Cellulose acetate (CA) is a resin derived from biomass. In addition to its various superior properties, CA is preferable to existing petroleum-derived resins from the viewpoint of green chemistry. Therefore, the acetylation of cellulose is one of the most important subjects in cellulose research. In this study, we found that the acetylation of cellulose could proceed in some protic ionic liquids (PILs) composed of amidine and acetic acid with ΔpK_a = ca. 8.4–8.7 under mild conditions without any catalyst. The degree of substitution (DS) of the produced CA was above 1.84, and the maximum DS was 2.87 when the ΔpK_a of the PIL was about 8.5. In propionate-based PILs, cellulose was not only acetylated but also propionated; however, the cellulose acetylation did not occur in formate-based PILs. It was revealed that the esterification of cellulose proceeded through the anion exchange between carboxylic anhydride and anion species of the PIL.

中文翻译：

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溶解纤维素的质子离子液体作为纤维素直接酯交换反应的低成本催化剂

醋酸纤维素（CA）是衍生自生物质的树脂。从绿色化学的观点来看，CA除了具有各种优异的性能外，还优于现有的石油衍生树脂。因此，纤维素的乙酰化是纤维素研究中最重要的课题之一。在这项研究中，我们发现，纤维素的乙酰化可以在脒和乙酸与ΔP组成一些质子型离子液体（比尔森）进行ķ_一个=约 8.4–8.7，在温和条件下，无任何催化剂。取代的（DS）所产生的CA度为1.84以上，并且最大DS为2.87，当ΔP ķ_一个的PIL约为8.5。在基于丙酸酯的PIL中，纤维素不仅被乙酰化，而且还被丙酸酯化。然而，在基于甲酸酯的PIL中没有发生纤维素乙酰化。揭示了纤维素的酯化是通过羧酸酐和PIL的阴离子种类之间的阴离子交换进行的。