Copper Phosphotungstate-Catalyzed Microwave-Assisted Synthesis of 5-Hydroxymethylfurfural In A Biphasic System

In this paper, we have described a novel route to produce 5-hydroxymethylfurfural (HMF), a valuable platform-molecule obtained from biomass, using transition metal-exchanged Keggin heteropolyacid salts as catalysts, in microwave-assisted reactions carried out in a water-ethyl acetate biphasic system. To avoid the use of homogenous Brønsted acid catalysts, which are corrosive and difficult to be reused, we have exchanged the protons of the Keggin heteropolyacids by transition metal cations. These salts were evaluated in the fructose dehydration, being the Cu3/2PW12O40 the most active and selective catalyst, achieving 81 % of HMF yield, after 15 min reaction at 413 K under microwave irradiation (MWI). The effects of metal cation, anion, and heteropolyanion present in the catalyst were evaluated. The greatest efficiency of Cu3/2PW12O40 was attributed to its high Lewis acidity strength, which allows that it coordinate with water molecules, consequently generating H3O+ ions in the reaction medium. Even though the catalyst has been water-soluble, it was easily reused removing the extracting phase, and adding a new load of the substrate to the remaining aqueous phase. This way, it was successfully reused without loss activity.

Phosphate Enrichment of Niobium-Based Catalytic Surfaces in Relation to Reactions of Carbohydrate Biomass Conversion: The Case Studies of Inulin Hydrolysis and Fructose Dehydration

In this work, some physical mixtures of Nb2O5·nH2O and NbOPO4 were prepared to study the role of phosphate groups in the total acidity of samples and in two reactions involving carbohydrate biomass: hydrolysis of polyfructane and dehydration of fructose/glucose to 5-hydroxymethylfurfural (HMF). The acid and catalytic properties of the mixtures were dominated by the phosphate group enrichment. Lewis and Brønsted acid sites were detected by FT-IR experiments with pyridine adsorption/desorption under dry and wet conditions. Lewis acidity decreased with NbP in the composition, while total acidity of the samples, measured by titrations with phenylethylamine in cyclohexane (~3.5 μeq m−2) and water (~2.7 μeq m−2), maintained almost the same values. Inulin conversion took advantage of the presence of surfaces rich in Brønsted sites, and NbOPO4 showed the best hydrolysis activity with glucose/fructose formation. The catalyst with a more phosphated surface showed less deactivation during the dehydration of fructose/glucose into HMF.

Synthesis of a sulfated-group-riched carbonaceous catalyst and its application in the esterification of succinic acid and fructose dehydration to form HMF

A novel sulfated-group-riched sulfonated carbonaceous catalyst with high acidic strength and adjustable ratio of acidic groups was designed in the paper, where glucose and benzyl chloride were hydrothermally carbonized first followed by sulfonation treatment. Various physicochemical techniques were used to characterize the catalyst such as IR, 13C MAS NMR and XPS spectra, NH3-TPD, XRD patterns and TG curve. Then, it was applied in the esterification of succinic acid and fructose dehydration to form HMF. Compared to commercial Amberlyst-15 catalyst, such carbonaceous solid acid exhibited excellent catalytic activity and thermal stability, which was attributed to its higher amount of sulfonic acid group.

Mechanistic studies on the formation of 5-hydroxymethylfurfural from the sugars fructose and glucose

In recent years the transformations of fructose and glucose to the platform chemical 5-hydroxymethylfurfural (5-HMF) have been studied extensively, and a variety of mechanisms have been proposed. This review summarizes the varied mechanisms proposed and methods used to study the dehydration of biomass, such as fructose and glucose, to give 5-hydroxymethylfurfural. For fructose dehydration, two main mechanisms have been suggested including a cyclic and an acyclic pathway, of which the cyclic pathway dominates. The conversion of glucose to 5-HMF can proceed either through initial isomerization to fructose or a direct dehydration. For glucose to fructose isomerization, two main reaction pathways have been proposed (1,2-hydride shift and enolization). This review discusses the mechanisms that have been determined based on the evidence from experiments and/or calculations, and briefly introduces the techniques frequently used in such mechanistic studies. Mechanisms in this field are strongly dependent on the nature of the solvent and the catalyst used, so it is important that researchers have a general idea about the existing mechanisms, and the methods and techniques used for investigation, before pursuing their own mechanistic studies.

CaCl2 molten salt hydrate-promoted conversion of carbohydrates to 5-hydroxymethylfurfural: an experimental and theoretical study

33.6% fructose and 52.1% HMF were achieved from glucose isomerization and dehydration in CaCl2 salt hydrate. Interactions existing in β-glucopyranose-CaCl2 and β-d-fructofuranose-Ca2+ promoted the glucose isomerization and fructose dehydration.

Improved Slit-shaped Microseparator and its Integration with a Microreactor for Modular Biomanufacturing

Modular and distributed biomanufacturing requires continuous flow microreactors integrated with efficient separation units operating at comparable time scales: biphasic reactive extraction of 5-hydroxymethyl furfural (HMF) by fructose dehydration is an...