Experimental and Theoretical Insights into the Effect of Syngas Components on Hg0 Removal over CoMn2O4 Sorbent

CoMn2O4 spinel sorbent was applied to remove Hg-0 in coal-derived syngas. The impacts of syngas components, including H2S, H-2, CO, HCl, and H2O, on Hg-0 abatement were examined. Moreover, the Hg-0 removal mechanism over the CoMn2O4 surface was elucidated in detail by combining experiments and density functional theory (DFT) calculations. About 90% Hg-0 abatement was obtained using CoMn2O4 sorbent in 40-200 degrees C under syngas atmosphere. H2S could adsorb and generate active sulfur upon CoMn2O4 and, hence, played the most important role in He elimination. HCl also facilitated He capture by producing reactive chlorine compounds. Under N-2 atmosphere, H-2, CO, and H2O played an inhibitory effect on Hg-0 removal, but they did not affect Hg-0 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 Hg-0 and H2S over CoMn2O4. After Hg-0 removal, HgS was formed and bonded to CoMn2O4 sorbent, which was certified using TPD and XPS analyses.