Radical footprinting and regularity revealing during the pyrolysis of technical lignins

• DOI: 10.1016/j.biortech.2022.127648
• Publication Date: 2022-07-19T06:21:06Z
• Authors: Yuyang Fan; Zhengxue Zhang; Zijun Wang; Haoyang Yu; Xiangchen Kong; Peijun Li; Ming Li; Rui Xiao; Chao Liu
• Keywords: Footprinting

Revealing radical-mediated reactions is conducive to illustrate lignin pyrolysis and achieve subsequent regulation. Three technical lignins (hot-water-extracted lignin, kraft lignin, and soda lignin) were selected in this study and pyrolyzed from 400 °C to 700 °C, and their pyrolysis radicals in both chars and bio-oils were monitored with the electron paramagnetic resonance spectrometer. Results showed that spin concentrations of char radicals had a volcanic trend against the pyrolysis temperature, and reached the maximum values at 550-600 °C. However, the contents of bio-oil radicals were low during pyrolysis at low and medium temperature, but their spin concentrations exploded abruptly over 600-650 °C. Meanwhile, the bio-oil yields were found to drop after 550-600 °C, and the three inflection temperatures for char radicals, bio-oil radicals, and bio-oil yields were perfectly matched. These findings systematically elucidated the radical regularity in technical lignin pyrolysis and fundamentally contributed to the development of radical-mediated lignin pyrolysis mechanisms.