Cellulose triacetate oligomers exhibit high solubility in dense CO2

Abstract

Cellulose triacetate (CTA) is CO₂-insoluble primarily due to its crystallinity, but oligomers of CTA have been shown to be highly CO₂-soluble. These oligomers were generated via the pivalolysis of high molecular weight CTA. The resultant mixture of oligomers was fractionated with organic solvents, and the CO₂-solubility of the each fraction was determined at 300 K. The fluid phase behavior of mixtures containing CO₂ and oligo-CTA composed of one to four per-acetylated monosaccharide repeat units was determined over the 0.1–5 wt% oligo-CTA range. In this concentration range, only bubble points were observed for the monomer. Both bubble points and dew points were observed for the dimer, trimer and tetramer. At a concentration of 5 wt% of oligo-CTA, two-phase pressures of 6.14, 7.38, 9.51 and 13.24 MPa were measured for the monomer, dimer, trimer and tetramer, respectively.