Molecular modeling of interfacial properties of the hydrogen + water + decane mixture in three-phase equilibrium.

The understanding of interfacial phenomena between H 2 and geofluids is of great importance for underground H 2 storage, but requires further study. We report the first investigation on the three-phase fluid mixture containing H 2 , H 2 O, and n -C 10 H 22 . Molecular dynamics simulation and PC-SAFT density gradient theory are employed to estimate the interfacial properties under various conditions (temperature ranges from 298 to 373 K and pressure is up to around 100 MPa). Our results demonstrate that interfacial tensions (IFTs) of the H 2 -H 2 O interface in the H 2 + H 2 O + C 10 H 22 three-phase mixture are smaller than IFTs in the H 2 + H 2 O two-phase mixture. This decrement of IFT can be attributed to C 10 H 22 adsorption in the interface. Importantly, H 2 accumulates in the H 2 O-C 10 H 22 interface in the three-phase systems, which leads to weaker increments of IFT with increasing pressure compared to IFTs in the water + C 10 H 22 two-phase mixture. In addition, the IFTs of the H 2 -C 10 H 22 interface are hardly influenced by H 2 O due to the limited amount of H 2 O dissolved in nonaqueous phases. Nevertheless, positive surface excesses of H 2 O are seen in the H 2 -C 10 H 22 interfacial region. Furthermore, the values of the spreading coefficient are mostly negative revealing the presence of the three-phase contact for the H 2 + H 2 O + C 10 H 22 mixture under studied conditions.