Downstream Processing of 1,3-propanediol: Thermodynamic Analysis and Simulation

Abstract

In recent years, as a result of the transition from the “hydrocarbon economy” to the “carbohydrate economy”, the chemical industry has accepted the fermentation process as an economical path for producing many compounds. 1,3-propanediol is one of them, since it is one of the oldest known fermentation products that was reliably identified in 1881 in glycerol fermentation. This work focuses on the separation of the 1,3-propanediol+water mixture that, to the authors’ knowledge, is poorly investigated in the literature. This separation is encountered in the microbial production of 1,3-propanediol, as well as in the downstream processing of the aqueous mixture obtained in the production of biofuels in which heavy by-products are often present. In particular, the system comprising water+ 1,3-propanediol+glycerol has been considered representative of the fermentation broth to be subject to further separation. Since no parameters of the Non-Random Two-Liquid (NRTL) model are available in the Aspen Plus® V11 process simulator for two of the three pairs of compounds involved in this system, a thermodynamic analysis has been performed to properly calibrate such a model for a reliable representation of the Vapour-Liquid Equilibrium data that have been collected from the literature. The resulting thermodynamic model has been used in the Aspen Plus® V11 process simulator for studying the recovery and purification of 1,3-propanediol produced by glycerol fermentation, paying attention not only to its purity but also to the quality of the removed water (maximum theoretical oxygen demand of 10 gO2/l) in order to avoid a water treatment step.