Selective Catalytic Reduction Catalyst Segmented Coating Backpressure
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Solution Overview
Problem
High washcoat loadings in selective catalytic reduction (SCR) catalysts for exhaust gas treatment systems lead to increased backpressure, reducing engine efficiency and potentially impairing NH3 storage, necessitating a solution that minimizes backpressure while maintaining catalytic activity.
Innovation Solution
A selective catalytic reduction catalyst with a porous wall-flow filter substrate coated with a zeolitic material comprising copper and iron, where the coating is applied both within the pores and on the surface, with a specific loading ratio and distribution to optimize catalytic activity and reduce backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high washcoat loadings (2 g/in3 and higher) are used to maximize low temperature NOx conversion and NH3 storage, then catalytic activity is improved, but backpressure increases significantly
Solution Approach 1:
The washcoat loading is segmented into two distinct locations: in-wall coating within the pores and on-wall coating on the surface. This segmentation allows the catalyst to achieve high total loading (2 g/in3 and higher) while distributing the coating material to maintain pore openness, thereby reducing backpressure while preserving catalytic activity for NOx conversion and NH3 storage
Solution Approach 2:
Different regions of the filter substrate are assigned different coating characteristics. The in-wall coating within the pores provides catalytic functionality with controlled loading to maintain pore permeability, while the on-wall coating on the surface contributes additional catalytic activity. This local differentiation allows optimization of both backpressure and catalytic performance
2Quantity of substance
If high washcoat loadings are added into the filter to maximize NH3 storage, then NH3 storage capacity is improved, but pore blockage increases which may prevent optimal NH3 storage
Solution Approach 1:
The NH3 storage function is segmented between in-wall coating within the pores and on-wall coating on the surface. The in-wall coating provides NH3 storage capacity while maintaining pore permeability through controlled loading, and the on-wall coating supplements storage capacity on the surface. This segmentation resolves the contradiction by achieving high total NH3 storage (2 g/in3 and higher) without excessive pore blockage that would prevent optimal NH3 storage
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 solution effectively reduces backpressure while maintaining good catalytic activity for nitrogen oxide reduction, enhancing the efficiency of the exhaust gas treatment system.
Implementation Method 1
a selective catalytic reduction coating comprising a selective catalytic reduction component comprising a zeolitic material comprising one or more of copper and iron
Implementation Method 2
a porous wall-flow filter substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by porous internal walls
Data Source
AI summary
The present invention relates to a selective catalytic reduction catalyst comprising a porous wall-flow filter substrate; wherein in the pores of the porous internal walls and on the surface of the porous internal walls, the catalyst comprises a selective catalytic reduction coating comprising a selective catalytic reduction component comprising a zeolitic material comprising one or more of copper and iron. The present invention further relates to a process for preparing a selective catalytic reduction catalyst using particles of a carbon-containing additive and an aqueous mixture comprising said particles of a carbon-containing additive.