Method of cleaning exhaust gases

Claim 1

A method of removing nitrogen oxides and carbon monoxide simultaneously from an exhaust gas containing 10 to 1,000 ppm of nitrogen oxides, 10 to 10,000 ppm of carbon monoxide, 0 to 1,000 ppm of sulfur oxides, 1 to 20% by volume of oxygen, 1 to 15% by volume of carbon dioxide gas, 5 to 20% by volume of steam and 0 to 20 g/Nm 3 of soot which comprises passing the exhaust gas together with ammonia over a first stage NOx removing catalyst consisting of (a) 50 to 99.5% by weight of a catalytic oxide composed of a titanium-containing oxide and (b) 0.5 to 50% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of vanadium, tungsten, molybdenum and tin at a temperature of 200° to 500° C., and then passing the exhaust gas over a second stage catalyst consisting of (A) 60 to 99.9% by weight of a catalytic oxide composed of a titanium containing oxide, (B) 0.1 to 20% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of copper, manganese and chromium and (C) 0 to 20% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of vanadium, tungsten, molybdenum, cerium and tin at a temperature of 200° to 500° C., thereby removing nitrogen oxides and carbon monoxide simultaneously from the exhaust gas.

Claim 2

A method of removing nitrogen oxides and carbon monoxide simultaneously from an exhaust gas containing 10 to 1,000 ppm of nitrogen oxides, 10 to 10,000 ppm of carbon monoxide, 0 to 1,000 ppm of sulfur oxides, 1 to 20% by volume of oxygen, 1 to 15% by volume of carbon dioxide gas, 5 to 20% by volume of steam and 0 to 20 g/Nm 3 of soot which comprises passing the exhaust gas together with ammonia over a first stage NOx removing catalyst consisting of (a) 50 to 99.5% by weight of a catalytic oxide composed of a titanium-containing oxide and (b) 0.5 to 50% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of vanadium, tungsten, molybdenum and tin at a temperature of 200° to 500° C., and then passing the exhaust gas over a second stage catalyst consisting of (A) 60 to 99.9% by weight of a catalytic oxide composed of a titanium containing oxide, (B) 0.1 to 20% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of copper, manganese and chromium and (C) 0 to 20% by weight of a catalytic oxide composed of at least one metal oxide selected from the group consisting of oxides of vanadium, tungsten, molybdenum, cerium and tin at a temperature of 200° to 500° C., thereby removing nitrogen oxides and carbon monoxide simultaneously from the exhaust gas.