Effect of the Feedstock Type on the Volumetric Low-Pressure CO2 Capture Performance of Activated Carbons

Activated carbons (ACs) display attractive gravimetric performance for CO2 capture, but it is unclear which carbon precursor suits preparation of ACs with high adsorption performance on a volumetric basis. Thus, we prepared ACs from five feedstocks (bamboo, rice husk, peanut shell, coconut shell, and anthracite) to study impacts of the feedstock type on the densities, volumetric pore parameters, and volumetric CO2 adsorption performance of ACs. The feedstock type was found to affect tap density of ACs, mainly because ACs possessed different macropore volumes. Because of the influence of tap density, the decreasing order of ACs for volumetric pore parameters was different from that for the corresponding gravimetric parameters. When AC was expected to display a high volumetric fine micropore volume (V-<0.7 nm,V-v and V-<1 nm,V-v), its tap density and gravimetric fine micropore volume should be both high. The feedstock type affected the volumetric CO2 uptakes of ACs at 0.15 and 1 bar, mainly because it changed volumetric fine micropore volume (V-<0.7 nm,V-v and V-<1 nm,V-v). The CO2/N-2 selectivity of ACs was impacted by feedstock type, because ACs had different ultramicropore/micropore volume ratios (V-<0.7nm/V-micro) and nitrogen contents. The feedstock type also affected the volumetric CO, adsorption rate of ACs, because ACs had different volumetric micropore volumes (V-<1 nm,V-v and V-1-2 nm,V-v). Coconut shell was the most suitable feedstock for the preparation of the carbonaceous CO2 adsorbent used in the adsorption bed, because of the high volumetric CO2 adsorption capacity, superior volumetric adsorption rate, and acceptable CO2/N-2 selectivity of the yielded AC. This study showed the necessity to evaluate ACs by their volumetric CO2 capture performance and provided an effective way to tune this performance via a rational choice of carbon precursor.