ZnO-CuO supported on activated carbon for H2S removal at room temperature

Sorbents for low temperature reactive adsorption of H2S were prepared by dispersing mixed Zn and Cu oxides onto a commercial activated carbon at fixed total metal loading and Cu:Zn atomic ratios from 0:1 to 1:1. Fresh and spent sorbents were characterized by means of ICP-MS, SEM-EDX, XRD, BET and pore size distribution, DRIFT and sulphur elemental analysis. H2S (50–3000 ppmv in N2) removal tests were run under dynamic conditions at 30 C. Due to the high dispersion of the metal oxide phase and its favorable interaction with the carbonaceous support, the functionalized sorbents showed a strongly enhanced adsorption capacity with respect to the raw activated carbon, under dry conditions. Furthermore, the utilization factor of the active phase (moles of S captured per mole of Cu + Zn) increased along with the Cu content up to 76%, thus demonstrating a clear promoting effect of Cu-insertion on the reactivity of ZnO, already at low Cu concentration. Temperature Programmed Desorption (TPD) of H2S and SO2 from saturated sorbents showed that H2S adsorption was coupled with oxidation phenomena leading to the formation of metal sulphates apart from metal sulphides and/or elemental sulphur, testifying the complexity of the surface reactions.