Enhancing capacity of activated carbons for hydrogen purification

The commercial technology for the separation of off-gases from steam methane reforming is pressure swing adsorption (PSA). To improve the performance of the PSA units, materials with enhanced capacity toward contaminants are required. In this work, a commercial activated carbon (AC) was used for the preparation of a new material with enhanced capacity toward contaminants (CO2, CH4, CO, and N2). Different samples were prepared by physical activation with CO2under different operating conditions. The conditions where the sample with the highest microporosity was obtained were reproduced to prepare a scale-up of 400 g. Carbon dioxide, hydrogen, methane, carbon monoxide, and nitrogen adsorption equilibrium and kinetics were studied on the modified AC and compared to the original AC results. An improvement of CO2 adsorption capacity of 17.5% was observed at 303 K and 7 bar. Carbon dioxide micropore diffusivity of same order of magnitude (Dc/rc 2 ) ∼4 × 10 -2 s-1 at 303 K) was observed for both adsorbents. Finally, ternary breakthrough curves (CO2-H2-CH 4) were performed for the validation of the multicomponent adsorption equilibrium. © 2009 American Chemical Society.