Pedro CARVALHO1, Liliana SILVA1
1CICECO - Aveiro Institute of Materials, Chemistry department, University of Aveiro, Aveiro, Portugal
Energy-efficient separation of gases has attracted intensive attention both in research and in industry. Among several approaches proposed for improving carbon dioxide (CO2) absorption for suitable industrial implementation, chemical absorption using amino-acid-based ionic liquids (AA-ILs) has attracted special interest because of the great affinity of the amino acid anion or cations in ionic liquids with CO2 finally contributing to high adsorption selectivity. Unfortunately, the use of AA-ILs alone presents several disadvantages that need to be addressed before their scape-up and ultimately industrial applications, as their high viscosity and regeneration energy demand, lead to high operational costs and make the process unfeasible.
Membrane-based gas separation technology through gas-liquid membrane contactors has been reported as one of the alternative methods to efficiently and economically separate carbon dioxide from the flue gas of fossil fuels combustion.
The separation of gases by membranes is more effective and energy-saving with lower production and equipment costs than some traditional gas separation methods, such as adsorption or distillation. However, most polymeric membranes suffer from the trade-off between mass transport rates and separation efficiency. Polymeric membranes show high gas permeation flux but low selectivity, and vice versa. Moreover, the membrane gas-liquid contractors based on MMMs themselves do not provide any selectivity properties but only act as a barrier for separating the liquid phase from the gas phase and provide a large gas-liquid contact area for mass transfer. To overcome such weakness, mixed matrix membranes (MMMs) can provide promising potentials in high-performance gas separation, by combining the high separation properties of the inorganic filler with the low cost and flexibility of the polymers. For filler selection, carbon sub-micro carbon capsules are promising adsorbents for gas storage and separation due to their high surface area and porosity, adjustable pore sizes, and controllable surface functionality. The use of absorbents on a membrane contactor improves the separation selectivity and the mass transfer driving force, allowing high membrane fluxes and low gas outlet CO2 concentration, highlighting the potential of the technology to take advantage of the green solvents discussed presented here.
This work focuses on the development and characterization of novel encapsulated AA-ILs-based MMMs for gas separation with high permeability and selectivity, as well as good thermal and chemical stability. The studies include fabrication and optimization of dense membranes and spinning coat of hollow fiber membranes with encapsulated amino acid-based ionic liquids, designing MMMs with goof filler/include interaction and good interfacial morphology, as well as evaluating the permeation and selectivity performance of all the prepared membranes for gas capture and separation.