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5‐Hydroxymethylfurfural (HMF) was transformed into 2,5‐diformylfuran (DFF) with nitric acid as the oxidant. The initial HMF content was as high as 12.5 wt %, and water was the sole solvent. This is an intensely exothermic reaction along with the emission of NO2 gas. A high DFF yield of 83.2 % was achieved if the oxidation ability of nitric acid matched with the requirement of target oxidation reaction while mismatched those of side reactions by regulating the initial concentration of nitric acid (59.5 wt %) and reaction temperature (50–60 °C). The oxidation reaction of HMF, overoxidation of HMF, and skeleton‐cracking reaction of FDCA preferred concentrated HNO3, hot HNO3, and concentrated or hot HNO3, respectively. After liquid‐liquid extraction, filtration, and column chromatography, light‐yellow DFF powders with purity of 92.1 wt % and isolated yield of 40.2 % were obtained and confirmed by NMR, FTIR, UV‐Vis, and elemental analysis. HMF was the dominant impurity due to its affinity to DFF. In addition, chromogenic substances were obtained as a byproduct, and they were potential pH indicators. These chromogenic substances had highly conjugated molecular structures, and they were generated via successive β‐protonation‐based ring‐opening reaction of HMF, aldol reaction, and dehydration reaction. [ABSTRACT FROM AUTHOR]

For the controllable transformation of C3–6 diols in ethylene glycol (EG), a H-Beta zeolite catalyst was modified with NH3via incomplete desorption. 60.8% of acid sites on the zeolite were deactivated, but the ratio of strong acid sites was obviously increased. With 1,2-pentanediol (PDO) as a representative large-carbon-number diol, the undesirable acetalization and oligomerization reactions of EG were suppressed in the EG-PDO reaction system over the modified catalyst due to their dependency on total acid sites. NH3-TPD and FTIR results proved that Lewis acid sites on the modified zeolite were eliminated after modification, resulting in the suppression of acetalization and oligomerization reactions. In contrast, a portion of strong Brønsted acid sites still remained, ensuring the catalytic transformation of PDO. Only 8.2% of EG was consumed after 8 h reaction, and the conversion of PDO could reach 84.3%. The loading of NH3 on the surface of zeolite pores led to diffusion resistance, slightly decreasing the reaction rate of PDO without affecting the reaction selectivity. The catalytic reactions of other C3–6 diols in EG followed similar principles, and the selectivity to aldehydes or ketone was improved over this modified catalyst. Non-diol biomass hydrogenation products such as glycerol had a negative influence on the selectivity, so these components should be isolated before the reactions. This catalyst could be reused at least 5 times, and the conversion of PDO slightly decreased. This work sheds light on the relationships between the acid properties of the catalyst and different reactions of diols. [ABSTRACT FROM AUTHOR]

This study aimed to extract pectin from local Majiayou pomelo (Citrus grandis (L.) Osbeck) peel in Jiangxi province with distilled water, hydrochloric acid and citric acid, respectively, and analyze the physicochemical components of pectin and its adsorption properties on Pb(II), and explicit the effect of adsorption parameters (initial pH value, initial ion concentration, adsorption time) on Pb (II) and its adsorption mechanism by adsorption isotherms and adsorption kinetics. The results showed that the yield of pectin by citric acid extraction (CEP) was highest (28.62%), followed by hydrochloric acid extraction (HEP) and distilled water extraction (WEP). In addition, the esterification degree (58.20%) and molecular weight (598.40 ku) of CEP were significantly lower than those of WEP and HEP (P<0.05), indicating that CEP had more carboxyl and higher solubility. The three pectins showed optimal adsorption of Pb (II) at initial pH 5.0, and reached equilibrium after 120 min adsorption. In addition, the adsorption capacity of CEP on Pb (II) was significantly higher than that by WEP and HEP. The adsorption isotherms of the three pectins were in accordance with Langmuir monolayer adsorption model, and the adsorption kinetics of the three pectins was consistent with pseudo first-order kinetics model. The adsorptions of three pectins on Pb (II) were the result of physical and chemical adsorption. Conclusion: The physicochemical properties of pectin and its adsorption capacity on Pb (II) were closely related to the extraction method, and CEP has a high adsorption capacity on Pb (II), which could be used as a low-cost, efficient, natural and environmental friendly adsorbent for removal of Pb (II). [ABSTRACT FROM AUTHOR]

TMSCFX2 (X = Cl, Br; TMS = trimethylsilyl) have been developed as halofluorocarbene (CFX, X = Cl, Br) precursors for [2+1] cyclopropanation with alkenes. Structurally diverse halofluorocyclopropanes were obtained in good to excellent yields. It was found that the reactivity order of the three halofluorocarbene reagents (TMSCF2Br, TMSCFCl2, and TMSCFBr2) in halofluorocyclopropanation with 1,1-diphenylethylene can be very different under different reaction conditions. [ABSTRACT FROM AUTHOR]