Pyrolysis characteristics and kinetics of lignin: effect of starting lignins

ABSTRACT

To elucidate the impact of starting lignins on pyrolysis characteristics and kinetics of lignin, seven lignins were pyrolyzed on a thermogravimetric (TG) analyzer. Results show that hardwood lignins showed derivative thermogravimetric (DTG) curves with one weight loss peak, softwood lignin showed a curve with two weight loss peaks, while grass lignins showed curves with a main weight loss peak and a shoulder peak. The average apparent activation energy (E_a) obtained with Starink model-free method varied greatly across the lignins. Prepared under mild conditions, the E_a values followed the order as grass lignin > hardwood lignin > softwood lignin. The most probable mechanism functions (MPMF) determined by Coats-Redfern model-fitting method also depended upon the lignins. This work shows that the slow pyrolysis behavior of lignin and the kinetic parameters are tightly related to its structure which depended greatly upon the biomass sources and isolation methods. More weak linkage structures, like β − O − 4 linkage, ferulates, and p-coumarates, could lead to the lower activation energy.

KEYWORDS:

• Lignin
• pyrolysis
• structure
• kinetic
• thermogravimetric

Nomenclature

Table

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under Grant [51706110]; and Jiangsu Key Lab of Biomass Energy and Materials under Grant [JSBEM 202013].

Notes on contributors

Jun Hu

Jun Hureceived his PhD degree from Southeast University in 2016. He is now working as an Associate Professor in School of Energy and Mechanical Engineering, Nanjing Normal University, China. His research interest focuses on the thermochemical conversion of biomass into fuels, chemicals, and carbon materials.

Xiaoxiang Jiang

Xiaoxiang Jiang received his PhD degree from Southeast University in 2011. He is now working as a Professor in School of Energy and Mechanical Engineering, Nanjing Normal University, China. His research interests include the thermochemical conversion of biomass into fuels, chemicals, and carbon materials, and environmental pollution control.