Reactive distillation with pervaporation hybrid configuration for enhanced ethyl levulinate production

Abstract

A hybrid process design based on reactive distillation (RD) combined with pervaporation membrane systems was proposed for the production of ethyl levulinate (LAEE) via esterification. In the proposed hybrid configuration, LAEE is produced from the bottom stream of the RD column while the ethanol/water mixture from the overhead is fed to an additional column. The azeotropic mixture in the overhead of the additional column is separated in the pervaporation unit, and the ethanol-rich stream is recycled to the RD column. An RD-only configuration with excess ethanol reactant was also examined to investigate the benefit of excess ethanol reactant and the azeotrope mixture separation. The proposed RD with pervaporation hybrid configuration provided 61.0% and 71.0% reductions of the total annual cost and energy, respectively, compared to the conventional RD configuration with excess levulinic acid (LA) reactant and 6.0% and 13.0%, respectively, as compared to the conventional RD configuration with excess ethanol reactant. The results demonstrated the advantage of the proposed hybrid RD process using pervaporation for lowering the cost and improving the energy efficiency of LAEE production. Different pervaporation arrangements (such as series and parallel arrangements) were discussed in connection with the two main variables (operating temperature and concentration gradient) affecting the membrane flux. The series arrangement was more suitable for the LAEE hybrid process because the influence of the operating temperature is dominant in this process. Thermal intensification in the RD-pervaporation was also examined for exploring further energy reduction. This thermally coupled RD-pervaporation hybrid configuration provided further reductions in total annual cost and energy by 63.0% and 73.0%, respectively, compared to the conventional RD configuration with excess LA reactant.