High-pressure phase behavior of the carbon dioxide-trifluoropropylisobutyl polyhedral oligomeric silsesquioxane binary system

ERTAŞ A., DİLEK HACIHABİBOĞLU Ç.

Journal of Supercritical Fluids, vol.219, 2025 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 219
  • Publication Date: 2025
  • Doi Number: 10.1016/j.supflu.2025.106538
  • Journal Name: Journal of Supercritical Fluids
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, Food Science & Technology Abstracts, INSPEC, Metadex, Civil Engineering Abstracts
  • Keywords: DFT, Gibbs free energy, POSS, PR+COSMOSAC EOS, Solubility
  • Middle East Technical University Affiliated: Yes

Abstract

The solubility of a bifunctional polyhedral oligomeric silsesquioxane, trifluoropropylisobutyl (TFIB) POSS, in supercritical carbon dioxide (scCO2) was investigated. In the temperature and pressure ranges of 308 K to 323 K and 8.8 MPa to 14.5 MPa, respectively, TFIB POSS is soluble in scCO2 up to 2.0 × 10−2 by weight fraction corresponding to 1.0 × 10−3 by mole fraction, which is between the solubility of its monofunctional counterparts, octaisobutyl POSS and octatrifluoropropyl POSS. The study includes the modeling of the TFIB POSS-CO2 binary system phase equilibrium with the density-based semi-empirical equations and Peng Robinson+COSMO segment activity coefficient (PR+COSMOSAC) equation of state (EOS). The prediction of the equation of state has been improved for the cage-structured molecule by introducing new electrostatic and dispersion contributions. While the density-based relations provide better fits to the solubility isotherms, the main advantage of the EOS is its applicability for a priori phase equilibrium predictions for the CO2-POSS systems in the absence of the solute critical properties.