Density and viscosity of glycerol acetates + CO2 mixtures at high pressure

MARIANA FORTUNATTI-MONTOYA; PABLO E. HEGEL; SELVA PEREDA

Campinas

Congreso; V Iberoamerican Conference on Supercritical Fluids (Prosciba); 2019

UNICAMP

Glycerol acetates are high-added value glycerol derived biosurfactants that findapplications in different industrial sectors. Previous studies show the supercritical CO2technology has a great potential for the fractionation of these highly viscous and nonvolatile products (mono, di, and triacetyl glycerol) according to the quality standards ofthe food and cosmeceutical sectors. A proper design of fractionation columns requires arobust thermodynamic model for phase equilibrium and PVT predictions, as well as ofproper correlations for physical properties like viscosity to carry out a good assessmentof the mass transfer problems to estimate the height of theoretical stages.Physiochemical properties of these multicomponent mixtures are difficult to predict dueto the complex nature of the system. Thus, in this work, we determine experimentallythe density and viscosity of CO2 saturated glycerol acetates mixtures at differentpressures (30 bar to 150 bar), temperatures (25 °C to 50 °C) and CO2 concentrations (30mol % to 70 mol %). Operating conditions were selected based on phase equilibriumpredictions with the GCA-EOS of a high-pressure fractionation column. First, a variablevolume equilibrium cell is used to measure bubble points and saturated liquid molarvolumes of glycerol acetates + CO2 mixtures. Thereafter, a high-pressure falling balltype viscometer is used to determine the dynamic viscosity of saturated liquid mixturesin the same range of pressure, temperature and CO2 concentrations. As expected,temperature and CO2 concentration has a significant effect on both density and viscositymeasurements. The measured molar volumes are between 70 cm3/mol and 130 cm3/mol,while the viscosities are between 5 mPa.s and 20 mPa.S, according to CO2concentration and temperature.