J Sol-Gel Sci Technol DOI 10.1007/s10971-017-4465-1 INVITED PAPER: NANO- AND MACROPOROUS MATERIALS (AEROGELS, XEROGELS, CRYOGELS, ETC.) Experimental and thermodynamic comparison of the separation of CO 2 /toluene and CO 2 /tetralin mixtures in the process of organogel supercritical drying for aerogels production Mouna Lazrag 1,2 ● Edouard Steiner 1 ● Cécile Lemaitre 1 ● Fabrice Mutelet 1 ● Romain Privat 1 ● Sabine Rode 1 ● Ahmed Hannachi 2 ● Danielle Barth 1 Received: 25 February 2017 / Accepted: 5 July 2017 © Springer Science+Business Media, LLC 2017 Abstract An organogel is firstly prepared by synthesizing an aminoacid-type organogelator which is able to immobi- lize aromatic solvents, such as tetralin or toluene. Aerogels are obtained from organogels by extracting the solvent with a stream of supercritical CO 2 in an autoclave. The CO 2 / solvent mixture leaving the autoclave is separated in a cas- cade of three cyclone separators. The experimental results showed a good solvent recovery rate in the case of tetralin, exceeding 90%, but an unsatisfactory separation for toluene with a yield below 65%. A thermodynamic study was car- ried out to model the separation for both solvents. The Peng–Robinson equation of state with van der Waals mixing rules and temperature-dependent binary interaction coeffi- cients was selected to predict the CO 2 /solvent thermo- dynamic behavior. Measurements of isothermal bubble points of the CO 2 /tetralin system were conducted using a high-pressure variable-volume visual cell confirming the relevancy of this model. Then, the first separator was simulated as a simple theoretical equilibrium stage. Simu- lations using PRO/II software were in good agreement with experimental solvent recovery rate for both toluene and tetralin. The best operating pressure and temperature for the separation were computed by a numerical parametric study. Graphical abstract Thermodynamic study to explain theoretical recovery in organogel supercritical drying: comparison between two solvents (T=20 °C, P=50 bar). 0 20 40 60 80 100 0 0.4 0.8 1.2 1.6 2 Solvent recovery rate (%) Solvent mole fraction (%) Tetralin Toluene Keywords Organogel ● Supercritical drying ● Aerogel ● CO 2 /solvent separation ● Thermodynamic ● Phase behavior 1 Introduction Aerogels are light porous solids possessing remarkable properties, such as high porosity (>80%), low density (<0.05 g/cm 3 )[1], large specific area (>500 m 2 /g) [2], low thermal conductivity(<0.02 W/m / K) [3], and high optical transparency [4]. Owing to these properties, aerogels are suitable for many applications. Acoustic and thermal insu- lation, sensors (ultrasonic and gas) [5], catalyst and catalytic supports, absorbents, drug delivery [6], electronic devices and energy storage [7, 8] are among possible applications for these environment-friendly materials. Aerogels are * Danielle Barth danielle.barth@univ-lorraine.fr 1 Laboratoire Réactions et Génie des Procédés, Université de Lorraine, France and Laboratoire Réactions et Génie des Procédés, UMR 7274, CNRS, 1 rue Grandville BP20451-54001, Nancy, France 2 Laboratoire Génie des Procédés et Systèmes Industriels (LR11ES54), Ecole Nationale d’Ingénieurs de Gabés, Université de Gabés Avenue Omar Ibn El Khattab, Zrig Eddakhlania 6072, Tunisia