Molecular insights into the dissociation of carbon dioxide hydrates in the presence of an ionic liquid, [BMIM][PF6

Abstract

Methane production from hydrate reservoirs using combined CO2and chemical inhibitor injection is a potential method for simultaneous methane recovery and CO2sequestration. Molecular dynamics simulations have been performed to study the dissociation of CO2hydrates in the presence and absence of the ionic liquid, viz., [BMIM][PF6], at 250, 255 and 260 K and pressures ranging from 20 to 60 bar. Effect of [BMIM][PF6] on hydrate thickness has been demonstrated to be not significant by hydrogen bonding and order parameter analyses. Local number density profiles of guest and host molecules show that in presence of this ionic liquid, deviation from hydrate-like behaviour is less than in its absence. This is due to preferential association of CO2with [PF6]- anion. The asymmetry in the density profiles of CO2 and H2O brings out the role of filled and empty partial cages at the interfaces on hydrate dissociation in the presence of [BMIM][PF6].