Isothermal Vapor Liquid Equilibrium Research Articles

Investigation of Thermodynamic Consistency Test of Carbon Dioxide (CO2) in Room-Temperature Ionic liquids using Generic van der Waals Equation of State

Thermodynamic consistency test of isothermal vapor-liquid equilibrium (VLE) data of various binary systems containing Carbon dioxide (CO2)/Room temperature ionic liquids (RTILs) have been investigated in wide ranges of pressures in each isotherm precisely. In this paper Generic van der Waals (GvdW) equation of state (EoS) coupled with modified van der Waals Berthelot mixing rule has successfully been applied for correlating P-T-x binary data. The optimum parameters were obtained by minimizing the average relative deviation between modeled and experimental data based on the bubble pressure algorithm. Modeling is highly shown satisfactory in all cases which means that deviations in correlated data are low subsequently can prove that the flexibility and capability of the proposed model for thermodynamic consistency. Results of the consistency test represented ten isothermal experimental data set to be thermodynamically consistent, fourteen were declared to be not fully consistent and just four isothermal experimental data sets were represented to be thermodynamically inconsistent.

Volumetric, enthalpic and VLE studies of binary mixtures of isomers of butyl chloride with cyclohexane at 298.15 K

Excess molar volumes (VmE), excess molar enthalpy (HmE) and isothermal vapor-liquid equilibrium data for n-, sec- and tert-butyl chloride (A) + cyclohexane (B) systems were measured at 298.15 K. Excess molar Gibbs free energy (GmE) for these systems were calculated by Barker's method. The VmE and HmE for these mixtures follow the sequence: n- > sec- > tert-butyl chloride while it is reverse for GmE. Prigogine-Flory-Patterson theory (PFP) predicts the experimental VmE and HmE data for these systems quite well except for HmE of n-butyl chloride (xA>0.5) mixtures and tert-butyl chloride mixtures for xA<0.5. The activity coefficients γA and γB of the components in binary (A+B) mixtures were also predicted by Singh and Maken activity coefficient model employing limited experimental activity coefficient data.

P-x isothermal equilibrium data for two ternary systems containing long-chain bioalcohols: (1-butanol or 2-butanol + cyclohexane + methylbenzene) at 313.15 K

Butanols can be incorporated as biofuels in gasoline. As a consequence, the thermodynamic behaviour in the blend of the different type of accompanying hydrocarbons (paraffins, cycloparaffins, olefins, aromatics) should be explored. Being a multicomponent mixture the best testing ground for checking prediction is the generation of the ternary systems made up of combinations of representatives of the indicated hydrocarbons two by two with alcohols. This paper reports the isothermal vapour–liquid equilibrium (VLE) at 313.15 K of the two remaining ternaries of an overall comprehensive study involving 1- or 2- butanol. A recognized accurate static technique consisting of an isothermal total pressure cell has been used for the measurements (Van Ness apparatus). Data were reduced using Barker’s method together with Wilson equation, as excess Gibbs energy model, enabling the determination of all phase equilibrium properties. Starting from our new data we complete the study by discussing the ternary prediction from four model equations by Wohl, Wilson, NRTL and UNIQUAC commonly used. Parameters fed by their constituent binaries reported in previous papers conclude that Wilson model provides the best result in both of our ternary systems.

Separation of benzene from methylcycloalkanes by extractive distillation with cyano-based ionic liquids: Experimental and CPA EoS modelling

The aromatic/aliphatic separation using ionic liquids (ILs) has been proposed as an enhanced technology when compared to conventional liquid-liquid extraction and extractive distillation processes. Some ILs show extractive properties (distribution ratios and selectivities) greater than those of conventional solvents, like sulfolane and N-methylpyrrolidone, positioning these solvents to address challenging separations. Methylcycloalkanes and benzene are close-boiling mixtures in the petrochemical industry, presented at the hydrogenated pyrolysis naphtha where benzene is at a high concentration (ca. 70 wt%). Aiming to tackle this separation, cyano-based ILs were tested as mass agents in the benzene separation from methylcycloalkanes. A complete phase equilibria characterization with the most promising ILs, [C2C1im][DCA] and [C2C1im][SCN], were done, using a recently developed experimental-modelling strategy. Isothermal vapour-liquid equilibria for binary, ternary and quaternary systems was measured by Headspace Gas-Chromatography (HS-GC) and modelled using the Cubic Plus Association (CPA) Equation of State (EoS). The presence of the ILs improved the methylcycloalkane/benzene relative volatilities by one order of magnitude, whereas homogeneous and heterogeneous regions were determined by HS-GC, leading to a consistent model.

Vapour-liquid equilibria of n-butane and ethyl mercaptan: Experiments and modelling

Design of debutaniser in fractionation train in gas processing requires accurate knowledge of phase equilibrium properties of n-butane with sulphur compounds like mercaptan. In this paper, we report high-quality isothermal vapour–liquid equilibrium data for n-butane + ethyl mercaptan (or ethanethiol) between 298.14 K and 388.18 K and pressures up to 2.0029 MPa. An equipment whose experimental technique is based on static-analytic method was considered. The equipment is composed by an agitated equilibrium cell with two online micro samplers connected to a Gas Chromatograph. The data was correlated with the Peng Robinson equation of state with classical alpha function. A comparison was also performed with two predictive models, PPR78 and PSRK UNIFAC.

Isothermal vapor-liquid equilibrium of binary and ternary systems of anisole, hexane, and toluene and ternary system of methyl tert-butyl ether, hexane, and toluene

Following the importance of equilibrium data of biomass components as well as octane boosters, the isothermal vapor-liquid behaviors of binary and ternary systems including hexane, toluene, and anisole, and ternary system of methyl tert-butyl ether, hexane, and toluene were investigated at 313.2 K. To do so, the Othmer still was employed to collect the experimental data. Furthermore, thermodynamic calculations were implemented by the Peng-Robinson equation of state and UNIQUAC and NRTL activity coefficient models. The whole binary systems passed the isothermal thermodynamic consistency test of Herington. Based on the obtained results, no azeotrope was observed. Moreover, the obtained errors of calculation imply that UNIQUAC equation is suitable for the representation of the vapor and liquid phases compositions.

Excess properties and isothermal vapour-liquid equilibrium data for the ((toluene + pyridine)) system from 343 K to 383 K

Isothermal vapour-liquid equilibrium (VLE) data for the ((toluene + pyridine)) system has been measured at four temperatures from approximately 343 K to 383 K, using a dynamic-analytic apparatus. The densities of ((toluene + pyridine)) mixtures were also measured from 298 K to 363 K using an Anton Paar DMA-5000 densitometer. The vapour-liquid phase equilibrium data were modelled by the γ-Φ approach and the Non-Random Two-Liquid and UNIQUAC activity coefficient models. The consistency of the experimental isothermal VLE data were checked by the area and point tests. The experimental density data were modelled using an 8-parameter empirical correlation which allowed for the simultaneous representation of temperature and liquid composition. The experimental data were used to determine the excess properties for volume, Gibbs energy, enthalpy and entropy. The excess volume was modelled using Redlich-Kister polynomials.

Study on Particle Swarm Optimization Variant and Simulated Annealing in Vapor Liquid Equilibrium Calculation

Phase equilibrium calculation plays a major rule in optimization of separation process in chemical processing. Phase equilibrium calculation is still very challenging due to highly nonlinear and non-convex of mathematical models. Recently, stochastic optimization method has been widely used to solve those problems. One of the promising stochastic methods is Particle Swarm Optimization (PSO) due to its simplicity and robustness. This study presents the capability of particle swarm optimization for correlating isothermal vapor liquid equilibrium data of water with methanol and ethanol system by optimizing Wilson, Non-Random Two Liquids (NRTL), and Universal Quasi Chemical (UNIQUAC) activity coefficient model and also presents the comparison with bare-bones PSO (BBPSO) and simulated annealing (SA). Those three optimization methods were successfully tested and validated to model vapor liquid equilibrium calculation and were successfully applied to correlate vapor liquid equilibrium data for those types of systems with deviation less than 2%. In addition, BBPSO shows a consistency result and faster convergence among those three optimization methods. Keywords: Phase equilibrium, stochastic method, particle swarm optimization, simulated annealing and activity coefficient model

Experimental measurements and modelling of vapour-liquid equilibrium of 2,3,3,3-tetrafluoropropene (R-1234yf) + 1,1,1,2,2-pentafluoropropane (R-245cb) system

Isothermal vapour-liquid equilibrium (VLE) of the R-1234yf+R-245cb binary system were measured using a “static-analytic” apparatus at temperatures from 283.39 to 343.27 K. The data measured were compared with literature data for conformity checking. Albeit both VLE measurement sets are in good accordance, an unexpected behaviour was observed for the relative volatility calculated on the basis of the literature data.The thermodynamic model used for the calculations reproduces very well R-1234yf+R-245cb VLE data, and is based on a 3-parameter cubic equation of state (denoted by NEoS). This cubic equation of state was associated with the Mathias–Copeman alpha function and van der Waals mixing rules. Comparisons were also done with Peng–Robinson EoS with similar alpha function and mixing rules.

Experimental measurements of saturated vapor pressure and isothermal vapor-liquid equilibria for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system

This work investigated saturated vapor pressure and isothermal vapor-liquid equilibrium (VLE) for 1,1,1,2-Tetrafluoroethane (HFC-134a) + 3,3,3-trifluoropropene (HFO-1243zf) binary system. The saturated vapor pressures of HFC-134a and HFO-1243zf ranging from (273.17–353.13) K, and VLE data at four temperatures (283.15, 293.15, 313.15, 323.14) K for the HFC-134a + HFO-1243zf system were measured by a static-analytical apparatus. The vapor pressure data of HFO-1243zf were regressed by a Wagner type equation and compared with existing literature data. The experimental VLE data of HFC-134a + HFO-1243zf system were correlated by Peng-Robinson (PR) equation of state (EOS) combined with van der Waals (vdW) mixing rules. The binary interaction parameters were obtained, and correlation deviation was acceptable. Azeotropic behavior can be found for the HFC-134a + HFO-1243zf system at measured temperatures. Our work provides fundamental thermodynamic properties of new mixed refrigerants which are crucial to evaluate their cycle performance and optimize the design of refrigeration system.

Isothermal Vapor–Liquid Equilibrium of the Absorption Working Pairs (HFC-32 + DMETrEG, HFC-32 + NMP) at Temperatures from 293.15 to 343.15 K

The working pairs of HFCs + organic absorption solvents are commonly used in absorption systems. In this work, the vapor–liquid equilibrium (VLE) data of HFC-32 + DMETrEG at (293.15–343.15) K and HFC-32 + NMP at (323.15–343.15) K were measured in a dual cycle apparatus. The VLE data were correlated by Antione-type equation, NRTL, and PR + MHV1 + NRTL model, respectively. The predicted VLE data showed a good agreement with the experimental VLE data. NRTL model was recommended to predict the VLE data and characteristic of solution for HFC-32 + DMETrEG and HFC-32 + NMP, compared to PR + MHV1 + NRTL model. The comparison of VLE characteristics for five binary mixtures (HFC-32 + DMETrEG, HFC-32 + NMP, HFC-32 + DMF, HFC-32 + DMAC, and HFC-32 + DMEDEG) was carried out. The compared results showed that the system pressures of HFC-32 + DMETrEG and HFC-32 + NMP were lower than other three mixtures, and the negative deviations from Raoult’s law of HFC-32 + DMETrEG and HFC-32 + NMP were larger than the others, which ...

(Vapor + liquid) phase equilibria of an aqueous solution of bromide-based ionic liquids – measurements, correlations and application to absorption cycles

In this work, thermodynamic and physicochemical properties including (vapor + liquid) equilibria (VLE), density and dynamic viscosity of binary mixtures composed of bromide-based ionic liquid (IL) and water were measured as a function of IL mole fraction in a wide range of temperature. The aqueous solution of the following ILs: 1-ethyl-1-methylpiperidinium bromide, ethylpyridinium bromide, 1-(2-hydroxyethyl)pyridinium bromide, 1-ethyl-1-methyl-morpholinium bromide, 1-hydroxyethyl-1-methylmorpholinium bromide, and N-ethyl-N,N-dimethyl-N-hydroxyethylammonium bromide have been tested for potential applications as working fluids in absorption refrigeration technology. The isothermal VLE has been measured by an ebulliometric method within a temperature range from T = (338.15–368.15) K and pressure up to 85 kPa and correlated using Redlich-Kwong equation of state. This work is a continuation of our systematic investigation of an aqueous solution of ionic liquids as a potential working fluid in absorption refrigeration technology. The summary of this research is the modeling of the theoretical cycles using working fluids proposed in this paper. The calculated values of the coefficient of performance (COP) were compared to other ILs from available literature and {LiBr + water} system, conventionally used on the industrial scale in absorption refrigeration technology.

Isothermal Vapor–Liquid Equilibrium Measurements for Alcohol + Water/n-Hexane Azeotropic Systems Using Both Dynamic and Automated Static-Synthetic Methods

Isothermal vapor–liquid equilibrium measurements (pressure– temperature–liquid and vapor composition) were conducted for water (1) + propan-1-ol (2), n-hexane (1) + butan-2-ol (2), and n-hexane (1) + 2-methyl-propan-1-ol (2) at three temperatures, each using a dynamic moderate pressure equilibrium still. Additionally, pressure–temperature-overall composition measurements for the first two systems were conducted for the intermediate temperatures using a newly automated static-synthetic apparatus to confirm the operability of the automation scheme and to compare the model predictions of the vapor-phase compositions from the processed pressure–temperature–liquid composition data by the static-synthetic method with the experimental vapor compositions measured by the dynamic method. The automation scheme was developed and implemented on the original static total pressure vapor–liquid equilibrium apparatus of Raal et al. (Fluid Phase Equilib. 2011, 310, 156–165) using the LabVIEW graphical programming language. In comparison to the manual operating mode, this scheme improved the efficiency of operation by reducing the man-hours involved and minimized the associated uncertainty with the measurement procedure with respect to liquid composition. Once executed, the control scheme requires approximately 2 days to produce a single 40-data point (pressure–temperature–liquid composition) isotherm and minimizes human intervention to 2–3 h in comparison to a 2-week long measurement procedure in the nonautomated operating mode and in excess of 3 weeks using the dynamic method with analysis by gas chromatography. All experimental data were modeled using the γ–Φ approach with the NRTL and UNIQUAC activity coefficient models and the virial equation of state with the Hayden and O’Connell correlation. For the pressure–temperature–liquid and vapor composition data measured, thermodynamic consistency testing was performed. The data sets passed the point test with 0.01 tolerance and the area test with 10% tolerance. Experimental vapor-phase compositions obtained by phase sampling in the dynamic method compared reasonably well with the predictions from the pressure–temperature–liquid composition data measured by the automated static-synthetic method.

Experimental measurements and correlation of isothermal vapor-liquid equilibria for HFC-32 + HFO-1234ze (E) and HFC-134a + HFO-1234ze (E) binary systems

Currently, refrigeration industry is facing the challenge of developing new highly efficient alternative refrigerants with zero ozone depression potential (ODP) and global warming potential (GWP) lower than 150. Mixtures, composed of hydrofluoro-olefins (HFOs) with either hydrofluorocarbons (HFCs) or natural refrigerants, are of great interest, because they could meet both thermodynamic and environmental requirements. This work investigated the phase behavior of two low GWP binary refrigerants containing trans-1,3,3,3-tetrafluoropropene (HFO-1234ze (E)) and two HFCs. Isothermal vapor-liquid equilibrium (VLE) data for two binary mixtures of difluoroethane (HFC-32) + HFO-1234ze (E) and 1,1,1,2-Tetrafluoroethane (HFC-134a) + HFO-1234ze (E) were measured by a static-analysis apparatus at four temperatures ranging from (283.15 to 323.14) K. The VLE data of HFC-32 + HFO-1234ze (E) system was compared with literature, and good consistence was obtained. The experimental VLE data were correlated by Peng-Robinson (PR) equation of state (EOS) combined with van der Waals (vdW) mixing rules. The binary interaction parameters of two mixtures were obtained, and correlation deviation was acceptable. Our work provides fundamental thermodynamics properties of new mixed refrigerants which are crucial to evaluate their cycle performance and optimize the design of refrigeration system.

Volumetric Behavior and Vapor–Liquid Equilibrium of Dimethyl Disulfide + n-Alkanol Binary Mixtures

In this paper, we report densities at 303.15 and 323.15 K and at atmospheric pressure (p = 0.1 MPa) of the binary mixtures containing dimethyl disulfide and a linear alkanol (methanol, ethanol, 1-propanol or 1-butanol). The isothermal vapor–liquid equilibrium for these systems was also determined at the same temperatures while the pressure range for vapor–liquid equilibrium measurement depends on both the mixture and temperature considered. The vapor–liquid equilibrium data were found to be thermodynamically consistent. From these data experimental excess volumes and excess Gibbs functions were obtained and correlated with composition using the Redlich–Kister polynomial expansion and the Wilson equation, respectively. The values of both excess properties were positive. The excess volumes, unlike the excess Gibbs functions, increase with the length of the n-alkanol chain.

VLE measurements and modelling for the binary systems of (CF4 + C6F14) and (CF4+ C8F18)

Isothermal phase equilibrium data were measured for the binary systems of tetrafluoromethane with either perfluorohexane or perfluorooctane to investigate the effect of carbon chain length of the solvent with regards to the solubility of tetrafluoromethane. Both the “static-analytic” and the “static-synthetic” methods were utilized to measure the high-pressure phase equilibrium data. Isothermal measurements were performed within the temperature range of (283.15–303.15) K and at pressures up to 11 MPa. Vapour pressure data for perfluorohexane and perfluorooctane were measured within the temperature range of (283.15–323.15) K. Additionally, isothermal vapour-liquid equilibrium data were measured for the binary system of carbon dioxide + n-hexane at 313.15 K; the data were utilized to validate the experimental method. The experimental data were modeled using the Peng-Robinson equation of state with the Wong-Sandler mixing rule and Non-Random Two-Liquid excess Gibbs energy model. The model provides a satisfactory representation of the experimental data within the measured temperature range.

Vapor–liquid equilibrium and molecular simulation data for carbon dioxide (CO2) + trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze(E)) mixture at temperatures from 283.32 to 353.02 K and pressures up to 7.6 MPa

Isothermal Vapor–Liquid Equilibrium (VLE) data for the binary mixture of CO2 + R-1234ze(E)(trans-1,3,3,3-tetrafluoroprop-1-ene) were measured using a static-analytic method apparatus at seven temperatures between 283.32 and 353.02 K and pressures up to 7.6 MPa. For temperatures over the critical temperature of pure CO2, the critical compositions and pressures of binary mixtures were approximated applying power laws with asymptotic behavior at critical point. The data were well correlated using the Peng–Robinson equation of state incorporating the generalized alpha function, with the Wong–Sandler mixing rules involving NRTL activity coefficient model. The experimental and correlated phase compositions were compared with Gibbs Ensemble Monte Carlo simulation data obtained at 293.15 K and 353.02 K. Though the molecular simulation predictions at low temperature (293.15 K) properly match experimental data, a slight shift appeared at high temperature (353.02 K), and the expected convergence of phase compositions near critical point was not fully observed.

Vapor–Liquid Equilibrium Data for the Carbon Dioxide (CO2) + 1,1,1,3,3-Pentafluorobutane (R365mfc) System at Temperatures from 283.15 to 337.15 K

Isothermal vapor–liquid equilibrium data for the binary mixture of carbon dioxide (CO2) and 1,1,1,3,3-pentafluorobutane (R365mfc) were measured at six isotherms ranging from 283.16 to 337.16 K, at pressures ranging from 0.7 to 9.1 MPa, and are presented. The measurements were performed using a “static-analytic” apparatus, equipped with two capillary ROLSI samplers, with phase analysis performed via gas chromatography. The measured data were correlated using in-house thermodynamic software based on the Peng–Robinson equation of state with the Mathias–Copeman α function and the Wong–Sandler mixing rules incorporating the nonrandom two liquids model.

Measurements of isothermal vapor-liquid equilibrium for 2,3,3,3-tetrafluoroprop-1-ene + 1,1,1,2-tetrafluoroethane + propane system at temperatures from 283.15 to 323.15 K

Isothermal vapor liquid equilibrium (VLE) data of the alternative 2,3,3,3-tetrafluoroprop-1-ene + 1,1,1,2-tetrafluoroethane + propane ternary mixture over the temperature range of 283.15–323.15 K at 10 K intervals were measured using a circulation type apparatus. The experimental VLE data were correlated by Wilson-RK model, NRTL-RK model and PR-WS-MUNIFAC model. All of the models can well present the experimental data. The average absolute relative deviation (AARD) of pressure are within 0.60% and the maximum average absolute deviation (AAD) of vapor mass fraction is 0.0154 for the PR-WS-MUNIFAC model. Based on the UNIFAC (Dortmund) method, the two new functional groups of C2H2F and CH2F were divided and the relevant group parameters were obtained by fitting the experimental data.

Isothermal Vapor–Liquid Equilibrium Measurements of Butan-2-one + 2-Methyl-propan-1-ol/Pentan-1-ol

Isothermal vapor–liquid equilibrium (VLE) data were measured for the systems of butan-2-one (1) + 2-methyl-propan-1-ol (2)/pentan-1-ol (2) using a dynamic low-pressure apparatus. Measurements were undertaken at approximately 333, 343, and 348 K. The VLE data were correlated by minimizing the pressure residual using the combined method with the Wilson and UNIQUAC activity coefficient models being employed for the liquid phase nonideality, using the virial equation of state with the Hayden and O’Connell correlation for the vapor phase nonideality. The Wilson model provided a marginally superior fit of the VLE data to the UNIQUAC model. The thermodynamic consistency of the data was tested, and it was found that all data sets were thermodynamically consistent according to the area and point tests. Excess enthalpies were calculated from the modeled VLE data and were extrapolated to conditions of experimental data from the literature. A good correlation was found between the experimental literature and calculat...