Cellulose acetate is one of the most important cellulose derivatives and is produced commercially primarily using the acetic acid process, in which superstoichiometric amounts of acetic anhydride and concentrated acetic acid are used to obtain cellulose triacetate. A subsequent partial hydrolysis is necessary in order to obtain uniformly substituted cellulose acetates with a lower degree of substitution. Homogeneous acetylations in ionic liquids or other cellulose solvent systems often offer milder conditions and the possibility of a one-step synthesis of cellulose acetates with a lower degree of substitution by simply adjusting the equivalents of the acetylating agent. Here we show an efficient homogeneous cellulose acetylation process without an additional catalyst or activation step using the DBU / CO2-switchable solvent system. Vinyl acetate was used as a more harmless acetylating agent under mild conditions, and the ease of recycling of all components used has been demonstrated with high recycling rates (87.0–98.9%). Less degradation of the cellulose framework compared to a cellulose acetate sample synthesized by the acetic acid process from the same cellulose source was shown by size exclusion chromatography (Mn = 35 kDa versus 12 kDa), which led to improved mechanical properties of solvent-cast films. Other homogeneous processes described so far (e.g. in ionic liquids) achieved lower degrees of substitution, required additional catalysts, proved to be less advantageous with regard to recycling or required more reactive acetylating agents. Our results thus show a cellulose acetylation method with a full focus on sustainability, efficiency and applicability, which leads to an E-factor of 1.92 for the overall process.

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