Denitration catalyst is the core part of the SCR process, the denitration catalyst applied in industrial mostly is vanadium/titanium based, with the temperature window of 370~430℃, and the denitration efficiency of about 80%. However, the vanadium/titanium (anatase) system is an unstable system, titanium dioxide is the metastable crystal with a smaller surface area; besides, when heated, the surface is easily shrank, and converted into stable thermodynamic state of rutile at a certain temperature and pressure, resulting in the declining of irreversible denitration efficiency. Experiments showed that the adding zirconium oxide can improve the tungsten trioxide denitration catalyst surface acidity, thermal stability and support denitrification efficiency.

 

It is well known that the first step of SCR denitration reaction is ammonia adsorption, the longer residence time benefits the reaction at the catalyst surface. The doped of tungsten oxide and zirconium oxide makes catalyst having superior storage capacity of ammonia, thus to conducive to the denitration reaction. Experimental prepared tungsten trioxide denitration catalyst doped zirconium, which showed as follows:

 

1. Prepare titanium oxide-zirconium oxide solid-solution vector (the molar ratio of Ti and Zr is 1) by coprecipitation method

Dropwise the titanium tetrachloride into deionized water containing zirconium oxychloride under the condition of ice-cooling with stirring;

2. After completing the addition, adjust the pH value to 9~10 with concentrated aqueous ammonia, stand for 12h after the white precipitate producing, then discard the upper-layer of serum;

3. Wash the precipitate with deionized water and go through vacuum filtration, until no Cl- exists;

4. Dry the washed the precipitate in an oven at 110℃ for 12 hours, grinding, and calcined in a muffle furnace at 450℃ for 4 hours to titanium-zirconium solid solution;

5. Preparation of WO₃/TiO₂-ZrO₂ catalyst, add ammonium tungstate into titanium-zirconium solid solution, then going through a oil bath at 25 ℃ for 4 hours and evaporating off all of the moisture at 85℃;

6. Dip the ammonium paratungstate under the condition of magnetic stirring with stirring, and then evaporated to get the dryness solid, transferred to an oven at 110℃ for 12 hours; calcined in a muffle furnace at 450 ℃ for 4 hours after milled to give the desired WO₃/TiO₂-ZrO₂ denitration catalyst.