Promoting effect of Fe/La loading on γ-Al2O3 catalyst for hydrolysis of carbonyl sulfur

Catalytic hydrolysis of carbonyl sulfur (COS) from blast furnace gas is one of the keys to achieving ultra-low emission in the iron-steel industry. To improve the COS hydrolysis activity on gamma-Al2O3 catalyst at low temperature, catalysts with Fe or La as the active component were prepared by the impregnation method, the physical and chemical properties of the catalyst were characterized by ICP, XRF, XRD, BET, and TPD. The hydrolysis activity of COS and sulfur resistance ability on various catalysts were investigated in a fixed bed reactor combined with gas chromatography. The results show that the addition of Fe or La improves the COS hydrolysis activity due to the increase in alkaline sites on the catalyst surface. The roles of various alkaline sites on catalysts have been recognized. The weak alkaline center is the reaction site of COS hydrolysis, the middle and strong alkaline centers are the adsorption and oxidation sites of H2S. The Fe/Al2O3 catalyst has higher hydrolytic activity and oxidative capacity for H2S removal due to forming more sulfate species on Fe. The La/Al2O3 catalyst has higher hydrolysis efficiency in that H2S rapidly desorbs from the catalyst surface to the gas phase, and then, the activity of reaction sites is recovered. This provides an idea for the preparation of sulfur-resistant catalysts.