Hybrid Binary Catalysts for Cold-Start NOx Reduction
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Solution Overview
Problem
Current engine aftertreatment systems face challenges in reducing NOx emissions, particularly under cold-start conditions and with high engine-out NOx levels, due to issues such as urea deposit buildup, reduced fuel economy, and increased system complexity, which are exacerbated by stringent emissions regulations.
Innovation Solution
The development of a hybrid binary catalyst composition that includes metal oxide nanoparticles hybridized to a metal zeolite, providing enhanced NOx reduction efficiency and durability, capable of decomposing urea deposits and operating effectively under cold start conditions without the need for a DOC upstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SCR catalysts are used to reduce NOx emissions, then NOx reduction performance is improved, but catalyst durability deteriorates due to urea deposit buildup
Solution Approach 1:
The patent employs a composite catalyst structure combining Cu-zeolite (for NOx reduction) with Scandium-Phosphate (for urea decomposition). This composite approach allows each material to perform its specialized function: the Cu-zeolite handles NOx conversion while the Scandium-Phosphate specifically targets urea deposit removal, thereby maintaining both NOx reduction performance and catalyst durability simultaneously
2Use of energy by moving object
If high engine-out NOx levels are processed to improve fuel economy, then fuel economy is improved, but emissions control effectiveness deteriorates
Solution Approach 1:
The patent modifies the catalyst's operational parameters by introducing Scandium-Phosphate which actively decomposes urea deposits at lower temperatures. This enables the catalyst to maintain high NOx reduction efficiency even when processing high engine-out NOx levels, as the urea decomposition prevents deposit buildup that would otherwise reduce catalytic activity and emissions control effectiveness
3Productivity
If DOC is placed upstream of SCR to provide NO2 for fast SCR reaction, then NOx reduction efficiency is improved, but system complexity increases
Solution Approach 1:
The patent creates a multi-functional catalyst that simultaneously performs NOx reduction (via Cu-zeolite), urea decomposition (via Scandium-Phosphate), and provides NO2 for fast SCR reaction. This eliminates the need for a separate upstream DOC, as the same catalyst unit performs multiple functions that were previously requiring separate components, thereby reducing system complexity while maintaining high NOx reduction efficiency
4Reliability
If urea dosing is increased to handle high engine-out NOx, then NOx reduction capability is improved, but urea deposit buildup increases
Solution Approach 1:
The patent converts the harmful effect of urea deposits into a beneficial process by using Scandium-Phosphate to catalyze urea decomposition. Instead of urea deposits accumulating and poisoning the catalyst, the Scandium-Phosphate actively breaks down urea into NH3 and CO2, preventing deposit formation while maintaining the urea's essential role in NOx reduction. This transforms the deposit buildup problem into an effective urea utilization solution
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 composition achieves improved NOx reduction performance and durability, enabling efficient emissions control across varying conditions while maintaining fuel economy and reducing system complexity.
Implementation Method 1
capable of decomposing urea deposits
Implementation Method 2
The SCR system 104 includes a selective catalytic reduction catalyst which interacts with NOx gases to convert the NOx gases into N2 and water, in the presence of an ammonia reductant
Implementation Method 3
The catalyst can be an oxidation catalyst, which can include a precious metal catalyst, such as platinum or palladium, for rapid conversion of hydrocarbons, carbon monoxide, and nitric oxides in the engine exhaust gas into carbon dioxide, nitrogen, water, or NO2
Data Source
AI summary
The present disclosure describes hybrid binary catalysts (HBCs) that can be used as engine aftertreatment catalyst compositions. The HBCs provide solutions to the challenges facing emissions control. In general, the HBCs include a porous primary catalyst and a secondary catalyst. The secondary catalyst partial coats the surfaces (e.g., the internal porous surface and/or the external surface) of the primary catalyst resulting in a hybridized composition. The synthesis of the HBCs can provide a primary catalyst whose entire surface, or portions thereof, can be coated with the secondary catalyst.