ROLE OF H2O AND O2 IN THE REACTIVE ADSORPTION OF H2S ON CuO-ZnO/AC AT LOW TEMPERATURE

H2S reactive adsorption on CuO-ZnO dispersed onto activated carbon is investigated in different gas streams, containing either O2, H2O or O2/H2O, at room temperature and in a lab-scale fixed-bed reactor. Sorbents performances are analyzed in terms of H2S adsorption capacity and adsorption rate and data are correlated with the sulphur species formed upon adsorption and in the different experimental conditions. Temperature Programmed Desorption (TPD), porosimetric and XPS analyses are performed in order to support the adsorption dynamic tests. The presence of O2 and H2O determines a remarkable increase in H2S adsorption capacity, favouring the formation of different sulphur species such as sulphides, sulphates and, above all, elemental sulphur. The analysis of the experimental data set shows the occurrence of two main H2S oxidation mechanisms with different rates: the first one quickly forms metal sulphates utilizing lattice oxygen from metal oxide clusters or superficial oxygen species; the second, slower one, requires H2O and molecular oxygen in the feed gas to catalytically form elemental sulphur chains that progressively fill-up the sorbent microporosity