Preparation of porous carbons with high low-pressure CO_2 uptake by KOH activation of rice husk char

摘要

Porous carbons for CO_2 capture at low pressures were prepared by KOH activation of rice husk char. Low activation temperature (640-710℃) and small KOH/char ratio (1:1) favored the increase in low-pressure CO_2 uptake. The CO_2 uptakes at 0.1 bar (0℃) reached 2.11 mmol/g, which were probably the highest value ever reported for porous carbons prepared from lignocellulosic biomass. The high CO_2 uptakes at low pressures were ascribable to the presence of micropores (＜0.7 nm or ＜1 nm), the narrow micropore size distribution, or the existence of nitrogen. The obtained porous carbons also exhibited a large CO_2 uptake at 1 bar (6.24 mmol/g at 0℃) and good CO_2-over-N_2 selectivity. No noticeable change in CO_2 uptake was observed after five successive runs of adsorption-desorption. The excellent recyclability, high CO_2 uptakes, and good selectivity show that high-performance porous carbons for capturing CO_2 at low pressures can be prepared by KOH activation of rice husk char.