Honeycomb Structure Zeolite Cell Wall Roughness NOx Conversion
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Solution Overview
Problem
Conventional honeycomb structures for NOx conversion in diesel engines face challenges in achieving high NOx conversion rates without significantly increasing pressure loss, as reducing the opening ratio to enhance zeolite content is limited by structural properties.
Innovation Solution
A honeycomb structure with a controlled cell density and surface roughness of the cell walls, incorporating zeolite and inorganic binders, maintains an optimal opening ratio while increasing reaction surface areas for improved NOx conversion, using specific zeolite types and ion exchange materials, and incorporating inorganic fibers for strength and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the opening ratio of the honeycomb structure is decreased to increase zeolite content and reaction surface area, then the NOx conversion rate is improved, but the pressure loss increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the opening ratio within the specific range of 50-65% and cell density of 31/cm², rather than simply decreasing the opening ratio. This optimized parameter combination allows sufficient zeolite content (230 g/L or more) to be incorporated while maintaining acceptable pressure loss characteristics and achieving high NOx conversion rates.
2Loss of energy
If the opening ratio is maintained at optimal levels to avoid pressure loss, then the pressure loss is reduced, but the reaction surface area decreases
Solution Approach 1:
The patent employs composite materials by combining zeolite with inorganic binders (alumina sol, silica sol, titania sol, or liquid glass) in the cell walls. This composite structure enables the cell walls to provide both structural integrity and catalytic functionality, maximizing the reaction surface area within the constrained opening ratio range and achieving high NOx conversion without increasing pressure loss.
Solution Approach 2:
The patent utilizes porous materials by incorporating inorganic fibers (alumina, silica, silicon carbide, glass, potassium titanate, or aluminum borate) into the honeycomb structure. These fibers create additional porous pathways and increase the effective surface area for catalytic reactions, allowing high NOx conversion rates to be achieved while maintaining the opening ratio within 50-65% and avoiding excessive pressure loss.
Data Source
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AI summary
A honeycomb structure includes at least one pillar shaped honeycomb unit including zeolite and an inorganic binder, the honeycomb unit including a plurality of cells extending from a first end to a second end of the honeycomb unit along its longitudinal directions, the cells being separated by cell walls; wherein 230 g/L (L represents an apparent volume) or more of zeolite is contained in the honeycomb unit; an opening ratio (P) of the honeycomb unit is in a range of 50% through 65%; the honeycomb unit has a cell density ρ of 31/cm2 through 93/cm2; and a surface roughness Ra of the cell wall is in a range of 1 µm through 30 µm.