Effect of polyvinylpyrrolidone at methane hydrate-liquid water interface. Application in flow assurance and natural gas hydrate exploitation

Polyvinylpyrrolidone (PVP) is one of the most studied low dosages hydrate inhibitor (LDHI), while its hydrate inhibiting effect is well known, its surface active properties by which PVP molecules alters the hydrate-liquid water interface has not been understood properly. In the present work, influence of PVP molecules at the hydrate-liquid water interface was studied at molecular level using molecular dynamics (MD) simulation. In addition, impact of various molecular weights (or chain length) of PVP molecules was also investigated. The force field parameters for PVP monomer (F-4) and polymers were developed and validated against PVP physical properties. The free energy of binding of PVP with methane hydrate and methane hydrate decomposition kinetics was studied in presence of PVP at hydrate-water interface. Structural properties of hydrate were analyzed using four body order parameter and mutually coordinated guest order parameter (MCG-OP). The decomposition rate of methane hydrate in presence of PVP molecules (in bulk water near hydrate interface) was studied, it was observed that PVP polymer changes the surface properties of hydrate and enhances the hydrate decomposition rate. (C) 2016 Elsevier Ltd. All rights reserved.