关键词: 毛竹, 纤维素, 半纤维素, 木质素, 热重-红外联用, 半定量

Abstract:

Objective: In order to provide guidance and reference for the pyrolysis and utilization of bamboo to become high-quality gas fuel and carbon materials, the pyrolysis properties of the cellulose, hemicellulose and lignin extracted from bamboo fiber and parenchyma under different pyrolysis conditions were explored. The effects of pyrolysis process on solid residues and volatiles composition were analyzed to provide technical guidance for the development of clean and efficient gradient carbonization and physical activation processes. Method: The pyrolysis characteristics and relative gas content of 3-year-old moso bamboo powder, bamboo fiber and parenchyma separated by water separation and three main components extracted by chemical method were analyzed semi quantitatively by TG-FTIR at heating rates of 10, 20 and 30 ℃·min^?1. Result: Under 10 ℃·min^?1 and N₂ atmosphere, the main pyrolysis stage of bamboo powder, bamboo fiber and parenchyma were 180-400 ℃, and the final solid residues were 19.8%, 21.3% and 17.5%. The main pyrolysis stages of cellulose, hemicelluloses and lignin in bamboo fiber and parenchyma occurred at 250-400 ℃, 190-365 ℃ and 100-500 ℃ respectively. The solid residues of cellulose, hemicelluloses and lignin in the two cells were 9.9% and 6.3%, 20.2% and 18.3%, 30.4% and 25.8%. TG-FTIR analysis showed that the gases produced by pyrolysis of all samples were mainly composed of CO₂, CO and CH₄. The highest relative content of functional group compounds such as C=O and C—O—C in cellulose pyrolysis products was 65.8%. The highest relative content of CO₂ in hemicelluloses was 42.7%. The content of combustible gas (CH₄, CO) in the gas products of lignin was the highest, which was 27.3%. With the increase of heating rate, the relative content of functional group compounds such as C=O and C—O—C in cellulose pyrolysis products and syngas in lignin decreased by about 5%, and the content of CO₂ in hemicellulose increased by nearly 10%. Conclusion: 1) Bamboo powder, different types of cells and their three components had different pyrolysis characteristics. The solid residue of parenchyma-cellulose was the lowest and that of fiber-lignin was the highest. 2) The pyrolysis gas composition types of bamboo powder, bamboo fiber and parenchya and three main components were basically the same, but the relative contents were obviously different. The main gas products of the cellulose pyrolysis were compounds containing C=O and C—O—C functional groups, the main products of hemicellulose pyrolysis were CO₂ and compounds containing C=O functional groups, and the main products of lignin pyrolysis were CO₂ and compounds containing C—O—C functional groups. 3) With the increase of heating rate, the TG/DTG curves of bamboo powder, different types of cells and three main components moved to the high temperature side as a whole. The FTIR absorption peak intensity of pyrolysis gas products increased, in which the relative content of CO and compounds containing C=O functional groups decreased gradually.

Key words: moso bamboo, cellulose, hemicelluloses, lignin, TG-FTIR, semi quantitative calculation