Binary System Methane Research Articles

Density and phase equilibrium of the binary system methane + n-decane under high temperatures and pressures

Densities of the binary system methane + n-decane have been determined through a vibrating tube densitometer from (278.15–463.15) K at pressures up to 140 MPa, and for methane mole fractions up to 0.8496. Negative excess volumes were found under the experimental conditions studied. Moreover isothermal compressibility values were obtained by differentiation from the Tammann-Tait correlation of the determined density values. Isobaric thermal expansion coefficients were also calculated based on differentiation from the isobaric fit of density data. We also measured the phase equilibrium of this binary system by using a variable volume cell with full visibility from (293.15–472.47) K for three mixtures with methane mole fractions of 0.4031, 0.6021 and 0.8496. Liquid fraction upon expansion below the saturation pressure has also been determined. Finally different equations of state were used to calculate the experimental density and excess volume data as well as the phase envelope data. No direct regression of the experimental data was involved in most of the calculation in order to provide a fair comparison of the performance of different models.

High pressure vapor-liquid equilibria for binary methane and protic ionic liquid based on propionate anions

Sour gases and methane separation has been studied for many years and ionic liquids (ILs) could be used to promote their separation. Protic ionic liquids based on substitute amines and carboxilate anions were reported to be selective to methane/carbon dioxide separation. However, the methane + ILs phase equilibria data, which is required to design gas separation, are scarce on the open literature. This study report the high pressure phase transition data for methane + N-methyl-2-hydroxyethylammonium propanoate, bis(2-hydroxyethyl)ammonium propanoate, or 2-hydroxyethylammonium propanoate. The binary system methane + N-methyl-2-hydroxyethylammonium propanoate was compared to literature experimental data. The structures and purities of ILs were confirmed by 1H NMR, 13C NMR, HSQC and HMBC NMR studies. Water content were measured by Karl Fischer coulometer measurements. The phase transitions have been classified as bubble points and studied at four temperatures from 333.1 to 363.1 K and pressures from 4 to 16 MPa. The experimental data were obtained using the static-synthetic visual method by a variable-volume cell unit. VLE transitions have been classified as bubble points. Henry's law constants were estimated and compared with other ILs and organic solvents. Experimental data for CH4 + + N-methyl-2-hydroxyethylammonium propanoate system were correlated using the three-parametric Redlich – Kwong – Peng – Robinson equation of state (RKPR-EoS) coupled to cubic van der Waals mixing rules (regarding the composition) and temperature dependence for the interaction energy parameter (CMR-T).

Reference Quality Vapor–Liquid Equilibrium Data for the Binary Systems Methane + Ethane, + Propane, + Butane, and + 2-Methylpropane, at Temperatures from (203 to 273) K and Pressures to 9 MPa

A specialized cell designed for vapor liquid equilibrium (VLE) measurements at cryogenic temperatures and high pressures was used to measure new (p,T,x,y) data for binary mixtures of methane + ethane, + propane, + 2-methylpropane (isobutane), and + butane from (203 to 273) K at pressures up to 9 MPa. A literature review of VLE data for these binary mixtures indicates that a significant number have large uncertainties; however, because estimates of uncertainties in measured phase compositions are often not quantified sufficiently, it can be difficult for equation of state (EOS) developers to identify which data sets are of poor quality. Robust quantitative uncertainties were estimated for the VLE data acquired in this work, which allowed the identification of literature data sets that should not be included in future EOS development. The new data were compared with the predictions of the Peng–Robinson (PR) EOS and the Groupe European de Recherche Gaziere (GERG-2008) multiparameter EOS. The former describes the new data measured at low pressures within experimental uncertainty but deviates systematically from the data as the bubble point pressure is increased; for the binary mixtures containing either of the butanes, the maximum relative deviation of the data from the PR EOS amounted to nearly 10 % of the methane liquid mole fraction. The GERG-2008 EOS was better able to describe the new high-pressure data for the CH4 + C3H8 system than the PR EOS. However, for both the CH4 + C4H10 mixtures, the GERG EOS deviated from these data by an amount twice as large as the PR EOS because of ambiguity about which VLE literature data sets should be used in model development. The new data resolve these ambiguities and should facilitate the development of improved EOS as needed, for example, in simulations of low temperature natural gas separation processes.

High pressure phase behavior modeling of asymmetric alkane + alkane binary systems with the RKPR EOS

Very asymmetric hydrocarbon mixtures present an interesting academic challenge for their modeling. In addition, they are becoming more important technologically, since the world oil reserves are becoming heavier in average.The RKPR EOS was developed in recent years in order to consider asymmetric systems and allow for a good representation of densities for different types of compounds while maintaining the relative simplicity of cubic equations of state. In this work the RKPR EOS is applied for the first time for the correlation of phase behavior in the series of binary systems methane+n-alkane and ethane+n-alkane. In addition to the use of attractive and repulsive interaction parameters with quadratic mixing rules, the role of the extra degree of freedom that the RKPR model offers for setting the pure compound parameters was also examined. A new table of RKPR pure compound parameters was defined for n-alkanes. A comparative study was made with the Peng–Robinson EOS, based on following the same optimization procedure for interaction parameters.

Modeling high-pressure phase equilibria of coalbed gases/water mixtures with the Peng–Robinson equation of state

Reservoir simulations for enhanced coalbed methane recovery and CO2 sequestration require an equation of state (EOS) model that can provide accurate predictions of vapor–liquid equilibria (VLE) of mixtures of coalbed gases (methane, nitrogen and carbon dioxide) with water at high-pressures and near-critical temperatures. An EOS should be capable of providing rapid and accurate estimates of phase equilibrium for gas+water mixtures under the conditions encountered in coalbed reservoir work. Although more complex equations of state may be used, the computational efficiency of cubic equations of state offers a distinct advantage for reservoir simulation purposes. Therefore, in this work, we utilized the Peng–Robinson equation of state (PR EOS) to model the high-pressure phase equilibria of coalbed gas+water mixtures, then developed expressions for the binary interaction parameters as functions of temperature for each of the important binary systems methane+water, nitrogen+water and carbon dioxide+water. For this purpose, an expanded database was assembled that contains vapor–liquid equilibrium measurements for the three binary mixtures. Several case studies were conducted to investigate both the correlative and predictive capabilities of the PR EOS. The PR EOS was found to be capable of describing the phase equilibria of these systems over the range of conditions encountered in coalbed reservoirs; however, the level of precision varies with the degree of complexity used in representing the interaction parameters in the mixing rules. Overall, an absolute average percentage deviation (%AAD) ranging from 0.3 to 1.7 was obtained for the liquid-phase compositions of the gas for the three binary systems when two system-specific interaction parameters were used. Expressions were developed to account for the temperature dependence of the binary interaction parameters. Using these expressions, the liquid-phase compositions for the three systems can be predicted within about 3–6%AAD, which is within three times the experimental errors in the measurements used in the analysis. The predictions for the vapor-phase composition of water, however, were less accurate (in terms of %AAD) due to the low values of the mole fraction of water in the vapor phase, where small errors in composition could lead to large percentage errors.

High pressure phase equilibria in methane + waxy systems. 3. Methane + a synthetic distribution of paraffin ranging from n-C 13 to n-C 22

Liquid–vapor and fluid–waxy solid phase transitions were measured under pressure on a pseudo binary system made up of methane + a waxy distribution of normal paraffins ranging from C 13 to C 22. The composition of the paraffins in the waxy fraction was defined in order to obtain an average molecular weight equal to that of pure heptadecane. Measurements were carried out up to 90 MPa by using a synthetic method on various mixtures ranging from 0 to 99% of methane. Results were compared to the phase equilibrium data of the binary system methane + heptadecane in the same conditions.

High pressure phase equilibria in methane + waxy systems. 2. Methane + waxy ternary mixture

Liquid–vapour and fluid–solid phase transitions were experimentally determined under pressure on the system methane + a ternary waxy mixture using a full visibility cell. The wax was an approximately equimolar mixture of n-C 16, n-C 17 and n-C 18, the composition being chosen to obtain a mixture with an average molecular weight similar to heptadecane. Measurements were performed according to the synthetic method on different mixtures ranging from 0 to 99.5 mol% of methane. The liquid–solid phase transitions were investigated up to 100 MPa and fluid phase boundary was studied in the temperature domain from 293 to 373 K. Measurements performed on this pseudo-binary system were compared to the phase diagram of the binary system methane + heptadecane.

Investigation of the surface tension of methane and n-alkane mixtures by perturbed-chain statistical associating fluid theory combined with density-gradient theory

The perturbed-chain statistical associating fluid theory (PC-SAFT) and density-gradient theory are used to construct an equation of state to describe the phase behavior of binary methane– n-alkane mixtures. With the molecular parameters and influence parameters regressed from bulk properties and surface tensions of pure fluids, respectively as input, both the bulk and interfacial properties are investigated. The surface tension of the binary systems methane–propane, methane–pentane, methane–heptane and methane–decane are predicted, and the results are satisfactory compared with the experimental data. Our results show that PC-SAFT combined with density-gradient theory is able to describe the interfacial properties of binary methane– n-alkane mixtures in wide temperature and pressure ranges, and illustrate the influence of the equilibrium bulk properties and chain length of n-alkane molecule on the interfacial properties.

Dynamic Viscosity Modeling of Methane + n-Decane and Methane + Toluene Mixtures : Comparative Study of Some Representative Models

Viscosity measurements of well-defined mixtures are useful in order to evaluate existing viscosity models. Recently, an extensive experimental study of the viscosity at pressures up to 140 MPa has been carried out for the binary systems methane + n-decane and methane + toluene, between 293.15 and 373.15 K and for several methane compositions. Although very far from real petroleum fluids, these mixtures are interesting in order to study the potential of extending various models to the simulation of complex fluids with asymmetrical components (light/heavy hydrocarbon). These data (575 data points) have been discussed in the framework of recent representative models (hard sphere scheme, friction theory, and free volume model) and with mixing laws and two empirical models (particularly the LBC model which is commonly used in petroleum engineering, and the self-referencing model). This comparative study shows that the average absolute deviation of the models is between 3.8 and 49.8%, and the maximum deviation is between 11.6 and 78.4%, depending on the considered model.

Further Validation of a Set of Quadrupolar Potential Models for Ethylene and Propylene from the Prediction of some Binary Mixture Vapor-Liquid Equilibria by Gibbs-ensemble Molecular Simulation

A set of two-center Lennard-Jones plus point quadrupole (2CLJQ) effective pair potential models for ethylene and propylene, that have already been shown to be capable of fitting the saturated densities, the vapor pressures, and the enthalpies of vaporization of the pure liquids, is tested for vapor-liquid equilibrium (VLE) of mixtures in this work. Monte Carlo simulations in the Gibbs ensemble were carried out in order to obtain VLE data for the binary systems methane+ethylene, ethylene+ethane, and ethane+propylene. No binary adjustable parameters were needed to compute the unlike-pair Lennard-Jones interactions in the binary systems. Simulation results were found to be in good agreement with the experimental data available for pressure and phase composition of the binary systems methane+ethylene at 150 and 190 K, ethylene+ethane at 233.15 and 255.37 K and ethane+propylene at 277.59 and 310.93 K.

On the phenomenon of double retrograde vaporization: multi-dew point behavior in the binary system ethane + limonene

Instead of the usual single-domed retrograde dew point curves, S-shaped dew point loci may occur in the isothermal pressure–composition diagram of the binary system methane+butane. This phenomenon has the consequence that at and immediately below the critical temperature of methane, isotherms are present showing triple-valued dew points for a fixed concentration. A similar behavior was observed in the binary system methane+pentane. However, in the latter system, in a narrow concentration range at temperatures slightly above the critical temperature of methane, isotherms were determined experimentally showing even two domes in the dew point loci, indicating quadruple-valued dew points at a given concentration. The latter behavior leads to the phenomenon of double retrograde vaporization, i.e. in a pressure–composition diagram at a fixed value of the concentration, the following sequence of phase transitions occur when going from low to high pressures: gas→liquid+gas→gas→liquid+gas→fluid. This paper presents bubble, dew and critical point data for the binary system ethane+limonene at five different compositions ranging from 99.50 to 99.93 mol% ethane. The data range within temperatures and pressures of 280–330 K and 3–6 MPa, respectively. This system also exhibits triple- and quadruple-valued dew points at certain concentrations, i.e. this binary system also shows the phenomenon of double retrograde vaporization. The results indicate that a very minor change in the concentration can vary the shape of dew point curve significantly.

Vapor−Liquid Equilibria for the Methane−Propane−Carbon Dioxide Systems at 230 K and 270 K

Vapor−liquid equilibria were measured for the binary systems methane−carbon dioxide, methane−propane, and carbon dioxide−propane at 230 K and 270 K. The ternary system methane−carbon dioxide−propane was studied at 230 K and pressures of 0.8, 4.0, and 7.0 MPa; and at 270 K for 2.8, 5.5, and 8.0 MPa. The Peng−Robinson equation of state was used to model the system.

Vapor + Liquid Equilibria for the Ternary System Methane + Ethane + Carbon Dioxide at 230 K and Its Constituent Binaries at Temperatures from 207 to 270 K

Vapor-liquid equilibrium data for the binary system methane + carbon dioxide were measured at 230, 250, and 270 K. The ethane + carbon dioxide system was studied at 207, 210, 213, 230, 250, and 270 K, and the methane + ethane system was studied at 210, 230, 250, and 270 K. Ternary vapor-liquid equilibria for the methane + ethane + carbon dioxide system were measured at 230 K over the pressure range from 1.15 to 6.59 MPa. The Peng-Robinson equation of state was used to model the systems, and binary interaction coefficients are reported.

Hyperbaric reservoir fluids: High-pressure phase behavior of asymmetric methane +n-alkane systems

In this paper, experimental three-phase equilibrium (solidn-alkane + liquid + vapor) data for binary methane +n-alkane systems are presented. For the binary system methane + tetracosane, the three-phase curve was determined based on two phase equilibrium measurements in a composition range fromxc24 = 0.0027 toxc24 = 1.0. The second critical endpoint of this system was found atp = (1114.7 ± 0.5) M Pa.T = (322.6 ± 0.25) K, and a mole fraction of tetracosane in the critical fluidphase ofxc24 = 0.0415 ± 0.0015. The second critical endpoint occurs where solid tetracosane is in equilibrium with a critical fluid phase (Sc24 +L =V). For the binary systems of methane with then-alkanes tetradecane, triacontane, tetracontane, and pentacontane, only the coordinates of the second critical endpoints were measured. The second critical endpoint temperature is found close to the atmospheric melting point temperature of then-alkane. The pressures at the second critical endpoints do not exceed 200 MPa. Based on these experimental data and data from the literature, correlations for the pressure. temperature, and fluid phase composition at the second critical endpoint of binary methane +n-alkane systems withn-alkanes between octane and pentacontane were developed.

Excess second virial coefficients for binary mixtures of carbon dioxide with methane, ethane, and propane

For the binary systems methane + carbon dioxide, ethane + carbon dioxide, and propane + carbon dioxide, measurements of the pressure change on mixing at 303.15, 313.15 and 323.15 K are reported in this paper, as well as the excess second virial coefficients calculated therefrom.

Three-phase liquid-liquid-vapor equilibria in the methane + ethane + n-hexane and methane + ethane + n-heptane systems

The three-phase L/sub 1/-L/sub 2/-V equilibria behaviour of the ternary systems methane + ethane + n-hexane and methane + ethane + n-heptane is studied. Also presented are the results for the binary system methane + n-heptane. The compositions and molar volumes of the liquid phases are reported as functions of temperature and pressure within the immiscibility regions. The two ternary systems have constituent binaries that exhibit L/sub 1/-L/sub 2/-V immiscibility (methane + n-hexane and methane + n-heptane, respectively). The addition of the third component, ethane, promotes three-phase behaviour in a region extending upward in temperature.

Excess enthalpy data for the ternary system methane—ethylene—carbon dioxide by flow calorimetry

AbstractExcess enthalpy data for the ternary system methane – ethylene – carbon dioxide was obtained utilizing an isothermal flow calorimeter. The measurements were made at three temperatures: 293.15, 305.15 and 313.15 K and pressures of 1.114, 1.520 and 3.445 MPa (11, 15 and 34 atm).The determination of excess enthalpies for the binary systems methane—ethylene, ethylene—carbon dioxide and methane—carbon dioxide has been reported in three preceeding articles, respectively: Gagné et al., 1985; Ba et al., 1979 and Barry et al., 1982a. The binary interaction coefficients kij obtained for these systems have been utilized as initial values for the optimization procedure leading to the kij for the ternary system. For the case of the ternary system studied in this investigation, two types of binary interaction coefficients kij have been determined from experimental data: kij independent of temperature and pressure and kij adjusted as function of temperature and pressure.Experimental data were compared with the predictions from Benedict—Webb—Rubin and Redlich—Kwong equations of state. In both cases, the coefficients kij dependent on temperature and pressure led to better prediction of excess enthalpies.