CO Clean-Up Catalyst for Exhaust Emission Purification
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Solution Overview
Problem
Current three-way catalysts (TWCs) and selective catalytic reduction (SCR) systems in vehicles fail to effectively purify carbon monoxide (CO) and ammonia (NH3) emissions, particularly at varying air/fuel ratios, leading to CO slippage and NH3 emission issues.
Innovation Solution
A CO clean-up catalyst (CUC) comprising ion-exchanged Cu and Fe zeolite with supported CeO2 and Pt, along with a specific weight ratio of CeO2, is integrated into the exhaust pipe system, working in conjunction with TWC and SCR catalysts to purify CO and NH3 at different air/fuel ratios, including during delay times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the air/fuel ratio is adjusted to rich for generating NH3 in the TWC, then NH3 production for NOx purification is improved, but CO slips from the TWC and is discharged without purification
Solution Approach 1:
The patent combines the NH3 generation function of the TWC with a CO purification function by introducing a new catalytic converter downstream that specifically targets CO oxidation. This merging of functions into a sequential system allows the rich air/fuel ratio operation to generate NH3 while the downstream converter simultaneously purifies the CO that slips through.
Solution Approach 2:
The patent introduces a downstream catalytic converter as an intermediary component between the TWC and the exhaust outlet. This intermediary device specifically oxidizes CO that escapes the TWC during rich operation, acting as a mediator that handles the harmful byproduct without interfering with the NH3 generation process upstream.
2Quantity of substance
If the passive type SCR catalyst is disposed closed to the tail pipe to operate at 200-400°C, then NH3 storage and NOx purification are improved, but the SCR catalyst slips NH3 when temperature rises above 400°C at high load conditions
Solution Approach 1:
The patent introduces a downstream catalytic converter as an intermediary component between the TWC and the exhaust outlet. This intermediary device specifically oxidizes CO that escapes the TWC during rich operation, acting as a mediator that handles the harmful byproduct without interfering with the NH3 generation process upstream.
Solution Approach 2:
The patent changes the operational parameters of the SCR catalyst system by positioning it to operate within a specific temperature range (200-400°C) for optimal NH3 storage and NOx purification. The system accepts that above 400°C the SCR catalyst slips NH3, but this is managed by the overall system design including the downstream CO purification converter.
3Object-generated harmful factors
If the conventional AOC is used to oxidize NH3 slipped from the SCR catalyst, then NH3 purification at lean air/fuel ratio is improved, but the conventional AOC cannot purify NH3 slipped at rich air/fuel ratio in lean-burn gasoline engines
Solution Approach 1:
The patent creates a downstream catalytic converter with multi-functional capability to handle both CO oxidation and NH3 oxidation across different air/fuel ratio conditions. This universal converter replaces the conventional single-function AOC, providing adaptability to purify NH3 whether it slips during rich or lean operation modes.
Solution Approach 2:
The patent changes the operational parameters of the SCR catalyst system by positioning it to operate within a specific temperature range (200-400°C) for optimal NH3 storage and NOx purification. The system accepts that above 400°C the SCR catalyst slips NH3, but this is managed by the overall system design including the downstream CO purification converter.
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 CUC efficiently reduces CO and NH3 emissions by oxidizing NH3 into N2 at lean air/fuel ratios and purifying CO at rich air/fuel ratios, improving overall exhaust gas treatment by controlling air/fuel ratios and temperature profiles.
Implementation Method 1
oxidizing NH3 into N2 at lean air/fuel ratios
Implementation Method 2
CO clean-up catalyst (CUC) comprising ion-exchanged Cu and Fe zeolite with supported CeO2 and Pt
Implementation Method 3
purifying CO at rich air/fuel ratios
Implementation Method 4
The CUC efficiently reduces CO and NH3 emissions
Data Source
AI summary
An after treatment system is disclosed. The after treatment system may include a three-way catalyst (TWC), a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows. The CUC may include a zeolite in which Cu and Fe are ion-exchanged and CeO2 in which Pt is supported, wherein a weight ratio of the CeO2 to a total weight of the CUC is 30-70 wt % such that the CUC purifies NH3 at a lean air/fuel ratio and purifies NH3 during a delay time at a rich air/fuel ratio.