The Influence of Different Types of Amino Acids on the Formation Kinetics of Methane Hydrate

With the development of human society, people's demand for energy is increasing. As a kind of clean fossil energy, natural gas has received more and more attention from the public. With its high safety, low cost, and high storage capacity, solidified natural gas (SNG) has been paid more attention. However, the slow rate of methane hydrate formation severely limits the widespread use of the SNG technology in actual production. The environmentally friendly amino acid additives have been shown to be more promising for promoting methane hydrate formation. However, most of the current studies did not compare the effects of different types of amino acids on methane hydrate formation adequately, which led to the study with limitations. By introducing a new physical quantity, water solubility, and five amino acids (leucine, phenylalanine, methionine, tryptophan, and glutamic acid) which were selected based on different amino acid types, this study discussed the influence of amino acid physical properties on methane hydrate formation. The results showed that each type of amino acid had a significant promotion effect on methane hydrate at low concentrations, but with the increase of concentration, the promotion effect varies. Aliphatic amino acids had a superior performance in terms of methane consumption, while aromatic amino acids possessed a higher promotion efficiency and shorter induction time. We also found an interesting phenomenon that amino acids with high water-solubility produce blocky hydrates and amino acids with low solubility produce tentacle-like hydrates; to the best of our knowledge, this phenomenon was proposed and discussed for the first time by our study. The results contribute to the realization of a safer, more stable, and environmentally friendly SNG technology.