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 (degree) 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 (degree) 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.