Molecular Dynamics Simulations as a Tool for the Selection of Candidates for Kinetic Hydrate Inhibitors

摘要

The possible effects of tour different functional groups that operate in kinetic hydrate inhibitors have been examined by molecular dynamics simulations, with focus on their possible effects at the hydrate surface. New simulations for models of PVCAP (Poly(N-vinylprolactam)) and another functional group that takes part in the inhibitor VC-713 are presented and discussed in relation to previously published results for PVP (Poly(N-vinylpyrrolidine)). A modified version of the PVCAP polymer is also suggested. In addition a monomer of the polymer chitosan is also simulated. Simulated results are discussed in relation to observations from experiments on real systems. For the model systems in this study we find that PVPCAP has more favourable interaction properties with hydrate water than PVP and should, according to the simulations presented in this paper, have better properties as a kinetic hydrate inhibitor than PVP. A modified version of the PVP monomer, where a hydroxyl group is added to the ring, increases the attachment to the hydrate surface further. In VC-713 a third group is alternating with PVP monomers and PVCAP monomers as the functional groups attached to the paraffinic backbone. The simulations of this particular group indicate favourable interactions between hydrate water and for the limited monomer simulated in this study, practically all coloumbic interaction between this group and water is devoted to connections with the hydrate crystal. A monomer of chitosan is also simulated and although this monomer has strong attachment energy to the hydrate surface it also has very favourable interactions with liquid water. It is, therefore, somewhat unclear whether this polymer would have a sufficient attachment to a hydrate in the competition with a liquid water environment.