A comparative investigation of methane hydrate formation from 0.1 wt % solutions of an alkaline extract of humic acids (HA) and sodium dodecyl sulfate (SDS) has been carried out. It was demonstrated that the hydrate grows as a voluminous loose mass squeezed onto the reactor walls in both cases. It turns that about 75% of water transforms into hydrate within 15−20 min. Thus, natural HA can act as kinetic hydrate promoters. At the same time, SDS increases the hydrate nucleation rate compared to pure water under the studied conditions (12.5−13.0 MPa and −5 °C), while HA retards the hydrate nucleation. Visual observation of the hydrate growth in the solutions of HA and SDS allowed us to propose a new mechanism of hydrate growth in the form of a porous loose mass squeezed upward over the reactor walls. The mechanism relates to overgrowing of the hydrate film formed at the gas−solution interface into the solution volume. This results in squeezing some part of the solution onto the reactor walls. Simultaneous contact of the gas, solution, and hydrate facilitates the rapid transformation of the squeezing solution into a loose hydrate mass. Then this mass soaks up the solution due to the capillary forces.

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The results of visual studies of the growth of methane and carbon dioxide hydrates from highly dilute aqueous solutions of acids and alkalis, as well as from the same solutions with the addition of 0.1 wt % sodium dodecyl sulfate, are presented. It was found that in addition to the growth of hydrate films at the water−gas interface (for solutions without sodium dodecyl sulfate) and the growth of a loose mass of hydrate on the walls of the reactor in the case of solutions with sodium dodecyl sulfate, there is also growth of the hydrate film on the free walls of the reactor. We speculate what these hydrate films form from the wetting water films located on the walls. In addition, growth of relatively large hydrate agglomerates on the reactor walls was observed. They look like "growing directly from the wall". Presumably, this is due to the possibility of film transfer of water between the formed hydrate films and the walls of the reactor. Possible features of the hydrate formation process caused by the formation of hydrates on wetting films are also discussed.