New Promoters Derived from Amino Acids and Citric Acid for the Efficient Storage of Methane As Gas Hydrates

In this work, we studied new citric acid derivatives of some amino acids, which improve the formation kinetics of methane hydrate at low concentrations. These compounds hold potential as efficient promoters of hydrate formation with the advantage that they do not foam upon release of the gas from the hydrates. The modification of the amino acids by citric acid enhances their efficiency as kinetic promoters of methane hydrate formation relative to the unmodified amino acids. This leads to shortening of the induction time and time to achieve maximal conversion of water to hydrate as well as to enhancing the methane uptake. The amide of norleucine and citric acid enhances the conversion of water to hydrate relative to the unmodified amino acid. For 0.05 mass % solutions, the conversion is increased by 5% to 89%, which corresponds to the absorption of 0.148 mole of methane per 1 mole of water. This modification of norleucine also leads to shortening of the induction time by a factor of 1.6 and of the time to reach maximal conversion by a factor of 2.8 relative to unmodified norleucine.