Activity of CuCl2-modified cobalt catalyst supported on Ti-Ce composite for simultaneous catalytic oxidation of Hg0 and NO in a simulated pre-sco process

Abstract

To achieve the high Hg0 oxidation efficiency in the atmospheres with low concentration of HCl or in temporary absence of HCl and facilitate the following SCR process, CuCl2-CoOX/Ti-Ce catalyst for simultaneous catalytic oxidation of Hg0 and NO in a pre-sco process (300–420°C) was developed. N2 adsorption-desorption, XRD, TG and XPS techniques were used to characterize the catalyst and its catalytic performance was evaluated in a laboratory-scale fixed-bed system. Results indicated that the oxidation process occurred at CuCl2 sites and CoOx sites separately for Hg0 and NO over the catalyst. With an increasing CuCl2 loading, more active CuCl2 species would form and both amorphous and crystalline phase of CuCl2 contribute to the excellent mercury oxidation capacity, however, resulting in the decrease of NO conversion efficiency. CuCl2 might hinder the interaction between NO species and CoOx sites. Thus, well dispersion of CuCl2 and CoOx species over catalyst surface could relieve the suppression. In the presence of 5ppmHCl and 6%O2, a sustainable Hg0 oxidation capability (nearly 100% at 360°C) could be achieved over 7%CuCl2-CTC catalyst. Elemental mercury at gaseous state collided with the CuCl2 sites of catalyst and reacted with the active Cl to form HgCl2. The consumption of active Cl species could be compensated by the gas phase HCl with the aid of O2. SO2 did not show a significant negative effect on Hg0 oxidation but suppressed NO oxidation. SO2 with high concentration would speed up the formation of sulphates, resulting in the loss of activity.