NiAl-LDH-Derived Catalyst with Excellent Selectivity for the Selective Oxidation of 5-Hydroxymethylfurfural to Furandicarboxylic Acid

In this study, a highly active NiAl-GCN non-noble-metal catalyst was developed for the selective catalytic oxidation of 5-hydroxymethylfurfural (HMF) to furandicarboxylic acid (FDCA). NiAl-layered double hydroxide (NiAl-LDH) was first synthesized via a hydrothermal method and then blended with dicyandiamide (2-fold by mass) and heated at 550 °C for 6 h to obtain the NiAl-GCN catalyst (consisting of a NiAl mixed metal oxide and g-C3N4). The prepared catalyst was then characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), N2 physisorption measurements, and X-ray photoelectron spectroscopy (XPS) to explore its structure, morphology, chemical composition, and physicochemical properties. Next, HMF oxidation tests were carried out, and the effects of reaction time, reaction temperature, amount of oxidant, and amount of catalyst on HMF conversion and product distribution were investigated to optimize the reaction conditions. In batch tests under the optimized testing conditions (acetonitrile as solvent, t-BuOOH as the oxidant, 120 °C, 12 h), the NiAl-GCN catalyst achieved a HMF conversion of 100%, FDCA selectivity of 80.6%, and good stability during recycling experiments. The synergistic electron transfer between GCN and NiAl-MMO enhances the adsorption of HMF and activation of oxidants, leading to superior catalytic efficiency and FDCA selectivity compared to single-component catalysts.