Apparent and Partial Molar Volumes at Infinite Dilution and Solid–Liquid Equilibria of Dibenzothiophene + Alkane Systems

Abstract

Densities of binary mixtures of dibenzothiophene (DBT), 4-methyl-dibenzothiophene (4-MDBT), or 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) with alkanes were measured at T = (298.2 and 313.2) K. Apparent molar volumes Vϕ and partial molar volume at infinite dilution V̅∞ of solutes were obtained, respectively, by experiments and by fitting Vϕ data to the Redlich–Meyer equation. V̅∞ increases with the solvent chain length for DBT solutions in linear alkanes, reaching a limiting value of 149.5 cm3·mol–1 at 298.2 K; the alkylation of the DBT molecule in positions 4 and 6 also increases V̅∞. The infinite dilution transference volume ΔV̅tr∞ from cyclohexane to n-hexane is −10 cm3·mol–1 at T = 298.2 K, and from iso-octane to n-octane the transference volumes are (1.4 and 4.3) cm3·mol–1 at T = (298.2 and 313.2) K, respectively. Solid–liquid equilibrium data for the same binary mixtures were determined. At 298.2 K, the maximum solubility of DBT in linear alkanes increases with solvent chain length, is greater in cyclohexane than in n-hexane, and is lower in iso-octane than in n-octane. For studied solutes, the maximum solubility in n-dodecane has the following order: 4,6-DMDBT < DBT < 4-MDBT.