Liquid–liquid equilibrium (LLE) for the biodiesel + glycerol + alcohol system is essential for the design, operation, process optimization, and economic evaluation of a biodiesel production plant. In this work, methyl and ethyl safflower biodiesels were produced from safflower (Carthamus tinctorius L.) seed oil. New LLE experimental datasets were obtained for the glycerol (1) + methanol/ethanol (2) + methyl/ethyl safflower biodiesel (3) systems at 298.15 and 318.15 K under atmospheric pressure. Binodal curves, tie-lines, distribution coefficients, and selectivity were determined. Data reliability was confirmed using the Othmer–Tobias correlation. LLE data were correlated with the UNIQUAC model satisfactorily, with deviations between 0.70 and 2.79% for all studied systems. The consistency of the estimated binary interaction parameters of the UNIQUAC model was ascertained. Finally, through process simulations in Aspen Hysys software, it was verified that the UNIFAC LLE model, along with the UNIQUAC model, can also be used adequately to describe the liquid–liquid behavior of biodiesel separators, provided that the biodiesel composition is accurately known.

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Although physicochemical properties are essential to developing new industrial ionic liquid (IL) applications, experimental data must be obtained, especially under high-pressure operational conditions. Therefore, density data were measured for three commercial ILs: methyltrioctylammonium bis(trifluoromethylsulfonyl) imide [(C8)3C1N][NTf2]; 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl) imide [C3C1Pip][NTf2]; and 1-butylpyridinium bis(trifluoromethylsulfonyl) imide [C5Py][NTf2] at high-pressure and wide temperature ranges [P = (0.2 to 100.0) MPa and T = (298.15 to 398.15) K] by the intermediate of a tube vibrating method. The operational range was chosen because it could cover many industrial applications. The structural interaction between the IL cation and the anion is significant in volumetric behavior. It was observed that the density increases in the following order: [C5Py][NTf2] > [C3C1Pip][NTf2] > [(C8)3C1N][NTf2]. The Tammann–Tait equation was used to evaluate the influence of pressure and temperature on density, showing an average absolute relative deviation (%AARD) of less than 0.032% compared to experimental data. From these data, the isothermal compressibility (κT), isobaric expansivity (αp), thermal pressure coefficient (γv), and internal pressure (P i) were calculated. Additionally, IL density was estimated using five different group contribution methods reported in the literature, with better results obtained for Gardas and Coutinho and Paduszyński and Domańska.

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