Separation of CO2/N2 mixtures by new IL/Acrylic polymer microcapsules designed by a one-step suspension-based polymerization encapsulation process

Abstract

In this study, we developed a one-step simplified suspension-based polymerization process for encapsuling ionic liquids (ILs) ([emim][TfO] and [emim][Tf2N]). Acrylic photoreactive monomers were cured using UV-365 light during the encapsulation process forming the capsule shell. The acetone extraction test confirmed IL encapsulation proving a high encapsulation efficiency for all samples (>80 %). For capsules produced with lower IL content, a homogeneous morphology was observed when compared to capsules with higher IL content. Suspension polymerization produced microcapsules presenting polynuclear morphology, as seen in TEM analysis. CO2 sorption ability and CO2/N2 selectivity of the produced capsules were superior when compared to pristine shell material. Capsule stability was proved by submitting the samples to several sorption/desorption cycles. [emim][TfO] microcapsules with low ILs concentration presented superior CO2 sorption results, 53 ± 0.9 mgCO2.g−1 (0.4 Mpa at 45 °C), and CO2/N2 selectivity, 4.5 ± 0.2, compared to [emim][Tf2N] microcapsules. The improvement in sorption capacity of [emim][TfO] microcapsules was greater than 50 % in comparison with the pristine shell material. Electronic structure modeling corroborated the experimental results proving that [emim][TfO] is better to separate CO2/N2 thanks to three electron-rich oxygens. The sorption results allied to the easiness of the process represents a significant contribution to the scientific development of a new, efficient, and simplified method for the encapsulation of ionic liquids, which can be applied in the capture of CO2 in industrial exhaust gas streams.