Phase Equilibrium and Dissociation Enthalpies for Hydrates of Various Water-Insoluble Organic Promoters with Methane

Abstract

Phase equilibrium data were measured for the mixed organic hydrates with methane. The organic compounds studied are cyclopentane, cyclopentyl chloride, cyclopentanone, methylcyclopentane, cyclohexene, tetrahydrothiophene, and trimethylene sulfide, which are water-insoluble. It is found that the organic compounds + methane hydrates are more easily formed than the methane hydrate. Therefore, these organic compounds act as the hydrate formation promoters. The hydrate promotion effectivenesses with methane as a help gas can be summarized in the following order: trimethylene sulfide > cyclopentane > tetrahydrothiophene > cyclopentanone > cyclopentyl chloride and cyclohexene > methylcyclopentane. Trimethylene sulfide has the biggest effect of hydrate promotion among the promoters studied in this work. It may be a promising water-insoluble chemical promoter. It is noted that the promotion effect is heightened with the decrease of the molecular size for the seven compounds. The hydrate dissociation enthalpies were determined via the Clausius–Clapeyron equation based on the different experimental equilibrium data. The absolute value of slope k plays an important role on the ΔdissHm.