Effect of Biofriendly Amino Acids on the Kinetics of Methane Hydrate Formation and Dissociation

Solidified natural gas (SNG) is a promising option to store [GRAPHIC] natural gas in the form of clathrate hydrates because of several benefits offered that include high degree of safety, eco-friendliness, high volumetric storage capacity, and the relative ease of gas recovery. Environmentally benign amino acids have been reported as promising kinetic promoters for enhancing methane hydrate formation. In this work, we examine in detail the effect of three different types of amino acids-tryptophan (nonpolar, hydrophobic amino acid with aromatic side chain), histidine (polar, basic amino acid with aromatic side chain), and arginine (polar, basic amino acid with aliphatic side chain)-on the kinetics of methane hydrate formation. The effect of amino acid concentration on the hydrate formation kinetics was investigated in two reactor configurations, namely, stirred and unstirred tank reactors. Amongst the amino acids studied, the best kinetic promotion for methane hydrate formation (in both stirred and unstirred reactor configurations) was achieved by tryptophan. The optimal concentration for best kinetic promotion of methane hydrate formation varies with the amino acid for same operating conditions. It may be inferred that the presence of an aromatic side chain and hydrophobic nature resulted in a better enhancement of methane hydrate formation.