Fractionation of aqueous isopropanol mixtures in a countercurrent packed column using supercritical CO2

International audiencePurification of isopropanol aqueous mixtures by supercritical CO2 was realized in the continuous mode using a packed column. The aim of the study was to experimentally and theoretically evaluate the separation performance of this packed contactor. Experiments were performed in a column of 2 m height and 17 mm diameter, in the range (10–20 MPa) and (40–60 °C) with a solvent to feed ratio varying from 4 to 11. Two types of packing, spring shape packing and metallic foam, were tested. The IPA composition of the feed was varied between 5% and 60% (w/w). The experimental results were compared to simulation of the process using the process simulation software Prosim Plus. The column modelling was based on the concept of theoretical equilibrium stages. Thermodynamic behaviour of the CO2–IPA–water system under pressure was represented on the whole range of conditions corresponding to the process, using the Soave–Redlich–Kwong equation of state (SRK) modified by Boston Mathias with PSRK mixing rules and UNIQUAC activity coefficient models. This model gave the best predictions, after the twelve interaction coefficients (four for each binary subsystem) were identified from the literature equilibrium experimental data. From the modelling, rather high values of the Height of a Theoretical Stage (HETS) were obtained (larger than 1 m) and these values were shown to diminish when the IPA feed composition was increased