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.
SignificanceFormation of clathrate hydrate (CH) requires high pressures and moderate temperatures, which enable their existence in marine sediments and the permafrost region of earth. The presence of CHs in interstellar medium (ISM) is still in question due to the extreme high vacuum and ultracold conditions present there. Here, we conclusively identified methane and carbon dioxide hydrates in conditions analogous to ISM. We found that molecular mobility and interactions play crucial roles in the formation of CHs, even though there is no external pressure to force cage formation. Various chemical processes on these hydrates in ISM may lead to relevant prebiotic molecules.
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.
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.
In experimental studies, it has been observed that the presence of sodium dodecyl sulfate (SDS) significantly increases the kinetics of hydrate formation and the final water-to-hydrate conversion ratio. In this study, we intend to understand the molecular mechanism behind the effect of SDS on the formation of methane hydrate through molecular dynamics simulation. Hydrate formation conditions similar to that of laboratory experiments were chosen to study hydrate growth kinetics in 1 wt % SDS solution. We also investigate the effect of interactions with isolated SDS molecules on methane hydrate growth. It was observed that the hydrophobic tail part of the SDS molecule favorably interacts with the growing hydrate surface and may occupy the partial hydrate cages while the head groups remain exposed to water.
Molecular dynamics simulations are carried out to get insights into the interfacial behavior of the decane + brine + surfactant + CH4 + CO2 system at reservoir conditions.
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