Study on carbonization of lignin by TG-FTIR and high-temperature carbonization reactor

Biomass charcoal is dominantly made from lignin. It is necessary to study lignin carbonization process to improve the quality of biomass charcoal. A Thermo-Gravimetric Analyzer coupled with a Fourier Transform Infrared Spectrometry (TG-FTIR) was applied to investigate the kinetics of lignin carbonization. Three mass loss stages (drying, pyrolysis and carbonization) were observed below 900 degrees C and another stage (structural rearrangement stage) with a slight mass loss was noticed between 900 and 1200 degrees C. Charcoal obtained at different temperatures was analyzed by FTIR to track the variation of functional groups. The pyrolysis of lignin started at 200 degrees C and charcoal was initially formed till 500 degrees C together with the intensive evolution of volatiles including various phenyl compounds. Amorphous carbon was formed between 500 and 900 degrees C, while most benzene rings structures were transformed into aromatic structures with emission of CO. When the temperature increased from 900 degrees C to 1400 degrees C, most C=C bonds were cleaved and a new charcoal structure, between amorphous carbon and graphite structures, was probably formed. The activation energies of the above three stages were estimated to be 54 kJ/mol, 70 kJ/mol and 178 kJ/mol. (c) 2012 Elsevier B.V. All rights reserved.