Pyrolysis characteristics of poplar sawdust by pretreatment of anaerobic fermentation

Abstract

Pyrolysis characteristics of poplar sawdust (PS) pretreated by anaerobic fermentation were investigated by means of thermogravimetric analysis (TGA) and pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) analysis. Results indicated that with an increase of pretreatment time from 0 to 20 days, the contents of cellulose and hemicellulose decreased from 54.05 and 17.96 wt. % to 51.29 and 12.61wt. % and the contents of the extractives and lignin increased from 1.41 and 26.58 wt. % to 7.31and 28.19 wt. %, respectively. The bio-pretreatment enhanced the starting pyrolysis temperature and increased the remains at 700 °C. Distinct weight loss of cellulose between 250–350 °C were observed at the TGA curves of P5, P10 and P20. Activation energy increased from 87.90 to 103.21 kJ mol−1. The bio-oil yield and product distributions also changed. Sugars content firstly increased from 7.64 to 16.73% and then decreased to 13.70%. The content of linear carbonyls initially decreased from 12.40 to 8.64% and then increased to 14.39%. Phenols show similar changing pattern. Its content changed from 24.72 to 22.54 and then 25.03%. The contents of linear acids, linear ketones and furans decreased. The contents of laevoglucose, hydroxyl acetaldehyde and 1, 2-benzenediol in the bio-oil increased from 4.54, 10.78 and 3.07% to 12.30, 13.30 and 5.44%, respectively. This indicated the pyrolysis selectivity of PS was improved. Effects of anaerobic fermentation on wood pyrolysis behaviors were remarkably different not only from straw biomass but from that of white- and brown-rot fungi.