Isothermal PρT measurements on Qatar’s North Field type synthetic natural gas mixtures using a vibrating-tube densimeter

Pressure–density–temperature (PρT) measurements of five natural gas mixtures that represent Qatar’s North Field natural gas reservoirs were carried out at temperatures from (250 to 450) K and at pressures up to 65 MPa by using a Anton Paar® (Graz, Austria) vibrating tube densimeter DMA 512P high-pressure cell. Total 20 isotherms from 250 K by 10 K intervals up to 450 K were measured. Experimental density data were compared with two main industry standard equations of state (EOS) namely AGA8-DC92 EOS and GERG2008 EOS. Comparisons of the experimental data with respect to AGA8-DC92 EOS and GERG2008 EOS resulted in prediction deviation ranges of (0.05 to −0.5)% and (0.25 to −0.5)% respectively.     

Thermodynamic properties of synthetic natural gases: Part 4. Dew point curves of synthetic natural gases and their mixtures with water: measurement and correlation

Experimental measurements of dew points for five synthetic natural gases (SNG)+water mixtures were carried out between 2.1×10⁵ and 73.2×10⁵ Pa in the temperature range from 224.3 to 270.2 K. The experimental results were analysed in terms of both an equation of state (EOS) model and an excess function–EOS method, which reproduced the experimental data with an AAD from 2.1 to 3.4 K and from 1.9 to 3.0 K, respectively.     

Solubility of carbon dioxide,methane, and ethane in 1-butanol and saturated liquid densities and viscosities

A designed pressure–volume–temperature (PVT) apparatus has been used to measure the (vapor + liquid) equilibrium properties of three binary mixtures (methane +, ethane +, and carbon dioxide + 1-butanol) at two temperatures (303 and 323) K and at the pressures up to 6 MPa. The solubility of the compressed gases in 1-butanol and the saturated liquid densities and viscosities were measured. In addition, the density and viscosity of pure 1-butanol were measured at two temperatures (303 and 323) K and at the pressures up to 10 MPa. The experimental results show that the solubility of the gases in 1-butanol increases with pressure and decreases with temperature. The dissolution of gases in 1-butanol causes a decline in the viscosity of liquid phase. The saturated liquid density follows a decreasing trend with the solubility of methane and ethane. However, the dissolution of carbon dioxide in 1-butanol leads to an increase in the density of liquid phase. The experimental data are well correlated with Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) equations of state (EOSs). SRK EOS was slightly superior for correlating the saturated liquid densities.     

Phase equilibrium measurements of (methane + benzene) and (methane + methylbenzene) at temperatures from (188 to 348) K and pressures to 13 MPa

New isothermal pTxy data are reported for (methane + benzene) and (methane + methylbenzene (toluene)) at pressures up to 13 MPa over the temperature range (188 to 313) K using a custom-built (vapor + liquid) equilibrium (VLE) apparatus. The aim of this work was to investigate literature data inconsistencies and to extend the measurements to lower temperatures. For (methane (1) + benzene (2)), measurements were made along six isotherms from (233 to 348) K at pressures to 9.6 MPa. At temperatures below 279 K there was evidence of a solid phase, and thus only vapor phase samples were analyzed at these temperatures. For the (methane (1) + methylbenzene (3)) system, measurements were made along seven isotherms from T = (188 to 313) K at pressures up to 13 MPa. Along the 198 K isotherm, a significant change in the data’s p,x slope was observed indicating (liquid + liquid) equilibria at higher pressures. The data were compared with literature data and with calculations made using the Peng–Robinson (PR) equation of state (EOS). For both binary systems our data agree with much of the literature data that also deviate from the EOS in a similar manner. However, the data of Elbishlawi and Spencer (1951) for both binary systems, which appear to have received an equal weighting to other data in the EOS development, are inconsistent with the results of our measurements and data from other literature sources.     

Vapor–liquid equilibria for the ternary mixture of carbon dioxide + 1-propanol + propyl acetate at elevated pressures

Vapor–liquid equilibrium (VLE) data for the ternary mixture of carbon dioxide, 1-propanol and propyl acetate were measured in this study at 308.2, 313.2, and 318.2 K, and at pressures ranging from 4 to 10 MPa. A static type phase equilibrium apparatus with visual sapphire windows was used in the experimental measurements. New VLE data for CO₂ in the mixed solvent were presented. These ternary VLE data at elevated pressures were also correlated using either the modified Soave–Redlich–Kwong or Peng–Robinson equation of state (EOS), and by employing either the van der Waals one-fluid or Huron–Vidal mixing model. Satisfactory correlation results from both EOS models are reported with temperature-independent binary interaction parameters. It is observed that at 318.2 K and 10 MPa, 1-propanol may probably be separated from propyl acetate into the vapor phase at the entire concentration range in the presence of high pressure CO₂.     

Phase equilibrium data for the ternary system (propane + chloroform + oryzanol)

The compound oryzanol available in the rice bran (oriza sativa) is well known for its antioxidant activity. Phase equilibrium data involving oryzanol in compressed fluids, hardly found in the literature, are important to provide the basis for the extraction and fractionation processes. In this sense, the aim of this work is to report phase equilibrium measurements for the system (γ-oryzanol + chloroform) in compressed propane. Phase equilibrium experiments were performed using the static synthetic method (cloud points transition data) in a high-pressure variable-volume view cell in the temperature range of 303 K to 353 K, pressures up to 17 MPa, for oryzanol overall mass fractions of 2 wt%, 5 wt% and 10 wt% in (propane + chloroform) mixtures. A complex phase behaviour comprising vapour–liquid, liquid–liquid, vapour–liquid–liquid, solid–liquid, solid–liquid–liquid, solid–liquid–liquid–vapour transitions were visually observed for the system studied.     

Vapor–liquid equilibrium of methane and methane + nitrogen and an equimolar hexane + decane mixture under isothermal conditions

Experimental vapor–liquid equilibrium data of the ternary system composed of methane and an equimolar hexane + decane mixture are reported. The experimental measurements were carried out under isothermal conditions at 258, 273, and 298 K in the pressure range 1–19 MPa. Also, experimental vapor–liquid measurements were carried out for the quaternary system methane + nitrogen and an equimolar hexane + decane mixture, at 258 K in the range 3.5–12 MPa. The results for the ternary system show that the solubility of methane in the equimolar mixture of alkanes increases when the pressure is increased at constant temperature and it increases as the temperature decreases in the whole pressure range studied. For the quaternary system with a constant amount of nitrogen, the solubility of methane in the liquid phase increases as the pressure increases at the studied temperature. The experimental results for the ternary system were satisfactorily correlated with the Peng–Robinson equation of state in the ranges of pressure and temperature studied. The equation of state was used to predict the behavior of the quaternary system using binary interaction parameters. The applicability of the principle of congruence was corroborated by comparing the vapor–liquid behavior of methane in the equimolar hexane + decane mixture with that in pure octane, at the three temperatures studied in this work.     

High-pressure phase equilibria in the (carbon dioxide + 1-hexanol) system

(Vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) data for the (carbon dioxide + 1-hexanol) system were measured at (293.15, 303.15, 313.15, 333.15, and 353.15) K. Phase behaviour 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 (0.6 and 14.49) MPa. The Soave–Redlich–Kwong (SRK) equation of state (EOS) with classical van der Waals mixing rules (two-parameters conventional mixing rule, 2PCMR), was used in a semi-predictive approach, in order to represent the complex phase behaviour (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behaviour is reasonably well predicted.     

Vapor–liquid equilibria in the binary system (−)-beta-pinene + (+)-fenchone: Analysis in terms of group contributions models of some binary systems containing terpenoids

Isobaric vapor–liquid equilibrium measurements are reported for the binary system (−)-beta-pinene + (+)-fenchone at the constant pressure of 13.33 kPa in the temperature range from 341.60 K to 393.25 K. The boiling temperatures of the mixtures were also measured at seven constant compositions in the pressure range from 2.56 kPa to 20.80 kPa. The experimental data were found to be thermodynamically consistent. Reduction of the vapor–liquid equilibrium data was carried out by means of the Wilson, NRTL and UNIQUAC equations. Our data on vapor–liquid equilibria for mixtures containing terpenoids are examined in terms of the DISQUAC and modified UNIFAC (Dortmund) group contributions models. Interaction parameters of the DISQUAC model are reported.     

(Vapor + liquid) equilibrium properties of (ethane + ethanol) system at (295, 303, and 313) K

The (vapor + liquid) equilibrium data for binary system of (ethane + ethanol) at three temperatures (295, 303, and 313) K were measured using a designed pressure–volume–temperature (PVT) apparatus. A wide range of pressures, (1 to 5) MPa, were considered for the measurements. The phase composition, saturated density, and viscosity of liquid phase were measured for each pressure and temperature. The experimental (vapor + liquid) equilibrium data were compared with the modeling results obtained using the Peng–Robinson and Soave–Redlich–Kwong equations of state.     

Characterizing phase transitions in liquid cesium by a soft-core and large-attraction equation of state

This paper investigates to identify phase transitions in condensed liquid cesium metal by considering the variation of intermolecular potential parameters ɛ and r_m in the whole liquid range, with ɛ being the potential well-depth and r_m the position of minimum potential. These parameters were obtained from the parameters of a new equation of state that was derived recently by using the characteristic potential function. By this method, transitions at about 575, 800, 1000, 1350, and 1650 K were identified. Transitions at 575, 800, and 1000 K are weak but, the one at 1350 K is very significant and has been explored experimentally and theoretically as the metal non-metal transition (MNMT), which is a phase transition before the critical condition dominates the thermodynamics. Also variations of the linear correlation coefficient of the isotherms generate a spot point pattern of these transitions. Our observations at 575 K for ɛ and r_m are in accord with the anomalies in adiabatic thermal coefficient of pressure, density, viscosity, electrical conductivity, and structure factor.     

Quaternary liquid–liquid equilibrium for water + 1-propanol + cesium sulfate + cesium chloride at 25 °C

Liquid–liquid equilibria for the quaternary system water + 1-propanol + cesium sulfate + cesium chloride were measured at 25 °C. The binodal curves and tie lines for quaternary system have been determined in order to investigate salting effects. Experimental tie lines were compared with values predicated by a modification of the Eisen–Joffe equation.     

The experiments and correlations of the solubility of ethylene in toluene solvent

Polymer cyclic olefin copolymer (COC) is produced from the reaction of attaching ethyl groups to the norbornene monomer in liquid phase. The first step of process is dissolving ethylene in a liquid phase where toluene is present as a cosolvent. Thus, the solubility of ethylene in liquid toluene is the most important factor affecting the production of COC. In this study, the solubility of ethylene in toluene was measured in the temperature range from 323.15 to 423.15 K and pressure range from 5 to 25 bar. The experiments were conducted by the method of pressure decaying with a newly designed apparatus. The experimental results show that the solubility of ethylene in toluene increases with increasing pressure but decreases with increasing temperature.The experimental solubility data were expressed in the vapor–liquid equilibrium relationship and correlated fairly well by the bubble–pressure calculation with the Peng–Robinson equation of state (PR EOS) incorporated with the van der Waals one-fluid and the Zhong–Masuoka mixing rules with the consideration of binary interaction parameters. The results showed the van der Waals (vdW-1) mixing rule is slightly better than the Z–M mixing rule for pressure correlation but the Z–M mixing rule is slightly better for vapor composition correlation.A semi-empirical solubility equation with four parameters for the present binary system was proposed in this study. This proposed model estimates the solubility easier and as accurate as the PR EOS does for the present system.     

High pressure phase equilibria in the system 1,1,1,2-tetrafluoroethane + heptylbenzene

Vapour–liquid, liquid–liquid and liquid–liquid–vapour equilibria for the system 1,1,1,2-tetrafluoroethane + heptylbenzene were determined in the temperature range from 260 to 400 K and at pressures up to 12 MPa. The system was found to be a type II system according to the classification of Van Konynenburg and Scott. The (l₂=l₁)g critical endpoint was found at T=320.07 K and P=1.155 MPa. The mole fraction of heptylbenzene in the critical liquid phase in the critical endpoint is approximately 0.20.     

Dew points of binary carbon dioxide + water and ternary carbon dioxide + water + methanol mixtures: Measurement and modelling

Dew points for four carbon dioxide + water mixtures between 1.2×10⁵ and 41.1×10⁵ Pa in the temperature range from 251.9 to 288.2 K, and eight carbon dioxide + water + methanol mixtures between 1.2×10⁵ and 43.5×10⁵ Pa and temperatures from 246.0 to 289.0 K were experimentally determined. The experimental results obtained on the binary and ternary systems were analysed in terms of a predictive excess function–equation of state (EF–EOS) method, which reproduced the experimental dew point temperature data with absolute average deviation (AAD) between 0.8 and 1.8 K for the systems with water, and from 0.0 to 2.7 K for the systems with water and methanol. The experimental results obtained for carbon dioxide + water mixtures, with molar fraction of water lower than 0.00174, at pressure values higher than 5×10⁵ Pa were also compared to a predictive equation of state model. It reproduced experimental dew point temperature data with AAD between 0.2 and 0.6 K.     

High-pressure phase equilibrium for the binary systems of {carbon dioxide (1) + dimethyl carbonate (2)} and {carbon dioxide (1) + diethyl carbonate (2)} at temperatures of 273 K, 283 K,and 293 K

Phase equilibrium data for the binary systems {carbon dioxide (CO₂) + dimethyl carbonate (DMC)} and {carbon dioxide (CO₂) + diethyl carbonate (DEC)} were measured at temperatures of 273 K, 283 K and 293 K in the pressure range of 0.5 MPa to 4.0 MPa. The measurements were carried out in a cylindrical autoclave with a moveable piston and an observation window. The experimental data were correlated with the Peng–Robison (PR) equation of state (EOS) and the Peng–Robinson–Stryjek–Vera (PRSV) equation of state with van der Waals-1 or Panagiotopoulos–Reid mixing rules. The correlations produced reasonable values for the interaction parameters. The comparisons between calculation results and experimental data indicate that the PRSV equation of state coupled with the Panagiotopoulos–Reid mixing rule produced the better correlated results.     

On the existence of temperature induced changes in the magnetic topology of crystals that show no first-order crystallographic phase transitions

The First-Principles Bottom–Up study of the 88 K and 273 K X-ray diffraction structures of the bis-2,3-dimethylpyridinium tetrabromocuprate molecular magnet shows that the analysis of the magnetic properties of a molecule-based magnet, that does not present any first order polymorphic transition in the range of temperature studied, depends on the X-ray structure employed. The reason is the thermal expansion anisotropy when the crystal goes from the low temperature phase to 273 K, which induces changes in the radical–radical J_AB interactions. As a consequence, the magnetic topology of the low temperature and 273 K structures change, a fact that induces a change in the macroscopic magnetic susceptibility curve (only the 88 K structure of bis-2,3-dimethylpyridinium tetrabromocuprate reproduces well the two-leg spin ladder experimental properties of this magnet). When anisotropic thermal effects are suspected one should use low temperature structures to study the magnetic properties at low temperature, and high temperature structures for the study of the magnetic properties in that range of temperatures.     

(Vapour + liquid) equilibria of the {1,1,1-trifluoroethane (HFC-143a) + isobutene} system

Isothermal (vapour + liquid) equilibrium data were measured for the {1,1,1-trifluoroethane (HFC-143a) + isobutene} as an alternative refrigerant in the temperature range from (273.15 to 348.15) K at 15 K intervals. A circulating-type apparatus with on-line gas chromatography was used in these experiments. The experimental data were correlated well by Peng–Robinson equation of state using the Wong–Sandler mixing rules.     

Excess molar volume,viscosity, and refractive index study for the ternary mixture {2-methyl-2-butanol (1) + tetrahydrofuran (2) + propylamine (3)} at different temperatures. Application of the ERAS-model and Peng–Robinson–Stryjek–Vera equation of state

Densities, viscosities, and refractive indices of the ternary mixture consist of {2-methyl-2-butanol (1) + tetrahydrofuran (THF) (2) + propylamine (3)} at a temperature of 298.15 K and related binary mixtures were measured at temperatures of (288.15, 298.15, and 308.15) K at ambient pressure. Data were used to calculate the excess molar volumes and the deviations of the viscosity and refractive index. The Redlich–Kister and the Cibulka equations were used for correlating binary and ternary properties, respectively. The ERAS-model has been applied for describing the binary and ternary excess molar volumes and also Peng–Robinson–Stryjek–Vera (PRSV) equation of state (EOS) has been used to predict the binary and ternary excess molar volumes and viscosities.