Novel custom gas sorption analyser for the assessment of adsorbents for CO2 capture by vacuum swing adsorption

Vacuum swing adsorption (VSA) technologies are being considered for the selective capture of CO₂ from flue gas prior to geosequestration, as a means of reducing CO₂ emissions associated with power generation. Typically the relative potential of sorbents for such processes has been determined by interpolation of measured adsorption isotherms. This approach however, is less than ideal because the isotherms do not account for the kinetic and thermal effects that may be important at short time scales (1-3 min) typically employed in VSA. A custom bench scale volumetric gas sorption analyzer (GSA) was constructed, incorporating a thermally insulated sample vessel, to mimic the poor thermal transfer to/from an industrial scale sorbent bed. This facilitates better assessment of the relative potential of different adsorbents under conditions anticipated for industrial operation. A typical amine adsorbent prepared by loading polyethyleneimine (PEI) into SBA15 mesoporous silica was found to have slower initial CO₂ sorption kinetics than commercial Zeolite 13X under realistic conditions (105°C, cycling from 0.05 to 0.15atm) despite having a larger isothermal CO₂ capacity and higher Hads(CO₂).