Montmorillonite–Biosurfactant Synergism: Significant Promotion of Methane Hydrate Formation Kinetics

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Gas hydrates hold great promise but are limited by stochastic nucleation and slow growth. Surfactants have attracted much attention for their promoting effect on hydrate formation kinetics, while their effect is not stable and can even inhibit nucleation. Here, we explored the synergistic effects of montmorillonite (MMT) and the degradable biosurfactant rhamnolipid (Rha) on methane hydrate formation using in situ Raman spectroscopy, kinetic experiments, and interfacial tension measurements. The results indicated that MMT significantly enhanced the promoting effect of Rha solutions of various concentrations, reducing the induction time to 30–90 min and increasing the final methane uptake to approximately 65%, which is about 15 times higher than that achieved in pure water. We proposed that the adsorption of Rha molecules on MMT led to a transformation of water structure and enhanced mass transfer, thereby achieving significant promotion of hydrate kinetics. This synergistic mechanism was also verified by the decrease in the ζ-potential of MMT particles and the changes in carbon elements on the MMT surface. These results elucidate the synergistic mechanism between surfactants and solid particles in promoting hydrate formation, providing valuable insights for the commercial application of surfactants and the advancement of artificial hydrate technology.