1. Full, Reactive Solubilization of Humin Byproducts by Alkaline Treatment and Characterization of the Alkali-Treated Humins Formed
- Author
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van Zandvoort, Ilona, van Eck, Ernst R. H., de Peinder, Peter, Heeres, Hero J., Bruijnincx, Pieter C. A., Weckhuysen, Bert M., Sub Inorganic Chemistry and Catalysis, Inorganic Chemistry and Catalysis, Sub Inorganic Chemistry and Catalysis, Inorganic Chemistry and Catalysis, and Chemical Technology
- Subjects
General Chemical Engineering ,hydroxymethylfurfural ,carbohydrates biomass ,CARBON MATERIALS ,Humins ,biorefineiy ,SPINNING NMR ,chemistry.chemical_compound ,Hydrothermal carbonization ,Taverne ,medicine ,Environmental Chemistry ,Organic chemistry ,HYDROTHERMAL CARBONIZATION ,alkaline treatment ,Dehydration ,NUCLEAR-MAGNETIC-RESONANCE ,C-13 NMR ,Dissolution ,Renewable Energy, Sustainability and the Environment ,LIGNIN DEPOLYMERIZATION ,Aromatization ,General Chemistry ,HYDROGEN ,medicine.disease ,Alkali metal ,Solid State NMR ,SOLID-STATE NMR ,CONVERSION ,chemistry ,Humin ,CROSS-POLARIZATION ,Molar mass distribution ,Hydroxymethylfurfural - Abstract
The valorization of the humin byproducts that are formed during hydrothermal, acid-catalyzed dehydration of carbohydrates is hampered by the insolubility of these byproducts. Here, we report on an alkaline pretreatment method that allows for the insolubility of this highly recalcitrant and structurally complex feed to be overcome. The reactive solubilization of glucose-derived humins was found to require a treatment at 200 degrees C in 0.5 M NaOH for 3.5 h. Fructose- and xylose-derived humins were found to be more recalcitrant, and complete dissolution required raising the temperature to 240 degrees C. Gel permeation chromatographic analyses show the relative average molecular weight of the now soluble humins to decrease with increasing temperature and reaction time. The alkali-treated humins are soluble in water of pH >= 7. Elemental analysis, IR, 2D PASS C-13 solid-state NMR and pyrolysis-GC MS (gas chromatography mass spectrometry) data indicate that the alkaline pretreatment leads to considerable changes in the molecular structure of the humins. Cleavage of C-O-C bonds and further aromatization of the originally highly furanic humins result in the formation of (polycyclic) aromatic structures decorated with carboxylic acids. The combination of the reduction in Mw and the formation of polar functional groups are thought to be the reasons behind the improved solubility.
- Published
- 2015
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