Hybrid Oxidation Catalyst for NOx Remediation
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Solution Overview
Problem
Current systems for remediating NOx emissions from diesel and lean-burn engines are generally expensive and ineffective in preventing hydrocarbon inhibition of catalysts.
Innovation Solution
A hybrid oxidation catalyst system comprising a noble metal oxidation catalyst with palladium particles in a ceramic layer upstream of a base metal oxide catalyst with transition metal oxide particles in another ceramic layer, which enhances NO+O2 conversion and prevents hydrocarbon inhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a base metal oxide catalyst is used to enhance NO+O2 conversion, then conversion effectiveness is improved, but hydrocarbon inhibition occurs reducing reliability
Solution Approach 1:
A noble metal oxidation catalyst is introduced as an intermediary component upstream of the base metal oxide catalyst. This noble metal catalyst oxidizes hydrocarbons before they reach the base metal oxide catalyst, preventing hydrocarbon inhibition and ensuring stable operation of the NO+O2 conversion catalyst throughout its service life.
Solution Approach 2:
The noble metal catalyst performs preliminary oxidation of hydrocarbons in the exhaust stream before the gases reach the base metal oxide catalyst. This preliminary action removes the harmful hydrocarbons that would otherwise inhibit the base metal oxide catalyst, allowing the main catalyst to operate reliably at full effectiveness.
2Reliability
If traditional expensive treatment systems are used, then NOx remediation is achieved, but system cost increases
Solution Approach 1:
The system changes the chemical parameters of the exhaust stream by oxidizing hydrocarbons to CO2 and H2O, and oxidizing CO to CO2, using catalytic reactions. This transforms the composition of the exhaust gases to eliminate hydrocarbon inhibition, enabling the use of more cost-effective base metal oxide catalysts while maintaining NOx remediation effectiveness.
Solution Approach 2:
The emission treatment system uses a composite catalyst structure combining noble metal particles on a first substrate with base metal oxide particles on a second substrate. This composite approach leverages the advantages of both catalyst types: the noble metal's ability to oxidize hydrocarbons and the base metal oxide's effectiveness for NO+O2 conversion, achieving reliable NOx remediation at lower cost than traditional single-catalyst systems.
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 hybrid system effectively oxidizes hydrocarbons and NO to NO2, improving NOx conversion efficiency and reducing costs by preventing hydrocarbon inhibition, especially at temperatures exceeding 75°C.
Implementation Method 1
The first catalyst is capable of oxidizing hydrocarbons and carbon monoxide
Implementation Method 2
The second catalyst is capable of oxidizing NO+O2 to NO2
Data Source
AI summary
A method of using a hybrid oxidation catalyst system for remediating a lean emission from a vehicle includes the step of oxidizing the hydrocarbons and carbon monoxide in an engine emission comprising hydrocarbons, carbon monoxide, NOx including NO and NO2, and oxygen with a first catalyst. The first catalyst includes noble metal particles supported in a first ceramic layer. The method further includes oxidizing the NO with a second catalyst having base metal oxide particles supported in a second ceramic layer to form NO2. The first catalyst is disposed upstream of the second catalyst and the system is capable of converting at least 10% of the amount of NO to NO2 at a temperature ranging from 75° C. to 225° C.