Levulinic Acid Production from Starch Using Microwave and Oil Bath Heating: A Kinetic Modeling Approach

This work examines the role played by starch composition and heating media in the synthesis of the promising biorefinery chemical levulinic acid (LA). Three corn starches with different amylose/amylopectin ratios were converted to LA using both microwave and conventional oil bath heating. The results obtained for the different reaction temperatures and times were used to calculate kinetic parameters using a multireaction model. It was observed that the long preheating and cooling times employed in microwave heating led to equivalent reaction temperatures below the set temperatures, and this in turn affected the product distributions via changes in the reaction kinetics. At low reaction temperatures, high amylopectin waxy corn starch gave higher LA yields than normal or high-amylose corn starch. Similarly, LA yields were higher at lower temperatures for oil bath heating than for microwave heating. The maximum LA yield obtained was around 53-55% for all substrates and for both heating media, but was obtained for a shorter reaction time and at a lower equivalent temperature in the case of microwave heating.