Toward an integrated conversion of fructose for two-step production of 2,5-furandicarboxylic acid or furan-2,5-dimethylcarboxylate with air as oxidant

Abstract

This study described a bifunctional catalyst consisted of iron nanoparticles (NPs) loaded in carbon decorated with nitrogen-sulfur heteroatoms (FeNC@S) for the oxidation-dehydration of fructose to 2,5-furandi-carboxylic acid (FDCA) or furan-2,5-dimethylcarboxylate (FDMC) via intermediate 2,5-diformyl-furan (DFF) with air as oxidant by two-step, which was manufactured by pyrolyzing a mixture of Fe-thiourea-chitosan. The synthesized FeNC@S catalyst exhibited outstanding activity and recyclability. More than 93% FDCA or FDMC was obtained. The characterization of the catalyst indicated that the modification of thiourea strongly promoted the dispersion of the FeOx nanoparticles and specific surface. FeNC@S was characterized by abundant sulfonic acid groups, which provided sufficient acid sites for the fructose dehydration. The N-modification improved the activity of FeOx for the 5-hydroxymethylfurfural oxidation via adjusting the electronic cloud distribution of FeOx, increasing surface lattice oxygen ratio and oxygen mobility. And the mechanism study indicated the lattice oxygen activity was improved via weakening Fe-O bond strength. Further, this protocol provided an alternative idea for the efficient preparation of FDCA and FDMC from fructose.