Direct oxidation of hydrogen sulphide to sulphur using impregnated activated carbon catalysts

Abstract

Low concentrations of H2S were directly oxidized to sulphur and small quantities of SÛ2, over seven different activated carbons with or without impregnation. The effectiveness of virgin activated carbon was tested at 175° C, 700 kPa, and O2/H2S ratio with 5% greater than stoichiometry. The conversion of H2S was 99.9 mol% with SO 2 production of 3-6%, for 360 min runtime for Fisher coconut shell activated carbon and 648 min for Envirotrol bituminous (EB) activated carbon. Then the activated carbons became deactivated due to deposition of sulphur on the surface. Under these conditions mesoporous activated carbons such as EB and Hydrodarco had the longest breakthrough time. The addition of 5.5 wt% ammonium iodide, potassium iodide and potassium carbonate individually to EB decreased the production of SO2 while having minimal effect on the overall H2S conversion. The addition of 5.5 wt% NH4I decreased the average SO2 production from 2.5% to 0.9%. The activation energy for the H2S oxidation on the 5.5 wt% Nh4I on EB activated carbon was determined to be 40 kj/mol. © 2008 Canadian Society for Chemical Engineering.