JP3884719B2 - Method for producing ceramic catalyst body - Google Patents

Description

【０１３１】
次に，試料１〜８，比較試料１，２のセラミック触媒体に対し実機エンジンからの排気ガスによる耐久試験を実施した。また，各試料の作成に用いた懸濁液の濃度は１０％とした。
耐久試験は，セラミック触媒体に実機エンジンを用いて９００℃で１０時間，排気ガスを導入して行った。そして，ＮＯｘ吸蔵量，セラミック触媒体の流路方向（図２に記載）の熱膨張係数をそれぞれ測定し，表２に記載した。
表２におけるＮＯｘ吸蔵量は，触媒安定層のないセラミック触媒体（耐久後）のＮＯｘ吸蔵量を１として，これに対する比で記載した。
また，熱膨張係数は押棒式熱膨張計法で，２５℃から８００℃の間の平均の熱膨張係数で評価した。
【０１３２】
表２から明らかなように，従来のプロペラ混合や媒体攪拌ミルで得た懸濁液より触媒安定層を形成した比較試料１では，熱膨張係数が１．７５×１０^-6／℃，比較試料２では，１．５６×１０^-6／℃と高かった。
比較試料１や２にかかるセラミック触媒体について，耐久試験後のセラミック担体をＥＰＭＡ（＝電子線マイクロアナライザー）で分析した結果，コーディエライト構造中にＮＯｘ吸蔵材に含まれるカリウムが移動，拡散していることが確認され，セラミック担体の組成が変化（副生成物を形成）して熱膨張係数が増加したことが確認された。
【０１３３】
これに対し，表２に示されるように，試料１〜８のセラミック触媒体は，いずれも流路方向の熱膨張係数が１．５×１０^-6／℃以下と実用上十分に低い。また，ＮＯｘ吸蔵量（耐久後）は，比較試料１及び２に比べ多くなっており，長期にわたり触媒性能が維持できることがわかった。
また，試料１〜８のセラミック触媒体の触媒成分，特にカリウム化合物の分散状態をＥＰＭＡで分析した結果，いずれの試料もカリウム化合物が触媒層中にほぼ均一に分散していることが確認された。これは試料１〜８のセラミック触媒体では，触媒安定層によりカリウムの移動，拡散が防止され，セラミック担体を構成するコーディエライトとカリウム化合物の反応が生じていないことを示している。
【０１３４】
【表２】

【０１３５】
（実施例５）
本例は，実施例１と同様のセラミック担体の表面にシリカよりなる中間層を，該中間層の表面にγ−アルミナのコート層と触媒成分，触媒トラップ材からなる触媒層を設けてなるセラミック触媒体について性能を評価した。
【０１３６】
上記触媒層はγ−アルミナからなるコート層に主触媒及び助触媒からなる触媒成分と上記触媒成分の拡散を防止する触媒トラップ材を担持して構成する。
主触媒は貴金属触媒で，助触媒はＮＯｘ吸蔵材である。具体的には，主触媒はＰｔとＲｈからなり，助触媒はカリウム化合物（Ｋ₂Ｏ）からなる。
触媒トラップ材は平均粒子径が１００〜３００ｎｍの超微粒子（シーアイ化成（株）製，ナノテック超微粒子）のＣｅＯ₂で，触媒層を構成するγ−Ａｌ₂Ｏ₃に対して重量で１０％（外％）を添加した。
【０１３７】
試料９〜１３は，実施例１に記載した高圧分散混合処理を利用して懸濁液を作製した。各試料において高圧分散混合処理に用いた装置は高圧ホモジナイザーで，圧力を少しずつ変えてある。
試料１４〜１６は，実施例２に記載した高速密閉攪拌処理を利用して懸濁液を作製した。各試料において回転羽根（実施例２参照）の周速を少しずつ変えてある。
また，比較試料３は，従来の分散方法であるスクリュー混合を，比較試料４は媒体撹拝ミルを利用して懸濁液を作製した。
なお，各懸濁液作製の詳細は実施例４と同様である。
【０１３８】
次に，試料９〜１６，比較試料３，４のセラミック触媒体に対し実機エンジンから排出される排気ガスを利用した耐久試験を実施例４と同様に行った。
その結果，表３から明らかなように，従来のプロペラ混合や媒体攪拌ミルで得た懸濁液より触媒層を形成した比較試料３では，熱膨張係数が１．８２×１０^-6／℃，比較試料４では，１．６５×１０^-6／℃と高かった。
【０１３９】
また，実施例４の比較試料１，２と同様に，コーディエライト構造中にＮＯｘ吸蔵材であるカリウムが移動，拡散していることが確認され，セラミック担体の組成が変化（副生成物を形成）し，熱膨張係数が増加したことが確認された。
【０１４０】
これに対し，試料９〜１６のセラミック触媒体は，いずれも流路方向の熱膨張係数が１．５×１０^-6／℃以下と実用上十分に低い。また，ＮＯｘ吸蔵量（耐久後）は，比較試料１及び２に比べ多くなっており，長期にわたり触媒性能が維持できることがわかった。
また，実施例４の試料１〜８と同様に，いずれの試料もカリウム化合物が触媒層中にほぼ均一に分散し，カリウムの移動，拡散が防止され，セラミック担体を構成するコーディエライトとカリウム化合物の反応が生じていなかった。
【０１４１】
【表３】

【０１４２】
（実施例６）
本例は，実施例１と同様のセラミック担体の表面にシリカよりなる中間層を，該中間層の表面にγ−アルミナのコート層と触媒成分，触媒活性材からなる触媒層を設けてなるセラミック触媒体について性能を評価した。
上記触媒層はγ−アルミナからなるコート層に主触媒及び助触媒からなる触媒成分と上記触媒成分の拡散を防止する触媒活性材を担持して構成する。
【０１４３】
主触媒は貴金属触媒で，助触媒はＮＯｘ吸蔵材である。具体的には，主触媒はＰｔとＲｈからなり，助触媒はカリウム化合物（Ｋ₂Ｏ）からなる。
触媒活性材は平均粒子径が１００〜３００ｎｍの超微粒子（シーアイ化成（株）製，ナノテック超微粒子）のＣｅＯ₂とＡｌ₂Ｏ₃とを１対１で混ぜたもので，触媒層を構成するγ−Ａｌ₂Ｏ₃に対して重量で１０％（外％）を添加した。
【０１４４】
試料１７〜２１は，実施例１に記載した高圧分散混合処理で懸濁液を作製した。各試料において高圧分散混合処理に用いた装置は高圧ホモジナイザーで，混合の圧力を少しずつ変えてある。
試料２２〜２４は，実施例２に記載した高速密閉攪拌処理で懸濁液を作製した。各試料において回転羽根（実施例２参照）の周速を少しずつ変えてある。
また，比較試料５は，従来の分散方法であるスクリュー混合を，比較試料６は媒体撹拝ミルを利用して懸濁液を作製した。
詳細は実施例４と同様である。
【０１４５】
次に，試料１７〜２４，比較試料５，６のセラミック触媒体に対し実機エンジンからの排気ガスによる耐久試験を実施例４と同様に行った。
その結果，表４から明らかなように，従来のプロペラ混合や媒体攪拌ミルで得た懸濁液より触媒層を形成した比較試料５では，熱膨張係数が１．８９×１０^-6／℃，比較試料６では，１．６２×１０^-6／℃と高かった。
また，実施例４の比較試料１，２と同様に，コーディエライト構造中にＮＯｘ吸蔵材であるカリウムが移動，拡散していることが確認され，セラミック担体の組成が変化（副生成物を形成）して熱膨張係数が増加したことが確認された。
【０１４６】
これに対し，試料１７〜２４のセラミック触媒体は，いずれも流路方向の熱膨張係数が１．５×１０^-6／℃以下と実用上十分に低い。また，ＮＯｘ吸蔵量（耐久後）は，比較試料１及び２に比べ多くなっており，長期にわたり触媒性能が維持できることがわかった。
また，いずれの試料もカリウム化合物が触媒層中にほぼ均一に分散し，カリウムの移動，拡散が防止され，セラミック担体を構成するコーディエライトとカリウム化合物の反応が生じていなかった。
【０１４７】
なお，実施例４〜６では，触媒成分の中でも特にカリウムの移動・拡散について調べたが，他のアルカリ金属，アルカリ土類金属系の化合物からなる触媒成分が触媒層に含まれていた場合も同様の結果を得た。
また，セラミック担体として，コーディエライト以外のＳｉＣ，Ｓｉ₃Ｎ₄，ムライトからなる材料で構成したハニカム構造体を用いた場合も同様の結果を得た。
【０１４８】
そして，表２〜表４に記載したように，プロペラ混合や媒体攪拌ミルを利用して触媒安定層や触媒層用の懸濁液を作製してセラミック触媒体を得た場合，該セラミック触媒体は，水蒸気存在下で６００℃程度からＮＯｘ吸蔵材等の触媒成分の拡散が始まってしまう。
このため自動車排気ガスにさらされるような最高温度が１０００℃程度まで上昇する使用環境では，触媒成分の拡散による触媒性能の低下，触媒成分とセラミック担体との反応が原因の担体劣化が発生する。
【０１４９】
これに対し，試料１〜２４にかかるセラミック触媒体は，懸濁液を高圧分散混合処理や高速密閉攪拌処理を利用して作製した懸濁液を利用する。
そのため，触媒安定層材料または触媒層材料を溶媒に均一分散混合して得た再凝集し難い懸濁液をセラミック担体に均一分散混合状態で付与することから形成した触媒安定層や触媒層は，どの部分においても均一な表面電位や均一な混合組成を備えており，高温，水分存在下（一般に排気ガスの水分率１０〜２０重量％である）で，触媒成分がセラミック担体へ拡散してセラミック担体劣化などの問題を生じ難い。
このように，各実施例に記載した試料１〜２４にかかるセラミック触媒体は，リーンバーンシステムやディーゼルエンジンの自動車排気ガス浄化用触媒として好適に用いることができる。
【０１５０】
さらに，各実施例に記載した試料１〜２４にかかるセラミック触媒体は，ガソリンエンジンの三元触媒に好適に用いることができる。
ガソリンエンジンの三元触媒は長期にわたり浄化性能を高活性で維持することが要求されるが，本例にかかるセラミック触媒体を利用することで，触媒層中の触媒活性材からＰｔ，Ｒｈ等の貴金属触媒に水素を供給することで（試料１７〜試料２４），活性面を増加させ，安定した触媒反応を長期に渡り維持できる。
【０１５１】
また，ディーゼルエンジンから排出されるすす等のＰＭ（パティキュレートマター：粒子状物質）を捕集し，貴金属触媒により燃焼・除去するセラミックフィルタでは，触媒成分が排気ガス中のイオウ等の触媒被毒物質の影響を受けて劣化する。
ここに試料１７〜２４を適用し，Ｐｔ，Ｒｈ等の貴金属触媒に水素を供給することで，触媒被毒物質の除去を促進することができる。よって，活性面に触媒被毒物質が残留・堆積することがないので，触媒反応を安定して維持できる。
【０１５２】
【表４】

【０１５３】
（比較例１）
比較のために，従来の分散方法であるプロペラ攪拌混合を利用して懸濁液を作成し，この懸濁液から触媒安定層，更触媒層を形成して実施例１と同様のＮＯｘ吸蔵還元型のセラミック触媒体を作成した。
本例では，懸濁液を調整するためにプロペラ攪拌混合装置（アスワン（株）ＳＭ−１０２）を用いる。このプロペラ攪拌混合装置による混合条件は回転数５００ｒｐｍで行う。なお，ここで使用する混合液は実施例１と同様に超微粒子ＣｅＯ₂とＹ₂Ｏ₃（シーアイ化成製）を純粋に均一混合させて調整した混合液を用いる。
【０１５４】
本例のプロペラ攪拌混合操作では，超微粒子ＣｅＯ₂とＹ₂Ｏ₃（シーアイ化成製）を純水に均一混合させて調整した懸濁液をビーカ（１リットル）に入れ，攪拌混合装置のシャフトの先端に攪拌羽根としてプロペラ羽根を取り付けたシャフトの先端を前記ビーカに入れて，プロペラ羽根を回転させて混合する。この際，ビーカの懸濁液が飛散しないように回転数を制御するが，最高回転数５００ｒｐｍが限界であった。
【０１５５】
（比較例２）
比較のために，従来の分散方法である媒体攪拌ミルを利用して懸濁液を作成し，この懸濁液から触媒安定層，更触媒層を形成して実施例１と同様のＮＯｘ吸蔵還元型のセラミック触媒体を作成した。
本例では，媒体攪拌ミルはバールミル装置（アシザワ（株）ＲＶ１Ｖ，有効容量１．０リットル，実容量０．５リットル）を用いる。バールミル装置による混合条件は，粉砕媒体としてジルコニア製ボール直径０．５ｍｍを３．０ｋｇ使用し，攪拌槽体積の８０％をジルコニア製ボールで充填する。
なお，ここで使用する混合液は実施例１と同様に超微粒子ＣｅＯ₂とＹ₂Ｏ₃（シーアイ化成製）を純粋に均一混合させて調整した混合液を用いる。
【図面の簡単な説明】
【図１】実施例１における，セラミック触媒体の要部説明図。
【図２】実施例１における，セラミック触媒体の全体説明図。
【図３】実施例１における，高圧分散混合処理装置の全体を示す説明図。
【図４】図３にかかる混合分散部の構成を示す説明図。
【図５】実施例２における，高速ミクサー装置の全体を示す説明図。
【図６】図５にかかる密閉耐圧容器の構成を示す説明図。
【図７】実施例３における，セラミック触媒体の要部説明図。
【符号の説明】
１．．．セラミック触媒体，
１０．．．孔部，
１１．．．セラミック担体，
１２．．．触媒安定層，
１３．．．触媒層，
２．．．高圧分散混合処理装置，
２１．．．高圧ポンプ，
２２．．．混合分散部，
２３．．．貯蔵槽，
２４．．．可動オリフィス，
２４０．．．先端，
ｄ１，ｄ２．．．圧縮空気，
ｅ１〜ｅ３．．．配管，
３．．．高速ミクサー装置，
３１．．．攪拌槽，
３１２．．．回転軸，
３１３．．．回転羽根，
３１４．．．密閉耐圧容器，
３２．．．貯蔵槽，
ａ１〜ａ４．．．配管，[0001]
【Technical field】
INDUSTRIAL APPLICABILITY The present invention can be used as a purification catalyst body for purifying exhaust gas from an internal combustion engine such as an automobile engine, and is particularly suitable as a catalyst body for purifying exhaust gas from a lean burn engine or a diesel engine and its ceramic catalyst body. It relates to a manufacturing method.
[0002]
[Prior art]
Conventionally, a so-called three-way catalyst that purifies exhaust gas by simultaneously oxidizing CO and HC and reducing NOx has been used as an exhaust gas purifying catalyst for automobiles.
In recent years, in order to protect the global environment, cleaner exhaust gas and CO₂Reduction of emissions is required, and lean burn engines that can reduce the amount of exhaust gas by improving fuel efficiency have been widely adopted.
[0003]
The conventional three-way catalyst does not perform its original function because the NOx purification performance decreases on the lean side (oxygen-excess atmosphere). To compensate for this, NOx occlusion reduction exhaust gas purification Catalysts have been developed.
The NOx occlusion reduction type exhaust gas purification catalyst stores NOx in a lean atmosphere in addition to a main catalyst composed of a noble metal catalyst such as Pt and Rh used in a conventional three-way catalyst. A NOx occlusion material that releases NOx occluded in a rich atmosphere (reducing atmosphere) is added as a promoter.
[0004]
As the NOx occlusion material, a strongly basic alkali metal such as Na, K, or Cs or an alkaline earth metal compound such as Mg, Sr, or Ba is used.
A NOx occlusion reduction type exhaust gas purification catalyst is described in, for example, Japanese Patent Application Laid-Open No. 6-31139, and a ceramic support made of cordierite or the like having low thermal expansion and excellent heat resistance is used for high-grade catalysts such as γ-alumina. It is disclosed that a NOx emission amount in a lean state can be reduced by a catalyst coated with a specific surface area material and supporting an alkali metal oxide and Pt.
The adsorbed NOx is released from the NOx occlusion material in a stoichiometric or rich atmosphere and purified by Pt. On the other hand, since the exhaust gas temperature tends to increase, it is important to improve the high temperature durability of the exhaust gas purification catalyst.
[0005]
However, an exhaust gas purifying catalyst in which an alkali metal compound is supported on a cordierite carrier as a NOx occlusion material has a problem that when the exhaust gas temperature becomes high, the NOx occlusion ability is lowered and the cordierite carrier is deteriorated.
This is considered to be caused by the fact that the alkali metal compound easily passes through the coating layer made of porous γ-alumina or the like and reacts with Si in cordierite.
[0006]
As a countermeasure, for example, Japanese Patent Laid-Open No. 10-165817 proposes to use a ceramic carrier or a metal carrier made of a low thermal expansion material not containing Si.
However, among α-alumina, zirconia, titania, titanium phosphate, aluminum titanate, stainless steel, and Fe-Al-Cr alloys exemplified in JP-A-10-165817, the thermal expansion properties are sufficiently low in practical use. Only very dense (heavy) aluminum titanate is shown.
[0007]
Aluminum titanate is disadvantageous in terms of vehicle weight reduction and expensive. Metal carriers are also expensive. Other ceramic materials have large thermal expansion and are not practical considering thermal shock resistance.
Thus, the fact is that no low-cost material with low thermal expansion coefficient to replace cordierite has been obtained.
[0008]
Further, in JP-A-10-137590, an exhaust gas purification filter that collects particulates discharged from a diesel engine is provided, and a coating layer made of silica, zirconia, titania or the like is provided on a ceramic filter such as cordierite. It is described that a catalyst component containing an alkali metal or alkaline earth metal sulfate is supported thereon, and that the diffusion of the catalyst component into the filter is suppressed by the coating layer.
[0009]
[Patent Document 1]
JP-A-6-31139
[Patent Document 2]
Japanese Patent Laid-Open No. 10-165817
[Patent Document 3]
Japanese Patent Laid-Open No. 10-137590
[0010]
[Problems to be solved]
However, as a result of investigations by the present inventors, the material of the coating layer described in the prior art is an alkali metal compound or an alkaline earth metal compound at a temperature of about 800 ° C., which is the operating temperature of the exhaust gas purification catalyst. After reaction, it was found that surplus alkali metal compounds and alkaline earth metal compounds can move and diffuse inside to reach the filter surface.
[0011]
Therefore, in the present situation where the maximum temperature of exhaust gas rises to around 1000 ° C., it is difficult to suppress the diffusion of alkali metal compounds and alkaline earth metal compounds with a coating layer made of these materials. And the problem that the composition of cordierite or the like serving as the filter base material reacts with the catalyst component to change and the thermal expansion coefficient increases cannot be said to be sufficiently solved at present.
[0012]
  The present invention has been made in view of such conventional problems, and has a low coefficient of thermal expansion and excellent high-temperature durability, the catalyst component is difficult to diffuse into the ceramic carrier, and the catalyst performance and deterioration of the ceramic carrier are unlikely to occur. Excellent catalyst performance can be maintained for a long timeMethod for producing ceramic catalyst bodyIs to provide.
[0013]
[Means for solving problems]
The first invention comprises a ceramic carrier, a catalyst stabilizing layer that covers the surface of the ceramic carrier and suppresses the diffusion of the catalyst component, and a catalyst layer that covers the surface of the catalyst stabilizing layer and contains the catalyst component. ,
In the method for producing a ceramic catalyst body, the surface potential of the catalyst stable layer and the surface potential of the catalyst layer are substantially the same, and the catalyst stable layer has a melting point higher than the highest use temperature.
Prepare the catalyst stable layer material that constitutes the catalyst stable layer,
A suspension in which the catalyst stable layer material is uniformly dispersed and mixed in a solvent is prepared,
In applying the suspension uniformly to the surface of the ceramic support and heat-treating the catalyst stable layer material to form the catalyst stable layer,
When preparing the suspension, a mixed liquid containing the catalyst stable layer material and the solvent is prepared, and a collision part is provided in the flow path of the mixed liquid, and the mixed liquid is applied to the collision part under high pressure. A method for producing a ceramic catalyst body is characterized by performing a high-pressure dispersion mixing process for uniformly dispersing and mixing a catalyst stable layer material in a solvent by collision.
[0014]
The second invention comprises a ceramic carrier and a catalyst layer covering the surface of the ceramic carrier and containing a catalyst component,
The catalyst layer contains a catalyst trap material capable of sucking the catalyst component and suppressing diffusion of the catalyst component, and the catalyst trap material has a melting point higher than the maximum use temperature.
Alternatively, the catalyst layer contains a catalyst active material capable of supplying hydrogen to the catalyst component by a steam reforming reaction, and the catalyst active material has a melting point higher than the maximum use temperature in the method for producing a ceramic catalyst body,
Preparing a catalyst layer material constituting the catalyst layer,
Preparing a suspension in which the catalyst layer material is uniformly dispersed and mixed in a solvent;
In applying the suspension uniformly to the surface of the ceramic carrier and heat-treating the catalyst layer material to form the catalyst layer,
When preparing the suspension, a mixed liquid containing the catalyst layer material and the solvent is prepared, and a collision part is provided in the flow path of the mixed liquid, and the mixed liquid collides with the collision part under high pressure. In the method for producing a ceramic catalyst body, a high-pressure dispersion mixing process is performed in which the catalyst layer material is uniformly dispersed and mixed in a solvent.
[0015]
The third invention comprises a ceramic carrier, a catalyst stable layer that covers the surface of the ceramic carrier and suppresses diffusion of the catalyst component, and a catalyst layer that covers the surface of the catalyst stable layer and contains the catalyst component. As
In the method for producing a ceramic catalyst body, the surface potential of the catalyst stable layer and the surface potential of the catalyst layer are substantially the same, and the catalyst stable layer has a melting point higher than the highest use temperature.
Prepare the catalyst stable layer material that constitutes the catalyst stable layer,
A suspension in which the catalyst stable layer material is uniformly dispersed and mixed in a solvent is prepared,
In applying the suspension uniformly to the surface of the ceramic support and heat-treating the catalyst stable layer material to form the catalyst stable layer,
When preparing the suspension, a mixed solution containing the catalyst stable layer material and the solvent is prepared, and a high-speed sealed stirring process is performed in which the mixed solution is stirred at high speed in a sealed space to apply a shearing force. The present invention resides in a method for producing a ceramic catalyst body (claim 5).
[0017]
  The first and third inventions are methods for producing a ceramic catalyst body comprising a ceramic carrier, a catalyst stabilizing layer, and a catalyst layer.SecondThe invention is a method for producing a ceramic catalyst body comprising a ceramic carrier and a catalyst layer, wherein the catalyst layer contains a catalyst trap material or a catalyst active material.
  Furthermore, the first and second inventions are manufacturing methods that utilize high-pressure dispersion mixing processing when uniformly dispersing and mixing the catalyst stable layer material and the catalyst layer material in a solvent.ThirdThe invention is a manufacturing method that uses high-speed hermetic stirring when uniformly dispersing and mixing.
[0018]
  The function and effect of the present invention will be described.
  In the present invention, a catalyst stable layer (first and third inventions) or a catalyst layer containing a catalyst trap material or a catalyst active material (Second(Invention) is formed by uniformly applying a suspension formed by uniformly dispersing and mixing a catalyst stable layer material or a catalyst layer material in a solvent to a ceramic carrier and then heat-treating it.
  Then, high-pressure dispersion mixing treatment (first and second inventions) or high-speed closed stirring means (ThirdInvention).
[0019]
Dispersion by the high-pressure dispersion mixing process or the high-speed hermetic stirring process prevents the catalyst stable layer material or the catalyst layer material from agglomerating and forming secondary particles in the solvent, and these are not dispersed in the primary particle size or near the primary particle size. It can be dispersed in a state having a particle size.
Furthermore, the suspension prepared by the high-pressure dispersion mixing process or the high-speed hermetic stirring process has a stable dispersion state for a long period of time, and re-aggregation of each material in the liquid hardly occurs.
[0020]
In this way, the catalyst stable layer and catalyst layer formed by applying a suspension that is difficult to reagglomerate to the ceramic support in a uniformly dispersed mixed state has a uniform surface potential and a uniform mixed composition in any part. Therefore, diffusion of the catalyst component to the ceramic carrier can be prevented.
Further, since the catalyst component is difficult to diffuse into the ceramic carrier, the catalyst performance is not deteriorated due to the diffusion of the catalyst component, and the ceramic carrier is hardly deteriorated. Therefore, it is possible to obtain a ceramic catalyst body in which the catalyst performance is hardly changed over a long period of time. it can.
That is, since the catalyst component is difficult to diffuse into the ceramic carrier, each catalyst component can be kept in a uniformly dispersed state in the catalyst layer. As described above, since the catalyst component is stably present in the catalyst layer, a ceramic catalyst body maintaining stable catalyst performance can be obtained.
Furthermore, it is possible to use a ceramic carrier made of a low thermal expansion material that could not be used on the premise of diffusion of the catalyst component in the past, and a ceramic catalyst body having a low thermal expansion coefficient can be obtained.
Moreover, even if the ceramic catalyst body is heated to a high temperature, the diffusion of the catalyst component is difficult to promote, so that a ceramic catalyst body that can be used up to the heat resistance limit of each material constituting the ceramic catalyst body can be obtained.
[0021]
Further, the high-pressure dispersion mixing process and the high-speed hermetic stirring process can efficiently and continuously disperse the catalyst stable layer material and the catalyst layer. And a suspension with a stable dispersion state can be created.
Therefore, according to the said process concerning this invention, a uniform suspension can be manufactured stably and a ceramic catalyst body can be manufactured stably.
[0027]
  As described above, according to the present invention, the low thermal expansion coefficient and the high temperature durability are excellent, the catalyst component is difficult to diffuse into the ceramic carrier, the catalyst performance is hardly lowered and the ceramic carrier is hardly deteriorated, and the excellent catalyst performance can be maintained for a long time. NaMethod for producing ceramic catalyst bodyCan be provided.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, first to firstThirdCeramic carrier, catalyst layer, catalyst component, catalyst stable layer, surface potential, maximum operating temperature, catalyst trap material, catalyst active material, catalyst stable layer material constituting catalyst stable layer, catalyst constituting catalyst layer The layer material, solvent, suspension, high-pressure dispersion mixing process, high-speed hermetic stirring process, etc. will be explained in order.
[0029]
  "Ceramic carrier"
  In the first to third inventions, the ceramic carrier is the base material of the ceramic catalyst body. It is preferable to use a ceramic carrier made of a honeycomb structure.
  Here, the honeycomb structure is a cylindrical structure having a large number of holes serving as gas flow paths for which catalytic performance is desired to act and having a honeycomb structure (see Example 1 described later).
  In the ceramic carrier, it is desirable that the surface on which the catalyst stable layer and the catalyst layer are formed includes not only the wall surface serving as the gas flow path but also the inner surface of the pores formed inside the wall surface.
[0030]
An example of manufacturing a honeycomb structure that can be used as the ceramic carrier of the present invention will be described.
When the honeycomb structure is made of cordierite, oxides such as talc, kaolin, and alumina can be generally used as a cordierite forming raw material.
A honeycomb having a desired shape is prepared by blending these cordierite-forming raw materials so as to have a theoretical composition, adding a molding aid such as a binder, a lubricant, a moisturizing agent and the like, kneading and extrusion molding. A molded body is obtained.
The honeycomb formed body is heated and degreased in the atmosphere and then fired to obtain a honeycomb structure. This honeycomb structure can be used as a ceramic carrier according to the present invention.
It should be noted that honeycomb carriers made of other materials can be produced by adjusting the raw materials in the same manner.
[0031]
  "Catalyst layer, catalyst component"
  1st and 3rdIn the invention, the catalyst layer is preferably formed by supporting a catalyst component on a coating layer made of a high specific surface area material such as γ-alumina.
  Also,SecondThe catalyst layer according to the present invention is preferably formed by supporting a catalyst trap material or a catalyst active material and a catalyst component on the coating layer.
[0032]
  In addition, it is possible to use exhaust gas purification catalysts for internal combustion engines (such as automobile engines), such as NOx occlusion reduction type catalysts for lean burn engines and diesel engines.ThirdWhen applying the ceramic catalyst body according to the invention, it is preferable to use a catalyst component obtained by adding a promoter such as a NOx occlusion material to a noble metal catalyst such as Pt, Rh, Pd or the like as the main catalyst.
[0033]
  "Catalyst stable layer"
  The catalyst stable layer has a melting point higher than the maximum use temperature and is formed from a catalyst stable layer material. The specific composition of the catalyst stable layer has been described above.Claims 8 to 11Etc. In addition to the catalyst stable layer material, the catalyst support layer may be prepared by adding a ceramic carrier, a material constituting the catalyst layer, a raw material of the material, or the like.
[0034]
  "Surface potential"
  First,ThirdIn the ceramic catalyst body produced by the invention, the surface potentials of the catalyst stable layer and the catalyst layer are substantially the same (that is, substantially equipotential), so that the catalyst component contained in the catalyst layer is not affected by the electric attractive force or repulsive force. Since it does not move and exists stably in the catalyst layer, it is possible to prevent the catalyst component from diffusing into the ceramic carrier at the maximum use temperature of the ceramic catalyst body.
[0035]
Here, the surface potential will be described.
The surface potential of various materials is generally defined by zeta potential. Therefore, also in this specification, the zeta potential of the material constituting the catalyst stable layer and the catalyst layer is measured, and the obtained measurement values are referred to as “surface potential of the catalyst stable layer” and “surface potential of the catalyst layer”, respectively. .
The material constituting the catalyst stable layer is the catalyst stable layer material, and the material constituting the catalyst layer is the catalyst layer material. Therefore, by adjusting the catalyst stable layer material, the type and composition ratio of the catalyst layer material, the surface potential values of the catalyst stable layer and the catalyst layer can be controlled to be equal.
Since the state of the catalyst layer material affects the catalyst performance, it is desirable to adjust the type and composition of the catalyst stable layer in order to obtain a ceramic catalyst body with better catalyst performance.
[0036]
A measurement example of the zeta potential will be described.
A dispersion in which the catalyst stable layer material and the catalyst layer material are dispersed in a solvent such as water is prepared, and the dispersion is prepared. These dispersions are used as evaluation samples and measured with a zeta electrometer.
There are several types of zeta electrometer measurement mechanisms.
For example, in the electrophoretic method, an electric field is applied from outside, the electrophoretic velocity corresponding to the surface potential of the dispersed particles in each dispersion is measured, the electric mobility is calculated from the electrophoretic velocity and the electric field, and the smoiuhowski equation is calculated. This method is used to obtain the zeta potential from the electric mobility.
In addition, water was used as a solvent in preparing the evaluation sample for measuring the zeta potential. In this case, the hydrogen ion concentration of water (pH value, hereinafter referred to as pH) is usually set in the range of pH 3 to 11 and any pH. The zeta potential is measured at.
The pH is adjusted with a nitric acid solution and an ammonia solution so as to obtain a desired pH. In this way, a zeta potential corresponding to the pH can be obtained.
[0037]
In addition to the above method for obtaining the zeta potential from the catalyst stable layer material and the catalyst layer material, the zeta potential can also be measured using the streaming potential method on the surface of the catalyst stable layer and the catalyst layer formed on the ceramic carrier. it can.
Here, the streaming potential method is a method in which a medium is caused to flow on the surface of a sample to be measured, and the zeta potential is obtained from the relationship between the generated potential difference and the pressure difference.
[0038]
Moreover, in order to adjust the surface potential of the catalyst stable layer, the catalyst stable layer can be produced as a multilayer structure using a plurality of catalyst stable layer materials.
In other words, in order to produce a multilayer catalyst stable layer, a suspension is prepared for each layer, and a series of steps of immersing, drying and firing the ceramic carrier in each suspension is repeated to form a multilayer catalyst stable layer. Obtainable.
[0039]
"Maximum operating temperature"
The catalyst stable layer material constituting the catalyst stable layer is a material having a melting point higher than the maximum use temperature of the ceramic catalyst body. In the case of an exhaust gas purifying catalyst for an internal combustion engine, the catalyst temperature during use is usually about 800 to 900 ° C. and rises to around the maximum temperature of 1000 ° C. Therefore, a material having a melting point of 1000 ° C. or higher is used.
When the melting point is lower than the maximum operating temperature, the catalyst stable layer melts at the maximum operating temperature, which may reduce the effect of suppressing the diffusion of catalyst components.
[0040]
"Catalyst layer material"
When the catalyst layer is formed by supporting a catalyst component, a catalyst trap material, a catalyst active material, etc. on a coat layer made of a high specific surface area material such as γ-alumina, the main component of γ-alumina and catalyst components (for example, precious metal catalysts) A catalyst or a promoter such as a NOx occlusion material is the catalyst layer material. In addition, to prevent thermal degradation of γ-alumina, TiO₂, ZrO₂Can be used.
[0041]
"Catalyst trap material"
By dispersing the catalyst trap material in the catalyst layer, the following effects can be obtained.
That is, the catalyst trap material sucks the catalyst component supported on the catalyst layer with the surface potential and captures it around the catalyst trap material, thereby preventing the catalyst component from diffusing into the ceramic carrier. Therefore, the catalyst component can be uniformly dispersed and held in the catalyst layer.
In addition, since the catalyst component is difficult to diffuse and react with the ceramic carrier, problems such as increased thermal expansion of the ceramic carrier are unlikely to occur, and a ceramic catalyst body that is inexpensive, excellent in high-temperature durability, and maintains stable catalyst performance over a long period of time can be obtained. It is done.
The catalyst trap material is preferably made of a material having a melting point higher than that of the ceramic catalyst body.
[0042]
The amount of the catalyst trap material is not particularly limited, but it may be added in a range of 3 to 30% by weight with respect to a high specific surface area material such as γ-alumina constituting the coating layer of the catalyst layer. preferable.
A remarkable effect can be obtained by setting the addition amount of the catalyst trap material to 3% or more. When the addition amount exceeds 30%, the effect according to the addition amount is not improved and the effect is saturated.
A specific example of the catalyst trap material will be described later.
[0043]
"Catalytic active material"
By dispersing the catalyst active material in the catalyst layer, the following effects can be obtained. That is, the catalyst active material attracts the catalyst component supported on the catalyst layer with the surface potential and captures it around the catalyst active material, thereby preventing the catalyst component from diffusing into the ceramic carrier. Therefore, the catalyst component can be uniformly dispersed and held in the catalyst layer.
In addition, since the catalyst component is difficult to diffuse and react with the ceramic carrier, problems such as increased thermal expansion of the ceramic carrier are unlikely to occur, and a ceramic catalyst body that is inexpensive, excellent in high-temperature durability, and maintains stable catalyst performance over a long period of time can be obtained. It is done.
In addition to such effects, the catalyst activator supplies hydrogen to the catalyst layer by a steam reforming reaction, whereby the surface activity of the catalyst component is increased and the catalyst reaction can be promoted.
The catalytically active material is preferably composed of a material having a higher melting point than the ceramic catalyst body.
[0044]
The catalytically active material has an action of supplying hydrogen generated by the steam reforming reaction to a catalyst component, particularly a noble metal catalyst such as Pt or Rh. This increases the active surface on the surface of the catalyst component. Since the increase in the active surface promotes the catalytic reaction, the catalyst performance can be enhanced.
Therefore, ceramic catalyst bodies equipped with a catalyst layer containing a catalyst activator can burn gasoline engine three-way catalysts and PM (particulate matter) that need to maintain long-term high purification performance and high activity. Can be suitably used for NOx catalyst, DPF (diesel particulate filter), etc.
[0045]
The amount of the catalytically active material used is not particularly limited, but may be added in a range of 3 to 50% by weight with respect to a high specific surface area material such as γ-alumina constituting the coating layer of the catalyst layer. preferable.
A remarkable effect can be obtained by setting the addition amount of the catalytically active material to 3% or more. If the addition amount exceeds 50%, the effect corresponding to the addition amount is not improved, and saturation occurs.
[0046]
  "Suspension" and "Solvent"
  In the first and third inventions, the suspension is prepared by uniformly dispersing and mixing the catalyst stable layer material in a solvent,SecondIn the invention, the catalyst layer material is prepared by uniformly dispersing and mixing in a solvent. As a solvent for dispersing the catalyst stable layer material or the catalyst layer material, water, alcohol, ethylene glycol, a dispersant, a mixed solvent thereof or the like can be used.
[0047]
"High-pressure dispersion mixing process", "High-speed sealed mixing process"
The present inventors used a high-pressure dispersion mixing process to obtain a suspension in which the catalyst stable layer material is uniformly dispersed and mixed in the solvent, or to obtain a suspension in which the catalyst layer material is uniformly dispersed and mixed in the solvent.
In the high pressure dispersion mixing process, a catalyst stable layer material or a mixed solution containing the catalyst layer material and a solvent is prepared, and the mixed solution collides with each other under a high pressure to make the catalyst stable layer material or the catalyst layer material uniform in the solvent. To disperse and mix.
[0048]
Moreover, a high-speed closed stirring process was used to obtain a suspension in which the catalyst stable layer material was uniformly dispersed and mixed in the solvent, or to obtain a suspension in which the catalyst layer material solvent was uniformly dispersed and mixed in the solvent.
The high-speed sealed stirring treatment is performed by preparing a catalyst stable layer material or a mixed solution containing the catalyst layer material and a solvent, and stirring the mixed solution at high speed in a sealed space to apply a shearing force. Alternatively, the catalyst layer material is uniformly dispersed and mixed in a solvent.
[0049]
Which part of the catalyst stable layer or catalyst layer formed by applying the catalyst reconstituting layer material or the suspension that is difficult to reaggregate obtained by uniformly dispersing and mixing the catalyst layer material to the solvent to the ceramic support in a uniformly dispersed mixed state Is also provided with a uniform surface potential and a uniform mixed composition, so that diffusion of the catalyst component to the ceramic carrier can be prevented.
[0050]
Next, in the first and second inventions, when the high-pressure dispersion mixing process is performed in the mixing and dispersing section provided to move the movable orifice up and down,
It is preferable that the liquid mixture pumped to the mixing / dispersing part collides with the tip of the movable orifice exposed inside the mixing / dispersing part under high pressure (Claim 3) (see FIGS. 3 and 4).
[0051]
According to the above method, a pressure change or a shock wave can be formed in the vicinity of the place where the mixed liquid collides with the movable orifice. These pressure changes and shock waves give the mixture a high degree of refinement, dispersion, emulsification, mixing, etc., so that the catalyst stable layer material (in the case of the first invention) and the catalyst layer material (in the case of the second invention) Can be efficiently and reliably uniformly dispersed and mixed with the solvent to produce a suspension in a stable dispersion state for a long period of time.
[0052]
Further, since the liquid mixture introduced by the movable orifice can variably control the volume of the flow path, the volume of the flow path can be adjusted according to the particle size and concentration of the material.
Thereby, the dispersion mixing can be optimally controlled and stably performed.
[0053]
In addition, a high-pressure homogenizer can be used for the high-pressure dispersion treatment. The high-pressure homogenizer pumps the liquid mixture at a high pressure to form a high-speed flow, and forms a shock wave by the high-speed flow to form a catalyst stable layer material (in the case of the first invention) and a catalyst layer material (in the second invention). In this case, a uniform suspension can be obtained by breaking the agglomerated part in the case) and dispersing it to the state of primary particles. Furthermore, by feeding the mixture at high pressure, mechanical shearing force is applied to the mixture, and the catalyst stable layer material (in the case of the first invention) and the catalyst layer material (in the case of the second invention) are solvent. Can be uniformly dispersed.
[0054]
Next, in the first and second inventions, the high-pressure dispersion mixing treatment is preferably performed at a pressure of 50 to 400 MPa.
[0055]
As a result, the catalyst stable layer material (in the case of the first invention) and the catalyst layer material (in the case of the second invention) in the suspension are efficiently and reliably uniformly dispersed and mixed with the solvent, and stable for a long time. A suspension in a dispersed state can be obtained.
If the pressure is less than 50 MPa, the pressure is low, and dispersion into the solvent may be insufficient, or precipitation may occur in the suspension in a relatively short time. Moreover, it is difficult to apply a pressure exceeding 400 MPa to the mixed solution, which may increase the cost. Therefore, such high pressure is not a realistic choice.
[0056]
  ThirdIn the present invention, the high-speed hermetic stirring treatment includes a hermetic pressure vessel and a rotating vessel that is rotatably attached to a rotary shaft provided inside the hermetic pressure-resistant vessel, and has a rotating blade slightly smaller in diameter than the inner diameter of the hermetic pressure-resistant vessel. In
  It is preferable to apply a shearing force by stirring the mixed solution at a high speed.6).
[0057]
The catalyst stable layer material or a mixed solution in which the catalyst layer material is mixed with the solvent is prepared, and the mixed solution is pumped to the stirring tank. The liquid mixture pumped into the stirring tank is pressed against the inner wall surface of the sealed pressure vessel by the centrifugal force formed by the rotation of the rotating blades in the sealed pressure vessel. A mechanical shearing force due to the shear stress generated thereby can be applied to the mixed liquid.
[0058]
In the above configuration, since the gap between the sealed pressure vessel and the rotating blade is very small, all the liquid mixture existing near the tip of the rotating blade (the end near the inner wall surface) is stirred by the rotating blade. Highly refined, dispersed, mixed, and emulsified. In addition, the liquid mixture inside and outside the rotating surface of the rotary blade is subjected to a mixing action due to a speed difference during the rotational movement due to the inertia of the liquid mixture itself, generation of vortex flow, and the like.
[0059]
According to this, the catalyst stable layer material (in the case of the first invention) and the catalyst layer material (in the case of the second invention) are efficiently and surely uniformly dispersed and mixed with the solvent, and the dispersion state is stable for a long time. A suspension can be obtained.
[0060]
Next, formation of the catalyst stable layer and formation of the catalyst layer will be described.
In the first and third inventions, the catalyst stable layer is formed, and the catalyst layer is formed thereon.
An example of forming the catalyst stable layer on the ceramic support will be described.
A suspension is prepared by uniformly dispersing and mixing the catalyst stable layer material constituting the catalyst stable layer in a solvent by a high-pressure dispersion mixing process and high-speed closed stirring means. Thereafter, the ceramic carrier is immersed in the suspension, and dried and fired by a usual method.
[0061]
In order to form the catalyst stable layer uniformly on the surface of the ceramic carrier, it is preferable to form an intermediate layer on the surface of the ceramic carrier prior to the formation of the catalyst stable layer.
In general, since the surface of the ceramic support has irregularities made up of a large number of pores formed at the time of firing, it is not easy to uniformly form a catalyst stable layer on the surface without causing pores or cracks.
[0062]
Therefore, by forming an intermediate layer in advance, reducing the irregularities on the surface of the ceramic carrier, and forming a catalyst stable layer on the intermediate layer, a uniform catalyst stable layer free from pores and cracks can be obtained. By providing a catalyst layer on the surface of such a catalyst stable layer, diffusion of the catalyst component in the catalyst layer to the ceramic carrier can be prevented.
[0063]
The ceramic material constituting the intermediate layer is not particularly limited, but is preferably a ceramic material having a melting point higher than the maximum use temperature, preferably a ceramic material having a melting point of 1000 ° C. or higher.
Further, when a ceramic material having a thermal expansion coefficient close to that of the ceramic support and the catalyst stable layer is selected, an effect of relieving stress due to the thermal expansion difference is obtained.
The method of forming the intermediate layer is the same as the method of forming the catalyst stable layer, and the intermediate layer is obtained by immersing the ceramic carrier in a suspension containing the ceramic material constituting the intermediate layer, and drying and firing. Can do.
[0064]
The ceramic particles forming the catalyst stable layer and the intermediate layer should have an average primary particle size of not more than the average pore size (usually about 5 μm) of the ceramic support, preferably not more than 1/10 of the average pore size. Is preferred. Thereby, a catalyst stable layer and an intermediate | middle layer can be uniformly and easily formed along the uneven | corrugated shape of the pore surface of a ceramic support | carrier.
The term “pore” as used herein refers to a hole formed in the surface of the ceramic carrier and a space communicating from the surface to the inside, and is an irregular pore space.
[0065]
Further, the catalyst stabilizing layer and the intermediate layer are preferably formed so as to cover the surface of the pores thinly without filling the pores of the ceramic support, and the thickness at this time is preferably about 1 to 3 μm, for example. preferable.
If the pores are filled with the catalyst stable layer and the intermediate layer, cracks and the like are likely to occur due to the difference in thermal expansion. In addition, the anchor effect when the catalyst layer is formed thereon cannot be expected, and the adhesive strength of the catalyst layer may be reduced.
[0066]
In addition, as a method for forming the catalyst layer on the surface of the catalyst stable layer, for example, the catalyst component is dispersed in a slurry containing a high specific surface area material such as γ-alumina to form the coat layer on the ceramic carrier and simultaneously the catalyst component is formed. It can be formed simultaneously.
In addition, the surface of the ceramic carrier provided with the catalyst stabilizing layer is covered with a coating layer made of a high specific surface area material such as γ-alumina, and then immersed in a solution containing the catalyst component and dried to carry the catalyst component on the coating layer. You can also.
[0067]
  Also,SecondIn the invention, a catalyst layer containing a catalyst trap material or a catalyst active material together with a catalyst component is formed on the surface of the ceramic carrier. For the formation of this catalyst layer, the same procedure as the formation of the catalyst stable layer can be used.
  That is, a catalyst component, a catalyst trap material or a catalyst active material is uniformly dispersed and mixed in a slurry containing γ-alumina to obtain a suspension according to the present invention, and a ceramic carrier is immersed in the suspension and dried. The catalyst layer can be supported and formed.
[0068]
  Also, first to firstThirdIn the present invention, when the suspension is uniformly applied to the surface of the ceramic carrier, it is preferable to apply ultrasonic waves to the suspension (claim).7).
  As a result, the catalyst stable layer material in the suspension (first and third inventions) and the catalyst layer material (SecondInventive) can be prevented from agglomeration and secondary particle formation, and a dispersed state having a primary particle size or a particle size of about the primary particle size can be maintained.
[0069]
  In the first and third inventions, the catalyst stabilizing layer is formed of the Group 1B, Group 2B, Group 3A, Group 3B, Group 4A, Group 5A, Group 6A, Group 7A of the Periodic Table of Elements. And at least one element selected from Group 8 elements.8).
  By including a material containing these elements, the surface potential of the catalyst stable layer can be easily controlled to be equal to the surface potential of the catalyst layer.
[0070]
  In addition, the catalyst stable layer includes La, Y, Sc, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, Lu, Al, Ga, Zn, Cu, Ti, Zr, Hf, It is made of a material containing at least one element selected from V, Nb, Ta, Cr, Mo, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt. Preferred (claims)9).
[0071]
  A compound containing one or more elements arbitrarily selected from these elements, such as oxides and composite oxides, can be used for the catalyst stable layer.
  Specifically, the catalyst stable layer is Y₂O_Three, Sc₂O_Three, TiO, Cr₂O_Three, MnO, Mn₂O_Three, Mn₂O_Five, Fe ₂ O_Three, Fe_ThreeO_Four, Co_ThreeO_Four, NiO, ZnO, CuO, Ga₂O_Three, ZrO₂, Zr₂O_Three, Nb₂O_Five, SnO₂, CeO₂, Pr₂O_Three, PrO_Four, Nd₂O_Three, Sm₂O_Three, Eu₂O_Three, Gd₂O_Three, Tb₂O_Three, Dy₂O_Three, Ho ₂O_Three, Er₂O_Three, Tm₂O_Three, Yb₂O_Three, Lu₂O_Three, HfO₂, Ta₂O_Five ,And Al₂O_ThreeIt is preferable to consist of one or more materials selected from10).
[0072]
  Above all, the catalyst stable layer is Y₂O_ThreeAnd CeO₂It is most preferable to include at least one of the following (claims)11). This material has an extremely high effect of keeping the surface potential of the catalyst stable layer and the catalyst layer equal and suppressing the diffusion and diffusion of catalyst components.
[0073]
In addition to oxides (composite oxides), non-oxides such as carbides and nitrides (can also be used as complex non-oxides) can also be used. Can be used as
Thus, according to the surface potential of the catalyst layer containing the catalyst component, an appropriate substance is selected from the above-mentioned compounds, or a plurality of compounds are selected and combined at an appropriate composition ratio, so that the catalyst stable layer and the catalyst layer Are controlled so as to have the same surface potential.
[0074]
  SecondofIn the present invention, the catalyst trap material is preferably made of a powder having an average primary particle size of 500 nm or less (claims).12).
  Since the catalyst trap material has a large surface area per unit weight of fine particles having an average primary particle diameter of 500 nm or less, the effect of the present invention can be obtained with a small amount of addition, and the material cost can be saved.
  When the average primary particle diameter is less than 10 nm, the particles may aggregate and form secondary particles, which may make it difficult to uniformly disperse and mix. Therefore, the lower limit diameter of the catalyst trap material may be 10 nm. preferable.
[0075]
  Also,SecondIn the present invention, the catalyst trap material is Y₂O_Three, Sc₂O_Three, NiO, ZnO, CuO, CeO₂, Pr₂O_Three, PrO_Four, Nd₂O_Three, Sm₂O_Three, Eu₂O_Three, Gd₂O_Three, Tb₂O_Three, Dy₂O_Three, Ho₂O_Three, Er₂O_Three, Tm₂O_Three, Yb₂O_Three, Lu₂O_ThreeAnd Al₂O_ThreeIt is preferable to consist of one or more materials selected from13).
  The catalyst trap material made of the above material is only uniformly dispersed in the catalyst layer and hardly reacts with other components (catalyst components, etc.) of the catalyst layer. Therefore, a catalyst layer having stable catalyst characteristics can be obtained without formation of by-products or the like.
[0076]
  Also,SecondIn the present invention, the catalytically active material is preferably made of a material containing at least one element selected from lanthanoid elements.14).
  This material undergoes a steam reforming reaction with high selectivity, and can efficiently supply hydrogen to the catalyst layer.
  Furthermore, as a specific example of the material containing the above elements, Y₂O_Three, CeO₂, Pr₂O_Three, PrO_Four, Nd₂O_Three, Sm₂O_Three, Eu₂O_Three, Gd₂O_Three, Tb₂O_Three, Dy₂O_Three, Ho₂O_Three, Er₂O_Three, Tm₂O_Three, Yb₂O_ThreeAnd Lu₂O_ThreeOne or more materials selected from15).
  All of these materials are thermally stable oxide materials. Therefore, when the ceramic catalyst body is used for a long time at a high temperature, the ceramic catalyst body is hardly deteriorated.
[0077]
  Particularly preferred compounds are one or more materials selected from at least Ce oxides or complex oxides, which are particularly active in steam reforming reactions and can efficiently supply hydrogen to the catalyst layer. Term16).
  It is considered that Ce oxide or composite oxide has excellent characteristics of oxygen adsorption / desorption, and the steam reforming reaction proceeds smoothly.
[0078]
  Further, the catalytically active material is CeO.₂And Y₂O_Three, TiO₂, ZrO₂And Al₂O_ThreeIt is preferable to comprise a mixed oxide obtained by mixing at least one oxide selected from17).
  CeO₂Is particularly active in steam reforming reactions.₂O_Three, TiO₂, ZrO₂And Al₂O_ThreeBy selecting one or more of these as mixed oxides, a steam reforming reaction can be caused more selectively and hydrogen can be efficiently supplied to the catalyst layer.
[0079]
Among the materials exemplified as the catalyst active material, there is a material that functions as a catalyst trap material. In this way, a catalyst layer containing both the catalyst activator and the functional trap material can be obtained.
In this case, in addition to the effect of increasing the activity by supplying hydrogen to the catalyst component, the ceramic carrier can be protected by sucking and capturing the catalyst component to suppress diffusion.
[0080]
  Also, first to firstThirdIn the present invention, the catalyst component contains a compound comprising at least one element selected from alkali metal elements and alkaline earth metal elements (claim)18) Is preferred.
  These metal element compounds have a high NOx storage effect. Therefore, when the catalyst component contains these compounds, the ceramic catalyst body according to the present invention can be used as an exhaust gas purifying catalyst.
[0081]
  Further, among the above compounds, it is particularly preferable to include a compound composed of at least one element selected from Li, Na, K, Ba, Rb, Be, Mg, Ca and Sr.19).
  Specifically, oxides, acetates, nitrates, sulfates and the like related to the above elements, composite compounds composed of these oxides and salts, and the like can be used.
  More preferably, a compound containing Ba, K, Li having excellent NOx occlusion ability, for example, barium acetate, potassium acetate, lithium nitrate, etc. can be suitably used.
  Note that the catalyst components listed here are merely examples, and catalyst layers made of different catalyst components are employed when producing a ceramic catalyst body used for other purposes.
[0082]
  The ceramic carrier has a thermal expansion coefficient of 1.5 × 10^Four/ C or less is preferable (claims)20).
  Such a ceramic carrier has high thermal shock resistance, and it is difficult to cause thermal shock destruction when used for an exhaust gas purifying catalyst into which high-temperature exhaust gas flows.
  Thermal expansion coefficient is 1.5 × 10^FourIf the temperature is higher than / ° C, impact resistance may deteriorate and high temperature durability may deteriorate.
  In addition, the lower limit of the thermal expansion coefficient is generally set to 0 or more so that the ceramic catalyst body is fixed in a metal housing and used so as not to be remarkably contracted and difficult to be fixed. It is preferable to do.
[0083]
  The ceramic support preferably contains cordierite.21).
  By using a cordierite material having a low thermal expansion coefficient as the ceramic carrier, a ceramic catalyst body excellent in thermal shock resistance can be obtained. A catalyst body excellent in thermal shock resistance is unlikely to undergo thermal shock destruction when used as an exhaust gas purification catalyst into which high-temperature exhaust gas flows.
  Cordierite is a material with excellent high-temperature durability. Therefore, the performance of the catalyst component in the catalyst layer can be maintained for a long time. Furthermore, cordierite is inexpensive and can reduce manufacturing costs.
[0084]
Cordierite is 2MgO · 2Al₂O_Three・ 5SiO₂It is a complex oxide represented by the chemical formula: It is a low thermal expansion material that has excellent heat resistance and is inexpensive.
In addition, as a ceramic carrier, for example, SiC, Si_ThreeN_FourIt is also possible to use a material made of a ceramic material containing Si.
[0087]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
The ceramic catalyst body according to the present invention will be described with reference to FIGS.
The ceramic catalyst body 1 according to this example includes a ceramic carrier, a surface of the ceramic carrier, a catalyst stabilizing layer 12 that suppresses diffusion of the catalyst component, a surface of the catalyst stabilizing layer 12, and a catalyst component. In addition to the catalyst layer 13, the surface potential of the catalyst stable layer 12 and the surface potential of the catalyst layer 13 are substantially the same, and the catalyst stable layer 12 has a melting point higher than the maximum use temperature.
[0088]
When the ceramic catalyst body 1 is manufactured, first, a catalyst stable layer material constituting the catalyst stable layer 12 is prepared, and a suspension is prepared by uniformly dispersing and mixing the catalyst stable layer material in a solvent. Next, the catalyst stable layer 12 is formed by uniformly applying the suspension to the surface of the ceramic carrier and heat-treating the catalyst stable layer material.
When preparing the suspension, a mixed liquid containing the catalyst stable layer material and the solvent is prepared, and the mixed liquid collides with each other under high pressure to uniformly disperse the catalyst stable layer material in the solvent. A high-pressure dispersion mixing process is performed.
[0089]
This will be described in detail below.
As shown in FIGS. 1 and 2, the ceramic catalyst body 1 according to the present example has a ceramic carrier made of cordierite as a base material, and an intermediate layer (not shown) made of silica is formed on the surface thereof. The catalyst stable layer 12 is formed on the surface of the catalyst, and the catalyst layer 13 is formed on the surface of the catalyst stable layer 12.
The ceramic catalyst body of this example is installed in the exhaust pipe of an automobile engine and used for purifying exhaust gas discharged from the engine.
[0090]
The ceramic carrier is a honeycomb structure, and as shown in FIGS. 1 and 2, the ceramic carrier has a large number of holes 10 serving as exhaust gas passages for allowing the catalyst to act, and the surface on which the catalyst stabilizing layer 12 is formed is a gas passage. It is the wall surface 100 of the hole 10 facing the surface. Moreover, the arrow line Z shown in FIG. 2 is a direction used as the flow path of the exhaust gas which makes a catalyst act.
FIG. 1A is an explanatory diagram showing a state in which the hole 10 is enlarged. In this way, the catalyst stable layer 12 is formed so as to cover the wall surface 100, and the catalyst layer 13 including a catalyst component described later is formed so as to cover the catalyst stable layer 12. In FIG. 1B, the wall surface 100 is further enlarged.
[0091]
The catalyst stable layer 12 is CeO.₂And Y₂O_ThreeThe catalyst layer 13 comprises a coating layer made of γ-alumina and a catalyst component made up of a main catalyst and a cocatalyst. The surface of the coating layer made of γ-alumina in the catalyst layer 13 is an uneven surface, and the catalyst component is physically adsorbed on the uneven surface.
The main catalyst is a noble metal catalyst, and the promoter is a NOx storage material. Specifically, the main catalyst is composed of Pt and Rh, and the promoter is a potassium compound (K₂O). The main catalyst is a conventionally known three-way catalyst, and the cocatalyst occludes NOx in a lean atmosphere, and releases NOx occluded in a stoichiometric (theoretical air-fuel ratio) and rich atmosphere (reducing atmosphere). It is.
Further, the surface potential of the catalyst layer 13 and the surface potential of the catalyst stable layer 12 are substantially equal, and in the actual use range of the ceramic catalyst body of this example, pH 7 to 10, both are 2 mV at pH 7, -2 mV at pH 8, and -9 at pH 9. It is -7 mV at 7 mV and pH 10.
Here, the surface potential measurement method will be explained. Prepare an evaluation sample of a catalyst layer or a catalyst stable layer for which the surface potential is to be measured, adjust the pH within a range of 5 to 11 with dilute hydrochloric acid solution and potassium hydroxide solution, and then measure the surface potential. The zeta potential, which is a substitute value for, is measured.
[0092]
The zeta potential was measured by a streaming potential method using a zeta potential measuring device (Nihon Sebel Hegner EKA) (measurement temperature: 23 to 25 ° C., pH adjusting solution: 0.01 N HCl and 0.01 N KOH). ).
The measurement procedure is shown below.
1) An evaluation sample (plate shape, 21 mm × 60 mm × 2 mm) is placed in the capillary tube of the evaluation unit of the zeta potential measurement device.
2) Extrude the electrolytic solution (0.01N-HCl and 0.01N-KOH) into the capillary tube at a constant pressure with compressed air.
3) Measure the generated electromotive force.
Hereinafter, the flow electromotive force generated in the capillary tube is measured while changing the differential pressure.
Moreover, the pH value of the electrolyte solution to be evaluated is adjusted to 0.01N-HCl and 0.01N-KOH solution, and the flow electromotive force is measured at the pH on the acid side and the alkali side. The pH value was the value at the end of measurement.
[0093]
Next, a method for producing the ceramic catalyst body according to this example will be described.
First, a ceramic support having a honeycomb structure is manufactured.
Talc, kaolin, alumina, and aluminum hydroxide were prepared as raw materials for cordierite, and these raw material powders were blended so as to be near the cordierite theoretical composition point.
Appropriate amounts of binder, lubricant, humectant and moisture were added to the blended material and kneaded. The kneaded product was extruded as a honeycomb formed body having a wall thickness of 100 μm, a cell density of 400 cpsi (number of holes per square inch), and a diameter of 50 mm.
The honeycomb formed body was degreased by heating to 800 ° C. in an air atmosphere, and then fired at 1390 ° C. for 2 hours. Thereby, a ceramic carrier was obtained.
[0094]
Next, an intermediate layer is provided on the ceramic carrier.
In order to allow uniform coating of the catalyst stable layer, this intermediate layer was formed by immersing a ceramic support in a silica sol (Nissan Chemical Co., Ltd., colloidal silica) solution, drying and firing.
[0095]
Next, a catalyst stable layer is formed.
As the catalyst stable layer material, ultrafine particles having an average particle diameter of 100 to 300 nm (Nanotech Ultrafine Particles manufactured by C-I Kasei Co., Ltd.) were used. These ultrafine particles are CeO₂And Y₂O_ThreeAll have a melting point of 1000 ° C. or higher.
The ultrafine particles were dispersed and uniformly mixed in pure water (in this example, pure water was used as a solvent) to prepare a suspension.
[0096]
The suspension according to this example was prepared using a high-pressure dispersion mixing process.
That is, in this example, a high-pressure homogenizer is used in the high-pressure dispersive mixing process, but a high-speed flow is formed by pumping a liquid mixture obtained by mixing the catalyst stable layer material with pure water into the high-pressure homogenizer, and a shock wave due to the high-speed flow is generated. A uniform suspension is produced by forming and destroying the agglomerated portion of the catalyst stable layer material in the solvent and dispersing the catalyst stable layer material to a primary particle state.
Furthermore, since the pumping to the high-pressure homogenizer is performed at a high pressure, a mechanical shearing force can be applied to the mixture during the pumping. This shearing force is also effective for dispersing the catalyst stable layer material in the mixed solution.
At this time, the pressure inside the high-pressure homogenizer was 200 MPa.
[0097]
The entire ceramic carrier provided with the intermediate layer is immersed in the suspension prepared as described above, and then pulled up from the suspension and dried. As a result, the suspension was uniformly applied to the surface of the ceramic carrier.
After drying, it was fired at 1000 ° C. in the atmosphere to sinter the catalyst stable layer material in the suspension to obtain a ceramic carrier having a catalyst stable layer on the surface.
[0098]
Next, a catalyst layer is formed on the ceramic support provided with the catalyst stable layer.
First, the main catalyst (Pt, Rh), the promoter (K₂O) was slurried in a solvent water. The slurry was coated with a ceramic carrier provided with the above catalyst stable layer, dried, and then fired at 1000 ° C. in the atmosphere to form a catalyst layer on the surface.
This obtained the ceramic catalyst body concerning this example.
[0099]
The effect concerning this example is demonstrated.
The ceramic catalyst body according to this example utilized high-pressure dispersion mixing processing when obtaining a suspension used for forming a catalyst stable layer. In addition, a high-pressure homogenizer was used for the above treatment.
[0100]
Dispersion by the high-pressure dispersion mixing treatment prevents aggregation of the catalyst stable layer material in the solvent and formation of secondary particles, and disperses them in a state having a primary particle size or a particle size close to the primary particle size. Can do.
Furthermore, the suspension prepared by the high-pressure dispersion mixing process has a stable dispersion state over a long period of time, and re-aggregation of each material in the liquid hardly occurs.
[0101]
The catalyst stabilization layer obtained from the suspension having such characteristics can prevent the catalyst component from diffusing into the ceramic support.
Further, since the catalyst component is difficult to diffuse into the ceramic carrier, the catalyst performance is not deteriorated due to the diffusion of the catalyst component, and the ceramic carrier is hardly deteriorated. Therefore, it is possible to obtain a ceramic catalyst body in which the catalyst performance hardly changes for a long time. it can.
[0102]
Further, it is possible to use a ceramic support made of cordierite having a low thermal expansion that could not be used on the premise of the diffusion of the catalyst component in the past, and a ceramic catalyst body having a low thermal expansion coefficient can be obtained.
Moreover, even if the ceramic catalyst body is heated to a high temperature, the diffusion of the catalyst component is difficult to promote, so that a ceramic catalyst body that can be used up to the heat resistance limit of each material constituting the ceramic catalyst body can be obtained.
[0103]
Therefore, according to the manufacturing method of this example, the low thermal expansion coefficient and excellent high temperature durability, the catalyst component hardly diffuses into the ceramic carrier, the catalyst performance is hardly deteriorated and the ceramic carrier is hardly deteriorated, and the excellent catalyst performance is maintained for a long time. A ceramic catalyst body that can be maintained over a wide range can be obtained.
[0104]
Further, the high-pressure dispersion mixing process for preparing the suspension can be performed in the mixing / dispersing section 22 provided so as to move the movable orifice 24 up and down as shown in FIGS.
As shown in FIG. 4, the high-pressure dispersion mixing apparatus 2 used here collides the liquid mixture pumped to the mixing / dispersing part 22 under high pressure on the tip 240 of the movable orifice 24 exposed inside the mixing / dispersing part 22. Let
As shown in FIG. 3, the above operation is performed by circulating a suspension (mixed solution) between the mixing and dispersing unit 22 and the storage tank 23 connected by the pipes e1, e2, and e3.
The suspension (mixed liquid) entered from the pipe e1 collides with the tip 240, branches, flows out from the two outlets 221, 222, joins at the pipe e3, and returns to the storage tank 23. The suspension again circulates from the storage tank 23 to the mixing and dispersing unit 22 through the pipes e2 and e1.
The high pressure pump 21 is provided for driving the movable orifice 24, and the high pressure pump 21 and the movable orifice are driven by the compressed air applied to the arrows d1 and d2.
[0105]
(Example 2)
In this example, a suspension for forming a catalyst stable layer is prepared by a method different from that in Example 1.
In this example, a suspension containing a catalyst stable layer material and a solvent is prepared, and the mixture is stirred at high speed in a sealed space to apply shearing force to apply a high-speed sealed stirring process. , CeO of catalyst stable layer material₂And Y₂O_ThreeAre uniformly dispersed and mixed in pure water as a solvent.
That is, as shown in FIGS. 5 and 6, the sealed pressure vessel 314 and the rotary shaft 312 provided inside the sealed pressure vessel 314 are rotatably attached to the rotary blade having a diameter slightly smaller than the inner diameter of the sealed pressure vessel 314. In the stirring tank 31 having 313, the mixture was stirred at high speed and a shearing force was applied.
[0106]
This will be described in detail below.
In this example, the high-speed closed stirring process for obtaining a suspension in which the catalyst stable layer material is uniformly dispersed and mixed in a solvent is performed using a high-speed mixer device (TK Filmics 80-50, manufactured by Tokushu Kika Kogyo Co., Ltd.). went. As a result, a highly uniform suspension dispersed to the primary particle size of the catalyst stable layer material or a particle size close to the primary particle size was obtained.
In this example, as in Example 1, ultrafine particle CeO was used.₂And Y₂O_Three(Cai Kasei Co., Ltd.) is used as a mixed solution prepared by uniformly mixing with pure water.
[0107]
As shown in FIGS. 5 and 6, the high-speed mixer device 3 is rotatably attached to a hermetic pressure vessel 314 and a rotary shaft 312 provided inside the hermetic pressure vessel 314, and is slightly larger than the inner diameter of the hermetic pressure vessel 314. It comprises a stirring tank 31 storage tank 32 having a small-diameter rotating blade 313, a pump device 33, and pipes a1 to a4 connecting these.
Further, as shown in FIG. 6, in the high-speed mixer device 3 described above, the inside of the sealed pressure vessel 31 is heated by forming the cooling section 34 on the outer surface of the sealed pressure vessel 314 and flowing the cooling water b1 and b2. Suppressed.
In particular, the high-speed mixer device 3 is intended for mixing, dispersion, and emulsification in a liquid medium. In this example, water is used as the liquid medium, so that it is operated at a boiling point of 100 ° C. or less, preferably about 60 ° C. or less. Drive on.
[0108]
As shown in FIG. 6, the hermetic pressure vessel 314 has a flow path inlet 315 and a flow path outlet 316.
Further, a rotating shaft 312 connected to a high-speed motor 311 is installed in the stirring tank 31, and the rotating shaft 312 is disposed concentrically with the hermetic pressure vessel 314.
A rotating blade 313 having a slightly smaller diameter than the sealed pressure vessel 314 is attached to the rotating shaft 312.
In FIGS. 5 and 6, the space between the rotary blade 313 and the sealed pressure vessel 314 is widely described for easy understanding, but in actuality, it is very narrow as about 2 mm.
[0109]
In the high-speed mixer device 3, the mixed solution circulates between the sealed pressure vessel 314, the storage tank 32, and the pump 33 connected by the flow paths a <b> 1 to a <b> 4.
In the hermetic pressure vessel 314, the mixed liquid rotates upon receiving the energy of the rotary blade 313, is pressed against the inner surface of the hermetic pressure vessel 314 by centrifugal force, increases in pressure, and rotates in the form of a hollow thin film.
[0110]
This rotation of the liquid mixture occurs not only in the portion that contacts the rotary blade 313 but also in the portion that is separated from the rotary blade 313 due to the movement of the liquid mixture rotated by the rotary blade 313, Is present, the rotation is transmitted to the liquid mixture through the rotation of the air.
Since the rotation speed of the rotary blade 313 is larger than the rotation speed of the mixed liquid and the gap between the sealed pressure-resistant vessel 314 and the rotary blade 313 is small, the mixed liquid existing near the end of the rotary blade 313 is all stirred by the rotary blade 313. Actions such as dispersion, mixing, and emulsification occur due to high degree of miniaturization.
[0111]
The liquid mixture inside and outside the rotation surface of the rotary blade 313 is also subjected to actions such as dispersion, mixing, and emulsification due to a speed difference during the rotational movement due to the inertia of the liquid mixture itself, generation of a vortex, and the like.
As described above, the mixed liquid becomes a uniformly dispersed mixed suspension by being dispersed and mixed while circulating between the sealed pressure vessel 314, the storage tank 32, and the pump 33.
Other details of the manufacturing method are the same as those in the first embodiment.
[0112]
In this example, the suspension is prepared using high-speed sealed stirring, so the catalyst stable layer material is prevented from agglomerating in the solvent and secondary particle formation, and these are primary particle size or near primary particle size. Can be dispersed in a state having a particle size of.
Furthermore, the suspension prepared by the high-pressure dispersion mixing process has a stable dispersion state over a long period of time, and re-aggregation of each material in the liquid hardly occurs.
[0113]
The catalyst stabilization layer obtained from the suspension having such characteristics can prevent the catalyst component from diffusing into the ceramic support.
Further, since the catalyst component is difficult to diffuse into the ceramic carrier, the catalyst performance is not deteriorated due to the diffusion of the catalyst component, and the ceramic carrier is hardly deteriorated. it can.
Further, it is possible to use a ceramic support made of cordierite having a low thermal expansion that could not be used on the premise of the diffusion of the catalyst component in the past, and a ceramic catalyst body having a low thermal expansion coefficient can be obtained.
Moreover, even if the ceramic catalyst body is heated to a high temperature, the diffusion of the catalyst component is difficult to promote, so that a ceramic catalyst body that can be used up to the heat resistance limit of each material constituting the ceramic catalyst body can be obtained.
[0114]
Therefore, according to the manufacturing method of this example, the low thermal expansion coefficient and excellent high temperature durability, the catalyst component hardly diffuses into the ceramic carrier, the catalyst performance is hardly deteriorated and the ceramic carrier is hardly deteriorated, and the excellent catalyst performance is maintained for a long time. A ceramic catalyst body that can be maintained over a wide range can be obtained.
Other details are the same as those in the first embodiment.
[0115]
(Example 3)
The ceramic catalyst body of this example includes a ceramic carrier and a catalyst layer that covers the surface of the ceramic carrier and contains a catalyst component.
As shown in FIG. 7A, the ceramic carrier has a honeycomb structure, and has a large number of holes 10 serving as exhaust gas flow paths for causing the catalyst to act, and the catalyst layer 13 has a wall surface 100 facing the gas flow path. To form. FIG. 7B is an explanatory diagram showing a state in which the hole 10 is enlarged. Thus, the catalyst layer 13 including the catalyst component and the catalyst trap material 131 is formed so as to cover the wall surface 100. In FIG. 1B, the vicinity of the hole 10 is further enlarged.
[0116]
The catalyst layer is formed by supporting a catalyst component composed of a main catalyst and a cocatalyst and a catalyst trap material for preventing diffusion of the catalyst component on a coat layer composed of γ-alumina.
The main catalyst is a noble metal catalyst, and the promoter is a NOx storage material. Specifically, the main catalyst is composed of Pt and Rh, and the promoter is a potassium compound (K₂O).
The catalyst trap material is an ultrafine particle (Nanotech ultrafine particle, manufactured by CI Chemical Co., Ltd.) having an average particle diameter of 100 to 300 nm.₂Γ-Al constituting the coating layer₂O_Three10% by weight (outside%) is added.
[0117]
Next, a method for producing the ceramic catalyst body according to this example will be described.
A ceramic carrier was prepared in the same manner as in Example 1, and the catalyst trap material and γ-Al were obtained using the high-pressure dispersion mixing process shown in Example 1.₂O_ThreeWas added to pure water to prepare a suspension. Moreover, the high-speed airtight stirring process shown in Example 2 can also be utilized for producing this suspension.
A ceramic carrier was immersed in the obtained suspension, dried, and then fired to obtain a ceramic catalyst body having a catalyst layer. Other details of the manufacturing method are the same as those in the first embodiment.
[0118]
In the ceramic catalyst body according to this example, the catalyst layer contains a catalyst trap material. Dispersion by high-pressure dispersion mixing treatment prevents aggregation of γ-alumina as a catalyst layer material or catalyst trap material in the solvent and formation of secondary particles, and reduces the primary particle size or the particle size close to the primary particle size. It can be dispersed in the prepared state.
Furthermore, the suspension prepared by the high-pressure dispersion mixing process has a stable dispersion state over a long period of time, and re-aggregation of each material in the liquid hardly occurs.
[0119]
In the catalyst layer obtained from the suspension having such characteristics, the catalyst trap material is uniformly contained in the entire catalyst layer, so that the diffusion of the catalyst component to the ceramic support can be prevented.
In other words, this catalyst trap material sucks the catalyst component supported on the catalyst layer with the surface potential and traps it around the catalyst trap material to prevent diffusion of the catalyst component inside the ceramic carrier at the temperature of use of the ceramic catalyst body. it can. Therefore, the catalyst component can be uniformly dispersed and held in the catalyst layer.
[0120]
Further, since the catalyst component is difficult to diffuse into the ceramic carrier, the catalyst performance is not deteriorated due to the diffusion of the catalyst component, and the ceramic carrier is hardly deteriorated. Therefore, it is possible to obtain a ceramic catalyst body in which the catalyst performance hardly changes for a long time. it can.
Further, it is possible to use a ceramic support made of cordierite having a low thermal expansion that could not be used on the premise of the diffusion of the catalyst component in the past, and a ceramic catalyst body having a low thermal expansion coefficient can be obtained.
Moreover, even if the ceramic catalyst body is heated to a high temperature, the diffusion of the catalyst component is difficult to promote, so that a ceramic catalyst body that can be used up to the heat resistance limit of each material constituting the ceramic catalyst body can be obtained.
[0121]
Therefore, according to the manufacturing method of this example, the low thermal expansion coefficient and excellent high temperature durability, the catalyst component hardly diffuses into the ceramic carrier, the catalyst performance is hardly deteriorated and the ceramic carrier is hardly deteriorated, and the excellent catalyst performance is maintained for a long time. A ceramic catalyst body that can be maintained over a wide range can be obtained.
Other details are the same as those in the first embodiment.
[0122]
In this example, the trap material is contained in the catalyst layer, but a catalyst layer containing the catalyst active material may be provided instead.
In this case, the catalytically active material is CeO of ultrafine particles having an average particle size of 100 to 300 nm (manufactured by CI Kasei Co., Ltd., nanotech ultrafine particles).₂And Al₂O_ThreeΓ-Al that composes the catalyst layer₂O_Three10% by weight (outside%) was added.
[0123]
By supplying hydrogen to the catalyst layer by the steam reforming reaction, the catalyst active material can prevent diffusion of the catalyst component into the ceramic carrier.
Therefore, the diffusion of the catalyst component into the ceramic carrier can be prevented at the use temperature of the ceramic catalyst body. Therefore, the catalyst component can be uniformly dispersed and held in the catalyst layer.
In addition, since the catalyst component is difficult to diffuse and react with the ceramic carrier, problems such as increased thermal expansion of the ceramic carrier are unlikely to occur, and a ceramic catalyst body that is inexpensive, excellent in high-temperature durability, and maintains stable catalyst performance over a long period of time can be obtained. It is done.
Other details are the same as those in the first embodiment.
[0124]
Example 4
The performance of the ceramic catalyst body according to the present invention will be described together with a comparative sample.
The ceramic catalyst bodies according to Samples 1 to 8 and Comparative Samples C1 and C2 have an intermediate layer made of silica on the surface of the ceramic carrier according to Example 1, and CeO on the surface of the intermediate layer.₂And yttria (Y₂O_ThreeAnd a catalyst layer composed of a coating layer of γ-alumina and a catalyst component on the surface thereof.
[0125]
The catalyst component consists of Pt, Rh, Pd of the main catalyst (noble metal catalyst), and the promoter (NOx storage material) is a potassium compound (K₂O). These catalyst components are physically adsorbed on the surface of the coat layer to form a catalyst layer. Further, the surface potential of the catalyst layer and the surface potential of the catalyst stable layer are substantially equal. In the actual use range of the ceramic catalyst body of this example, pH 7 to 10, both are 2 mV at pH 7, -2 mV at pH 8, -7 mV at pH 9, It is -7 mV at pH 10 (see Example 1 for details).
[0126]
The ceramic catalyst bodies according to Samples 1 to 5 were prepared as suspensions for the catalyst stable layer by the high-pressure dispersion mixing process described in Example 1. The equipment used for the high-pressure dispersion mixing treatment was a high-pressure homogenizer (Emulsi Flex® C-5, manufactured by AVESTIN), and the pressure was changed little by little.
The ceramic catalyst bodies according to Samples 6 to 8 are suspensions for the catalyst stable layer using the high-speed mixer device described in Example 2 (TK Filmics 80-50, manufactured by Tokushu Kika Kogyo Co., Ltd.). Was made. The rotating blades (see Example 2) are gradually changed to 30, 40, 50 M / sec (unit: rpm).
[0127]
In addition, Comparative Sample 1 is suspended using propeller stirring and mixing, which is a conventional dispersion method (Comparative Example 1 described later), and Comparative Sample 2 is suspended using a medium stirring mill (Comparative Example 2 described later), which is a conventional dispersion method. A turbid liquid was prepared.
[0128]
Table 1 shows the relationship between the suspension preparation conditions and the state of the obtained suspension when preparing Samples 1 to 8 and Comparative Samples 1 and 2.
In Table 1, the concentration of the suspension is the weight ratio of the dispersed particles to the total suspension weight in weight percent concentration. Then, under the preparation conditions and suspension concentration of each suspension, particles dispersed in the suspension (CeO serving as a catalyst stable layer material)₂And yttria (Y₂O_Three)) Was measured for each concentration by a laser Doppler method using a Microtrac (UPA150, Nikkiso) particle size analyzer.
[0129]
From the above measurement results, it was found that the dispersion using the high-pressure dispersion mixing process and the high-speed hermetic stirring process according to the present invention can obtain a dispersion state with a very fine particle size compared to the conventional dispersion method. .
CeO₂And yttria (Y₂O_Three) The primary particle size is theoretically CeO₂Is 50 nm (0.05 μm), Y₂O_ThreeIs considered to be about 150 nm (0.15 μm), so that it was found that the particles in the suspension by the high-pressure dispersion mixing treatment or the high-speed hermetic stirring treatment are in the state of average primary particles or a state close thereto.
[0130]
[Table 1]

[0131]
Next, durability tests were conducted on the ceramic catalyst bodies of Samples 1 to 8 and Comparative Samples 1 and 2 using exhaust gas from an actual engine. The concentration of the suspension used for preparing each sample was 10%.
The durability test was conducted by introducing exhaust gas at 900 ° C. for 10 hours using an actual engine in a ceramic catalyst body. Then, the NOx occlusion amount and the thermal expansion coefficient in the flow direction of the ceramic catalyst body (described in FIG. 2) were measured and listed in Table 2.
The NOx occlusion amount in Table 2 is described as a ratio with respect to the NOx occlusion amount of the ceramic catalyst body without the catalyst stable layer (after durability) as 1.
The thermal expansion coefficient was evaluated by an average thermal expansion coefficient between 25 ° C. and 800 ° C. by a push rod type thermal dilatometer.
[0132]
As is apparent from Table 2, the comparative sample 1 in which the catalyst stable layer was formed from the suspension obtained by the conventional propeller mixing or medium stirring mill had a thermal expansion coefficient of 1.75 × 10.^-6/ ° C, 1.56 × 10 for comparative sample 2^-6/ C was high.
As a result of analyzing the ceramic support after the endurance test with EPMA (= electron beam microanalyzer), the potassium contained in the NOx occlusion material moves and diffuses in the cordierite structure. It was confirmed that the thermal expansion coefficient was increased by changing the composition of the ceramic support (forming by-products).
[0133]
On the other hand, as shown in Table 2, all of the ceramic catalyst bodies of Samples 1 to 8 have a thermal expansion coefficient of 1.5 × 10 5 in the flow path direction.^-6/ C or below and practically low enough. Further, the NOx occlusion amount (after endurance) was larger than those of Comparative Samples 1 and 2, and it was found that the catalyst performance could be maintained over a long period.
Moreover, as a result of analyzing the dispersion state of the catalyst components of the ceramic catalyst bodies of Samples 1 to 8, particularly the potassium compound, it was confirmed that the potassium compound was almost uniformly dispersed in the catalyst layer in each sample. . This indicates that in the ceramic catalyst bodies of Samples 1 to 8, potassium migration and diffusion are prevented by the catalyst stabilizing layer, and the reaction between cordierite constituting the ceramic carrier and the potassium compound does not occur.
[0134]
[Table 2]

[0135]
(Example 5)
In this example, the same ceramic carrier as in Example 1 is provided with an intermediate layer made of silica, and the intermediate layer is provided with a ceramic layer comprising a coating layer of γ-alumina, a catalyst component, and a catalyst trap material. The performance of the catalyst body was evaluated.
[0136]
The catalyst layer is formed by supporting a catalyst component comprising a main catalyst and a cocatalyst and a catalyst trap material for preventing diffusion of the catalyst component on a coat layer comprising γ-alumina.
The main catalyst is a noble metal catalyst, and the promoter is a NOx storage material. Specifically, the main catalyst is composed of Pt and Rh, and the promoter is a potassium compound (K₂O).
The catalyst trap material is an ultrafine particle (Nanotech ultrafine particle, manufactured by CI Chemical Co., Ltd.) having an average particle diameter of 100 to 300 nm.₂Γ-Al constituting the catalyst layer₂O_Three10% by weight (outside%) was added.
[0137]
Samples 9 to 13 were prepared as suspensions using the high-pressure dispersion mixing process described in Example 1. The equipment used for high-pressure dispersion mixing in each sample was a high-pressure homogenizer, and the pressure was changed little by little.
Samples 14 to 16 were prepared as suspensions using the high-speed hermetic stirring process described in Example 2. In each sample, the peripheral speed of the rotary blade (see Example 2) is changed little by little.
Moreover, the comparative sample 3 produced the suspension which used the screw mixing which is the conventional dispersion method, and the comparative sample 4 produced the suspension using the medium stirring mill.
The details of the preparation of each suspension are the same as in Example 4.
[0138]
Next, the durability test using the exhaust gas discharged from the actual engine was performed on the ceramic catalyst bodies of Samples 9 to 16 and Comparative Samples 3 and 4 in the same manner as in Example 4.
As a result, as is apparent from Table 3, in Comparative Sample 3 in which the catalyst layer was formed from the suspension obtained by the conventional propeller mixing or the medium stirring mill, the thermal expansion coefficient was 1.82 × 10^-6/ ° C, for Comparative Sample 4, 1.65 × 10^-6/ C was high.
[0139]
In addition, as in Comparative Samples 1 and 2 of Example 4, it was confirmed that potassium, which is a NOx occlusion material, moved and diffused in the cordierite structure, and the composition of the ceramic carrier changed (by-products were changed). It was confirmed that the thermal expansion coefficient increased.
[0140]
On the other hand, the ceramic catalyst bodies of Samples 9 to 16 all have a thermal expansion coefficient of 1.5 × 10 5 in the flow path direction.^-6/ C or below and practically low enough. Further, the NOx occlusion amount (after endurance) was larger than those of Comparative Samples 1 and 2, and it was found that the catalyst performance could be maintained over a long period.
Further, in the same manner as Samples 1 to 8 in Example 4, in all the samples, the potassium compound is dispersed almost uniformly in the catalyst layer, and the migration and diffusion of potassium is prevented, and cordierite and potassium constituting the ceramic support. There was no reaction of the compound.
[0141]
[Table 3]

[0142]
(Example 6)
In this example, the same ceramic support as in Example 1 is provided with an intermediate layer made of silica, and the intermediate layer is provided with a ceramic layer comprising a coating layer of γ-alumina, a catalyst component, and a catalyst active material. The performance of the catalyst body was evaluated.
The catalyst layer is formed by supporting a catalyst component composed of a main catalyst and a cocatalyst on a coat layer composed of γ-alumina and a catalyst active material for preventing diffusion of the catalyst component.
[0143]
The main catalyst is a noble metal catalyst, and the promoter is a NOx storage material. Specifically, the main catalyst is composed of Pt and Rh, and the promoter is a potassium compound (K₂O).
The catalytically active material is CeO of ultrafine particles (manufactured by CI Chemical Co., Ltd., nanotech ultrafine particles) having an average particle size of 100 to 300 nm.₂And Al₂O_ThreeΓ-Al that composes the catalyst layer₂O_Three10% by weight (outside%) was added.
[0144]
Samples 17 to 21 were suspensions prepared by the high-pressure dispersion mixing process described in Example 1. The equipment used for high-pressure dispersion mixing in each sample was a high-pressure homogenizer, and the mixing pressure was changed little by little.
Samples 22 to 24 were prepared as suspensions by the high-speed closed stirring process described in Example 2. In each sample, the peripheral speed of the rotary blade (see Example 2) is changed little by little.
Moreover, the comparative sample 5 produced the suspension which used the screw mixing which is a conventional dispersion method, and the comparative sample 6 produced the suspension using the medium stirring mill.
Details are the same as in the fourth embodiment.
[0145]
Next, the endurance test using the exhaust gas from the actual engine was performed on the ceramic catalyst bodies of Samples 17 to 24 and Comparative Samples 5 and 6 in the same manner as in Example 4.
As a result, as is clear from Table 4, in Comparative Sample 5 in which the catalyst layer was formed from the suspension obtained by the conventional propeller mixing or the medium stirring mill, the thermal expansion coefficient was 1.89 × 10^-6/ ° C., 1.62 × 10 6 for the comparative sample 6^-6It was as high as / ° C.
In addition, as in Comparative Samples 1 and 2 of Example 4, it was confirmed that potassium, which is a NOx occlusion material, moved and diffused in the cordierite structure, and the composition of the ceramic carrier changed (by-products were changed). It was confirmed that the thermal expansion coefficient increased.
[0146]
On the other hand, the ceramic catalyst bodies of Samples 17 to 24 all have a thermal expansion coefficient of 1.5 × 10 5 in the flow path direction.^-6/ C or below and practically low enough. Further, the NOx occlusion amount (after endurance) was larger than those of Comparative Samples 1 and 2, and it was found that the catalyst performance could be maintained over a long period.
In each sample, the potassium compound was almost uniformly dispersed in the catalyst layer, the potassium migration and diffusion were prevented, and the reaction between cordierite constituting the ceramic support and the potassium compound did not occur.
[0147]
In Examples 4-6, the movement / diffusion of potassium was examined among the catalyst components. However, the catalyst layer may contain a catalyst component composed of another alkali metal or alkaline earth metal compound. Similar results were obtained.
In addition, as a ceramic carrier, SiC, Si other than cordierite_ThreeN_FourSimilar results were obtained when a honeycomb structure made of mullite material was used.
[0148]
Then, as described in Tables 2 to 4, when a ceramic catalyst body is obtained by preparing a catalyst stable layer or a suspension for the catalyst layer using a propeller mixing or medium stirring mill, the ceramic catalyst body In the presence of water vapor, diffusion of catalyst components such as NOx occlusion material starts from about 600 ° C.
For this reason, in a use environment in which the maximum temperature that is exposed to automobile exhaust gas rises to about 1000 ° C., the catalyst performance deteriorates due to the diffusion of the catalyst component, and the carrier deteriorates due to the reaction between the catalyst component and the ceramic carrier.
[0149]
On the other hand, the ceramic catalyst bodies according to Samples 1 to 24 use a suspension prepared by using a high-pressure dispersion mixing process or a high-speed hermetic stirring process.
Therefore, the catalyst stable layer or catalyst layer formed by applying the catalyst reconstituting layer material or the suspension that is difficult to reaggregate obtained by uniformly dispersing and mixing the catalyst layer material in the solvent to the ceramic carrier in a uniformly dispersed mixed state, Every part has a uniform surface potential and a uniform mixed composition, and the catalyst component diffuses into the ceramic carrier in the presence of high temperature and moisture (generally the moisture content of the exhaust gas is 10 to 20% by weight). Difficult to cause problems such as carrier deterioration.
Thus, the ceramic catalyst body concerning the samples 1-24 described in each Example can be used suitably as a catalyst for automobile exhaust gas purification of a lean burn system or a diesel engine.
[0150]
Furthermore, the ceramic catalyst bodies according to Samples 1 to 24 described in each example can be suitably used for a three-way catalyst of a gasoline engine.
The three-way catalyst of a gasoline engine is required to maintain the purification performance with high activity over a long period of time. By using the ceramic catalyst body according to this example, Pt, Rh, etc. can be obtained from the catalyst active material in the catalyst layer. By supplying hydrogen to the noble metal catalyst (sample 17 to sample 24), the active surface can be increased and a stable catalytic reaction can be maintained over a long period of time.
[0151]
Also, in ceramic filters that collect PM (particulate matter) such as soot discharged from diesel engines, and burn and remove with precious metal catalysts, the catalyst component is catalyst poisoning such as sulfur in exhaust gas Deteriorated under the influence of substances.
By applying samples 17 to 24 here and supplying hydrogen to a noble metal catalyst such as Pt or Rh, removal of the catalyst poisoning substance can be promoted. Therefore, the catalytic poisoning substance does not remain or accumulate on the active surface, and the catalytic reaction can be stably maintained.
[0152]
[Table 4]

[0153]
(Comparative Example 1)
For comparison, a suspension is prepared using propeller stirring and mixing, which is a conventional dispersion method, and a catalyst stable layer and a further catalyst layer are formed from this suspension, and the NOx occlusion reduction is the same as in Example 1. A type ceramic catalyst body was prepared.
In this example, a propeller stirring and mixing device (Aswan Co., Ltd. SM-102) is used to adjust the suspension. The mixing condition by this propeller stirring and mixing apparatus is performed at a rotation speed of 500 rpm. The mixed solution used here was the same as in Example 1 with ultrafine particles CeO.₂And Y₂O_Three(Cai Kasei Co., Ltd.) is used a mixed solution prepared by purely uniform mixing.
[0154]
In the propeller stirring and mixing operation of this example, ultrafine particles CeO are used.₂And Y₂O_ThreeA suspension prepared by uniformly mixing (Cai Kasei Co., Ltd.) with pure water is put into a beaker (1 liter), and the tip of the shaft with a propeller blade attached to the tip of the shaft of the stirring and mixing device is attached to the beaker. Then, mix by rotating the propeller blades. At this time, the rotation speed was controlled so that the suspension of the beaker was not scattered, but the maximum rotation speed was 500 rpm.
[0155]
(Comparative Example 2)
For comparison, a suspension is prepared using a medium stirring mill, which is a conventional dispersion method, and a catalyst stable layer and a further catalyst layer are formed from the suspension, and the NOx occlusion reduction similar to that in Example 1 is performed. A type ceramic catalyst body was prepared.
In this example, a bar stirring device (Ashizawa RV1V, effective capacity 1.0 liter, actual capacity 0.5 liter) is used as the medium stirring mill. The mixing conditions using a bar mill apparatus are as follows: 3.0 kg of a zirconia ball diameter of 0.5 mm is used as a grinding medium, and 80% of the stirring tank volume is filled with zirconia balls.
The mixed solution used here was the same as in Example 1 with ultrafine particles CeO.₂And Y₂O_Three(Cai Kasei Co., Ltd.) is used a mixed solution prepared by purely uniform mixing.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a main part of a ceramic catalyst body in Example 1. FIG.
2 is an overall explanatory view of a ceramic catalyst body in Example 1. FIG.
3 is an explanatory view showing the entire high-pressure dispersion mixing apparatus in Embodiment 1. FIG.
4 is an explanatory diagram showing a configuration of a mixing and dispersing unit according to FIG. 3;
FIG. 5 is an explanatory diagram showing the entire high-speed mixer device according to the second embodiment.
6 is an explanatory view showing a configuration of a sealed pressure vessel according to FIG. 5;
7 is an explanatory view of the main part of a ceramic catalyst body in Example 3. FIG.
[Explanation of symbols]
1. . . Ceramic catalyst body,
10. . . Hole,
11. . . Ceramic carrier,
12 . . Catalyst stable layer,
13. . . Catalyst layer,
2. . . High pressure dispersive mixing equipment,
21. . . High pressure pump,
22. . . Mixing and dispersing section,
23. . . Storage tank,
24. . . Movable orifice,
240. . . tip,
d1, d2. . . Compressed air,
e1-e3. . . Piping,
3. . . High speed mixer equipment,
31. . . Stirring tank,
312. . . Axis of rotation,
313. . . Rotating blades,
314. . . Sealed pressure vessel,
32. . . Storage tank,
a1-a4. . . Piping,

Claims (21)

A ceramic carrier, a catalyst stabilizing layer that covers the surface of the ceramic carrier and suppresses diffusion of the catalyst component, and a catalyst layer that covers the surface of the catalyst stabilizing layer and contains the catalyst component;
In the method for producing a ceramic catalyst body, the surface potential of the catalyst stable layer and the surface potential of the catalyst layer are substantially the same, and the catalyst stable layer has a melting point higher than the highest use temperature.
Prepare the catalyst stable layer material that constitutes the catalyst stable layer,
A suspension in which the catalyst stable layer material is uniformly dispersed and mixed in a solvent is prepared,
In uniformly applying the suspension to the surface of the ceramic carrier and heat-treating the catalyst stable layer material to form the catalyst stable layer,
When preparing the suspension, a mixed liquid containing the catalyst stable layer material and the solvent is prepared, and a collision part is provided in the flow path of the mixed liquid, and the mixed liquid is applied to the collision part under high pressure. A method for producing a ceramic catalyst body, comprising performing a high-pressure dispersion mixing process for uniformly dispersing and mixing a catalyst stable layer material in a solvent by collision. Comprising a ceramic carrier and a catalyst layer covering the surface of the ceramic carrier and containing a catalyst component;
The catalyst layer contains a catalyst trap material capable of suppressing the diffusion of the catalyst component by sucking the catalyst component, and the catalyst trap material has a melting point higher than the maximum use temperature;
Alternatively, the catalyst layer contains a catalyst active material capable of supplying hydrogen to the catalyst component by a steam reforming reaction, and the catalyst active material has a melting point higher than the maximum use temperature in the method for producing a ceramic catalyst body,
Preparing a catalyst layer material constituting the catalyst layer,
Preparing a suspension in which the catalyst layer material is uniformly dispersed and mixed in a solvent;
In applying the suspension uniformly to the surface of the ceramic carrier and heat-treating the catalyst layer material to form the catalyst layer,
When preparing the suspension, a mixed solution containing the catalyst layer material and the solvent is prepared, a collision portion is provided in the flow path of the mixed solution, and the mixed solution collides with the collision portion under high pressure. And a high pressure dispersion mixing process for uniformly dispersing and mixing the catalyst layer material in the solvent. In claim 1 or 2, when the high-pressure dispersion mixing process is performed in a mixing and dispersing section provided to move the movable orifice up and down,
A method for producing a ceramic catalyst body, characterized in that the liquid mixture pumped to the mixing and dispersing section collides with the tip of a movable orifice exposed inside the mixing and dispersing section under high pressure.   The method for producing a ceramic catalyst body according to any one of claims 1 to 3, wherein the high-pressure dispersion mixing treatment is performed at a pressure of 50 to 400 MPa. A ceramic carrier, a catalyst stabilizing layer that covers the surface of the ceramic carrier and suppresses diffusion of the catalyst component, and a catalyst layer that covers the surface of the catalyst stabilizing layer and contains the catalyst component;
In the method for producing a ceramic catalyst body, the surface potential of the catalyst stable layer and the surface potential of the catalyst layer are substantially the same, and the catalyst stable layer has a melting point higher than the highest use temperature.
Prepare the catalyst stable layer material that constitutes the catalyst stable layer,
A suspension in which the catalyst stable layer material is uniformly dispersed and mixed in a solvent is prepared,
In uniformly applying the suspension to the surface of the ceramic carrier and heat-treating the catalyst stable layer material to form the catalyst stable layer,
When preparing the suspension, a mixed solution containing the catalyst stable layer material and the solvent is prepared, and a high-speed sealed stirring process is performed in which the mixed solution is stirred at high speed in a sealed space to apply a shearing force. A method for producing a ceramic catalyst body. 6. The high-speed hermetic stirring process according to claim 5, comprising: a hermetic pressure vessel and a rotary blade that is rotatably attached to a rotary shaft provided inside the hermetic pressure vessel, and has a rotating blade slightly smaller in diameter than the inner diameter of the hermetic pressure vessel. In the stirring tank,
A method for producing a ceramic catalyst body, which is carried out by stirring the mixed solution at a high speed and applying a shearing force.   The method for producing a ceramic catalyst body according to any one of claims 1 to 6, wherein when the suspension is uniformly applied to the surface of the ceramic carrier, ultrasonic waves are applied to the suspension. . The catalyst stable layer according to any one of claims 1 to 3-7 , wherein the catalyst stabilizing layer is composed of Group 1B, Group 2B, Group 3A, Group 3B, Group 4A, Group 5A, Group 6A of the Periodic Table of Elements. A method for producing a ceramic catalyst body, comprising a material containing at least one element selected from elements of Group IV, Group 7A, and Group 8. The catalyst stable layer according to any one of claims 1 to 3 , wherein the catalyst stable layer includes La, Y, Sc, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, Lu, Al, At least selected from Ga, Zn, Cu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt A method for producing a ceramic catalyst body comprising a material containing one or more elements. Claim 1, in any one of 3-9, the catalyst stability _{layer, Y 2 O 3, Sc 2} O 3, TiO, Cr 2 O 3, MnO, Mn 2 O 3, Mn 2 O 5, Fe ₂ O ₃ , Fe ₃ O ₄ , Co ₃ O ₄ , NiO, ZnO, CuO, Ga ₂ O ₃ , ZrO ₂ , Zr ₂ O ₃ , Nb ₂ O ₅ , SnO ₂ , CeO ₂ , Pr ₂ O ₃ , PrO ₄ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O _{3. A} method for producing a ceramic catalyst body, comprising at least one material selected from ₃ , Lu ₂ O ₃ , HfO ₂ , Ta ₂ O ₅ , and Al ₂ O ₃ . The method for producing a ceramic catalyst body according to any one of claims 1 and 3 to 10 , wherein the catalyst stable layer includes at least one of Y ₂ O ₃ and CeO ₂ . The method for producing a ceramic catalyst body according to any one of claims 2 to 4, wherein the catalyst trap material is made of powder having an average primary particle diameter of 500 nm or less. 13. The catalyst trap material according to claim 2, wherein the catalyst trap material is Y ₂ O ₃ , Sc ₂ O ₃ , NiO, ZnO, CuO, CeO ₂ , Pr ₂ O ₃ , PrO ₄ , Nd ₂ O. ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O _A method for producing a ceramic catalyst body, comprising at least one material selected from ₃ and Al ₂ O ₃ . The method for producing a ceramic catalyst body according to any one of claims 2 to 4, wherein the catalytically active material is made of a material containing at least one element selected from lanthanoid elements. 15. The catalyst active material according to claim 2, wherein the catalyst active material is Y ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , PrO ₄ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O _3. From one or more materials selected from Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ A method for producing a ceramic catalyst body. 16. The ceramic catalyst body according to any one of claims 2 to 4, 14, and 15, wherein the catalytically active material is made of at least one material selected from at least a Ce oxide or a composite oxide. Manufacturing method. In the claims 2-4, any one of 14 to 16, the catalyst activity material, and _{CeO 2, Y 2 O 3,} 1 or more oxide selected from TiO _2, ZrO ₂ and Al ₂ O ₃ A method for producing a ceramic catalyst body comprising a mixed oxide obtained by mixing a product.   18. The ceramic catalyst body according to claim 1, wherein the catalyst component includes a compound composed of at least one element selected from an alkali metal element and an alkaline earth metal element. Production method.   19. The catalyst component according to claim 1, wherein the catalyst component includes a compound composed of at least one element selected from Li, Na, K, Ba, Rb, Be, Mg, Ca, and Sr. A method for producing a ceramic catalyst body. The method for producing a ceramic catalyst body according to any one of claims 1 to 19, wherein the ceramic carrier has a thermal expansion coefficient of 1.5 x 10 ⁴ / ° C or less.   21. The method for producing a ceramic catalyst body according to any one of claims 1 to 20, wherein the ceramic carrier contains cordierite.

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