Valorização da glicerina como solvente da destilação extrativa para separação de azeótropo etanol-água

Abstract

The recovery of by-products like glycerin and cake from oilseeds, resulting in the production of biodiesel, has been the main alternative to make this biofuel competitive compared to petroleum and diesel oil. This alternative can be associated with a beneficial integration of processes, such as use of glycerin as a solvent for separation of ethanol-water mixture in plants alcohol. Thus, the use of glycerin in place of ethylene glycol, a substance of fossil origin was tested. The glycerin eliminates the azeotrope formed by modification of the liquid-vapor equilibrium of ethanol-water mixture, increasing the difference in volatility between these components. To verify the operating conditions suitable for the process of extractive distillation for ethanol dehydration, experiments were performed in laboratory scale, using a central composite rotational design (CCRD). The independent variables were the molar fraction glycerol / water and the degree of vacuum, the latter as a way to avoid thermal decomposition of glycerol into acrolein. The analysis of the response surfaces showed that the molar fraction glycerin / ethanol becomes appropriate than 0.4 and the absolute pressure of the system is adequate around 380 mm Hg. In this way it was possible to obtain a statistical model for simulation and prediction of appropriate conditions to the process for developing a technology that prior actions to preserve the environment.