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SnCl4, a versatile Lewis acid catalyst in the biomass conversion, plays a positive role for the cellulose biomass conversion but negative for chitin biomass conversion as realized in our previous research. In this report, the unexpected effects of SnCl4 on the conversion of d-glucosamine (GlcNH2) to 5-hydroxymethylfurfural (5-HMF) in ZnCl2 molten salt hydrate medium were investigated. The strong interaction between SnCl4 and GlcNH2 in ZnCl2 molten salt hydrate medium was examined by nuclear magnetic resonance (NMR) techniques. Additionally the d-glucose and N-acetyl-d-glucosamine were also utilized in NMR titration experiments to reveal the complexation of amino group with Sn4+ ions during the catalytic process. The observed drifts of chemical shifts and signal broadening of the C2 position of GlcNH2 in 13C NMR spectra indicates that the amino group in GlcNH2 is probably the Sn4+ ion complexation site. The correlations in the 1H-15N HSQC NMR spectra provide the direct evidence and further confirm that the amino group is the complexation site between SnCl4 and GlcNH2. This very specific complex between the amino group and the Sn4+ ion inhibit the conversion of GlcNH2 to 5-HMF in ZnCl2 molten salt hydrate medium.

Lignite showed high capacity for reducing Cr(VI) to Cr(III) and hence removed Cr(VI) from aqueous solution, but the reduced Cr(III) cannot be released from adsorbent afterwards especially under acidic condition. In order to know why Cr(III) ions are immobilized within lignite adsorbent and how to recovery Cr species, the interaction of Cr(III) ions with lignite oxidized by Cr(VI) was studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The data obtained from these studies indicate that Cr(III) ions are bonded to oxygenic functional groups in lignite oxidized by Cr(VI) and electrons are delocalized over -O-Cr-O- domain. It is also revealed that the O atoms of C = O and C-O groups in the adsorbent matrix are bonded to Cr(III) ions along with the decrease of electron density, while the O atoms of O -C = O group are along with the increase of electron density. Based on these important structural information, we developed a method to treat Cr-loaded lignite further and to recover the Cr species.

Brown coal-based materials are excellent adsorbents for reducing chromium(VI) to chromium(III) and afterward immobilizing these chromium(III) by the binding of oxygenic functional groups in adsorbents. In the study, the approach of pyrolysis is employed for the treatment of Cr-loaded solid waste. The effects of adsorbed chromium on the pyrolysis of Xilingol brown coal were studied, and the solid char residues were collected to characterize with XPS, XRD and SEM/EDX. For the pyrolysis in Ar, the mass loss rates of Cr-loaded samples were much higher than that of unloaded samples above 750 °C, together with the increase in CO and H2 emission. XPS spectra revealed that the increase in CO could be related to formation of [Cr–O–C]. For the pyrolysis in CO2, the presence of chromium was more favorable for the conversion of char, especially demineralized brown coal and kerogen. The maximum decomposition temperatures for the Cr-loaded samples were about 200 °C lower than that of unloaded samples. The char residue yields of Cr-loaded samples were obviously higher than that of corresponding unloaded samples (at 1200 °C). Finally, the chromium in the solid residue was recovered in the form of Cr2O3. The present study exploits an approach method for both brown coal waste treatment and chromium recovery.

In this study, different from previous reports focused on removal efficiency of Cr(VI), the structural variations of brown coal and kerogen concerned with Cr(VI) removal were studied. The process conditions of Cr(VI) removal were optimized, and the reduction of Cr(VI) to Cr(III) was evaluated. In addition, the variations of functional groups in brown coal and kerogen before and after Cr(VI) detoxification were characterized by FTIR, XPS, SS-NMR, TEM-EDS, and SEM-EDS. The results indicated that brown coal and kerogen had highly adsorption efficiency for Cr(VI) (maximum 4.67 mmol/g), and 80.1% of adsorbed Cr(VI) was reduced to Cr(III) while 90.4% of them was held on the adsorbents. It also revealed that the content of –CH 3 , –CH 2 , C O and phenolic hydroxyl groups in adsorbents decreased, but the content of C O and O–C O groups increased after Cr(VI) detoxification. Overall, structure identified of brown coal and kerogen in this work could provide important basic data for further application in wastewater treatment.

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.

Low temperature 1H- and 19F-DOSY have been used for analyzing reactive intermediates in glycosylation reactions, where a glycosyl trichloroacetimidate donor has been activated using different catalysts. The DOSY protocols have been optimized for low temperature experiments and provided new insight into acid catalyzed glycosylation chemistry. From the study a new glycosylation intermediate was characterized.

The basic ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) could efficiently catalyze the conversion of 2-amino-2-deoxy-d-glucose (GlcNH2) into deoxyfructosazine (DOF) and fructosazine (FZ). Mechanistic investigation by NMR studies disclosed that [C2C1Im][OAc], exhibiting strong hydrogen bonding basicity, could coordinate with the hydroxyl and amino groups of GlcNH2via the promotion of hydrogen bonding in bifunctional activation of substrates and further catalyzing product formation, based on which a plausible reaction pathway involved in this homogeneous base-catalyzed reaction was proposed. Hydrogen bonding as an activation force, therefore, is responsible for the remarkable selectivity and rate enhancement observed.

Low temperature