Thermogravimetric Analysis of Pyrolysis Characteristics of Alkali Lignin

Pyrolysis characteristics and kinetics of alkali lignin separated from kraft black liquor were studied by thermogravimetric analysis.The effect of heating rate on the pyrolysis characteristics of alkali lignin was investigated.The results showed that the non-isothermal weight-loss process of alkali lignin includes the phases of dehydration,holding,rapid weight-loss and slow weight-loss.The pyrolysis of alkali lignin is mainly in the range of 250℃and 500℃. The pyrolysis process starts earlier and then continues for quite long time.The amount of pyrolysis residue is about 30%.The pyrolysis characteristics of alkali lignin are different from that of natural lignin.The derivative thermogravimetry (DTG) curves of alkali lignin show that as temperature raising rate increases, the maximum pyrolysis rate and the temperature at which pyrolysis rate reaches maximum increase.Based on the experiment,the Coats-Redfern method was used to analyze the pyrolysis process and calculate the kinetic parameters at the different heating rate.The pyrolysis process of alkali lignin can be described with one step first-order reaction in the main pyrolysis region.