Thermodynamic Assessment of the Partitioning of Acetone between Supercritical CO2 and Polystyrene Using the Polar PC-SAFT Equation of State

Ali A. AlHammadi,Mohammed I. L. Abutaqiya

doi:10.1021/acsomega.0c04487

Abstract

Supercritical carbon dioxide (scCO2) has gained considerable attention in the process industry due to its favorable economic, environmental, and technical characteristics. Polymer processing is one of the key industrial applications where scCO2 plays an important role. In order to be able to efficiently design the polymer processing equipment, understanding the phase behavior and partition of solutes between scCO2 and polymers is necessary. This paper investigates the partitioning of acetone – a conventional polar cosolvent – between scCO2 and polystyrene – a glassy polymer. We highlight the importance of taking into account the polar interactions between acetone molecules and their role in the polymer phase behavior. The system is modeled under a wide range of temperatures and pressures (278.15–518.2 K and 1.0–20.0 MPa) using the polar version of the perturbed chain statistical associating fluid theory (polar PC-SAFT) equation of state. The results show that at relatively low pressure, the system exhibits a vapor–liquid–liquid (VLL) three-phase region bounded by two two-phase regions (VL and LL). At high pressure, VLL and VL regions disappear and only the LL region remains. The temperature effect is more interesting, showing a transition of upper critical solution temperature behavior to lower critical solution temperature behavior at 10 MPa and 398.15 K. It is found that neglecting the polar term can lead to significant changes in the description of the polymeric-system phase behavior especially at lower temperatures. No such differences are observed at higher temperatures (above 500 K) where the effect of polar interaction is considerably weaker.

Highlights

The special characteristics of supercritical carbon dioxide, such as nontoxicity, chemical inertness,[1] high diffusivity, and considerable solvation power,[2] have allowed its wide application in the chemical and processing industry
The system of solute−polymer in compressed carbon dioxide was found to be of interest as it is important to understand how the solute will partition between compressed carbon dioxide and polymer-rich phases for the efficient design of polymer separation and extraction processes
PC-statistical associating fluid theory (SAFT) can capture the experimental data with reasonable accuracy and an average absolute percent deviation (AAPD%) of around 5−10%

Summary

Introduction

The special characteristics of supercritical carbon dioxide (scCO2), such as nontoxicity, chemical inertness,[1] high diffusivity, and considerable solvation power,[2] have allowed its wide application in the chemical and processing industry. These processes include particle formation, reaction,[3] fractionation,[4] purification, extraction, drying,[5] blending, foaming,[6] and developing polymer complexes.[7−9] In many cases, practical applications of scCO2 have been studied and realized.[10,11]. Knowledge of phase behavior conditions is key for fine tuning the solute amount partitioned and diffused between the swollen-polymer phase and the fluid phase.[14]

Methods

Results

Conclusion