Study of liquid-liquid equilibrium aiming at the deodorization of bioglycerol by solvent extraction

Bioglycerol is the main co-product generated in biodiesel production, formed at approximately 10% w/w in relation to the amount of oil used as raw material. Therefore, the industry has been purifying the glycerin phase to obtain bioglycerol at a purity suitable for commercialization. However, purifying the glycerin phase has not proven to be a simple task, as several processes are required to achieve high purities, such as neutralization, decantation, evaporation, vacuum distillation, deodorization at high-temperature and with steam stripping injection, and adsorption on activated carbon. Deodorization, in particular, is carried out at high temperatures, presenting high energy costs and adverse operating conditions, in order to remove short-chain oxygenated compounds. As a result, there is a need to study alternative separation processes that are safer and less costly, such as liquid-liquid extraction. To do so, it is necessary to first determine the liquid-liquid equilibrium (LLE) behavior of the substances using model systems to generate information that will provide the knowledge for future implementation in the industry. Therefore, the aim of this study was to evaluate the liquid-liquid extraction through LLE studies of glycerol (diluent) + ?-valerolactone (solvent) + valeric or propanoic acid (solute) systems at 50°C and (glycerol + H2O, 50% molar) (diluent) + ?-valerolactone + valeric acid at 25°C. The results showed that ?-valerolactone (GVL) was able to extract the solutes from the glycerol-rich phase in all studied systems, with solute distribution coefficients greater than 1 and presenting good solute selectivity, with values greater than 7. For the system containing the glycerol+H2O mixture as a diluent, GVL was even more selective to the solute. The uncertainties of the calculated mass fractions for the first two experimental systems were obtained in the third decimal place and for the system containing water in the diluent, values between the second and third decimal places were obtained. Finally, the LLE compositions were modeled using the NRTL and UNIQUAC and the results indicated that both models were capable of accurately modeling the studied systems, however, for the system with water, thermodynamic modeling needs to be improved. The tested predictive methods (UNIFAC-DMD and COSMO-SAC) failed for the studied systems (AU)