Development of a diffusion-limited shrinking particle model of cellulose dissolution in a carbon dioxide switchable system

Abstract

A diffusion-limited shrinking spherical particle model was developed to describe cellulose dissolution in carbon dioxide switchable system (CO2-SWS) by assuming an instantaneous reaction of the CO2-SWS on the cellulose surface. CO2, the main precursor of the SWS, was mixed with 1,8-diazabicyclo [5.4.0] undec-7-ene, ethylene glycol and dimethyl sulfoxide under various operating pressures (P) and temperatures (T) to yield a CO2 switchable ionic liquid for cellulose dissolution. As dissolution proceeded, the cellulose particle radius decreased because of the disappearance of cellulose. The model–predicted diffusion coefficient (D), completed dissolution time (τ), and dissolution conversion (XC) were determined under various CO2-SWS operating conditions. The predicted τ and XC values were in good agreement with the observed results. The influence of the CO2-SWS operating conditions on the predicted numerical D, τ, and XC values were investigated using Spearman’s rho correlation. The results showed that the D values ranged from 10−20 to 10−17 m2 s−1 for the CO2-SWS–cellulose system depending on the system conditions.