Exhaust Gas Purifying Catalyst with ZrCe Oxide Gradient
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Solution Overview
Problem
Conventional exhaust gas purifying catalysts struggle to meet stricter regulations for removing HC, CO, and NOx, particularly during the warm-up phase of internal combustion engines and over long operation periods, due to inadequate warm-up performance and durability.
Innovation Solution
An exhaust gas purifying catalyst with a substrate having through holes and a catalyst coating layer containing precious metals and Zr or Ce oxides, where the oxide equivalent weight of Zr in one area is 51-100 wt% and Ce in another area is 58-100 wt%, optimizing the distribution to enhance HC and NOx removal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalysts are used, then basic exhaust gas purification is achieved, but warm-up performance is insufficient
Solution Approach 1:
The catalyst coating layer is divided into upstream and downstream regions with different Zr/Ce oxide compositions. The upstream region contains Zr oxide with 51-100 wt% Zr equivalent weight to stabilize precious metals during cold start, while the downstream region contains Ce oxide with 58-100 wt% Ce equivalent weight for optimal NOx storage and reduction during warm operation. This spatial differentiation of material properties resolves the contradiction between warm-up performance and overall purification efficiency.
Solution Approach 2:
The invention changes the compositional parameters of the catalyst coating by controlling the oxide equivalent weights of Zr and Ce in different regions. By adjusting these parameters within specific ranges (Zr: 51-100 wt%, Ce: 58-100 wt%), the catalyst achieves optimized performance for both cold start and warm operation conditions, resolving the performance trade-off.
2Duration of action of stationary object
If conventional catalysts are used, then initial purification function is provided, but durability over long operation is insufficient
Solution Approach 1:
The downstream region of the catalyst coating is specifically designed with Ce oxide content (58-100 wt% Ce equivalent weight) optimized for NOx storage and reduction during sustained operation. This local composition ensures stable purification performance over long durability periods, addressing the contradiction between initial function and long-term reliability.
3Reliability
If uniform catalyst coating is applied, then simple manufacturing is achieved, but optimized performance in different flow areas is lost
Solution Approach 1:
The catalyst coating structure is deliberately made non-uniform with distinct upstream and downstream regions having different oxide compositions. This spatial variation in material quality optimizes HC removal in the upstream region and NOx removal in the downstream region, achieving superior overall performance despite increased structural complexity.
Solution Approach 2:
The catalyst coating is segmented into functionally distinct upstream and downstream regions along the exhaust gas flow direction. Each segment is tailored with specific oxide compositions (Zr-rich upstream, Ce-rich downstream) to handle different purification requirements, resolving the contradiction between performance optimization and structural simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst achieves improved warm-up performance by stabilizing precious metals and ensuring effective HC removal immediately after engine start-up, and maintains durability by securing NOx and CO removal performance over extended engine operation.
Implementation Method 1
one of or a combination of catalytic components, such as Pt, Pd and Rh, is dispersed in and carried by a refractory inorganic compound powder, such as alumina and ceria-zirconia
Implementation Method 2
three-way catalysts that purify HC, CO, and NOx at the same time
Implementation Method 3
a reduced OSC performance (oxide storage performance)
Data Source
AI summary
An exhaust gas purifying catalyst comprises a substrate having a through hole serving as a passage for exhaust gas; and a catalyst coating layer formed on an internal surface of the through hole. The catalyst coating layer contains: a component (i): a precious metal; and a component (ii): at least one of a Zr oxide, a Ce oxide and a ZrCe mixed oxide. On an upstream portion of the passage, an oxide equivalent weight of Zr is within a range of 51-100 wt % of an oxide equivalent weight of Zr and Ce contained in the component (ii). On a downstream portion of the passage, the component (ii) includes at least one of a Ce oxide and a ZrCe mixed oxide in which an oxide equivalent weight of Ce is within a range of 58-100 wt % of an oxide equivalent weight of Zr and Ce contained in the ZrCe mixed oxide.