Fractionation of glycerol acetates with supercritical carbon dioxide

Abstract

Glycerol acetates are sustainable products that exhibit several industrial applications. These compounds are traditionally synthesized by the esterification of glycerol with acetic acid, and their fractionation is key to isolate high value-added products. The supercritical fractionation of glycerol acetates is an interesting alternative to separate these low volatile viscous mixtures efficiently at low temperatures to avoid thermal degradation. We evaluate the fractionation using CO2 as solvent, based on a previous study with a predictive thermodynamic model (GCA-EOS), since there is a lack of experimental equilibrium information, especially for mono and di-acetin. The group contribution approach of GCA-EOS allows predicting the phase behavior of these two compounds based on a model tuned with data available for glycerol and triacetin, as well as phase equilibrium data of low molecular weight alcohols and esters. In this work, the model is validated against new experimental fractionation data carried out in a batch high-pressure cell at temperatures between 301 K and 323 K and pressures between 100 bar and 130 bar. The predictions are in good agreement, with the experimental data, proving that GCA-EOS is a reliable tool for the design and scale-up of the high-pressure fractionation technology under study, which is also one of the aims of this work.