Platinum-Impregnated Ammonia Slip Catalyst for Broad-Range NOx Control
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Solution Overview
Problem
Existing ammonia slip catalysts fail to effectively convert ammonia to nitrogen over a wide range of temperatures in vehicle driving cycles while minimizing nitrogen oxide byproducts.
Innovation Solution
A catalytic article comprising a high porosity substrate with platinum or palladium, and an SCR catalyst coating, which facilitates the selective reduction of nitrogen oxides and reduces ammonia slip by using platinum, palladium, or a mixture thereof, supported on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If more ammonia is added to maximize NOx conversion, then NOx removal efficiency is improved, but ammonia slip increases causing environmental harm and system corrosion
Solution Approach 1:
The patent combines the SCR catalyst and ASC catalyst into a single integrated catalyst article with multiple coatings on a monolithic substrate. The SCR catalyst (first coating) performs NOx reduction while the ASC catalyst (second coating) performs ammonia oxidation, allowing both functions to work simultaneously in one device rather than requiring separate catalysts
Solution Approach 2:
The integrated catalyst article performs multiple functions: NOx reduction via SCR reaction and ammonia oxidation via ASC reaction. This multi-functional design allows the system to both maximize NOx conversion and simultaneously control ammonia slip by converting excess ammonia to nitrogen and water
2Object-generated harmful factors
If conventional SCR catalyst is used alone, then NOx reduction is achieved, but ammonia slip causes corrosion and damage to exhaust system components
Solution Approach 1:
The patent combines the SCR catalyst and ASC catalyst into a single integrated catalyst article with multiple coatings on a monolithic substrate. The SCR catalyst (first coating) performs NOx reduction while the ASC catalyst (second coating) performs ammonia oxidation, allowing both functions to work simultaneously in one device rather than requiring separate catalysts
Solution Approach 2:
The ASC catalyst converts the harmful excess ammonia (which causes corrosion) into beneficial nitrogen and water. By oxidizing ammonia in the second coating, the system transforms a harmful substance into harmless products, protecting the exhaust system from corrosion while maintaining effective NOx reduction
3Object-generated harmful factors
If ammonia oxidation catalyst is added downstream of SCR catalyst, then ammonia slip is reduced, but device complexity and backpressure increase
Solution Approach 1:
The patent combines the SCR catalyst and ASC catalyst into a single integrated catalyst article with multiple coatings on a monolithic substrate. The SCR catalyst (first coating) performs NOx reduction while the ASC catalyst (second coating) performs ammonia oxidation, allowing both functions to work simultaneously in one device rather than requiring separate catalysts
Solution Approach 2:
The integrated catalyst article performs multiple functions: NOx reduction via SCR reaction and ammonia oxidation via ASC reaction. This multi-functional design allows the system to both maximize NOx conversion and simultaneously control ammonia slip by converting excess ammonia to nitrogen and water
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 achieves over 90% conversion of ammonia to nitrogen across a broad temperature range, minimizing nitrogen oxide byproducts and maintaining low backpressure.
Implementation Method 1
NOx needs to be reduced selectively with a catalyst and a reductant in a process known as selective catalytic reduction (SCR) that converts NOx into elemental nitrogen (N2) and water
Implementation Method 2
an ammonia oxidation catalyst (also known as an ammonia slip catalyst or 'ASC') is installed downstream of the SCR catalyst to remove ammonia from the exhaust gas by converting it to nitrogen
Implementation Method 3
The reductant is absorbed onto the catalyst and the NOx is reduced as the gases pass through or over the catalyzed substrate
Data Source
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AI summary
Catalytic articles having a high porosity substrate containing platinum, palladium or a mixture thereof, in walls of the high porosity substrate and an SCR catalyst coating on a wall of the high porosity substrate are disclosed. The platinum, palladium or mixture thereof can be present in the wall of the high porosity support as a metal, or as a supported platinum, palladium or a mixture thereof. The catalytic articles are useful for selective catalytic reduction (SCR) of NOx in exhaust gases and in reducing the amount of ammonia slip. Methods for producing such articles are described. Methods of using the catalytic articles in an SCR process, where the amount of ammonia slip is reduced, are also described.