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Deep eutectic solvents (DESs) exhibit similar physicochemical properties to the ionic liquids. They are inexpensive, renewable, nontoxic, and environmentally benign solvents and have gradually attracted attention in several fields, for example, biorefinery. Here choline chloride-based DESs have been used as solvents and catalysts for the preparation of deoxyfructosazine (DOF) through a self-condensation reaction of d-glucosamine (GlcNH2). The catalytic performances of a “green cocatalyst”, amino acids, and the reaction mechanism were also studied. The results displayed that choline chloride/urea was capable to convert GlcNH2 efficiently, with a 13.5% yield of DOF at low temperature and with a short reaction time (100 °C, 150 min). Among the screened amino acids, arginine showed the highest activity and gave the highest yield of DOF (30.1%) under the optimized reaction conditions. Nuclear magnetic resonance (NMR) studies revealed a strong hydrogen bond interaction between GlcNH2 and arginine. Moreover, a d...

An original route for levulinic acid (LA) conversion was achieved via C–C bond formation in a co-catalysis system containing Lewis and Bronsted acids. Different from conventional base-catalyzed processes, this acidic reaction system inhibits the carboxylic acid from deactivating the base catalyst, additionally simplifies the technical processes. The synergistic effect of the two types of acids effeciently catalyzed the dimerization reaction of LA to generate two C10 compounds, tetrahydro-2-methyl-5,γ-dioxo-2-furanpentanoic acid and 3-(2-methyl-5-oxo-tetrahydrofuran-2-yl)-4-oxopentanoic acid, with the total yield of 50.9% at 59.7% conversion. These products present high added value as fuel or fine chemical precursors.

Various NMR techniques were employed to study the catalytic performance of the Lewis acid SnCl4 and the Bronsted acid HCl in the conversion of inulin to value-added compounds by hydrolysis and subsequent dehydration. The hydrolysis of inulin was examined to reveal the catalytic abilities of SnCl4 besides its intrinsic acidity by in situ 1H and 13C NMR at 25 °C. The dehydration reaction of inulin with SnCl4 as catalyst was followed by high temperature in situ 1H NMR at 80 °C. The fructose moieties were dehydrated to 5-(hydroxymethly)furfural (5-HMF), but the glucose fragment of inulin was inactive for dehydration reaction under this condition. The formation of 5-HMF and its transformation into formic acid and levulinic acid through a rehydration reaction could be monitored by in situ NMR spectroscopy. Moreover, diffusion ordered spectroscopy NMR revealed that the Lewis acid ion, Sn4+ interacts with the inulin model compounds, i.e., sucrose and fructose. The synergistic effects of complexation and acidity f...

The diffusion ordered NMR spectroscopy (DOSY) protocol for the analysis of reaction mixture of lignocellulosic biomass conversion has been developed and investigated systematically. Model reaction mixtures from cellulose, hemicellulose and lignin conversion, real reaction mixtures of sucrose and glucose dehydration, were facilely separated and assigned in the diffusion dimension without any prior separation or isolation. The shift reagent, EuFOD, was successfully utilized to increase the difference in diffusion and thereby resolution in lignin degradation model. DOSY NMR offers an easy and robust method for the structure identification and reaction mixture separation in biomass conversion.

An efficient strategy is developed for chemical recycling of cured epoxy resin (CEP) from its carbon fiber reinforced polymer composites (CFREP) using AlCl3/CH3COOH as the degradation system. Acetic acid swells the dense structures of CEP, facilitating the penetration of the aluminum ion catalyst into the polymer matrix. The weakly coordinating aluminum ions in CH3COOH solution selectively cleave the C–N bond while leaving the C–C, C–O (aryl alkyl ether) bonds intact. This process recovers valuable oligomers and carbon fibers from CFREP.

The solvent properties of ZnCl2 molten salt medium and its synergic effect with the Lewis acid catalyst, Sn4+, for biomass conversion, were investigated by nuclear magnetic resonance. The tautomeric distribution of fructose in the ZnCl2 molten salt medium was examined, and its effect for humins formation during the biomass conversion was evaluated. The ion complex composed by Sn4+ and Zn2+ indicated that there is a synergic catalytic effect between these two Lewis acid ions. 13C NMR spectra of fructose in different ZnCl2 molten salt hydrate concentrations revealed that the concentration of β-furanose and α-furanose tautomers, which lead to 5-HMF, were significantly decreased with increased salt concentration. Meanwhile the β-pyranose tautomer, which is correlated with humins formation, was increased significantly.