Masoud Mofarahi

Resin-based activated carbon beads through KOH activation (KRACs; 400–450 μm) were studied to elucidate the role of ultra-micropores in CO2 adsorption and separation. The improved textural properties resulted in an enhancing CO2 adsorption of 55.4% (10.0 wt % at 303 K and 101.3 kPa), showing excellent cyclic stability. The change in CO2 adsorption capacity correlated well with ultra-micropore properties. However, it was noteworthy that excessive developed ultra-micropores reduced the CO2 adsorption rate. In the breakthrough experiments using CO2/N2 and CO2/CH4 mixtures, KRAC with the most developed ultra-micropores showed the highest CO2 adsorption capacity, but the tailing was higher. As CO2 concentration increased in the CO2/N2 mixture, the difference in adsorption capacity from other KRACs was highly reduced. Furthermore, the breakthrough time of the KRAC in the CO2/CH4 mixture was even shorter than other KRACs due to the preoccupied CH4 despite the highest adsorption capacity of CO2. The ultra-micropores should be carefully controlled for separation efficiency, considering adsorbates in mixtures