Biomass conversion to alkyl levulinates using heteropoly acid carbon mesoporous composites

Abstract

With regards to the importance of biomass conversion into valuable compounds such as alkyl levulinate (AL), herein, the synthesis of butyl levulinate (BL) and ethyl levulinate (EL) from various carbohydrates (fructose, glucose, and sucrose) was studied using a series of phosphomolybdic acid (HPMo) catalysts supported on carbon mesoporous CMK-8 and CMK-3. The effect of acid loading as well as the influence of carbon mesoporous on carbohydrate conversion into ALs was investigated. Furthermore, mono lacunary phosphomolybdate catalyst supported on CMK-8 was prepared and its efficiency was compared to the optimum catalyst (CMK-HPM-50). XRD, N2 adsorption-desorption, SEM-EDX, FT-IR, TGA-DTA, and TEM analysis were performed for characterization of the synthesized catalysts. Compared to other catalysts, CMK-HPM-50 with 50% acid loading on CMK-8 showed the best results for the BL and EL production with yields of 42, 57, 66% and 53, 64, 72% from sucrose, glucose, and fructose, respectively, due to the unique 3D cubic mesostructure of CMK-8 and high Brønsted acidity of immobilized HPMo. The conversion of carbohydrates to ALs (BL and EL) was almost completed (> 98%) at all of the experiments. Various factors including, the amount of catalyst, reaction time, and reaction temperature were studied. According to the results, 50 mg of CMK-HPM-50 catalyst, 180 °C for the reaction temperature, and 3 h for the reaction time were selected as optimum conditions.