CN-117098602-B - Catalyst composition for exhaust gas purification and catalyst for exhaust gas purification

Abstract

An object of the present invention is to provide an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst having improved exhaust gas purifying performance, wherein the exhaust gas purifying catalyst composition comprises Ce-based oxide particles, ce-Zr-based composite oxide particles, al-based oxide particles, and a noble metal element, wherein the Ce-based oxide particles have a CeO 2 conversion amount of 90 mass% or more in the Ce-based oxide particles, the Ce-Zr-based composite oxide particles have a CeO 2 conversion amount of 5 mass% or more and 90 mass% or less in the Ce-Zr-based composite oxide particles, the Ce-based composite oxide particles have an average particle diameter of 0.10 [ mu ] m or more and 15 [ mu ] m or less in the exhaust gas purifying catalyst composition, and the Ce-based oxide particles have a CeO 2 conversion amount of 2.0 mass% or more and 30 mass% or less in the exhaust gas purifying catalyst composition.

Inventors

• TANAKA HIROYASU
• MORITA Itaru
• Tail has uncommon forever
• MUTOH TSUTOMU

Assignees

• 三井金属矿业株式会社

Dates

Publication Date

20260512

Application Date

20220301

Priority Date

20210330

Claims (6)

1. 1. A catalyst composition for purifying exhaust gas, which comprises Ce-based oxide particles, ce-Zr-based composite oxide particles, al-based oxide particles and a noble metal element, The CeO 2 conversion amount of Ce in the Ce-based oxide particles is 90 mass% or more based on the mass of the Ce-based oxide particles, The CeO 2 conversion amount of Ce in the Ce-Zr composite oxide particles is 5 to 90 mass% based on the mass of the Ce-Zr composite oxide particles, The Ce-based oxide particles have an average particle diameter of 1.0 μm or more and 15 μm or less, The Ce-based oxide particles in the exhaust gas-purifying catalyst composition are present in an amount of 2.0 mass% or more and 30 mass% or less, based on the mass of the exhaust gas-purifying catalyst composition.
2. 2. The exhaust gas purifying catalyst composition according to claim 1, wherein a ZrO 2 conversion amount of Zr in the Ce-Zr-based composite oxide particles is 10 mass% or more and 95 mass% or less based on the mass of the Ce-Zr-based composite oxide particles.
3. 3. The exhaust gas-purifying catalyst composition according to claim 1 or 2, wherein the noble metal element is supported on the Ce-based oxide particles, the Ce-Zr-based composite oxide particles, and the Al-based oxide particles.
4. 4. The catalyst composition for exhaust gas purification according to claim 1 or 2, wherein the noble metal element is selected from Rh and Pt.
5. 5. The exhaust gas-purifying catalyst composition according to claim 1 or 2, wherein the CeO 2 in the Ce-based oxide particles has a crystallite diameter of 10nm or more.
6. 6. A catalyst for purifying exhaust gas, comprising a base material and a catalyst layer provided on the base material, The catalyst layer is composed of the exhaust gas-purifying catalyst composition according to any one of claims 1 to 5.

Description

Catalyst composition for exhaust gas purification and catalyst for exhaust gas purification Technical Field The present invention relates to an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst. Background Exhaust gas from internal combustion engines of automobiles, motorcycles, and the like contains harmful components such as hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NO x). As an exhaust gas purifying catalyst for purifying and rendering harmless these harmful components, a three-way catalyst is used, which has catalytic activity for oxidizing THC into water and carbon dioxide, oxidizing CO into carbon dioxide, and reducing NOx into nitrogen. In an exhaust gas purifying catalyst such as a three-way catalyst, an Al oxide such as alumina (Al 2O3) or a ce—zr composite oxide is used as a carrier for supporting a catalytically active component (for example, noble metal particles such as Pt, pd, rh, etc. (for example, patent documents 1 and 2). In the present specification, the term "Al-based oxide" refers to an Al-containing oxide in which the amount of Al 2O3 calculated as Al is 70 mass% or more based on the mass of the oxide, and the term "ce—zr-based composite oxide" refers to a composite oxide containing Ce and Zr in which the amount of CeO 2 calculated as Ce is 5 mass% or more and 90 mass% or less based on the mass of the composite oxide. The Ce-Zr based composite oxide is a material (OSC material) having an oxygen storage capacity (OSC: oxygen Storage Capacity) and can slow down the fluctuation of the oxygen concentration in exhaust gas to expand the operating window of the catalyst. As the OSC material, ce-based oxides such as cerium oxide (CeO 2) may be used (for example, patent document 2). However, ceO 2 is generally not used as a carrier for supporting the catalytic active components of the three-way catalyst because of its low oxygen storage capacity. In the present specification, the term "Ce-based oxide" refers to an oxide containing Ce in which the amount of CeO 2 converted to Ce is 90 mass% or more based on the mass of the oxide. Prior art literature Patent literature Patent document 1 Japanese patent laid-open publication No. 2017-039069 Patent document 2 Japanese patent laid-open No. 2006-297372 Disclosure of Invention Problems to be solved by the invention The Ce-based oxide has high affinity for the catalytically active component (e.g., noble metal particles such as Pt, pd, rh, etc.), but has low heat resistance. On the other hand, although Al-based oxides and ce—zr-based composite oxides have high heat resistance, they have low affinity for catalytically active components (e.g., noble metal particles such as Pt, pd, rh, etc.). Therefore, by using a Ce-based oxide, a Ce-Zr-based composite oxide, and an Al-based oxide in combination as a carrier for supporting a catalytic active ingredient, the weak points of the Ce-based oxide can be made up by the Ce-Zr-based composite oxide and the Al-based oxide, and the weak points of the Ce-Zr-based composite oxide and the Al-based oxide can be made up by the Ce-based oxide. However, even if the Ce-based oxide, the ce—zr-based composite oxide, and the Al-based oxide are used in combination, there are cases where the exhaust gas purifying performance is degraded. For example, when CeO 2 is used as a carrier for supporting a catalytic active ingredient, ceO 2 may be aggregated with each other due to low heat resistance of CeO 2, small pores of CeO 2 may disappear (i.e., the specific surface area may be reduced), and thus the catalytic active ingredient may be buried, resulting in a reduction in exhaust gas purification performance. Since the aggregation of ceos 2 with each other and the decrease in specific surface area of CeO 2 easily occur in a high-temperature environment, the decrease in exhaust gas purification performance easily occurs after exposure to the high-temperature environment. In the present specification, "high temperature" means a temperature of, for example, 800 ℃ or higher, particularly 900 ℃ or higher. The present invention is directed to an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst using a Ce-based oxide, a Ce-Zr-based composite oxide, and an Al-based oxide, which improve the exhaust gas purifying performance (particularly, the exhaust gas purifying performance after exposure to a high-temperature environment). Solution for solving the problem The inventors of the present invention have found that the exhaust gas purifying performance (particularly, the exhaust gas purifying performance after exposure to a high-temperature environment) can be improved by adjusting the average particle diameter and the content of Ce-based oxide in an exhaust gas purifying catalyst composition and an exhaust gas purifying catalyst using Ce-based oxide, ce—zr-based composite oxide, and Al-based oxide. The present invention has been completed based on the above kno