Thermochemical properties of lignin extracted from willow by deep eutectic solvents (DES)

• DOI: 10.1007/s10570-019-02489-8
• Publication Date: 2019-05-09T10:27:30Z
• Authors: Gaojin Lyu; Qin Wu; Tengfei Li; Weikun Jiang; Xingxiang Ji; Guihua Yang
• Keywords: Guaiacol; Thermogravimetric analysis

In the present examination, the thermochemical behavior of the lignin extracted from willow (Salix matsudana cv. Zhuliu) by deep eutectic solvents (DES) treatment (DES-lignin) with varied times were investigated with the techniques of thermogravimetric analyzer, in situ diffuse reflectance infrared pyrolysis (in situ-FTIR), and pyrolysis–gas chromatography/mass spectrometry. The results showed that thermal degradation of DES-lignin mainly occurred at 185–470 °C with two maximum weight loss peaks at 265 °C and 380 °C respectively, and the solid residue was 40% when terminated at 800 °C. The identified cluster of aromatics from in situ-FTIR was detected earlier and stronger than those of small molecular gases, suggesting cleavage of lignin intermolecular linkages dominated the initial pyrolysis process. The DES-lignin was sensitive to pyrolysis to produce aromatics. The total phenols yield from DES-lignin pyrolysis reached a maxima of 95.1% at 450 °C, among which phenol and guaiacol accounted for the largest proportion, i.e. 20.8% and 24.2% respectively. In addition, product distribution was remarkably affected by pyrolysis temperature and the DES treatment time used for lignin isolation.