Modified Density Gradient Theory for Surfactant Molecules Applied to Oil/Water Interfaces

Mu, Xiaoqun; Xi, Shun; Alpak, Faruk O.; Chapman, Walter G.

doi:10.1021/acs.iecr.8b00164

Cited by 15 publications

(15 citation statements)

References 57 publications

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“…For instance, the slope changes from about −0.10 to −0.07 mN/(m K) in the pressure range 30-100 MPa (Figure S3). These results are consistent with other theoretical [75][76][77] and simulation 52,[78][79][80] studies.…”

Section: Decane+water Systemsupporting

confidence: 93%

Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

et al. 2020

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Molecular dynamics simulations are carried out to study the two-phase behavior of the n-decane+water system in the presence of methane, carbon dioxide, and their mixture at reservoir conditions. The simulation studies were complemented by theoretical modeling using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) and density gradient theory. Our results show that the presence of methane and carbon dioxide decreases the interfacial tension (IFT) of the decane+water system. In general, the IFT increases with increasing pressure and decreasing temperature for the methane+decane+water and carbon dioxide+decane+water systems, similar to what has been found for the corresponding decane+water system. The most important finding of this study is that the presence of carbon dioxide decreases the IFT of the methane+decane+water system. The atomic density profiles provide evidence of the local accumulation of methane and carbon dioxide at the interface, in most of the studied systems. The results of this study show the preferential dissolution in the water-rich phase and enrichment at the interface for carbon dioxide in the methane+carbon dioxide+decane+water system. This indicates the preferential interaction of water with carbon dioxide relative to methane and decane. Notably, there is an enrichment of the interface by decane at high mole fractions of methane in the methane/decane-rich or methane/carbon dioxide/decane-rich phase. Overall, the solubility of methane and carbon dioxide in the water-rich phase increases with increasing pressure and temperature.Additionally, we find that the overall performance of the PC-SAFT EoS and the cubic-plus-association EoS is similar with respect to the calculation of bulk and interfacial properties of these systems.

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Section: Decane+water Systemsupporting

confidence: 93%

Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

et al. 2020

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“…However, the agreement is poor, for example, at low temperatures, because the simulated density profile of decane shows artificial oscillations as described above. In general, for all systems, decane has a negative surface excess due to unfavorable hydrophilic–hydrophobic interactions between H 2 O and decane. ,− The increase in IFT with pressure is attributed to the negative surface excess of decane (see eq and Figure ). This surface excess was found to decrease with temperature at a fixed pressure.…”

Section: Resultsmentioning

confidence: 98%

Bulk and Interfacial Properties of the Decane + Brine System in the Presence of Carbon Dioxide, Methane, and Their Mixture

Choudhary

Ruslan

Nair

et al. 2021

Ind. Eng. Chem. Res.

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Bulk and interfacial properties of decane in the presence of carbon dioxide, methane, and their mixture nilesh choudhary, Arun Kumar narayanan nair * , Mohd fuad Anwari che Ruslan & Shuyu Sun * Molecular dynamics simulations were performed to study the bulk and interfacial properties of methane + n-decane, carbon dioxide + n-decane, and methane + carbon dioxide + n-decane systems under geological conditions. in addition, theoretical calculations using the predictive peng-Robinson equation of state and density gradient theory are carried out to compare with the simulation data.A key finding is the preferential dissolution in the decane-rich phase and adsorption at the interface for carbon dioxide from the methane/carbon dioxide mixture. in general, both the gas solubility and the swelling factor increase with increasing pressure and decreasing temperature. interestingly, the methane solubility and the swelling of the methane + n-decane system are not strongly influenced by temperature. our results also show that the presence of methane increases the interfacial tension (ift) of the carbon dioxide + n-decane system. typically, the ift of the studied systems decreases with increasing pressure and temperature. the relatively higher surface excess of the carbon dioxide + n-decane system results in a steeper decrease in its ift as a function of pressure. Such systematic investigations may help to understand the behavior of the carbon dioxide-oil system in the presence of impurities such as methane for the design and operation of carbon capture and storage and enhanced oil recovery processes.

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“…28 The model was also extended to block copolymers 66 and reformulated in a density gradient theory. 67 Several variations of SAFT have been proposed since its development: soft-SAFT, 68,69 SAFT with a variable range of the potential, 70,71 SAFT-γ Mie, 72,73 and perturbed-chain SAFT (PC-SAFT). 74−79 While in SAFT, the dispersion contribution of individual segments on a chain is equal to the contribution of nonbonded segments, 57 PC-SAFT incorporates the chain structure in the dispersion term, which improves the description of the phase behavior for several systems.…”

Section: ■ Introductionmentioning

confidence: 99%

Surfactant Modeling Using Classical Density Functional Theory and a Group Contribution PC-SAFT Approach

Rehner

Bursik

Groß

2021

Ind. Eng. Chem. Res.

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Models for surfactants need to incorporate the amphiphilic character of the molecules to describe key properties such as the adsorption at interfaces and the reduction of interfacial tensions. One possibility is to model the surfactant molecules as heteronuclear chains. Therefore, we revisit the heterosegmented density functional theory and present a theory consistent with the group contribution perturbed-chain statistical associating fluid theory equation of state. The model is used to study water/surfactant and water/surfactant/octane systems with surfactants from the group of polyethylene glycol alkyl ethers, a commonly used group of nonionic surfactants. The model parameters are obtained by fitting to pure component data of small surfactants. Binary interaction parameters are required to model the water/alkane subsystem and to account for the polarity of the head groups of the surfactant. The model is able to reproduce the significant enrichment of surfactant molecules at both vapor–liquid surfaces and liquid–liquid interfaces and the corresponding reduction of interfacial tensions. For liquid–liquid interfaces, the competing solubility of the surfactant in both phases has to be taken into account when searching for an optimal surfactant molecule.

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Modified Density Gradient Theory for Surfactant Molecules Applied to Oil/Water Interfaces

Cited by 15 publications

References 57 publications

Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

Bulk and Interfacial Properties of the Decane + Water System in the Presence of Methane, Carbon Dioxide, and Their Mixture

Bulk and Interfacial Properties of the Decane + Brine System in the Presence of Carbon Dioxide, Methane, and Their Mixture

Surfactant Modeling Using Classical Density Functional Theory and a Group Contribution PC-SAFT Approach

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