Hydrogen-Enriched TWC Catalysts for Cold-Start Emission Control
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Solution Overview
Problem
Existing exhaust gas treatment systems for gasoline engines are ineffective at low temperatures for reducing nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) emissions during the cold-start period due to the inefficiency of three-way conversion (TWC) catalysts, which are less active below 150°C.
Innovation Solution
Introducing a small amount of hydrogen gas (H2) upstream of the TWC catalyst during the cold-start period, modulating its introduction to achieve a specific air-to-fuel ratio (Δλ) to enhance catalyst activity, using a system comprising a catalyst article, hydrogen source, feedback sensor, and control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TWC catalysts are used for exhaust gas treatment, then CO, HC, and NOx pollutants can be abated under stoichiometric conditions, but the catalysts are ineffective at low temperatures below 150°C during cold-start period
Solution Approach 1:
Hydrogen is introduced into the exhaust gas stream before the TWC catalyst during the cold-start period to preliminarily activate the catalyst and promote pollutant conversion at low temperatures, before the catalyst would normally become effective
Solution Approach 2:
The air-to-fuel ratio is modulated by introducing hydrogen, creating a controlled rich condition (Δλ between -0.014 and -0.345) that changes the chemical environment to enhance catalyst activity and prevent nitrate formation at low temperatures
2Reliability
If hydrogen is introduced into the exhaust gas stream to enhance catalyst activity, then TWC activity is improved and NMHC+NOx emissions are minimized, but the system complexity increases with additional components
Solution Approach 1:
The system uses the engine's own exhaust gas stream as the medium for hydrogen introduction, leveraging existing system components (exhaust manifold, oxygen sensor) to deliver the beneficial effect without requiring entirely separate infrastructure
Solution Approach 2:
The oxygen sensor provides real-time feedback on the air-to-fuel ratio, allowing the control system to modulate hydrogen introduction dynamically and maintain the optimal Δλ range, ensuring consistent catalyst activation while adapting to varying engine 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
Enhances TWC catalyst activity, minimizing non-methane hydrocarbon and nitrogen oxide (NMHC+NOx) emissions by regenerating catalysts and preventing nitrate formation, even at low temperatures.
Implementation Method 1
use hydrogen as a reductant in the exhaust gas stream
Implementation Method 2
enhance TWC catalyst activity
Implementation Method 3
three-way conversion (TWC) automotive catalysts... are effective to abate CO, HC, and NOx pollutants
Implementation Method 4
preventing nitrate formation
Data Source
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AI summary
The disclosure provides a system for treating an exhaust gas stream from a gasoline engine. The system is configured to introduce controlled quantities of hydrogen gas into the exhaust gas stream upstream of a catalyst article during a cold-start period. Further provided are related methods of treating such exhaust streams. Such systems and methods are useful in reducing a level of one or more of hydrocarbons, carbon monoxide, and nitrogen oxide in a gaseous exhaust stream from a gasoline engine.