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Per-O-acylation of xylan at room temperature in dimethylsulfoxide/N-methylimidazole

Authors
  • Zhang, Xueqin1
  • Zhang, Aiping2
  • Liu, Chuanfu1
  • Ren, Junli1
  • 1 South China University of Technology, State Key Laboratory of Pulp and Paper Engineering, Guangzhou, 510640, People’s Republic of China , Guangzhou (China)
  • 2 South China Agricultural University, College of Materials and Energy, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, Guangzhou, 510642, People’s Republic of China , Guangzhou (China)
Type
Published Article
Journal
Cellulose
Publisher
Springer-Verlag
Publication Date
Jul 15, 2016
Volume
23
Issue
5
Pages
2863–2876
Identifiers
DOI: 10.1007/s10570-016-0997-8
Source
Springer Nature
Keywords
License
Green

Abstract

The per-O-acylation of xylan-type hemicellulose was firstly carried out in dimethylsulfoxide/N-methylimidazole (DMSO/NMI) at room temperature without additional catalyst. The optimum conditions for esterification of xylan was investigated in terms of the molar ratio of reagents to anhydroxylose units (AXU) in xylan and the kinds of esterification reagents to obtain a high degree of substitution (DS, 1.98) and weight percent gain (WPG, 86.88 %) of xylan esters. In this solvent system, NMI acted as a solvent, a base and an excellent catalyst, therefore, the per-O-acylation of xylan (DS of 1.98) was readily accomplished in DMSO/NMI system at room temperature. Structure elucidation of xylan esters was characterized by FT-IR and NMR (1H-NMR, 13C-NMR and HSQC). FT-IR and NMR analyses provided the direct evidence of per-O-acylation of xylan under the given conditions. Furthermore, HSQC revealed the higher reactivity of hydroxyls at C-2 position than those at C-3 position of xylan. The solubility of xylan in DMSO, DMF and CHCl3 improved after esterification. TGA/DTG indicated that the thermal stability of xylan increased after the esterification with anhydrides, while decreased with acyl chlorides, probably due to degradation and hydrolysis of the acylated xylan at the presence of by-product hydrochloric acid.

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