Kinetic Study on the Sulfuric Acid-Catalyzed Conversion of d -Galactose to Levulinic Acid in Water

Levulinic acid is an interesting building block for biofuel (additives) and biobased chemicals. It is accessible by an acid-catalyzed reaction of a wide variety of carbohydrates. We here report a kinetic study on the conversion of d-galactose to levulinic acid in aqueous solutions with sulfuric acid as the catalyst. The experiments were carried out in a broad range of temperatures (140-200 °C), initial concentrations of galactose (0.055-1.110 M), and concentrations of sulfuric acid (0.05-1 M). The experimental data were modeled using a power-law approach, and good agreement between the experimental data and the model was obtained. The maximum yield of levulinic acid (54 mol %) was achieved at 130-140 °C, low initial galactose concentrations (0.055 M), and high acid concentrations (1 M). With the kinetic information available, the most suitable reactor configuration was determined, and it is predicted that a continuously stirred-tank reactor is preferred over a plug-flow reactor. The findings presented here may also be applicable to the kinetic modeling of levulinic acid synthesis from more complex biomass sources such as lignocellulosic (woody) and aquatic (e.g., seaweed) biomass.