Inexpensive but Highly Efficient Co–Mn Mixed‐Oxide Catalysts for Selective Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid

Abstract

A highly active and inexpensive Co-Mn mixed-oxide catalyst was prepared and used for selective oxidation of 5-hydroxymethylfurfural (HMF) into 2, 5-furandicarboxylic acid (FDCA). Co-Mn mixed-oxide catalysts with different Co/Mn molar ratios were prepared through a simple solid-state grinding method-a low-cost and green catalyst preparation method. The activity of these catalysts was evaluated for selective aerobic oxidation of HMF into FDCA in water. Excellent HMF conversion (99 %) and FDCA yield (95 % ) were obtained under the best reaction conditions (i.e., 120 °C, 5 h, Co-Mn mixed-oxide catalyst with a Co/Mn molar ratio of 0.25 calcined at 300 °C (Co-Mn-0.25) and 1 MPa O ). The catalyst could be reused five times without a significant decrease in activity. The results demonstrated that the catalytic activity and selectivity of the Co-Mn mixed-oxide catalysts prepared through solid-state grinding were superior to the same Co-Mn catalyst prepared through a conventional coprecipitation method. The high catalytic activity of the Co-Mn-0.25 catalyst was attributed to its high lattice oxygen mobility and the presence of different valence states of manganese. The high activity and low cost of the Co-Mn mixed-oxide catalysts prepared by solid-state grinding make it promising for industrial application for the manufacturing of polyethylene furanoate, a bioreplacement for polyethylene terephthalate, from sustainable bioresources.

Aerobic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid over Holey 2 D Mn2O3 Nanoflakes from a Mn‐based MOF

“…After that, the fraction of these two intermediates gradually decreased at a relatively low rate. The conversion of HMF increased steeply and reached a plateau about 98.0 % at 6 h and meanwhile the yield of FDCA gradually increased to 93.6 % at 12 h and finally to >99.0 % at 24 h. It is noteworthy that no DFF intermediate was detected throughout the whole reaction process, indicating the oxidation reaction in this study would be in the tandem HMF→HMFCA→FFCA→FDCA pathway, different from the HMF→DFF→FFCA→FDCA pathway for the most Mn‐based oxides . This could be because of the Mn 4+ on the surface of Mn 2 O 3 nanoflakes (observed by XPS) preferred to adsorb the −OH in geminal diol moiety rather than adsorb the −OH in the hydroxymethyl moiety in the first step.…”

“…Finally, aldehydic moiety of FFCA undergoes similar process in the first step to form carboxyl moiety, producing FDCA. The Mn 3+ arising from the above‐mentioned steps can be oxidized by the adsorbed O 2 on the catalyst surface to Mn 4+ , regenerating the Mn 4+ O 2− species …”

2,5-Furandicarboxylic acid production via catalytic oxidation of 5-hydroxymethylfurfural: Catalysts, processes and reaction mechanism

“…This study also pointed out the high concentrations of Mn 4+ and Ce 3+ on the MnO x -CeO 2 surface play a key role as active sites for the HMF oxidation. Superior oxygen mobility and various oxidation states are widely accepted to elucidate the remarkable performance of multitudinous Mn-based composites, such as Co-Mn-0.25 [74], MnCo 2 O 4 [75], and Mn-Fe mixed oxide [76]. Yu et al [77] further proposed that active M 3+ O(-Mn 4+ ) 2 clusters in (Fe, Co, Ni)-doped MnO x catalysts were the principal active sites for the aerobic oxidation of HMF (Fig.…”

Efficient Continuous Production of the Biofuel Additive 5‐(t‐Butoxymethyl) Furfural from 5‐Hydroxymethylfurfural

“…The production of HMF from the sugar platform has been extensively studied and a number of efficient catalytic systems have been reported . The rich chemistry of HMF has been explored for the synthesis of a high number of value‐added chemicals such as 5‐alkoxymethylfurfurals, 2,5‐furandicarboxylic acid, bishydroxymethylfuran, and 2,5‐dimethylfuran . In particular, due to their high cetane number, the ethers of HMF came into the spotlight as candidates for fuel applications [3a,8]…”