Influences of biofriendly amino acids on methane hydrate formation for natural gas storage and transportation application

Abstract

Solidified natural gas (SNG) is an appealing option for storing natural gas in the form of clathrate hydrates. However, it has some limitations, particularly the slow rate of hydrate formation and the requirement for severe operating conditions. To overcome these constraints, one approach is to introduce promoters into the system to enhance the hydrate formation rate. Amino acids have been reported as kinetic promoters with the potential to improve methane hydrate formation. In this work, the effect of three different side-chain amino acids (L-methionine, L-leucine, and L-valine) on methane hydrate formation and dissociation was investigated in terms of kinetics and morphology. The experiments were conducted at 8 MPa and 277.2 K using a hybrid combinatorial reactor approach at various amino acid concentrations (0.1 to 1.0 wt%). Results showed that the presence of amino acids significantly decreased the induction time and increased the rate of methane hydrate formation. In addition, L-methionine was shown to be the most effective kinetic promoter in this work. However, the final methane uptake and the water to hydrate conversion were the same in all experiments. For all investigated experiments, the morphology of methane hydrate formation exhibited a similar pattern, including methane bubbles and capillary channels. In terms of hydrate dissociation, methane recovery was greater than 95% in all studies, and no foam was generated during dissociation, which is favorable for large-scale applications.