Pd-Ceria Catalyst on Composite Oxide Support for Exhaust Purification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing catalysts for exhaust gas purification fail to maintain sufficient catalytic activity at low temperatures and oxygen storage/release performance after exposure to high temperatures, as hydrocarbons are adsorbed and poison the surface of Pd, leading to inadequate catalytic activity and reduced oxygen storage capacity.
Innovation Solution
A catalyst is developed where ceria nanoparticles are supported on a composite metal oxide support containing alumina and zirconia, with Pd-containing nanoparticles dispersed and supported in proximity to ceria, achieving a specific molar ratio and distribution to enhance catalytic activity and oxygen storage/release performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Pd is supported on metal oxide support for exhaust gas purification, then catalytic activity for oxidizing CO and HC is improved, but hydrocarbons are adsorbed and poison the Pd surface at low temperatures, reducing catalytic activity
Solution Approach 1:
Ceria nanoparticles are introduced as an intermediary substance between Pd and the exhaust gas. The ceria absorbs hydrocarbons through its oxygen storage capacity, preventing them from poisoning the Pd surface. This mediator approach allows Pd to maintain its catalytic function while ceria handles the harmful hydrocarbon adsorption, resolving the contradiction between catalytic activity and hydrocarbon poisoning.
Solution Approach 2:
The oxygen storage capacity parameter of the support material is changed by using ceria nanoparticles with specific oxygen storage/release properties. This parameter change enables the support to dynamically adjust oxygen availability, preventing hydrocarbon accumulation on Pd surface at low temperatures while maintaining catalytic activity. The oxygen storage capacity acts as a controllable parameter that resolves the poisoning issue.
2Quantity of substance
If ceria is used as oxygen storage material to improve oxygen storage/release performance, then oxygen storage capacity is improved, but oxygen storage/release performance deteriorates after exposure to high temperatures
Solution Approach 1:
A composite material system is created by combining ceria nanoparticles with a composite metal oxide support containing alumina and zirconia. This composite structure provides thermal stability to the ceria, preventing sintering and maintaining oxygen storage/release performance after high-temperature exposure. The zirconia component specifically contributes to thermal stability, while alumina provides structural support, together preserving the oxygen storage capacity under harsh conditions.
Solution Approach 2:
The support structure is designed with local quality differentiation where ceria nanoparticles are dispersed on specific regions of the composite metal oxide support. The alumina and zirconia components provide localized thermal stability and structural integrity in high-temperature zones, while ceria maintains its oxygen storage function in accessible regions. This spatial differentiation of properties ensures both oxygen storage capacity and high-temperature reliability.
3Power
If Pd particles are dispersed on support to maintain catalytic activity, then catalytic activity is improved, but Pd particles aggregate at high temperatures, reducing catalytic activity
Solution Approach 1:
The composite metal oxide support with alumina and zirconia provides a porous structure with high surface area and thermal stability. This porous matrix physically confines Pd particles, preventing their aggregation at high temperatures while maintaining good dispersion. The porous structure allows adequate space for Pd particles to remain dispersed without direct contact, thus preserving catalytic activity under thermal stress conditions.
Solution Approach 2:
The support structure is pre-designed with specific porous characteristics and surface properties before Pd deposition. This preliminary preparation of the support ensures that Pd particles are uniformly dispersed and anchored in stable positions from the beginning, preventing subsequent aggregation during high-temperature operation. The pre-engineered support structure proactively prevents the aggregation problem rather than reacting to it.
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 exhibits excellent catalytic activity at low temperatures and maintains superior oxygen storage/release performance after high-temperature exposure, preventing hydrocarbon poisoning and ensuring effective purification of exhaust gases.
Implementation Method 1
a material having an oxygen storage capacity (CSC) that can store oxygen when the oxygen concentration in the exhaust gas is high and release oxygen when the oxygen concentration in the exhaust gas is low
Implementation Method 2
oxidize carbon monoxide (CO) and hydrocarbon (HC) and reduce nitrogen oxides (NOx)
Implementation Method 3
a catalyst for purification of exhaust gas in which Pd-based nanoparticles composed of Pd or Pd oxide
Implementation Method 4
CeZr-based composite metal oxide particles having oxygen storage/release performance
Implementation Method 5
hydrocarbons (HC) are adsorbed and poisoned on the surface of Pd
Data Source
AI summary
A catalyst for purification of exhaust gas in which Pd-based nanoparticles and ceria nanoparticles are supported on a composite metal oxide support containing alumina, ceria, and zirconia, wherein a molar ratio (Ce/Pd) of Ce and Pd supported on the support is 1 to 8, a proximity α between Pd and Ce is 0.15 to 0.50, wherein the proximity α is determined, based on Pd and Ce distribution maps in an element mapping image of energy dispersive X-ray analysis, by the following formula (1):α=∑ j=0N-1∑ i=0M-1((I(i,j)-Iave)(T(i,j)-Tave))∑ j=0N-1∑ i=0M-1(I(i,j)-Iave)2-∑ j=0N-1∑ i=0M-1(T(i,j)-Tave)2,(1)a Pd dispersity after a heat-resistance test at 1050° C. for 25 hours is 0.8% or more.