Interfacial properties of the alkane+water system in the presence of carbon dioxide and hydrophobic silica

Abstract Molecular dynamics simulations were carried out to understand the interfacial properties of the alkane+water system in the presence of CO 2 and hydrophobic silica at temperatures from 323 to 443 K and pressures up to about 200 MPa. The simulation data were compared to predictions from density gradient theory. Our results of the interfacial tension (IFT) of the alkane+water and alkane+CO 2 +water systems were in reasonable agreement with the experimental data. At a given temperature and pressure, the IFT of the alkane+water system almost linearly increases with the number of carbon atoms in the alkane molecule n . The IFTs of the alkane+CO 2 +water system are relatively similar to those reported for the corresponding alkane+water system. The addition of CO 2 decreased the IFT of the alkane+water system. For a given n , the IFT is approximately equal for linear, branched, and cyclic alkanes in the presence of water and CO 2 . The water contact angle obtained from simulations of the alkane+water+silica system is in the range of about 117–139 ° . This contact angle decreases with pressure, and in general, the higher the temperature, the more pronounced is this pressure effect. Overall, the contact angle is higher for lower n and cyclic alkanes, but branching has no noticeable effect on the contact angle. The contact angles of the CO 2 +water+silica system were in reasonable agreement with experimental data. The contact angle increased with increasing pressure and decreasing temperature for this system. The contact angles of the dodecane+CO 2 +water+silica system are relatively similar to those reported for the corresponding dodecane+water+silica system. The addition of CO 2 increased the contact angle of the dodecane+water+silica system.