Thermodynamic Inhibition of CO2–CH4 Gas Hydrates by DESs: Experimental and Computational Study

Abstract

This study presents an experimental and computational investigation of thermodynamic hydrate inhibition behavior of four deep eutectic solvents (DESs) on binary mixed CO₂–CH₄ gas hydrates. The mixtures of hydrogen bond acceptors, tetramethylammonium chloride, and tetrapropylammonium bromide with hydrogen bond donors, glycerol, and ethylene glycol were used to prepare the DESs. The hydrate liquid–vapor equilibrium data for studied systems were measured using an isochoric pressure-search method within the temperature and pressure ranges of (280.51–285.20) K and (3.86–9.48) MPa, respectively. All the investigated DESs inhibited CO₂–CH₄ hydrates, with the inhibition effect increasing with the DES concentration. The experimental results were validated using a computational approach through the analysis of sigma profile data and hydrogen bonding energies obtained for the investigated DESs. The order of the obtained sigma profile results and hydrogen bonding energies was consistent with the experimental results, thereby validating the inhibition ability of the investigated DESs. The hydrogen bonding energies that were obtained in this study correlated well with the inhibition ability of the studied DESs, and this proved the reliability of the computational approach used. Furthermore, this computational approach was successfully used as the prescreening tool to predict the inhibition ability of theoretically formulated DESs without experimental data.