Morphology Study of Structure I Methane Hydrate Formation and Decomposition of Water Droplets in the Presence of Biological and Polymeric Kinetic Inhibitors

The effect of kinetic inhibitors on the morphology of methane structure I hydrate was observed using a high pressure sapphire crystallizer. Two kinetic inhibitors were studied, poly(VP/VC), a lactam ring copolymer of polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), and type-I antifreeze protein (AFP). The experiments were performed at temperatures ranging from 274.2 to 275.2 K and pressures from 4200 to 7200 kPa. The experiments were conducted on three droplets simultaneously (a pure water droplet, a droplet containing 0.01 mol/m³ poly(VP/VC), and a droplet containing 0.01 mol/m³ AFP). The morphology and translucency were compared and found to vary significantly due to the presence of kinetic inhibitors. Hydrates formed under a higher driving force had dendrite formation on all but the AFP droplet. Low driving force experiments produced noticeably smoother surfaces on all droplets compared to high driving force experiments. Translucency also varied with AFP and poly(VP/VC) having the appearance of thinner films. Hydrate decomposition was also studied. The pure water droplet had the fastest rate of decomposition, followed by the droplet containing the AFP. The poly(VP/VC) droplet has a visible hydrate skin for a substantially longer period of time than the pure water and the AFP droplet.