Dual-Layer NOx Adsorber Catalyst for Low-Temperature Storage
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Solution Overview
Problem
Lean burn engines, such as diesel engines, face inefficiencies in NOx emission control due to existing NOx absorber catalysts, which are ineffective at low temperatures and require fuel-rich conditions for NOx release, affecting fuel economy and increasing CO2 emissions.
Innovation Solution
A passive NOx absorber catalyst comprising a molecular sieve catalyst with a noble metal and a palladium-based catalyst supported on cerium oxide, allowing NOx storage at low temperatures and controlled release when downstream SCR or SCRF catalysts reach operating temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional NOx absorber catalyst is used, then NOx can be stored at high temperatures, but it is ineffective at low temperatures and requires fuel-rich conditions for release
Solution Approach 1:
The catalyst is divided into two distinct functional segments: a first catalyst layer for low-temperature NOx storage and a second catalyst layer for high-temperature NOx storage. This segmentation allows each layer to operate optimally in its respective temperature range, enabling effective NOx capture during cold start conditions without requiring fuel-rich purge conditions
Solution Approach 2:
The invention changes the operational parameters by using a passive thermal-based release mechanism instead of fuel-rich chemical reactions. The second catalyst layer stores NOx at higher temperatures and releases it passively when exhaust temperatures rise, eliminating the need for fuel-rich conditions and reducing overall fuel consumption
2Adaptability or versatility
If a single-material PNA is used, then the device is simple, but it cannot effectively store NOx across a wide temperature range
Solution Approach 1:
The invention uses a composite catalyst structure with two different catalyst materials having complementary temperature characteristics. The first catalyst material (e.g., Pt on molecular sieve) excels at low-temperature NOx storage, while the second catalyst material (e.g., Pd on ceria) excels at high-temperature NOx storage. This composite approach enables effective NOx capture across the full operating temperature range of the engine
Solution Approach 2:
The dual-catalyst system provides multi-functionality by handling both cold start conditions and normal operating conditions within a single catalyst device. The first catalyst layer addresses cold start emissions, while the second catalyst layer handles NOx storage during normal operation, making the system universally effective across all engine operating conditions
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 effectively stores NOx at low temperatures and releases it when downstream catalysts are operational, improving NOx control and reducing fuel consumption and CO2 emissions by avoiding the need for fuel-rich conditions.
Implementation Method 1
PNAs are able to store or adsorb NOx at relatively low exhaust gas temperatures (e.g. less than 200 °C), usually by adsorption
Implementation Method 2
release NOx at higher temperatures. The NOx storage and release mechanism of PNAs is thermally controlled
Data Source
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AI summary
A NOx absorber catalyst for treating an exhaust gas from a diesel engine. The NOx absorber catalyst comprises a first NOx absorber materialcomprising a molecularsieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a molecular sieve, and wherein the molecular sieve contains the noble metal; a second NOx absorber material comprising palladium (Pd) supported on an oxide of cerium; and a substrate having an inlet end and an outlet end.