Novel route of reactive extraction to recover 1,3-propanediol from a dilute aqueous solution

1,3-Propanediol in aqueous solutions was reacted with propionaldehyde, butyraldehyde, or isobutyraldehyde to form substituted 1,3-dioxane. When excess aldehydes were used, the substituted 1,3-dioxanes were extracted from the aqueous phase to the aldehyde phase; in this step, aldehydes were both reactant and extractant. 1,3-Propanediol was recovered from the extractant through hydrolysis of substituted 1,3-dioxanes in reactive distillation equipment. The reaction equilibrium constants of propionaldehyde, butyraldehyde, and isobutyraldehyde were calculated as 1390-625, 3480-470, and 678-204, respectively, at 7-52 degrees C. Phase equilibrium measurements showed that the mass distribution coefficients between organic and aqueous phases for 2-ethyl-1,3-dioxane, 2-propyl-1,3-dioxane, and 2-isopropyl-1,3-dioxane were 3.96-5.40, 27.03-28.08, and 38.51-57.91, respectively, at 15-50 degrees C. Reactive extraction kinetics studies indicated that the acetalization reactions occurred easily at room temperature. The reactive extraction route present in this work is more effective than the normal distillation route.