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Ni phosphides and NiCo alloys are extensively explored for their remarkable efficiency in biomass alcohol oxidations, yet the underlying mechanisms remain inadequately understood. This study thoroughly elucidates the roles of Ni, Co, and P in improving the catalytic performance of Ni‐Co‐P catalysts for the electrochemical conversion of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), a promising biomass‐derived building block replacing terephthalic acid. Phosphorization of Ni results in the partial formation of Ni2P phase and significantly boosts the formation of the reactive NiOOH phase on the surface, which is the crucial catalytic phase for converting HMF into FDCA. The integration of Co into the heterojunction between Ni2P and NiOOH enhances the oxidation reactivity of 5‐formyl‐2‐furancarboxylic acid (FFCA), a pivotal intermediate influencing FDCA productivity, by selectively stabilizing aldehydes, thereby promoting further oxidation rather than surface desorption. in situ/operando spectroscopic analyses consistently highlight the equal significance of the rapid generation of NiOOH and the robust adsorption of reactant molecules at the surface in achieving high catalytic performance. These insights into elemental contributions set a new standard for designing multi‐component electrocatalysts for efficient biomass alcohol oxidation. [ABSTRACT FROM AUTHOR]

The key challenge for 5‐hydroxymethylfurfural oxidation reaction (HMFOR) lies in understanding the synergistic interactions between active sites and adsorption sites, but the uncertain spatial positions of these two sites largely limit their synergistic effect. Here, an embedded Pd/NiFe layered double hydroxide (LDH) with Pd nanoparticles (NPs) (3.6 nm) far larger than the interlayer spacing of LDH is reported, which results in the in situ generation of the defective structures at the interface of the NiFe laminate. The Pd/NiFe shows a lower onset potential of 1.34 V compared to NiFe (1.42 V). Experimental and theoretical calculations reveal that the Pd NPs exhibit a high level of orbital overlap with HMF, leading to a strong adsorption tendency and an increased local concentration of HMF near the Pd NPs. The Ni defects generated around Pd NPs result in the 3d‐orbitals of adjacent Ni sites approaching the Fermi level, reducing the oxidation barrier from Ni2+‐OH to Ni3+‐O active sites. Furthermore, this work provides crucial evidence for the hydration interactions between the aldehyde groups in HMF and the hydroxyl groups on the catalyst surface, demonstrating that the removal ability of the latter one can have an important influence on HMFOR activity. [ABSTRACT FROM AUTHOR]

Maximizing the loadings of active centers without aggregation for a supported catalyst is a grand challenge but essential for achieving high gravimetric catalytic activity, especially toward multi‐step reactions. The oxidation of 5‐hydroxymethylfurfural (HMF), a key biomass‐derived platform molecule, into 2,5‐furandicarboxylic acid (FDCA), a promising alternative to polyester monomer, is such a multi‐step reaction that involves 6 proton and electron transfers. This process often demands strong alkaline environment but also suffers from the alkali‐driven polymerization side‐reaction. Meanwhile, neutral media ameliorates the polymerization, but lacks efficient catalyst toward deep oxidation. Herein, we devised a strategy of creating ultra‐dense supported Ru oxide clusters via directed ion exchange in a Co hydroxyanion (CoHA) support material. Pyrimidine ligands were first incorporated into the CoHA interlayers, and the subsequent evacuation of pyrimidines created porous channels for the directed ion exchange with the built‐in anions in CoHA, which allowed the dense and mono‐disperse functionalization of RuCl62− anions and their resulting Ru oxide clusters. These ultra‐dense Ru oxide clusters not only enable high HMF electrooxidation currents under neutral conditions but also create microscopic channels in‐between the clusters for the expedited re‐adsorption and oxidation of intermediates toward highly oxidized product, such as 5‐formyl‐2‐furoic acid (FFCA) and FDCA. A two‐stage HMF oxidation process, consisting of ambient conversion of HMF into FFCA and FFCA oxidation into FDCA under 60 °C, was eventually developed to first achieve a high FDCA yield of 92.1 % under neutral media with significantly reduced polymerization. [ABSTRACT FROM AUTHOR]

The oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) is a key reaction in valorizing biomass. DFF is hardly soluble in water, while HMF is often obtained from biorefineries in crude wet organic fractions. Thus, the reaction is challenging for both biocatalysis performed in aqueous media, and for chemocatalysis where the presence of water often results in catalyst poisoning. Galactose oxidase (GalOx) can selectively oxidize HMF to DFF and displays promising activity in aqueous‐organic media. In this study, GalOx was immobilized on ten carriers, assessing the immobilization yield, activity, and stability. Covalently immobilized GalOx catalyzed the oxidation of HMF to DFF in neat and water‐saturated EtOAc, and in biphasic systems of various water contents. At 50 % v/v H2O, the reaction was conducted at a semi‐preparative scale (50 mL) with no adverse effect on DFF yield. Some limitations arise, such as enzyme deactivation, and adsorption of DFF to the support, particularly in the aqueous fraction. Future options to upgrade the route may include designed stable enzymes under the presence of HMF/DFF, and the setup of microaqueous systems where DFF adsorption is minimized. The use of wet EtOAc media would be a promising approach in future biorefineries employing inexpensive crude wet organic fractions. [ABSTRACT FROM AUTHOR]

The design of an "H"‐shaped reactor has been studied to satisfy the possibility of using a triphasic medium to transform d‐glucose into 5‐hydroxymethylfurfural (HMF) by a hybrid catalytic process using an immobilized glucose isomerase, allowing the isomerization of D‐glucose to d‐fructose, and a heterogeneous chemical catalyst to catalyze the dehydration of d‐fructose to HMF. The various parameters influencing the transport of d‐fructose within the reactor were studied, namely the difference in pH between the two aqueous phases, the agitation and the quantity of 3,4‐DCPBA/Aliquat336® used to extract and transport continuously the d‐fructose. The pH discrepancy, which must be between 5.0 and 5.5, turns out to be the real driving force behind the extraction of D‐fructose. The D‐Fru/3,4‐DCPBA molar ratio of 1/0.25 allowed the transport of more than 80 % of the D‐fructose initially present and shows that the same molecule of 3,4‐DCPBA is involved at least twice in the transport of D‐fructose and that the 3,4‐DCPBA/Aliquat336® couple performs a turnover within the organic phase. Finally, a HMF production yield of 30.9 % and an isomerization yield of 79.1 % were obtained, illustrating the shift in the isomerization equilibrium made possible by a D‐fructose extraction yield of 96.8 %. [ABSTRACT FROM AUTHOR]

5‐hydroxymethylfurfural (HMF) is produced upon dehydration of C6 sugars in biorefineries. As the product, it remains either in aqueous solutions, or is in situ extracted to an organic medium (biphasic system). For the subsequent oxidation of HMF to 2,5‐furandicarboxylic acid (FDCA), 'media‐agnostic' catalysts that can be efficiently used in different conditions, from aqueous to biphasic, and to organic (microaqueous) media, are of interest. Here, the concept of a one‐pot biocatalytic cascade for production of FDCA from HMF was reported, using galactose oxidase (GalOx) for the formation of 2,5‐diformylfuran (DFF), followed by the lipase‐mediated peracid oxidation of DFF to FDCA. GalOx maintained its catalytic activity upon exposure to a range of organic solvents with only 1 % (v/v) of water. The oxidation of HMF to 2,5‐diformylfuran (DFF) was successfully established in ethyl acetate‐based biphasic or microaqueous systems. To validate the concept, the reaction was conducted at 5 % (v/v) water, and integrated in a cascade where DFF was subsequently oxidized to FDCA in a reaction catalyzed by Candida antarctica lipase B. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: 5‐Hydroxymethylfurfural (HMF) is regarded as a thermal process contaminant in foods. Six flavan‐3‐ol fractions were isolated or semisynthesized from sorghum, cranberry and grape seed. Their unit compositions, interflavan linkages and degree of polymerization were characterized. The aim of this study was to investigate the effect of flavan‐3‐ols on the formation of HMF in chemical reaction models and fried potato chips. RESULTS: Results showed that all flavan‐3‐ols significantly mitigated the HMF formation at concentrations of 50, 100 and 200 µg mL−1 in the chemical model system, and the inhibition was positively related to dose. Using the food model, HMF content was reduced by about 50% when potato chips were soaked in an optimal concentration of 0.1 mg mL−1 flavan‐3‐ol solutions before frying. Based on the same mass concentration, B‐type flavan‐3‐ols mitigated more HMF than A‐type, and oligomeric proanthocyanidins had stronger inhibitory activity than polymers. At suitable addition levels (0.01–0.1 mg mL−1), the browning of auto‐oxidized flavan‐3‐ols under high temperature compensated the anti‐browning effect along with the supression of the Maillard reaction; therefore, the color of fried potato chips was not affected. CONCLUSION: This study demonstrates that flavan‐3‐ols could be effective additives for reducing HMF levels in fried potato chips without changing sensory properties. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A novel production of biobased p-xylene from hydroxymethylfurfual has been investigated and presented. This is an important part of a process for the production of aromatics from lignocellulosic biomass. The detailed flow sheets are designed based on laboratory experiments by Leshkov et al. and William et al. and economic analysis has been performed. The minimum biobased p-xylene cost is estimated as $3,962/metric ton, of which the main contribution comes from the HMF cost. Sensitivity analysis has been used to assess the impact of uncertainties of economic parameters and also to determine the most significant reaction factor in the technological development, i.e., selectivity and conversion. It has been shown that high selectivity is favored at the same yield. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2079-2087, 2013 [ABSTRACT FROM AUTHOR]

The formation of hydroxymethylfurfural, nonenzymatic brown coloured compounds and free sulphydryl groups in goat milk was studied during heating at 75-95 °C. Analysis of kinetic data suggested that formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds followed zero order reaction kinetics, while formation of free sulphydryl groups during heating varied depending on heating time. A good linear correlation ( r = 0.839) was found between brown coloured compounds and hydroxymethylfurfural content in milk samples during heating. Activation energies ( Ea) for the formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds were 96.31 and 69.79 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]