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

- This work illustrates the inhibition and decomposition mechanism of gas hydrate in presence of polyvinylpyrrolidone at molecular level.
- Free energy of binding of polyvinylpyrrolidone with hydrate surface was calculated.
- Higher molecular weight of polyvinylpyrrolidone has greater binding affinity with gas hydrate surface.
- Enhanced decomposition kinetics was observed in the presence of polyvinylpyrrolidone polymer.

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 (F4) 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.

Graphical AbstractImages shows the encagement of atoms of 16-mer PVP inside water which are cages close to hydrate surface and graph is PMF (free energy) profiles of all three systems.160