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1. (WO2018077554) A METHOD FOR REMOVING NITROGEN OXIDES FROM A GAS USING AN IRON EXCHANGED ZEOLITE CATALYST
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CLAIMS

1 . A method for removing nitrogen oxides NOx from a gaseous current, comprising the steps of:

passing the gaseous current through a de-NOx catalytic bed comprising a catalyst which is iron exchanged zeolite, with the addition of ammonia as a reducing agent,

wherein the molar ratio of NH3 over NOx in the gas admitted to said de- NOx catalytic bed is greater than 1 .33.

2. A method according to claim 1 , said ratio of NH3 over NOx being greater than 1 .4.

3. A method according to claim 2, said ratio of NH3 over NOx being 1 .4 to 2, preferably 1 .4 to 1 .6, more preferably 1 .5 or about 1 .5.

4. A method according to any of the previous claims, wherein, after the passage though said de-NOx catalytic bed, the residual amount of NOx in the gas is not greater than 100 ppm, preferably not greater than 50 ppm, more preferably not greater than 25 ppm.

5. A method according to any of the previous claims comprising the step of: operating said de-NOx catalytic bed at a temperature in the range of 400 to 450 °C, preferably 430 °C.

6. A method according to any of the previous claims, wherein the iron exchanged zeolite catalyst is chosen among the following types: MFI, BEA, FER, MOR, FAU, MEL, or a combination thereof.

7. A method according to claim 6, wherein the iron exchanged zeolite is of the Fe-ZSM-5 type.

8. A method according to any of the previous claims, wherein the space velocity in said de-NOx catalytic bed is 10000 h"1 to 14000 h"1, preferably 13000 h-1 .

9. A method according to any of the previous claims, the absolute pressure of the gas in said de-NOx catalytic bed being greater than 1 bar, preferably 2 to 25 bar, more preferably 5 to 15 bar.

10. A method according to any of the previous claims wherein the gaseous current is a tail gas of a process for making nitric acid, withdrawn from an absorption column.

1 1 . A method according to any of the previous claims comprising: passing the NOx-containing gas through a first de-NOx catalytic bed, adding ammonia as a reducing agent to the effluent of said first-de-NOx catalytic bed until the molar ratio of NH3 over NOx in said effluent gas is greater than 1 .33, preferably 1 .4 to 1 .6, passing the effluent gas and ammonia directly through said de-NOx catalytic bed without a passage through a de-N2O catalytic bed.

12. A method according to any of the previous claims, wherein the gaseous current is a flue gas of a combustion process, or a tail gas of a process for making nitric acid withdrawn from an absorption column, and

the process does not comprise passing the gas through a series of another de-NOx catalytic bed and a subsequent de-N2O catalytic bed, before the passage through said de-NOx catalytic bed.