Catalyst Rhodium Depletion Reduction via Pre-Heating
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Solution Overview
Problem
The high cost of rhodium in catalytic converters for internal combustion engines due to stringent emission standards, particularly the European emissions standard EU4, necessitates a reduction in rhodium loading while maintaining low emission limits, which is hindered by the slow light-off temperature of catalysts with reduced rhodium loading.
Innovation Solution
A direct-injection internal combustion engine with a turbocharger and a catalytic converter system that employs a noble metal load with a palladium to rhodium weight ratio greater than 9:1, combined with a specific noble metal loading of at most 40 g/ft^3, and a heating measure involving multiple fuel injections to achieve a catalyst temperature above 300°C within 30 seconds, ensuring compliance with EU standard 4 or 5 emission limits at reduced rhodium consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the rhodium loading in the catalytic converter is reduced to lower costs, then the noble metal cost decreases, but the light-off temperature is not reached quickly enough after cold start
Solution Approach 1:
The patent applies preliminary action by implementing a heating measure before the catalyst needs to reach light-off temperature. A multiple injection of fuel is performed during intake and compression strokes to pre-heat the exhaust gas and catalyst, ensuring the catalyst reaches 300°C within 30 seconds even with reduced rhodium loading. This preliminary heating action compensates for the reduced thermal mass and reactivity of the lower rhodium content.
Solution Approach 2:
The patent changes the operating parameters of the internal combustion engine to optimize catalyst heating. By adjusting injection timing (early injection during intake stroke and late injection during compression stroke) and fuel injection quantity, the exhaust gas temperature is increased to accelerate catalyst light-off. This parameter change allows the system to achieve rapid light-off with reduced rhodium loading by controlling the thermal environment rather than relying solely on the catalyst's inherent properties.
2Quantity of substance
If the palladium to rhodium weight ratio is increased to reduce rhodium consumption, then the cost decreases, but the maintaining emission standards becomes more difficult
Solution Approach 1:
The patent uses the exhaust gas itself as an intermediary to transfer heat to the catalyst. By injecting fuel that burns in the exhaust stream, the hot exhaust gas acts as a mediator to rapidly heat the catalyst to light-off temperature. This intermediary heating mechanism compensates for the reduced catalytic activity from lower rhodium content, maintaining emission standard compliance while reducing rhodium consumption.
Solution Approach 2:
The patent implements periodic fuel injection during specific engine cycles (intake and compression strokes) to periodically heat the exhaust gas and catalyst. This periodic heating action ensures the catalyst reaches operating temperature quickly after cold start, maintaining reliable emission control performance with the modified noble metal formulation that has higher Pd:Rh ratio.
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
This approach allows for cost-effective, low-tailpipe emissions after a cold start, maintaining the mechanical and thermal stability of the catalyst coating while achieving the required emission standards without external exhaust gas recirculation, thus reducing rhodium usage and operational costs.
Implementation Method 1
Catalyst systems for internal combustion engines for motor vehicles with which pollutants in exhaust gases from internal combustion engines can be converted into harmless or less harmful components
Implementation Method 2
a heating measure is provided in which, in homogeneous operation, a multiple injection of fuel takes place, with at least one first early fuel injection during an intake stroke and at least one second later injection in a compression stroke of a cylinder, so that the catalyst exceeds a temperature TK of 300 °C within a time interval of 30 seconds
Data Source
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AI summary
The invention relates to a method for the after-treating of an exhaust gas from a preferably direct-injection and/or spark-ignition internal combustion engine, wherein the exhaust gas is fed through a catalytic converter system connected downstream of the internal combustion engine, the system comprising at least one catalyst having a noble metal depletion comprising at least the elements palladium and rhodium, the elements palladium and rhodium being present in the noble metal depletion in a weight ratio of > 5:1, 6:1, 7: 1, 8:1, 9:1, 10:1, 11:1, or 12:1, the catalyst exceeding a temperature T? of 300°C, 450°C, 550°C, 600°C within a time interval of 30 seconds, preferably 20 seconds, especially preferably 10 seconds after starting the internal combustion engine operating in the new European driving cycle, and/or the cumulative untreated emissions of hydrocarbons not exceeding 0.05 g/km and/or of nitrogen oxides not exceeding 0.04 g/km within a time interval of 10 seconds, preferably 20 seconds, especially preferably 30 seconds after starting the engine operating in the new European driving cycle, and/or the internal combustion engine achieving at least the emissions limit values of EU standard 4, preferably EU standard 5, in the new European driving cycle. The invention further relates to a device for exhaust gas after-treatment.