Pd-Rich Catalysed Soot Filter for Ammonia Slip Control
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Solution Overview
Problem
Existing exhaust gas treatment systems for vehicular lean burn internal combustion engines require a dedicated ammonia slip catalyst, which increases complexity, cost, and backpressure, while also producing undesirable NOx re-make and N2O emissions.
Innovation Solution
A system comprising a Pd-rich or Pd-only catalysed soot filter (CSF) integrated between two selective catalytic reduction (SCR) catalysts, eliminating the need for a separate ammonia slip catalyst by leveraging the CSF's enhanced NH3 oxidation selectivity to reduce NOx re-make and N2O production, while maintaining CO and HC conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated ammonia slip catalyst is included in the exhaust system, then ammonia oxidation performance is improved, but system complexity and device complexity increase
Solution Approach 1:
The patent combines the ammonia slip catalyst function with the catalysed soot filter by coating the filter substrate with a ammonia oxidation catalyst layer. This integration merges two separate components (ammonia slip catalyst and soot filter) into one, eliminating the need for a dedicated ammonia slip catalyst while maintaining ammonia oxidation performance. The catalyst layer is applied directly to the soot filter substrate, creating a multi-functional component that handles both particulate matter filtration and ammonia slip control.
2Reliability
If a dedicated ammonia slip catalyst is included in the exhaust system, then ammonia oxidation performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent integrates the ammonia slip catalyst function into the catalysed soot filter structure, eliminating the need for a separate ammonia slip catalyst component. This reduces the total number of parts that need to be manufactured, assembled, and installed, thereby lowering manufacturing costs. The catalyst layer is applied during the soot filter manufacturing process, further reducing overall production expenses.
3Reliability
If a dedicated ammonia slip catalyst is included in the exhaust system, then ammonia oxidation performance is improved, but backpressure increases
Solution Approach 1:
The patent combines the ammonia slip catalyst function with the catalysed soot filter, eliminating the need for a separate ammonia slip catalyst component. This reduction in the number of components directly decreases the cumulative backpressure in the exhaust system, as each additional component contributes to flow resistance. The integrated design maintains ammonia oxidation performance while improving exhaust flow characteristics.
4Reliability
If traditional Pt-based ammonia slip catalyst is used, then ammonia oxidation performance is improved, but NOx re-make and N2O emissions increase
Solution Approach 1:
The patent changes the catalyst material from traditional platinum-based to palladium-based, which has different catalytic properties. Palladium exhibits superior selectivity for ammonia oxidation to nitrogen and water, while minimizing the formation of NOx and N2O byproducts. This material parameter change fundamentally alters the reaction pathway and product distribution, reducing harmful emissions while maintaining ammonia conversion efficiency.
Solution Approach 2:
The patent employs a composite catalyst structure consisting of palladium particles supported on a ceramic substrate with specific surface properties. This composite material design optimizes the catalytic activity and selectivity, allowing efficient ammonia oxidation while suppressing unwanted side reactions that produce NOx and N2O. The support material plays a crucial role in directing the reaction toward desired products.
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 system achieves higher NOx conversion, reduces platinum group metal loading, decreases system complexity and cost, and minimizes N2O emissions, with improved performance under aggressive driving conditions.
Implementation Method 1
A system comprising a Pd-rich or Pd-only catalysed soot filter (CSF) integrated between two selective catalytic reduction (SCR) catalysts, eliminating the need for a separate ammonia slip catalyst by leveraging the CSF's enhanced NH3 oxidation selectivity
Implementation Method 2
maintaining CO and HC conversion efficiency
Implementation Method 3
a first selective catalytic reduction (SCR) catalyst... a second selective catalytic reduction (SCR) catalyst
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
A system for treating an exhaust gas from a vehicular lean burn internal combustion engine comprises, in order: (i) a first means for injecting a nitrogenous reductant; (ii) a first selective catalytic reduction (SCR) catalyst; (iii) a catalysed soot filter (CSF) comprising a filter substrate; and (iv) a second selective catalytic reduction (SCR) catalyst, wherein the CSF comprises palladium and, optionally, platinum, wherein a weight ratio of palladium to platinum in the CSF is greater than 1 : 1 and wherein a total platinum group metal content of the CSF is from 0.3 to 2gft3.