CF4和惰性气体混合物的输运性质的计算

The present work is concerned with determining the viscosity, diffusion, thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including: CF4-He, CF4-Ne, CF4-Ar, CF4-Kr, CF4-Xe from the principle of corresponding states of viscosity by the inversion technique. The Lennard-Jones (12-6) model potential is used as the initial model potential. The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities, diffusions, thermal diffusion factors, and thermal conductivities. The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%, respectively.     

Transport properties of dilute ammonia-noble gas mixtures from new intermolecular potential energy functions

Previously we have determined the dilute mixture transport properties of slightly polar fluorocarbons using the inverted intermolecular potential energies(Ind.Eng.Chem.Res.45(2006)9211-9223).In the present paper,the corresponding states correlations for reduced viscosity collision integrals were employed to obtain effective un-like interaction potential models for dilute binary mixtures of highly polar molecule ammonia with noble gases. The inverted potentials were fitted to the Morse-Spline-van der Waals(MSV),model potential.The method of least-squares fitting was then applied to identify best consistence force parameters for each ammonia-noble gas mixture,taking advantage of experimental viscosities,diffusion coefficients and thermal conductivities. The proposed potential models were compared with those obtained from other sources,in order to assess the ex-tent of their validity. The potentials were later employed to calculate transport properties of the studied mixtures.Then,results were compared with those reported in the literature,which led to the acceptable agreement.     

离子液体[C4mim][PF6]与N, N-二甲基甲酰胺二元混合物在298.15 K～318.15 K的密度和粘度

Viscosities and densities for 1-butyl-3-methylimidazolium hexafluorophosphate （[C4mim][PF6]） and N, N-dimethylformamide （DMF） binary mixtures have been measured at the temperature range from 293.15 K to 318.15 K. It is shown that the viscosities and densities decrease monotonously with temperature and the content of DMF. Various correlation methods including Arrhenius-like equation, Sedclon et al.＇s equation, Redlich-Kister equation with four parameters, and other empirical equations were applied to evaluate these experimental data. A model based on an equation of state Ior estimating the viscosity of mixtures containing ionic liquids were proposed by coupling with the excess Gibbs free energy model of viscosity, which can synchronously calculate the viscosity and the molar volume. The results show that the model gives a deviation of 8.29% for the viscosity, and a deviation of 1.05% for the molar volume when only one temperature-independent adjustable parameter is adopted. The correlation accuracy is further improved when two parameters or one temperature-dependent parameter is used.     

稀四氟化碳气体混合物传递性质的确定(英文)

In our previous work, we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride (CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique. The present work is a continuation of our studies on determining the transport properties of binary gas mixtures CF4 with some gases including three diatomic molecules CO, N2, and O2, a linear polyatomic CO2, and two non-linear polyatomic molecules SF6 and CH4. The Chapman-Enskog and Vesovic-Wakeham methods as well as inversion procedure are used to determine the viscosities, diffusivities, and thermal conductivities, which deviates from the literature values within 1%, 4%, and 5%, respectively.     

Determination of physical properties for the mixtures of [BMIM]Cl with different organic solvents

Physical properties including refractive index, density, viscosity and conductivity for binary mixtures of 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) and different organic solvents at 298.15 K have been investigated. Ex-cess molar volumes have been calculated and obtained data has been fitted by the Redlich–Kister equation. The density and refractive index were found to increase with increasing concentration of [BMIM]Cl, however, excep-tions do exist as in the case of dimethyl sulfoxide (DMSO)/[BMIM]Cl. For DMSO/[BMIM]Cl, the density decreases with increasing concentration. The addition of different organic solvents was able to disrupt the interactions within mixtures, leading to free mobility of ions. The free mobility of ions has been found to enhance conductivity and decrease viscosity to varying extents in al mixtures studied. It has been observed that solubility parameters, dielectric constants and composition of the solvents used play a vital role in determining the resultant properties. The data obtained wil play an important role in understanding the effect of the addition of organic solvents in ILs to enhance their applicability.     

Excess Molar Volumes and Viscosities of Binary Mixtures of p-Xylene with Cyclohexane, n-Heptane, n-Octane, Sulfolane, N-Methyl-2-pyrrolidone and Acetic Acid at 303.15 K and 323.15 K and Atmospheric Pressure

Experimental data on density and viscosity at 303.15 K and 323.15 K are presented for the binary mixtures of p-xylene with cyclohexane, n-heptane, n-octane, sulfolane, N-methyl-S-pyrrolidone and acetic acid. From these data, the excess molar volume and deviations in viscosity have been calculated. The computed quantities have been fitted to the Redlich-Kister Equation to derive coefficients and estimate the standard error values. Results are discussed in terms of intermolecular interactions.     

用定标粒子理论研究不同温度下2-甲基-2-丙醇与腈二元液相混合物的超额热力学参数和超音速度理论估值(英文)

Density, ρ, ultrasonic speed, u, and viscosity, η, of binary mixtures of 2-methyl-2-propanol (2M2P) with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN) including those of pure liquids are measured over the entire composition range at temperatures 298.15, 303.15 and 308.15 K. From these experimental data, the excess available volume, E a V , excess free volume, E f V , excess isothermal compressibility, E T β , excess thermal expansion coefficient, E α , and excess internal pressure, E i π , are calculated. The variation of these properties with composition and temperature are discussed in terms of molecular interactions between unlike molecules of the mixtures. It is found that the values of E a V , E f V , E T β and E α are positive and those of E i π are negative for all the mixtures at each temperature studied, indicating the presence of weak interactions between 2M2P and AN/PN/BN molecules. The variations of E a V , E f V , E T β , E α and E i π values with composition indicate that the interactions in these mixtures follow the order: ANPNBN, i.e., the 2M2P-nitrile interaction decreases with the increase of alkyl chain length in these nitrile molecules. In addition, the theoretical ultrasonic velocity is calculated using the scaled particle theory and compared with the experimental values.     

借助变阱宽方阱链流体状态方程模拟非电解质体系表面张力和粘度(英文)

The equation of state(EOS)for square-well chain fluid with variable range(SWCF-VR) developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids(ILs).A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation(AAD)of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.     

对二甲苯与环己烷、正庚烷、正辛烷、环丁砜和N-甲基-2-吡咯烷酮和乙酸二元混合物在303．15K和323．15K的超额体积和黏度

Experimental data on density and viscosity at 303.15K and 323.15K are presented for the binary mixtures of p-xylene with cyclohexane, n-heptane, n-octane, sulfolane, N-methyl-2-pyrrolidone and acetic acid. From these data, the excess molar volume and deviations in viscosity have been calculated. The computed quantities have been fitted to the Redlich-Kister Equation to derive coefficients and estimate the standard error values. Results are discussed in terms of intermolecular interactions.     

Physicochemical properties of aqueous solutions of sodium glycinate in the non-precipitation regime from 298.15 to 343.15 K

The physicochemical properties, including the density, viscosity, and refractive index of aqueous solutions of sodium glycinate as a solvent for CO2 absorption in the non-precipitation regime were measured under the wide temperature range of 298.15 to 343.15 K. The concentration of the sodium glycinate in an aqueous form in the non-precipitation regime was identified up to 2.0 mol·L?1. The coefficients of thermal expansion values were estimated from measured density data. It was found that, the densities, viscosities and refractive indices of the aqueous sodium glycinate decrease with an increase in temperature, whereas with increasing sodium glycinate concentration in the solution, all three properties increase. Thermal expansion coefficients slightly increase with rising temperature and concentration. The measured values of density, viscosity and refractive index were correlated as a function of temperature by using the least squares method. The predicted data obtained from correlation equations for all measured properties were in fairly good agreement with the experimental data.     

Viscosity of crude oils

A series of experimental viscosity data for seven different North Sea oils is presented. A new corresponding states method for prediction of the viscosity of both gaseous and liquid hydrocarbon fluids has been developed. The required input is critical constants and the molecular weight of each component. Very accurate results were obtained for the crude oils using the C₇₊-characterization procedure of Pedersen et al.[1]. The viscosity correlation is also shown to give satisfactory results for pure hydrocarbons and binary mixtures.     

Production of natural graphite particles with high electrical conductivity by grinding in alcoholic vapors

Natural graphite particles with a high crystallinity, which were sieved to obtain particles less than 63 μm, were ground with a ball mill under a dry atmosphere and various alcoholic vapors such as i-C₃H₈OH, n-C₃H₈OH, C₂H₅OH, and CH₃OH. The size and flakiness of the ground products and the electrical conductivity of the films made from the ground products were experimentally examined. Grinding the particles under alcoholic vapors slowly reduced the particle size and was similar to grinding in dry air, but grinding in alcoholic vapors produced flakier products. The graphite films, which were composed of flakier particles and were ground in alcoholic vapor, displayed higher electrical conductivities than the feed graphite particles. The products ground in C₂H₅OH, i-C₃H₇O and n-C₃H₇OH vapors had 50% or less of the specific resistance of the feed particles.     

Pure and mixed gas CH4 and n-C4H10 permeability and diffusivity in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ permeability coefficients in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures from −20 to 35 °C. CH₄ partial pressures range from 1.1 to 14.6 atm, and n-C₄H₁₀ partial pressures range from 0.02 to 1.8 atm. CH₄ permeability decreases with increasing n-C₄H₁₀ upstream activity (f/f_sat) in the feed. For example, at −20 °C, CH₄ permeability decreases by more than an order of magnitude, from 52,000 to 1700 Barrer, as n-C₄H₁₀ activity increases from 0 to 0.73. In contrast, n-C₄H₁₀ mixed gas permeability is essentially unaffected by the presence of CH₄. The depression of CH₄ permeability in mixtures is a result of competitive sorption and blocking effects, which reduce both CH₄ mixture solubility and diffusivity, respectively. Diffusion coefficients of n-C₄H₁₀ and CH₄ in mixtures were calculated from mixture permeability and mixture solubility data. The CH₄ concentration-averaged diffusion coefficient generally decreases as n-C₄H₁₀ activity increases. On the other hand, the n-C₄H₁₀ diffusion coefficient is essentially unaffected by the presence of CH₄. Pure and mixed gas activation energies of permeation and diffusion of CH₄ and n-C₄H₁₀ are reported. The mixed gas n-C₄H₁₀/CH₄ permeability selectivity increases with increasing n-C₄H₁₀ activity and decreasing temperature, and it is higher than pure gas estimates would suggest. Mixture diffusivity selectivity also increases with increasing n-C₄H₁₀ activity. The difference between pure and mixed gas permeability selectivity arises from both solubility and diffusivity effects. The dual mode mixed gas permeability model describes the mixture permeability data reasonably well for n-C₄H₁₀. However, the model must be modified to accurately describe the methane data by accounting for the decrease in methane diffusivity due to the presence of n-C₄H₁₀ (i.e., blocking). Even though the penetrant concentrations are rather significant at some of the conditions considered, no evidence is observed for phenomena such as multicomponent coupling that would require a model more complex than the binary form of Fick's law. That is, Fick's law in its simplest form adequately describes the experimental data.     

The effects of fullerene (C60) crystal structure on its electrochemical capacitance

The electrochemical properties of different types of fullerene crystals (x-C₆₀), having hollow-long cylindrical (C-C₆₀), hollow-long square (S-C₆₀), and thick solid-short hexagonal (H-C₆₀) shapes were investigated. The prepared x-C₆₀ samples had specific dimensions with respect to aspect ratio (12.0, 6.7, and 1.5) and lattice spacing distance (1.12, 1.04, and 1.00 nm). Interestingly, it was possible to control the aspect ratio and lattice spacing distance by adjusting the molecular ratio of C₆₀ to the aromatic solvent (m-xylene) used in the preparation. In addition, the number of m-xylene molecule in the x-C₆₀ crystal structure increased with decreasing ratio of x-C₆₀ to m-xylene in the solution, corresponding to ca. C₆₀·0.83m-xylene (for C-C₆₀), C₆₀·0.39m-xylene (for S-C₆₀), and C₆₀·0.36m-xylene (for H-C₆₀). A more ordered arrangement of m-xylene molecules resulted in an improved electrochemical capacitance of x-C₆₀. Importantly, in the case of the regular structure (C-, S-, H-C₆₀), when m-xylene was assembled in the x-C₆₀ structure, the large lattice spacing distance increased. This explains why the C-C₆₀ sample had the largest electrochemical capacitance, compared to the S- and H-C₆₀ samples. Such a configuration would allow for a high charge accumulation and the formation of a donor-acceptor complex, which would permit an easier charge transfer.     

CF_4和惰性气体混合物的输运性质的计算

The present work is concerned with determining the viscosity, diffusion, thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including: CF_4-He, CF_4-Ne, CF_4-Ar, CF_4-Kr, CF_4-Xe from the principle of corresponding states of viscosity by the inversion technique. The Lennard-Jones (12-6) model potential is used as the initial model potential. The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities, diffusions, thermal diffusion factors, and thermal conductivities. The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%, respectively.     

Experimental data vs. 3-D model calculations of HFCVD processes: correlations and discrepancies

An existing 3-D model [Mankelevich et al. Diamond Relat. Mater. 7 (1998) 1133] has been used to explain experimentally measured spatially resolved CH₃ radical number densities in hot filament CVD reactors operating with both CH₄/H₂ and C₂H₂/H₂ process gas mixtures and to examine in detail the process of C₂↔C₁ inter-conversion in the gas phase. It has been shown that cooler regions distant from the filament need to be modelled in order to obtain the significant C₂→C₁ conversion observed in HFCVD reactors with C₂H₂/H₂ process gas mixtures. The origin and effect of the non-equilibrated H₂ molecule vibrational state population distribution are studied for the first time in the context of HFCVD reactor models.     

The isomerization and metathesis of n-butenes: I. Unreduced molybdena-alumina catalysts

A significant change in the catalytic characteristics of an unreduced molybdena-alumina catalyst occurred at room temperature with increasing duration of contact with the reactant cis-2-butene. Butene isomerization over the fresh catalyst was effected by an acidic mechanism with the concomitant intermolecular transfer of H and D. The chief diagnostic characteristics for this mechanism were maintained throughout pulse experiments, but changed to those characteristic of isomerization by metathesis after soaking in butene for 15 min or when a static recirculation reactor was used, i.e., with increasing contact time, the acidic character of the catalyst decreased and the activity for metathesis increased. Thus, in the later stages of the reaction, equimolar mixtures of cis-2-butene d₀ and d₈ isomerized to produce cis- and trans-C₄H₄D₄, C₄H₈, and C₄D₈ in ratios of 2:1:1 without other hydrogen scrambling.     

n-Paraffins obtained by extraction and mild stepwise hydrogenation of Wandoan coal

Wandoan Australian coal was separated into three parts by the float and sink method. The light(I) and medium(II) density fractions were extracted both by benzene-ethanol using ultrasonic irradiation and at 200 °C in an autoclave. The residue was hydrogenated in steps to obtain the n-hexane soluble part, raising the reaction temperature from 320 to 390 °C. The n-paraffins were analysed for each extract. Those from ambient extraction showed a bimodal distribution in the C₁₂-C₃₁ region with odd carbon numbers predominating in the C₂₃-C₃₁ region. In the case of the 200 °C extract a smooth distribution appeared at C₁₂-C₃₁. For the first hydrogenation, the paraffins were distributed at C₁₂-C₃₂ with a slight predominance of odd-paraffins in the C₂₃-C₃₁ region, and only one maximum at C₂₆. When the temperature was increased from 320 to 390 °C the distribution approached two maxima at C₁₂ and C₂₆, with the former increasing in amount with the temperature. At the final stage there is a slight predominance of even paraffins in the region C₁₄-C₂₀ which is believed to originate from esters, acids, alcohols etc. It was also found that there was no serious difference between part I and II in the distribution of n-paraffins, but part I yielded greater amounts of saturated hydrocarbons than the corresponding part II.     

New inversion and ab initio intermolecular potentials for supercritical fluorine: Calculation of some properties and MD simulation

A new pair-potential energy function of fluorine has been determined via the inversion of reduced viscosity collision integrals. The potential reproduces the second virial coefficient, viscosity, and thermal conductivity of supercritical fluorine in good accordance with experimental data. We have also determined the (F₂)₂ potential using different ab initio methods at different geometries. Molecular dynamics simulation has been also performed to obtain pressure of supercritical fluorine using the inversion pair-potential supplemented by Feynman–Hibbs quantum correction and the weighted ab initio potential using the CCSD(T)/aug-pvdz method. To consider many-body interactions, the simple three-body potential of Hauschild and Prausnitz [7] used with the inversion potential to improve the properties without requiring an expensive three-body calculation. We have also calculated the three-body interactions for (F₂)₃ system using the ab initio computations at different orientations. Our results indicated that the three-body potentials improve the two-body supercritical values.