Exhaust Catalyst Segmentation for NOx and Oxidation Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing catalysts for exhaust gas purification face challenges in maintaining the catalytic performance of palladium and rhodium due to the adverse effects of alkaline earth metals, particularly at high temperatures, which can lead to reduced NOx purification capacity and oxidation performance.
Innovation Solution
A catalyst comprising a catalytically active component with palladium and barium supported on a refractory inorganic oxide at an optimal ratio, combined with another component having platinum and/or rhodium supported on a refractory inorganic oxide, is used to enhance exhaust gas purification performance while maintaining NOx purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an alkaline earth metal is added to enhance palladium's catalytic action, then oxidation performance is improved, but NOx purification capacity by rhodium is lowered
Solution Approach 1:
The catalyst is divided into multiple functional layers: a first catalyst layer containing palladium and alkaline earth metal for oxidation reactions, and a second catalyst layer containing rhodium for NOx purification. This segmentation allows each metal to operate in its optimal environment without mutual interference, resolving the contradiction between enhancing oxidation performance and maintaining NOx purification capacity
Solution Approach 2:
Different regions of the catalyst have different compositions optimized for specific functions. The first catalyst layer has high palladium and alkaline earth metal content for oxidation, while the second catalyst layer has high rhodium content for NOx purification. This local quality differentiation allows each component to excel at its designated task without being poisoned by other components
2Reliability
If rhodium is used in high amounts to maximize NOx purification capacity, then NOx purification performance is improved, but catalyst cost increases significantly
Solution Approach 1:
The catalyst is segmented into layers with different precious metal concentrations. The second catalyst layer contains high rhodium content for effective NOx purification, while the first catalyst layer contains minimal or no rhodium, using instead palladium and alkaline earth metals for oxidation functions. This segmentation concentrates rhodium only where it is most needed, reducing overall rhodium usage while maintaining high NOx purification capacity
Solution Approach 2:
Palladium and alkaline earth metals in the first catalyst layer perform multiple functions: they provide oxidation activity for CO and HC conversion, and also serve as a cost-effective alternative to rhodium for some purification functions. This multi-functionality reduces dependence on expensive rhodium while maintaining overall catalyst performance
3Device complexity
If a single catalyst layer containing all precious metals is used, then device complexity is reduced, but catalytic performance under varying exhaust conditions deteriorates
Solution Approach 1:
The catalyst is segmented into multiple layers, each optimized for specific exhaust gas composition ranges. The first catalyst layer with palladium and alkaline earth metal excels in rich conditions for oxidation, while the second catalyst layer with rhodium excels in lean conditions for NOx purification. This segmentation allows the catalyst to adapt to varying exhaust conditions more effectively than a single-layer design
Solution Approach 2:
Each catalyst layer has a locally optimized composition tailored to specific operating conditions. The first layer has high palladium and alkaline earth metal content optimized for oxidation in rich exhaust, while the second layer has high rhodium content optimized for NOx purification in lean exhaust. This local quality optimization enables the catalyst to maintain high performance across a broader range of operating conditions
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
This configuration effectively suppresses the adverse effects of alkaline earth metals, enhancing both the ignition and NOx purification performance of the catalyst, particularly under rich conditions, and maintains the catalytic activity of rhodium, thereby improving overall exhaust gas purification efficiency.
Implementation Method 1
a catalytically active component (I) having palladium and barium supported on a refractory inorganic oxide (A)
Implementation Method 2
enhancing both the ignition and NOx purification performance of the catalyst
Implementation Method 3
a catalytically active component (II) having at least either of rhodium and platinum on a refractory inorganic oxide (B)
Implementation Method 4
NOx purification capacity
Data Source
AI summary
It is an object of the present invention to provide a catalyst for the exhaust gas purification having excellent ignition performance and NOx purification performance. The present invention provides a catalyst for the exhaust gas purification which comprises a catalytically active component (I) having palladium and barium supported on a refractory inorganic oxide (A); and a catalytically active component (II) having at least either of rhodium and platinum on a refractory inorganic oxide (B), a method for the production thereof, and a method for purifying an exhaust gas using such a catalyst.