Simultaneous removal of H2S and COS using activated carbons and their supported catalysts

Adsorption and catalytic decomposition of H2S and COS were investigated over active carbons using a flow reactor with fixed bed in the temperature range from 300 to 450 °C. Active carbons removed very effectively COS at a relatively high temperature of 400 °C, some portion being decomposed to CO over active carbons. Although H2S was also removed by active carbons at 400 °C, the removal capacity of H2S was much smaller than that of COS and H2S was hardly decomposed over active carbons. The impregnation of Fe on the active carbon enhanced very much the removal of both COS and H2S; however, their decomposition behaviors were much different. It is found that the decomposition of H2S was enhanced by Fe-supported activated carbon derived from a brown coal, while no decomposition of COS took place over the same Fe-supported active carbon. These results indicate that H2S may be dominantly removed through the reaction with metal to produce metal sulfide, while COS may be preferably adsorbed as COS itself in the pore of active carbon and then may react with carbon surface to be decomposed to CO. Such contrast adsorption and decomposition behaviors of COS and H2S are discussed based on their chemical reactivity over active carbon-supported catalyst.