Adsorption of carbonyl sulfide on modified activated carbon under low-oxygen content conditions

Activated carbon sorbents impregnated with KOH, Fe(NO3)3, Cu(NO3)2, Zn(NO3)2 or Co(NO3)2 and their applications in catalytic oxidation reaction of COS were investigated. The results showed that the activated carbon modified with 10 % (mass percentage) KOH enhanced the adsorption ability significantly. And it was also found that the oxygen content and temperature were the two most important factors in the COS adsorption. Further investigation on the pore structures of the samples with X-ray photoelectron spectroscopy indicated that an adsorption/oxidation process happened in the KOH modified activated carbon in which the major existing forms of sulfur were SO4 2− and S species. The oxidation of COS suggested that KOH in the micropores may play a catalytic role during the adsorption. On the other hand, we found that the desorption activation energy from KOHW was higher than that from AC by the CO2-TPD spectra, which indicated the adsorption of CO2 on KOH impregnated activated carbon was stronger. The strong adsorption could be attributed to the basic groups on the activated carbon surface. In conclusion, the activated carbon impregnated with KOH promises a good candidate for COS adsorbent.