Solubility of menadione and dichlone in supercritical carbon dioxide

• Published in: Fluid phase equilibria Vol. 423; pp. 84 - 92
• Main Authors: Reveco-Chilla, Andrea G., Cabrera, Adolfo L., de la Fuente, Juan C., Zacconi, Flavia C., del Valle, José M., Valenzuela, Loreto M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-2016
• Subjects: Carbon dioxide; Chrastil's equation; Density; Detectors; Dichlone; Menadione; Olefins; Polarity; Precipitation (chemistry); Solubility; Supercritical CO2; Temperature; Thermodynamic consistency; Thermodynamic consistency; Chrastil's equation; Menadione; Supercritical CO2; Dichlone; Solubility
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/j.fluid.2016.04.001

This work reports the solubility of menadione (2-methyl-1,4-naphthoquinone) and dichlone (2,3-dichloro-1,4-naphthoquinone) in SuperCritical (SC) carbon dioxide (CO2) at 313, 323, and 333 K and (7.1–33) MPa. A Gibbs-Duhem test was applied to assess the thermodynamic consistency of experimental data using the Peng-Robinson equation of state with Wong-Sandler mixing rule to represent the solubility, and the non-random two-liquid model to compute Gibbs' excess free energy. In addition, the solubility of menadione and dichlone in SC-CO2 at 313 K and 9.5 MPa, a solubility correction by a change in the density of SC-CO2 as compared to this reference condition (580 kg/m3), and a solubility correction by a change in absolute temperature compared to 313 K were estimated using Chrastil's equation. The solubility of menadione at the reference conditions was 8.3 times higher than that of dichlone (3095 versus 375 mg kg−1 solute/CO2). However, both CO2 density and system absolute temperature had anomalously smaller effects on the solubility of menadione than dichlone, so that menadione was only 4.2 time more soluble in SC-CO2 than dichlone at the extreme conditions of 333 K and 33 MPa (3460 versus 831 mg kg−1 solute/CO2) for which ρ = 851.1 kg/m3. The anomalous behavior of the solubility of menadione in SC-CO2 was imputed to experimental difficulties (solute precipitation resulting in tube blocking, saturation of HPLC detector signal) associated with high solubility values (≥0.5 × 10−3 M fraction) that may have been also responsible for thermodynamically inconsistent results reported by others in literature. We compared the solubilities in SC-CO2 of menadione and dichlone with those for several solutes sharing the same molecule core (1,4-naphthoquinone) and concluded they are negatively impacted by polar and non-polar substituents, but that these negative steric and polarity effects could be partially compensated by a non-polar olefin substituent, or ameliorated by distancing substitutions from the carbonyl groups.
•Measured solubility of menadione and dichlone in CO2 was thermodynamically consistent.•Solubility of menadione and dichlone in CO2 was best-fitted to Chrastil's model.•Solubility of menadione in CO2 was minimally affected by system temperature and pressure.•Substituents on 1,4-naphtoquinone derivatives have large effects on their solubility in CO2.