CHA Zeolite Particle Size and Composition for Crack Resistance
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Solution Overview
Problem
Conventional CHA-structured zeolites used in SCR catalysts face issues with cracks due to water absorption and low NOx conversion rates, primarily due to inappropriate particle size and SiO2/Al2O3 composition ratios, leading to poor durability and heat resistance.
Innovation Solution
A CHA-structured zeolite with a SiO2/Al2O3 composition ratio of 5 to 14.9 and an average particle size of 0.1 to 0.5 µm, supported with 3.5 to 6.0% Cu, is developed, ensuring high crystallinity and improved NOx conversion performance while minimizing displacement caused by water absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a CHA-structured zeolite with a particle size of 1.0 to 8.0 μm is used to manufacture a SCR catalyst, then the heat resistance is improved, but the displacement caused by water absorption is great, leading to cracks in the catalyst
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size of CHA-structured zeolite to 0.1 to 0.5 μm and the SiO2/Al2O3 composition ratio to 15 or less. This specific parameter optimization reduces water absorption displacement while maintaining heat resistance, thereby preventing cracks and improving overall catalyst reliability.
2Productivity
If the SiO2/Al2O3 composition ratio of CHA-structured zeolite is less than 15, then the NOx conversion rate is improved, but the particle size control becomes critical to avoid excessive water absorption
Solution Approach 1:
The patent simultaneously optimizes two critical parameters: SiO2/Al2O3 composition ratio (≤15) for high NOx conversion rate and particle size (0.1 to 0.5 μm) for minimal water absorption displacement. This dual parameter control achieves both high productivity and manufacturing precision.
3Productivity
If the zeolite particle size is reduced to improve NOx conversion, then the catalytic activity increases, but the structural stability decreases due to greater displacement by water absorption
Solution Approach 1:
The patent identifies an optimal particle size range of 0.1 to 0.5 μm that balances catalytic activity and structural stability. Within this range, the zeolite maintains high NOx conversion while minimizing water absorption displacement, thereby preserving structural integrity.
4Reliability
If a CHA-structured zeolite is coated on the surface of a honeycomb unit base material, then cracks are avoided, but the zeolite density as a catalyst becomes low, resulting in low NOx conversion rate
Solution Approach 1:
Instead of coating zeolite on the honeycomb surface, the patent uses zeolite particles themselves as the honeycomb catalyst material with optimized particle size (0.1 to 0.5 μm) and composition ratio (SiO2/Al2O3 ≤ 15). This approach achieves both high NOx conversion rate and crack resistance through proper particle engineering.
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 optimized zeolite exhibits enhanced NOx converting performance, heat resistance, and durability, reducing the likelihood of cracks in the honeycomb catalyst and maintaining high catalytic activity.
Implementation Method 1
A SCR (Selective Catalytic Reduction) system in which ammonia reduces NOx to nitrogen and water is known as a system for converting exhaust gases discharged from automobiles. A CHA-structured zeolite with Cu supported thereon is drawing attentions as a SCR-catalytic zeolite.
Implementation Method 2
the displacement caused by water absorption is great
Data Source
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AI summary
The present invention provides a zeolite that is excellent in NOx converting performance and, when used as a honeycomb catalyst, suppresses damage of the honeycomb catalyst. The present invention provides a zeolite having a CHA structure, the zeolite having a SiO2/Al2O3 composition ratio of less than 15 and an average particle size of 0.1 to 0.5 µm.