Insights into the effects of metal-ion doping on the structure and hot-coal-gas desulfurization properties of Zn-based sorbents supported on SBA-15

Abstract

Doping of metal (Co/Ni/Ce) ions into ZnO was proposed for modifying the structure and hot-coal-gas desulfurization properties of ZnO supported on SBA-15 (ZnO/SBA-15). Co and Ce element are presented as Co2+ and Co3+, and Ce3+ and Ce4+ in modified sorbents, respectively, while only Ni2+ is found in Ni-ion-doped sorbents. Doping of Co/Ni ions causes the formation of Zn-Co/Ni-O solid solution and more porous sorbents. Accordingly, the desulfurization performance of ZnO/SBA-15 is greatly improved after the doping of Co/Ni ions. Furthermore, Ni-doped sorbent with Zn/Ni molar ratio of 20:1 (Zn20Ni1/SBA-15) shows the highest breakthrough sulfur capacity (16.0 g of S per 100 g of sorbent). More importantly, the introduction of Co/Ni/Ce ions produces an inhibiting effect on the formation of COS during desulfurization process. Especially, the amount of COS formed before H2S breakthrough for Zn20Ni1/SBA-15 decreases by 99.4% compared to ZnO/SBA-15. The inhibition of COS emission is mainly attributed to the catalytic effect of Co/Ni/Ce-containing species on the hydrogenolysis of COS. In addition, Zn20Ni1/SBA-15 shows stable desulfurization performance during successive sulfidation/regeneration cycles, favorable for its application for hot coal gas desulfurization.