Exhaust Catalyst Phosphorus Poisoning Mitigation
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Solution Overview
Problem
Existing catalysts for exhaust gas purification from internal combustion engines face challenges in maintaining performance over long periods due to phosphorus poisoning, which leads to deterioration in catalytic activity, especially when exposed to high temperatures and phosphorus compounds.
Innovation Solution
A catalyst configuration with a lower noble metal layer and upper layers having different noble metal concentrations, including an intermediate zone with varying rhodium and palladium concentrations, is used to mitigate phosphorus poisoning effects, ensuring sustained performance for CO, HC, and NOx purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst is exposed to exhaust gas containing phosphorus compounds at high temperature for long time, then the catalytic performance deteriorates due to phosphorus poisoning, but the demand requires maintaining high purification performance over long service life
Solution Approach 1:
The catalyst is divided into multiple layers with different compositions and functions. The first catalyst layer (containing Pd and Pt) serves as a phosphorus capture zone, while the second catalyst layer (containing Rh) maintains high purification performance. This segmentation protects the Rh layer from phosphorus poisoning while ensuring long service life.
Solution Approach 2:
The first catalyst layer acts as an intermediary between the exhaust gas and the second catalyst layer. It captures phosphorus compounds from the exhaust gas, preventing them from reaching and poisoning the Rh-based second catalyst layer, thus protecting the main catalytic function.
2Reliability
If a single-layer catalyst structure is used, then the device complexity is low, but the catalytic performance deteriorates rapidly under phosphorus poisoning conditions
Solution Approach 1:
The catalyst is divided into multiple layers with different compositions and functions. The first catalyst layer (containing Pd and Pt) serves as a phosphorus capture zone, while the second catalyst layer (containing Rh) maintains high purification performance. This segmentation protects the Rh layer from phosphorus poisoning while ensuring long service life.
Solution Approach 2:
Different regions of the catalyst have different compositions tailored to their specific functions. The first layer has high Pd and Pt content for phosphorus capture, while the second layer has Rh for high-activity purification. This local differentiation optimizes performance while managing complexity.
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 maintains high purification efficiency for carbon monoxide, hydrocarbons, and nitrogen oxides even after prolonged exposure to phosphorus compounds at high temperatures, enhancing the durability and longevity of exhaust gas purification performance.
Implementation Method 1
a first catalyst layer containing Pd and/or Pt; and a second catalyst layer containing Rh provided on a surface of the first catalyst layer
Implementation Method 2
Diffusional inhibition of the exhaust gas in the catalyst layer is caused by the phosphorus compound being deposited or penetrated into the catalyst layer
Implementation Method 3
cerium oxide of an oxygen-storage-release material (oxygen storage material) that is widely used in a three-way catalyst and a phosphorus compound react with each other to form cerium phosphate
Data Source
AI summary
A catalyst for purification of exhaust gas containing a phosphorus compound includes: a lower catalyst layer containing at least one of noble metal provided on a refractory three-dimensional structure; and an upper catalyst layer at an inflow side of exhaust gas and an upper catalyst layer at an outflow side of exhaust gas provided on a surface of the lower catalyst layer. The upper catalyst layer at the inflow side and the upper catalyst layer at the outflow side have different concentrations of noble metal. The catalyst has an intermediate zone with a length of 3 to 23% of the overall length of the refractory three-dimensional structure provided between the upper catalyst layer at the inflow side and the upper catalyst layer at the outflow side. The intermediate zone starts from a position 10 to 38% from an end face of the catalyst at the inflow side of exhaust gas.