Evolution of the functionalities and structures of biochar in pyrolysis of poplar in a wide temperature range

This study studied the change of functionalities in the biochar formed in pyrolysis of poplar wood in a wide range of temperature. The in situ Diffuse Reflectance Infrared Fourier transform spectroscopy characterization indicated that aldehydes and ketones functionalities formation initiated at 100 °C, dominated at 300 to 500 °C. Carboxyl group was less stable than carbonyls. Cellulose crystal in poplar decomposed slightly at 300 °C and significantly at 350 °C. The temperature from 250 to 350 °C significantly affected biochar yields, while the drastic fusion of the ring structures in biochar occurred from 550 to 650 °C, making biochar more aliphatic while less more aromatic. High pyrolysis temperature also created more defective structures in the biochar and favored the absorption of the CO₂ generated during the pyrolysis. The results provide the reference information for understanding the structural configuration and evolution of the functionalities during in pyrolysis of poplar biomass.