Kinetics and Reaction Engineering of Levulinic Acid Production from Aqueous Glucose Solutions

We have developed a kinetic model for aqueous-phase production of levulinic acid from glucose using a homogeneous acid catalyst. The proposed model shows a good fit with experimental data collected in this study in a batch reactor. The model was also fitted to steady-state data obtained in a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). The kinetic model consists of four key steps: (1) glucose dehydration to form 5-hydroxymethylfurfural (HMF); (2) glucose reversion/degradation reactions to produce humins (highly polymerized insoluble carbonaceous species); (3) HMF rehydration to form levulinic acid and formic acid; and (4) HMF degradation to form humins. We use our model to predict the optimal reactor design and operating conditions for HMF and levulinic acid production in a continuous reactor system. Higher temperatures (180200 degrees C) and shorter reaction times (less than 1 min) are essential to maximize the HMF content. In contrast, relatively low temperatures (140160 degrees C) and longer residence times (above 100 min) are essential for maximum levulinic acid yield. We estimate that a maximum HMF carbon yield of 14?% can be obtained in a PFR at 200 degrees C and a reaction time of 10 s. Levulinic acid can be produced at 57?% carbon yield (68?% of the theoretical yield) in a PFR at 149 degrees C and a residence time of 500 min. A system of two consecutive PFR reactors shows a higher performance than a PFR and CSTR combination. However, compared to a single PFR, there is no distinct advantage to implement a system of two consecutive reactors.