Clathrate Hydrates of Greenhouse Gases in the Presence of Natural Amino Acids: Storage, Transportation and Separation Applications

Storage of greenhouse gases in the form of gas hydrates is attractive and is being pursued rigorously in recent times.  However, slow formation rate and inefficient water to hydrate conversion are the main hindering factors. In this report, we examine the role of two amino acids (0.5wt%), l-methionine (l-met) and l-phenylalanine (l-phe) on the formation of gas hydrates using methane (CH4), carbon dioxide (CO2) and their mixtures as guest molecules. Experiments are conducted under non-stirred and isochoric configurations. The hydrate conversion efficiency of both amino acids is identical for hydrates formed with CH4 and mixture of (CO2+CH4). However, the hydrate conversion is significantly less in CO2 hydrates in l-phe system. Addition of amino acids to the water dramatically improved the kinetics of hydrate formation and 90% of maximum gas uptake in hydrate phase occurred in less than an hour. The water to hydrate conversion is also very efficient (> 85%) in the presence of amino acids. Therefore, the amino acids containing systems are suitable for storing both CH4 and CO2 gases. The gas hydrates were characterised using powder x-ray diffraction (XRD) and Raman spectroscopic measurements. These measurements indicate the formation of sI hydrates and encasing of gas molecules as guests.

Enclathration of greenhouse gas molecules in hydrates.

Amount of captured gas with 0.5 wt% l-methionine (l-met) (bars with Sparse pattern) and l-phenylalanine (l-phe) (filled bars) in CO2 and CH4 gas mixtures. All the experiments were with initial gas pressure ~3300 kPa. 

Ref: PSR Prasad and BS Kiran, Scientific Reports | (2018) 8:8560 | DOI:10.1038/s41598-018-26916-1