Aerobic Oxidation of 5-Hydroxymethylfurfural to High-Yield 5-Hydroxymethyl-2-furancarboxylic Acid by Poly(vinylpyrrolidone)-Capped Ag Nanoparticle Catalysts

An efficient method for the catalytic aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) was developed using size-controlled Ag nanoparticles (NPs) in an aqueous solution. A series of AgNPs catalysts stabilized by poly(vinylpyrrolidone) (PVP) supported on ZrO2with different Ag loadings were prepared. XRD, TEM, XPS, and FT-IR techniques were used to characterize the nature of these catalysts. The impact of the Ag loading, the molar ratio of PVP to Ag, the reaction temperature and time, and the base type on the conversion of HMF and yield of HMFCA was investigated. The reaction results show that Ag–PVP/ZrO2 catalysts with a bigger particle size (u003e10 nm) exhibited superior catalytic activity and HMFCA selectivity compared to Ag/ZrO2 with a smaller particle size (ca. 8.5 nm), indicating that the addition of PVP has a promoting effect on the aerobic oxidation of HMF into HMFCA. The 2.5%Ag–PVP/ZrO2(1:1) catalyst presents an excellent activity with 100% conversio...