Amino acids as kinetic inhibitors for tetrahydrofuran hydrate formation: Experimental study and kinetic modeling

In this work, a series of natural amino acids which are environmentally friendly and biodegradable have been tested as hydrate crystal growth kinetics inhibitors for THF (tetrahydrofuran) hydrate formation. Also the thermodynamic natural path has been used for modeling of the hydrate formation rate in a constant volume process. The used amino acids consist of glycine and l-leucine at varying concentrations (0.05–1.5 wt%) and the experiments have been conducted in a batch reactor under atmospheric pressure, with and without the presence of acetone. Induction time and equilibrium temperature of hydrate formation have been measured and compared. Amino acids with lower hydrophobicity have been found to be better KHIs to delay nucleation and reduce growth. The results also have shown that glycine has better inhibition performance than l-leucine because of lower hydrophobicity. While, it has been known when acetone is present, inhibition performance of amino acids improves and l-leucine is also more suitable than glycine, because of its nonpolar side chain and insolubility in acetone. The results of modeling show that there is good agreement between model prediction and experimental data with average error of 0.9% and this model can well predict constant volume experimental data of THF hydrate formation in the presence of amino acids.