Room Temperature CO2 Adsorption Studies Using Pure and Ionic Immobilized Zeolites

The adsorption of pure CO2 on various zeolites (NH4-Y, H-Y, Na-Y, NH4-ZSM-5, H-ZSM-5, etc.) and MCM-41 materials was studied at room temperature and in a pressure range of 1-15 bar. Of these, NH4-Y showed the highest CO2 adsorption capacity followed by Al-MCM-41. Further, five amino acid anion based ionic liquids (ILs) were immobilized on the Na-Y zeolite, and their CO2 adsorption capacity was compared with that of pure Na-Y. The FTIR spectroscopy confirms the loading of IL on the zeolite. The BET analysis revealed a significant decrease in the surface area and pore volume of the IL immobilized zeolite, and the extent of reduction depended on the IL type and its loading. The CO2 adsorption capacity of IL immobilized zeolites was observed to be less than that of pure zeolite. This could be attributed to the reduced accessibility of active sites of the base zeolite due to the partial or complete coverage of the zeolite's external and internal surface with ILs and/or due to the steric hindrance that resulted from the large molecular structures of ILs. Optimal tailoring of cation/anion of IL in terms of molecular size and functionality in conjunction with mesopore-based adsorbents can improve overall CO2 capture on IL immobilized systems by effective chemisorption (from the IL) and physisorption (from the adsorbent).