Direct Evidence of Carbon Dioxide Sorption on Argonne Premium Coals Using Attenuated Total Reflectance−Fourier Transform Infrared Spectroscopy

The direct interaction between CO 2 and two Argonne Premium Coals [Pocahontas No. 3 (low-volatile bituminous) and Beulah-Zap (lignite)] was probed by use of attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy at 328 K and pressures up to 8.0 MPa. Sorbed CO 2 on Argonne Coals was detected at 2335 cm - 1 for Beulah-Zap coal and 2332 cm - 1 for Pocahontas No. 3 coal. The energy of adsorption (18.8−20.5 kJ/mol), estimated from the Langmuir equation, was consistent with physisorption. The spectral data indicated that only one type of site was available for sorption. No evidence could be found for specific interactions between CO 2 and oxygen functional groups in the coals. The CO 2 −coal sorption isotherm was derived without estimating the CO 2 compressibility and adsorbed layer density, both of which are needed in manometric techniques.