生物质三组分热裂解行为的对比研究

Pyrolysis behavior of cellulose,xylan and lignin

在热天平上对比研究了生物质中的纤维素、半纤维素和木质索三种主要组分的热失重规律。结果表明，作为半纤维索模型化合物的木聚糖热稳定性差，在217℃-390℃发生明显分解；纤维素热裂解起始温度最高，且主要失重发生在较窄温度区域，固体残留物仅为6．5％；木质索表现出较宽的失重温度区域，最终固体残留物高达42％。在红外辐射机理试验台上对比研究了三组分热裂解产物随温度的变化规律。三组分热裂解生物油产量随温度变化先升后降。纤维素生物油产量在峰值上最高，但纤维素生物油热稳定性差，高温时挥发分的二次分解最明显；木聚糖和木质素生物油产量较低，表现出较好的热稳定性。三组分热裂解焦炭产量随温度升高而降低，最终纤维素热裂解焦炭产量为1．5％，而木聚糖和木质素分别为22％和26％。三组分热裂解气体产物随温度升高而增长，但在气体组成分布上因三组分的结构上的差异而不同。

The difference of pyrolysis characteristic among cellulose, xylan and lignin was studied by TG and heat radiation reactor. Xylan has a lower thermal stability than cellulose, and decomposes at 217 ℃ -390 ℃. Cellulose has a higher onset temperature of pyrolysis and lower yield of char compared with xylan and lignin, and decomposes in a rather narrow temperature range. Lignin decomposes over a broad temperature range from 227 ℃ to 550 ℃ with a char yield of 42% which is the highest of the three fractions. The trend of bio-oil yield from the three components with temperature is the same, which increases firstly and then decreases. The bio-oil yield from cellulose is the highest of the three fractions, but it is lest stable. The bio-oil from xylan and lignin shows a higher thermal stability. The char yield for cellulose, xylan and lignin decreases with temperature rise, and finally closes to a constant value about 1.5%, 22% and 26%. The gas yield increases with temperature rise, but the contents of the gas are different according to the different fraction.