Dual-Zone Catalytic Filter for Diesel Soot and Poisoning

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Solution Overview

Problem

Catalytically coated particulate filters for diesel engines face challenges in maintaining high fresh activity, ageing stability, and sulphur resistance for the conversion of carbon monoxide and hydrocarbons, particularly due to the sensitivity of platinum-palladium coatings to sulphur poisoning.

Innovation Solution

A catalytically coated particulate filter with a platinum catalyst activated with palladium on the incoming flow side and a platinum-only catalyst downstream, utilizing support materials like silicon carbide, aluminium oxide, and cerium/zirconium mixed oxides, with specific palladium to platinum ratios to enhance thermal stability and sulphur resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a platinum-palladium catalyst coating is used to enhance fresh activity and thermal stability, then the catalytic activity for converting carbon monoxide and hydrocarbons is improved, but the sulphur resistance deteriorates due to sulphur poisoning of the palladium

Engineering Contradiction:

Improvecatalytic activityVSAvoidsulphur poisoning

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The filter is coated with a first catalyst containing platinum and palladium on the incoming flow side where high fresh activity and thermal stability are needed, and with a second catalyst containing only platinum downstream where sulphur resistance is prioritized. This spatial differentiation of catalyst composition allows each zone to optimize for its specific functional requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The catalytic coating is divided into two distinct segments along the filter length: a first catalyst zone with platinum-palladium composition and a second catalyst zone with platinum-only composition. This segmentation allows the system to simultaneously achieve high fresh activity in the first zone while maintaining sulphur resistance in the second zone.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If a platinum-only catalyst coating is used to improve sulphur resistance, then the sulphur poisoning is reduced, but the fresh activity and thermal stability deteriorate compared to platinum-palladium coatings

Engineering Contradiction:

Improvesulphur resistanceVSAvoidfresh activity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Speed

If the filter is positioned close to the engine to reduce exhaust system length, then the response time is improved, but the thermal stability requirement increases due to higher exhaust gas temperatures

Engineering Contradiction:

Improveresponse timeVSAvoidthermal stability

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The catalytic coating uses a composite material system where platinum provides the base catalytic activity and sulphur resistance, while palladium adds enhanced thermal stability and fresh activity. This composite catalyst formulation allows the filter to withstand the higher temperatures encountered when positioned close to the engine while maintaining high catalytic performance.

Inventive Principle:

Principle #40Composite materials

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 filter maintains high catalytic activity over its service life, effectively converting carbon monoxide and hydrocarbons while resisting sulphur poisoning, even under varying engine conditions.

Implementation Method 1

the first catalyst contains platinum and palladium on first support materials

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

where they are catalytically converted into carbon dioxide and water. The exhaust gas and therefore also the particulate filter arranged downstream are heated with the aid of the heat of reaction that is released

Methodology Applied

Scientific EffectExothermic reaction: Exothermic Reaction

Implementation Method 3

catalytic coating of the filter... the soot ignition temperature is lowered

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentUS7977275B2Catalytically coated particle filter and method for producing the same and its use

Publication Date: 2011.07.12 UMICORE AG & CO KG

AI summary

The invention proposes a particulate filter having a catalytic coating which contains two catalysts arranged one behind the other. The first catalyst is located in the gas inlet region of the filter and contains a palladium/platinum catalyst. The second catalyst is arranged downstream of the first catalyst and preferably contains platinum alone as catalytically active component. The combination of these two catalysts provides the coated filter with a good ageing stability and resistance to sulphur poisoning.