Study On Catalytic Oxidation Of Elemental Mercury Over Cerium Phosphate Based Catalysts

With the burning of coal and other fossil fuels, large amounts of anthropogenic mercury are emitted into the atmosphere. Catalytic oxidation combined with absorption of WFGD is an effective method for controlling mercury pollution from flue gases, which has attracted tremendous attentions in current science. The key of this technology is to develop efficient catalysts for Hg0 oxidation.Based on this technology, the thesis had developed a novel Ce-P-O catalyst, which showed a remarkable Hg0 oxidation efficiency. At high temperature region (300～ 400 ℃), its Hg0 oxidation efficiency could reach more than 95%. In simulated flue gas conditions (containing flue gases with H2O, SO2, HCl and NO at a space velocity of 600000 h-1), the oxidation efficiency could be still retained at more than 70% at the temperature of 350 ℃. While under the same conditions, Hg0 oxidation efficiency of SCR catalyst (V-W-Ti) was merely about 5%. This result indicated that the Ce-P-O catalyst had promising application in Hg0 catalytic oxidation. To take full use of SCR reactor and achieved the goal of denitration coupled with Hg0 oxidation, the thesis studied the SO2 poisoning resistance of Ce-P-O catalyst in SCR process. It was found that the removal efficiency of NOX decreased to 66% after 9 h measurement in the presence of 500 ppm SO2 at the temperature of 350℃.To improve its SO2 poisoning resistance, the Ce-P-O catalyst was then modified by doping V, which was found effective. In the presence of 500 ppm SO2, the removal efficiency of NOx over the modified catalyst retained nearly 100% at the temperature of 350℃ for 13 h. The doping of V over the Ce-P-O catalyst can also promote its Hg0 oxidation efficiency and the optimal doping level was between 1.0～2.0 wt%, the oxidation efficiency of which could reach 85% with a space velocity of 1200000 h-1 at the temperature of 350 ℃.Finally, several application conditions were evaluated over the V/Ce-P-O catalyst to explore its feasibility in these applications. Experimental results indicated that the catalyst exhibited satisfied performance in the application of SCR reaction coupled with Hg0 oxidation. Therefore, the catalyst could be applied into denitration and Hg0 oxidation simultaneously, and could be also utilized as a supplement for commercial SCR catalystto oxidize Hg0, which was of great potential for industrial applications.