Sabine Rode

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

An organogel is firstly prepared by synthesizing an aminoacid-type organogelator which is able to immobilize aromatic solvents, such as tetralin or toluene. Aerogels are obtained from organogels by extracting the solvent with a stream of supercritical CO2 in an autoclave. The CO2/solvent mixture leaving the autoclave is separated in a cascade 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 carried 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 coefficients was selected to predict the CO2/solvent thermodynamic behavior. Measurements of isothermal bubble points of the CO2/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. Simulations 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 abstractThermodynamic study to explain theoretical recovery in organogel supercritical drying: comparison between two solvents (T=20 °C, P=50 bar).

15 – Hybrid amine-based PCC processes, membrane contactors for PCC

Post-combustion carbon capture using membrane contactors is discussed in this chapter. Among membrane contactor technologies, the hollow-fiber membrane contactor (HFMC) is the most studied as it permits development of the highest interfacial areas per unit volume. The main drawback of HFMC is membrane wetting; hence, the selection of the solvent–membrane combination as well as of the operating conditions is essential to proper functioning of this technology. The modeling of HFMC is detailed and an example, CO2 capture by monoethanolamine, is illustrated and discussed. Various pilot-plant investigations are analyzed, thus sharing the current advancements and obstacles in a context close to the industrial one. Finally, the application of HFMC technology in PCC, though promising, needs more research to make it competitive with packed columns in terms of robustness and economics.