Characterization of whole biomasses in pyridine based ionic liquid at low temperature by 31P NMR: An approach to quantitatively measure hydroxyl groups in biomass as their original structures

Abstract

In this study, the dissolution of biomass components-cellulose, hemicellulose, and lignin, and two whole biomasses-switchgrass and poplar in a pyridine based ionic liquid at a low temperature-50°C has been examined, which will provide an opportunity to explore the original structures of biomass components. The following phosphitylation, and 31P NMR measurement could provide quantitative results for various hydroxyl groups, including aliphatic, condensed phenolic, guaiacyl phenolic, p-hydroxyl phenyl and carboxylic hydroxyl groups in the biomass components, and whole biomass. By employing various biomass model compounds (glucose, cellotriose, and cellohexose), artificial mixtures of biomass components (cellulose, hemicellulose, and lignin), and computational simulation for the assignments by using density functional theory calculation in Gaussian, reliability and accuracy of this method have been examined as well, which indicated that this method is a reliable and accurate way to quantitatively characterize five different types of hydroxyl groups in biomass and its components.