Preparation Of CoO_x-Ag/CeO₂ Catalyst And Its Application In Hmf Oxidation

The production of precious and environmental chemicals with ample biomass has become an enormous concern towards the shortage of trite energy.As one of the crucial biomass-derived compounds,the process from 5-hydroxymethylfurfural（HMF）to2,5-furandicarboxylicacid（FDCA）is of tremendous consequence.From the view of sustainable synthesis,design of the patent green catalysts to realize the biopharmaceuticals refinery is at an instinct need.Among the efficient noble metal catalysts for the oxidation of HMF,Ag-based catalysts have the potential to catalyze the formation of 5-hydroxymethyl-2-furanicacid（HMFCA）,but the further production of FDCA remains a great challenge.In this paper,a synthesis strategy of Co O_x-Ag/Ce O₂catalyst is proposed.The single noble metal Ag catalyst Co O_x-Ag/Ce O₂-2 achieves 92.8%yield of FDCA for the first time with 100%conversion of HMF.Even under base-free condition,the yield of 72.0%FDCA can be obtained as a breakthrough in reducing the toxicity of base.The mechanism is studied in depth and it is suggested that Ag⁺–O_v–Ce³⁺interface is formed in the catalyst according to the characterization results of XPS,Raman and H₂-TPR.The kinetic analysis of the reaction was carried out.Superoxide radicals were confirmed to play as the reactive oxygen species.The harmonious cooperation between Ag⁺and O_v–Ce³⁺sites was unveiled:Ag⁺site facilitates the cleavage of C–H bond,O_v–Ce³⁺site enhances the adsorption of reactants,accelerates the dissociation of H₂O,and promotes the conversion of O₂into superoxide radicals.This work has a breakthrough significance for the study of HMF oxidation mechanism on Ag-based catalysts,and can provide a reference for the rational design of high-performance multiphase catalysts.