WO2013069713A1 - Catalyst for removing nitrogen oxide contained in combustion exhaust gas, and method for removing nitrogen oxide using said catalyst - Google Patents

Catalyst for removing nitrogen oxide contained in combustion exhaust gas, and method for removing nitrogen oxide using said catalyst Download PDF

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WO2013069713A1
WO2013069713A1 PCT/JP2012/078911 JP2012078911W WO2013069713A1 WO 2013069713 A1 WO2013069713 A1 WO 2013069713A1 JP 2012078911 W JP2012078911 W JP 2012078911W WO 2013069713 A1 WO2013069713 A1 WO 2013069713A1
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catalyst
exhaust gas
nitrogen oxide
removing nitrogen
temperature
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Japanese (ja)
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日数谷　進
香奈 清水
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日立造船株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
    • B01J29/46—Iron group metals or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/2073—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20746—Cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to a catalyst for removing nitrogen oxides (hereinafter referred to as NOx) in combustion exhaust gas and a method for removing NOx using the catalyst.
  • NOx nitrogen oxides
  • a method for removing NOx contained in combustion exhaust gas is an ammonia selective catalytic reduction in which ammonia is added to exhaust gas as a reducing agent and NOx is removed by contacting the exhaust gas with a denitration catalyst mainly composed of vanadium or titania.
  • the method (hereinafter referred to as the ammonia SCR method) is the mainstream.
  • Sulfur oxides (hereinafter referred to as SOx) are present together with NOx in the combustion exhaust gas of fuel containing sulfur such as heavy oil.
  • the denitration temperature of such combustion exhaust gas must be equal to or higher than the precipitation temperature of ammonium sulfate from the viewpoint of preventing the precipitation of ammonium sulfate on the catalyst.
  • the precipitation temperature of ammonium sulfate is related to the SO 3 and ammonia concentrations in the exhaust gas. The relationship is shown in FIG. As can be seen from FIG. 1, as the SO 3 and ammonia concentrations increase, the precipitation temperature of ammonium sulfate increases.
  • the flue gas of a coal-fired boiler generally SOx concentration S0 3 concentration thereof of 10% 10ppm for a 100 ppm, ammonia concentration for a NOx concentration is 500ppm is maximum 500ppm.
  • the precipitation temperature of ammonium sulfate under this condition is about 250 ° C.
  • the exhaust gas temperature at this time is usually 300 to 400 ° C., and since the ammonium sulfate precipitation temperature is higher than 250 ° C., ammonium sulfate does not precipitate on the catalyst, and stable catalyst performance can be maintained.
  • the SOx concentration in the exhaust gas is 1000 ppm
  • the NOx concentration is as high as 1000 ppm
  • the precipitation temperature of ammonium sulfate is as high as about 280 ° C.
  • the exhaust gas temperature is as low as 250 ° C., ammonium sulfate precipitates under these conditions, and stable catalyst performance cannot be maintained.
  • a direct decomposition method such as Patent Document 1 in which NOx is simply brought into contact with a catalyst made of a metal composite oxide having ionic conductivity and decomposed into nitrogen and oxygen, or as a reducing agent.
  • a denitration method in which NOx is brought into contact with a catalyst using hydrocarbons.
  • a catalyst in which a metal is supported on ⁇ zeolite Patent Document 2
  • a catalyst mainly composed of alumina, aluminum sulfate, and silver Patent Document 3
  • the reaction temperature is as high as 600 ° C. or more in the former method, and about 350 ° C. in the latter method.
  • Patent Document 4 describes a direct cracking method that does not use a reducing agent.
  • Comparative Example 3 a catalyst in which a metal is supported on hydrogenated zeolite is used, and the NOx removal rate is 10% or less at a temperature of 400 ° C. It has been shown.
  • this catalyst a part of the proton acid point, which is an acid point stronger than the metal acid point, remains even after the metal is supported, so that NO preferentially attacks the stronger acid point and the denitration reaction does not proceed easily.
  • the cause is that in the direct decomposition method and the reduction removal method, oxygen generated when NO is decomposed on the catalyst is not removed from the catalyst surface. Therefore, if it is possible to remove oxygen on the catalyst surface, it is considered that a direct decomposition method and a reduction removal method are possible.
  • exhaust gas is heated at a temperature of 200 to 350 ° C., preferably 220 to 320 ° C., more preferably a catalyst obtained by ion-exchange of MFI type zeolite with at least one of Fe, Co, and Mn. It has been found that NOx can be effectively reduced by contacting in the range of 230 to 300 ° C., more preferably 230 to 270 ° C.
  • MFI-type zeolite may be a commercially available product.
  • the ion exchange method may be, for example, a method in which MFI-type zeolite is suspended in an aqueous solution containing Fe, Co and / or Mn precursor compounds, and the zeolite is dried and then calcined after filtration and washing.
  • the precursor compound may be an inorganic acid salt (eg, nitrate, sulfate) or an organic acid salt (eg, acetate) of Fe, Co and / or Mn.
  • the zeolite after ion exchange with at least one of Fe, Co, and Mn has an acid point in the sodium, the above ion exchange metal, and the proton, and the acid strength at each acid point is proton> ion exchange metal> Sodium order.
  • the denitration reaction proceeds by decomposing nitric oxide at the acid sites of the ion exchange metal.
  • Example 1 After Fe / zeolite catalyst commercially available MFI zeolite 4g of 0.05M of Fe (NO 3) 3 ⁇ 9H 2 0 aqueous 500m1, and the suspension 6 hours at 50 ° C., filtered, washed, 12 at 120 ° C. It was dried for 4 hours and then calcined at 400 ° C. for 6 hours. Thus, an Fe ion exchange zeolite catalyst was obtained. The Fe loading of this catalyst was 2.0 wt%.
  • Example 2 Co / zeolite catalyst 4 g of commercially available MFI type zeolite was suspended in 500 ml of 0.01 M Co (NO 3 ) 2 aqueous solution at 80 ° C.
  • Example 3 Mn / zeolite catalyst 4 g of commercially available MFI-type zeolite was suspended in 500 ml of 0.01M Mn (CH 3 COO) 2 aqueous solution at 80 ° C. for 18 hours, then filtered, washed and dried at 120 ° C. for 12 hours. Further, it was calcined at 500 ° C. for 4 hours. In this way, a Mn ion exchange zeolite catalyst was obtained.
  • Comparative Example 1 A1 2 0 3 4g of 0.05M of Fe (NO 3) 3 ⁇ 9H 2 0 was suspended 6 hours at 80 ° C. in an aqueous solution 500 ml, which was filtered, dried at 120 ° C. 12 hours, further 400 ° C. For 6 hours. Thus, an Fe-supported A1 2 0 3 catalyst was obtained. The Fe loading of this catalyst was 2.0 wt%. Comparative Example 2 After suspending 4 g of commercially available ⁇ -type zeolite in 500 ml of 0.01 M Co (NO 3 ) 2 aqueous solution at 80 ° C. for 18 hours, this was filtered, washed, dried at 120 ° C.
  • Table 2 shows the test results.
  • the reason why NO 2 is generated at the outlet is due to the equilibrium relationship. NO is oxidized to NO 2 by oxygen in the air in the supply gas. The denitration rate can be improved by increasing the amount of catalyst.
  • the denitration rate higher than that of the comparative example was obtained in any of the catalysts, indicating that the catalyst of the present invention has a high catalytic performance at a reaction temperature of 250 ° C.

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Abstract

The present invention provides a method by which a nitrogen oxide contained in an exhaust gas can be removed with high efficiency at a temperature around an ammonium sulfate precipitation temperature. A method for removing a nitrogen oxide contained in an exhaust gas, characterized by comprising bringing the exhaust gas into contact with a catalyst at a temperature ranging from 200 to 350˚C, wherein the catalyst is produced by the ion exchange of an MFI-type zeolite with at least one element selected from Fe, Co and Mn.

Description

燃焼排ガス中の窒素酸化物の除去触媒および同触媒を用いる窒素酸化物の除去方法Catalyst for removing nitrogen oxides from combustion exhaust gas and method for removing nitrogen oxides using the catalyst
　本発明は、燃焼排ガス中の窒素酸化物（以下、ＮＯｘと記す）の除去触媒および同触媒を用いるNOｘの除去方法に関する。 The present invention relates to a catalyst for removing nitrogen oxides (hereinafter referred to as NOx) in combustion exhaust gas and a method for removing NOx using the catalyst.
　燃焼排ガス中に含まれているNOｘを除去する方法は、アンモニアを還元剤として排ガスに添加しバナジウムやチタニアを主成分とする脱硝触媒に排ガスを接触させることでＮＯｘを除去するアンモニア選択的接触還元法（以下、アンモニアＳＣＲ法と記す）が主流である。 A method for removing NOx contained in combustion exhaust gas is an ammonia selective catalytic reduction in which ammonia is added to exhaust gas as a reducing agent and NOx is removed by contacting the exhaust gas with a denitration catalyst mainly composed of vanadium or titania. The method (hereinafter referred to as the ammonia SCR method) is the mainstream.
　重油等の硫黄を含む燃料の燃焼排ガス中にはＮＯｘと共に硫黄酸化物（以下、ＳＯｘと記す）が存在する。このような燃焼排ガスの脱硝温度は、触媒上への硫安の析出を防止する観点から硫安の析出温度以上でなければならない。硫安の析出温度は排ガス中のＳＯ３およびアンモニア濃度に関係する。その関係を図１に示す。図１からわかるようにＳＯ３およびアンモニア濃度が高くなると硫安の析出温度が高くなる。 Sulfur oxides (hereinafter referred to as SOx) are present together with NOx in the combustion exhaust gas of fuel containing sulfur such as heavy oil. The denitration temperature of such combustion exhaust gas must be equal to or higher than the precipitation temperature of ammonium sulfate from the viewpoint of preventing the precipitation of ammonium sulfate on the catalyst. The precipitation temperature of ammonium sulfate is related to the SO 3 and ammonia concentrations in the exhaust gas. The relationship is shown in FIG. As can be seen from FIG. 1, as the SO 3 and ammonia concentrations increase, the precipitation temperature of ammonium sulfate increases.
　石炭焚きボイラーの燃焼排ガスでは、一般的にＳＯｘ濃度は１００ｐｐｍであるためＳ０３濃度はその１０％の１０ｐｐｍ、ＮＯｘ濃度は５００ｐｐｍであるためアンモニア濃度は最大５００ｐｐｍである。この条件における硫安の析出温度は約２５０℃となる。この時の排ガス温度は通常３００～４００℃であり、硫安の析出温度２５０℃より高いため触媒上への硫安の析出は起こらず、安定した触媒性能を維持することができる。
一方、舶用機関から排出されている排ガスは燃料がＣ重油であるため排ガス中のＳＯｘ濃度が１０００ｐｐｍ、のＮＯｘ濃度も１０００ｐｐｍと高く、硫安の析出温度は約２８０℃と高くなる。しかし、排ガス温度は２５０℃と低いため、この条件では硫安が析出し、安定した触媒性能を維持することができない。 The flue gas of a coal-fired boiler, generally SOx concentration S0 3 concentration thereof of 10% 10ppm for a 100 ppm, ammonia concentration for a NOx concentration is 500ppm is maximum 500ppm. The precipitation temperature of ammonium sulfate under this condition is about 250 ° C. The exhaust gas temperature at this time is usually 300 to 400 ° C., and since the ammonium sulfate precipitation temperature is higher than 250 ° C., ammonium sulfate does not precipitate on the catalyst, and stable catalyst performance can be maintained.
On the other hand, since the exhaust gas discharged from the marine engine is C heavy oil, the SOx concentration in the exhaust gas is 1000 ppm, the NOx concentration is as high as 1000 ppm, and the precipitation temperature of ammonium sulfate is as high as about 280 ° C. However, since the exhaust gas temperature is as low as 250 ° C., ammonium sulfate precipitates under these conditions, and stable catalyst performance cannot be maintained.
　従って、舶用機関排ガスを上記選択的接触還元法で処理するには排ガス温度を硫安析出温度以上に加熱する必要がある。
高濃度のＳＯｘおよびＮＯｘが存在し、排ガス温度が低い舶用機関排ガスの処理にアンモニアＳＣＲ触媒を使用するには硫安の析出温度を排ガス温度以下にする必要がある。硫安の析出温度は図１に示されるとおりＳ０３濃度とアンモニア濃度で決定される。アンモニア濃度は排ガス中のNOｘ濃度と目標脱硝率で決まるため、この値を低減することできない。したがって、排ガス温度が低い舶用機関ではアンモニアＳＣＲ法を使用することができない。 Therefore, in order to treat marine engine exhaust gas by the selective catalytic reduction method, it is necessary to heat the exhaust gas temperature to a temperature higher than the ammonium sulfate precipitation temperature.
In order to use an ammonia SCR catalyst for the treatment of marine engine exhaust gas having a high concentration of SOx and NOx and a low exhaust gas temperature, it is necessary to set the precipitation temperature of ammonium sulfate below the exhaust gas temperature. Precipitation temperature of ammonium sulfate is determined by S0 3 concentration and ammonia concentration as shown in FIG. Since the ammonia concentration is determined by the NOx concentration in the exhaust gas and the target denitration rate, this value cannot be reduced. Therefore, the ammonia SCR method cannot be used in a marine engine having a low exhaust gas temperature.
　アンモニアＳＣＲ法以外の脱硝方法としては、イオン導電性を有する金属複合酸化物からなる触媒等にＮＯｘを接触させるだけで窒素と酸素に分解する直接分解法（特許文献１など）や、還元剤として炭化水素を用い触媒にＮＯｘを接触させる脱硝方法があり、後者の触媒としてβゼオライトに金属を担持した触媒（特許文献２）や、アルミナ、硫酸アルミニウム、銀を主成分とする触媒（特許文献３）が知られている。しかし、反応温度は前者の方法では６００℃以上と高く、後者の方法では３５０℃程度である。 As a denitration method other than the ammonia SCR method, a direct decomposition method (such as Patent Document 1) in which NOx is simply brought into contact with a catalyst made of a metal composite oxide having ionic conductivity and decomposed into nitrogen and oxygen, or as a reducing agent. There is a denitration method in which NOx is brought into contact with a catalyst using hydrocarbons. As the latter catalyst, a catalyst in which a metal is supported on β zeolite (Patent Document 2), a catalyst mainly composed of alumina, aluminum sulfate, and silver (Patent Document 3) )It has been known. However, the reaction temperature is as high as 600 ° C. or more in the former method, and about 350 ° C. in the latter method.
　特許文献４には還元剤を用いない直接分解法が記載され、その対照例３には水素化したゼオライトに金属を担持させた触媒を用い、温度４００℃でＮＯｘ除去率は１０％以下であったことが示されている。しかし、この触媒では金属担持後も金属の酸点より強い酸点であるプロトン酸点が一部残るため、ＮＯはより強い酸点を優先的にアタックし、脱硝反応が進行しにくい。 Patent Document 4 describes a direct cracking method that does not use a reducing agent. In Comparative Example 3, a catalyst in which a metal is supported on hydrogenated zeolite is used, and the NOx removal rate is 10% or less at a temperature of 400 ° C. It has been shown. However, in this catalyst, a part of the proton acid point, which is an acid point stronger than the metal acid point, remains even after the metal is supported, so that NO preferentially attacks the stronger acid point and the denitration reaction does not proceed easily.
特開平１１－１５１４４０号公報Japanese Patent Laid-Open No. 11-151440 特開２００４－３５８４５４号公報JP 2004-358454 A 特開２０１０－２９７８３号公報JP 2010-29783 A 特公平０７－１０６３００号公報Japanese Patent Publication No. 07-106300
　上述のとおり、従来、舶用機関のように温度２５０℃付近の低温排ガスに対しては実用的な触媒性能を有する触媒は見い出せていなかった。 As described above, conventionally, no catalyst having practical catalytic performance has been found for low-temperature exhaust gas at a temperature of around 250 ° C. like a marine engine.
　その原因は、直接分解法および還元除去法では、触媒上でＮＯが分解した際に生成する酸素が触媒表面から除去されないことにある。従って、触媒表面の酸素を除去することが可能となれば直接分解法および還元除去法が可能と考えられる。 The cause is that in the direct decomposition method and the reduction removal method, oxygen generated when NO is decomposed on the catalyst is not removed from the catalyst surface. Therefore, if it is possible to remove oxygen on the catalyst surface, it is considered that a direct decomposition method and a reduction removal method are possible.
　
　本発明者らは検討を重ねた結果、ＭＦＩ型ゼオライトをＦｅ、ＣｏおよびＭｎのうちの少なくとも一種でイオン交換させた触媒に排ガスを温度２００～３５０℃、好ましくは２２０～３２０℃、より好ましくは２３０～３００℃、より好ましくは２３０～２７０℃の範囲で接触させることで効果的にNOｘを低減できることを見出した。
As a result of repeated investigations, the present inventors have found that exhaust gas is heated at a temperature of 200 to 350 ° C., preferably 220 to 320 ° C., more preferably a catalyst obtained by ion-exchange of MFI type zeolite with at least one of Fe, Co, and Mn. It has been found that NOx can be effectively reduced by contacting in the range of 230 to 300 ° C., more preferably 230 to 270 ° C.
　ＭＦＩ型ゼオライトは市販品であってよい。 MFI-type zeolite may be a commercially available product.
　イオン交換方法は、たとえば、Ｆｅ、Ｃｏおよび／またはＭｎの前駆体化合物を含む水溶液にＭＦＩ型ゼオライトを懸濁させ、濾過、洗浄の後、該ゼオライトを乾燥ついで焼成する方法であってよい。前駆体化合物はＦｅ、Ｃｏおよび／またはＭｎの無機酸塩（例えば硝酸塩、硫酸塩）、有機酸塩（例えば酢酸塩）であってよい。 The ion exchange method may be, for example, a method in which MFI-type zeolite is suspended in an aqueous solution containing Fe, Co and / or Mn precursor compounds, and the zeolite is dried and then calcined after filtration and washing. The precursor compound may be an inorganic acid salt (eg, nitrate, sulfate) or an organic acid salt (eg, acetate) of Fe, Co and / or Mn.
　Ｆｅ、ＣｏおよびＭｎのうちの少なくとも一種でイオン交換させた後のゼオライトには、ナトリウム、上記イオン交換金属、プロトンの部分に酸点があり、各酸点における酸強度はプロトン＞イオン交換金属＞ナトリウムの順となる。脱硝反応は、イオン交換金属の酸点で一酸化窒素が分解されることで進行する。 The zeolite after ion exchange with at least one of Fe, Co, and Mn has an acid point in the sodium, the above ion exchange metal, and the proton, and the acid strength at each acid point is proton> ion exchange metal> Sodium order. The denitration reaction proceeds by decomposing nitric oxide at the acid sites of the ion exchange metal.
硫酸アンモニウム／硫酸水素アンモニウムの析出温度が三酸化硫黄濃度とアンモニア濃度に関係することを示すグラフである。It is a graph which shows that the precipitation temperature of ammonium sulfate / ammonium hydrogen sulfate is related to sulfur trioxide concentration and ammonia concentration. 触媒の性能評価を行うための試験装置を示す概略フロー図である。It is a schematic flowchart which shows the test apparatus for performing the performance evaluation of a catalyst.
　次に本発明を実施例に基づいて具体的に説明する。
実施例１
Ｆｅ／ゼオライト触媒
 市販のＭＦＩ型ゼオライト４ｇを０．０５ＭのＦｅ（ＮＯ３）３・９Ｈ２０水溶液５００ｍ１に５０℃で６時間懸濁させた後、これを濾過、洗浄し、１２０℃で１２時間乾燥し、さらに４００℃で６時間焼成した。こうしてＦｅイオン交換ゼオライト触媒を得た。この触媒のＦｅ担持量は２．０ｗｔ％であった。
実施例２
Ｃｏ／ゼオライト触媒
　市販のＭＦＩ型ゼオライト４ｇを０．０１ＭのＣｏ（ＮO３）２水溶液５００ｍｌに８０℃で１８時間懸濁させた後、これを濾過、洗浄し、１２０℃で１２時間乾燥し、さらに５００℃で４時間焼成した。こうしてＣｏイオン交換ゼオライト触媒を得た。この触媒のＣｏ担持量は２．３１ｗｔ％であった。
実施例３
Ｍｎ／ゼオライト触媒
　市販のＭＦＩ型ゼオライト４ｇを０．０１ＭのＭｎ（ＣＨ３ＣＯＯ）２水溶液５００ｍ１に８０℃で１８時間懸濁させた後、これを濾過、洗浄し、１２０℃で１２時間乾燥し、さらに５００℃で４時間焼成した。こうしてMnイオン交換ゼオライト触媒を得た。この触媒のＭｎ担持量は４．０ｗｔ％であった。
比較例１
　Ａ１２０３　４ｇを０．０５ＭのＦｅ（ＮO３）３・９Ｈ２０水溶液５００ｍｌに８０℃で６時間懸濁させた後、これを濾過し、１２０℃で１２時間乾燥し、さらに４００℃で６時間焼成した。こうしてＦｅ担持Ａ１２０３触媒を得た。この触媒のＦｅ担持量は２．０ｗｔ％であった。
比較例２
　市販のβ型ゼオライト４ｇを０．０１ＭのＣｏ（ＮＯ３）２水溶液５００ｍ１に８０℃で１８時間懸濁させた後、これを濾過、洗浄し、１２０℃で１２時間乾燥し、さらに５００℃で４時間焼成した。こうしてＣｏイオン交換ゼオライト触媒を得た。この触媒のＣｏ担持量は３．８ｗｔ％であった。
触媒性能評価
　上記で得られた触媒をプレス成形後に粉砕し、メッシュサイズ２８から１４に整粒し、得られた粒状触媒を、図２に示す試験装置を用いる評価試験に供した。図２中，(1)は脱硝反応器、(2)は蒸発器、(3)はポンプ、(4)は水槽である。試験条件を表１に示す。 Next, the present invention will be specifically described based on examples.
Example 1
After Fe / zeolite catalyst commercially available MFI zeolite 4g of 0.05M of Fe (NO 3) 3 · 9H 2 0 aqueous 500m1, and the suspension 6 hours at 50 ° C., filtered, washed, 12 at 120 ° C. It was dried for 4 hours and then calcined at 400 ° C. for 6 hours. Thus, an Fe ion exchange zeolite catalyst was obtained. The Fe loading of this catalyst was 2.0 wt%.
Example 2
Co / zeolite catalyst 4 g of commercially available MFI type zeolite was suspended in 500 ml of 0.01 M Co (NO 3 ) 2 aqueous solution at 80 ° C. for 18 hours, then filtered, washed, and dried at 120 ° C. for 12 hours. Furthermore, it baked at 500 degreeC for 4 hours. In this way, a Co ion exchange zeolite catalyst was obtained. The amount of Co supported by this catalyst was 2.31 wt%.
Example 3
Mn / zeolite catalyst 4 g of commercially available MFI-type zeolite was suspended in 500 ml of 0.01M Mn (CH 3 COO) 2 aqueous solution at 80 ° C. for 18 hours, then filtered, washed and dried at 120 ° C. for 12 hours. Further, it was calcined at 500 ° C. for 4 hours. In this way, a Mn ion exchange zeolite catalyst was obtained. The amount of Mn supported by this catalyst was 4.0 wt%.
Comparative Example 1
A1 2 0 3 4g of 0.05M of Fe (NO 3) 3 · 9H 2 0 was suspended 6 hours at 80 ° C. in an aqueous solution 500 ml, which was filtered, dried at 120 ° C. 12 hours, further 400 ° C. For 6 hours. Thus, an Fe-supported A1 2 0 3 catalyst was obtained. The Fe loading of this catalyst was 2.0 wt%.
Comparative Example 2
After suspending 4 g of commercially available β-type zeolite in 500 ml of 0.01 M Co (NO 3 ) 2 aqueous solution at 80 ° C. for 18 hours, this was filtered, washed, dried at 120 ° C. for 12 hours, and further at 500 ° C. Baked for 4 hours. In this way, a Co ion exchange zeolite catalyst was obtained. The amount of Co supported by this catalyst was 3.8 wt%.
Evaluation of Catalyst Performance The catalyst obtained above was pulverized after press molding and sized to a mesh size of 28 to 14, and the obtained granular catalyst was subjected to an evaluation test using the test apparatus shown in FIG. In FIG. 2, (1) is a denitration reactor, (2) is an evaporator, (3) is a pump, and (4) is a water tank. Table 1 shows the test conditions.
Figure JPOXMLDOC01-appb-T000001
 　表２に試験結果を示す。出口でＮＯ２が生じているのは、平衡の関係からである。供給ガス中の空気中の酸素によってＮＯがＮＯ２に酸化される。触媒量を増すことで脱硝率を向上させることができる。
Figure JPOXMLDOC01-appb-T000001
 Table 2 shows the test results. The reason why NO 2 is generated at the outlet is due to the equilibrium relationship. NO is oxidized to NO 2 by oxygen in the air in the supply gas. The denitration rate can be improved by increasing the amount of catalyst.
Figure JPOXMLDOC01-appb-T000002
 　実施例においてはいずれの触媒においても比較例より高い脱硝率が得られており、本発明の触媒が反応温度２５０℃で高い触媒性能を有することがわかる。
　　 
Figure JPOXMLDOC01-appb-T000002
 In the examples, the denitration rate higher than that of the comparative example was obtained in any of the catalysts, indicating that the catalyst of the present invention has a high catalytic performance at a reaction temperature of 250 ° C.

Claims (3)

  1. ＭＦＩ型ゼオライトをＦｅ、ＣｏおよびＭｎのうちの少なくとも一種でイオン交換させたことを特徴とする、燃焼排ガス中の窒素酸化物の除去触媒。 A catalyst for removing nitrogen oxides in combustion exhaust gas, wherein MFI-type zeolite is ion-exchanged with at least one of Fe, Co, and Mn.
  2. 請求項１記載の触媒に排ガスを温度２００～３５０℃の範囲で接触させることを特徴とする、排ガス中の窒素酸化物の除去方法。 A method for removing nitrogen oxides in exhaust gas, wherein the exhaust gas is brought into contact with the catalyst according to claim 1 at a temperature in the range of 200 to 350 ° C.
  3. 　触媒に排ガスを温度２２０～３２０℃の範囲で接触させることを特徴とする請求項２記載の方法。 The method according to claim 2, wherein the exhaust gas is brought into contact with the catalyst at a temperature in the range of 220 to 320 ° C.
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