Circumferential Coating Honeycomb Structure for Catalyst Oozing Prevention
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Solution Overview
Problem
High-porosity honeycomb structures used in gasoline particulate filters and diesel particulate filters face issues with catalyst solution oozing out, leading to waste and instability in product control information reading, and the circumferential coating layers experience cracking due to thermal expansion differences and poor printability.
Innovation Solution
A circumferential coating material containing fused silica, a color developing agent, colloidal silica, and a silicon-based water repellent agent, with a specific composition and low water content, is applied to form a circumferential coating layer that inhibits catalyst solution oozing, enhances thermal expansion matching, and improves laser marking readability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high-porosity honeycomb structure is used to decrease pressure loss, then productivity and fuel consumption are improved, but catalyst solution oozes out from the circumferential surface
Solution Approach 1:
The coating material is divided into multiple functional components: fused silica forms the base structure, colloidal silica provides binding, color developing agents enable laser marking, and water repellent agents prevent catalyst solution penetration. This segmentation of functions within the coating material allows simultaneous achievement of porosity reduction and catalyst solution blocking.
Solution Approach 2:
The patent uses a composite coating material combining inorganic components (fused silica, colloidal silica) with functional additives (color developing agents, water repellent agents). This composite structure creates a multi-functional coating that reduces porosity while maintaining laser marking capability and preventing catalyst solution oozing.
2Loss of substance
If a circumferential coating layer is applied to prevent catalyst solution oozing, then catalyst loss is reduced, but the coating layer cracks due to thermal expansion differences
Solution Approach 1:
The patent modifies the thermal expansion parameters of the coating material by selecting fused silica as the base component, which has a thermal expansion coefficient matching the honeycomb structure. This parameter matching prevents thermal stress accumulation and cracking during high-temperature baking and operation.
3Loss of substance
If the circumferential coating layer is made dense to prevent oozing, then catalyst solution loss is reduced, but laser marking readability deteriorates
Solution Approach 1:
The coating material exhibits local quality differentiation: the fused silica and colloidal silica provide dense structure for preventing catalyst solution penetration, while the color developing agents (organic dyes or pigments) create localized optical properties that enhance laser marking contrast and readability. This spatial and functional differentiation resolves the contradiction between density and markability.
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 effectively prevents catalyst solution oozing, reduces cracking, and ensures stable laser marking readability, maintaining the structural integrity and functionality of the honeycomb structures during high-temperature baking and usage.
Implementation Method 1
a silicon based water repellent agent in a range of 1 to 10 mass % to a total mass of the fused silica, the color developing agent, and the colloidal silica
Implementation Method 2
improves laser marking readability
Implementation Method 3
a color developing agent in a range of 5 to 50 mass %
Implementation Method 4
enhances thermal expansion matching
Data Source
AI summary
A circumferential coating material which is coated on a circumferential surface of a honeycomb structure monolithically formed by extrusion, to form a circumferential coating layer, the circumferential coating material containing fused silica in a range of 20 to 75 mass %, containing a color developing agent in a range of 5 to 50 mass %, containing colloidal silica in a range of 5 to 30 mass %, and further containing a silicon based water repellent agent in a range of 1 to 10 mass % to a total mass of the fused silica, the color developing agent, and the colloidal silica.