Impacts of temperature on evolution of char structure during pyrolysis of lignin

• Published in: The Science of the total environment Vol. 699; p. 134381
• Main Authors: Zhang, Chenting, Shao, Yuewen, Zhang, Lijun, Zhang, Shu, Westerhof, Roel J.M., Liu, Qing, Jia, Peng, Li, Qingyin, Wang, Yi, Hu, Xun
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10-01-2020
• Subjects: Biofuels; Biomass; Charcoal - chemistry; DRIFTS study of pyrolysis; Hot Temperature; Impacts of temperature; Lignin - chemistry; Pyrolysis; Pyrolysis of lignin; Structure of char; Temperature; Pyrolysis of lignin; Impacts of temperature; Structure of char; DRIFTS study of pyrolysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.134381

This study investigated the pyrolysis of lignin pyrolysis in a temperature region from 200 to 800 °C, aiming to understand influence of pyrolysis temperature on evolution of structures of the resulting char. The results showed that fusion of the ring structure initiated at 200 °C, where the C/H ratio in the char was equal to that in naphthalene (two fused rings). The C/H ratio in the char obtained at 350 °C corresponded to that in pyrene (four fused rings), while the char produced at 550 °C was equivalent to 20 fused benzene rings in terms of C/H ratio. The increasing pyrolysis temperature also shifted the oxygen-containing functionalities such as the carbonyl, esters, ketones in the bio-oil to the ether functionality that had a higher thermal stability. The DRIFTS study of pyrolysis of lignin showed that drastic changes of the functionalities and the internal structure of the char occurred in a narrow temperature region from 520 to 530 °C. The carbonyl functionality and the aliphatic structure were eliminated, and new conjugated π-bond systems formed.
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•C/H ratio in different char is equivalent to that in fused rings of varied size.•Increasing pyrolysis temperature shifted ketones, esters in bio-oil to ethers.•Tar obtained above 550 °C had a higher oxygen content but better thermal stability.•DRIFTS study shows the drastic structural changes of char occurred at 520 to 530 °C.