Pressure Dependence Of Interfacial Tension Research Articles

Modeling of Pressure Dependence of Interfacial Tension Behaviors of Supercritical CO2 + Crude Oil Systems Using a Basic Parachor Expression

Parachor based expressions (basic and mechanistic) are often used to model the experimentally observed pressure dependence of interfacial tension (IFT) behaviors of complex supercritical carbon dioxide (sc-CO2) and crude oil mixtures at elevated temperatures. However, such modeling requires various input data (e.g. compositions and densities of the equilibrium liquid and vapor phases, and molecular weights and diffusion coefficients for various components present in the system). In the absence of measured data, often phase behavior packages are used for obtaining these input data for performing calculations. Very few researchers have used experimentally measured input data for performing parachor based modeling of the experimental IFT behaviors of sc-CO2 and crude oil systems that are of particular interest to CO2 injection in porous media based enhanced oil recovery (EOR) operations.This study presents the results of parachor based modeling performed to predict pressure dependence of IFT behaviors of a complex sc-CO2 and crude oil system for which experimentally measured data is available in public domain. Though parachor model based on calculated IFT behaviors shows significant deviation from the measured behaviors in high IFT region, difference between the calculated and the experimental behaviors appears to vanish in low IFT region. These observations suggest that basic parachor expression based calculated IFT behaviors in low IFT region follow the experimental IFT behaviors more closely.An analysis of published studies (basic and mechanistic parachor expressions based on modeling of pressure dependence of IFT behaviors of both standard and complex sc-CO2 and crude oil systems) and the results of this study reinforce the need of better description of gas-oil interactions for robust modeling of pressure dependence of IFT behavior of these complex systems.

Modeling of Pressure Dependence of Interfacial Tension Behaviors of a Complex Supercritical CO2 + Live Crude Oil System Using a Basic Parachor Expression

Parachor based basic expressions are often used to model the experimentally observed pressure dependence of interfacial tension (IFT) behaviors of complex supercritical CO2 + crude oil (dead or live) mixtures at elevated temperatures. However, such modeling requires compositions and densities of the equilibrium liquid and vapor phases and molecular weights of various components present in the system. In the absence of measured data, often phase behavior packages are used for obtaining these input data for performing calculations. Very few researchers have used experimentally measured input data for performing parachor based modeling of the experimental IFT behaviors of complex supercritical CO2 + live crude oil systems. This study presents the results of a basic parachor model based modeling of pressure dependence of IFT behaviors of a complex supercritical CO2 + live crude oil system for which experimentally measured input data is available in public domain. Though the calculated IFT behaviors showed significant deviation from the experimentally measured behaviors at a given pressure, calculated IFT versus pressure trends appeared to follow the experimental observed trends closely. Also, despite a large variation in the compositions of feed supercritical CO2 + live crude oil mixtures, both trends (calculated and experimental) converged rapidly to attain a near zero IFT condition at more or less same pressure.

Interfacial Tension between Methane and Octane at Elevated Pressure at Five Temperatures from (274.2 to 282.2) K

The pressure dependence of interfacial tension between methane and octane at five temperatures has been determined using the pendant-drop method. The experimental results show that the interfacial tension value decreases with the increased temperature and pressure. The higher temperature and pressure has a positive contribution on weakening the intermolecular interaction between methane and octane. The surface excess concentration for methane on octane at different temperatures and pressures and the surface free energies of adsorption for (methane + octane) were calculated and compared with the (methane + water) system. The calculated results show that methane is more preferred for the adsorption on octane than on water.

Thermodynamic Study on Phase Transition in Adsorbed Film of Fluoroalkanol at the Hexane/Water Interface. 7. Pressure Effect on the Miscibility in the Adsorbed Film of Alkanol and Fluoroalkanol Mixture

The Miscibility of 1-icosanol (C20OH) and 1,1,2,2-tetrahydroheptadecafluorodecanol (FC10OH) in the adsorbed film at the hexane/water interface was studied by measuring the pressure dependence of interfacial tension at various compositions and analyzing the experimental results thermodynamically. The criterion of ideal mixing in the adsorbed film with respect to the volume of adsorption v was constructed and used to examine the nonideal mixing of C20OH and FC10OH in the adsorbed film. It is found that the v value deviates positively from the ideal mixing line, and therefore the mixing of C20OH and FC10OH molecules causes a larger increase in volume in the adsorbed film than in the bulk solution. Furthermore, the excess volume of adsorption vH,E was positive and its magnitude was comparable to that of the liquid alkane and perfluoroalkane mixture. This result is probably due to the increase in the occupied area of individual components at the interface. To gain a better understanding of the miscibility of C...

Thermodynamic Study on Phase Transition in Adsorbed Film of Fluoroalkanol at the Hexane/Water Interface. 6. Pressure Effect on the Phase Transition in the Adsorbed Film of Alkanol and Fluoroalkanol Mixture

The phase transition in the adsorbed film of 1-icosanol (C20OH) and 1,1,2,2-tetrahydroheptadecafluorodecanol (FC10OH) mixture at the hexane/water interface was studied by measuring the pressure dependence of interfacial tension at a specific composition of FC10OH X2 = 0.280 and 298.15 K and evaluating the volume change of adsorption. By drawing the interfacial pressure π vs mean area per adsorbed molecule A curve, it was clarified that three types of first-order phase transitions (gaseous−expanded, expanded−FC10OH condensed, and FC10OH condensed−C20OH condensed) take place in the adsorbed film. The phase transition from the FC10OH condensed to the C20OH condensed state was accompanied by a decrease of the volume change associated with adsorption Δν. By evaluating the partial molar volume change of adsorption, − , and comparing its pressure dependence between the FC10OH condensed and C20OH condensed states, it was suggested that the pressure dependence of the partial molar volume is in the order of ∂ /∂p > ∂ /∂p > ∂ /∂p ≈ ∂ /∂p. Furthermore, it was found that the transition pressure πeq of the FC10OH condensed−C20OH condensed transition (second transition) increases and the corresponding one of the expanded−FC10OH condensed transition (first transition) decreases with increasing pressure. This difference was explained by means of the − values at the phase transition point.

Pressure dependence of interfacial tension of hydrocarbon—water systems using axisymmetric drop shape analysis

A number of theories suggest that the pressure (P) dependence of interfacial tension (γ) (the slope of the γ-P curve) is related to the thickness of the liquid—fluid interface. High quality data in this area are scarce; thus testing such theories is difficult. However, with the advent of ADSA (axisymmetric drop shape analysis), γ and hence its pressure coefficient can be measured with much greater accuracy than the more traditional methods were capable of. A study was undertaken using ADSA to determine both the time and pressure dependences of interfacial tension for the pure n-decane—water system in the 0–35 MPa pressure range. The results indicate that the γ-P relationship is highly linear and that the pressure coefficient for this system at 21.2°C is (22.37 ± 0.35) × 10−12 m, while at 21.5°C this value increases to (23.29 ± 0.48) × 10−12 m.

Thermodynamic consideration of the pressure dependence of interfacial tension

The pressure dependence of the interfacial tension of oil/water interface is related thermodynamically to the excess number of moles of oil per unit area defined with reference to Gibbs' dividing surface, the distance between the two dividing planes satisfying the Hansen convention, or the volume of interface formation. In order to know what the most useful thermodynamic concept is, the inter-facial tension has been measured as a function of pressure for the interfaces of four members of the homologous series of alkane (hexane, octane, decane, and dodecane), the substances of symmetrical ring structure (cyclohexane and benzene), and the substances of unsymmetrical linear structure (butyl bromide and hexyl bromide) against water. It has been clarified that the volume of interface formation is appropriate to elucidate the behavior of oil and water molecules in the interfacial region. Further, this conclusion has been substantiated by measuring the interfacial tension as a function of temperature and evaluating the entropy and energy of interface formation.