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Hao W.,Xiamen University | Tang X.,Xiamen University | Zeng X.,Xiamen University | Sun Y.,Xiamen University | And 3 more authors.
BioResources | Year: 2015

A comprehensive, kinetic experiment on the conversion of glucose to 2-hydroxyethyl levulinate ethylene ketal (HLEK), in a cascade of reactions in ethylene glycol, catalyzed by low-concentration sulfuric acid, was conducted. The ethylene glycol/sulfuric acid system was found to be tolerant of a high glucose concentration, and no solid humins were created. At a high initial glucose concentration (30 wt %), an HLEK yield of 27.6% was achieved at a moderate temperature (433 K) after a 330-min reaction with dilute sulfuric acid (0.15 mol/L). In ethylene glycol, more than half of the initial glucose was converted into glucosides within 5 min, and a dynamic equilibrium between these species was achieved; thus, it is reasonable to assume that the ratio of glucosides to glucose was constant (1.35:1) during the entire reaction process. The production of HLEK from glucose via glucosides as a function of the process variables was well-represented by a simplified first-order kinetic model, and the rate expressions were applied to determine the optimum conditions for batch processing.

Tang X.,Xiamen University | Li Z.,Xiamen University | Zeng X.,Xiamen University | Jiang Y.,Xiamen University | And 6 more authors.
ChemSusChem | Year: 2015

In this work, the hydrocyclization of methyl levulinate (ML) to γ-valerolactone (GVL) was performed in MeOH over an in situ prepared nanocopper catalyst without external H2. This nanocopper catalyst served as a dual-functional catalyst for both hydrogen production by MeOH reforming and hydrogenation of ML. Nearly quantitative ML conversion with a GVL selectivity of 87.6 % was achieved at 240 °C in 1 h in MeOH under a nitrogen atmosphere. ML in the methanolysis products of cellulose also could be hydrogenated effectively to GVL over this nanocopper catalyst even in the presence of humins to give an ML conversion of 94.1 % and a GVL selectivity of 73.2 % at 240 °C in 4 h. The absorption behavior of humins on the surface of the nanocopper catalyst was observed, which resulted in a pronounced increase in the acidic sites of the nanocopper catalyst that facilitate ring-opening and the hydrocarboxylation/alkoxycarbonylation of GVL to byproducts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jiang Y.,Xiamen University | Chen W.,Xiamen University | Sun Y.,Xiamen University | Sun Y.,Key Laboratory of Biomass Energy and Materials of Jiangsu Province | And 6 more authors.
Industrial Crops and Products | Year: 2016

5-(Hydroxymethyl)furfural (HMF) is an important platform chemical, but the large scale production is limited by its instability. In this research, 5-[(formyloxy)methyl]furfural (FMF), derived from HMF, was produced directly from cellulose in formic acid reaction system with a yield of 33.4 mol% at 150 °C for 2 h. Among numerous metal salt catalysts screened in this study, alkali metal bromides were found to be effective in catalyzing cellulose conversion to FMF. Bromide anions facilitation of the esterification of HMF to form FMF was confirmed. In addition, the effects of water, acid and other reaction parameters also were investigated when NaBr was used as the catalyst. Up to 2% of water or acid in this reaction system did not impact on the FMF yield. Increasing the temperature for every 20 °C from 130 °C to 170 °C halved the reaction time but did not change the maximum yield. FMF was more hydrophobic and thermostable than HMF, which made it easier to be recovered. In a two-step process, FMF with a recovery of 29.4 mol% and purity of 97 mol% was obtained. © 2016 Elsevier B.V..

Hao W.,Xiamen University | Li W.,Xiamen University | Tang X.,Xiamen University | Zeng X.,Xiamen University | And 4 more authors.
Green Chemistry | Year: 2016

An efficient process for the catalytic transfer hydrogenation of biomass-derived 5-hydroxymethyl furfural (HMF) to 2,5-bishydroxymethyl furan (BHMF) is presented using ethanol as a hydrogen donor and solvent over low-cost ZrO(OH)2. A HMF conversion of 94.1% and a DHMF selectivity of 88.9% were achieved at 423 K in 2.5 h. The fresh, spent, and regenerated catalysts were characterized comprehensively, and the OH group of ZrO(OH)2 as sites for ligand exchange with ethanol was considered to be important for the activity. © The Royal Society of Chemistry 2016.

Tang X.,Xiamen University | Zeng X.,Xiamen University | Li Z.,Xiamen University | Li W.,Xiamen University | And 6 more authors.
ChemCatChem | Year: 2015

This is the first report of HCl/ZrO(OH)2 catalysts prepared in situ by the autonomous decomposition of ZrOCl2·8 H2O in levulinic acid (LA)/2-butanol solution, which catalyzed the esterification of LA in tandem with hydrocyclization to γ-valerolactone (GVL) by Meerwein-Ponndorf-Verley (MPV) reduction without the use of external H2. A maximum GVL yield of 92.4 % from neat LA and a GVL formation rate of 1092.2 μmol g-1 min-1 were achieved in 2-butanol at 240 °C in 2 h. The in situ generated ZrO(OH)2 was characterized comprehensively and its unexpected catalytic efficiency was attributed mainly to its extremely high surface area. A crude LA stream from the acid hydrolysis of cellulose was extracted into 2-butanol and subjected to this catalyst system to give a GVL yield of 82.0 % even in the presence of humins. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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