Insights into H2S-absorption and oxidation-regeneration behavior of Ni-doped ZnO-based sorbents supported on SBA-15 for desulfurization of hot coal gas

Sulfur removal from hot coal gas is one of important technologies for highly efficient coal-based energy system. H2S-absorption and oxidation-regeneration behavior of Ni-doped ZnO-based sorbents supported on SBA-15 (ZnNi/SBA-15) was analyzed in this work. The results indicate that ZnNi/SBA-15 shows highest H2S-uptake capacity (16 g S/100 g sorbent) and lowest amount of produced COS (0.0004 g COS/100 g sorbent) when used for desulfurization at 500 degrees C. Removal of H2S at 700 degrees C leads to lowest breakthrough sulfur capacity of sorbents. It is ascribed to the destruction of typical microscopic morphology of SBA-15. Boltzmann function is suitable for modeling the H2S-absorption behavior of ZnNi/SBA-15. The evolution rate of H2S for sorbents varies from 0.096 to 0.228 min(-1) at 400-700 degrees C. H2S-CO and H2S-CO2 reactions both contribute to the formation of COS at the stage of H2S-absorption saraturation. Increase of temperature from 550 to 600 degrees C results in the disappearance of ZnS in regenerated ZnNi/SBA-15. Moreover, most of plugged pore structure caused by sulfidation reaction could restore after regeneration at 600 degrees C. Further increase of regeneration temperature causes the decline of regeneration efficiency and less porous sorbent. Additionally, the sorbents have stable desulfurization ability and low COS emission during multiple sulfidation-regeneration cycles.