Method for preparing a catalyst for selective catalytic reduction of nitrogen oxides

A method for preparing a catalyst for selective catalytic reduction of nitrogen oxides, comprising the following steps of:

• a) pretreating a spent catalyst discharged from a hydro-desulfurization process of an oil refinery, comprising 1 to 30 wt % of vanadium, 1 to 20 wt % of nickel, 1 to 20 wt % of molybdenum and 1 to 15 wt % of sulfur component on alumina, by thermally treating said spent catalyst followed by washing with water
• b) providing a support impregnated with 1 to 15 wt % of tungsten on the support basis, said support being selected from the group consisting of alumina, titania, silica, zeolite and a mixture thereof;
• c) pulverizing the pretreated spent catalyst, followed by homogeneously wet-mixing the pulverized spent catalyst with the tungsten-impregnated support under the addition of water and acid;
• d) dehydrating the mixture to remove excess moisture and non-impregnated active metals therein;
• e) drying the dehydrated mixture, followed by grinding the dried mixture;
• and
• f) extruding the grinded mixture or coating the grinded mixture to a structure, followed by drying and then calcining to form a catalyst body.