Experimental Measurements, Correlation, and Prediction Models to Study 1-Ethyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid Ternary Mixtures

Volumetric and acoustic properties were obtained using density, ρ₁₂₃, and speed of sound, u₁₂₃, experimental values for ternary systems of {[EMIM][BF₄] (x₁) + acetic acid (x₂) + acetophenone (x₃)} (mix₁) and {[EMIM][BF₄] (x₁) + propionic acid (x₂) + acetophenone (x₃)} (mix₂) at T = (293.15-333.15) K and 0.1 MPa. The observed V_m123^E and Δk_s123 data of the studied ternary mixtures were modeled with a total of 63 evaluated models, which resulted from a sum of each of nine predictive terms (no estimated parameters) with each of seven correlative terms (estimated parameters). The entire model is a correlative model, and if all of the parameters of the correlative term are set to zero, it becomes a predictive model. The ideal number of parameters in the correlation was then approximated using standard deviations (σ). For mix₁, V_m123^E was only negative and Δk_s123 was only positive, while for mix₂ both negative and positive results were found for each property. Also, quantitative results point out that mix₁ is closer to ideal behavior than mix₂. The modeling for mix₂ employed more complex equations, with more parameters, and even so presented worse deviations than for mix₁. These results evidence the effect of one CH₂ in the acid chain on the thermodynamic properties of these mixtures.