Significance of micropores for the removal of hydrogen sulfide from oxygen-free gas streams by activated carbon

Activated carbons are widely used adsorbents for hydrogen sulfide (H 2 S) removal in the field of gas stream purification in industry. Five commercially available wood-, coal-, and coconut shell-based activated carbons, prepared by phosphoric acid activation and steam activation, were chosen as adsorbents in an effort to elucidate the effect of the pore structure on H 2 S adsorption of activated carbons in an oxygen-free gas stream. The adsorption experiments were conducted in an adsorption column, and the breakthrough curves of the activated carbons were examined. The results showed that adsorption of H 2 S by activated carbon under oxygen-free conditions was dependent on the microporous structure, particularly micropores with sizes of <1 nm. The surface area of CS-3 is 1,792 m 2 ·g −1 . The H 2 S breakthrough capacities of WS-1, BS-1, CS-1, CS-2, and CS-3 were 0.006, 0.01, 0.018, 0.021, and 0.026 g·cm −3 under oxygen-free conditions. The adsorption experiments of the KOH- and CuO-loaded activated carbons further confirmed the significance of micropores with sizes of <1 nm for H 2 S removal. Also, it was found that pre-adsorption or co-adsorption of carbon tetrachloride led to poisoning of the activated carbon for H 2 S adsorption due to a remarkable reduction in the micropore volume. Therefore, steam-activated materials with highly developed micropore structures were favorable adsorbents for H 2 S removal because of their high adsorption capacities and reduced fire risk in an oxygen-free gas stream.