Exhaust Catalyst Pore Volume Distribution for Light-Off
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Solution Overview
Problem
Conventional exhaust gas purification catalysts exhibit poor light-off temperature characteristics, failing to efficiently convert pollutants at engine start-up due to inadequate pore volume distribution, particularly in the range of 5-25 nm.
Innovation Solution
A porous structure with a specific pore volume distribution ratio of 1.4 to 2.5 for pores between 15-25 nm to those between 5-15 nm, optimized by mercury porosimetry, enhances contact between exhaust gases and catalyst active components, improving light-off temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the catalyst layer is designed with conventional pore volume control, then the noble metal contact probability is improved, but the light-off temperature characteristics remain insufficient
Solution Approach 1:
The invention changes the pore volume distribution parameters specifically in the 5-25 nm diameter range, optimizing the ratio between different pore size ranges to achieve both improved noble metal contact probability and enhanced light-off temperature characteristics
Solution Approach 2:
The invention applies different pore volume characteristics to different pore size ranges within the catalyst layer, creating localized optimal conditions for both noble metal contact and low-temperature catalytic activity
2Measurement precision
If the pore volume of fine pores (5-15 nm) is increased to improve noble metal contact, then the contact probability is enhanced, but the light-off temperature characteristics deteriorate
Solution Approach 1:
The invention optimizes the ratio parameter between different pore size ranges (15-25 nm to 5-15 nm) to fall within 1.3 to 2.5, balancing the competing requirements of noble metal contact probability and light-off temperature characteristics
Solution Approach 2:
The catalyst layer comprises a composite porous structure with multiple pore size ranges (5-15 nm and 15-25 nm) working synergistically, where each pore size range contributes differently to overall catalyst performance
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 optimized pore volume distribution significantly enhances the light-off temperature characteristics, enabling efficient conversion of NOx, HC, and CO at engine start-up, as demonstrated by lower T50 values in the catalysts tested.
Implementation Method 1
enhances contact between exhaust gases and catalyst active components
Data Source
AI summary
Provided is a porous structure for exhaust purification catalysts having excellent light-off temperature characteristics. The porous structure for exhaust purification catalysts includes an oxygen storage component and an inorganic porous solid. The porous structure has a pore volume distribution such that the ratio of the pore volume of pores with a diameter of from 15 nm to less than 25 nm to the pore volume of pores with a diameter of from 5 nm to less than 15 nm is 1.3 to 2.5 as measured with a mercury porosimeter. The pore volume distribution preferably has at least one peak top in a pore diameter range of from 15 nm to less than 25 nm.