Process intensification in the ketalization of glycerol with acetone catalyzed by NaHSO₄-NaOH catalytic system

Glycerol is one cheap byproduct in production of biodiesel, and the ketalization of glycerol is one of the most important and effective way to increase its value and improve the sustainability of biodiesel. The ketalization of glycerol with acetone is always catalyzed by acid catalyst. In this work, NaOH was added into the reaction system during the ketalization process catalyzed by NaHSO₄, and it was found for the first time that this process could be intensified by NaOH significantly. The acidity of acidic catalysts would affect their catalytic performance. Increasing reaction temperature and time, molar ratio of acetone to glycerol, the dosage of NaHSO₄ and molar ratio of NaOH to NaHSO₄ could favor for the ketalization, but the excessive formation of water and the evaporation of acetone would retard the reaction. The addition of NaOH could destroy the intermolecular hydrogen bond network of glycerol molecules, making the hydroxyl groups bared in free state, and increase the amount of electrophilic transition state of acetone, which help to promote the transformation of glycerol to solketal significantly. With the assistance of NaOH, the conversion rate of glycerol could even reach 97.58 % without extracting water continuously from the reaction system.