Homogeneous Esterification Mechanism of Bagasse Modified with Phthalic Anhydride in Ionic Liquid, Part 3: Structural Transformation of Lignins

Abstract

The phthalation of bagasse was investigated comparatively with the three main isolated components in 1-allyl-3-methylidazium chloride (AmimCl) to reveal the reaction behavior of bagasse. In the first two parts, the detailed changes of cellulosic and hemicellulosic components in bagasse were elucidated during phthalation. In Part 3, the phthalation of lignins was performed in AmimCl with various ratios of phthalic anhydride/lignins from 10 to 50 mmol/g. The phthalation degree ranged from 41.1% to 68.8% for the phthalated lignins. The aliphatic hydroxyls of lignins were more easily phthalated than the phenolic hydroxyls as revealed by 31 P nuclear magnetic resonance (NMR) analysis. Fourier transform infrared spectroscopy (FT-IR) and two dimensional (2D) heteronuclear single quantum correlation (HSQC) confirmed the attachment of phthaloyl group onto lignins. Severe degradation of lignin macromolecules was found at high ratios of phthalic anhydride/lignins (30 to 50 mmol/g) by gel permeation chromatography (GPC) analysis. These results provide a detailed understanding of reaction behaviors of lignins during bagasse phthalation, which are beneficial to prepare composites based on phthalated lignocellulose with better properties.

A Feasible Way to Produce Carbon Nanofiber by Electrospinning from Sugarcane Bagasse

“…The insolubility of lignocellulose in the conventional solvents is the biggest obstacle for its application on electrospinning [18]. The solubility of lignocellulose was improved for the direct utilization of all components after derivatization, especially the esterification reaction [18][19][20]. In general, the esterification reaction of lignocellulose is mainly divided into heterogeneous and homogeneous processes [18,20].…”