Ethanol dehydration by absorption and biodiesel production by reactive distillation: An innovative integrated process

An innovative integrated process of ethanol dehydration and ethylic biodiesel production based on absorption and reactive distillation processes was demonstrated by experimental validated simulation and optimization using Aspen Plus (R) and Statistica (R) software, respectively. Glycerol, a byproduct of the transesterification of triacylglycerols, was adopted as solvent for ethanol purification. Experimental and simulated results of the absorption process step were compared and showed no significant difference from t-test with 95% of confidence level. The optimal conditions of the processes were obtained using a multivariate analysis. For the absorption process, the optimized parameters were solvent feed stream temperature, T = 27 degrees C; number of stages, N = 6; and solvent-to-feed ratio, S/F = 1.5, 1.4 and 1.0 for ethanol mass fractions on feed stream of 0.8800, 0.9380 and 0.9910. The optimal parameters of the reactive distillation column (RDC) for biodiesel production were ethanol-to-oil molar ratio, MR = 12; N = 6; total reflux ratio; and residence time to number of stages ratio, t/N = 8 min/stage. The integrated process produced anhydrous ethanol with mass purity above 99.9%, oil conversion (X-oil) above 99%, and biodiesel yield of 98%. Moreover, X-oil > 96.5% was also obtained for a lower value of MR = 7 adopting t/N = 8 min/stage. Finally, the integrated process proved to be a potential economically attractive technology for ethylic biodiesel production, since reactive distillation and absorption columns were coupled based on the concept of process intensification.