# US 7,744,839 B2 · Method for reducing the nitrogen oxide concentration in gases > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,744,839 B2 - Document ID: US7744839B2 - Status: Granted - Kind: B2 - Application number: 11/913,450 - Filed: 2006-04-27 - Published: 2008-10-02 - Granted: 2010-06-29 - Earliest claimed: 2005-05-11 - Assignees: Uhde GmbH - Inventors: Meinhard Schwefer; Rolf Siefert; Michael Groves - Web page: https://patentgrep.com/patent/US7744839B2 ## CPC - B01D 53/8628: {Processes characterised by a specific catalyst} - B01D 2251/202: Hydrogen - B01D 2251/204: Carbon monoxide - B01D 2251/2062: Ammonia - B01D 2251/208: Hydrocarbons - B01D 2255/20738: Iron - B01D 2255/50: Zeolites - B01D 2257/402: Dinitrogen oxide - B01D 2257/404: Nitrogen oxides other than dinitrogen oxide - Y02C 20/10: of nitrous oxide (N2O) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG] ## Abstract The method comprises passing an N2O- and NOx-containing gas over a sequence of two catalyst beds, adding reducing agents for NOx and for N2O between the catalyst beds in such an amount that not only NOx but also a predetermined proportion of N2O is reduced. The reaction conditions are set so that the N2O content of the gas is reduced by not more than 95%, based on the N2O content at the entrance of the first catalyst bed, by decomposition to nitrogen and oxygen in the first catalyst bed and that not only chemical reduction of NOx but also chemical reduction of N2O occurs in the second catalyst bed so that the N2O content of the gas is reduced by at least 50%, based on the N2O content at the entrance of the second catalyst bed. ## Claims ### Claim 1 A method for reducing the content of N2O and NOx in gases, comprising: a) passing the N2O- and NOx-containing gas over two catalyst beds, wherein the first catalyst bed contains a catalyst for decomposing N2O into nitrogen and oxygen and the second catalyst bed contains a catalyst for chemically reacting N2O and NOx with a reducing agent; b) selecting temperature, pressure, and space velocity in said first catalyst bed so that the decrease of N2O content of the gas is not more than 95%, based on the N2O content of the gas at the entrance of said first catalyst bed, and c) adding a reducing agent for N2O and a reducing agent for NOx between the first and second catalyst beds in an amount sufficient to chemically remove all of the NOx and at least 50% of the N2O, based on the N2O content of the gas at the entrance of said second catalyst bed. ### Claim 2 (depends on 1) The method of claim 1, wherein temperatures of less than 500° C. are set in the first and second catalyst beds. ### Claim 3 (depends on 1) The method of claim 1, wherein gas pressures of at least 2 bar are set in the first and second catalyst beds. ### Claim 4 (depends on 1) The method of claim 1, wherein the N2O- and NOx-containing gas is passed over said catalyst beds at a space velocity of from 5000 to 50 000 h−1, based on the summed catalyst volume of the two catalyst beds. ### Claim 5 (depends on 1) The method of claim 1, wherein at least one metal-laden zeolite catalyst is used in at least one of said catalyst beds. ### Claim 6 (depends on 5) The method of claim 5, wherein said at least one metal-laden zeolite catalyst is of the MFI, BEA, FER, MOR, FAU, and/or MEL type. ### Claim 7 (depends on 6) The method of claim 6, wherein said at least one metal-laden zeolite catalyst in the first catalyst bed is an iron-laden zeolite of the MFI and/or FER type. ### Claim 8 (depends on 6) The method of claim 6, wherein said at least one metal-laden zeolite catalyst in the second catalyst bed is an iron-laden zeolite of the MFI and/or BEA type. ### Claim 9 (depends on 6) The method of claim 6, wherein said at least one metal-laden zeolite catalyst in the first and second catalyst beds are an iron-laden zeolite of the MFI type. ### Claim 10 (depends on 1) The method of claim 1, wherein iron-laden zeolites which have been treated with steam are used in at least one catalyst bed. ### Claim 11 (depends on 1) The method of claim 1, wherein iron-laden zeolites in which the ratio of extra-lattice aluminium to lattice aluminium is at least 0.5 are used as catalysts in at least one catalyst bed. ### Claim 12 (depends on 11) The method of claim 11, wherein ammonia is used as reducing agent for NOx and hydrocarbons are used as reducing agent for N2O. ### Claim 13 (depends on 12) The method of claim 12, wherein the hydrocarbons are used as reducing agents for N2O in an amount of 0.2 to 1.0 mol per mol of N2O to be removed. ### Claim 14 (depends on 1) The method of claim 1, wherein nitrogen-containing reducing agents, hydrocarbons, carbon monoxide, hydrogen, or mixtures containing at least two of these components are used as reducing agents for NOx and as reducing agents for N2O. ### Claim 15 (depends on 1) The method of claim 1, wherein ammonia is used as reducing agent for NOx and as reducing agent for N2O. ### Claim 16 (depends on 15) The method of claim 15, wherein ammonia is used as reducing agent for NOx in an amount of from 0.9 to 2.5 mol per mol of NOx to be removed and ammonia is used as reducing agent for N2O in an amount of from 0.5 to 2.0 mol per mol of N2O to be removed. ### Claim 17 (depends on 1) The method of claim 1, wherein it is integrated into the process for nitric acid production. ### Claim 18 (depends on 1) The method of claim 1, wherein it is integrated into the process of operating a gas turbine. ### Claim 19 (depends on 1) The method of claim 1, wherein it is integrated into the process of operating a power station.