Sodium Dodecyl Sulfate Preferentially Promotes Enclathration of Methane in Mixed Methane-Tetrahydrofuran Hydrates.

Methane storage in mixed hydrates is advantageous due to faster kinetics and added stability. However, capacity needs to be improved. Here we study mixed hydrates of methane (CH) and tetrahydrofuran (THF), in the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter for hydrate formation. We report the co-existence of pure methane (sI) and mixed CH-THF hydrates (sII) in the presence of SDS; however, in the absence of SDS, co-existence of pure THF (sII) and mixed CH-THF hydrates (sII) was observed. Thus the presence of SDS preferentially promotes the enclathration of methane over that of THF. Furthermore, through in situ Raman spectrometry, complemented by high-pressure differential scanning calorimeter, we present temperature-dependent methane occupancy in small and large cages of sI and sII hydrates. Our findings offer new insights for enhancing the methane storage capacity in more stable sII hydrate configuration for large-scale methane storage via solidified natural gas technology.