Phase equilibrium measurement and modeling approach to quaternary ammonium salts with and without monoethylene glycol for carbon dioxide hydrates

This experimental work evaluates the thermodynamic hydrate inhibition behavior of three quaternary ammonium salts (QAS) namely tetra ethyl ammonium iodide (TEAI), tetra methyl ammonium bromide (TMAB) and tetraethyl ammonium bromide (TEAB) for carbon dioxide (CO ₂ ) hydrates. The Hydrate Liquid Vapor Equilibrium (HLVE) data for CO ₂ are evaluated through T-cycle method at different temperature (275–283 K) and pressure (2.0–3.50 MPa) conditions in the presence and absence of 5 and 10 wt% aqueous QAS and QAS + MEG solutions. Among all the considered compounds, the inhibition effect of TMAB was found to be the best in pure as well as in mixture with MEG therefore, extended further for 1 wt% also along with 5 and 10 wt%. The inhibition effect including average suppression temperature (ΔŦ) and dissociation enthalpies (ΔH _diss ) for hydrate formation are also calculated for the systems taken into consideration. Additionally, a thermodynamic model offered by Dickens and Quinby-Hunt has been used for the prediction of HLVE temperatures of CO ₂ gas for the considered systems. The results obtained from experimental and modeling data indicate that pure QAS and their mixtures with MEG perform efficiently as thermodynamic hydrate inhibitor for CO ₂ gas. Therefore, the use of these compounds in thermodynamic inhibition of CO ₂ hydrates systems can lead towards their application in flow assurance strategies.