Mixed-oxide sorbents for high-temperature removal of hydrogen sulfide

Abstract

Several pure and mixed oxides (ZnO, CuO, ZnO-Fe_2O_3, CuO-Fe_2O_3, CuO-AI_O_3, and CuO-Fe_2O_3-Al_2O_3) were investigated as regenerable sorbents for the removal of H_2S at high temperatures. A special technique was used to prepare the sorbents in highly porous form. The sorbents were subjected to successive sulfidation-regeneration cycles in a packed-bed microreactor. Sulfidation was carried out at 538-650 °C with H_2S-H_2O-H_2-N_2 mixtures, regeneration with O_2-N_2-H_2O mixtures. Fresh, sulfided, and regenerated sorbents were characterized by XRD, SEM-EDS, and BET surface area analysis. Solid conversion and the prebreakthrough exit concentration of H_2S are discussed in terms of physical structure and thermodynamic properties of the sorbents. The performance of the sorbents CuO-Fe_2O_3, CuO-Al_2O_3, and CuO-Fe_2O_3-AI_2O_3 is discussed in terms of changes in the oxidation state of copper during sulfidation.