Tunable NOx Adsorber for Cold-Start Emission Control
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Solution Overview
Problem
Current NOx reduction technologies face challenges in effectively capturing and releasing nitrogen oxides at low temperatures, particularly during the cold-start period of engine operation, as existing catalysts lack sufficient activity below 200°C, leading to inefficient NOx trapping and regeneration, which affects fuel economy and emission control.
Innovation Solution
A low-temperature NOx adsorber (LT-NA) composition comprising a rare earth metal component, a platinum group metal (PGM) component, and a dopant, where the PGM and dopant are disposed on or impregnated in the rare earth metal component, allowing for modulation of adsorption/desorption properties to suit specific vehicle requirements, enabling NOx capture at low temperatures and release at higher temperatures when downstream catalytic components become effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional SCR catalysts are used, then NOx reduction is effective at high temperatures, but catalytic activity is insufficient at low temperatures below 200°C
Solution Approach 1:
The patent modifies the chemical composition parameters of the catalyst by incorporating specific rare earth metals (ceria, praseodymia, neodymia) and adjusting metal oxide ratios to enable effective NOx reduction at lower temperatures while maintaining high-temperature performance
Solution Approach 2:
The invention uses composite catalyst materials combining rare earth metal oxides with precious metal components (platinum, palladium, rhodium) supported on alumina or titania, creating a multi-functional catalyst that operates effectively across a broad temperature range from cold start to high-temperature operation
2Object-generated harmful factors
If LNT catalysts with rich purge are used to regenerate trapped NOx, then NOx emissions are controlled, but fuel economy deteriorates
Solution Approach 1:
The patent extracts and eliminates the need for rich purge regeneration by incorporating a downstream SCR catalyst that can directly reduce trapped NOx using exhaust gas conditions, thereby removing the energy-intensive rich burn regeneration step and improving fuel economy while maintaining NOx control
3Productivity
If NO to NO2 conversion is enhanced for efficient NOx trapping, then trapping efficiency improves, but reaction rate is too slow at temperatures below 200°C
Solution Approach 1:
The patent changes the catalytic parameters by incorporating specific rare earth metal oxides and precious metal combinations that accelerate the NO to NO2 oxidation reaction rate at low temperatures, enabling efficient NOx trapping during cold start conditions without requiring high conversion temperatures
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 LT-NA composition effectively stores NOx at temperatures below 200°C and releases it at predetermined elevated temperatures, improving NOx reduction efficiency and aligning with stringent emission regulations, thereby enhancing fuel economy and emission control.
Implementation Method 1
a low-temperature NOx adsorber (LT-NA) composition comprising a rare earth metal component, a platinum group metal (PGM) component, and a dopant
Implementation Method 2
releasing the stored NOx at a predetermined temperature
Data Source
AI summary
The present disclosure is directed to a method for treating a gaseous exhaust stream containing nitrogen oxides (NOx) from a diesel or lean-burn gasoline engine following a cold-start of the engine The method involves contact of the gaseous exhaust stream with at least a low temperature NOx adsorber (LT-NA) component. The LT-NA component includes a rare earth metal component, a platinum group metal (PGM) component, and a dopant. The present disclosure is also directed to a method of modulating a NOx adsorption/desorption profile of an LT-NA composition, a NOx desorption temperature range of an LT-NA composition, or both.