The biological production of 1,3-propanediol from glycerol, which is a by-product in a bio-diesel production process, is of great interest. However, major difficulties still exist in downstream processing because 1,3-propanediol has a high boiling point. In this study, reactive extraction with aldehydes in the presence of a hydrophobic acidic ionic liquid as an acidic catalyst was used to extract 1,3-propanediol from an aqueous solution. Hydrophobic acidic ionic liquids have successfully played the role of acidic catalysts for acetalization as well as hydrochloric acid. Aromatic compounds as diluents were preferable for this acetalization. Conversion of 60 g/dm³ of 1,3 propanediol reached 96% at a concentration of 4.0 mol/dm³ of 1-butanal in toluene.