Catalysed Particulate Filter Segmented Catalyst Coating
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Solution Overview
Problem
The existing methods for preparing multifunctional diesel particulate filters with different catalysts are expensive and complex due to segmentary or zone coating, which complicates the production process and increases costs.
Innovation Solution
A method involving a particulate filter body with longitudinal flow passages coated with a first catalyst washcoat containing an SCR catalyst on the dispersion side and a second combined catalyst washcoat containing an ammonia slip catalyst and oxidation catalyst on the permeation side, where the particle sizes of the catalysts are optimized to prevent diffusion and ensure effective coating, allowing for a simpler and cheaper production setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If segmentary or zone coating of different catalysts is used on the filter, then the desired catalytic functions are achieved, but the preparation process becomes expensive and difficult
Solution Approach 1:
The filter is divided into two sides (dispersion side and permeation side) with different catalyst coatings applied to each side. The dispersion side receives a first catalyst washcoat containing SCR catalyst, while the permeation side receives a second catalyst washcoat containing oxidation catalyst. This segmentation allows different catalytic functions to be achieved without complex zone coating processes.
Solution Approach 2:
Different catalyst compositions are applied locally to different sides of the filter based on the flow direction and functional requirements. The dispersion side (inlet side) is coated with SCR catalyst to handle incoming exhaust gas, while the permeation side (outlet side) is coated with oxidation catalyst to treat the filtered gas. This local quality approach simplifies the coating process while maintaining catalytic effectiveness.
2Quantity of substance
If catalyst particles are too small, then they can diffuse through the filter walls, but they cannot be effectively retained on the filter surface
Solution Approach 1:
The filter walls are designed with specific porosity and pore size characteristics that allow small catalyst particles to be retained on the surface while still permitting gas flow. The porous structure of the filter walls provides a mechanism for size-based separation, where particles smaller than the pore diameter are retained on the surface rather than passing through to the other side.
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 results in a more cost-effective and efficient preparation of multifunctional catalysed particulate filters with improved heat transfer and faster warm-up during cold starts, enabling earlier reductant injection and enhanced SCR reaction initiation.
Implementation Method 1
a first catalyst washcoat containing a first catalyst composition being active in selective catalytic reduction of nitrogen oxides
Implementation Method 2
a catalyst being active in selective oxidation of ammonia to nitrogen
Implementation Method 3
a catalyst being active in oxidation of carbon monoxide and hydrocarbons
Implementation Method 4
coating the particulate filter body with the first catalyst washcoat on the entire dispersion side and within partition walls of the filter body
Data Source
AI summary
The invention pertains to a catalysed particulate filter provided in its entire dispersion side and within its partition walls with a first catalyst being active in selective catalytic reduction of nitrogen oxides, and in its entire permeate side with a second catalyst combination with a catalyst being active in oxidation of ammonia mixed with a catalyst being active in oxidation of carbon monoxide and hydrocarbons and a method for its preparation. The mean particle size of the first catalyst is smaller than the mean pore diameter of the longitudinal porous walls, and the mean particle size of the second catalyst combination is larger than the mean pore diameter of the longitudinal walls. In the example, the first catalyst is a silica aluminium phosphate SAPO-34 promoted with 2% copper and the second catalyst is a mixture of platinum and palladium (molar ratio 3:1) supported on alumina particles and beta zeolite powder with 1.0% copper.