Adsorption Capacity Enhancement by Activation with CO2 of Monolithic Adsorbents Made of KOH-Activated Carbon and Polymer-Derived Binder

Disc-shaped monoliths molded from KOH-activated carbon powder (AC) and novolac resin (N) or poly(furfuryl alhohol) (P) binder were activated with CO2 to open an access to the microporosity that was blocked by the binder char. The variation in the porous texture of monoliths was characterized by the N2 adsorption at 77 K and mercury porosimetry. The results show that using N allows the monoliths to be activated to a higher burnoff compared to P (30 vs 15 wt %) without noticeable loss of the integrity and mechanical strength. The increase in the surface area and micropore volume on activation is accompanied by a considerable development of meso- and macropores and a decrease in bulk density of monoliths. The behavior has been discussed as an effect of excessive reactivity to carbon dioxide of KOH-activated carbon compared to binder derived char. The preferential burnoff of accessible activated carbon particles limits the enhancement of volumetric storage capacity with activation progress of monolith. The maximum methane uptake of 10.7 mmol g–1 at 25 °C and 3.5 MPa was measured for the activated monolith made using novolac binder.