PC-SAFT/UNIQUAC model assesses formation condition of methane hydrate in the presence of imidazolium-based ionic liquid systems

Ionic Liquids as Gas Hydrate Thermodynamic Inhibitors

“…Experimental and PVTSim predicted pure water hydrate phase equilibrium temperatures vary with pressure in IL hydrate phase behavior related to the literature. ,,,,, …”

“…The 41 articles studied about 247 IL systems at varying concentrations (up to 50 wt %) in different gas systems and/or mixed/synergistic studies of ILs, commercial inhibitors (MeOH, EtOH, etc. ), and amino acids (glycine). ,, However, 28 out of the 41 articles were published post the last review on ILs as gas hydrate inhibitors by Tariq et al The 28 articles consist of 163 IL systems with the methane hydrate phase boundary being the most studied. ,,,,,− Followed by CO 2 ,, and mixed CH 4 + CO 2 systems, , other authors have also studied the effect of ILs on natural gas hydrate compositions. , Generally, two main types of methods and apparatuses are used to determine the hydrate phase boundary conditions of ILs. The widely used method is the isochoric pressure search technique ,,,,,− or the T-cycle method; ,,, this method is mostly used in high-pressure autoclave cells, ,,,, rocking cells, ,, and hydreval .…”

“…The variation of the pure water data in the literature might be due to the type of systems used for the testing (whether deionized water, distilled water, or tap water). The root-mean-square error (RMSE) in the measurement of the hydrate phase behavior data for pure water systems in the literature ,,,,, is 1.631 with an R 2 of 0.74 as shown in Figure .…”

“…However, the model predictions are more accurate at lower concentrations. The models overpredict the hydrate phase behaviors of ILs at concentrations above 30 wt % . Generally, the modeling of hydrate phase behavior in ILs is available for CH 4 and CO 2 hydrates with acceptable error margins.…”

“…For example, Chu et al 39 reported the average depression temperature for [EMIM][Cl] as 1.091 K at 10 wt %, while Long et al 29 and Richard and Adidharma 43 reported 1.886 and 1.66 K, respectively, representing a deviation of 52%−73%. Also, Long et al 29 reported a temperature depression for [EMIM]-[Ac] as 1.902 K, while Zare et al 41 reported 1.525 K, representing about a 24% hydrate inhibition impact increase reported by Long et al 29 compared to Zare et al 41 This data measurement inconsistency or error affects correlations and data analysis collectively for model development and IL hydrate inhibition performance comparisons. 87 The enthalpy of dissociation represents the amount of heat needed to dissociate a mole of gas molecules from a hydrate crystal, with a reaction formula as…”