Thermal decomposition of pyrolytic lignin under inert conditions at low temperatures
Thermal decomposition of pyrolytic lignin under inert conditions at low temperatures
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DOI：
10.1016/j.fuel.2017.03.035
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发表时间：
2017-07
期刊：
影响因子：
7.4
通讯作者：
Yee Wen Chua;Yun Yu;Hongwei Wu
中科院分区：
文献类型：
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作者：
Yee Wen Chua;Yun Yu;Hongwei Wu
从生物质快速热解生成的生物油中分离出一种热解木质素，用落管/固定床反应器在100~350℃的惰性条件下进行热解。结果表明，在这种快速热解条件下，热解木质素的残炭率从100℃时的∼82%迅速下降到350℃时的∼23%，大部分失重是由于热解木质素中的轻芳烃低聚物(即CH2Cl2可溶部分)的显著减少，这种减少随着温度的升高而增加。相反，在这种低温热解过程中，热解木素焦中残留的重芳烃低聚物(即CH2Cl2不溶部分)变化不大。显然，在热解木质素的热分解过程中，轻、重芳烃低聚物之间存在强烈的相互作用，从而导致观察到的额外焦化。热解木质素在热解过程中的主要反应是脂肪族和小酚类化合物的释放(即通过脱甲基化和脱碳反应)，主要是由于热解木质素结构中的醚键断裂所致。随着温度的升高，由于高温(>；250°C)下的聚合反应增强，焦炭结构变得更芳香。
A pyrolytic lignin, separated from the bio-oil generated from biomass fast pyrolysis bio-oil at 500 °C via cold-water extraction, was thermally decomposed in a drop-tube/fixed-bed reactor under inert conditions at 100–350 °C. It is found that the char yield of the pyrolytic lignin under such fast pyrolysis conditions decreases rapidly from ∼82% at 100 °C to ∼23% at 350 °C. The majority of the weight loss is contributed by the significant reduction in the fraction of light aromatic oligomers (i.e., the CH2Cl2-soluble fraction) retained in the pyrolytic lignin chars, with such reductions increasing with temperature. On the contrary, there is insignificant change in the fraction of heavy aromatic oligomers (i.e., the CH2Cl2-insoluble fraction) retained in the pyrolytic lignin chars during pyrolysis at such low temperatures. It is evident that there are strong interactions between the light and heavy aromatic oligomers during thermal decomposition of the pyrolytic lignin, leading to the observed additional char formation. The main reactions during thermal decomposition of the pyrolytic lignin are the release of aliphatic and small phenolic compounds (i.e., via demethylation and decarbonylation reactions), mainly due to the breaking of ether bonds in the pyrolytic lignin structure. The char structure becomes more aromatic as temperature increases, due to the enhanced polymerization reactions at high temperatures (>250 °C).