We performed a systematic experimental kinetics study on AlCl3-catalyzed conversion of glucose to 5-hydroxymethylfurfural (HMF) in NaCl–H2O/tetrahydrofuran (THF) biphasic solvent. The kinetics model covers an extensive reaction network including the parallel and tandem reactions of isomerization, dehydration, decomposition, and polymerization from glucose. The accuracy of the model was verified by a parity plot and statistical significance analysis of the kinetic parameters. A deliberate insight into the intrinsic kinetic properties (reaction rate constant and apparent activation energy) of each subreaction elaborates the regulatory role of THF and NaCl on reaction pathways within the network. That is, THF suppresses the rehydration, degradation, and polymerization of HMF to unwanted byproducts, inhibits fructose-to-HMF dehydration and fructose-to-humins polymerization, but promotes the generation of formic acid (FA) from the direct degradation of both glucose and fructose by facilitating the generation of [Glc/Fru + H–H2O–FA]+ species without formation of levulinic acid (LA); while NaCl promotes the dehydration and polymerization of fructose, decelerates the glucose-to-fructose isomerization, and effectively suppresses glucose-to-humins polymerization. The suppression role of NaCl on glucose conversion may come from the inhibition on mutarotation and ring opening from glucose due to the existence of a hydrogen bond between (C6)­O–H on glucose and Cl– ion. The Brønsted acid (HCl) from the hydrolysis of AlCl3 is responsible for direct glucose/fructose-to-FA degradation, HMF-to-humins polymerization, and HMF-to-FA/LA rehydration. The Lewis acidic [Al­(OH)2(aq)]+ species is active for the reversible glucose-to-fructose isomerization and direct HMF-to-FA degradation, whereas glucose/fructose-to-humins polymerization and fructose-to-HMF dehydration are both Brønsted and Lewis acid-catalyzed. This work highlights a deep understanding of the complicated reaction network in the acid-catalyzed conversion of glucose to HMF in a biphasic solvent.

Chitin is the most abundant biopolymer after cellulose but it has not been fully utilized yet. Because of biologically fixed nitrogen, effective conversion of chitin or its derivatives to value‐added organonitrogen compounds is a promising strategy to valorize chitin biomass, which has attracted increasing attention. Recently, a novel concept of shell biorefinery has been proposed on account of the huge potentials of chitin valorization. Until now, a number of valuable organonitrogen chemicals, including amino sugars, amino alcohols, amino acids, and heterocyclic compounds, have been produced from chitin biomass. In this Minireview, the focus is on the recent advances in the synthesis of organonitrogen chemicals employing chitin biomass as starting material via different catalytic processes. An outlook on the challenges and opportunities for more effective valorization of chitin will be given.

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Effective conversion of chitin or its derivatives (i.e., chitosan) to value-added organonitrogen compounds is a promising strategy to valorize chitin. Glucosaminic acid (GlcNA) is an important amino acid derived from chitosan. In this work, we demonstrate the feasibility of GlcNA production from chitosan by tandem hydrolysis and oxidation reactions without isolating glucosamine (GlcN) intermediate. The Amberlyst-15 and Au/MgO were identified as suitable catalysts for the hydrolysis and oxidation step, respectively, but the direct employment of hydrolysate from the first step in further oxidation resulted in very low yield of target amino acid. We show that humin-like polymers formed during hydrolysis poisoned Au/MgO, resulting in low GlcNA yield, and subsequently a key detoxication process of the hydrolyzed mixture using activated carbon was developed. It effectively removed the undesired side products that inhibit Au catalyzed oxidation reaction, markedly enhancing the GlcNA yield from 17% for untreated hydrolysate to 63% for preadsorbed sample. As such, a two-step process is developed to produce GlcNA from chitosan with an overall yield of 36%.

The synergetic action of tetrahydrofuran (THF) and low-pressure CO2 (1.0 MPa) is favourable for effective inhibition of humin precursor (i.e., oligomer) formation in the conversion of glucose to 5-hydroxymethylfurfural (HMF).

Sulfonated polyaniline with mutually reactive sulfonic acid groups and amine/imine represents an organocatalyst for effective production of 5-hydroxymethylfurfural (HMF) from carbohydrates in low-boiling solvents with complete restriction of HMF rehydration.

A novel sulfonated organocatalyst bearing stable double H-bonds shows high catalytic performance and good reusability for the tandem production of 5-ethoxymethylfurfural (EMF), a biofuel candidate, from biomass-derived fructose.

We report an unprecedented solid organic-base catalyst, formyl-modified polyaniline (FS-PAN), for the dehydration of fructose to 5-hydroxymethylfurfural (HMF) with a high yield of 90.4 mol %. We demonstrate that the nitrogen atoms incorporated between the phenyl rings in the backbone of the polyaniline chain contribute to the basicity of the catalyst. The grafting of electron-withdrawing formyl groups to the imine nitrogen atoms leads to a significant increase of basicity of the polymer catalyst owing to the greater localization of electrons at the amide nitrogen atom formed. A linear dependence of the yield of HMF on the grafting level of formyl groups in FS-PAN indicates that the amide acts as the active phase. A possible reaction mechanism for this organic-base-catalyzed dehydration reaction is proposed. The side-reaction of HMF rehydration is inhibited thoroughly, and the condensation of any reaction intermediates to undesirable oligomers is restrained by this base catalyst. This organic-base catalyst can be recycled completely without loss of activity. This research highlights the first application of a highly effective and stable solid base catalyst for the transformation of renewable carbohydrates into fine chemicals.