Effects of Hydrophobic and Hydrophilic Graphene Nanoflakes on Methane Hydrate Kinetics

Abstract

Gas hydrate technologies have steadily gained interest in several industries for their potential use in natural gas transport and carbon dioxide sequestration applications. To further develop these emerging technologies, significant focus has been placed on additives, and particularly nanoparticles, which optimize their efficiencies. The addition of materials such as graphene nanoflakes (GNFs) has previously been proven to enhance the production of methane hydrates and other hydrate systems. In this study, the growth rates of methane hydrates were measured in the presence of both hydrophobic (as-produced) and hydrophilic (plasma-functionalized) GNFs at 2 °C and 4646 kPa. The effect of GNF loading in the aqueous phase for both types was also determined. Small-scale agglomeration limited the growth rate enhancement effect of hydrophobic GNFs at low concentrations of around 0.5 ppm while significantly increasing the formation kinetics by about 101% at concentrations of 5 ppm. At even higher concentrations (10 ppm), the performance decreased due to large-scale agglomeration. Enhancement rose rapidly at low concentrations (0.1–1 ppm) of hydrophilic GNFs, peaking at about 288% before dropping to around 215% at 5 ppm due to mean free path limitations then rising again as surface area increased.