Microwave-Assisted Hydrothermal Conversion of Potato Peel into Levulinic Acid and Formic Acid

The current chemical industry primarily relies on basic molecules from petroleum. Nevertheless, these molecules, known as building block chemicals, can be synthesized from biomass. Therefore, the aim of this work was to evaluate the production of formic acid (FA) and levulinic acid (LA) from agro-industrial waste, particularly potato peel (PP), using a microwave-assisted hydrothermal treatment. The sample was conditioned and characterized by a physicochemical analysis. The results indicated that the PP had a high moisture content (≈ 82%) and a total carbohydrate content of 39.8%. Subsequently, a 23 factorial design was established to study the effect of temperature (100 to 180 °C), H2SO4 concentration (0 to 0.6 M) and reaction time (5 to 30 min.) on FA and LA conversion. From the experimental trials, it was possible to establish that the highest FA (2.51%) and LA (13.77%) yields were obtained at 180 °C and 0.6 M H2SO4. When ANOVA analysis was performed, it was observed that the temperature and H2SO4 concentration were the most influential parameters on FA and LA conversion. Finally, to improve the process, some tests were performed with a new set of temperatures (160, 180, and 200 °C) and acid concentrations (0.3, 0.6, and 1.0 M), and a previous hydrolysis stage was established, where the highest FA (3.19%) and LA (27.95%) yields were found at 160 °C and 1.0 M H2SO4. This work showed that it is possible to obtain value-added products from agro-industrial waste such as PP; however, further studies and experiments focused on improving the yield of the process are still required.