In this work, new interesting results were obtained in relation to the dual effects of amino acids on the nucleation and growth rate of hydrate in different systems. Interestingly, some amino acids acted as promoter, while they are known as kinetic hydrate inhibitors. It considers that the hydrophobic and hydrophilic properties of amino acids play a significant role in the inhibition and promotion of hydrate formation when hydrophobic gas molecules (such as ethane, methane and propane) are only present in the system. In this regard, glycine and L-serine (as hydrophobic amino acids) showed a weak inhibitory effect on the growth rate of hydrate in ethane+water and methane+propane+water systems, while L-histidine and L-glutamine (as hydrophilic amino acids) acted as promoters in these systems. On the other hand, a different behavior was observed in the presence of THF (as a hydrophilic hydrate former), such that all the amino acids behaved as inhibitors. The induction time measurements also showed that all the amino acids (except L-glutamine) retard the nucleation, such that the nucleation was more retarded with increasing amino acid hydrophobicity. The performance of amino acids was also compared with SDS and PVP for evaluation of their potential as promoters and inhibitors. Also, the results showed that glycine and L-serine can be useful in the development of new synergists for kinetic hydrate inhibitors.

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