The mechanisms of hydrothermal deconstruction of lignocellulose: new insights from thermal-analytical and complementary studies.
The mechanisms of hydrothermal deconstruction of lignocellulose: new insights from thermal-analytical and complementary studies.
复制标题
木质纤维素的水热解构机制：热分析和补充研究的新见解。
DOI：
10.1016/j.biortech.2011.06.044
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发表时间：
2011-10
影响因子：
11.4
通讯作者：
Tucker G
中科院分区：
文献类型：
--
作者：
Ibbett R;Gaddipati S;Davies S;Hill S;Tucker G
► 热分析提供真实条件下水热反应的实时数据。 ► 根据 DSC，半纤维素水解具有较低的热函变化，但木糖降解是放热的。 ► 水热放热降解反应可能类似于早期生物质热解。 ► DMTA表明生物质中木质素的聚合结构在高温下会降解。 ► 水热反应在固体含量大于 50% 时有效。差示扫描量热法、动态机械热分析、重量分析和化学技术已被用来研究秸秆生物质的水热反应。由于半纤维素中木糖环的分解，放热降解在 195°C 以上开始，这可能类似于干生物质热解早期阶段发生的反应，尽管通过水介导在较低温度下激活。放热的温度和幅度随着酸浓度的增加而降低，表明活化能的降低和反应途径平衡的变化。自催化水解产物中木聚糖低聚物的存在被认为是由于低速率常数而不是特定的反应机制。木质素玻璃化转变的丧失表明木质素相在高温自催化条件下重组，但在较低温度酸催化条件下保持部分完整。这表明木质素降解反应是热激活的，但不能被酸水溶液有效催化。
► Thermal analysis provides real-time data on hydrothermal reactions under realistic conditions. ► From DSC, hemicellulose hydrolysis has low enthalpy change but xylose degradation is exothermic. ► Hydrothermal exothermic degradation reactions may be similar to early stage biomass pyrolysis. ► DMTA shows that the polymeric structure of lignin in biomass is degraded at high temperatures. ► Hydrothermal reactions are effective at greater than 50% solids content. Differential Scanning Calorimetry, Dynamic Mechanical Thermal Analysis, gravimetric and chemical techniques have been used to study hydrothermal reactions of straw biomass. Exothermic degradation initiates above 195 °C, due to breakdown of the xylose ring from hemicellulose, which may be similar to reactions occurring during the early stage pyrolysis of dry biomass, though activated at lower temperature through water mediation. The temperature and magnitude of the exotherm reduce with increasing acid concentration, suggesting a reduction in activation energy and a change in the balance of reaction pathways. The presence of xylan oligomers in auto-catalytic hydrolysates is believed to be due to a low rate constant rather than a specific reaction mechanism. The loss of the lignin glass transition indicates that the lignin phase is reorganised under high temperature auto-catalytic conditions, but remains partially intact under lower temperature acid-catalytic conditions. This shows that lignin degradation reactions are activated thermally but are not effectively catalysed by aqueous acid.