Phase Equilibria for Gas Hydrates Formed with Methane or Ethane + Tetra‑n‑Butylphosphonium Bromide + Water

• Published in: Journal of chemical and engineering data 2020-11, Vol.65 (11), p.5428-5436
• Main Authors: Elizalde-Solis, Octavio, Díaz-Ibarra, Jesús A, Mendo-Sánchez, Rubí D, Vega-Díaz, Yedzi B, Pérez-López, Hugo I, Zúñiga-Moreno, Abel
• Format: Article
• Language: English
• ISSN: 0021-9568; 1520-5134
• DOI: 10.1021/acs.jced.0c00564

This paper presents the three-phase (liquid–hydrate–vapor) equilibrium conditions for the binary and ternary systems constituted by methane (CH4) or ethane (C2H6) + tetra-n-butylphosphonium bromide (TBPB, C16H36BrP) + water (H2O). The experiments were carried using the isochoric method within the temperature and pressure ranges of (277.0–293.5) K and (0.65–9.22) MPa, respectively. Phase equilibria for binary systems, CH4 + H2O and C2H6 + H2O, were in good agreement when they were compared with previously reported data. Different mass fractions of aqueous TBPB solutions (w TBPB) in the range of (0.0099–0.20) were studied. For the ternary CH4 + C16H36BrP + H2O system, it was observed that the ionic liquid has promotional effects for the gas hydrate formation in the range of w TBPB = 0.05–0.20 since the three-phase equilibrium curves moved toward low-pressure and high-temperature conditions, which agrees with previous results reported in the literature. From comparison, deviations are within the experimental errors. On the other hand, encouraging results were found only at w TBPB = 0.05 for the C2H6 + C16H36BrP + H2O system, since the ionic liquid exhibited promotional effects; meanwhile, this effect decreased for w TBPB = 0.10 and 0.20, since the liquid–hydrate–vapor equilibrium curves were closer to that of ethane hydrate, and under some conditions (w TBPB = 0.20), the ionic liquid had suppressing capabilities where the equilibrium curve moved to temperatures lower than the corresponding ethane hydrate. Standard uncertainties of temperature and pressure in the three-phase equilibrium measurements were estimated to be u(T) = 0.13 K and u(p) = 0.07 MPa, respectively.