A design-of-experiments approach to modeling activity coefficients in solvent mixtures: a case study using platinum(ii) acetylacetonate in mixtures of acetone, cyclohexanol, 1,2,3,4-tetrahydronaphthalene and propylene carbonate
2005
Flanagan, Scott C. | Hall, Eric | Bowie, Wade | Fuhs, James W. | Logan, Robbie | Maniei, Farzaneh | Hunt, Andrew
The solubility of platinum(ii) acetylacetonate (Pt(acac)₂) in various solvent mixtures of acetone, cyclohexanol, propylene carbonate and 1,2,3,4-tetrahydronaphthalene (THN) have been determined at 25 °C and 1 atm, using thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). The densities of the saturated solutions were determined by pycnometry. The entropy of fusion and melting point of Pt(acac)₂ were determined by differential scanning calorimetry (DSC) to be 41.4 J mol⁻¹ K⁻¹ and 512.5 K, respectively. From this data, the ideal mole fraction at saturation (xᵢdₑₐₗ) of Pt(acac)₂ was calculated to be 0.0278, which is more than twice the highest reported solubility of that compound. In this effort, mixtures of acetone, propylene carbonate and THN exhibit cosolvency for Pt(acac)₂, with the greatest measured molar solubility of Cₛₐₜ = 0.0675 mol L⁻¹ occurring at the 1 ∶ 1 ∶ 1 v ∶ v ∶ v ratio of these three solvents. A new equation was developed for activity coefficients in solvent mixtures and used to predict ln γ for Pt(acac)₂ to within 3.6% of the measured values. The concept of Intercomponent Mixture Parameters (IMPs) is introduced in relation to Scheffé mixture polynomials as applied to the prediction of activity coefficients in solvent mixtures.
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