Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid in water by hydrotalcite-activated carbon composite supported gold catalyst

Abstract

Selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was studied using molecular oxygen without addition of any soluble base. A new, cheap and robust support (i.e. hydrotalcite-activated carbon composite, HT-AC) was prepared by physical milling of home-made HT and commercial AC, which required using less chemical consumption and simpler chemical protocol. Au/HT-AC catalyst showed superior catalytic performance for aerobic oxidation of HMF in water under mild conditions compared to Au/HT and Au/AC catalysts, respectively. It was found that the HT-AC support with the optimal ratio (2:1 in mass ratio) significantly enhanced FDCA yield and catalytic stability. After 12h at 100°C, 99.5% FDCA yield was achieved using O2 at 0.5MPa. Moreover, 99% FDCA yield was obtained using air as oxidant after 18h. The catalyst demonstrated remarkable stability during recycling up to six times. The influence of different reaction parameters was studied and optimized. Furthermore, the properties of catalysts were characterized by ICP-MS, N2 isotherms, XRD, XPS and TEM.