Impregnation of ionic liquids in mesoporous silica using supercritical carbon dioxide and co-solvent

Abstract

Ionic liquids (ILs) have been considered to be attractive alternatives for CO₂ capture. The impregnation of ILs on porous substrates can significantly reduce the ILs consumption, enhance the mass transfer of CO₂ in the ILs and make their recycling easier. However, due to the high viscosity of the ILs, the impregnated ILs were often poorly dispersed on the substrates or blocked the nanochannels when the traditional impregnation method was used. In this study, a new, effective and environmentally benign technique to impregnate ILs onto mesoporous substrates was proposed. The impregnation of [Bmim]BF₄ on SBA-15 was successfully achieved using supercritical carbon dioxide (scCO₂) as the solvent and methanol as co-solvent. The ILs were proved to be impregnated into the nanochannels rather than on the outside of the substrate by N₂ adsorption–desorption and SEM analysis. The operating pressure, temperature and time were investigated to find out the optimum parameter to synthesis these nanocomposites. Finally, the CO₂ adsorption capacity of the ILs@SBA-15 composites was performed on a dynamic adsorption apparatus.