Electrochemical Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid (FDCA) in Acidic Media Enabling Spontaneous FDCA Separation

Abstract

2,5-Furandicarboxylic acid (FDCA) has become an increasingly desirable platform chemical to replace terephthalic acid in the production of a variety of polymeric materials, including polyethylene terephthalate. FDCA can be produced by the oxidation of 5-hydroxymethylfurfural (HMF), which can be derived from cellulosic biomass. Oxidation of HMF to FDCA is typically performed under basic conditions. Separation of FDCA is most easily accomplished by lowering the pH until FDCA is insoluble and filtering it from solution. In a large-scale process, this would lead to a high operating cost to purchase the required acid and base and to dispose of the resulting salt waste. In this study, electrochemical oxidation of HMF was carried out in acidic media by using a manganese oxide (MnO ) anode to remove the need to vary the pH to separate FDCA. The MnO anode afforded a FDCA yield of 53.8 % in a pH 1 H SO solution, in which FDCA precipitation occurred spontaneously from the same reaction solution without altering the pH or other aspects of the solution composition. Electrochemical oxidation in acidic media offers a new pathway to convert HMF into maleic acid, which is another desirable biomass-derived platform molecule. The performance of the MnO anode was investigated in comparison with that of a Pt anode to identify unique electrocatalytic properties of the MnO anode for HMF oxidation.

Electrochemical biomass valorization on gold-metal oxide nanoscale heterojunctions enables investigation of both catalyst and reaction dynamics with operando surface-enhanced Raman spectroscopy

“…Both metals and metal oxides have been investigated, with nickel oxides and nickel-containing materials generally being reported to the most active material in terms of selectivity and efficiency. [9][10][11][12][13][14][15][16][17][18] Despite its potential, mechanistic studies of electrochemical HMF oxidation on metal oxides to understand surface dynamics and key factors that render certain materials highly active, especially through spectroscopic means, are few and there are many knowledge gaps le to ll. In comparison, operando spectroscopy on reactions such as water electrolysis and CO 2 reduction has greatly enriched the eld's knowledge of these systems and consequently, accelerated progress.…”

Titanium Oxide‐Confined Manganese Oxide for One‐Step Electrocatalytic Preparation of 2,5‐Furandicarboxylic Acid in Acidic Media

“…Considering the influence of OER, the electrochemical conversion of HMF was carried out under the potential of 1.64 V, 1.69 V, 1.74 V, and 1.79 V vs RHE in an H‐type electrolytic cell separated by a porous glass frit, with the working electrode chamber containing 20 mM HMF in 0.1 M HClO 4 as anolyte (2 mL) and the counter electrode chamber containing 0.1 M HClO 4 as catholyte (2 mL). Since FDCA is insoluble in pH<2, the electrolysis process was carried out at 60 °C [14] . HMF and possible oxidation products were detected by high performance liquid chromatography method (HPLC), and quantification calculations were based on the calibration curve of standard substance (Figure S6).…”

“…Under the chosen potential, 2,5‐diformylfuran (DFF), 5‐formylfuran‐2‐carboxylic acid (FFCA) and FDCA, as well as maleic acid (MA) were detected while 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA) was negligible (Figure S7). The result was consistent with previous reports for HMF oxidation in acidic media [14] . After passing stoichiometric charges (23.16 C), the conversion of HMF was close to 100 %, with FFCA and FDCA as the main product under the chosen potential (Figure 4c).…”

“…To this end, developing the effective acidic electrocatalytic system for oxidizing HMF seems to be a promising and essential route for the preparation of FDCA, which can potentially conduct the preparation and separation of FDCA in one step, and with the coproducing valuable product at a lower voltage. Unfortunately, the development of acidic systems for oxidizing HMF to FDCA is severely limited by the available electrocatalyst [14] . The key to the successful preparation of FDCA in acidic media is the designing of electrocatalyst with HMF oxidation activity and stability.…”

“…The key to the successful preparation of FDCA in acidic media is the designing of electrocatalyst with HMF oxidation activity and stability. Up to now, MnO x was the only reported effective anode, which can prepare and spontaneously obtain FDCA precipitation in the pH 1 media without any extra assistance [14] . However, ongoing efforts are still needed to promote the catalytic activity and durability of MnO x ‐based catalysts to improve the efficiency of the scale production of FDCA.…”