Complete catalytic reaction of mercury oxidation on CeO2/TiO2 (001) surface: A DFT study

CeO2/TiO2 catalyst is a promising material for realizing the integration of denitrification and mercury removal to reduce mercury emissions. Oxidation mechanism of Hg-0 on CeO2/TiO2 (001) surface in the presence of HCl and O-2 was studied by density functional theory (DFT). The results indicated that Hg-0 was physically adsorbed on CeO2/TiO2 (001) surface. As an important intermediate, HgCl was adsorbed on the surface of CeO2/TiO2 (001) utilizing enhanced chemisorption, while the adsorption energy of HgC1 2 was only -57.05 kJ/mol. In the absence of HC1, mercury oxidation followed the Mars-Maessen mechanism with a relatively high energy barrier, and the product (HgO) was difficult to desorb, which hindered the reaction process. When HCl existed, reactive chlorine (Cl*) would be produced by the dissociation of HCl, and the mercury oxidation would follow the Langmuir-Hinshelwood mechanism. The co-existence of HCl and O-2 had no significant effect on the adsorption of Hg-0, but reduced the reaction energy barrier and the final product (HgCl2) was more easily desorbed from the catalyst surface. In addition, two complete cyclic reaction pathways for catalytic oxidation of Hg-0 on CeO2/TiO2 (001) surface were constructed to clarify the detailed reaction process.

Automated summary

CeO2/TiO2 catalyst is effective in denitrification and mercury removal, reducing mercury emissions. The presence of HCl and O2 influences the oxidation of Hg-0 on the catalyst surface, and HgCl acts as an important intermediate in the catalytic process.