Experimental measurement and modeling of the vapor–liquid equilibrium of carbon dioxide + chloroform

Isothermal bubble and dew points, saturated molar volumes, and mixture critical points for binary mixtures of carbon dioxide+chloroform (trichloromethane) (CO₂/CHCl₃) have been measured in the temperature region 303.15–333.15 K and at pressures up to 100 bar. Mixture critical points are reported at 313.15, 323.15, and 333.15 K. The data were modeled with the Peng–Robinson equation of state using both the van der Waals-1 (vdW-1) mixing rule and the Wong–Sandler (WS) mixing rule incorporating the UNIQUAC excess free energy model. The WS mixing rule provided a better representation of the data than did the vdW-1 mixing rule, though with three adjustable parameters instead of one. The extrapolating ability of both of the mixing rules was investigated. Using the parameters regressed at 323.15 K, the WS mixing rule yielded better extrapolations for the composition dependence at 303.15, 313.15, and 333.15 K than the vdW-1 mixing rule.     

Investigation on isobaric vapor–liquid equilibrium for acetic acid + water + methyl ethyl ketone + isopropyl acetate

Isobaric vapor–liquid equilibrium (VLE) data for acetic acid + water, acetic acid + methyl ethyl ketone (MEK), MEK + isopropyl acetate, acetic acid + MEK + water and acetic acid + MEK + isopropyl acetate + water are measured at 101.33 kPa using a modified Rose cell. The nonideal behavior in vapor phase of binary systems measured in this work is analyzed through calculating fugacity coefficients since mixture containing acetic acid deviates from ideal behavior seriously in vapor phase due to the associating effect of acetic acid. Combined with Hayden–O’Connell (HOC) equation, the VLE data of the measured binary systems for acetic acid + water, acetic acid + MEK and MEK + isopropyl acetate are correlated by the NRTL and UNIQUAC models. The NRTL model parameters obtained from correlating data of binary system are used to predict the VLE data of the ternary and quaternary systems, and the predicted values obtained in this way agree well with the experimental values.     

Vapor–liquid equilibrium in the system ethane + ethylene glycol

The solubility of ethane in ethylene glycol (EG) has been determined at temperatures in the range 298–398 K at pressures up to 20 MPa. The experimental results were correlated by the Peng–Robinson equation of state, and interaction parameters have been obtained for this system. The parameters in the Krichevsky–Ilinskaya equation were calculated from these interaction parameters.     

Isothermal vapor–liquid equilibria for different binary mixtures involved in the alcoholic distillation

Isothermal vapor–liquid equilibrium (VLE) data for five binary systems ethyl acetate + 3-methyl-1-butanol, ethanol + 3-methyl-1-butanol, ethyl acetate + 2-methyl-1-butanol, ethanol + 2-methyl-1-butanol, ethyl acetate + 2-methyl-1-propanol, involved in the alcoholic distillation have been determined experimentally by headspace gas chromatography. The composition in the liquid phase was corrected with the help of an iterative method by means of a G^E model. However, due to the large density difference between the liquid and the vapor, the correction of the liquid phase composition is nearly negligible. All the binary mixtures show positive deviations from Raoult's law. The experimental VLE data are well predicted by using the modified UNIFAC model (Dortmund).     

Isobaric vapor–liquid equilibria for the system 1-pentanol–1-propanol–water at 101.3 kPa

Consistent vapor–liquid equilibrium data for the ternary system 1-pentanol–1-propanol–water is reported at 101.3 kPa at temperatures in the range of 362–393 K. The VLE data were satisfactorily correlated with UNIQUAC model.     

High-pressure vapor–liquid equilibria in the nitrogen–n-pentane system

New experimental vapor–liquid equilibrium data of the N₂–n-pentane system were measured over a wide temperature range from 344.3 to 447.9 K and pressures up to 35 MPa. A static-analytic apparatus with visual sapphire windows and pneumatic capillary samplers was used in the experimental measurements. Equilibrium phase compositions and vapor–liquid equilibrium ratios are reported. The new results were compared with those reported by other authors. The comparison showed that the pressure–composition data reported in this work are in good agreement with those determined by others but they are closer to the mixture critical point at each temperature level. The experimental data were modeled with the PR and PC-SAFT equations of state by using one-fluid mixing rules and a single temperature independent interaction parameter. Results of the modeling showed that the PC-SAFT equation fit the data satisfactorily even at the highest temperatures of study.     

An activity coefficient model for predicting salt effects on vapor–liquid equilibria of mixed solvent systems

In the present study, an activity coefficient model, based on the concept of local volume fractions and the Gibbs–Helmholtz relation, has been developed. Some modifications were made from Tan–Wilson model (1987) and TK–Wilson model (1975) to represent activity coefficients in mixed solvent–electrolyte systems. The proposed model contains two groups of binary interaction parameters. One group for solvent–solvent interaction parameters corresponds to that given by the TK–Wilson model (1975) in salt-free systems. The other group of salt–solvent interaction parameters can be calculated either from vapor pressure or bubble temperature data in binary salt–solvent systems. It is shown that the present model can also be used to describe liquid–liquid equilibria. No ternary parameter is required to predict the salt effects on the vapor–liquid equilibria (VLE) of mixed solvent systems. By examining 643 sets of VLE data, the calculated results show that the prediction by the present model is as good as that by the Tan–Wilson model (1987), with an overall mean deviation of vapor phase composition of 1.76% and that of the bubble temperature of 0.74 K.     

Prediction of viscosities and vapor–liquid equilibria for five polyhydric alcohols by molecular simulation

Reverse nonequilibrium molecular dynamics in the canonical ensemble and coupled–decoupled configurational-bias Monte Carlo simulations in the Gibbs ensemble were used to predict the low-shear rate Newtonian viscosities and vapor–liquid coexistence curves for 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, and 1,2,4-butanetriol modeled with the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field. Comparison with available experimental data demonstrates that the TraPPE-UA force field yields very good predictions of the viscosities and vapor–liquid coexistence curves. A detailed analysis of liquid structure and hydrogen bonding is provided.     

Low pressure vapor–liquid equilibrium in ethanol + congener mixtures using the Wong–Sandler mixing rule

Phase equilibrium in binary ethanol mixtures found in alcoholic beverage production has been analyzed using a cubic equation of state (EoS) and suitable mixing and combining rules. The main objective of the study is the accurate modeling of the congener concentration in the vapor phase (substances different from ethanol), considered to be an important enological parameter in the alcohol industry. The Peng–Robinson (PR) equation of state has been used and the Wong–Sandler (WS) mixing rules, that include a model for the excess Gibbs free energy, have been incorporated into the equation of state constants. In the Wong–Sandler mixing rules the van Laar (VL) model for the excess Gibbs energy has been used. This combination of equations of state, mixing rules and combining rules are commonly applied to high pressure phase equilibrium and have not yet been treated in a systematic way to complex low pressure ethanol mixtures as done in this work. Nine binary ethanol + congener mixtures have been considered for analysis. Comparison with available literature data is done and the accuracy of the calculations is discussed, concluding that the model used is accurate enough for engineering applications.     

Isothermal vapor–liquid equilibria and excess molar volumes for 2-methyl pyrazine (2MP) containing binary mixtures

2-Methyl pyrazine (2MP) has led to significant interest for its industrial and pharmaceutical uses. The new vapor–liquid equilibria (VLE) at 353.15 K and excess molar volumes (V^E) at 298.15 K over the whole mole fraction range for seven binaries (water, n-hexane, cyclohexane, n-heptane, methylcyclopentane (MCP), methylcyclohexane (MCH) and ethyl acetate (EA) with 2MP) have been measured. VLE were measured by using headspace gas chromatography and V^E were determined using precision density meter. The water+2MP system has only the minimum boiling azeotrope. The experimental VLE and V^E data were well correlated in terms of common g^E models and Redlich–Kister equation, respectively.     

Ab initio study of the conformational equilibrium of ethylene glycol

Summary The conformational equilibrium of ethylene glycol (CH₂OHCH₂OH) has been examined by performing geometry optimizations at the 6-31G*, MP2/6-31G* and 6-31G** levels. Final energies have been calculated at the MP3 level with the optimized geometries. The two most stable conformers are atGg andgGg but it is verified that the inclusion of electronic correlations reduces their energy difference of 0.6 kcal/mol at the HF level to less than 0.2 kcal/mol. The possible coexistence of the two most stable conformers is in agreement with some previous studies of Frei et al. For thetXg conformer a detailed analysis of the intramolecular potential as a function of rotation around the C-C bond is also reported.     

Vapor–liquid equilibria and excess properties for methyl tert-butyl ether (MTBE) containing binary systems

Methyl tert-butyl ether (MTBE) is recently widely used in the chemical and petrochemical industry as a non-polluting octane booster for gasoline and as an organic solvent. The isobaric or isothermal vapor–liquid equilibria (VLE) were determined directly for MTBE+C₁–C₄ alcohols. The excess enthalpy (H^E) for butane+MTBE or isobutene+MTBE and excess volume (V^E) for MTBE+C₃–C₄ alcohols were also determined. Besides, the infinite dilute activity coefficient, partial molar excess enthalpies and volumes at infinite dilution (γ^∞, H^E,∞, V^E,∞) were calculated from measured data. Each experimental data were correlated with various g^E models or empirical polynomial.     

Isobaric vapor–liquid equilibria for acetone + methanol + lithium nitrate at 100 kPa

Isobaric vapor–liquid equilibria for the ternary system acetone + methanol + lithium nitrate have been measured at 100 kPa using a recirculating still. The addition of lithium nitrate to the solvent mixture produced an important salting-out effect and the azeotrope tended to disappear for small contents of salt. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of the Mock's model were estimated. These parameters were used to predict the ternary vapor–liquid equilibrium which agreed well with the experimental one.     

High-pressure vapor–liquid and vapor–liquid–liquid equilibria in the carbon dioxide + 1-heptanol system

Vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE) data for the carbon dioxide + 1-heptanol system were measured at 293.15, 303.15, 313.15, 333.15 and 353.15 K. Phase behavior measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between 0.58 and 14.02 MPa. The Soave–Redlich–Kwong (SRK)-EOS coupled with Huron–Vidal (HV) mixing rules and a reduced UNIQUAC model, was used in a semi-predictive approach, in order to represent the complex phase behavior (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behavior is qualitatively correct predicted.     

Vapor–liquid equilibria and excess volumes of the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate at 101.325 kPa

Isobaric vapor–liquid equilibrium data have been experimentally determined at 101.3 kPa for the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate. No azeotrope was found in any of the systems. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC liquid-phase equations and the corresponding binary interaction parameters are reported. The densities and derived excess volumes for the three mixtures are also reported at 298.15 K.     

纤维二糖与葡萄糖催化转化制备乙二醇(英文)

选用纤维二糖作为探针分子,探索纤维素催化转化制备乙二醇过程的反应路径.分别考察了纤维二糖和葡萄糖在双组分催化剂H2WO4和Ru/C下的催化反应活性.结果表明,乙二醇不仅来自于纤维二糖水解产物葡萄糖的逆羟醛缩合作用,同时也可以来自于纤维二糖的直接逆羟醛缩合过程.而且,纤维二糖的直接逆羟醛缩合作用对糖苷键的水解也有一定的促进作用.比较发现,钨基催化剂作用下纤维二糖的逆羟醛缩合反应活性比葡萄糖要低,因此乙醇醛可以缓慢产生并在Ru/C催化剂上迅速加氢生成乙二醇.使得以纤维二糖作为原料比以葡萄糖作为原料时获得更高的乙二醇收率.     

Solid–liquid equilibrium of K2SO4 in solvent mixtures at different temperatures

The objective of the present work is to represent the solid–liquid equilibrium of potassium sulfate in diverse water + organic solvent mixtures. This representation is carried out between 288.15 and 318.15 K in the following solvent mixtures: water + 1-propanol, water + methanol, water + ethanol and water + acetone. The experimental solubility data of the potassium sulfate in the diverse mixed solvents were obtained from literature, and the thermodynamic representation of the phase equilibrium is based on a simple methodology reported in the literature. Good agreements are observed between the results obtained in this work and the experimental solubility data of K₂SO₄ in the different solvent mixtures.Since these systems present a notable decrease in solubility owing to the effect of the cosolvent, making them potentially suitable for separating potassium sulfate by drowning-out the crystallization process, the amounts of salt precipitated, as a function of the weight percent of cosolvent, was calculated for the four systems analyzed. In addition, the optimum yield was estimated as function of the mass fraction of 1-propanol for the K₂SO₄ + water + 1-propanol system.     

Isothermal vapor–liquid equilibria for binary mixtures of benzene, toluene, m-xylene, and N-methylformamide at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibrium (VLE) at 333.15 K and 353.15 K for four binary mixtures of benzene + toluene, benzene + N-methylformamide, toluene + m-xylene and toluene + N-methylformamide have been obtained at pressures ranged from 0 kPa to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. The P–x–y diagram and the activity coefficient indicate that two mixtures of benzene + toluene and toluene + m-xylene were close to the ideal solution. However, two mixtures containing N-methylformamide present a large positive deviation from the ideal solution. The excess Gibbs energy in the benzene + toluene mixture is negative indicates that it is an exothermic system.     

Vapor–liquid equilibrium data and critical points for the system H2S+COS. Extension of the PSRK group contribution equation of state

Isothermal vapor–liquid equilibrium data for the binary system hydrogen sulfide+carbonyl sulfide were measured in the temperature range from 232 to 293 K using the static-synthetic technique. From the isothermal P−x data, the azeotropic conditions were derived. The critical line of this system was visually detected in a flow apparatus. Interaction parameters for this binary system were fitted simultaneously to all the experimental VLE and critical data for the Predictive Soave–Redlich–Kwong group contribution equation of state.     

Solid–liquid phase equilibrium in the systems of LiBr–H2O and LiCl–H2O

A set of empirical temperature-molar fraction expressions for solid–liquid equilibrium curves of LiBr–H₂O and LiCl–H₂O systems is presented. The expressions are based upon a body of experimental data that have been compiled and critically evaluated. The equations cover the full composition range for LiCl–H₂O system and compositions up to the salt mole fraction of x = 0.46 (i.e. mass fraction of w=0.805) for LiBr–H₂O, corresponding to transition from monohydrate to anhydrate. Temperatures and solution compositions at the eutectic point and at transition points between hydrates have been determined from intersections of the curves corresponding to the adjacent hydrate ranges of the phase diagram. Equations of a special structure were used, involving the coordinates of the transition points as parameters, which makes possible their direct non-linear optimization. To obtain more reliable results, a procedure was employed optimizing both the temperature–composition and composition–temperature equations simultaneously. The uncertainty in the obtained values of the transition point coordinates are estimated to be of the order of 1 K for temperature and 0.001 for the composition expressed in salt mole fraction. Gaps in the database are shown to give experimenters orientation for future research.