Three-Way Catalyst Pore Structure Suppresses Sintering
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Solution Overview
Problem
Existing exhaust gas-purifying three-way catalysts face issues with particle growth due to sintering at high temperatures, leading to rapid deterioration in catalyst performance, especially in gasoline engines with higher exhaust gas temperatures, and require heat treatment at high temperatures for specific crystal structures, which is inefficient.
Innovation Solution
A composite particle structure is developed where a platinum group element catalytically active particle is supported on a base material particle with a large pore size of 100 to 650 nm, using a ceria-based or zirconia-based oxygen storage material, to prevent sintering and enhance heat resistance, with a content proportion of 0.001 to 30% by mass of the catalytically active particle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalytically active component is used in fine particle form supported on a carrier, then catalytic activity is enhanced and PGM amount is reduced, but particle sintering occurs at high temperature causing particle growth and remarkable decrease in catalytically active sites
Solution Approach 1:
The patent employs a carrier with controlled pore size (100-650 nm) and pore volume (0.3-2.0 mL/g) to support the catalytically active component. The porous structure provides a large surface area for dispersion while the specific pore dimensions prevent particle sintering by constraining the movement and aggregation of fine particles at high temperatures, thus maintaining both high catalytic activity and particle size stability.
Solution Approach 2:
The patent uses a composite carrier structure combining metal oxide (alumina, zirconia, or ceria) with controlled pore characteristics. This composite approach integrates the high surface area of fine particles with the thermal stability of the metal oxide matrix, enabling the catalytically active component to maintain dispersion and activity even under high-temperature conditions that would normally cause sintering.
2Quantity of substance
If Al2O3 is used as a base material particle for diesel engine catalysts, then oxygen storage capacity is achieved, but heat resistance is insufficient and catalyst performance rapidly deteriorates in gasoline engines with higher exhaust gas temperatures
Solution Approach 1:
The patent modifies the physical parameters of the base material by controlling pore size (100-650 nm) and pore volume (0.3-2.0 mL/g) rather than changing the chemical composition fundamentally. This parameter optimization allows the same metal oxide materials to exhibit improved thermal stability and heat resistance, enabling their use in gasoline engines with higher exhaust temperatures while retaining oxygen storage capacity.
Solution Approach 2:
The patent applies different material compositions and pore structure characteristics to different regions of the catalyst system. The carrier is designed with specific local pore properties (size and volume distribution) that provide both oxygen storage functionality and heat resistance, while the catalytically active component is distributed throughout this optimized pore network to maintain activity under high-temperature conditions.
3Temperature
If heat treatment at 800 to 1100°C for several tens of hours is applied to obtain a solid solution crystal structure, then heat resistance is enhanced, but productivity decreases due to the lengthy and complex process
Solution Approach 1:
The patent performs preliminary preparation of the carrier with optimized pore size (100-650 nm) and pore volume (0.3-2.0 mL/g) before the final heat treatment step. This preliminary structuring allows the subsequent heat treatment to be more effective and shorter in duration, as the pre-formed pore network provides a template that guides crystal structure formation without requiring extended treatment times to achieve the desired solid solution structure.
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 significantly suppresses particle growth and maintains high purification performance, reducing NOx, CO, and HC emissions, and can be used in various engine types with improved heat resistance and reduced production costs.
Implementation Method 1
a catalytically active particle of a platinum group element is supported on a base material particle... Three-way catalysts (TWC) with platinum group elements (PGM: Platinum Group Metals) such as ruthenium, rhodium, palladium, osmium, iridium, and platinum as catalytically active components are widely used in purification of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx)
Implementation Method 2
a composite particle which comprises a base material particle having a pore size of 100 to 650 nm as measured by a mercury intrusion method and a catalytically active particle of a platinum group element supported on the base material particle... significantly suppresses particle growth
Data Source
AI summary
Provided is, for example, an exhaust gas-purifying three-way catalyst which is suppressed in particle growth due to sintering of a catalytically active component on a carrier in exposure to a high temperature and thus is enhanced in purification performance, and a method for producing the same, as well as an integral structure type exhaust gas-purifying catalyst using the same.The exhaust gas-purifying three-way catalyst of the present invention includes a composite particle which contains a base material particle having a pore size of 100 to 650 nm as measured by a mercury intrusion method and a catalytically active particle of a platinum group element supported on the base material particle, in which a content proportion of the catalytically active particle is 0.001 to 30% by mass in total in terms of metal of the platinum group element, based on a total amount of the composite particle.