JP2013136034A - Urea scr catalyst and exhaust gas post-treatment system - Google Patents

Urea scr catalyst and exhaust gas post-treatment system Download PDF

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JP2013136034A
JP2013136034A JP2011288912A JP2011288912A JP2013136034A JP 2013136034 A JP2013136034 A JP 2013136034A JP 2011288912 A JP2011288912 A JP 2011288912A JP 2011288912 A JP2011288912 A JP 2011288912A JP 2013136034 A JP2013136034 A JP 2013136034A
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iron silicate
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urea scr
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JP5817522B2 (en
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Kokichi Maekawa
弘吉 前川
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Isuzu Motors Ltd
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    • 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
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
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    • 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
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Abstract

PROBLEM TO BE SOLVED: To provide an urea SCR catalyst capable of highly actively eliminating NOx discharged from an engine at low temperature and having high water and heat durability and an exhaust gas post-treatment system.SOLUTION: In the urea SCR catalyst for reducing NOx in exhaust gas with ammonia, heating treatment is performed after Cu ions are introduced to Al isomorphous substitution iron silicate in which Al ions are introduced into an iron silicate skeleton, in particular iron silicate beta zeolite by using the ion exchange method.

Description

本発明は、ディーゼル排ガスに含まれるＮＯｘを無害化するための尿素ＳＣＲ触媒に係り、特に、高活性で水熱耐久性がありしかも低温でのＮＯｘ吸着特性に優れた尿素ＳＣＲ触媒及び排ガスの後処理システムに関するものである。   The present invention relates to a urea SCR catalyst for detoxifying NOx contained in diesel exhaust gas, and more particularly to a urea SCR catalyst having high activity, hydrothermal durability, and excellent NOx adsorption characteristics at low temperatures, and after the exhaust gas. It relates to a processing system.

ディーゼル排ガスに含まれるＮＯｘを無害化する装置の１つとして、尿素ＳＣＲ（Selective Catalytic Reduction；以下ＳＣＲと略記）が実用化されている。   As one device for detoxifying NOx contained in diesel exhaust gas, urea SCR (Selective Catalytic Reduction; hereinafter abbreviated as SCR) has been put into practical use.

図５は、特許文献１に示されたディーゼル排ガスの後処理システムを示し、ディーゼルエンジンの排ガス管１０に酸化触媒（ＤＯＣ）反応器１１、ディーゼルパティキュレートフィルタ（ＤＰＦ）１２、ＳＣＲ反応器１３が順に接続されてディーゼル排ガスの後処理システムが構成される。   FIG. 5 shows a diesel exhaust gas aftertreatment system disclosed in Patent Document 1, in which an oxidation catalyst (DOC) reactor 11, a diesel particulate filter (DPF) 12, and an SCR reactor 13 are provided in an exhaust gas pipe 10 of a diesel engine. The diesel exhaust gas aftertreatment system is connected in order.

ディーゼルエンジンからの排ガスは、酸化触媒反応器１１内で、排ガス中の未燃焼燃料（ＨＣ）や、一酸化炭素（ＣＯ）等が酸化された後、排ガス中のＰＭ（パティキュレートマター）がディーゼルパティキュレートフィルタ（ＤＰＦ）１２で捕集される。次に、排ガス中の窒素酸化物（ＮＯｘ）は、ＳＣＲ反応器１３の入口側で噴射された尿素水１４の加水分解で生じたアンモニアとＳＣＲ反応器１３内のＳＣＲ触媒で反応して窒素と水とに還元されて無害化される。   Exhaust gas from the diesel engine is oxidized in the oxidation catalyst reactor 11 after unburned fuel (HC), carbon monoxide (CO), etc. in the exhaust gas are oxidized, and then PM (particulate matter) in the exhaust gas is diesel. It is collected by a particulate filter (DPF) 12. Next, nitrogen oxide (NOx) in the exhaust gas reacts with ammonia generated by hydrolysis of the urea water 14 injected at the inlet side of the SCR reactor 13 by the SCR catalyst in the SCR reactor 13 to react with nitrogen. It is reduced to water and detoxified.

ＳＣＲ反応器１３に用いられるＳＣＲ触媒としては、一般にゼオライト触媒が用いられており（特許文献２）、このゼオライト触媒を含むスラリーをセラミックハニカムなどの担体に塗布したもの或いはその成型体がＳＣＲコンバータとして用いられる。   As the SCR catalyst used in the SCR reactor 13, a zeolite catalyst is generally used (Patent Document 2). A slurry containing the zeolite catalyst applied to a carrier such as a ceramic honeycomb or a molded body thereof is used as an SCR converter. Used.

従来、ＳＣＲ触媒用ゼオライトとして鉄イオン交換アルミノシリケート（以下従来触媒と表記する）が広く用いられており、この触媒を用いて、尿素水が加水分解して生じるアンモニアを還元剤として作用させることで、ディーゼル排ガス中の窒素酸化物（ＮＯｘ）を除去することができる。   Conventionally, iron ion-exchange aluminosilicate (hereinafter referred to as conventional catalyst) has been widely used as a zeolite for SCR catalysts. By using this catalyst, ammonia generated by hydrolysis of urea water acts as a reducing agent. Nitrogen oxide (NOx) in diesel exhaust gas can be removed.

特開２０１１−１５２４９６号公報JP 2011-152696 A 特開２００７−２９６５２１号公報JP 2007-296521 A 特開２００７−２２２７４２号公報JP 2007-222742 A

E.A. Urquieta-Gonzalez, L. Martins, R.P.S. Peguin, M.S. Batista, Materials Reserch, 5, 321-327 (2002)E.A.Urquieta-Gonzalez, L. Martins, R.P.S.Peguin, M.S.Batista, Materials Reserch, 5, 321-327 (2002) O. P. Krivoruchko, N. T. Vasenin, T. V. Larina, V. F. Anufruenko, and Academician V. N. Parmon, DOKLADY PHYSICAL CHEMISTRY, 430, 13-16 (2010)O. P. Krivoruchko, N. T. Vasenin, T. V. Larina, V. F. Anufruenko, and Academician V. N. Parmon, DOKLADY PHYSICAL CHEMISTRY, 430, 13-16 (2010) Yihua Zhang, Ian J. Drake, and Alexis T. Bell, Chem. Mater., 18, 2347-2356 (2006)Yihua Zhang, Ian J. Drake, and Alexis T. Bell, Chem. Mater., 18, 2347-2356 (2006)

しかしながら、上記の従来触媒は、低温（〜１６０℃程度）においては、ＮＯｘ浄化能力が十分ではないため、エンジン始動直後、即ち低温時においては、エンジンから排出されたＮＯｘの大部分が浄化されずに大気中に放出される問題がある。従って、低温時のＮＯｘ排出を抑制するためには、低温時のＮＯｘ浄化能力を高めるか、或いはＮＯｘ吸着剤を用いてＮＯｘを保持するなどの方策が必要となる。   However, since the above conventional catalyst does not have sufficient NOx purification capability at low temperatures (about 160 ° C.), most of the NOx discharged from the engine is not purified immediately after engine startup, that is, at low temperatures. There is a problem of being released into the atmosphere. Therefore, in order to suppress NOx emission at low temperatures, measures such as increasing the NOx purification capability at low temperatures or holding NOx using a NOx adsorbent are necessary.

本発明者は、特願２０１１−２４３３４８（発明の名称：尿素ＳＣＲ触媒及び排ガスの後処理システム）にて、鉄シリケート骨格内にＡｌイオンを導入した尿素ＳＣＲ触媒を発明した。この先願の尿素ＳＣＲ触媒は、高いＮＯｘ浄化活性ならびに水熱耐久性を有し、しかも従来の触媒と同等のＮＯｘ吸着特性を有するものであるが、低温活性に未だ改良の余地があることがわかった。   The present inventor invented a urea SCR catalyst in which Al ions are introduced into an iron silicate skeleton in Japanese Patent Application No. 2011-243348 (name of invention: urea SCR catalyst and exhaust gas aftertreatment system). This prior application urea SCR catalyst has high NOx purification activity and hydrothermal durability, and has NOx adsorption characteristics equivalent to those of conventional catalysts, but there is still room for improvement in low-temperature activity. It was.

そこで、本発明の目的は、上記課題を解決し、低温時にエンジンから排出されるＮＯｘを浄化できる尿素ＳＣＲ触媒及び排ガスの後処理システムを提供することにある。   Therefore, an object of the present invention is to provide a urea SCR catalyst and an exhaust gas aftertreatment system that can solve the above-described problems and purify NOx discharged from the engine at a low temperature.

上記目的を達成するために請求項１の発明は、排ガス中のＮＯｘをアンモニアで還元するための尿素ＳＣＲ触媒において、鉄シリケート骨格内にＡｌイオンを導入したＡｌ同型置換鉄シリケートに、Ｃｕイオンを導入したことを特徴とする尿素ＳＣＲ触媒である。   In order to achieve the above object, the invention of claim 1 is the urea SCR catalyst for reducing NOx in the exhaust gas with ammonia, and Cu ions are introduced into the Al isomorphous substituted iron silicate in which Al ions are introduced into the iron silicate skeleton. It is a urea SCR catalyst characterized by having been introduced.

請求項２の発明は、Ａｌ同型置換鉄シリケートに導入するＣｕ導入量は、Ａｌ同型置換鉄シリケートに対し０．４〜６．０ｍａｓｓ％とした請求項１記載の尿素ＳＣＲ触媒である。   The invention according to claim 2 is the urea SCR catalyst according to claim 1, wherein the amount of Cu introduced into the Al isomorphous substituted iron silicate is 0.4 to 6.0 mass% with respect to the Al isomorphous substituted iron silicate.

請求項３の発明は、鉄シリケートベータゼオライトと硝酸アルミニウムと蒸留水を混ぜ、これを還流してＡｌ同型置換鉄シリケートとし、Ａｌ同型置換鉄シリケートにイオン交換によってＣｕイオンを導入し、これを５００℃以上で焼成した請求項１記載の尿素ＳＣＲ触媒である。   In the invention of claim 3, iron silicate beta zeolite, aluminum nitrate and distilled water are mixed and refluxed to obtain an Al isomorphous substituted iron silicate, and Cu ions are introduced into the Al isomorphous substituted iron silicate by ion exchange. The urea SCR catalyst according to claim 1, which is calcined at a temperature of not lower than ° C.

請求項４の発明は、ディーゼルエンジンの排ガス管にＳＣＲ反応器を接続し、そのＳＣＲ反応器の上流側で尿素水を噴射して排ガス中のＮＯｘを除去する排ガスの後処理システムにおいて、ＳＣＲ反応器の触媒に、鉄シリケート骨格内にＡｌイオンを導入したＡｌ同型置換鉄シリケートに、Ｃｕイオンを導入した尿素ＳＣＲ触媒を用いることを特徴とする排ガスの後処理システムである。   According to a fourth aspect of the present invention, there is provided an SCR reaction system in an exhaust gas aftertreatment system in which an SCR reactor is connected to an exhaust gas pipe of a diesel engine and urea water is injected upstream of the SCR reactor to remove NOx in the exhaust gas. The exhaust gas aftertreatment system is characterized in that a urea SCR catalyst in which Cu ions are introduced into an Al isomorphous substituted iron silicate in which Al ions are introduced into an iron silicate skeleton is used as the catalyst of the vessel.

本発明は、Ａｌ同型置換鉄シリケートにＣｕイオンを導入することによって、低温時の高いＮＯｘ浄化活性ならびに水熱耐久性を有し、しかも従来の触媒と同等のＮＯｘ吸着特性を有するＳＣＲ用の触媒とすることができるという優れた効果を発揮する。   The present invention provides a catalyst for SCR having high NOx purification activity at low temperature and hydrothermal durability by introducing Cu ions into Al isomorphous substituted iron silicate and having NOx adsorption characteristics equivalent to conventional catalysts. The excellent effect of being able to be demonstrated.

本発明の尿素ＳＣＲ触媒の骨格構造を説明する図である。It is a figure explaining the frame | skeleton structure of the urea SCR catalyst of this invention. 本発明の尿素ＳＣＲ触媒と先願のＡｌ同型置換鉄シリケートからなる尿素ＳＣＲ触媒と従来の鉄ゼオライトＳＣＲ触媒のＮＯｘ浄化率とＮＯｘ吸着率を示す図である。It is a figure which shows the NOx purification rate and NOx adsorption rate of the urea SCR catalyst which consists of the urea SCR catalyst of this invention, the Al isomorphous substituted iron silicate of a prior application, and the conventional iron zeolite SCR catalyst. 従来のゼオライト（アルミノシリケート）から鉄ゼオライトＳＣＲ触媒を製造する際の骨格構造を説明する図である。It is a figure explaining the frame | skeleton structure at the time of manufacturing an iron zeolite SCR catalyst from the conventional zeolite (aluminosilicate). 従来の鉄シリケートＳＣＲ触媒の骨格構造（ａ）と骨格内のＦｅが離脱した骨格構造（ｂ）とＦｅが離脱した骨格にＡｌを導入したＡｌ同型置換鉄シリケートの骨格構造（ｃ）を説明する図である。A skeleton structure (a) of a conventional iron silicate SCR catalyst, a skeleton structure (b) from which Fe in the skeleton is released, and a skeleton structure (c) of an Al isomorphous substituted iron silicate in which Al is introduced into the skeleton from which Fe is released FIG. ディーゼルエンジンの排ガスの後処理システムを示す図である。It is a figure which shows the aftertreatment system of the exhaust gas of a diesel engine.

以下、本発明の好適な一実施の形態を添付図面に基づいて詳述する。   A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

図１は、本発明の尿素ＳＣＲ触媒の骨格構造を示したもので、出発原料として鉄シリケートベータゼオライトを用い、その骨格構造内からのＦｅの脱離によって生じた空孔（シラノールネスト）にＡｌを導入してＡｌ同型置換鉄シリケートとし、そのＡｌ同型置換鉄シリケートに、イオン交換処理によりＣｕイオンを導入するものである。   FIG. 1 shows a skeleton structure of the urea SCR catalyst of the present invention. Iron silicate beta zeolite is used as a starting material, and vacancies (silanol nests) generated by the elimination of Fe from the skeleton structure are Al. To form an Al isomorphous substituted iron silicate, and Cu ions are introduced into the Al isomorphous substituted iron silicate by ion exchange treatment.

先ず、鉄シリケートベータゼオライトからＡｌ同型置換鉄シリケートとすることで、Ｆｅが抜けた空孔にＡｌによる活性点の補填が行えると共に水熱耐久性の強化が行え、かつ従来の鉄シリケート触媒と同等のＮＯｘ吸着特性を維持できるものであり、本発明は、このＡｌ同型置換鉄シリケートにＣｕイオンを導入することで、低温活性を改良するものである。   First, Al isomorphous substituted iron silicate from iron silicate beta zeolite can compensate for active sites by Al in pores from which Fe has been removed, and can enhance hydrothermal durability, and is equivalent to conventional iron silicate catalysts. Thus, the present invention improves the low-temperature activity by introducing Cu ions into the Al isomorphous substituted iron silicate.

ゼオライトは、シリカ（ＳｉＯ2）を基本とする網目状の骨格構造から成る。この骨格内に、Ａｌ，Ｂ等の３価の陽イオンが置換されることによって負電荷が生じるが、その対イオンがプロトン（Ｈ+）の場合、このサイトが酸点として機能する。この酸点はＳＣＲ反応に必要なアンモニアを吸着保持するために不可欠である。 Zeolite has a network-like skeleton structure based on silica (SiO 2 ). A negative charge is generated by substituting trivalent cations such as Al and B in this skeleton. When the counter ion is a proton (H + ), this site functions as an acid point. This acid point is indispensable for adsorbing and holding ammonia necessary for the SCR reaction.

従来のゼオライト触媒は、図３（ａ）に示した骨格の一部がＡｌによって置換されたアルミノシリケートを基本に、対イオンがＦｅイオンに交換された構造の鉄ゼオライトになっている（図３（ｂ））。   A conventional zeolite catalyst is based on an aluminosilicate in which a part of the skeleton shown in FIG. 3 (a) is replaced by Al, and is an iron zeolite having a structure in which counter ions are exchanged with Fe ions (FIG. 3). (B)).

先願のＡｌ同型置換鉄シリケートは、図４（ａ）に示すように、骨格の一部がＦｅで置換された鉄シリケートの骨格構造から、熱処理や使用による劣化で、図４（ｂ）に示すように、鉄シリケートの骨格内からＦｅの離脱によって生じた空孔（シラノールネスト）に、図４（ｃ）に示すようにＡｌを導入することによって鉄シリケートの骨格構造内にＦｅの一部をＡｌ同型置換した構造である。   As shown in FIG. 4 (a), the Al isomorphous substituted iron silicate of the prior application is shown in FIG. 4 (b) due to deterioration due to heat treatment and use from the skeleton structure of iron silicate in which a part of the skeleton is substituted with Fe. As shown in FIG. 4 (c), Al is introduced into the vacancies (silanol nests) generated by the detachment of Fe from the skeleton of the iron silicate, so that a part of Fe is contained in the skeleton structure of the iron silicate. Is a structure in which Al is isomorphously substituted.

この先願のＡｌ同型置換鉄シリケートは、従来触媒よりも高いＮＯｘ浄化性能ならびにＮＯｘ吸着特性を保持しながら、高いＮＯｘ浄化性能ならびに水熱耐久性を付与したＳＣＲ触媒とすることができるものである。   The Al-substituted iron silicate of the prior application can be an SCR catalyst that has high NOx purification performance and hydrothermal durability while maintaining higher NOx purification performance and NOx adsorption characteristics than conventional catalysts.

しかし、先願のＡｌ同型置換鉄シリケートは、低温活性に問題を残していることがわかった。   However, it was found that the Al isomorphous substituted iron silicate of the prior application left a problem in low temperature activity.

そこで本発明では、Ａｌ同型置換の手法によって鉄シリケート骨格内にＡｌを導入して酸点を増補し、さらにこのＡｌ同型置換鉄シリケートにＣｕイオンを導入することによって、低温活性、すなわち低温時のＮＯｘ浄化性能を向上させ、Ａｌ同型置換鉄シリケートの特長である水熱耐久性を兼ね備えた尿素ＳＣＲ触媒としたものである。   Therefore, in the present invention, by introducing Al into the iron silicate skeleton by the Al isomorphous substitution technique to supplement the acid sites, and further introducing Cu ions into the Al isomorphous substituted iron silicate, low temperature activity, that is, at low temperatures. This is a urea SCR catalyst that improves NOx purification performance and also has hydrothermal durability, which is a feature of Al isomorphous substituted iron silicate.

以下に本発明の尿素ＳＣＲ触媒について、さらに詳しく説明する。   Hereinafter, the urea SCR catalyst of the present invention will be described in more detail.

鉄シリケートの合成；
鉄シリケートは、コロイダルシリカ、シリコンアルキシド、ヒュームドシリカ等のシリカ源と、テトラエチルアンモニウムヒドロキシド（ＴＥＡＯＨ）水溶液等のベータ構造を与える構造規制有機物質（ＳＤＡ）水溶液と、水酸化ナトリウム、水酸化カリウム等のアルカリ金属源、硝酸鉄、硫酸鉄、塩化鉄等の鉄源と、蒸留水とから合成する。 Synthesis of iron silicates;
Iron silicate is composed of a silica source such as colloidal silica, silicon alkoxide, and fumed silica, an aqueous structure-regulating organic substance (SDA) solution that provides a beta structure such as an aqueous tetraethylammonium hydroxide (TEAOH) solution, sodium hydroxide, and hydroxide. It is synthesized from an alkali metal source such as potassium, an iron source such as iron nitrate, iron sulfate, or iron chloride, and distilled water.

具体的には、シリカ源としてコロイダルシリカ（Ｌｕｄｏｘ ＨＳ−４０）、構造規制有機物質（ＳＤＡ）として、テトラエチルアンモニウムヒドロキシド（３５ｍａｓｓ％水溶液、以下ＴＥＡＯＨという）、アルカリ金属源としてＮａＯＨ（２５ｍａｓｓ％水溶液）、鉄源として硝酸鉄（III）九水和物および蒸留水を用いた。   Specifically, colloidal silica (Ludox HS-40) as a silica source, tetraethylammonium hydroxide (35 mass% aqueous solution, hereinafter referred to as TEAOH) as a structure-regulated organic substance (SDA), and NaOH (25 mass% aqueous solution) as an alkali metal source As an iron source, iron (III) nitrate nonahydrate and distilled water were used.

テフロン（登録商標）容器に、ＮａＯＨ水溶液とＴＥＡＯＨを加えて室温で１５分間撹拌後、コロイダルシリカを加えて４０分室温で撹拌した。ここに、硝酸鉄を蒸留水で溶解した水溶液を撹拌しながら滴下して室温で４時間撹拌し、出発ゲルを得た。   To a Teflon (registered trademark) container, an aqueous NaOH solution and TEAOH were added and stirred at room temperature for 15 minutes, and then colloidal silica was added and stirred at room temperature for 40 minutes. The aqueous solution which melt | dissolved iron nitrate with distilled water was dripped here, stirring, and it stirred at room temperature for 4 hours, and obtained the starting gel.

このゲルの組成モル比は、１（ＳｉＯ2）：０．３７（ＴＥＡＯＨ）：０．０５（Ｆｅ2Ｏ3）：０．３（ＮａＯＨ）：２０（Ｈ2Ｏ）である。 The compositional molar ratio of this gel is 1 (SiO 2 ): 0.37 (TEAOH): 0.05 (Fe 2 O 3 ): 0.3 (NaOH): 20 (H 2 O).

得られたゲルをオートクレーブに移し、１５０℃のオーブン中で１４４時間静置して水熱合成を行った。得られた生成物を室温まで冷却した後、濾過し、蒸留水で洗浄して白色粉末を得た。   The obtained gel was transferred to an autoclave and allowed to stand in an oven at 150 ° C. for 144 hours for hydrothermal synthesis. The obtained product was cooled to room temperature, filtered, and washed with distilled water to obtain a white powder.

出発ゲルの組成比は、ＳｉＯ2１ｍｏｌに対し、Ｆｅ導入量は、Ｆｅ2Ｏ3０．００５〜０．０３ｍｏｌが好ましく、より好ましくは０．０１〜０．０２ｍｏｌである。 The composition ratio of the starting gel, to SiO 2 1 mol, Fe incorporated in a quantity of, Fe 2 O 3 0.005~0.03mol, and more preferably from 0.01～0.02Mol.

また、Ｆｅ源としては、硝酸鉄、硫酸鉄、塩化鉄、その他の３価の陽イオンＦｅ塩が適用可能である。シリカ源としては、コロイダルシリカ、シリコンアルキシド、ヒュームドシリカなどの非晶質シリカを用いることができる。   As the Fe source, iron nitrate, iron sulfate, iron chloride, and other trivalent cation Fe salts are applicable. As the silica source, amorphous silica such as colloidal silica, silicon alkoxide, or fumed silica can be used.

水熱合成反応時の加熱温度は、１３０℃以上１８０℃以下が好ましく、より好ましくは、１４０℃以上１６０℃以下である。また加熱時間は１２０時間以上１６０時間以下が好ましい。   The heating temperature during the hydrothermal synthesis reaction is preferably 130 ° C. or higher and 180 ° C. or lower, and more preferably 140 ° C. or higher and 160 ° C. or lower. The heating time is preferably 120 hours or longer and 160 hours or shorter.

Ａｌ導入方法：
Ａｌ同型置換の処理は次のようにして実施した。 Al introduction method:
The treatment of Al isomorphous replacement was performed as follows.

ベータ型鉄シリケート（［Ｆｅ］−Ｂｅｔａ）、Ａｌ（ＮＯ3）3・９Ｈ2Ｏおよび蒸留水を、［Ｆｅ］−Ｂｅｔａ：Ａｌ（ＮＯ3）3：Ｈ2Ｏ＝１：１：５０の質量比になるように混ぜ、８０℃のウォーターバスを用いて１８時間還流した。還流終了後、室温まで冷却し、濾過した後、蒸留水を用いて洗浄して褐色粉末を得た。 Beta-type iron silicate ([Fe] -Beta), Al (NO 3 ) 3 .9H 2 O and distilled water were mixed with [Fe] -Beta: Al (NO 3 ) 3 : H 2 O = 1: 1: 50. It mixed so that it might become mass ratio, and it recirculate | refluxed for 18 hours using the 80 degreeC water bath. After completion of the reflux, the mixture was cooled to room temperature, filtered, and washed with distilled water to obtain a brown powder.

このサンプルを、５５０℃で５時間焼成し、Ｃｕイオン交換前のＡｌ導入［Ｆｅ］−Ｂｅｔａを得た。   This sample was calcined at 550 ° C. for 5 hours to obtain Al-introduced [Fe] -Beta before Cu ion exchange.

このベータ型鉄シリケートに導入するＡｌイオンは、Ｆｅ離脱によって生じた空孔（シラノールネスト）を補填する量以上であればよく、ＳｉＯ2／Ａｌ2Ｏ3のモル比で２００以下であればよい。 The Al ions introduced into the beta-type iron silicate need only be in an amount that can compensate for voids (silanol nests) generated by Fe desorption, and may have a SiO 2 / Al 2 O 3 molar ratio of 200 or less. .

Ｃｕイオン交換方法：
Ａｌ同型置換鉄シリケート（Ａｌ導入鉄シリケート）のＣｕイオン交換方法としては、既知の方法を用いればよく、例えば非特許文献１、２に示された液相イオン交換法でも、非特許文献３に示された固相イオン交換法を用いてもよい。 Cu ion exchange method:
As a Cu ion exchange method of Al isomorphous substituted iron silicate (Al-introduced iron silicate), a known method may be used. For example, even in the liquid phase ion exchange method shown in Non-Patent Documents 1 and 2, Non-Patent Document 3 The indicated solid phase ion exchange method may be used.

ここで、液相イオン交換法とは、Ｃｕイオンを含む溶液にＡｌ同型置換シリケートに分散することによって、イオン交換する方法であり、固相イオン交換法とは、Ａｌ同型置換シリケートにＣｕの塩または酸化物を混合し、還元雰囲気あるいは不活性雰囲気で熱処理することによって、イオン交換する方法である。   Here, the liquid phase ion exchange method is a method of performing ion exchange by dispersing in a solution containing Cu ions in an Al isomorphous substituted silicate, and the solid phase ion exchange method is a salt of Cu in the Al isomorphous substituted silicate. Alternatively, an ion exchange is performed by mixing oxides and performing heat treatment in a reducing atmosphere or an inert atmosphere.

Ｃｕイオン交換方法によるＣｕ導入量は、Ａｌ同型置換シリケートの質量に対し、０．４〜０．６ｍａｓｓ％が好適である。   The amount of Cu introduced by the Cu ion exchange method is preferably 0.4 to 0.6 mass% with respect to the mass of the Al isomorphous substituted silicate.

Ｃｕイオン交換に用いる銅塩としては、例えば酢酸銅、塩化銅、硫酸銅などの各種銅塩を用いることができる。液相イオン交換時の溶液濃度は、０．００５〜０．０５ｍｏｌ／Ｌが好適である。この溶液中で室温〜１００℃の範囲で１２〜３６時間処理することによって、Ｃｕイオン交換を行う。この処理は、複数回行うことにより多くのＣｕを導入することができる。   As a copper salt used for Cu ion exchange, for example, various copper salts such as copper acetate, copper chloride, and copper sulfate can be used. The solution concentration during the liquid phase ion exchange is preferably 0.005 to 0.05 mol / L. Cu ion exchange is performed by treating in this solution for 12 to 36 hours at room temperature to 100 ° C. By performing this treatment a plurality of times, a large amount of Cu can be introduced.

イオン交換処理後、蒸留水を用いて濾過・洗浄し、室温〜１２０℃の範囲の温度で乾燥させた後、空気気流下５２０℃で１時間焼成し、本発明の尿素ＳＣＲ触媒を得る。なお焼成温度は、５００℃以上で、焼成時間は１時間以上であればよい。   After the ion exchange treatment, it is filtered and washed with distilled water, dried at a temperature ranging from room temperature to 120 ° C., and then calcined at 520 ° C. for 1 hour in an air stream to obtain the urea SCR catalyst of the present invention. The firing temperature may be 500 ° C. or higher and the firing time may be 1 hour or longer.

次に、この本発明のＡｌ同型置換鉄シリケートにＣｕイオンを導入した尿素ＳＣＲ触媒と、図４（ｃ）に示した先願のＡｌ同型置換鉄シリケートと、図３（ｂ）に示した従来触媒のＮＯｘ浄化性能とＮＯｘ吸着性能を試験した結果を図２に示す。   Next, the urea SCR catalyst in which Cu ions are introduced into the Al isomorphous substituted iron silicate of the present invention, the Al isomorphous substituted iron silicate of the prior application shown in FIG. 4 (c), and the prior art shown in FIG. 3 (b). FIG. 2 shows the results of testing the NOx purification performance and NOx adsorption performance of the catalyst.

図２において、横軸は排ガスの温度、縦軸はＮＯｘの浄化率を示し、また排ガス温度５０〜１２０℃の範囲でのＮＯｘ吸着率も同時に示している。   In FIG. 2, the horizontal axis represents the exhaust gas temperature, the vertical axis represents the NOx purification rate, and the NOx adsorption rate in the exhaust gas temperature range of 50 to 120 ° C. is also shown.

図２において、実線ａは本発明の尿素ＳＣＲ触媒、二点鎖線ｂは先願のＡｌ同型置換鉄シリケート、点線ｃは従来の尿素ＳＣＲ触媒（アルミノシリケート）のＮＯｘ浄化率とＮＯｘ吸着率をそれぞれ示したものである。   In FIG. 2, the solid line a represents the urea SCR catalyst of the present invention, the two-dot chain line b represents the Al isomorphous substituted iron silicate of the prior application, and the dotted line c represents the NOx purification rate and NOx adsorption rate of the conventional urea SCR catalyst (aluminosilicate), respectively. It is shown.

この図２より、従来の触媒に対して、本発明の尿素ＳＣＲ触媒および先願のＡｌ同型置換鉄シリケートは、ＮＯｘ吸着率については同等であるが、ＮＯｘ浄化率については、従来の触媒より格段に上昇していることがわかる。   From FIG. 2, the urea SCR catalyst of the present invention and the Al isomorphous substituted iron silicate of the prior application are equivalent to the conventional catalyst in terms of NOx adsorption rate, but the NOx purification rate is much higher than that of the conventional catalyst. You can see that it is rising.

特に、本発明の尿素ＳＣＲ触媒は、先願のＡｌ同型置換鉄シリケートに対してＮＯｘ浄化率が全体に高く、特に１００〜２００℃で触媒活性が高いことがわかる。   In particular, it can be seen that the urea SCR catalyst of the present invention generally has a high NOx purification rate compared with the Al isomorphous substituted iron silicate of the prior application, and particularly high catalytic activity at 100 to 200 ° C.

このように、本発明は、先願のＡｌ同型置換鉄シリケートにＣｕイオンを導入することによって、高いＮＯｘ浄化活性ならびに水熱耐久性を付与した触媒とすることができると共に、従来ＳＣＲ触媒と同等のＮＯｘ吸着特性を有し、かつ先願のＡｌ同型置換鉄シリケートよりもＮＯｘ浄化活性が向上し、しかも耐久性に優れた触媒とすることができる。   As described above, the present invention can provide a catalyst having high NOx purification activity and hydrothermal durability by introducing Cu ions into the Al isomorphous substituted iron silicate of the prior application, and is equivalent to the conventional SCR catalyst. Thus, the NOx purification activity is improved as compared with the Al isomorphous substituted iron silicate of the prior application, and the catalyst is excellent in durability.

１０ 排ガス管
１３ ＳＣＲ反応器
１４ 尿素水 10 exhaust gas pipe 13 SCR reactor 14 urea water

Claims (4)

排ガス中のＮＯｘをアンモニアで還元するための尿素ＳＣＲ触媒において、鉄シリケート骨格内にＡｌイオンを導入したＡｌ同型置換鉄シリケートに、Ｃｕイオンを導入したことを特徴とする尿素ＳＣＲ触媒。   A urea SCR catalyst for reducing NOx in exhaust gas with ammonia, wherein Cu ions are introduced into an Al isomorphous substituted iron silicate in which Al ions are introduced into an iron silicate skeleton. Ａｌ同型置換鉄シリケートに導入するＣｕ導入量は、Ａｌ同型置換鉄シリケートに対し０．４〜６．０ｍａｓｓ％とした請求項１記載の尿素ＳＣＲ触媒。   The urea SCR catalyst according to claim 1, wherein the amount of Cu introduced into the Al isomorphous substituted iron silicate is 0.4 to 6.0 mass% with respect to the Al isomorphous substituted iron silicate. 鉄シリケートベータゼオライトと硝酸アルミニウムと蒸留水を混ぜ、これを還流してＡｌ同型置換鉄シリケートとし、Ａｌ同型置換鉄シリケートにイオン交換によってＣｕイオンを導入し、これを５００℃以上で焼成した請求項１記載の尿素ＳＣＲ触媒。   Claims: A mixture of iron silicate beta zeolite, aluminum nitrate and distilled water, refluxed to obtain an Al isomorphous substituted iron silicate, Cu ions introduced into the Al isomorphous substituted iron silicate by ion exchange, and calcined at 500 ° C or higher. The urea SCR catalyst according to 1. ディーゼルエンジンの排ガス管にＳＣＲ反応器を接続し、そのＳＣＲ反応器の上流側で尿素水を噴射して排ガス中のＮＯｘを除去する排ガスの後処理システムにおいて、ＳＣＲ反応器の触媒に、鉄シリケート骨格内にＡｌイオンを導入したＡｌ同型置換鉄シリケートに、Ｃｕイオンを導入した尿素ＳＣＲ触媒を用いることを特徴とする排ガスの後処理システム。   In an exhaust gas aftertreatment system that connects an SCR reactor to the exhaust gas pipe of a diesel engine and injects urea water upstream of the SCR reactor to remove NOx in the exhaust gas, an iron silicate is used as the catalyst of the SCR reactor. An exhaust gas aftertreatment system, wherein a urea SCR catalyst into which Cu ions are introduced is used for Al isomorphous substituted iron silicate in which Al ions are introduced into the skeleton.
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JPH10137597A (en) * 1996-11-12 1998-05-26 Mitsubishi Heavy Ind Ltd Catalyst for purifying nitrogen oxide
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