型;利用该模型计算了55个体系377个数据点的二元有机物混合液导热系数,计算值与实验值的总平均相对偏差为1.48%,计算值与实验数据吻合很好,计算准确性优于文献方法;本文方法简单方便,只需要混合液各组分的导热系数数据,就可以直接预测各种温度和组成的有机物混合液的导热系数。     

丁醇异构物与环己烷的超额焓

用以前所提出的液体通用混合模型［７］，导得了一个醇－烃液体混合物的超额焓与组成间的关系式，并由三个丁醇异构物与环己烷系统进行了检验。为了确定组分的特性常数，还实验测定了仲丁醇、异丁醇和叔丁醇在３０～８０℃温度范围的热压力系数。检验结果表明，这个关系式能满意地描述这些液体混合物的超额焓随组成的变化规律。     

二元液体混合物扩散系数的理论计算

许多化工过程涉及扩散控制的质量传递,扩散系数的获取对过程工程的精确量化具有重要意义.今提出了基于局部组成的扩散系数模型,以估算Maxwell-Stefan扩散系数随浓度的变化.仅通过无限稀释下的扩散系数,以及溶液的Wilson或NRTL参数,能够预测二元混合物的扩散系数.与文献发表的实验数据比较,对15种二元组分溶液的计算结果平均误差是6.35%.结果显示,这种模型优于目前常用的Darken模型.     

A Comparative Study on Curing Characteristics,Mechanical Properties,Swelling Behavior,Thermal Stability,and Morphology of Feldspar and Silica in SMR L Vulcanizates

Abstract

Comparison studies on effects of feldspar and silica (Vulcasil C) as a filler in (SMR L grade natural rubber) vulcanizates on curing characteristics, mechanical properties, swelling behavior, thermal analysis, and morphology were examined. The incorporation of both fillers increases the scorch time, t ₂, and cure time, t ₉₀, of SMR L vulcanizates. At a similar filler loading, feldspar exhibited longer t ₂ and t ₉₀ but lower values of maximum torque, M_HR, and torque difference, M_HR–M_L than did silica-filled SMR L vulcanizates. For mechanical properties, both fillers were found to be effective in enhancing the tensile strength (up to 10 phr), tensile modulus, and hardness of the vulcanizates. However, feldspar-filled SMR L vulcanizates showed lower values of mechanical properties than did silica-filled SMR L vulcanizates. Swelling measurement indicates that swelling percentages of both fillers-filled SMR L vulcanizates decrease with increasing filler loading whereas silica shows a lower swelling percentage than feldspar-filled SMR L vulcanizates. Scanning electron microscopy (SEM) on fracture surface of tensile samples showed poor filler–matrix adhesion for both fillers with increasing filler loading in the vulcanizates. However, feldspar-filled SMR L vulcanizates showed poorer filler–matrix adhesion than did silica-filled SMR L vulcanizates. Thermogravimetric analysis (TGA) results indicate that the feldspar-filled SMR L vulcanizates have higher thermal stability than do silica-filled SMR L vulcanizates.     

Separation of Liquid Mixtures and the Minimum Steam Rectification Stream

Theoretical Foundations of Chemical Engineering - In this paper, we compare various estimates of the abilities of liquid mixtures to be separated by distillation. The minimum specific heat...     

Thermal Effects in Evaporation from Binary Liquid Mixtures

Thermal effects are considered assuming a volatile component evaporates from a binary liquid mixture in a very long tube. The work is an extension of the work of Chebbi and Selim (2006 Chebbi, R., and Selim, M. S. (2006). The Stefan problem of evaporation of a volatile component from a binary liquid mixture, Heat Mass Transfer, 42(3), 238–247.[Crossref], [Web of Science ®] , [Google Scholar]) (isothermal case) to include evaporative cooling. A similarity solution is provided for the gas–liquid interface temperature and the temperature profiles in the liquid and gas phases. The analysis accounts for the motion of the gas–liquid interface and shows evaporative cooling as expected. The magnitude of evaporative cooling is found significant when volatility of the volatile component is sufficiently high. The validity of the approximations used in the solution is addressed.     

由PR状态方程计算液体混合物表面张力

在界面化学位的基础上，定义了组分的界面逸度系数，推导出一个新的液体混合物表面张力的表达式，同时用Ｐｅｎｇ－Ｒｏｂｉｎｓｏｎ状态方程计算液体混合物体相和表面相组分的逸度系数，从而实现了由状态方程计算液体混合物表面张力。文中用这一新模型计算了５６个二元体系的表面张力，平均相对偏差为３．３８％，说明该方法是可行的。     

液体烃及其混合物粘度预测方法的研究进展

综述了液体烃及其混合物粘度预测方法的研究进展。内容主要包括各种预测方法的理论基础、预测的具体方程形式,以及预测的平均误差。本文所选择的方法都是一些应用比较广泛比较有发展前景的方法。