Gas hydrate phase equilibrium in the system methane–carbon dioxide–neohexane and water

Incipient equilibrium hydrate formation conditions for the methane–carbon dioxide–neohexane–water system were obtained by employing the isothermal pressure search method. Two gas mixtures containing 80 and 50% methane respectively on a water-free basis were used. At a given temperature, the incipient hydrate formation pressure from the 80–20 gas mixture with neohexane was found to be lower by about 1 MPa from the hydrate formation pressure for the system without neohexane. This is considered to be an indication that structure H hydrate forms. The results for the 50–50 gas mixture, however, indicate that only below a temperature of approximately 277.5 K it is possible to form structure H hydrate.