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 O-2 at temperatures ranging from 26 degrees C to 400 degrees C. The results showed that the rate of Hg-0 oxidation over SCR catalyst was zeroth order with respect to O-2 and nearly first order with respect to Hg-0. Mercury oxidation followed the Eley-Rideal mechanism involving chlorine compounds as the intermediates that subsequently oxidize mercury. Formation of oxidized mercury (Hg2+) from Hg-0 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 Hg-0 oxidation in the presence of HCl and O-2 at different conditions. The apparent activation energy for Hg-0 oxidation over the SCR catalyst was 37.73 kj/mol according to the kinetic model. (C) 2013 Elsevier B.V. All rights reserved.