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 % (C fruc = 0.1 M; C acid = 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 % (C fruc = 0.1 M; C acid = 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.

We here report experimental and kinetic modeling studies on the conversion of sucrose to levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) in water using sulfuric acid as the catalyst. Both compounds are versatile building blocks for the synthesis of various biobased (bulk) chemicals. A total of 24 experiments were performed in a temperature window of 80–180 °C, a sulfuric acid concentration between 0.005 and 0.5 M, and an initial sucrose concentration between 0.05 and 0.5 M. Glucose, fructose, and HMF were detected as the intermediate products. The maximum LA yield was 61 mol %, obtained at 160 °C, an initial sucrose concentration of 0.05 M, and an acid concentration of 0.2 M. The maximum HMF yield (22 mol %) was found for an acid concentration of 0.05 M, an initial sucrose concentration of 0.05 M, and a temperature of 140 °C. The experimental data were modeled using a number of possible reaction networks. The best model was obtained when using a first order approach in substrates (except for the reversion of glucose) and agreement between experiment and model was satisfactorily. The implication of the model regarding batch optimization is also discussed.

Fast pyrolysis is as a promising and versatile technology to depolymerize and concentrate sugars from lignocellulosic biomass. The pyrolysis liquids produced contain considerable amounts of levoglucosan (1,6-anhydro-β-d-glucopyranose), which is an interesting source for glucose (GLC). Here, we report a kinetic study on the conversion of levoglucosan (LG) to GLC in water using sulfuric and acetic acid as the catalysts under a wide range of conditions in a batch setup. The effects of the initial LG loading (0.1–1 M), sulfuric and acetic acid concentrations (0.05–0.5 M and 0.5–1 M, respectively), and reaction temperatures (80–200 °C) were determined. Highest GLC yields were obtained using sulfuric acid (98 mol %), whereas the yields were lower for acetic acid (maximum 90 mol %) due to the formation of byproducts such as insoluble polymers (humins). The experimental data were modeled using MATLAB software, and relevant kinetic parameters were determined. Good agreement between experimental and model was obtained when assuming that the reaction is first order with respect to LG. The activation energies were 123.4 kJ mol–1 and 120.9 kJ mol–1 for sulfuric and acetic acid, respectively.

Background: 5-Hydroxymethylfurfural (HMF), an important biobased platform chemical, is accessible by the acid catalysed conversion of biopolymers containing hexoses (cellulose, starch, inulin) and monomeric sugars derived thereof. We here report an experimental study on the uncatalysed, thermal conversion of inulin to HMF in aqueous solutions in a batch set-up. Results:The reactions were conducted in a temperature range of 153-187°C, an inulin loading between 0.03 and 0.12 g/mL and batch times between 18 and 74 min using a central composite experimental design. The highest experimental HMF yield in the process window was 35 wt% (45 mol%), which is 45% of the theoretical maximum (78 wt%). The HMF yields were modeled using a statistical approach and good agreement between experiment data and model was obtained. The possible autocatalytic role of formic acid (FA) and levulinic acid, two main byproducts, was probed by performing reactions in the presence of these acids and it was shown that particularly FA acts as a catalyst. Conclusions:Inulin is an interesting feed for the synthesis of HMF in water. A catalyst is not required, though autocatalytic effects of FA play a major role and also affect reaction rates and product yields. Graphical abstract:Chicory 5-hydroxymethylfurfural No catalystInulin