Synthesis of Maleic Acid from Biomass-Derived Furfural in the Presence of KBr/Graphitic Carbon Nitride (g-C3N4) Catalyst and Hydrogen Peroxide

A one-step, liquid-phase hydrogen peroxide reaction system, which was heterogeneously catalyzed by KBr-doped graphitic carbon nitride (KBr/g-C3N4), was developed for the conversion of furfural to maleic acid (MA). At first, a 68.0% MA yield was achieved in a homogeneous reaction system catalyzed by KBr-KOH. Next, a series of K-doped g-C3N4 catalysts with various potassium salts (KBr, KCl, KNO3, and KOH) was synthesized and tested for the conversion of furfural to MA, 2-buten-1,4-olide (FRO), and succinic acid (SA). When comparing the various K-doped g-C3N4 catalysts, KBr/g-C3N4 enhanced MA selectivity, which resulted in complete furfural conversion and a 70.4% MA yield (at 100 degrees C for 180 min). Furthermore, a synergistic interaction was observed between KBr and the g-C3N4 support, which could explain why KBr/g-C3N4 had the highest MA selectivity.