Catalytic Decomposition of Glucose to Levulinic Acid by Synergy of Organic Lewis Acid and Brønsted Acid in Water

Four organic Lewis acids, samarium(III), aluminum(III), yttrium(III), and indium(III) trifluoromethanesulfonates were combined with four organic Brønsted acids, benzenesulfonic, toluene-p-sulfonic, trichloroacetic, and oxalic acids to synergistically catalyze the decomposition of glucose to produce levulinic acid (LA). The combination of aluminum trifluoro-methanesulfonate (Al(CF3SO3)3) and oxalic acid (H2C2O4) exhibited a strong synergic activity for the decomposition of glucose to LA. The effects of the mole fraction of Al(CF3SO3)3 in the Al(CF3SO3)3-H2C2O4 system on the decompositions of glucose, fructose, and 5-hydroxymethylfurfural (5-HMF) were investigated. The mixed-acid system showed the strongest synergic catalytic activity for glucose, fructose, and 5-HMF decompositions at the Al(CF3SO3)3 mole fraction of 0.33. The effect of temperature on the decomposition of glucose in the Al(CF3SO3)3-H2C2O4 system was also investigated. Based on the results obtained in this contribution and previous work, synergy in catalytic systems was demonstrated.