Selective oxidation of 5-hydroxymethyl furfural over non-precious metal heterogeneous catalysts

• Non-precious MnxFeyOz is an active catalyst for the selective oxidation of HMF.
• The optimal catalysts composition corresponds to an atomic Mn/Fe ratio of 3/1.
• Manganese coexist as a mixture of Mn(III) and Mn(IV) with a hematite phase.
• A two steps procedure for preparation of FDCA avoids the catalyst deactivation.

An alternative synthesis of 2,5-furandicarboxylic acid (FDCA) was carried out by oxidation of 5-hydroxy-2-methyl furfural (HMF) in aqueous medium. The reaction occurred in presence of non-precious metal (MnxFey) mixed oxide catalyst. The effect of various reaction parameters such as nature and amount of base, reaction temperature, oxygen pressure, catalyst composition were investigated in order to quantitatively produce FDCA. The catalytic behavior of the mixed oxide catalyst was assigned to an optimal Mn/Fe ratio of 3/1, where a mixture of Mn(III) and Mn(IV) coexists with a hematite phase. The synergetic cooperation of these phases allowed the efficient oxidation of FFCA to FDCA. The humins species formed by HMF degradation exhibited a negative effect over the catalytic activity of Mn/Fe mixed oxide, while the chlorine resulted after the pH modification had no influence upon the catalytic oxidation.

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