Correlation of viscosity of binary liquid mixtures

A new two-parameter model presented in the previous work for correlating the viscosity of pure liquids is extended to correlate the viscosity of binary liquid mixtures. The correlation relates this non-equilibrium property to some equilibrium properties, the volume, the internal energy of vaporization and their excess properties. The viscosities of 47 binary liquid mixtures, including different kinds, which having no maximum or minimum viscosity, which having one maximum or one minimum viscosity, and which having both of one maximum and one minimum viscosities in the whole composition range, are correlated using the model and compared with data reported in the literature with the overall average absolute deviation of 1.05%. Further comparison with a good correlation, a free-volume type correlation, is also discussed. The results show that the new method is satisfactory.     

Generalized correlation for predicting the kinematic viscosity of liquid petroleum fractions

A two-parameter viscosity model proposed previously for pure liquids is extended to correlate the kinematic viscosity–temperature behavior for liquid petroleum fractions. The coefficients in the viscosity equation are related to the characterization properties of the petroleum fractions and a generalized kinematic viscosity–temperature correlation is then developed, which needs only specific gravity at 15.6°C and 50% boiling point as input parameters. The present method, when tested by predicting the experimental kinematic viscosities of 47 fractions from 15 world crude oils with total 250 data points, yielded reasonable results with an overall average absolute deviation of 4.2%.     

汽液共存相的粘度及导热系数间的关系

粘度和导热系数是石油、化工等工业过程设计中必需的两种主要传递性质，对它们的实验测定和理论预测或关联研究一直受到人们的广泛关注．对传递性质的研究有以下特点：在理论上，对气体，尤其是稀薄气体有较成功的动力学理论，但对稠密流体，尤其是液体，尚无严格的理论方法，实用中多为经验或半经验的模型；在实验测定方面，对液体的测定相对容易，已积累了大量数据，尤其是液体的粘度和导热系数．另外，在一些工业生产过程中，往往处理呈平衡（饱和）的汽、液两相。质，需要知道各种操作条件下两相工质的传递性质，因此，研究汽（气）、液…     

Transport properties of CO2-expanded acetonitrile from molecular dynamics simulations

Carbon-dioxide-expanded liquids, which are mixtures of organic liquids and compressed CO2, are novel media used in chemical processing. The authors present a molecular simulation study of the transport properties of liquid mixtures formed by acetonitrile and carbon dioxide, in which the CO2 mole fraction is adjusted by changing the pressure, at a constant temperature of 298 K. They report values of translational diffusion coefficients, rotational correlation times, and shear viscosities of the liquids as function of CO2 mole fraction. The simulation results are in good agreement with the available experimental data for the pure components and provide interesting insights into the largely unknown properties of the mixtures, which are being recognized as important novel materials in chemical operations. We find that the calculated quantities exhibit smooth variation with composition that may be represented by simple model equations. The translational and rotational diffusion rates increase with CO2 mole fraction for both the acetonitrile and carbon dioxide components. The shear viscosity decreases with increasing amount of CO2, varying smoothly between the values of pure acetonitrile and pure carbon dioxide. Our results show that adjusting the amount of CO2 in the mixture allows the variation of transport rates by a factor of 3-4 and liquid viscosity by a factor of 8. Thus, the physical properties of the mixture may be tailored to the desired range by changes in the operating conditions of temperature and pressure.     

A new three-parameter viscosity-temperature equation for saturated liquids from the triple point to the critical point

A new simple viscosity-temperature equation with only three adjustable parameters is proposed that is valid over the entire saturated liquid curve for a chemically diverse set of compounds. This equation can incorporate the correct near-critical behavior and satisfies the need for a reliable equation for fitting and predicting the viscosity of saturated liquids. It reproduces data within the experimental uncertainty over the entire saturated liquid region. Compared with the previous viscosity-temperature equations, the new equation not only more accurately correlates experimental data but also more effectively extrapolates values from the usual range in which data are available both to the critical point and to the triple point.     

Viscosity of n-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids saturated with compressed CO2

The viscosity of imidazolium-based ionic liquids (ILs) saturated with gaseous, liquid and supercritical carbon dioxide (CO₂) was measured by a high-pressure viscometer at three different temperatures (25, 50, and 70 °C). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1-n-hexyl-3-methylimidazolium ([HMIm]), and 1-n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)amide ([Tf₂N]), saturated with CO₂ was measured up to a maximum of 287 bar. As CO₂ pressure is increased the viscosity of the IL mixture dramatically decreases. While, the ambient pressure viscosity of 1-alkyl-3-methyl-imidazolium [Tf₂N] ILs increases significantly with increasing chain length, the viscosity of all the CO₂-saturated ILs becomes very similar at high CO₂ pressures. From previous vapor–liquid equilibrium data, the viscosity with concentration was determined and found to be the primary factor to describe the fractional viscosity reduction. Several predictive and correlative methods were investigated for the mixture viscosity given pure component properties and include arithmetic mixing rules, the Irving (Predictive Arrhenius) model, Grunberg equation, etc. The modified Grunberg model with one adjustable parameter provided an adequate fit to the data.     

Thermophysical properties of pure and water-saturated tetradecyltrihexylphosphonium-based ionic liquids

In this work, the solubility of water in several tetradecyltrihexylphosphonium-based ionic liquids at 298.15 K, and densities and viscosities of both pure and water-saturated ionic liquids in a broad temperature range were measured. The selected ionic liquids comprise the common tetradecyltrihexylphosphonium cation combined with the following anions: bromide, chloride, bis(trifluoromethylsulfonyl)imide, decanoate, methanesulfonate, dicyanamide and bis(2,4,4-trimethylpentyl)phosphinate. The isobaric thermal expansion coefficients for pure and water-saturated ionic liquids were determined based on the density dependence with temperature. Taking into account that the excess molar volumes of the current hydrophobic water-saturated ionic liquids are negligible, the solubility of water was additionally estimated from the gathered density data and compared with the experimental solubilities obtained. Moreover, the experimental densities were compared with those predicted by the Gardas and Coutinho model while viscosity data were correlated using the Vogel–Tammann–Fulcher method.     

A noncontinuum model of van der Waals interactions for describing the physicochemical properties of pure molecular liquids

A noncontinuum model based on the use of such molecular characteristics as molecular refraction, dipole moment, and molar volume is suggested for quantitatively describing the physicochemical properties (surface tension, enthalpy of vaporization, boiling temperature, viscosity, etc.) of pure molecular liquids. The ratio between the coefficients of correlation equations relating electrostatic and dispersion contributions to all the properties analyzed was found to be invariant.     

Eutectic-based ionic liquids with metal-containing anions and cations

Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids. FAB-MS analysis shows that the liquids are made up of metal-containing anions and cations in which the donor is coordinated to the cation. Data on the viscosity, conductivity, density, phase behaviour and surface tension are presented and these are shown to be significantly different to other related ionic liquids that incorporate quaternary ammonium salts. The conductivity and viscosity are comparable with other ionic liquids and the data fit well to the Hole theory model recently proposed.     

Estimation of pure component properties. Part 4: Estimation of the saturated liquid viscosity of non-electrolyte organic compounds via group contributions and group interactions

A new group contribution method for the prediction of pure component saturated liquid viscosity has been developed. The method is an extension of the pure component property estimation techniques that we have developed for normal boiling points, critical property data, and vapour pressures. Predictions can be made from simply having knowledge of the molecular structure of the compound. In addition, the structural group definitions for the method are identical to those proposed for estimation of saturated vapour pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid viscosity data for more than 1600 components. Results of the new method are compared to several other estimation methods published in literature and are found to be significantly better. A relative mean deviation in viscosity of 15.3% was observed for 813 components (12,139 data points). By comparison, the Van Velzen method, the best literature method in our benchmarking exercise produced a relative mean deviation of 92.8% for 670 components (11,115 data points). Estimation results at the normal boiling temperature were also tested against an empirical rule for more than 4000 components. The range of the method is usually from the triple or melting point to a reduced temperature of 0.75–0.8. Larger than average deviations were observed in the case of molecules with higher rotational symmetry, but no specific correction of this effect was included in this method.     

Calculation of the viscosity of binary liquids at various temperatures using Jouyban-Acree model

Applicability of the Jouyban-Acree model for calculating absolute viscosity of binary liquid mixtures with respect to temperature and mixture composition is proposed. The correlation ability of the model is evaluated by employing viscosity data of 143 various aqueous and non-aqueous liquid mixtures at various temperatures collected from the literature. The results show that the model is able to correlate the data with an overall percentage deviation (PD) of 1.9+/-2.5%. In order to test the prediction capability of the model, three experimental viscosities from the highest and lowest temperatures along with the viscosities of neat liquids at all temperatures have been employed to train the model, then the viscosity values at other mixture compositions and temperatures were predicted and the overall PD obtained is 2.6+/-4.0%.     

Transient molecular dynamics simulations of liquid viscosity for nonpolar and polar fluids

A transient molecular dynamics (TMD) method for obtaining fluid viscosity is extended to multisite, force-field models of both nonpolar and polar liquids. The method overlays a sinusoidal velocity profile over the peculiar particle velocities and then records the transient decay of the velocity profile. The viscosity is obtained by regression of the solution of the momentum equation with an appropriate constitutive equation and initial and boundary conditions corresponding to those used in the simulation. The transient velocity decays observed appeared to include both relaxation and retardation effects. The Jeffreys viscoelastic model was found to model accurately the transient responses obtained for multisite models for n-butane, isobutane, n-hexane, water, methanol, and 1-hexanol. TMD viscosities obtained for saturated liquids over a wide range of densities agreed well for the polar fluids, both with nonequilibrium molecular dynamics (NEMD) results using the same force-field models and with correlations based on experimental data. Viscosities obtained for the nonpolar fluids agreed well with the experimental and NEMD results at low to moderate densities, but underpredicted experimental values at higher densities where shear-thinning effects and viscous heating may impact the TMD simulations.     

Viscosity Arrhenius parameters correlation: extension from pure to binary fluid mixtures

Knowledge of fluids’ physicochemical properties is mandatory for the design and optimisation of industrial processes and products. A data quantity of most importance, in this regard, turns out to be the value of fluid viscosity. Many empirical and semi-empirical formulas have been proposed in the literature to describe the viscosity of pure liquids and binary liquid mixtures. Recently, an interesting equation is proposed for pure solvents correlating the two parameters in the viscosity Arrhenius-type equation, namely the activation energy (E_a) and the pre-exponential factor (A_s). This paper aims to extend the said correlation to binary liquid mixtures. To achieve this purpose, statistical methods are applied using data sets from the literature of some solvent binary mixtures at different compositions and temperatures. The validation of the extended proposed equation for binary liquid mixtures is important since it simplifies the estimation of viscous behaviour and the ensuing calculations.     

Solvation and rotational dynamics of coumarin 153 in ionic liquids: comparisons to conventional solvents

Steady-state and time-resolved emission spectroscopy with 25 ps resolution are used to measure equilibrium and dynamic aspects of the solvation of coumarin 153 (C153) in a diverse collection of 21 room-temperature ionic liquids. The ionic liquids studied here include several phosphonium and imidazolium liquids previously reported as well as 12 new ionic liquids that incorporate two homologous series of ammonium and pyrrolidinium cations. Steady-state absorption and emission spectra are used to extract solvation free energies and reorganization energies associated with the S0 <--> S1 transition of C153. These quantities, especially the solvation free energy, vary relatively little in ionic liquids compared to conventional solvents. Some correlation is found between these quantities and the mean separation between ions (or molar volume). Time-resolved anisotropies are used to observe solute rotation. Rotation times measured in ionic liquids correlate with solvent viscosity in much the same way that they do in conventional polar solvents. No special frictional coupling between the C153 and the ionic liquid solvents is indicated by these times. But, in contrast to what is observed in most low-viscosity conventional solvents, rotational correlation functions in ionic liquids are nonexponential. Time-resolved Stokes shift measurements are used to characterize solvation dynamics. The solvation response functions in ionic liquids are also nonexponential and can be reasonably represented by stretched-exponential functions of time. The solvation times observed are correlated with the solvent viscosity, and the much slower solvation in ionic liquids compared to dipolar solvents can be attributed to their much larger viscosities. Solvation times of the majority of ionic liquids studied appear to follow a single correlation with solvent viscosity. Only liquids incorporating the largest phosphonium cation appear to follow a distinctly different correlation.     

Surface tension and refractive index of pure and water-saturated tetradecyltrihexylphosphonium-based ionic liquids

Experimental data on the surface tension and refractive index of tetradecyltrihexylphosphonium-based ionic liquids with bromide, chloride, decanoate, methanesulfonate, dicyanimide, bis(2,4,4-trimethylpentyl)phosphinate and bis(trifluoromethylsulfonyl)imide anions are reported. The data were obtained for pure and water saturated samples at temperatures from 283 K to 353 K and at atmospheric pressure. The refractive index of the investigated ionic liquids decreases with increasing the water content in the sample. On the other hand, no clearly dependence of the surface tension with the water content up to a weight fraction of 16% was found. The prediction of the refractive index for the studied ionic liquids was also accomplished by a group contribution method and new values for the cation and diverse anions were estimated and proposed. The studied ionic liquids show lower surface tension in comparison with imidazolium-, pyridinium- or pyrrolidinium-based ionic liquids with a similar anion; also they show higher surface entropy than cyclic nitrogen-based fluids which indicates a lower surface organization. The anion dependence of the surface tension and surface entropy for the investigated ionic liquids is weaker than that for short-chain imidazolium-based ionic liquids. Their critical temperatures evaluated from Eötvos and Guggenheim equations are also lower than those of N-heterocyclic ionic fluids.     

Capillary rise of liquids over a microstructured solid surface

The location of the triple line as a function of time has been recorded for a series of organic liquids, with various surface tension to viscosity ratios, wicking upward a rough Cu(6)Sn(5)/Cu intermetallic (IMC) substrate. The complex topographical features of such an IMC rough surface are characterized by surface porosity and surface roughness. A theoretical model for wicking upward a rough surface has been established by treating the rough IMC surface as a two-dimensional porous medium featuring a network of open microtriangular grooves. The model is verified against experimental data. The study confirms that the kinetics of capillary rise of organic liquids in a nonreactive flow regime over a porous surface having arbitrary but uniformly distributed topographical features involves (i) surface topography metrics (i.e., permeability, tortuosity/porosity, and geometry of the microchannel cross section); (ii) wicking features (i.e., contact angle and filling factor); and (iii) physical properties of liquids (i.e., surface tension and viscosity). An excellent agreement between theoretical predictions and experimentally obtained data proves, for a selected filling factor η, validity of the analytically established model. Scaled data sets show that, for a given rough surface topography, (i) wicking kinetics of considered liquids depend on properties of liquids, that is, surface tension to viscosity ratios and contact angles; (ii) the filling factor for all tested liquids is an invariant, offering good prediction within the range of ~0.9-1.0. The distance of the wicking front versus square root of time relationship was well established throughout the whole considered wicking evolution time.     

New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid-molecular solvent mixtures

The low vapor pressure and the versatility of the physico-chemical properties of ionic liquids make them really attractive as an alternative for conventional molecular solvents. The knowledge of their physico-chemical properties (viscosity, conductivity, miscibility with organic solvents and anion-cation interactions) has appeared mandatory for better targeting their applications, although it is generally still lacking or incomplete.This work promotes capillary electrophoresis instrumentation as an integrated apparatus for measurement of viscosity, conductivity and absorbance of pure ionic liquids and ionic liquid-molecular solvent mixtures. Compared to current conventional techniques, the assets of this instrumentation for this purpose are the combined availability of a pressure delivery system, power supply, diode array absorbance detector and thermoregulation device, allowing unattended, automatic and easy operation, involving minimum sample handling. Most importantly, the required sample volume can be reduced to about 50 μL, making this protocol very cost-effective. A protocol was optimized with respect to time, sample consumption and data reliability for the determination of these physico-chemical parameters. Ionic liquids selected for method development and validation differed in the nature of their cation (butyl- and ethyl-methylimidazolium) and anion (trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide). Various molecular solvents were mixed with these ionic liquids (acetonitrile, methanol, dimethylformamide and trifluoroethanol) and the same physico-chemical properties were determined by optimized methods. The knowledge of these data should be of great support in various application areas, including the development of new separation media for capillary electrophoresis and chromatographic techniques.     

Viscosity of Ionic Liquids: Application of the Eyring’s Theory and a Committee Machine Intelligent System

Accurate determination of the physicochemical characteristics of ionic liquids (ILs), especially viscosity, at widespread operating conditions is of a vital role for various fields. In this study, the viscosity of pure ILs is modeled using three approaches: (I) a simple group contribution method based on temperature, pressure, boiling temperature, acentric factor, molecular weight, critical temperature, critical pressure, and critical volume; (II) a model based on thermodynamic properties, pressure, and temperature; and (III) a model based on chemical structure, pressure, and temperature. Furthermore, Eyring’s absolute rate theory is used to predict viscosity based on boiling temperature and temperature. To develop Model (I), a simple correlation was applied, while for Models (II) and (III), smart approaches such as multilayer perceptron networks optimized by a Levenberg–Marquardt algorithm (MLP-LMA) and Bayesian Regularization (MLP-BR), decision tree (DT), and least square support vector machine optimized by bat algorithm (BAT-LSSVM) were utilized to establish robust and accurate predictive paradigms. These approaches were implemented using a large database consisting of 2813 experimental viscosity points from 45 different ILs under an extensive range of pressure and temperature. Afterward, the four most accurate models were selected to construct a committee machine intelligent system (CMIS). Eyring’s theory’s results to predict the viscosity demonstrated that although the theory is not precise, its simplicity is still beneficial. The proposed CMIS model provides the most precise responses with an absolute average relative deviation (AARD) of less than 4% for predicting the viscosity of ILs based on Model (II) and (III). Lastly, the applicability domain of the CMIS model and the quality of experimental data were assessed through the Leverage statistical method. It is concluded that intelligent-based predictive models are powerful alternatives for time-consuming and expensive experimental processes of the ILs viscosity measurement.     

Estimation of the polymer-solvent interaction parameters for polyesters of aliphatic acids

Intrinsic viscosity data are used to estimate the polymer solvent interaction parameters for aliphatic polyesters. The effect of the structure of the polymer chain and solvent molecules is discussed. The results are compared with theoretical calculations based on the equation-of-state theory of pure liquids and their mixtures. The contact energy term X₁₂ is found to be close to zero for benzene and tetrahydrofuran but a strong specific interaction with chloroform is indicated.     

Surface tension correlation for pure polar fluids by a new molecular model and SRK equation of state

In this work, a new model based on molecular thermodynamic was presented to correlate the surface tension of pure polar liquids. This model was developed based on the Davis theory. According to this theory, the surface tension is defined as a function of radial distribution function (RDF) and potential function (PF) as well. The proposed model includes three additive terms; hard sphere, dispersion and polar interactions. The RDF of Kolafa equation of state and Dirac delta function as a PF were used for hard sphere interaction. The RDF expression of Xu and Hu was considered for both dispersion and polar interactions. The presented model has two adjustable parameters, size and energy, which were obtained by optimization of an objective function for each pure fluid. This proposed approach was used for 19 pure polar fluids divided into 6 groups; organic acids, alcohols, ketones, ethers, aldehydes, and water. The average absolute deviation percent (AAD%) obtained for 19 fluids are 0.74. Also the surface tension of these 19 fluids was calculated by the use of SRK EOS and Sugden empirical formula in two cases. In case 1, Sugden's Parachor was calculated from Hugill and van Welsenes correlation and in case 2, it was obtained by optimization of an objective function for each component. The values of AAD% are 43.544 and 2.281 for cases 1 and 2, respectively. These results show the new model, which includes two adjustable parameters, can correlate the surface tension of the pure polar liquids with a high accuracy.