Molecular dynamics simulation of the formation of methane hydrates in the presence of KHIs

Poly(N-vinylpyrrolidone) (PVP) and PVP-A were selected as typical kinetic hydrate inhibitors (KHIs) to simulate the inhibition processes of methane hydrate formation, where PVP-A is obtained by introducing butyl ester groups into the PVP molecule. The results show that KHIs do not significantly delay the formation of the first complete hydrate cage, but inhibit the nucleation of methane hydrate by retarding the formation and growth of the labile clusters and reducing the stability of newly formed hydrate cages. The steric effect and H-bond between inhibitor molecules and the labile clusters are not the main reasons for inhibiting methane hydrate nucleation. The formation of hydrate cages can be effectively inhibited by KHIs during the nucleation stage, but ineffective in the rapid growth stage. Moreover, PVP and PVP-A exhibit dual-functionality, i.e., disturbing H-bonding between water molecules and the movement of methane and water. (c) 2021 Elsevier Ltd. All rights reserved.