The formation of clathrate hydrates
in pipelines is potentially
threatening to exploration and gas transportation in the petroleum
industry. To reduce such risks, various surfactants have been explored
as anti-agglomerants to prevent the aggregation of hydrate particles.
However, the anti-agglomeration mechanisms are not yet fully understood.
In this study, modified atomic force microscopy is first developed
to investigate the effects of two surfactants, namely, 1-naphthaleneacetic
acid and dodecylbenzenesulfonic acid, on the surface of a tetrahydrofuran
(THF) hydrate. The surfactants have remarkable effects in terms of
changing the grain size and decreasing the grain boundary depth and
surface roughness of the THF hydrate. In addition, the surfactants
reduce the quasi-liquid layer (QLL) thickness of the THF hydrate and
the adhesion forces between the hydrate and the microsphere probe.
This phenomenon may be caused by the changes induced by surfactant
molecules on the water–guest molecule structure near the gas/water
interface. Thus, hydrate growth is enhanced in the QLL. The adhesion
forces decrease linearly with QLL thickness after adding the surfactants.
These findings indicate that surfactants reduce the adhesion forces
by reducing the QLL thickness at higher temperatures. The effects
of surfactants on the QLL thickness and surface morphology of the
hydrate are investigated, providing critical information on the cohesive
behaviors among hydrate particles or between hydrate particles with
other materials. Our work provides new insights into the underlying
mechanism of how surfactants prevent hydrate aggregation, which is
crucial in hydrate-related safety management.