Equilibrium Adsorption Measurements of Pure Nitrogen, Carbon Dioxide, and Methane on a Carbon Molecular Sieve at Cryogenic Temperatures and High Pressures

A detailed experimental study of the adsorption behavior at equilibrium of pure nitrogen, methane, and carbon dioxide gases oil a commercial carbon molecular sieve (Shirasagi MSC 3K-161) is reported at temperatures between 115 K to 323 K and pressures up to 5 MPa. A volumetric-type apparatus was used to obtain over 200 excess (Gibbs) adsorption capacity data over this range of pressure and temperature with ail estimated uncertainty of 4%. The absolute adsorption isotherms were type I in the IUPAC classification with the adsorption capacity at constant pressure increasing significantly with decreasing temperature. For each gas, the adsorption data were regressed to a four parameter Toth equation to represent the temperature and pressure dependence of the data with a relative standard uncertainty of 4%. The optimized parameters from the Toth equation included the isosteric enthalpies of adsorption that were 17 kJ.mol(-1), 27 kJ.mol(-1), and 18 kJ.mol(-1) for N-2, CO2, and CH4, respectively.