Influence of cationic and non-ionic surfactants on the kinetics of mixed hydrogen/tetrahydrofuran hydrates

• Cationic and non-ionic surfactant effect on the formation of H2/THF mixed hydrates.
• Presence of THF retards the kinetic promotion effect of surfactants for hydrate formation.
• Surfactant effect on mixed THF hydrate formation is characteristic of the guest gas.
• Surfactant did not influence the dissociation kinetics of H2/THF mixed hydrates.

In this study, the kinetics of mixed hydrogen/tetrahydrofuran (THF) hydrate formation in presence of cationic dodecyl trimethylammonium chloride (DTAC) surfactant and non-ionic Tween-20 (Polysorbate 20) surfactant was evaluated. Stoichiometric concentration of 5.6 mol% THF solution with varying surfactant concentrations from 0.01 wt% to 1 wt% were experimented and their effect on the mixed hydrogen/THF hydrate formation was studied. Marginal improvement in the mixed hydrogen/THF hydrate formation rates were observed for both the chosen surfactants with maximum of about 20% increase using 0.5 wt% DTAC and 0.1 wt% Tween-20. Decomposition kinetics of mixed hydrogen/THF hydrates using thermal stimulation (ΔT=20 K) with and without stirring showed that stirring improved the decomposition kinetics with t90 of 22.2(±0.8) min in comparison to t90 of 29.1(±0.6) min for the experiments conducted without stirring. The presence of surfactant did not significantly affect the decomposition kinetics for experiments conducted both with and without stirring. Methane/THF mixed hydrate formation under similar experimental conditions studied show that the presence of 0.5 wt% DTAC surfactant resulted in reduction of hydrate formation rates by approximately 20%. The effect of surfactant in presence of THF characteristically differs depending upon the guest gas and the system under investigation.

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