On the mechanism of hydrogen sulfide removal from moist air on catalytic carbonaceous adsorbents

Five carbonaceous adsorbents were studied as media for H2S removal from the gas phase. Materials were characterized using nitrogen adsorption, thermal analysis, XRF, and other standard methods. Hydrogen sulfide removal capacities were measured using the ASTM test. Then the species adsorbed/formed on the carbon surfaces were identified. The results showed that surface chemical features have a significant effect on the performance of materials as H2S adsorbents. To be adsorbed, hydrogen sulfide has to be oxidized to either elemental sulfur or sulfuric acid. The amount adsorbed and the extent of oxidation are governed by the surface pH and the dispersion of catalytic centers. Such centers can be nitrogen-containing basic groups and metals (iron and alkali and alkaline earth metals). A high volume of small micropores is also important. Contributing to a high dispersion of catalyst and providing adsorption centers for storage of oxidation products, these pores form specific oxidation microreactors.