Inhibition properties of new amino acids for prevention of hydrate formation in carbon dioxide-water system: Experimental and modeling investigations

In the present work, the effect of new structures of amino acids is studied for prevention of hydrate formation in the carbon dioxide-water system. These amino acids consist of L-proline (as amino acid with nonpolar side chain), L-serine and L-glutamine (as amino acids with polar side chain), and L-histidine (as amino acid with charged side chain). The inhibition effects of these amino acids were compared with glycine, L-threonine, and poly-N-vinylpyrrolidone (PVP). Experiments were performed in the concentration range of 0.5-2 wt.%. Investigation on the experimental results shows that inhibition properties of amino acids in an aqueous solution was due to hydrophobicity, the net charge of amino acid, and electrically charge of the side chain. Based on the experimental results, the ranking of amino acids (to decrease the hydrate growth rate) is as follows: L-histidine > glycine > L-proline ≈ L-serine ≈ L-threonine > L-glutamine, although the inhibition effect of some amino acids is not significant. In addition, the inhibition effects of these amino acids are quantitatively described by the chemical affinity model. The predicted results confirm that some of the applied amino acids decrease CO2 hydrate formation rate.