1 research outputs found
Heterogeneous Mercury Oxidation by HCl over CeO<sub>2</sub> Catalyst: Density Functional Theory Study
CeO<sub>2</sub>-based catalysts have been regarded as potential
materials for Hg removal due to high catalytic performance, nontoxicity,
and low cost. Density functional theory calculations were performed
to investigate the mercury oxidation mechanism by HCl over a CeO<sub>2</sub> catalyst. The thermodynamic stability analysis suggests that
the stoichiometric CeO<sub>2</sub>(111) is the most stable surface.
The protonated CeO<sub>2</sub> surfaces takes place at low oxygen
partial pressures, and the chlorinated CeO<sub>2</sub> surfaces can
stably exist under low HCl concentrations. The adsorption energies
and geometries show that Hg<sup>0</sup> is physically adsorbed on
oxygen sites of the CeO<sub>2</sub>(111) surface and HCl is chemically
adsorbed on the CeO<sub>2</sub>(111) surface. HCl can dissociate on
the CeO<sub>2</sub>(111) surface with a low barrier. The Hg oxidation
is most likely to proceed with the Eley–Rideal mechanism at
the first step (Hg → HgCl), followed by the Langmuir–Hinshelwood
mechanism at the second step (HgCl → HgCl<sub>2</sub>). In
the whole Hg oxidation reaction, the formation of HgCl<sub>2</sub> is the rate-determining step. The low energy barriers for the oxidation
reaction of Hg on CeO<sub>2</sub> make it an attractive alternative
catalyst for Hg oxidation