Toward an Intensified Process of Biomass-Derived Monomers: The Influence of 5-(Hydroxymethyl)furfural Byproducts on the Gold-Catalyzed Synthesis of 2,5-Furandicarboxylic Acid

Abstract

The utilization of biomass and development of intensified processes are essential to establish a sustainable production of chemicals in the future. Herein, we report on a strategy that allows one to directly convert the biomass-derived platform molecule 5-(hydroxymethyl)­furfural (HMF) over Au/ZrO2 in aqueous medium to 2,5-furandicarboxylic acid (FDCA), a renewable building block for biobased polymers like polyethylene furanoate. The focus lies on identifying the influence of 5-(hydroxymethyl)­furfural synthesis byproducts, like unconverted sugars, levulinic acid, and formic acid as well as the remaining inorganics, on the synthesis of 2,5-furandicarboxylic acid to save the intermediate step of HMF purification. These components were added to the reaction mixture individually and in combination to study their effect. Although most of these substances lowered the FDCA yield, the reaction conditions could be optimized to produce FDCA quantitatively. Only the addition of levulinic acid led to a severe deterioration of the production of FDCA, which was attributed to poisoning of the catalyst. In a realistic technical scenario, the direct oxidation of impure HMF from unconcentrated sugar syrup in high FDCA yield (74%) was demonstrated. Catalyst stability was investigated in the presence of sugars. On the basis of these studies, highly needed recommendations for the HMF synthesis were developed to establish a more sustainable, technically feasible, and intensified process for direct FDCA production from sugars at industrial scales.

Challenges of Green Production of 2,5‐Furandicarboxylic Acid from Bio‐Derived 5‐Hydroxymethylfurfural: Overcoming Deactivation by Concomitant Amino Acids

“…NaOH, ratio of intended Au/HMF = 1 : 100). [7] The low concentration of HMF in the solution, caused by a nonoptimized process for HMF synthesis, was compensated by adding commercial HMF to achieve a final HMF concentration of 0.067 m, which is comparable to other studies. [8a,9b,11b,c] This bio-derived solution modified to higher HMF concentration still contains the realistic amount of impurities, the influence of which we aim to study.…”

“…For example, for Au/ZrO 2 and Au/C, the influence of the particle size on the activity of the catalysts was discussed in literature. [28] Naim et al [7] observed sintering of Au particles after HMF oxidation reaction (as confirmed by powder XRD patterns), which were not visible in the as-synthesized catalyst. To investigate the role of sintering, we determined the crystallite size of nanoparticles in AuPd(2 : 1)/C after preparation as well as after HMF oxidation by peak fitting and using the full width at half maximum (FWHM) in the Scherrer equation (details, cf.…”

“…Thus, the influence of impurities in the feedstock from biomass on the catalytic system is often not considered. [7] Naim et al [7] observed a major decrease in the FDCA yield using an Au/ZrO 2 catalyst in presence of 0.25 equiv. of levulinic and formic acid in the solution, which are among the main side products of HMF synthesis from fructose.…”

“…Although one of the main criteria for the extensive research on green FDCA synthesis is the use of abundant and renewable biomass resources, investigations on the oxidation of HMF from real biomass to FDCA have hardly been reported in the literature. Thus, the influence of impurities in the feedstock from biomass on the catalytic system is often not considered [7] . Naim et al [7] .…”

Current Advances in the Sustainable Conversion of 5‐Hydroxymethylfurfural into 2,5‐Furandicarboxylic Acid

“…The author reported that in most of the cases FDCA was produced quantitatively while only levulinic acid led to catalyst poisoning. [31]…”