Dielectric Properties During Microwave-Induced Interesterification Reactions for Biodiesel and Triacetin Production

The microwave-assisted interesterification of babassu oil with methyl, ethyl and butyl acetates was carried out via acid catalysis, using sulfuric, phosphoric, methanesulfonic and acetic acids for the production of biodiesel with triacetin as an additive. Dielectric measurements in the range of 0.3 to 13 GHz of pure reactants and reactions media lead to a clear understanding of the interaction between the medium and microwave irradiation, allowing achieving optimal conditions in terms of microwave power, kind and catalyst concentration, reactant molar ratios, and temperatures. Using ethyl acetate, reactions were carried out at various oil to acetate molar ratio (1:12 to 1:72) using sulfuric acid (0.5% m/m_T) as a catalyst. For 1:60 molar ratio, the experiments were carried out with 0.5 to 2% m/m_T sulfuric acid. The kind of catalyst and the applied microwave power to mass ratio were investigated using H₃PO₄, CH₃COOH and CH₃SO₃H. The best catalytic activities were achieved with H₂SO₄ and CH₃SO₃H. It was found that under microwave or conventional heating the reactivity follows the ethyl→methyl→butyl trend. The best results were achieved using ethyl acetate with H₂SO₄ which yields 91.1% biodiesel and 18.3% triacetin in 120 min under microwave heating while using CH₃SO₃H yields 80.1% biodiesel and 11.2% triacetin.

Keywords:
interesterification; microwave heating; dielectric properties; triacetin; biodiesel