Deep Eutectic solvents Applicability in Oil and Gas Processing fields for CO 2 Control

Acidity Scale in a Choline Chloride- and Ethylene Glycol-Based Deep Eutectic Solvent and Its Implication on Carbon Dioxide Absorption

An equilibrium acidity (pK_a) scale that comprises 16 Brönsted organic acids, including phenols, carboxylic acids, azoles, and phenylmalononitriles, was established in a choline chloride/EG-based deep eutectic solvent (DES) ([Ch][Cl]:2EG) by ultraviolet-visible (UV-Vis) spectroscopic methods. The established acidity scale spans about 6 pK units in the DES, which is similar to that for these acids in water. The acidity comparisons and linear correlations between the DES and other solvents show that the solvent property of [Ch][Cl]:2EG is quite different from those of amphiphilic protic and dipolar aprotic molecular solvents. The carbon dioxide absorption capabilities as well as apparent absorption kinetics for a series of anion-functionalized DESs ([Ch][X]:2EG) were measured, and the results show that the basicity of comprising anion [X] of choline salt is essential for the maximum carbon dioxide absorption capacity, i.e., a stronger basicity leads to a greater absorption capacity. The possible absorption mechanisms for carbon dioxide absorption in these DESs were also discussed based on the spectroscopic evidence.

Experimental investigation and modelling of synergistic thermodynamic inhibition of Diethylene Glycol and glycine mixture on CO2 gas hydrates

In this experimental and modelling study, Diethylene glycol (DEG) and Glycine (Gly) mixtures are introduced to hinder carbon dioxide hydrate formation by pushing the phase boundaries on the lower temperature side. The mixture of DEG and Gly with the ratio of 1:1 is experimented at 15, 10, and 5 wt% concentrations and the pressure vary from 2.5 to 4.0 MPa. The T-cycle method is employed to assess the effect of the studied blends on the CO₂ hydrate by evaluating the hydrate dissociation temperature. Varied compositions of pure DEG and Gly as well as their mixtures are used to compute the synergistic effect. The studied system's thermodynamic hydrate inhibition (THI) influence is a concentration-driven phenomenon. Higher concentration can shift the hydrate liquid vapor equilibrium (HLVE) curve to lower temperatures and high-pressure regions. The outcomes depict that mixture of DEG and Gly at 15 wt%. Shows comparatively better results than the mixtures at 5 and 10 wt%, respectively. The obtained 10 wt% mixture results have also been compared with the conventional hydrate inhibitors and other THIs systems and provide a significant hydrate average suppression (ΔT) of 2.4 K. Furthermore, the freezing point-based Dickens and Quint Hunt model was also applied to predict the HLVE data of CO₂ hydrates and satisfactory agreement found with maximum mean absolute error (MAE) of 0.498 K. A better inhibitory performance was seen when diethylene glycol and glycine were combined, demonstrating the potential of amino acids as synergistic inhibitors in the exploitation of hydrates, transportation of oil and gas, and flow assurance.