Cellulose-dissolving protic ionic liquids as low cost catalysts for direct transesterification reactions of cellulose

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 20; no. 6; pp. 1412 - 1422
• Main Authors: Hanabusa, Hideki, Izgorodina, Ekaterina I., Suzuki, Shiori, Takeoka, Yuko, Rikukawa, Masahiro, Yoshizawa-Fujita, Masahiro
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2018
• Subjects: Acetic acid; Acetylation; Anhydrides; Anion exchange; Anion exchanging; biomass; Catalysis; Catalysts; cellulose; Cellulose acetate; Cellulose esters; Cellulose propionates; Cellulosic resins; Esterification; Green chemistry; Ionic liquids; Ions; Propionic acid; Resins; Solvents; Transesterification
• ISSN: 1463-9262; 1463-9270; 1463-9270
• DOI: 10.1039/C7GC03603E

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 Δp K 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 Δp K 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.