Mechanocatalytic depolymerization of hemicellulose to xylooligosaccharides: New insights into the influence of impregnation solvent

Mechanocatalytic depolymerization of lignocellulose constitutes a new frontier in biorefinery. In this study, a weak alkali-oxidation pretreatment with sodium percarbonate was employed to isolate hemicellulose from corncob, which was comprehensively characterized by FTIR, H-1, C-13, and 2D HSQC NMR. The influences of impregnation solvent, the type and dosage of acid catalyst, and ball-milling time on the mechanocatalytic depolymerization of hemicellulose have been systematically investigated. A mathematical model based on Kamlet-Taft parameters was first proposed to reveal the relationship between the reaction conversion and the solvent properties, and the results suggested a solvent possessing a high polarity/polarizability and Lewis basicity is favorable for the reaction. Under the optimal conditions, 97.1% conversion of hemicellulose with 93.1% selectivity of xylooligosaccharides based on xylans could be achieved within 2 h. Qualitative high-resolution ESIMS and quantitative HPAEC analysis demonstrated the good solubility of the obtained xylooligosaccharides was ascribed to the depolymerization of hemicellulose rather than the formation of sulfonated oligosaccharides.

Automated summary

Mechanocatalytic depolymerization of hemicellulose from corncob was achieved through a weak alkali-oxidation pretreatment. The study systematically investigated the effects of impregnation solvent, acid catalyst type and dosage, and ball-milling time on the depolymerization process. A mathematical model based on Kamlet-Taft parameters was proposed to explain the relationship between reaction conversion and solvent properties. The optimal conditions resulted in high conversion of hemicellulose to xylooligosaccharides.