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

Molecular dynamics simulations were carried out to understand the interfacial properties of the alkane+water system in the presence of CO 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+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 . The IFTs of the alkane+CO+water system are relatively similar to those reported for the corresponding alkane+water system. The addition of CO decreased the IFT of the alkane+water system. For a given , the IFT is approximately equal for linear, branched, and cyclic alkanes in the presence of water and CO. 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 and cyclic alkanes, but branching has no noticeable effect on the contact angle. The contact angles of the CO+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+water+silica system are relatively similar to those reported for the corresponding dodecane+water+silica system. The addition of CO increased the contact angle of the dodecane+water+silica system.