Experimental Investigation of the Thermodynamic Effects of Monoethanolamine, Diglycolamine, Triethanolamine, and 2-(Methylamino)ethanol on CO ₂ Hydrate Formation

Controlling the formation of carbon dioxide (CO2) hydrate is crucial for CO2 capture, transportation, and storage. Understanding the effects of additives on CO2 hydrate formation is essential for selecting suitable chemicals to ensure flow assurance. This study presents new experimental data on the effects of alkanolamine additives: monoethanolamine (MEA), diglycolamine (DGA), triethanolamine (TEA), and 2-(methylamino)ethanol (MAE) on CO2 hydrate formation. Equilibrium dissociation temperatures and pressures were measured using isochoric and temperature-cycling methods over a temperature range of 272–281 K, pressure range of 1.7–3.4 MPa, and additive concentrations of 5 and 10 wt %. All additives thermodynamically inhibited CO2 hydrate formation, with MEA exhibiting the strongest inhibitory effect. Compared to other thermodynamic hydrate inhibitors (THIs), including amines, alcohols, ionic liquids, and alcohol amine mixtures reported in the literature, MEA demonstrated the highest inhibition strength. Additionally, the Clausius–Clapeyron equation was used to speculate on CO2 hydrate structures, suggesting that the sI CO2 hydrate is generated in the presence of each additive. Furthermore, the Østergaard–Masoudi–Tohidi–Danesh–Todd (ØMTDT) equation was employed to effectively correlate the equilibrium dissociation data of CO2 hydrates in the presence of these additives.