Measurement for the Dissociation Conditions of Methane and Carbon Dioxide Hydrate in the Presence of Additive Materials

We report in this study the dissociation conditions for the carbon dioxide hydrate in the presence of additive materials. We measured the hydrate-water-vapor (H-Lw-V) three-phase equilibrium data using the isochoric method. Examples of these phase equilibrium data for the additive materials of 1,3,5-trioxane, 2,5-dihydrofuran, 1,3-dioxolane, and 3,4-dihydro-2H-pyran are presented. The experimental pressure range is from 1.6 to 3.3 MPa, and the concentration of each additive is at 10 wt%. The experimental results indicate that cyclic ethers of 1,3,5-trioxane, 2,5-dihydrofuran, and 1,3-dioxolane promote the formation of carbon dioxide hydrate. Their promotion effects at a given pressure are up to 5 K, 6.9 K, and 4.2 K, respectively, The additive material of 3,4-dihydro-2H-pyran, however, shows the inhibitor behavior. The average inhibition effect is about 1.3 K at a given pressure.