Catalyst and method for removing NOX from combustion exhaust gas
Provided is a catalyst for removing NOx from a combustion exhaust gas, in particular, a low-NOx combustion exhaust gas, wherein the catalyst has a ratio of a pore volume in a range of not less than 500 Å and not more than 3000 Å in a pore diameter relative to a total pore volume of not less than 15% and not more than 40% and preferably a ratio of a pore volume in a range of not less than 1000 Å in the pore diameter relative to the total pore volume of not less than 10% and not more than 45% in a pore volume distribution in a range of not more than 10 5 Å in the pore diameter, and where SILICA is unlikely to be deposited and even when the amount of SILICA deposited is increased, denitration performance is hardly lowered.
1. A catalyst for removing NOx from a combustion exhaust gas, wherein the catalyst comprises an oxide of titanium, an oxide of molybdenum and/or tungsten, and an oxide of vanadium, wherein a ratio of V element to Ti element is not more than 2% by weight in terms of a weight percentage of V 2 O 5 /TiO 2 ,
the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 500 A and not more than 3000 Å relative to a total pore volume of not less than 15% and not more than 40%, a ratio of a pore volume in a range of pore diameter of not less than 500 Å relative to the total pore volume of not less than 25% and not more than 50% and a ratio of a pore volume in a range of pore diameter of not less than 1000 Å relative to the total pore volume of not less than 10% and not more than 45% in a pore volume distribution in a range of pore diameter of not more than 10 5 Å.
2. The catalyst according to claim 1 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 40 Å and not more than 3000 Å relative to the total pore volume of not less than 80% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
3. The catalyst according to claim 2 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 40 Å relative to the total pore volume of not less than 90% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
4. The catalyst according to claim 2 , wherein a ratio of Mo element and/or W element to Ti element is not more than 5% by weight in terms of a weight percentage of (MoO 3 +WO 3 )/TiO 2 .
5. The catalyst according to claim 2 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 3000 Å relative to the total pore volume of not more than 10% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
6. The catalyst according to claim 1 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 40 Å relative to the total pore volume of not less than 90% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
7. The catalyst according to claim 6 , wherein a ratio of Mo element and/or W element to Ti element is not more than 5% by weight in terms of a weight percentage of (MoO 3 +WO 3 )/TiO 2 .
8. The catalyst according to claim 6 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 3000 Å relative to the total pore volume of not more than 10% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
9. The catalyst according to claim 1 , wherein a ratio of Mo element and/or W element to Ti element is not more than 5% by weight in terms of a weight percentage of (MoO 3 +WO 3 )/TiO 2 .
10. The catalyst according to claim 1 , wherein the catalyst has a ratio of a pore volume in a range of pore diameter of not less than 3000 Å relative to the total pore volume of not more than 10% in the pore volume distribution in the range of pore diameter of not more than 10 5 Å.
11. A method comprising bringing a combustion exhaust gas into contact with the catalyst according to claim 1 , in the presence of ammonia to remove NOx from the combustion exhaust gas.
12. The method according to claim 11 , wherein the combustion exhaust gas is a low concentration-NOx combustion exhaust gas.
13. The method according to claim 12 , wherein the combustion exhaust gas has a NOx concentration of not more than 350 ppm.