Amino acid ionic liquid-modified mesoporous silica sorbents with remaining surfactant for CO₂ capture

An amino acid ionic liquid (AAIL) was immobilized into a few kinds of mesoporous silica supports, namely MCM-41 and SBA-15, calcined or not calcined by an impregnation method. 1-Ethyl-3-methylimidazolium lysine ([EMIM][Lys]) was synthesized and employed as an AAIL. CO₂ adsorption experiments were then carried out using the [EMIM][Lys]-loaded mesoporous silica sorbents. Although the as-prepared supports not calcined, denoted as MCM-41-SA and SBA-15-SA, themselves did not adsorb CO₂ almost at all, these supports led to higher CO₂ adsorption capacities of the supported [EMIM][Lys] sorbents than the counterparts calcined, because of the remaining surfactant in the supports. In contrast to the improved adsorption performances for supported AAIL sorbents, the remaining surfactants did not enhance the regeneration performances in cyclic CO₂ adsorption–desorption. Pore-expanded SBA-15 (PE-SBA-15) was also synthesized and used as a support to see the effect of pore-expansion of support on CO₂ adsorption by the AAIL-loaded sorbents, not only the remaining surfactant. The calcined PE-SBA-15 caused greater capacities than the calcined SBA-15 at any [EMIM][Lys] loadings, displaying that pore-expansion can also improve the CO₂ adsorption performances. On the other hand, PE-SBA-15 not calcined (PE-SBA-15-SA) did not result in higher capacities of the sorbents than the counterpart calcined, in contrast to SBA-15-SA and MCM-41-SA. Thus, a synergetic effect by combination of the remaining surfactant and pore-expansion of support was not seen on the CO₂ adsorption of supported AAIL sorbents.