SCR Catalyst Multiple Washcoat Formulations
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Solution Overview
Problem
Selective catalytic reduction (SCR) systems face challenges in effectively reducing NOx emissions across various operating conditions, including steady state, transient, low temperature, and high temperature conditions, due to limitations in ammonia storage density and NOx conversion efficiency.
Innovation Solution
The use of multiple washcoat formulations with differing ammonia storage densities in SCR catalysts, where the front catalyst brick has a lower ammonia storage density than the rear catalyst brick, utilizing compositions such as Vanadia-based, Cu-zeolite, and Fe-zeolite formulations, to optimize NOx conversion and ammonia storage across different conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single washcoat formulation is used in the SCR catalyst, then the device complexity is reduced, but the NOx conversion efficiency and ammonia storage capabilities cannot be optimized across various operating conditions
Solution Approach 1:
The patent applies local quality by using different washcoat formulations in different regions of the catalyst. The front catalyst brick uses a first washcoat formulation optimized for certain conditions, while the rear catalyst brick uses a second washcoat formulation optimized for other conditions. This allows each region to have tailored properties that address specific operating conditions, thereby improving overall adaptability without requiring multiple separate catalyst devices.
Solution Approach 2:
The patent segments the SCR catalyst into multiple catalyst bricks with different washcoat formulations. Instead of using a uniform catalyst throughout, the system divides the catalyst into front and rear sections, each with optimized formulations for different operating conditions. This segmentation enables the system to handle varying operating conditions more effectively while maintaining a single integrated exhaust aftertreatment apparatus.
2Productivity
If the front catalyst brick has lower ammonia storage density, then NOx conversion efficiency is improved under certain conditions, but the overall ammonia storage capability of the system is reduced
Solution Approach 1:
The patent implements local quality by assigning different ammonia storage densities to different catalyst bricks based on their position and function. The front catalyst brick has lower ammonia storage density to optimize NOx conversion efficiency under specific conditions, while the rear catalyst brick has higher ammonia storage density to compensate and ensure sufficient overall ammonia availability. This localized optimization allows the system to achieve both high conversion efficiency and adequate ammonia storage capability.
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
This approach enhances NOx conversion efficiency and ammonia storage capabilities, allowing for effective NOx reduction across a range of operating conditions, as demonstrated by the performance differences in the graphs depicting NOx conversion and ammonia storage density as functions of temperature and time.
Implementation Method 1
multiple washcoat formulations with differing performance characteristics... differing ammonia storage densities
Implementation Method 2
Selective catalytic reduction (SCR) exhaust aftertreatment... reducing emissions of oxides of Nitrogen (NOx)
Data Source
AI summary
Unique SCR catalyst including multiple washcoat formulations with differing performance characteristics are disclosed. One exemplary embodiment is an apparatus including a catalyst substrate defining a plurality of flow channels leading from an inlet to an outlet, a first washcoat composition distributed over a first portion of the flow channels, and a second washcoat composition distributed over a second portion of the flow channels. The first washcoat composition has a lower ammonia storage density than the second washcoat composition.