Experimental and Theoretical Insights into the Effect of Syngas Components on Hg⁰ Removal over CoMn₂O₄ Sorbent
2020
Wang, Zhen | Yang, Yingju | Liu, Jing | Liu, Feng | Yan, Xuchen
CoMn₂O₄ spinel sorbent was applied to remove Hg⁰ in coal-derived syngas. The impacts of syngas components, including H₂S, H₂, CO, HCl, and H₂O, on Hg⁰ abatement were examined. Moreover, the Hg⁰ removal mechanism over the CoMn₂O₄ surface was elucidated in detail by combining experiments and density functional theory (DFT) calculations. About 90% Hg⁰ abatement was obtained using CoMn₂O₄ sorbent in 40–200 °C under syngas atmosphere. H₂S could adsorb and generate active sulfur upon CoMn₂O₄ and, hence, played the most important role in Hg⁰ elimination. HCl also facilitated Hg⁰ capture by producing reactive chlorine compounds. Under N₂ atmosphere, H₂, CO, and H₂O played an inhibitory effect on Hg⁰ removal, but they did not affect Hg⁰ removal in the presence of H₂S. Based on the experimental and DFT results, the Langmuir–Hinshlwood mechanism, where chemically adsorbed mercury interacts with surface sulfur from H₂S dissociation, is responsible for the reaction between Hg⁰ and H₂S over CoMn₂O₄. After Hg⁰ removal, HgS was formed and bonded to CoMn₂O₄ sorbent, which was certified using TPD and XPS analyses.
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