Method for treating contaminated catalyst

A method for restoring the catalytic activity of a selective catalytic reduction catalyst, supported on a catalyst support and contaminated with platinum, to enhance catalytic reduction of oxides of nitrogen to nitrogen by said catalyst, said method comprising:

• a. contacting said spent catalyst with a solution comprising a metal salt of a metal which catalyzes the reaction of ammonia and an oxide of nitrogen to nitrogen;
• b. heating said catalyst contacted with said solution at a calcination temperature in the presence of oxygen to a calcination temperature at which said metal salt is decomposed to form an oxide of said metal, and said metal oxide is bonded to said catalyst support to form a calcined catalyst;
• and,
• c. contacting said calcined catalyst with a SCR flue gas stream at a temperature in the range of about 450.degree. F. to about 750.degree. F.

A method of treating catalyst having a surface area and contaminated with platinum, said method comprising:

• a. heating water to a temperature in the range of about 110.degree. F. to about 130.degree. F. to form mildly warm water;
• b. adding oxalic acid to said warm water;
• c. adding ammonium meta-vanadate to said warm water to form a solution of ammonium meta-vanadate in oxalic acid and water and maintaining said solution at a temperature wherein said ammonium meta-vanadate is dissolved;
• d. contacting said catalyst contaminated with platinum with said solution of ammonium meta-vanadate in oxalic acid and water for a period of time sufficient to permit said solution to contact at least a substantial portion of said surface area of said catalyst;
• e. drying said catalyst of step d. with air for at least ten seconds;
• f. heating said catalyst of step e. to a temperature in the range of about 130.degree. F. to about 170.degree. F. for a period about 30 minutes to about 90 minutes to liberate ammonia from said meta-vanadate, CO from said oxalic acid and SO.sup.2 from vanadyl sulfate;
• and
• g. heating said catalyst of step f. to a calcination temperature in the range of about 225.degree. F. to 300.degree. F.