Are the amino acids thermodynamic inhibitors or kinetic promoters for carbon dioxide hydrates?

This study deals with the carbon dioxide (CO2) hydrate formation in aqueous solutions, containing 0.5 wt% amino acids (L-valine, L-phenylalanine, L-cysteine, L-methionine and L-threonine) under isochoric conditions. Systematic experiments were conducted in both stirred (300 rpm) and non-stirred configurations. The hydrate formation requires higher sub-cooling than the pure CO2 system. The gas uptake in the hydrates, formed under stirred conditions, in l-val, l-cys and l-met systems is ∼20% higher than the pure system, while in other two (l-phe & l-thr) it is comparable to the pure system. Further, there is no appreciable gas uptake in pure, l-phe and l-thr systems under non-stirred conditions. On the other hand, the gas uptake is higher and faster, similar to stirred conditions, in other three systems, i.e., l-val, l-cys and l-met. Thus, the aqueous solutions consisting of these three amino acids are useful in the CO2 gas capture and storage applications.