Multi-Stage Diesel Particulate Filter with Cerium-Platinum Catalyst
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Solution Overview
Problem
Diesel engines emit significant particulates and NOx, with existing catalysts facing challenges in durability, sulfate formation, and inefficient NO oxidation, limiting effective soot oxidation temperatures and filter regeneration.
Innovation Solution
Employing a fuel-borne catalyst comprising cerium and platinum group metals in a multi-stage particulate filter system, where cerium nitrates form on the filter surface to enhance soot oxidation at lower temperatures, and utilizing NO2 as a powerful oxidant, while maintaining resistance to sulfur poisoning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If catalyzed soot filters are used to decrease soot oxidation temperature, then passive trap regeneration is enabled, but durability is poor and sulfate formation occurs
Solution Approach 1:
The filter is divided into multiple functional zones: a first catalytic layer containing Pt and Ce for NO oxidation and sulfate resistance, and a second catalytic layer containing Pd for enhanced soot oxidation. This segmentation allows each layer to specialize in specific functions, improving overall durability while maintaining low regeneration temperature.
Solution Approach 2:
The invention uses composite catalytic materials combining multiple precious metals (Pt, Pd, Ce) with specific support materials. The composite structure leverages the synergistic effects of different materials: Pt for NO oxidation, Ce for sulfate resistance and oxygen storage, and Pd for soot oxidation, achieving both low temperature operation and high durability.
2Productivity
If Pt is used as primary catalyst component to generate NO2, then soot oxidation is enhanced, but sulfate formation and catalyst deactivation occur
Solution Approach 1:
Cerium oxide (CeO2) acts as an intermediary material that resists sulfur poisoning and maintains catalytic activity in the presence of SO2. The Ce component protects the Pt catalyst from deactivation by sulfur compounds while still allowing NO oxidation to proceed, thereby preventing sulfate formation on the catalyst surface.
Solution Approach 2:
The invention modifies the chemical environment around the Pt catalyst by introducing CeO2, which changes the local oxidation state and sulfur interaction parameters. This parameter change allows the system to maintain high soot oxidation rates while resisting sulfate formation through the sulfur-resistant properties of cerium oxide.
3Productivity
If fuel injection is used to increase filter temperature for regeneration, then soot oxidation is promoted, but fuel economy deteriorates
Solution Approach 1:
The catalytic filter enables self-regeneration by utilizing the vehicle's own exhaust gas composition (NO, O2, soot) as reactants. The Pt-Ce-Pd catalyst system automatically facilitates the oxidation reactions needed for soot removal without requiring external fuel injection, making the regeneration process energy-self-sufficient and preserving fuel economy.
Solution Approach 2:
The invention changes the chemical parameters of the exhaust gas by using catalysis to lower the activation energy required for soot oxidation. This parameter change allows regeneration to occur at the lower temperatures naturally present in diesel exhaust, eliminating the need for high-temperature fuel injection regeneration.
4Device complexity
If uncatalyzed soot filters are used, then system simplicity is maintained, but soot oxidation temperature remains too high for continuous regeneration
Solution Approach 1:
The invention applies catalytic materials locally on specific surfaces within the filter structure rather than requiring a completely different filter design. The Pt-Ce-Pd catalyst layers are deposited on the internal surfaces of the filter walls, providing localized catalytic activity that lowers the balance point temperature while maintaining the overall simplicity of the uncatalyzed filter architecture.
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 solution significantly reduces particulate emissions, particularly ultrafine particles, with improved regeneration characteristics and durability, maintaining fuel economy without increasing DPF size, and effectively utilizing conventional and low-sulfur fuels.
Implementation Method 1
The use of catalysts has the potential of decreasing the soot oxidation temperature sufficiently to provide for passive trap regeneration
Implementation Method 2
active and passive filter regeneration strategies are being used in practice to bum soot
Implementation Method 3
burn soot
Implementation Method 4
cerium nitrates form on the filter surface to enhance soot oxidation at lower temperatures
Implementation Method 5
a filter section comprised of passages effective to remove particulates from a moving stream of combustion gases
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3
AI summary
A method and apparatus are provided for reducing emissions of particulates from diesel engines. Exhaust is passed through a diesel particular filter having at least two stages comprised of (a) a catalyst section having a platinum group metal catalyst on contact surfaces within the catalyst section and (b) a filter section comprised of passages effective to remove particulates from a moving stream of combustion gases generated by combusting the fuel in the engine and holding them therein to permit their oxidation. Carbon removal is enhanced by utilizing levels of platinum group metal composition, cerium compositions, fuels and/or optional chemical enhancers to generate NO2 in the catalyst section in amounts sufficient to form cerium nitrates in the filter section. The cerium oxide is associated with and maintains dispersion of the platinum in the filter section, and the cerium nitrates are available at the surface and within the soot particles to provide enhanced soot oxidation at a lower balance point.