Enhanced hydrate formation by natural-like hydrophobic side chain amino acids at ambient temperature: A kinetics and morphology investigation

Abstract

Application of amino acids to copromote methane hydrate formation with tetrahydrofuran (THF) and their effects on the dissociation were investigated at room temperature. Hydrophobic side chain amino acids (valine, leucine, and methionine) were experimented together with 5.56 mol% THF on the hydrate formation kinetics and morphology at 293.2 K and 8 MPa in an unstirred reactor. Results show that all hydrophobic side chain amino acids affected the hydrate formation kinetics by increasing the formation rate at the same extent as surfactants. In addition, the presence of amino acids resulted in almost five times higher formation rate than with only 5.56 mol% THF. However, there were no significant difference hydrate formation rate with different amino acid concentrations. Surprisingly, the formation with certain hydrophobic side chain amino acids, leucine and methionine, showed multiple-step hydrate growth profiles, which resulted in the high methane uptake as compared to 5.56 mol% THF. The hydrate formation morphology in the presence of hydrophobic side chain amino acids illustrated different hydrate growth patterns from the THF solution and was totally different for each of the amino acid. Moreover, the presence of hydrophobic side chain amino acid did not affect the methane hydrate dissociation.