Efficient Co-Cu/MS Catalyst from the Sequential Adsorption and Carbonization of Melamine Foam for the Selective Oxidation of 5-Hydroxymethylfurfural (HMF)

Polyethylenefuranoate, a suitable alternative for polyethylene terephthalate, can be synthesized from biomass-derived 2,5-furandicarboxylic acid (FDCA), which is obtained via the selective oxidation of 5-hydroxymethylfurfural (HMF) over noble or non-noble metal oxide catalysts. However, the FDCA yields using non-noble metal catalysts can be improved. Hence, in this study, we developed a series of Co- and Cu-embedded melamine sponge (MS)-derived carbon catalysts (xCo-Cu/MS) for HMF oxidation, wherein Co and Cu oxides with different Co : Cu ratios were embedded in carbonized MS. The metals were adsorbed on the MS, followed by carbonization. This strategy allowed the uniform distribution of metal clusters in the carbon texture, which enhanced the catalytic activity for HMF conversion and improved the FDCA yield. The good distribution and small crystal size of Co3O4 significantly increased the active surface area, enhancing the catalytic activity. Compared to Co-Cu/MS catalysts, the 4Co-Cu/activated carbon catalyst synthesized via impregnation afforded the maximum FDCA yield (93 %) with 100 % HMF conversion at 170 C-degrees and 7 h. Moreover, oxidative regeneration using H2O2 proved to be the best regeneration method for the MS catalysts, with only a 5 % decrease in the FDCA yield after three cycles.