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Presently, gas hydrates are being studied for their potential applications in technologies involving natural gas transportation, carbon dioxide sequestration, and component separation. In order to optimize their use, research has focused on finding hydrate-promoting agents and understanding how they work. One such promoter, multiwall carbon nanotubes (MWNTs), was found to enhance hydrate growth. The current study investigates the effects of adding plasma-functionalized hydrophilic MWNTs and as-produced hydrophobic MWNTs on the dissolution stage of methane hydrate formation. It was found that the addition of the hydrophilic MWNTs increased methane dissolution rates with an increase in MWNT loading. Furthermore, the hydrophobic MWNTs initially enhanced dissolution up until a concentration of 5 ppm, at which point the rates began to return to their nominal values. It was also found that the addition of either type of MWNT did not significantly affect the total number of moles of methane dissolved in the water.

Gas hydrate inhibition is a prime focus of industrial hydrocarbon research as pipeline blockages can be costly and dangerous. Historically, many chemical species have been studied for their effects on the hydrate formation process. One of the most investigated compounds in the kinetic hydrate inhibitor (KHI) category is polyvinylpyrrolidone (PVP). While the effects of PVP on hydrates are well-documented, the mechanism that defines its function is still not completely understood. To obtain further insight into its behavior, bulk liquid samples in a PVP-containing system were extracted at six specific times throughout a methane hydrate formation process. The effect of PVP loading concentration was also investigated. It was found that as time progressed, concentration of PVP in the liquid decreased, suggesting that PVP binds to the surface of growing hydrates. Furthermore, this decrease in concentration was more prevalent in situations where lower initial PVP loadings were used.

In an attempt to mitigate carbon dioxide emissions, new technologies are being proposed that can aid in greenhouse gas sequestration. One such technology involves trapping carbon dioxide in hydrate form. To optimize this process, it is of interest to investigate how the hydrate system behaves in the presence of promoting agents. In this work, the effect of asproduced and amine-functionalized multi-wall carbon nanotubes (MWNTs) on carbon dioxide dissolution and hydrate growth rates was studied. For either type of the MWNTs, the effect on saturation values and dissolution rates was negligible. Under lower concentrations, it was found that both forms of MWNTs enhanced growth, with the functionalized MWNTs performing slightly better. Under higher concentrations, both forms of MWNTs decreased growth rates, because the initial nucleation event was more pronounced and led to heat-and mass-transfer limitations.

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