Honeycomb Catalyst Coating via Pulsed Air
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Solution Overview
Problem
Existing catalysts for exhaust gas purification face a trade-off between increasing the surface area for improved efficiency and maintaining strength and cost-effectiveness, as measures to enhance surface area often compromise structural integrity and increase manufacturing costs.
Innovation Solution
A process involving a thixotropic slurry with poly-carboxylic acid or poly-carboxylate salt is used to form a coating layer on a honeycomb support, where pulsed air is applied to increase the coating layer's surface area without altering the support's structure or increasing costs, by immersing or sucking the slurry into the support and then spraying pulsed air to create a turbulent flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of cells of the honeycomb support is increased to increase the contact area with exhaust gas, then the exhaust gas purification efficiency is improved, but the strength of the catalyst is reduced
Solution Approach 1:
The invention changes the problem from increasing contact area through adding more cells (2D plane division) to increasing contact area through expanding the perimeter of individual cells (1D boundary expansion). By making the coating layer extend further along the cell walls, the contact area increases without reducing cell size or number, thereby maintaining structural strength.
Solution Approach 2:
The invention applies local quality by creating an asymmetric coating layer distribution where the coating extends preferentially in the axial direction along the cell walls. This localized expansion of the coating layer perimeter maximizes the exhaust gas contact area in the most effective region without uniformly thickening the entire catalyst structure, thus avoiding strength reduction.
2Area of stationary object
If the thickness of the ribs of the honeycomb support is reduced to increase the contact area with exhaust gas, then the exhaust gas purification efficiency is improved, but the strength of the catalyst is significantly reduced
Solution Approach 1:
Instead of reducing rib thickness (1D dimension reduction) to increase contact area, the invention expands the coating layer perimeter in the axial direction (1D boundary expansion), achieving increased contact area through a different dimensional approach that does not compromise the mechanical integrity of the rib structure.
3Area of stationary object
If the shape of the honeycomb support is changed from rectangular-cell to hexagonal-cell to increase the contact area with exhaust gas, then the exhaust gas purification efficiency is improved, but the manufacturing cost is significantly increased
Solution Approach 1:
The invention makes the coating layer formation process multi-functional: it not only forms the necessary catalytic coating but also simultaneously increases the exhaust gas contact area through axial extension. This eliminates the need for specialized hexagonal cell geometries, allowing conventional rectangular-cell supports to achieve enhanced performance without increased manufacturing complexity or cost.
4Manufacturing precision
If the viscosity of the slurry is increased to enhance thixotropy and improve coating uniformity, then the coating quality is improved, but the ease of application is reduced
Solution Approach 1:
The invention utilizes periodic action through the thixotropic property of the slurry, which exhibits time-dependent viscosity changes. The slurry is applied in a high-viscosity state for uniform coating, then its viscosity decreases over time under shear stress during the pulsing process, allowing easy penetration and distribution. This periodic viscosity change enables both coating uniformity and ease of application.
Solution Approach 2:
The invention changes the viscosity parameter of the slurry dynamically through thixotropy. By formulating the slurry with thixotropic agents, the viscosity can be adjusted to be high during application for uniform coating, then automatically decrease during the pulsing process for easy penetration, and increase again after application to prevent dripping. This parameter change resolves the contradiction between coating quality and ease of application.
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 method enhances the surface area of the catalyst, improving exhaust gas purification efficiency without reducing strength or significantly increasing manufacturing costs, as demonstrated by increased NOx purification rates and perimeter expansion of the coating layer.
Implementation Method 1
Thixotropy is a property in which the viscosity of a material decreases with time when the material is forced to flow at a constant shear velocity and the viscosity returns to the original value again when the flow is stopped and the material is kept stationary for a while.
Implementation Method 2
In this process, a turbulent flow is produced in the honeycomb support. The flow rate of the air preferably ranges from 10 to 150 m/s. The turbulent flow stretches the perimeter of the coating layer, and hence the surface area thereof increases.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~4
AI summary
An object of the present invention is to provide a process for producing a catalyst for exhaust gas purification capable of increasing the area brought into contact with exhaust gas to improve the exhaust gas purification efficiency without decrease in strength of the catalyst for exhaust gas purification and without significant increase in manufacturing cost of the catalyst for exhaust gas purification. The present invention provides a process for producing a catalyst for exhaust gas purification formed by forming a coating layer containing a catalyst component on a honeycomb support, characterized in that the method comprises immersing the honeycomb support in a thixotropic slurry containing the catalyst component or sucking the slurry into the honeycomb support, removing the honeycomb support from the slurry, spraying pulsed air onto an end surface of the removed honeycomb support in the axial direction thereof, and baking the honeycomb support to form the coating layer on the honeycomb support.