Thermodynamic Study on Proline Inhibition of Methane Hydrate Formation

Gas hydrates are crystalline compounds formed at certain conditions. Methane hydrate can block the pipeline and gathering production equipment, resulting in unpredictable damage and economic losses. Injecting kinetic hydrate inhibitors (KHIs) and thermodynamic inhibitors (TIs) is an effective way to inhibite the formation of gas hydrate. However, most of conventional hydrate inhibitors have major drawbacks such as serve pollution, poor biodegradability and toxicity[1]. Fortunately, some amino acids (L-valine, L-alanine, glycine), environment-friendly and easily biodegradable, were found with distinctive thermodynamic and kinetic inhibition for the carbon dioxide hydrate formation[2,3]. Consequently, we applied the amino acids of proline as a thermodynamic inhibitor for methane hydrate in this work. In addition, compared with other amino acids, proline is believed as the most possible osmoprotectant in living systems because of the interaction between proline and water[4]. The experiments of three-phase (liquid-hydrate-vapor) equilibrium conditions for methane hydrate in the presence of 0.2-3.0 mol% proline solution were investigated in the range of 273.15-285.15K. The results show that the phase equilibrium pressure of 3.0mol/L proline solution is 14.03Mpa at 283.14K. It means that proline has excellent thermodynamic inhibility for methane hydrate at high concentration.