Aerobic Oxidation of 5‐(Hydroxymethyl)furfural Cyclic Acetal Enables Selective Furan‐2,5‐dicarboxylic Acid Formation with CeO₂‐Supported Gold Catalyst

Abstract

The utilization of 5-(hydroxymethyl)furfural (HMF) for the large-scale production of essential chemicals has been largely limited by the formation of solid humin as ab yproduct, which prevents the operation of stepwise batchtype and continuous flow-type processes.The reaction of HMF with 1,3-propanediol produces an HMF acetal derivative that exhibits excellent thermal stability.A erobic oxidation of the HMF acetal with aCeO 2 -supported Au catalyst and Na 2 CO 3 in water gives a90-95 %yield of furan 2,5-dicarboxylic acid, an increasingly important commodity chemical for the biorenewables industry,f rom concentrated solutions (10-20 wt %) without humin formation. The six-membered acetal ring suppresses thermal decomposition and self-polymerization of HMF in concentrated solutions.K inetic studies supported by DFT calculations identify two crucial steps in the reaction mechanism, that is,t he partial hydrolysis of the acetal into 5-formyl-2-furan carboxylic acid involving OH À and Lewis acid sites on CeO 2 ,and subsequent oxidative dehydrogenation of the in situ generated hemiacetal involving Au nanoparticles. These results represent as ignificant advance over the current state of the art, overcoming an inherent limitation of the oxidation of HMF to an important monomer for biopolymer production.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Recent Developments in Metal-Based Catalysts for the Catalytic Aerobic Oxidation of 5-Hydroxymethyl-Furfural to 2,5-Furandicarboxylic Acid

“…Many fewer examples of concentrated HMF substrates are studied in the oxidation of HMF to FDCA. Recently, an approach for stabilizing the active formyl group of HMF by the acetalization with 1,3-propanediol was reported, which enables production of a high yield of FDCA and low humin formation, even in solutions of up to 20 wt% HMF acetal, by aerobic oxidation in the presence of a base additive [38]. In addition, extremely low concentration of HMF, together with their short-term reaction time often applied in reported cases, may underestimate other issues, particularly catalyst stability.…”

“…Formation of undesired humin is a great issue for HMF transformation, especially in concentrated HMF solutions. Kim et al reported recently progress in utilizing Au/CeO 2 catalyst for achieving 90-95% yield of FDCA via aerobic oxidation of acetal derivatives of HMF [38]. In this approach, protection of aldehyde group of HMF with 1,3-propanediol was proposed to prevent the formation of undesired humin via decomposition and self-polymerization, and to achieve efficient FDCA yield from the resultant HMF acetal derivative.…”

Heterogeneous Catalytic Conversion of Sugars Into 2,5-Furandicarboxylic Acid

“…The catalyst could be recycled at least three times without any decrease in its catalytic performance. Apart from carbon, the effect of CeO 2 as a catalyst support was investigated by Kim et al (2018) because of its Lewis acid and hydroxide ion sites. Kim et al's work with Au/CeO 2 in the aerobic oxidation of low aqueous concentrations of HMF and its cyclic acetal derivative gave a yield of 90-95% FDCA (Kim et al, 2018).…”

“…Apart from carbon, the effect of CeO 2 as a catalyst support was investigated by Kim et al (2018) because of its Lewis acid and hydroxide ion sites. Kim et al's work with Au/CeO 2 in the aerobic oxidation of low aqueous concentrations of HMF and its cyclic acetal derivative gave a yield of 90-95% FDCA (Kim et al, 2018). However, for a concentrated solution of 10 wt% under 2.0 equivalent Na 2 CO 3 FDCA yield from HMF declined to 28%, whereas oxidation of 1,3-propanediol derived cyclic acetal of HMF (PD-HMF) gave a high yield of FDCA at 94%.…”

Recent Progress in Catalytic Oxidative Transformations of Alcohols by Supported Gold Nanoparticles

“…In this regard, very recently, Hensen, Nakajima and co‐workers confirmed that protection of the formyl group of HMF with 1,3‐propanediol was a very effective approach to prevent undesired side reactions, and to achieve high conversion of the resulting PD‐HMF . They displayed that FDCA can be attained in 90–95% yields from the 20 wt% solution of PD‐HMF through aerobic oxidative transformation promoted by Au/CeO 2 catalyst with Na 2 CO 3 in water (Figure ).…”