Experimental and Kinetic Modeling Studies on the Sulfuric Acid Catalyzed Conversion of <scp>d</scp>-Fructose to 5-Hydroxymethylfurfural and Levulinic Acid in Water

Abstract

Levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) have been identified as promising biomass-derived platform chemicals. A kinetic study on the conversion of d-fructose to HMF and LA in water using sulfuric acid as the catalyst has been performed in batch setups. The experiments were carried out in a temperature window of 140–180 °C, using sulfuric acid as the catalyst (0.005–1 M) and an initial d-fructose concentration between 0.1 and 1 M. A kinetic model for the conversion of d-fructose to HMF and the subsequent reaction of HMF to LA was developed including the kinetics for the formation of solid byproducts (humins) using a power-law approach. According to the model, the maximum attainable HMF yield in the experimental window is 56 mol % (Cfruc = 0.1 M; Cacid = 0.005 M; 166 °C), which is close to the highest experimental value within the range (53 mol %) and considerably higher than that reported for d-glucose. The highest modeled LA yield was 70 mol % (Cfruc = 0.1 M; Cacid = 1 M; 140 °C), close to the experimental value of 74 mol %. This LA yield is considerably higher than that found for d-glucose within the range of experimental conditions. The model was used to determine the optimum reactor configuration for highest HMF and LA yields, and it is shown that highest HMF yields are attainable in a PFR reactor, whereas a large extent of backmixing is favorable when aiming for a high LA yield.