Imaging Biologically-Based Clathrate Hydrate Inhibitors
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The unscheduled formation of gas hydrate plugs in oil and gas pipelines, which can lead to serious mechanical and personnel damage, is a problematic issue in the petroleum industry. Traditionally, thermodynamic inhibitors such as methanol have been used to control the formation of gas hydrates, but due to the large expenses and ecological risks associated with its use there is increased interest in the use of alternative hydrate inhibitors. They include kinetic inhibitors (KIs) and antiagglomerants (AAs) and as their names imply, function by interfering with the kinetics of hydrate formation and hydrate agglomeration. Recently, antifreeze proteins (AFPs) have shown to inhibit hydrates and have been proposed as hydrate inhibitors. Normally, AFPs function to protect the tissues of various organisms during freezing conditions. Initially they were found in polar fish, and were later recognized in insects, plants and microorganisms. AFPs are thought to function by lowering the freezing point of water through an adsorption-inhibition mechanism. This thesis has shown that antifreeze proteins (AFPs) are able to modify the crystal morphologies of structure II (sII) tetrahydrofuran (THF) similarly to the KI poly-N-vinylpyrrolidone (PVP) by adhering to the hydrate surface and inhibiting crystal growth. The AFPs were also tested on a high-pressure sII methane/ethane/propane hydrate and proved to have superior hydrate inhibition to PVP. Yet, the expense of purifying AFPs makes them impractical for industrial purposes, thus investigations into the use of cold-adapted bacteria as hydrate inhibitors proved that isolates capable of adsorbing to THF hydrate showed the most effective THF hydrate inhibition. These findings suggest a potential for the future development of biologically-based hydrate inhibitors.