Increased co-oxidation activity for mercury under hot and cold site coal power plant conditions – Preparation and evaluation of Au/TiO2-coated SCR-DeNOx catalysts

• Preparation of structured Au/TiO2-coated SCR-DeNOx catalysts.
• Their mercury oxidation, DeNOx and SO2/SO3 conversion activity were investigated.
• Au/TiO2 coatings are promising for increasing the mercury co-oxidation activity.
• Au/TiO2 coatings did not appreciably affect the main DeNOx reaction.
• Au/TiO2 coatings increased the SO2/SO3 conversion rate at higher temperatures.

The investigation aims to develop SCR-catalysts with enhanced oxidation activity for elemental mercury. For this, different nano-sized TiO2 particles were coated with 1 and 2 wt.% gold. Suspensions obtained from these particles were used for dip-coating the commercial honeycomb-shaped V2O5–WO3/TiO2 reference SCR catalyst. The mercury oxidation activities of the Au/TiO2-coated catalysts were investigated in the laboratory for the temperature range 180–390 °C and simulated coal-fuel flue gas conditions (O2, SO2, NO, H2O, Hg, HCl and without NH3).At reaction temperatures from 180 to 320 °C, Au/TiO2 coatings enhanced the mercury oxidation activity of the SCR catalyst significantly by a factor of 2. At higher reaction temperatures the positive effect of the Au/TiO2 coatings on mercury oxidation decreased and was strongly dependent on the HCl content of the flue gas. The impact of Au/TiO2 coatings on the DeNOx activity of the SCR catalysts at 390 °C was only marginal. The measured SO2/SO3 conversion activity rates depended on the coating procedure and the gold content of the catalysts.In conclusion, the Au/TiO2 coatings are promising for the development of multi-pollutant SCR-DeNOx catalysts with high mercury co-oxidation activity for cold-site configurations or flue gases with higher HCl contents.

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