Hydrogen bond donor solvents such as aromatic solvents inhibit the secondary degradation of cellulose-derived primary pyrolysis products. In a previous study, we found that the formation of solid carbonized products was completely inhibited during cellulose pyrolysis in aromatic solvents, with 5-hydroxymethylfurfural (5-HMF) recovered in certain yields instead. This indicated that 5-HMF is an intermediate in cellulose carbonization. To confirm this hypothesis, the thermal reactivity of 5-HMF was investigated. At 280 °C, pure 5-HMF polymerized into a hard glassy substance through OH group elimination, but further conversion was slow. When pyrolyzed in the presence of glycerol, a model of coexisting primary pyrolysis products from cellulose, a coupling reaction proceeded. Reactions characteristic of cellulose carbonization then occurred, including the formation of acidic groups and benzene-type structures in the solid products. These results confirmed the above hypothesis. The molecular mechanism of cellulose carbonization is discussed, focusing on the crystalline nature.

中文翻译：

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羟甲基糠醛作为纤维素碳化的中间体

氢键供体溶剂如芳族溶剂抑制纤维素衍生的初级热解产物的二次降解。在之前的一项研究中，我们发现在芳香族溶剂中的纤维素热解过程中完全抑制了固体碳化产物的形成，取而代之的是 5-羟甲基糠醛 (5-HMF) 以一定的收率回收。这表明5-HMF是纤维素碳化的中间体。为了证实这一假设，研究了 5-HMF 的热反应性。在 280 ℃时，纯 5-HMF 通过 OH 基团消除聚合成硬质玻璃状物质，但进一步转化缓慢。当在甘油存在下进行热解时，甘油是一种共存的纤维素初级热解产物的模型，会进行偶联反应。然后发生纤维素碳化的反应特征，包括在固体产物中形成酸性基团和苯型结构。这些结果证实了上述假设。讨论了纤维素碳化的分子机制，重点关注结晶性质。