Rh-Pt Catalyst Composition for Gasoline Exhaust Emissions Control

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Solution Overview

Problem

Three-way catalysts (TWCs) used in gasoline engines face challenges with Rh deactivation during lean conditions, leading to reduced performance and increased costs due to high precious metal prices, necessitating a cost-effective solution to maintain emissions control while reducing Rh loading.

Innovation Solution

A catalyst composition with a platinum group metal (PGM) component comprising rhodium (Rh) and platinum (Pt) in a weight ratio of at least 1:10, supported on a PGM support material, such as ceria-zirconia mixed oxide, to enhance Rh stability and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If Rh loading is reduced to lower costs, then cost-effectiveness is improved, but Rh deactivation during lean conditions worsens

Engineering Contradiction:

Improvecost-effectivenessVSAvoidRh stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Pt acts as an intermediary element that modifies the chemical environment around Rh, preventing Rh deactivation during lean conditions. The Pt-Rh interaction creates a protective effect that maintains Rh activity without requiring higher Rh loadings, thus resolving the contradiction between cost-effectiveness and Rh stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The catalyst uses a composite PGM component containing both Pt and Rh in a weight ratio of at least 1:10. This composite structure leverages the synergistic interaction between Pt and Rh, where Pt enhances Rh stability during lean conditions while maintaining overall catalytic performance, enabling cost-effective formulations with reduced Rh content

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If Pt is introduced to replace Rh, then cost is reduced, but catalyst performance may deteriorate

Engineering Contradiction:

Improvecost reductionVSAvoidcatalyst performance

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The invention optimizes the Pt:Rh weight ratio parameter (at least 1:10) to achieve the right balance between cost reduction and performance maintenance. By carefully controlling this compositional parameter, the catalyst achieves both economic benefits and sustained catalytic activity for CO, HC, and NO conversions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Pt is strategically introduced in specific amounts relative to Rh to create localized beneficial effects. The Pt atoms interact with Rh atoms at specific sites, enhancing Rh stability during lean conditions without compromising overall catalytic function, thus maintaining performance while reducing cost

Inventive Principle:

Principle #3Local quality

3Reliability

If Rh is used during lean conditions, then emissions control is maintained, but Rh deactivation occurs

Engineering Contradiction:

Improveemissions controlVSAvoidRh deactivation

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

Pt serves as a protective intermediary that modifies the interaction between Rh and the lean exhaust gas environment. This interaction prevents Rh from deactivating under lean conditions, allowing the catalyst to maintain emissions control reliability without Rh loss

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Pt provides preliminary protection to Rh against deactivation before it occurs during lean conditions. The Pt-Rh interaction pre-establishes a stable configuration that resists the deactivating effects of lean exhaust, preventing rather than correcting Rh deactivation

Inventive Principle:

Principle #9Preliminary anti-action

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 Rh-Pt interaction limits Rh deactivation, improves light-off and transient performances, and reduces the need for high Rh loading, making the catalyst more cost-effective while maintaining emissions control.

Implementation Method 1

a beneficial Rh—Pt interaction limits the deactivation of Rh during lean events and improves light off and transient performances

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

TWCs perform three main functions: (1) oxidation of CO

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 3

TWCs perform three main functions: (2) oxidation of unburnt HCs

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 4

TWCs perform three main functions: (3) reduction of NON

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentUS11788450B2TWC catalysts for gasoline engine exhaust gas treatments

Publication Date: 2023.10.17 JOHNSON MATTHEY PLC

AI summary

A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first platinum group metal (PGM) component supported on a first PGM support material, wherein the first PGM component comprises rhodium (Rh) and platinum (Pt); and wherein Pt and Rh has a weight ratio of at least 1:10.