Solubility Parameter Of Liquid Research Articles

Thermodynamic investigation of asphaltene precipitation and deposition profile in wellbore: A case study

Asphaltene precipitation and deposition are considered major problems in primary, secondary and tertiary phases of oil production. These phenomena can cause partial or complete blockage in the near-wellbore region, production string and surface facilities. To study the extent of asphaltene precipitation and deposition, the wellbore pressure and temperature profiles are determined and vapor-liquid flash calculations are conducted with the aid of Peng-Robinson equation of state for a well in one of the southwest fields of Iran. Subsequently, the matching parameters of the solubility model are optimized with genetic algorithm as the search engine so that the model is tuned with experimental data of asphaltene precipitation. Finally, the rate of deposition and the resulting changes in tubing inner diameter are determined at each depth versus time. The results showed that as the fluid moves upwards from the bottom-hole until the bubble point is reached, the liquid expands and its solubility parameter slightly decreases. This leads to a discrepancy between the solubility parameter of liquid and asphaltene and the asphaltene starts to precipitate. On the other hand, in the two-phase region, liquid solubility parameter increases considerably due to gas evolution. Hence, the difference between solubility parameter of liquid and asphaltene significantly drops, leading to a considerable decrement in asphaltene precipitation. Fluid temperature can be considered as an acceptable approximation for tubing surface temperature. As long as the tubing diameter remains constant, by travelling upwards in the well, the rate of deposition per unit area decreases. At points where the tubing diameter changes, a change in liquid velocity inversely affects the rate of deposition. Well tubing blockage is more likely to occur at points where the rate of deposition per unit area has a maximum value.

Determining the solubility parameter and the cross-link density of medical grade silicones: effect of increasing the range of swelling liquids.

Four samples of four medical grade silicones were swollen in six "good" liquids (i.e. those with a good swelling ability, in which silicones swell appreciably) at 25°C, until they reached constant mass (i.e. equilibrium). The volume fraction, ϕ, of the silicone in the swollen sample was calculated for each grade of silicone. Using a combination of the six ϕ values obtained in this study and four of those obtained in a previous study, for each silicone grade, ϕ was plotted against δl, the liquid solubility parameter for the ten liquids used. Using a curve fitting technique a second-order polynomial was plotted through the data points; the minimum in this polynomial provided a value for δp (the polymer solubility parameter). Furthermore, the results showed that the δp values obtained in this study (using ten liquids) were slightly but significantly greater (p<0.05) than those obtained in a previous study (using four liquids), for grade C6-165 only. Similarly, the χ and υ values obtained in the two studies were only significantly different (p<0.05) from each other, for grade C6-165.

Enhancement of water transport through the liquid–vapor interface by surfactants

Interactions between surfactants and water were monitored from the perspective of liquid–vapor interfaces. The surfactants studied were chosen to be the paradigms of the three major types of amphiphilic molecules: the anionic surfactant (e.g. sodium dodecyl sulfate), the cationic surfactant (e.g. dodecyltrimethylammonium chloride), and the nonionic surfactant (e.g., n-dodecyl-β-D-maltoside). Droplets were deposited on octadecyltrichlorosilane (OTS) covered silicon surfaces and their contact angle and contact base diameter were observed as a function of time to obtain information on the drying dynamics. Using a new method to evaluate the solubility parameters of liquids via evaporating sessile droplets, information on the assembling of surfactants as well as their interfacial behavior at the water–vapor interface is extracted. It is concluded that surfactants accelerate drying in pre-micellar solutions. Formation of micelles retards this acceleration. Surfactants, depending on the type and concentration, interfere with the intermolecular force among liquid, with the most significant influence observed around the critical micelle concentration. Monomers with hydrogen bond-forming head groups and longer tails influence the liquid more than the other types of surfactants. Small electrolyte molecules affect the drying dynamics of ionic surfactant solutions more than nonionic surfactant solutions.

Infinite dilution partition coefficients of benzene derivative compounds in supercritical carbon dioxide + ionic liquid systems: 1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium octylsulfate [bmim][OcSO4

Infinite dilution partition coefficients of benzene and benzene derivative compounds (chlorobenzene, bromobenzene, toluene, ethylbenzene, benzaldehyde, benzyl alcohol and phenol) between supercritical carbon dioxide and ionic liquids (1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium octylsulfate [bmim][OcSO4]) were measured with a packed-column chromatographic technique. The Sanchez–Lacombe equation of state was used to correlate the data and could describe the qualitative changes of the infinite dilution partition coefficients over a wide range of temperatures (313–352K) and pressures (5–15MPa). A linear solvation energy relationship (LSER) model, LSER-δ, was developed for compressible phases that uses solute, solvent and ionic liquid solubility parameters. Partition coefficients were generally in the order of solute volatility with the exception of hydrogen bonding solutes. LSER solute volume (McGowan's volume, V) and solute dipolarity/polarizability (S) greatly affected the partition coefficient values. It was found that the McGowan's volume can be considered as a function of the CO2 solubility parameter, which may be helpful in extending LSER theory to supercritical fluid systems. Both models could describe the partition coefficient well and were useful in understanding some of the interactions of the solute with the supercritical CO2 and ionic liquid phases.

Regular Solution Theory for Low Pressure Carbon Dioxide Solubility in Room Temperature Ionic Liquids: Ionic Liquid Solubility Parameter from Activation Energy of Viscosity

The low pressure solubility of carbon dioxide in eight commercially available room temperature ionic liquids was measured at 10, 25, and 40 °C using a transient thin liquid film technique. In this paper, carbon dioxide solubility is reported as the Henry’s law constant for each system. Experimental results were interpreted using regular solution theory where Eyring’s reaction rate theory was successfully applied to estimate the solubility parameter of each ionic liquid from its activation energy of viscosity. Consistent with the regular solution theory, the carbon dioxide solubility was found to be inversely proportional to the solubility parameter of the ionic liquid, and Henry’s law constants were successfully correlated with the square of the difference between ionic liquid and carbon dioxide solubility parameters.

Swelling of medical grade silicones in liquids and calculation of their cross-link densities

Four medical grade silicones were swollen, until they reached equilibrium (i.e. constant mass) in eight liquids at 25 °C. The greatest swelling was obtained with n-heptane but the volume fraction, ϕ, of the silicones in their swollen state was not significantly different ( p < 0.05) in this liquid than in cyclohexane. For each grade of silicone, ϕ was plotted against δ l , the liquid solubility parameter, for each liquid in which it was swollen. A second-order polynomial was plotted through the results; the minimum in this polynomial provided a value for the polymer solubility parameter, δ p . The Flory polymer–liquid interaction parameter, χ, was calculated for the four best liquids, using Hildebrand's solubility parameter theory. An alternative method for calculating χ, directly from swelling measurements, was shown to produce physically unreasonable results. The cross-link density, υ, was calculated, from ϕ and χ, for each grade of silicone, using the Flory–Rehner equation. Since the values of two parameters involved in Hildebrand's theory cannot be determined reliably and because the Flory–Rehner equation is an approximation, absolute values of υ cannot be obtained. However, the relative values of υ obtained were higher for the harder grades then for the softer grades and similarly, the grades with the higher Young's modulus had higher υ values.

Direct and Indirect Quantum Mechanical QSPR Hildebrand Solubility Parameter Models

AbstractThe objectives of this study were to develop Quantitative Structure–Property Relationship (QSPR) models to predict Hildebrand solubility parameters (δt). The study investigated direct δt prediction by QSPR and indirect δt calculation from QSPR‐predicted enthalpy of vaporization values. Molecular ground‐state minimum energy conformations were identified and optimized using the AM1 semiempirical Quantum Mechanical (QM) method. Predictive multiple linear regression models were derived correlating training set experimental solubility parameters or enthalpies of vaporization with descriptors obtained from the QM calculations. A four‐descriptor Hildebrand total solubility parameter regression equation was developed where R2=0.97, R$\rm{ {_{adj}^{2}}}$=0.97, F=461.5, s2=0.53, and Root Mean Square Error (RMSE)=0.69. A four‐descriptor QSPR model to predict enthalpies of vaporization (ΔHvap−kJ/mol) was constructed where R2=0.96, R$\rm{ {_{adj}^{2}}}$=0.96, F=230.3, s2=4.75, and RMSE=2.04. δt calculations from ΔHvap correlated well with literature δt , where R2=0.96. Both of these models are statistically significant as well as predictive. The direct and indirect δt models developed here compare favorably with liquid solubility parameter estimation accuracies (10%) reported by Hoftyzer–Van Krevelen and Hoy. These methods are useful for determining the miscibility of small organic molecules, an important consideration when formulating polymer blends.

Effect of surfactant treatment on the formation of bound polymer on titanium dioxide powders

The dispersibility of agglomerates into polymeric media is affected by the interactions between the medium and the particles and between the particles themselves. In this work, we have used the amount of bound polymer as a measure of interfacial interactions between the particles and the medium. Titanium dioxide powders with surfaces modified with silica and/or alumina were analyzed for their interactions with various liquid media by suspending them in different solvents and monitoring dispersion stability for given periods of time. Applying the concept that materials which have cohesive energy densities in close range are compatible, data for the solubility parameters of liquids have been used to characterize the pigment surface. The adsorption of surfactants onto the particle surface will modify its characteristics, and consequently, the interfacial interactions with various media. Determination of the bound polymer in dispersions of different coated titania particles in linear low density poly(ethylene) showed better interactions between the polymer and the filler particles for surfactant treated powders.