Experimental and DFT Approach on the Determination of Natural Gas Hydrate Equilibrium with the Use of Excess N2 and Choline Chloride Ionic Liquid as an Inhibitor

This work presents the characterization of hydrate-forming conditions of a Qatari natural gas-type mixture, QNG-S1, obtained using two different experimental methods, namely, a benchtop reactor and a gas hydrate autoclave. The obtained experimental results were found to be in agreement with each other. Another mixture in which the QNG-S1 sample was diluted with nitrogen (N-2) in a 1:1 ratio was also characterized for hydrate dissociation conditions using a rocking cell apparatus only. The thermodynamic hydrate inhibition effect of a biocompatible ionic liquid, choline chloride (ChCl), was tested for both QNG-S1 and QNG-S1+N-2 at two concentrations (1 and 5 wt %) using the rocking cell apparatus. It was found that the ChCl shows a typical classical thermodynamic inhibitor behavior for both tested mixtures QNG-S1 and QNG-S1+N-2 by shifting the hydrate equilibrium toward lower temperature and higher pressure. Likewise, the interaction between ChCl and model hydrate cages was analyzed using density functional theory to characterize the ionic liquid inhibition mechanism at the nanoscopic level.