Levulinic acid (LA) is considered as an important intermediate for production of chemicals, resins, polymers, and fuel additives. Herein, five Brønsted–Lewis acidic ionic liquids (ILs) were synthesized and their acidities of ILs were characterized using FT-IR spectroscopy. The order of their acidic strength was similar to that of the used metal chlorides (ZnCl₂ > FeCl₃ > CuCl > CrCl₃). Cellulose was effectively converted to LA in pure water at 180 °C in 10 h without additives, and the maximum yield of LA was more than 49% over the Brønsted–Lewis IL [HO₃S-(CH₂)₃-py]Cl-FeCl₃. The synergistic catalytic effect of the Lewis and Brønsted acidic centers of the catalyst played a significant role for the conversion of cellulose to LA. Some solid residues were formed along with the synthesis of LA, and the result of its characterization suggested that they had good thermal stability and their structures were benzene or amorphous (partially hydrogenated) fused benzene ring. Otherwise, the IL reusability was good, and when it was reused for five times, its catalytic performance was not changed. Therefore, the conversion route for cellulose to LA in pure water with the Brønsted–Lewis acidic ILs provides an environmentally friendly method for biobased-platform from biomass.

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中文翻译：

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通过功能性 Brønsted–Lewis 酸性离子液体催化纤维素高效转化为乙酰丙酸

乙酰丙酸 (LA) 被认为是生产化学品、树脂、聚合物和燃料添加剂的重要中间体。在此，合成了五种 Brønsted-Lewis 酸性离子液体 (ILs)，并使用 FT-IR 光谱表征了它们的酸性离子液体。它们的酸性强度的顺序与所使用的金属氯化物相似（ZnCl ₂  > FeCl ₃  > CuCl > CrCl ₃）。纤维素在 180 °C 纯水中在 10 h 内有效转化为 LA，且无添加剂，与 Brønsted–Lewis IL [HO ₃ S-(CH ₂ ) ₃ -py]Cl相比，LA 的最大产率超过 49% -FeCl ₃. 催化剂的 Lewis 和 Brønsted 酸性中心的协同催化作用对纤维素向 LA 的转化起到了重要作用。LA的合成过程中形成了一些固体残留物，其表征结果表明它们具有良好的热稳定性，其结构为苯或无定形（部分氢化）稠合苯环。否则，IL的重复使用性良好，重复使用5次后，其催化性能没有变化。因此，使用 Brønsted-Lewis 酸性离子液体在纯水中将纤维素转化为 LA 的途径为从生物质中提取生物基平台提供了一种环境友好的方法。

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