JPH10249205A - Manufacture of catalyst for exhaust gas purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the chemical combination of an NOX absorbent material with alumina and prevent carbonate from becoming decomposed in a manufacturing step and further, improve the NOX absorbing power of a catalyst in a lean atmosphere by manufacturing the catalyst in a carbonic acid gas atmosphere through an entire baking process after the carrying of the NOX absorbent material. SOLUTION: A slurry solution prepared by loading alumina sol obtained by mixing 10g of boehmite alumina with 900g of 1% aqueous nitric acid solution and stirring the mixture, and activated γ alumina powder into a magnetic ball mill and crushing these materials, is made to stick to cordierite formation monolithic carrier. Further, this carrier is baked to obtain a carrier with a coated layer weighing 100g/L. In addition, this carrier material is impregnated with a mixed aqueous solution of rhodium nitrate and dinitrodiamine platinum, and then is baked after drying. Next, the carrier material is impregnated with an aqueous iron nitrate solution and is likewise baked after drying. After that, the carrier material is impregnated with an aqueous lanthanum nitrate solution, then is baked in an air current containing 10% CO2 after drying to obtain a desired catalyst for exhaust gas purification.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、ガソリン及びディ
ーゼル自動車、ボイラー等の内燃機関から排出される排
気ガス中の炭化水素（ＨＣ）、一酸化炭素（ＣＯ）およ
び窒素酸化物（ＮＯｘ）を浄化する排気ガス浄化用触媒
の製造方法に関し、特に酸素過剰雰囲気下でのＮＯｘの
浄化性能に優れる排気ガス浄化用触媒およびその製造方
法に関する。The present invention relates to the purification of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) in exhaust gas discharged from internal combustion engines such as gasoline and diesel vehicles and boilers. The present invention relates to a method for producing an exhaust gas purifying catalyst, and more particularly to an exhaust gas purifying catalyst excellent in NOx purification performance in an oxygen-excess atmosphere and a method for producing the same.

【０００２】[0002]

【従来の技術】近年、石油資源の枯渇問題および地球温
暖化の観点から、低燃費自動車の実現が期待されてお
り、特にガソリン自動車に関しては希薄燃焼自動車の開
発が望まれている。希薄燃焼自動車においては、希薄燃
焼走行時の排気ガス雰囲気は、理論空燃状態（以下、
「ストイキ状態」と称す）に比べて酸素過剰雰囲気（以
下、「リーン状態」と称す）となる。リーン雰囲気にお
いて、従来の三元触媒を適応させた場合には、過剰な酸
素の影響からＮＯｘ浄化作用が不十分になる問題があっ
た。このため酸素過剰雰囲気下においてもＮＯｘを浄化
できる触媒の開発が望まれていた。2. Description of the Related Art In recent years, from the viewpoint of depletion of petroleum resources and global warming, realization of fuel-efficient vehicles is expected, and development of lean-burn vehicles is particularly desired for gasoline vehicles. In lean-burn vehicles, the exhaust gas atmosphere during lean-burn operation is based on the theoretical air-fuel condition
The atmosphere becomes an oxygen-excess atmosphere (hereinafter, referred to as a "lean state") as compared with the "stoichiometric state". When a conventional three-way catalyst is applied in a lean atmosphere, there has been a problem that the effect of excessive oxygen makes the NOx purification action insufficient. Therefore, development of a catalyst that can purify NOx even in an oxygen-excess atmosphere has been desired.

【０００３】従来より、リーン雰囲気下におけるＮＯｘ
浄化性能を向上させる触媒は種々提案されており、大別
して二種類ある。一つは排気ガス中のＨＣを還元剤とし
てＮＯｘを還元浄化するものであり、もう一つはリーン
雰囲気下でＮＯｘを吸収し、ストイキ状態あるいは燃料
過剰（リッチ）雰囲気下でＮＯｘを浄化するものであ
る。Conventionally, NOx in a lean atmosphere has been
Various catalysts for improving the purification performance have been proposed, and are roughly classified into two types. One is for reducing and purifying NOx by using HC in exhaust gas as a reducing agent, and the other is for absorbing NOx in a lean atmosphere and purifying NOx in a stoichiometric or fuel-rich (rich) atmosphere. It is.

【０００４】前者の代表的なものとしては、例えば特開
昭６３−１００９１９号公報に、銅（Ｃｕ）をゼオライ
トに担持した触媒が開示されている。一方、後者の代表
的なものとしては、例えば特開平５−１６８８６０号公
報に、ランタン等を白金（Ｐｔ）に担持させてランタン
をＮＯｘ吸収材として用いる触媒が開示されている。As a representative of the former, for example, JP-A-63-100919 discloses a catalyst in which copper (Cu) is supported on zeolite. On the other hand, as a representative of the latter, for example, JP-A-5-168860 discloses a catalyst in which lanthanum is supported on platinum (Pt) and lanthanum is used as a NOx absorbent.

【０００５】しかし、上記特開平５−１６８８６０号公
報に開示された触媒は、ＮＯｘ吸収能力が不十分である
という問題があり、かかる問題を解決する目的で、例え
ば特開平５−２６１２８７号公報、特開平５−３１７６
５２号公報および特開平６−３１１３９号公報にアルカ
リ、アルカリ土類金属を用いる排気ガス浄化用触媒が開
示されている。また、特開平６−１４２４５８号公報お
よび特開平６−２６２０４０号公報には、アルカリ金
属、アルカリ土類金属、希土類金属、鉄金属を含有する
排気ガス浄化用触媒が開示されている。[0005] However, the catalyst disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-168860 has a problem that the NOx absorption capacity is insufficient, and for the purpose of solving such a problem, for example, Japanese Patent Application Laid-Open No. 5-261287, JP-A-5-3176
No. 52 and JP-A-6-31139 disclose exhaust gas purifying catalysts using alkali and alkaline earth metals. JP-A-6-142458 and JP-A-6-262040 disclose exhaust gas purifying catalysts containing alkali metals, alkaline earth metals, rare earth metals, and iron metals.

【０００６】さらに、特開平７−１７１３９９号公報で
は、多孔質単体にＢａ等ＮＯｘ吸収材を担持した担体に
対して、炭酸処理を行いＮＯｘ吸収材を炭酸塩化した
後、貴金属触媒を担持する工程を順に行うことで、貴金
属触媒担持工程におけるＮＯｘ吸収材の溶出と、貴金属
の析出・沈澱を防止し、ＮＯｘ吸収成分と貴金属触媒の
担持量を増大させ、ＮＯｘ吸収能力を向上させる方法が
開示されている。Further, Japanese Patent Application Laid-Open No. 7-171399 discloses a process of carrying out a carbonation treatment on a carrier in which a NOx absorbent such as Ba is carried on a single porous body and carbonating the NOx absorbent, followed by carrying a noble metal catalyst. Are sequentially performed to prevent the elution of the NOx absorbent in the noble metal catalyst supporting step and the precipitation and precipitation of the noble metal, increase the amount of the NOx absorbing component and the noble metal catalyst carried, and improve the NOx absorbing ability. ing.

【０００７】このＮＯｘ吸収反応の主経路を、典型的な
ＮＯｘ吸収材であるＢａの場合について示すと、 ＢａＣＯ₃ ＋２ＮＯ₂ ＋１／２・Ｏ₂ →Ｂａ（ＮＯ₃ ）₂ ＋ＣＯ₂ ・・・式１（ＮＯｘ吸収反応の主経路） であることが報告されており（触媒 Ｖｏｌ．３８（１
９９６）Ｐ４５０〜４５３）、ＢａＣＯ₃ 等の炭酸塩は
ＮＯｘ吸収反応にとって重要な化学形態であるといえ
る。また、ＢａＣＯ₃ の熱安定性は、分解温度が１３６
０℃と高いことが知られている。The main route of this NOx absorption reaction is shown in the case of Ba, which is a typical NOx absorbent, as follows: BaCO ₃ + 2NO ₂ + 1/2 · O ₂ → Ba (NO ₃ ) ₂ + CO _2. 1 (the main route of NOx absorption reaction) (Catalyst Vol. 38 (1)
996) Carbonates such as P450-453) and BaCO ₃ can be said to be important chemical forms for the NOx absorption reaction. The thermal stability of BaCO ₃ is such that the decomposition temperature is 136.
It is known that the temperature is as high as 0 ° C.

【０００８】[0008]

【発明が解決しようとする課題】ところが、これらＢａ
等ＮＯｘ吸収材を、多孔質担体に担持後、炭酸処理によ
り熱安定性の高い炭酸塩としても（図２）、さらに貴金
属触媒を担持し、貴金属触媒を固定化するために焼成す
ると、アルミナとＮＯｘ吸収材が化合し、吸収反応に重
要な炭酸塩が分解、減少することが判明した（図３）。
さらにアルミナと化合したＮＯｘ吸収材を、室温から炭
酸塩が分解した温度付近でＣＯ₂ に曝しても、炭酸塩は
再生せず（図４）、式１に示すＮＯｘ吸収反応の主経路
が半減もしくは失われるために、吸収量低下が起きるこ
とがわかった。However, these Ba
After the NOx absorbent is loaded on the porous carrier, it is converted into a carbonate having high thermal stability by carbonation treatment (FIG. 2). Further, when a noble metal catalyst is loaded and calcined to fix the noble metal catalyst, alumina It was found that the NOx absorbent was combined to decompose and reduce the carbonates important for the absorption reaction (FIG. 3).
Further, even when the NOx absorbent combined with alumina is exposed to CO ₂ from room temperature to a temperature near the decomposition of the carbonate, the carbonate is not regenerated (FIG. 4), and the main route of the NOx absorption reaction shown in Equation 1 is reduced by half. Or, it was found that absorption was reduced due to loss.

【０００９】[0009]

【課題を解決するための手段】本発明者らは、上記課題
を解決するために研究した結果、ＮＯｘ吸収材担持後の
全ての焼成工程を炭酸ガス雰囲気下で行うことで、ＮＯ
ｘ吸収材とアルミナとの化合を抑制し、製造工程におけ
る炭酸塩の分解を防ぎ（図１）、リーン雰囲気でのＮＯ
ｘ吸収能を向上させることを見いだし、本発明に到達し
た。Means for Solving the Problems As a result of research conducted to solve the above problems, the present inventors have found that all the sintering steps after carrying the NOx absorbent are carried out in a carbon dioxide gas atmosphere.
x suppresses the combination of the absorber and alumina, prevents the decomposition of carbonate in the manufacturing process (FIG. 1), and reduces NO in a lean atmosphere.
The inventors have found that the x-absorbing ability is improved, and have reached the present invention.

【００１０】多孔質担体への、ＮＯｘ吸収材の担持−焼
成工程と、貴金属の担持−焼成工程と、遷移金属の担持
−焼成工程とは、ＮＯｘ吸収材担持後に行われる全ての
焼成を炭酸ガス雰囲気下で行う場合、いかなる順序で行
われてもよい。The steps of carrying and firing the NOx absorbent, the step of supporting and firing the noble metal, and the step of supporting and firing the transition metal on the porous carrier are all carried out after the NOx absorbent is loaded by using carbon dioxide gas. When performed in an atmosphere, they may be performed in any order.

【００１１】炭酸ガス雰囲気焼成時の濃度は、ＣＯ₂ 濃
度５％以上であることが好ましい。ＣＯ₂ 濃度５％以下
では、炭酸塩の分解抑制効果が十分得られず、５％以上
であればその効果を得られる。The concentration during firing in a carbon dioxide gas atmosphere is preferably a CO ₂ concentration of 5% or more. When the CO ₂ concentration is 5% or less, the effect of suppressing the decomposition of carbonate cannot be sufficiently obtained, and when the CO ₂ concentration is 5% or more, the effect can be obtained.

【００１２】炭酸ガス雰囲気焼成時の燃焼温度は３００
〜７００℃であることが好ましい。７００℃以上では、
いかなる濃度の炭酸ガス雰囲気下でも、炭酸塩の分解を
防ぐことはできず、一方、３００℃以下では、炭酸塩の
分解が起こらない反面、焼成による担持成分の固定化を
十分行うことができず、耐久後に貴金属、遷移金属の凝
集、または、貴金属、遷移金属と基材、ＮＯｘ吸収材と
の化合が生じ、次式２に示す貴金属、遷移金属の働きが
低下し、前述式１のＮＯｘ吸収反応の低下を招く。 ＮＯ₂ ＋１／２・Ｏ₂ →ＮＯ₃ ・・・式２（貴金属の働き）The combustion temperature during firing in a carbon dioxide atmosphere is 300
It is preferable that it is -700 degreeC. Above 700 ° C
Under an atmosphere of carbon dioxide of any concentration, decomposition of carbonate cannot be prevented. On the other hand, at a temperature of 300 ° C. or lower, decomposition of carbonate does not occur. After the endurance, agglomeration of a noble metal or a transition metal, or a combination of a noble metal or a transition metal with a base material or a NOx absorbent occurs, and the functions of the noble metal and the transition metal represented by the following formula 2 decrease, and NOx absorption of the above formula 1 This leads to a decrease in the reaction. NO ₂ + 1/2 · O ₂ → NO ₃ ··· Formula 2 (function of precious metal)

【００１３】本発明の排気ガス浄化用触媒に用いるＮＯ
ｘ吸収材としては、アルカリ金属、アルカリ土類金属、
および、希土類金属から選ばれる金属の化合物を用いる
ことができる。アルカリ金属としてはＫ、アルカリ土類
金属としてはＢａまたはＳｒ、希土類金属としてはＬａ
をそれぞれ用いることが好ましい。NO used in the exhaust gas purifying catalyst of the present invention
x absorbers include alkali metals, alkaline earth metals,
Further, a compound of a metal selected from rare earth metals can be used. K as an alkali metal, Ba or Sr as an alkaline earth metal, La as a rare earth metal
Is preferably used.

【００１４】本発明の排気ガス浄化用触媒に用いる貴金
属としては、白金、パラジウム、および、ロジウムから
成る群より選ばれる少なくとも一種が用いられる。As the noble metal used in the exhaust gas purifying catalyst of the present invention, at least one selected from the group consisting of platinum, palladium and rhodium is used.

【００１５】前記貴金属の一部または全部を担持するた
めの基材としては、貴金属の分散性、特に耐久後の貴金
属の分散性を確保するため、比表面積の大きい耐熱性無
機材料が適し、特に活性アルミナが好ましい。耐熱比表
面積を高めるために希土類元素やジルコニア等を添加し
た活性アルミナを用いても良い。As a substrate for supporting a part or all of the noble metal, a heat-resistant inorganic material having a large specific surface area is suitable in order to secure the dispersibility of the noble metal, particularly, the noble metal after durability. Activated alumina is preferred. Activated alumina to which a rare earth element, zirconia, or the like is added to increase the heat resistant specific surface area may be used.

【００１６】本発明の排気ガス浄化用触媒に用いる遷移
金属は、鉄、コバルト、ニッケル、および、マンガンか
ら成る群より選ばれる少なくとも一種が用いられる。As the transition metal used in the exhaust gas purifying catalyst of the present invention, at least one selected from the group consisting of iron, cobalt, nickel and manganese is used.

【００１７】[0017]

【発明の実施の形態】以下、本発明による排気ガス浄化
用触媒の製造方法の実施例を、比較例及び実験例を参照
しながら具体的に説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method for producing an exhaust gas purifying catalyst according to the present invention will be specifically described with reference to comparative examples and experimental examples.

【００１８】（実施例１）１％硝酸水溶液９００ｇにベ
ーマイトアルミナ１０ｇを混合攪拌して得られたアルミ
ナゾルと、活性γアルミナ粉末を磁性ボールミルに投入
し、粉砕してアルミナスラリーを得た。このスラリー液
をコーディエライト質モノリス担体（１Ｌ，４００セ
ル）に付着させ、４００℃で１時間焼成してコート層重
量１００ｇ／Ｌ担体を得た。Example 1 An alumina sol obtained by mixing and stirring 10 g of boehmite alumina in 900 g of a 1% aqueous nitric acid solution and activated γ-alumina powder were charged into a magnetic ball mill and pulverized to obtain an alumina slurry. This slurry liquid was adhered to a cordierite-based monolith carrier (1 L, 400 cells) and calcined at 400 ° C. for 1 hour to obtain a coat layer weight of 100 g / L carrier.

【００１９】貴金属担持、第１の工程である焼成工程
（工程Ａ）；当該コート層重量１００ｇ／Ｌ担体材料
に、硝酸ロジウム、ジニトロジアミン白金の混合水溶液
を含浸し、乾燥した後、空気中で４００℃、１時間の焼
成を行った。当該材料中のロジウムおよび白金の含有量
は、各々０．２４ｇ／Ｌ、１．１８ｇ／Ｌであった。Noble metal loading, first baking step (step A): 100 g / L of the coating layer is impregnated with a mixed aqueous solution of rhodium nitrate and dinitrodiamine platinum, dried, and dried in air. The firing was performed at 400 ° C. for one hour. The contents of rhodium and platinum in the material were 0.24 g / L and 1.18 g / L, respectively.

【００２０】遷移金属担持、第２の工程である焼成工程
（工程Ｂ）；工程Ａで得た担体材料に、硝酸鉄水溶液を
含浸し、乾燥した後、空気中で４００℃、１時間の焼成
を行った。当該材料中の鉄の含有量は、金属モルに換算
して０．１モル／Ｌであった。Transition metal loading, second step, firing step (step B); impregnating the carrier material obtained in step A with an aqueous solution of iron nitrate, drying, and then firing in air at 400 ° C. for 1 hour. Was done. The iron content in the material was 0.1 mol / L in terms of mole of metal.

【００２１】ＮＯｘ吸収材担持、第３の工程である焼成
工程（工程Ｃ）；工程Ａおよび工程Ｂで得た担体材料
に、硝酸ランタン水溶液を含浸し、乾燥した後、１０％
ＣＯ₂含有空気気流中で４００℃、１時間の焼成を行っ
た。当該材料中のランタンの含有量は、金属モルに換算
して０．１モル／Ｌであった。さらに、硝酸バリウムと
酢酸カリウムの混合水溶液を含浸し、乾燥した後、１０
％ＣＯ₂ 含有空気気流中で４００℃、１時間の焼成を行
った。当該材料中のバリウム、カリウムの含有量は、各
々金属モルに換算して０．１モル／Ｌ、０．１モル／Ｌ
であった。The NOx absorbent loading, the third step, a firing step (step C); the carrier material obtained in step A and step B is impregnated with an aqueous lanthanum nitrate solution, dried and then 10%
The calcination was performed at 400 ° C. for 1 hour in an air stream containing CO ₂ . The content of lanthanum in the material was 0.1 mol / L in terms of mole of metal. Furthermore, after impregnating with a mixed aqueous solution of barium nitrate and potassium acetate and drying,
The calcination was performed at 400 ° C. for 1 hour in an air stream containing% CO ₂ . The contents of barium and potassium in the material are respectively 0.1 mol / L and 0.1 mol / L in terms of metal mol.
Met.

【００２２】（実施例２）工程Ｂ、工程Ａ、工程Ｃの順
に行うこと以外は、実施例１と同様にして排気ガス浄化
用触媒を得た。Example 2 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that Step B, Step A and Step C were performed in this order.

【００２３】（実施例３）工程Ａ、工程Ｃ、工程Ｂの順
に行い、工程Ｂの焼成を１０％ＣＯ₂ 含有空気気流中で
行うこと以外は、実施例１と同様にして排気ガス浄化用
触媒を得た。(Example 3) A process for purifying exhaust gas was carried out in the same manner as in Example 1 except that Step A, Step C, and Step B were performed in this order, and that the calcination in Step B was performed in an air stream containing 10% CO ₂ . A catalyst was obtained.

【００２４】（実施例４）工程Ｂ、工程Ｃ、工程Ａの順
に行い、工程Ａの焼成を１０％ＣＯ₂ 含有空気気流中で
行うこと以外は、実施例１と同様にして排気ガス浄化用
触媒を得た。Example 4 Exhaust gas purification was performed in the same manner as in Example 1 except that Step B, Step C, and Step A were performed in this order, and that the calcination in Step A was performed in an air stream containing 10% CO ₂ . A catalyst was obtained.

【００２５】（実施例５）工程Ｃ、工程Ａ、工程Ｂの順
に行い、工程Ａ，Ｂの焼成を１０％ＣＯ₂ 含有空気気流
中で行うこと以外は、実施例１と同様にして排気ガス浄
化用触媒を得た。Example 5 Exhaust gas was produced in the same manner as in Example 1 except that Step C, Step A, and Step B were performed in this order, and that Steps A and B were performed in an air stream containing 10% CO _2. A purification catalyst was obtained.

【００２６】（実施例６）工程Ｃ、工程Ｂ、工程Ａの順
に行い、工程Ａ，Ｂの焼成を１０％ＣＯ₂ 含有空気気流
中で行うこと以外は、実施例１と同様にして排気ガス浄
化用触媒を得た。(Example 6) Exhaust gas was produced in the same manner as in Example 1 except that the steps C, B, and A were performed in this order, and the calcination of the steps A and B was performed in an air stream containing 10% CO _2. A purification catalyst was obtained.

【００２７】（実施例７）工程Ｃにおいて、焼成を５０
％ＣＯ₂ 含有空気気流中で行うこと以外は、実施例１と
同様にして排気ガス浄化用触媒を得た。(Embodiment 7) In step C, the firing was
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that the reaction was performed in an air stream containing% CO ₂ .

【００２８】（実施例８）工程Ａにおいて、硝酸ロジウ
ム、ジニトロジアミン白金の混合水溶液のかわりに硝酸
パラジウム水溶液を用いること以外は、実施例１と同様
にして排気ガス浄化用触媒を得た。当該材料中のパラジ
ウムの含有量は、２．８３ｇ／Ｌであった。Example 8 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that in step A, an aqueous solution of palladium nitrate was used instead of the mixed aqueous solution of rhodium nitrate and dinitrodiamine platinum. The content of palladium in the material was 2.83 g / L.

【００２９】（実施例９）工程Ｂにおいて、硝酸鉄水溶
液のかわりに硝酸コバルト水溶液を用いること以外は、
実施例１と同様にして排気ガス浄化用触媒を得た。当該
材料中のコバルトの含有量は、金属モルに換算して、
０．１モル／Ｌであった。(Example 9) In step B, an aqueous cobalt nitrate solution was used instead of the aqueous iron nitrate solution.
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1. The content of cobalt in the material is converted into moles of metal,
It was 0.1 mol / L.

【００３０】（実施例１０）工程Ｂにおいて、硝酸鉄水
溶液のかわりに硝酸マンガン水溶液を用いること以外
は、実施例１と同様にして排気ガス浄化用触媒を得た。
当該材料中のマンガンの含有量は、金属モルに換算し
て、０．１モル／Ｌであった。Example 10 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that in step B, a manganese nitrate aqueous solution was used instead of the iron nitrate aqueous solution.
The content of manganese in the material was 0.1 mol / L in terms of mole of metal.

【００３１】（実施例１１）工程Ｂにおいて、硝酸鉄水
溶液のかわりに硝酸ニッケル水溶液を用いること以外
は、実施例１と同様にして排気ガス浄化用触媒を得た。
当該材料中のニッケルの含有量は、金属モルに換算し
て、０．１モル／Ｌであった。Example 11 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that in step B, an aqueous solution of nickel nitrate was used instead of the aqueous solution of iron nitrate.
The nickel content in the material was 0.1 mol / L in terms of mole of metal.

【００３２】（実施例１２）工程Ｃにおいて、硝酸バリ
ウムを用いないこと以外は、実施例１と同様にして排気
ガス浄化用触媒を得た。Example 12 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that barium nitrate was not used in Step C.

【００３３】（実施例１３）工程Ｃにおいて、硝酸カリ
ウムを用いないこと以外は、実施例１と同様にして排気
ガス浄化用触媒を得た。Example 13 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that potassium nitrate was not used in Step C.

【００３４】（実施例１４）工程Ｃにおいて、硝酸ラン
タンを用いないこと以外は、実施例１と同様にして排気
ガス浄化用触媒を得た。Example 14 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that lanthanum nitrate was not used in Step C.

【００３５】（比較例１）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例１と同様にして排気ガス浄化用触媒を得た。(Comparative Example 1) 10% in all firings
Without using the CO ₂ containing air, except that carried in the air fired to obtain the exhaust gas purifying catalyst in the same manner as in Example 1.

【００３６】（比較例２）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例２と同様にして排気ガス浄化用触媒を得た。(Comparative Example 2) 10%
Without using the CO ₂ containing air, except that carried in the air fired to obtain the exhaust gas purifying catalyst in the same manner as in Example 2.

【００３７】（比較例３）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例３と同様にして排気ガス浄化用触媒を得た。(Comparative Example 3) 10% in all firings
An exhaust gas purifying catalyst was obtained in the same manner as in Example 3, except that calcination was performed in air without using CO ₂ -containing air.

【００３８】（比較例４）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例４と同様にして排気ガス浄化用触媒を得た。(Comparative Example 4) 10% in all firings
Without using the CO ₂ containing air, except that carried in the air fired to obtain the exhaust gas purifying catalyst in the same manner as in Example 4.

【００３９】（比較例５）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例５と同様にして排気ガス浄化用触媒を得た。(Comparative Example 5) 10%
Without using the CO ₂ containing air, except that carried in the air fired to obtain the exhaust gas purifying catalyst in the same manner as in Example 5.

【００４０】（比較例６）全ての焼成において、１０％
ＣＯ₂ 含有空気を用いず、空気中焼成を行うこと以外
は、実施例６と同様にして排気ガス浄化用触媒を得た。(Comparative Example 6) 10% in all firings
Without using the CO ₂ containing air, except that carried in the air fired to obtain the exhaust gas purifying catalyst in the same manner as in Example 6.

【００４１】（比較例７）工程Ｃの１０％ＣＯ₂ 含有空
気中で行う焼成を、２５０℃で１時間行うこと以外は、
実施例１と同様にして排気ガス浄化用触媒を得た。(Comparative Example 7) Except that the firing in Step C in air containing 10% CO ₂ was performed at 250 ° C for 1 hour,
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1.

【００４２】（比較例８）工程Ｃの１０％ＣＯ₂ 含有空
気中で行う焼成を、２５０℃で１時間行うこと以外は、
実施例２と同様にして排気ガス浄化用触媒を得た。(Comparative Example 8) Except that the firing in Step C in air containing 10% CO ₂ was performed at 250 ° C for 1 hour,
An exhaust gas purifying catalyst was obtained in the same manner as in Example 2.

【００４３】（比較例９）工程Ｃ，Ｂの１０％ＣＯ₂ 含
有空気中で行う焼成を、２５０℃で１時間行うこと以外
は、実施例３と同様にして排気ガス浄化用触媒を得た。(Comparative Example 9) An exhaust gas purifying catalyst was obtained in the same manner as in Example 3, except that the calcination in Steps C and B in air containing 10% CO ₂ was performed at 250 ° C for 1 hour. .

【００４４】（比較例１０）工程Ｃ，Ａの１０％ＣＯ₂
含有空気中で行う焼成を、２５０℃で１時間行うこと以
外は、実施例４と同様にして排気ガス浄化用触媒を得
た。Comparative Example 10 10% CO ₂ of Steps C and A
An exhaust gas purifying catalyst was obtained in the same manner as in Example 4, except that the calcination in the contained air was performed at 250 ° C. for 1 hour.

【００４５】（比較例１１）工程Ｃ，Ａ，Ｂの１０％Ｃ
Ｏ₂ 含有空気中で行う焼成を、２５０℃で１時間行うこ
と以外は、実施例５と同様にして排気ガス浄化用触媒を
得た。(Comparative Example 11) 10% C of steps C, A and B
An exhaust gas purifying catalyst was obtained in the same manner as in Example 5, except that the calcination in the O ₂ -containing air was performed at 250 ° C. for 1 hour.

【００４６】（比較例１２）工程Ｃ，Ａ，Ｂの１０％Ｃ
Ｏ₂ 含有空気中で行う焼成を、２５０℃で１時間行うこ
と以外は、実施例６と同様にして排気ガス浄化用触媒を
得た。(Comparative Example 12) 10% C of Steps C, A and B
An exhaust gas purifying catalyst was obtained in the same manner as in Example 6, except that the calcination in the O ₂ -containing air was performed at 250 ° C. for 1 hour.

【００４７】（比較例１３）工程Ｃの１０％ＣＯ₂ 含有
空気中で行う焼成を、７５０℃で１時間行うこと以外
は、実施例１と同様にして排気ガス浄化用触媒を得た。(Comparative Example 13) An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that the calcination in Step C in air containing 10% CO ₂ was performed at 750 ° C for 1 hour.

【００４８】（比較例１４）工程Ｃの１０％ＣＯ₂ 含有
空気中で行う焼成を、７５０℃で１時間行うこと以外
は、実施例２と同様にして排気ガス浄化用触媒を得た。(Comparative Example 14) An exhaust gas purifying catalyst was obtained in the same manner as in Example 2, except that the firing in Step C in air containing 10% CO ₂ was performed at 750 ° C for 1 hour.

【００４９】（比較例１５）工程Ｃ，Ｂの１０％ＣＯ₂
含有空気中で行う焼成を、７５０℃で１時間行うこと以
外は、実施例３と同様にして排気ガス浄化用触媒を得
た。Comparative Example 15 10% CO ₂ of Steps C and B
An exhaust gas purifying catalyst was obtained in the same manner as in Example 3, except that the calcination in the contained air was performed at 750 ° C. for 1 hour.

【００５０】（比較例１６）工程Ｃ，Ａの１０％ＣＯ₂
含有空気中で行う焼成を、７５０℃で１時間行うこと以
外は、実施例４と同様にして排気ガス浄化用触媒を得
た。Comparative Example 16 10% CO ₂ of Steps C and A
An exhaust gas purifying catalyst was obtained in the same manner as in Example 4, except that the calcination in the contained air was performed at 750 ° C. for 1 hour.

【００５１】（比較例１７）工程Ｃ，Ａ，Ｂの１０％Ｃ
Ｏ₂ 含有空気中で行う焼成を、７５０℃で１時間行うこ
と以外は、実施例５と同様にして排気ガス浄化用触媒を
得た。(Comparative Example 17) 10% C of Steps C, A and B
An exhaust gas purifying catalyst was obtained in the same manner as in Example 5, except that the firing in the O ₂ -containing air was performed at 750 ° C. for 1 hour.

【００５２】（比較例１８）工程Ｃ，Ａ，Ｂの１０％Ｃ
Ｏ₂ 含有空気中で行う焼成を、７５０℃で１時間行うこ
と以外は、実施例６と同様にして排気ガス浄化用触媒を
得た。(Comparative Example 18) 10% C of steps C, A and B
An exhaust gas purifying catalyst was obtained in the same manner as in Example 6, except that the calcination in the O ₂ -containing air was performed at 750 ° C. for 1 hour.

【００５３】（比較例１９）工程Ｃにおいて、焼成を
２．５％ＣＯ₂ 含有空気気流中で行うこと以外は、実施
例１と同様にして排気ガス浄化用触媒を得た。Comparative Example 19 An exhaust gas purifying catalyst was obtained in the same manner as in Example 1, except that in step C, the calcination was carried out in an air stream containing 2.5% CO ₂ .

【００５４】上記実施例１〜１４および比較例１〜１９
の触媒について、工程および触媒組成を、表１に示す。Examples 1 to 14 and Comparative Examples 1 to 19
Table 1 shows the process and catalyst composition for the catalyst (1).

【００５５】[0055]

【表１】 [Table 1]

【００５６】（実験例）上記実施例１〜１４および比較
例１〜１９の触媒について、以下の条件で初期及び耐久
後の触媒活性評価を行った。(Experimental Examples) The catalysts of Examples 1 to 14 and Comparative Examples 1 to 19 were evaluated for catalytic activity at the initial stage and after the endurance under the following conditions.

【００５７】＜耐久条件＞エンジン４４００ｃｃの排気
系に触媒を装着し、６００℃で、５０時間運転し、耐久
を行った。<Durability Conditions> A catalyst was mounted in an exhaust system of 4400 cc engine and operated at 600 ° C. for 50 hours to perform durability.

【００５８】＜評価条件＞触媒活性評価は、排気量２０
００ｃｃのエンジンの排気系に各種触媒を装着し、Ａ／
Ｆ＝１４．６（ストイキ状態）で３０秒間、その後Ａ／
Ｆ＝２２（リーン状態で３０秒間の１サイクルを行い、
各々平均転化率を測定し、このＡ／Ｆ＝１４．６の場合
の平均転化率とＡ／Ｆ＝２２の場合の平均転化率とを平
均してトータル転化率とした。この評価を、初期及び耐
久後に各々行った。平均転化率の算出法は以下の通りで
ある。<Evaluation Conditions> The catalyst activity was evaluated using a displacement of 20
Attaching various catalysts to the exhaust system of a 00cc engine, A /
F = 14.6 (stoichiometric state) for 30 seconds, then A /
F = 22 (1 cycle of 30 seconds in lean state,
The average conversion was measured, and the average conversion when A / F = 14.6 and the average conversion when A / F = 22 were averaged to obtain the total conversion. This evaluation was performed at the initial stage and after the endurance. The method of calculating the average conversion is as follows.

【００５９】[0059]

【数１】 (Equation 1)

【００６０】トータル転化率として得られた触媒活性評
価結果を表２に示す。比較例に比べ、実施例は、触媒活
性が高く、後述する本発明の効果を確認することができ
る。Table 2 shows the catalytic activity evaluation results obtained as the total conversion. As compared with the comparative example, the example has a higher catalytic activity, and can confirm the effects of the present invention described later.

【００６１】[0061]

【表２】 [Table 2]

【００６２】請求項記載の排気ガス浄化用触媒製造方法
で得られた触媒は、ＮＯｘ吸収材担持以降の全ての焼成
を、炭酸ガス雰囲気下で行うことにより、従来の触媒製
造法では十分活性が得られないリーン雰囲気におけるＮ
Ｏｘ浄化性能を、ＮＯｘ吸収に必要な、吸収材の炭酸化
合状態を維持することにより高めることができる。The catalyst obtained by the method for producing an exhaust gas purifying catalyst according to the present invention has sufficient activity in the conventional catalyst production method by performing all calcinations after loading the NOx absorbent in a carbon dioxide gas atmosphere. N in a lean atmosphere that cannot be obtained
Ox purification performance can be enhanced by maintaining the carbonation state of the absorbent necessary for NOx absorption.

【００６３】[0063]

【発明の効果】以上、詳細に説明してきたように、本発
明の排気ガス浄化用触媒の製造方法では、ＮＯｘ吸収材
担持後の全ての焼成工程を炭酸ガス雰囲気下で行うこと
で、基材中のアルミナとＮＯｘ吸収材の化合を防ぎ、Ｎ
Ｏｘ吸収反応に重要な炭酸塩を、吸収材担持後の焼成に
より失うことなく製品化することができる。こうして、
触媒中に保持された炭酸塩は、排気ガス雰囲気下におい
ても、排気ガス雰囲気中に含まれる１０〜１５％のＣＯ
₂ により、アルミナと化合することなく、式１に示した
ＮＯｘ吸収反応式に基づく反応を速やかに実現し、十分
なＮＯｘ吸収能を得ることができる。As described above in detail, in the method for manufacturing an exhaust gas purifying catalyst according to the present invention, all the sintering steps after carrying the NOx absorbent are carried out in a carbon dioxide gas atmosphere. Prevents the combination of alumina and NOx absorbent in the
Carbonates important for the Ox absorption reaction can be commercialized without being lost by firing after supporting the absorbent. Thus,
The carbonate retained in the catalyst is capable of removing 10 to 15% of CO contained in the exhaust gas atmosphere even under the exhaust gas atmosphere.
_{According to 2} , a reaction based on the NOx absorption reaction formula shown in Formula 1 can be quickly realized without combining with alumina, and a sufficient NOx absorption capacity can be obtained.

【図面の簡単な説明】[Brief description of the drawings]

【図１】Ｘ線回折ピークパターン（吸収材担持後全工程
炭酸ガス焼成）を示す図である。FIG. 1 is a view showing an X-ray diffraction peak pattern (all steps of carbon dioxide firing after supporting an absorber).

【図２】Ｘ線回折ピークパターン（炭酸ガス処理後）を
示す図である。FIG. 2 is a view showing an X-ray diffraction peak pattern (after carbon dioxide gas treatment).

【図３】Ｘ線回折ピークパターン（貴金属担持、焼成処
理後）を示す図である。FIG. 3 is a view showing an X-ray diffraction peak pattern (noble metal supported, after firing treatment).

【図４】Ｘ線回折ピークパターン（炭酸ガス再処理後）
を示す図である。FIG. 4 X-ray diffraction peak pattern (after reprocessing of carbon dioxide)
FIG.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 耐久性無機担体上に、貴金属触媒を担
持、焼成する第１の工程と、 遷移金属を担持、焼成する第２の工程と、 ＮＯｘ吸収材を担持、焼成する第３の工程と、から成る
排気ガス浄化用触媒の製造方法において、 第３の工程以降の全てに含まれる焼成工程を炭酸ガス雰
囲気下で行うことを特徴とする排気ガス浄化用触媒の製
造方法。1. A first step of supporting and firing a noble metal catalyst on a durable inorganic carrier, a second step of supporting and firing a transition metal, and a third step of supporting and firing a NOx absorbent. The method of manufacturing an exhaust gas purifying catalyst according to claim 1, wherein the firing step included in all of the third and subsequent steps is performed in a carbon dioxide gas atmosphere.