Molecular mechanisms of Poly(N-alkyl methacrylamides)s as Kinetic hydrate inhibitors

Abstract

Kinetic hydrate inhibitors (KHIs) have been used commercially to inhibit gas hydrate plugging in pipelines due to high efficiency and low dosage, and small changes in their molecular structures can significantly influence the inhibition performance, but the mechanisms by which they function remain unclear. Here, we employ the first principle calculation method to study the molecular mechanisms of poly(N-alkyl methacrylamides)s as KHIs, and to reveal the effect of alkyl pendant groups on their inhibition performance. The results show that the inhibition performance of KHIs correlates well with their reactivity such as energy gap and the charge population. KHIs can slow down the diffusive motion of water molecules, retarding the hydrate formation, but also can adsorb onto the incomplete cages of the hydrate surface, driving methane molecules. These two effects are enhanced by increasing the size of the alkyl pendant chain, leading to the better inhibition performance.