Supercritical CO2 assisted strategy for acetic acid elimination from industrial cellulose acetate–water mixtures

Abstract

A critical analysis of the major steps involved in the cellulose acetate industrial process is performed, with the aim of proposing possible improvements using supercritical CO2 based sub-processes. Once highlighted the main weakness of the traditional process, related to the (i) fine modulation of the acetylation reaction to obtain 2.5 acetate, (ii) acetic acid removal from the acetic dope, and (iii) treatment of the diluted acetic acid–water solution, the most attractive alternative resulted the adoption of a supercritical antisolvent extraction (SAE) performed on the acetic dope. Operating in this way, the problems related to the use of large quantities of water to remove acetic acid from the acetic dope are resolved, since it will be directly extracted by supercritical CO2. Micro- and nanoparticles, or filaments, of cellulose acetate can be produced. Finally, an acetic acid residue of 23 ppm, in the supercritical CO2 treated cellulose acetate, confirmed the success of this alternative process configuration.