Semicontinuous reactive extraction and reactive distillation

A novel semicontinuous process that alternates between reactive extraction and reactive distillation in a single packed column is introduced. It is illustrated for the recovery of dilute 1,3-propanediol from an aqueous fermentation broth. 1,3-Propanediol is recovered by reaction with isobutyraldehyde, forming 2-isopropyl-1,3-dioxane. The dioxane is recovered by extraction in a liquid organic phase using excess isobutyraldehyde, and then reacted in reverse to form the diol. Rigorous simulations, including a new methodology to simulate the dynamic transition from reactive extraction to reactive distillation, and economic analyses are presented. The semicontinuous process is shown to have lower costs and energy requirements than a previously proposed continuous process using this unique reaction route. However, in this case, direct distillation has lower costs than either reaction process.