Hydrate-Based Gas Storage Made Greener: Methane Hydrate Formation Enhancement with a Low-Toxicity Promoter

Abstract

In this work, the role of 5.56 mol % 1,3-dioxolane (DIOX) in mixed methane hydrate formation was investigated in terms of thermodynamics, kinetics, and morphology. The results indicate that DIOX modifies the hydrate phase equilibrium, thereby promoting hydrate formation under milder conditions. A comparison between DIOX- and tetrahydrofuran (THF)-promoted hydrate formation revealed that DIOX enables a significantly faster formation rate─approximately 5 times higher than THF─although its final gas uptake is only about half that of THF. To further explore DIOX’s properties, the effects of temperature and pressure on mixed methane hydrate formation in the presence of DIOX were examined using a hybrid combinatorial reactor (HCR). Experiments were conducted at 8 MPa and temperatures of 288.2 and 293.2 K. The results demonstrate that higher temperatures lead to lower gas uptake and slower hydrate formation kinetics, as increased temperature reduces heat distribution efficiency. Additionally, the effect of pressure variations (from 8 to 4 MPa at 288.2 K) was analyzed, revealing that a lower pressure decreases both the gas uptake and formation kinetics due to a reduced driving force. Furthermore, this study investigated the synergistic effects of combining DIOX with sodium dodecyl sulfate (SDS) and amino acids (tryptophan and methionine) at 293.2 K and 8 MPa. The results indicate that the presence of SDS and amino acids reduces the induction time and slightly enhances the hydrate formation rate. Moreover, SDS significantly improves the final gas uptake, resembling the hydrate formation observed with THF. Methane recovery reached up to 95% from hydrates formed with or without copromoters, and no significant variation in formation morphology was observed in all tested conditions.

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