2.4. CO2 adsorption isotherms
Adsorption equilibrium isotherms for pure CO2 were measured using a magnetic suspension balance by Rubotherm (Bochum, Germany). The adsorbents were degassed in situ at 423 K (except for pristine zeolite 13X, which was regenerated 623 K) until no mass variation in the system was observed. After that, the measuring chamber was cooled down to the experiment temperature (298 or 348K) and the gas pressure (CO2) was increased stepwise (UHV until approximately 10 bar).