Method for preparing a catalyst for reduction of nitrogen oxides

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

• a) pretreating a spent catalyst discharged from a hydro-desulfurization process of an oil refinery, which comprises 4 wt % or less of vanadium, 4 wt % or less of nickel, 5 wt % or more of molybdenum and 1 wt % or less of sulfur on an alumina support by thermally treating said spent catalyst followed by washing with water;
• b) providing a titania impregnated with 3 to 10 wt % of tungsten on the basis of titania weight;
• c) pulverizing the pretreated spent catalyst, followed by homogeneously mixing the pulverized spent catalyst with the tungsten-impregnated titania under the addition of water and acid;
• d) dehydrating the mixture to remove excess moisture and active metal components therein;
• e) drying the dehydrated mixture at 100 to 200° C. for 9 hours or longer, followed by grinding the dried mixture;
• and
• f) forming a catalyst body by extruding the grinded mixture or coating the grinded mixture to a structure, followed by drying under a constant temperature and humidity condition and then calcining the dried structure.