Measurements for the Dissociation Conditions of Methane Hydrate in the Presence of 1,3,5-Trioxane and Oxolan-2-ylmethanol

The dissociation conditions for methane hydrates in the presence of (0.0104 to 0.0350) mole fraction ((0.05 to 0.15) mass fraction) 1,3,5-trioxane aqueous or brine solutions and (0.0192 to 0.0702) mole fraction ((0.10 to 0.30) mass fraction) oxolan-2-ylmethanol (tetrahydrofurfuryl alcohol, THFA) aqueous solutions were experimentally measured in this study. The hydrate phase dissociation conditions were measured with an apparatus which was operated at high pressure and low temperature conditions. The liquid water-hydrate-vapor (L-w-H-V) three-phase equilibrium dissociation temperatures and pressures for methane hydrate in the presence of these additives were determined by employing the isochoric method. New experimental data are reported within the pressure range from (4 to 10) MPa for the methane + water + 1,3,5-trioxane hydrate system and from (9 to 15) MPa for the methane + water + oxolan-2-ylmethanol hydrate system, respectively. It is demonstrated that the addition of 1,3,5-trioxane has a promotion effect on the formation of methane hydrate. In addition, the liquid-hydrate-vapor (L-H-V) three-phase equilibrium dissociation conditions for brine solution with water and 0.011 mole fraction (0.035 mass fraction) NaCl were also measured in this study with the addition of 1,3,5-trioxane. The promotion effect for methane hydrate formation in brine environments is also observed. On the other hand, the results of adding oxolan-2-ylmethanol show the inhibition effect on the formation of methane hydrate.