An unexpected behavior of H3PMo12O40 heteropolyacid catalyst on the biphasic hydrolysis of vegetable oils

Abstract

Fatty acids (FA) are key ingredients in formulating numerous high-value chemicals. In general, catalytic routes for their production require drastic conditions of pressure and temperature or homogeneous catalysts and high water consumption. The novelty of this work is to discover a versatile catalyst for hydrolysis reactions able to migrate from the aqueous phase into the oil phase throughout the process and then back to the initial phase at the end of reaction: the H₃PMo₁₂O₄₀ heteropolyacid catalyst. We have found that variation in the pH value during the reaction promoted the conversion of PMo₁₂O₄₀³⁻ heteropolyanion to a PMo₁₁O₃₉⁷⁻ lacunar anion which was partially soluble in the oil layer, favouring the reaction. H₃PMo₁₂O₄₀ was compared with other heteropolyacids and also to sulfuric acid. The effects of the main reaction variables such as temperature, water : oil molar ratio, concentration and type of catalyst were assessed. ¹H NMR spectroscopy analysis allowed monitoring the reactions and provided fatty acid yields.