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

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 Hg-0 and NO in the simulated flue gas. Results showed that the catalysts exhibited good capacity of simultaneous catalytic oxidation of Hg-0 (around 70%) and NO (around 40%) at 300 degrees C using a simulated flue gas (Hg-0, NO, SO2, O-2, H2O and balanced N-2). These catalysts were investigated in detail by means of N-2 adsorption-desorption, XRD, Raman spectroscopy, TEM and XPS. The characterization results indicated that physical characteristics of catalysts were not the main contributor for Hg-0 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 Hg-0 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 Hg-0 and NO oxidation. NO was observed to promote Hg-0 oxidation with the presence of O-2. SO2 led to a certain decrease of Hg-0 oxidation efficiency due to the competitive adsorption.H2O had a slightly inhibitory impact on Hg-0 oxidation. Moreover, NO oxidation was more susceptible to SO2 than Hg-0 oxidation over the catalyst. (C) 2017 Elsevier Ltd. All rights reserved.