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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