Carbon dioxide (CO2) gas is well-known as a greenhouse gas that leads to global warming. Many efforts have been made to capture CO2 from coal-fired power plants, as well as to reduce the amounts of excess CO2 in the atmosphere to around 400 ppm. However, this is not a simple task, particularly in the lower pressure region than 1000 ppm. This is because the CO2 molecule is chemically stable and has a relatively low reactivity. In the present study, the CO2 adsorption at room temperature on MFI-type zeolites exchanged with alkaline-earth-metal ions, with focus on CO2 concentrations <1000 ppm, was investigated both experimentally and by calculation. These materials exhibited a particularly efficient adsorption capability for CO2, compared with other presented samples, such as the sodium-form and transition-metal ion-exchanged MFI-type zeolites. Ethyne (C2H2) was used as a probe molecule. Analyses were carried out with IR spectroscopy and X-ray absorption, and provided significant information regarding the presence of the M2+-O2--M2+ (M2+: alkaline-earth-metal ion) species formed in the samples. It was subsequently determined that this species acts as a highly efficient site for CO2 adsorption at room temperature under very low pressure, compared to a single M2+ species. A further advantage is that this material can be easily regenerated by a treatment, e.g., through the application of the temperature swing adsorption process, at relatively low temperatures (300-473 K).
- CO adsorption at 300 K
- M-O-M (M: alkaline-earth-metal ion)
- acetylide species
- easy regeneration of the sample
- fast adsorption
ASJC Scopus subject areas
- Materials Science(all)