Reaction Behaviors of Bagasse Modified with Phthalic Anhydride in 1‐Allyl‐3‐Methylimidazolium Chloride with Catalyst 4‐Dimethylaminopyridine

Abstract

The modification of lignocellulose with cyclic anhydrides could confer stronger hydrophilic properties to lignocellulose, which could be used in many industrial fields. To elucidate the modification mechanism of lignocellulose, bagasse was phthalated comparatively with its three main components in 1-allyl-3-methylimidazolium chloride (AmimCl) using 4-dimethylaminopyridine as catalyst and phthalic anhydride as acylation reagent in the present study. From FT-IR and 2D HSQC analyses, the skeleton of bagasse and the fractions were not significantly changed during phthalation in AmimCl. 2D HSQC results suggested that the reactive hydroxyls in bagasse were partially phthalated, and the reactivity of the hydroxyls in anhydroglucose units followed the order C-6 > C-2 > C-3. Similarly, the reactivity order of hydroxyls in anhydroxylose units was C-2 > C-3. For lignin, the predominant diesterification occurred during the homogeneous modification, and both aliphatic and aromatic hydroxyls were phthalated. The reactivity order of phenolic hydroxyls was S-OH > G-OH > H-OH, which was distinct from that without catalyst. In addition, it was found that the thermal stability of phthalated bagasse was affected by the disruption of cellulose crystallinity and the degradation of components. The thermal stability of the phthalated bagasse decreased upon chemical modification and regeneration.

Structural Changes of Bagasse dusring the Homogeneous Esterification with Maleic Anhydride in Ionic Liquid 1-Allyl-3-methylimidazolium Chloride

“…Determination of the Percentage of Substitution (PS). The theoretical hydroxyl contents of unmodified cellulose and hemicelluloses were calculated, according to the reported literature [ 32 ], and the substituted hydroxyl contents of the maleated bagasse, cellulose, and hemicelluloses were determined by the back-titration method [ 32 ].…”

“…The theoretical hydroxyl content of unmodified bagasse was calculated according to the reported literature [ 32 ]. The PS of sample was calculated based on Equation (2).…”

Esterification Mechanism of Bagasse Modified with Glutaric Anhydride in 1-Allyl-3-methylimidazolium Chloride

“…Cellulose, hemicelluloses and lignin were isolated from the extractive-free bagasse, as per our previous publication [ 37 ].…”

“…According to our previous report [ 37 ], the back-titration method were used to determine the substituted hydroxyl contents of bagasse, cellulose, and hemicelluloses samples, and the theoretical hydroxyl contents of unmodified bagasse, cellulose, and hemicelluloses were 14.30, 18.52, and 15.15 mmol/g.…”

“…The physic-chemical properties of samples were characterized with FT-IR (Bruker, Karlsruhe, Germany) and NMR ( 1 H NMR, 13 C NMR and 1 H- 13 C HSQC NMR, Bruker Advance III 600M, Bruker, Karlsruhe, Germany), as the previous literature [ 37 ].…”