Abstract
Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.
Highlights
− CH2C3H3N2 − 3.2 Basic significant issue for the utilization of KHIs is the prediction of when gas hydrates will nucleate, and how quickly they will grow
Our recent study proposed that the KHI abilities of some hydrophobic amino acids with respect to CO2 hydrate inhibition are attributed to the perturbation of the structure of the surrounding water[24], but no experimental evidence for this proposal has yet been reported
The findings of this study provide strong experimental evidence in support of the hypothesis that perturbation plays a critical role in the inhibition of gas hydrate formation
Summary
− CH2C3H3N2 − 3.2 Basic significant issue for the utilization of KHIs is the prediction of when gas hydrates will nucleate, and how quickly they will grow. Several more recent studies have proposed that perturbation of the structure of liquid water by KHIs is another mechanism that can be used to interpret gas hydrate inhibition phenomena[12,15]. Such perturbation is a universal phenomenon in which a solute dissolved in water induces changes in the structure of water[20,21,22,23]. Our recent study proposed that the KHI abilities of some hydrophobic amino acids with respect to CO2 hydrate inhibition are attributed to the perturbation of the structure of the surrounding water[24], but no experimental evidence for this proposal has yet been reported. The findings of this study provide strong experimental evidence in support of the hypothesis that perturbation plays a critical role in the inhibition of gas hydrate formation
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