Synergy of Lewis and Bronsted Acids on Catalytic Hydrothermal Decomposition of Hexose to Levulinic Acid

摘要

The mixed-acid systems of four Lewis acids (FeCl_3, CrCl_3, ZnCl_2, and CuCl_2) combining three Bronsted acids (H_2SO_4, HCl, and H_3PO_4) were evaluated for the decomposition of glucose to produce levulinic acid (LA). The CrCl_3-H_3PO_4 system had a strong synergic catalytic activity for the decomposition of glucose to LA. The effects of the ratio of CrCl_3 and H_3PO_4 on glucose, fructose, and 5-hydroiymethylfurfural (5-HMF) decompositions were investigated. The mixed-acid system showed the strongest synergic catalytic activity for glucose, fructose, and S-HMF decompositions when the ratio of CrCl_3 in the CrCl_3-H_3PO_4 system was 0.4-0.5. To probe the synergic catalysis mechanism of the CrCl_3-H_3PO_4 system, the synergic catalytic activities of CrCl_3-phosphates (KH_2PO_4 K_2HPO_4, and K_3PO_4) systems on glucose decomposition were also evaluated. The possible synergic catalysis mechanisms were proposed. This study provides insights for the synergic catalysis mechanism of hexose conversion to yield LA.