NRTL Equation Research Articles

Experimental determination of liquid-liquid equilibrium data and their representation using the UNIQUAC and NRTL equations

Knowledge of physical and chemical data is essential in process engineering, including the fluid phase equilibria, important phenomena for the design and simulation of many separation processes such as distillation and liquidliquid extraction. One important information concerns the phase diagram. Many researches [1-4] have investigated multicomponent systems in order to understand and provide further information about the thermodynamic properties of such systems and representation of phase equilibria. In this study an apparatus has been specially developed and implemented, it is based on a « staticanalytic » method (similar to the one of Laugier and Richon [5]) with two liquids phase samplers in order to determine experimental « liquid – liquid » equilibrium data [6] ; mixtures of known overall composition were prepared directly inside the equilibrium cell. The analytical work was carried out using a Perichrom (France) gas chromatograph equipped with a thermal conductivity detector (TCD) connected to a data acquisition system. The need to acquire good « liquid – liquid » equilibrium data is important, but it is also essential to be able to represent accurately using appropriate models and thus be able to calculate the phase equilibria in all conditions of use, for this the Simulis software from Prosim (Toulouse, France) is used with the NRTL [7] (Non Random Two Liquids) and UNIQUAC [8] (Universal Quasi Chemical) activity coefficient models to correlate the experimental data In this study the results for the systems (water1propanol1-pentanol) and (waterethanol1-pentanol) were considered. The reliability of the experimental data obtained was successfully verified by applying the Othmer-Tobias [9], Bachman [10] and Hand [11] correlations.

Liquid–Liquid Equilibria of the Methanol + Ethylbenzene + Methylcyclohexane Ternary System at 278.15, 283.15, and 293.15 K

Liquid–liquid equilibria of the methanol + ethylbenzene + methylcyclohexane ternary system are reported at 278.15, 283.15, and 293.15 K. The effect of the temperature on the liquid–liquid equilibrium is discussed. All chemical concentrations were quantified by gas chromatography using a thermal conductivity detector. Experimental data for the ternary system are compared with values calculated by the NRTL and UNIQUAC equations. It was found that both equations gave comparable quality representations of the experimental data for this ternary system. Distribution curves were also analyzed. Data for the ternary system is available from the literature at 303.15 K.

Flash point of organic binary mixtures containing alcohols: experiment and prediction

Abstract The flash points of three organic binary mixtures containing alcohols were measured in the present work. The experimental data was obtained using the Pensky-Martens closed cup tester. The experimental data were compared with the values calculated by the Liaw model. Activity coefficients were calculated by the Wilson equation and NRTL equation. The accuracy of predicted flash point values is dependent on the thermodynamic model used for activity coefficient.

Solubility and partition coefficient of p-toluic acid in p-xylene and water

The solubility and partition coefficient of p-toluic acid in p-xylene and water at ambient pressure were measured over the temperature range of 303.2–353.2K. The measured solubility data and partition coefficient data were well correlated by the NRTL equation. The well-documented p-toluic acid–water system was used to validate the reliability of the sampling and analytical techniques employed. The results showed that the solubility of p-toluic acid in p-xylene and water increases with the temperature increase. The partition coefficient of p-toluic acid between p-xylene and water increases with the increasing initial mass of p-toluic acid, but decreases with the rising temperature. The equilibrium data of the ternary system are essential for the extraction process design and scale-up in the PTA wastewater recovery and treatment.

Design calculations of an extractor for aromatic and aliphatic hydrocarbons separation using ionic liquids

AbstractThe study concentrates on the separation of aromatic hydrocarbons from aliphatic hydrocarbon mixtures using ionic liquids as a new alternative of extraction solvents. Influence of the phase equilibrium description accuracy on the separation equipment design using different thermodynamic models was investigated. As a model system, a heptane-toluene binary mixture was chosen, employing 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES) ionic liquid as an extractive solvent. Liquid-liquid equilibrium (LLE) data of the ternary system were calculated using NRTL equations with different quality model parameters. Model 1 corresponds to the NRTL equation with the original binary parameters evaluated independently from the respective binary equilibrium data. Model 2 is represented by an NRTL equation extended by the ternary correction term (with the original binary parameters and ternary correction term parameters evaluated from the ternary tie-lines). Model 3, i.e. the NRTL equation with binary model parameters determined via ternary LLE data regression using ASPEN Plus, was taken from Meindersma et al. (2006). Continuous-flow liquidphase extraction was simulated considering a cascade of mixer-settler type extractors according to the Hunter-Nash scheme (Hunter & Nash, 1934). Based on the simulation results, for a preset separation efficiency criterium, different accuracies of the equilibrium description caused serious discrepancies in the separation equipment design, e.g. in the number of theoretical stages, solvent to feed ratio, and product purity.

Vapour–liquid equilibria and excess enthalpies of the binary mixtures 1-pentanol with 2,2,4-trimethylpentane or n-heptane

Accurate experimental data of vapour–liquid equilibria (VLE) and excess enthalpies are reported for the binary systems (1-pentanol+2,2,4-trimethylpentane) and (1-pentanol+n-heptane). An isothermal total pressure cell was used for measuring the VLE at T=313.15K. The data were correlated using Margules, Wilson, NRTL and UNIQUAC equations. The enthalpies of mixing were measured at two different temperatures T=(298.15 and 313.15)K using an isothermal flow calorimeter and were correlated by the Redlich–Kister equation. The thermodynamic behaviour is discussed.

Tag 개방식 장치를 이용한 tert-Pentanol+n-Decane 계의 하부인화점 측정

인화점은 공기 속 가연성 증기의 농도가 연소하한계(lower flammability limit)에 도달할 때의 최저 온도이며, 산업현장에서 사용하는 물질들의 화재와 폭발의 위험성을 결정하는 중요한 물성치이다. 단일 성분의 인화점 정보는 여러 문헌에서 얻을 수 있으나, 이성분계 혼합물의 인화점은 충분히 제공되어 있지 않다. 본 연구에서는 tert-pentanol+n-decanel 계의 인화점을 Tag 개방식 장치를 이용하여 측정하였다. 실험값은 Raoult의 법칙과, Wilson 식과 NRTL 식을 활용한 최적화 기법에 의해 계산된 값들과 비교되었다. 최적화 기법에 의한 계산값이 Rauolt의 법칙에 의한 계산값 보다 실험값에 더욱 근접하였다. The flash point the lowest temperature at which the concentration of vapor of the substance in the air reaches the lower flammability limit(LFL), and is one of the most important physical properties used to determine the potential for fire and explosion hazards of industrial materials. The most published flash point data was for pure components and the flash points of the binary solutions that have flammable components, appear to be scarce in the literature. In the present study, the flash points of tert-pentanol+n-decane system were measured by Tag open-cup tester. The measured data were compared with the values calculated by the Raoult's law and the optimization methods based on the Wilson and NRTL equations. The calculated values by optimization methods were found to be better than those based on the Raoult's law.

Isothermal vapor–liquid equilibria and excess Gibbs free energies in some binary nitroalkane + chloroalkane mixtures at temperatures from 298.15 K to 318.15 K

The vapor pressures of binary mixtures of cloroalkane (1-chlorobutane, 1-chloropentane)+nitromethane or nitroethane were measured at temperatures between 298.15K and 318.15K. The vapor pressures vs. liquid phase composition data have been used to calculate the activity coefficients of the two components, and the excess molar Gibbs energies GE for the mixtures, using Barker's method. Redlich–Kister, Wilson, NRTL and UNIQUAC equations, taking into account the vapor phase imperfection in terms of the 2-nd virial coefficient, have represented the GE values. No significant difference between GE values obtained with these equations has been observed. The results indicate that all the systems show positive deviations from Raoult's law. The experimental VLE data were analyzed in terms of the modified UNIFAC (Dortmund) model.

Calculation of vapour - liquid - liquid – equilibria in quaternary systems

Abstract A method of parameters fitting to the experimental vapour - liquid - liquid equilibrium (VLLE) data is presented for the NRTL and the Uniquac equations for six quaternary mixtures. The same equations but with coefficients taken from the simulator Chemcad database were also used for calculation of the VLLE for the same mixtures. The calculated equilibrium temperatures and compositions for all the three phases were compared with the experimental data for these four cases. The investigated models were also applied for calculation of the compositions and temperatures of ternary azeotropes occurring in the considered quaternary mixtures. The computed values were compared with the experimental ones to appreciate the model's accuracy and to confirm whether the model correctly predicts the presence of homo- or heteroazeotrope. The NRTL equation with coefficients fitted to the VLLE data proved to be the most accurate model. For the mixtures containing water, ethanol and two different hydrocarbons this model shows particularly high accuracy. In three cases the mean deviations between the calculated and measured temperatures do not exceed 0.25 K, and for the fourth mixture the difference equals 0.33. Besides, the mean deviations between the calculated and the measured concentrations in the gas and liquid phases, with one exception do not exceed 1 mole %.

Solid–liquid phase equilibria for binary mixtures of propellant’s stabilizers

Solid–liquid equilibria for three binary mixtures of N-(2-acetoxyethyl)-p-nitroaniline (1) + 2-nitrodiphenylamine (2), N-(2-acetoxyethyl)-p-nitroaniline (1) + ethyl centralite (2) and N-(2-acetoxyethyl)-p-nitroaniline (1) + methyl centralite (2) have been determined experimentally using differential scanning calorimeter (DSC). Simple eutectic behaviours for these systems have been observed. The experimental results have been correlated by means of NRTL and UNIQUAC equations. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.61 to 3.32 K and depend on the particular model used. The best solubility correlation has been obtained with the UNIQUAC model.

Vapour–liquid equilibrium measurements and modelling for the ternary system (water + 2-propanol + 1-butyl-3-methylimidazolium acetate)

Vapour–liquid equilibrium (VLE) data were measured for the ternary mixtures of water (1) + 2-propanol (2) + 1-butyl-3-methylimidazolium acetate ([bmim][OAc]) (3). Complete T, x and y data were obtained in a relatively wide range of ionic liquid (IL) mass fractions up to 0.8. The data were correlated by means of NRTL and eNRTL equations with satisfactory results. Using the eNRTL equation, the ternary VLE behaviour was also modelled through correlation of two data sets, in which the mole fraction of 2-propanol on IL-free basis is respectively at 0.1 and 0.98. In this way, the six data sets were reproduced satisfactorily, with root mean square deviations of 1.06 K for temperature and 0.0098 for vapour-phase mole fractions. Owing to the regular distribution of the experimental data, good agreement between experiment and calculation was graphically presented. Effect of the IL on the VLE behaviour of the volatile components was also illustrated.

Boiling temperatures and excess thermodynamic functions of 2-propanol-n-alkyl propanoate solutions

Boiling temperatures of five binary systems are measured by ebuliometer in the pressure range of 5.333–101.3 kPa. The compositions of equilibrium vapor phases in the systems are calculated using the constructed saturated vapor pressure isotherms as a base. The excess Gibbs energies, excess enthalpies, and excess entropies of solutions are calculated from our data on liquid-vapor equilibria. Regularities in the changes of phase equilibria and thermodynamic properties of solutions with the composition and temperature of the system are established. Vapor-liquid equilibria in the systems are described by the Wilson and NRTL equations.

Phase equilibrium in acetone-water-mesityl oxide-diacetone alcohol four-component system

The liquid-vapor equilibrium is measured for acetone-mesityl oxide, acetone-diacetone alcohol, and mesityl oxide-diacetone alcohol binary systems and for three ternary systems. Activity coefficients for these systems are found. The binary interaction parameters of the NRTL equation for the components of a given reaction mixture are calculated from experimental data using the PRO/II SimSci software package. The vapor-liquid equilibrium is modeled and an analysis of the phase diagram is presented.

Phase Equilibria Study of the Binary Systems (N-Hexylisoquinolinium Thiocyanate Ionic Liquid + Organic Solvent or Water)

Liquid-liquid phase equilibria (LLE) of binary mixtures containing a room-temperature ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] with an aliphatic hydrocarbon (n-hexane, n-heptane), aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), cyclohexane, thiophene, water, and 1-alcohol (1-ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol) have been determined using a dynamic method from room temperature to the boiling-point of the solvent at ambient pressure. N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] has been synthesized from N-hexyl-isoquinolinium bromide as a substrate. Specific basic characterization of the new compound including NMR spectra, elementary analysis, and water content have been done. The density and viscosity of pure ionic liquid were determined over a wide temperature range from 298.15 to 348.15 K. The mutual immiscibility with an upper critical solution temperature (UCST) for the binary systems {IL + aliphatic hydrocarbon, cyclohexane, or water} was detected. In the systems of {IL + aromatic hydrocarbon or thiophene} an immiscibility gap with a lower critical solution temperature (LCST) was observed. Complete miscibility in the liquid phase, over a whole range of ionic liquid mole fraction, was observed for the binary mixtures containing IL and an 1-alcohol. For the tested binary systems with immiscibility gap {IL + aliphatic hydrocarbon, aromatic hydrocarbon, cyclohexane, thiophene, or water}, the parameters of the LLE correlation have been derived using the NRTL equation. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) experiments.

Progress in selecting desiccant and dehumidifier for liquid desiccant cooling system

Liquid desiccant cooling system (LDCS) is an alternative air-conditioning system with good energy-saving potential. Dehumidification performance is the key part of LDCS; while desiccant variety and dehumidifier influence the dehumidification performance. However, few works have been done about how to select cost-effective liquid desiccant and good performance dehumidifier. To improve, we proposed a new method for selecting a cost-effective mixed desiccant group: it combines the non-random two-liquid equation (NRTL equation) with the desiccant cost to get the mathematical form of the cost-effectiveness. Meanwhile, through the comparison experiments among different dehumidifiers, we have found out some helpful tips for dehumidifier design: it achieves better effect with rougher surface and adsorption absorption complex plan. These progresses increase the dehumidification performance by more than 50% and could make LDCS more competitive in the future market.

Thermodynamic characterization of second generation biofuels: Vapour–liquid equilibria and excess enthalpies of the binary mixtures 1-pentanol and cyclohexane or toluene

The paper reports accurate experimental data of vapour–liquid equilibria at T=313.15K, using an isothermal total pressure cell, for the binary systems (1-pentanol+cyclohexane) and (1-pentanol+toluene). The data were correlated using Margules, Wilson, NRTL and UNIQUAC equations. Also, the enthalpies of mixing were measured for the same systems at two different temperatures T=(298.15 and 313.15)K using an isothermal flow calorimeter and the excess enthalpies were correlated by the Redlich–Kister equation. The thermodynamic behaviour of both systems is discussed.

Phase equilibrium properties of the ternary mixture dibutyl ether + toluene + heptane at 313.15 K

New accurate vapour liquid equilibrium data for the ternary mixture formed by dibutyl ether (DBE), toluene and heptane at 313.15K have been measured. A static method using an isothermal total pressure cell (Van Ness’ technique) has been employed. The system studied presented a slight deviation from ideal behaviour. Reduction of the experimental data has been done by Barker's method using Wohl expansion, NRTL, Wilson and UNIQUAC equations. Moreover, experimental results have been compared to predictions for the ternary system obtained from the Wilson, NRTL, UNIQUAC and UNIFAC (Dortmund) models.

Liquid–liquid equilibria and thermo physical properties for 1-methyl-2-pyrrolidinone + heterocyclic nitrogen compounds + hexadecane systems at 298.15 K

Liquid–liquid equilibrium data for {1-methyl-2-pyrrolidinone (NMP)+heterocyclic nitrogen compounds+hexadecane} systems were analytically determined at 298.15K and atmospheric pressure using stirred and thermo-regulated cell. The experimental data were modeled with the NRTL and UNIQUAC equations. Besides, the Bachman–Brown correlation was used to ascertain the reliability of the experimental data. Additionally, excess molar volumes (VE) and deviations in the molar refractivity (ΔR) data at 298.15K were determined for the {NMP+heterocyclic nitrogen compounds} binary systems using a digital vibrating-tube densimeter and a precision digital refractometer. The VE and ΔR data were modeled with the Redlich–Kister equation.

Thermodynamic properties of the N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide

This work is a continuation of our wide ranging investigation on quinolinium based ionic liquids (ILs). The study includes specific basic characterisation of the synthesized compounds N-octylquinolinium bromide, [OQuin][Br] and N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide [OQuin][NTf2] by NMR spectra, elementary analysis and water content. Differential scanning calorimetry (DSC) measurements gave us properties of the pure [OQuin][NTf2] i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity at the glass transition. Densities and viscosities were determined as a function of temperature. The temperature-composition phase diagrams of 10 binary mixtures composed of organic solvent dissolved in the IL: {[OQuin][NTf2]+aromatic hydrocarbon (benzene, or thiophene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol, or 1-dodecanol)} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (250 to 370)K. For mixtures with benzene and alkylbenzenes, the immiscibility gap in the liquid phase in a low mole fraction of the IL was observed with upper critical solution temperature (UCST) higher than the boiling point of the solvent. In the system with thiophene, the immiscibility gap is lower and UCST was measured. For binary mixtures with alcohols, complete miscibility in the liquid phase was observed for 1-butanol and 1-hexanol. In the systems with longer chain alcohols, the immiscibility gap with UCST was noted. Typical behaviour for ILs was observed with an increase of the chain length of an alcohol the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid+liquid), SLE and (liquid+liquid), LLE phase equilibrium data sets.

Separation of Benzene from Heptane Using Tree Ionic Liquids: BMimMSO4, BMimNTf2, and PMimNTf2

To study the influence of the structure of the different ionic liquids on the separation of the binary mixtures of hydrocarbon + aromatic compounds, we have carried out the liquid-liquid equilibrium (LLE) of the ternary systems: heptane + benzene + 1-butyl-3-methylimidazolium methylsulfate, BMimMSO4, 1-butyl-3-methylimidazolium bistrifluoromethylsulfonylimide, BMimNTF2 and 1-methyl-3-propylimidazolium bistrifluoromethylsulfonylimide, PMimNTF2, were measured at T = 298.15 K and atmospheric pressure. Selectivity and solute distribution ratio, derived from the equilibrium data, were used to determine if these ionic liquid can be used as a potential extracting solvent for the separation of aromatic compounds from heptane. The experimental data for the ternary systems were well correlated with NRTL and UNIQUAC equations. The results were used to analyse the influence of structure of the ionic liquid.