CO2 capture performances of [Emim][Gly] ionic liquid confined into porous sorbents for post-combustion applications

The development of high-efficiency and cost-effective purification processes for CO2 capture from flue-gas is today considered mandatory to mitigate energy-related emissions. The use of ionic liquids (ILs) for post-combustion CO2 capture is a very attractive option to circumvent amine-based absorbents drawbacks. Recent literature studies suggest the use of ILs supported onto porous substrates for CO2 capture, when dealing with ILs exhibiting high viscosities and as a strategy to minimize their utilization costs. Nevertheless, most of the adsorption studies are generally performed in pure CO2 streams, not representative of a real flue-gas. This work investigates the CO2 capture of a mesoporous alumina functionalized with 1-ethyl-3-methylimidazolium glycinate ([Emim][Gly]) IL. Two sorbents were prepared by impregnation of the substrate with [Emim][Gly] in ethanol solution at two concentration values of active phase (1.08×10–2 and 2.01×10–2 kg L–1), followed by solvent evaporation. N2 pore size analysis of sorbents showed that the impregnation treatment did not significantly affect the pore size distribution of the raw support. CO2 adsorption runs on either raw or [Emim][Gly]-functionalized alumina were performed in a fixed-bed column at 303, 323, 353 and 373 K and for mimicking flue-gas streams (CO2 15% vol., balance N2). Results testified the effectiveness of the functionalization treatment with [Emim][Gly] IL which determined an increase in the parent sorbent CO2 capture capacity, mainly at lower temperatures. At 303 K, the adsorption capacity values derived for sorbents loaded with 5 and 9% wt. IL were about 35 and 60% greater than the figure obtained for raw alumina, respectively (Figure 1). Dynamic tests showed that functionalized sorbents were characterized by slower saturation kinetics. Moreover, an increase in the operating temperature determined a reduction of the saturation time, likely due to a reduction of the IL viscosity promoting faster CO2 diffusion rates within the IL film confined into the sorbent pores.