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 and V
<1 nm,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 and V
<1 nm,v). The CO2/N2 selectivity of ACs was impacted by feedstock type,
because ACs had different ultramicropore/micropore volume ratios (V
<0.7 nm/V
micro) and nitrogen contents. The feedstock type also affected the volumetric
CO2 adsorption rate of ACs, because ACs had different volumetric
micropore volumes (V
<1 nm,v and V
1–2 nm,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/N2 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.
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