Solvent-free heteropolyacid-catalyzed glycerol ketalization at room temperature

Abstract

Currently, glycerol has been produced in large amounts as a biodiesel co-product. Therefore, developing processes to convert it into more valuable chemicals has attracted significant attention. Glycerol ketals are compounds useful as synthesis intermediates, fragrance ingredients, and mainly bioadditives for diesel and gasoline, and have been produced from reactions catalyzed by mineral acids. In this work, we assessed the activity of H₃PW₁₂O₄₀ heteropolyacid on glycerol ketalization with different ketones at room temperature and in the absence of an auxiliary solvent. The effects of the principal reaction parameters such as the reactant stoichiometry, catalyst concentration, reaction temperature, and type of carbonylic reactant were investigated. H₃PW₁₂O₄₀ heteropolyacid was much more active than other Brønsted acid catalysts evaluated (i.e. H₂SO₄, p-toluenesulfonic acid, H₃PMo₁₂O₄₀ or H₄SiW₁₂O₄₀) and exhibited high selectivity toward five-membered (1,3-dioxolane) cyclic ketals. Although homogeneous, the heteropolyacid catalyst could be recovered and reused without a loss of activity.