Elucidation of reactions preceding tarry material formation in hydrothermal reaction field.

在生物质超临界水气化和水热预处理过程中，加热过程中焦油状物质的生成是非常重要的，但其反应机理还没有得到充分的了解。以葡萄糖为模型化合物，在水热条件下，在管式反应器中进行反应，测定了特定温度和反应时间下果糖、赤藓糖、甘油醛、脱水葡萄糖和5-羟甲基糠醛的产率。参考文献，确定了反应网络，用最小二乘法确定了各反应的Arrhenius参数。结果表明，葡萄糖分解的反应级数随温度的变化而变化，表明主要反应路径随水热反应场的变化而变化。利用这些反应速率参数，计算了不同升温速率下的产物收率。在较低的升温速率下，5-羟甲基糠醛的产率增加。在改变加热速率的情况下进行了实验运行，并且发现当加热速率较低时，焦油状材料的产率较高。水溶性产物的分析表明，分子量约为120的化合物正在发生聚合。在以前的研究中，分子量为126的5-羟甲基糠醛被认为是产生有色产物的原因，考虑到本研究的结果，强烈建议5-羟甲基糠醛聚合有助于焦油状物质的产生。

In spite of the importance of tarry material production during heating up period in supercritical water gasification and hydrothermal pretreatment of biomass, the reaction mechanism is not sufficiently understood. In this study, glucose was selected as a model compound, reaction was made to proceed in tubular reactors under hydrothermal conditions, and yield of product compounds including fructose, erythrose, glyceraldehyde, anhydroglucose, and 5-hydorxymethylfurfuraol were determined for specific temperature and reaction time. Referring previous literatures, reaction network was determined, and Arrhenius parameters of each reaction were determined by the least-square method. As a result, reaction order for glucose decomposition was found to change with temperature, indicating main reaction paths to change with hydrothermal reaction field. With these reaction rate parameters, yield of products for different heating rate was calculated. For a lower heating rate, the yield of 5-hydroxymethylfurfural increased. Experimental runs were conducted where heating rate was changed, and it was found that when heating rate is lower, the higher was the yield of tarry material. Analysis of water-soluble products indicated that polymerization of a compound whose molecular weight was around 120 was taking place. In previous studies of heating sugars, 5-hydroxymethylfurfural, whose molecular weight is 126, has been nominated as a cause of colored product, and consideration with the result of this study, it is strongly suggested that 5-hydroxymethylfurfural polymerization contributes to the production of tarry materials.