Catalytic oxidation of Hg0 in flue gas over Ce modified TiO2 supported Co-Mn catalysts: Characterization, the effect of gas composition and co-benefit of NO conversion

- CoxMn5/TiCey catalysts exhibited good capacity of catalytic oxidation of Hg0 and NO.
- Ce species existed mainly in amorphous phase.
- Co promoted the generation of Mn2O3 but obstructed the dispersion of MnOx.
- Multiple redox couples and surface oxygen species contributed to Hg0 and NO oxidation.
- O2 promoted the oxidation activity but SO2 generally suppressed it.

A series of Ce modified TiO2 supported Co-Mn catalysts (CoxMn5/TiCey) prepared by sol-gel method and impregnation method were evaluated for simultaneous catalytic oxidation of Hg0 and NO in the simulated flue gas. Results showed that the catalysts exhibited good capacity of simultaneous catalytic oxidation of Hg0 (around 70%) and NO (around 40%) at 300 °C using a simulated flue gas (Hg0, NO, SO2, O2, H2O and balanced N2). These catalysts were investigated in detail by means of N2 adsorption-desorption, XRD, Raman spectroscopy, TEM and XPS. The characterization results indicated that physical characteristics of catalysts were not the main contributor for Hg0 and NO oxidation. Ce species existed mainly in amorphous phase. The addition of CeOx might lead to a migration of Co and Mn species from bulk to surface. The addition of Co could promote the generation of Mn2O3 but obstruct the dispersion of MnOx on the surface of catalyst. An appropriate increasing loading amount of CoOx or CeOx would be preferable for the improvement of activity performance. The presence of Co3+/Co2+, Mn4+/Mn3+ and Ce4+/Ce3+ redox couples as well as surface oxygen species contributed to the Hg0 and NO oxidation. A possible synergetic effect Among Co, Mn and Ce species might improve the activity further. Furthermore, an increased oxygen concentration could facilitate the Hg0 and NO oxidation. NO was observed to promote Hg0 oxidation with the presence of O2. SO2 led to a certain decrease of Hg0 oxidation efficiency due to the competitive adsorption·H2O had a slightly inhibitory impact on Hg0 oxidation. Moreover, NO oxidation was more susceptible to SO2 than Hg0 oxidation over the catalyst.