Experimental and Modeling Study of Hydrate Phase Equilibria for CO2-Containing Hexadecane Mixtures in Pure Water and Ethanol–Water Solutions

In this work, we developed a model capable of representing experimental hydrate-phase equilibria data for mixtures containing hexadecane in pure water and in ethanol–water solutions, yielding an average absolute percentage deviation (AAPD) of 0.6% and a maximum absolute percentage deviation (MAPD) of 1.8%. Experimental determinations of the hydrate phase equilibria data of mixtures containing hexadecane with and without the presence of a thermodynamic inhibitor (ethanol) were carried out and represented with the proposed model. The nonvisual isochoric method by pressure search was used to determine hydrate phase equilibrium data over the temperature ranges of (269.4 to 277.7) K and pressure ranges of (1.3 to 3.1) MPa at a fixed hexadecane mass fraction composition (w_C16H34 = 0.1) and several ethanol mass fractions (w_C2H6O = 0.05, 0.10, 0.15). Uncertainty analysis was performed, yielding combined uncertainties of 0.14 K and 0.02 MPa for temperature and pressure, respectively, and a relative standard uncertainty of 0.0016 for mass fraction. Prior to the measurements, the viability of the experimental technique was assessed by comparing international literature (pure CO₂ hydrate phase equilibrium data) with data obtained using our equipment, thus showing good agreement. A thermodynamic consistency test was performed to verify the reliability of the experimental data involving ethanol.