Kinetics of mercury oxidation in the presence of hydrochloric acid and oxygen over a commercial SCR catalyst

Experiments were conducted in a fixed-bed reactor containing a commercial SCR catalyst sample to investigate the kinetics of mercury oxidation in the presence of HCl and O2 at temperatures ranging from 26 °C to 400 °C. The results showed that the rate of Hg0 oxidation over SCR catalyst was zeroth order with respect to O2 and nearly first order with respect to Hg0. Mercury oxidation followed the Eley–Rideal mechanism involving chlorine compounds as the intermediates that subsequently oxidize mercury. Formation of oxidized mercury (Hg2+) from Hg0 was likely the rate limiting step. The method for predicting mercury oxidation efficiency in a kinetic framework was also proposed, which used the reaction rate of mercury oxidation per catalyst mass to calculate oxidation efficiency. In agreement with the experimental results, the kinetic model well described the rate of Hg0 oxidation in the presence of HCl and O2 at different conditions. The apparent activation energy for Hg0 oxidation over the SCR catalyst was 37.73 kJ/mol according to the kinetic model.

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► Hg0 oxidation over the commercial catalyst follows the Eley–Rideal mechanism.
► The presence of both HCl and O2 is critical to Hg0 oxidation.
► Hg0 oxidation is zeroth-order with respect to O2 and first-order in regard to Hg0.
► The activation energy for Hg0 oxidation over the SCR catalyst is 37.7 kJ/mol.