Hydrate-based energy storage: Studying mixed CH4/1,3-dioxane hydrates via thermodynamic modeling, in-situ Raman spectroscopy, and macroscopic kinetics

It can be foreseen that the global demand for natural gas (NG) will show an increase trend in the upcoming decades. Solidified Natural Gas (SNG) having a high energy density provides an alternative solution for the storage and transportation of NG. In this study, our focus lies on investigating the impact of 1,3-dioxane and L-tryptophan on mixed CH4/dioxane hydrate formation from multiple perspectives including thermodynamic, Raman spectra, and kinetics. The thermodynamic experimental results confirmed that the mixed CH4/dioxane hydrate can form at a moderate conditions and shows high dissociation enthalpies. A thermodynamic model based on van der Waals and Platteeuw model was applied for predicting equilibrium conditions of the Hydrate–Liquid–Vapor system, yielding an average absolute deviation ranging from 1.7% to 3.9%. Raman spectra results revealed that there is a two–stage growth mechanism for mixed CH4/dioxane hydrates. Kinetic results demonstrated that the system of CH4/5.56 mol% dioxane/water shows the highest gas uptake of 91.1 (±0.5) v/v at 287.15 K and 10.0 MPa, compared to other systems. Moreover, the addition of 1000 ppm L-tryptophan can reduce the time to reach 90% uptake (t90), showing a value of 19.9 (±1.8) minutes. The findings derived from this research are instrumental in developing the SNG technology.