(411b) Investigation of Hydrate Shell Formation on Water-Containing Particles

The hydrate formation has been controlled by engineering the interface between host and guest molecules.Water is completely enclosed by permeable shell of the microcapsules from gas or oil environment, which allows limited diffusion of water and guest molecules, retarding the hydrate formation. The shells are cracked upon the hydrate formation as the hydrates are nucleated and grown within the shell at which the molecules are brought into a contact. In a static condition, the cracks are formed in the thin part of shell, which then slowly propagate whole part as the hydrate is further grown at the gaps of cracks. By contrast, in a dynamic condition of shear flow, the cracks are formed, along which microcapsules are rapidly widened by the shear stress. The microcapsules can be further engineered to produce microcarriers for delivery of inhibitors against hydrate formation. As we confirmed, the rupturing of polymeric shell is triggered by the hydrate formation. The microcapsules can be designed to release the hydrate inhibitors only when they experience the conditions responsible for the hydrate formation.

In addition the formation of hydrate shell was also observed when water was observed in hydrogel polymer networks, forming hydrogel particles. For the hydrogel decane mixture a lower hydrate fraction was observed and the torque remained stable during the hydrate formation. The addition of 0.5 wt% of a commercial kinetic hydrate inhibitor (Luvicap) to the aqueous phase (with no hydrogel) delayed the hydrate onset time, but several spikes in the torque were observed during the hydrate formation which suggests that segregation and deposition of hydrate particles is occurring in the liquid phase. When Luvicap (0.5 wt%) was incorporated into the hydrogel particles at the same concentration there was an increase in the hydrate onset time and the torque remained stable during the hydrate formation. This study is the first attempt to achieve both kinetic hydrate inhibition and anti-agglomeration using polymer hydrogels. Moreover, the synthesized hydrogel is compatible with monoethylene glycol (MEG) solution and the resulting MEG-hydrogel particles showed the hydrate formation characteristics of an under-inhibited system. Raman spectroscopy data provide evidence that the hydrate shell was formed on the surface of the hydrogels and the shell properties was influenced by the formation and dissociation of the hydrate. These results suggest that the hydrate shell formed on the surface of hydrogel particles which retained the aqueous phase inside the hydrogel core prevents the agglomeration of the hydrate particles.