Zeolite Honeycomb Structure for NOx Reduction
Solution Overview
Problem
Conventional honeycomb structures used in NOx reduction systems for automotive exhaust gases face challenges in maintaining strength and efficiency, with zeolite-based units risking reduced strength at higher zeolite content and increased cell wall thickness hindering gas penetration and catalyst utilization.
Innovation Solution
A honeycomb structure with a specific formulation of zeolite and inorganic binder, incorporating inorganic fibers and particles, optimized cell wall thickness, and porosity to balance strength and NOx treating efficiency, ensuring effective NOx reduction with a small size and light weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of zeolite is increased to improve NOx treating efficiency, then the treating efficiency is improved, but the strength of the honeycomb unit is not sufficiently maintained
Solution Approach 1:
The patent uses a composite material system consisting of zeolite particles (230-270 g/L), inorganic binder, and inorganic fibers. The inorganic binder and fibers form a reinforcement network that maintains structural strength while allowing high zeolite content (up to 300 g/L) for effective NOx treatment. This composite approach resolves the contradiction by combining materials with complementary properties.
2Strength
If the thickness of the cell wall is increased to maintain strength, then the strength is maintained, but NOx gasses are not sufficiently penetrated into the inside of the cell wall
Solution Approach 1:
The patent employs porous inorganic binder materials with controlled pore structures that allow deep gas penetration even in thin cell walls (0.2-0.4 mm). The porosity enables exhaust gases to penetrate throughout the cell wall thickness, ensuring effective catalyst utilization while maintaining strength through the porous network structure rather than increasing wall thickness.
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: cell wall thickness (0.2-0.4 mm), porosity (40-60%), zeolite content (230-270 g/L), and inorganic fiber content. By changing these parameters in combination rather than adjusting thickness alone, the patent achieves both sufficient strength and effective gas penetration for high NOx treating efficiency.
3Productivity
If the size of the honeycomb catalyst is increased to increase effective catalyst region, then the treating efficiency is improved, but the honeycomb catalyst becomes large-sized and heavy
Solution Approach 1:
The patent achieves high treating efficiency in a compact size by optimizing the effective catalyst region through controlled porosity (40-60%) and cell wall thickness (0.2-0.4 mm). These parameter changes maximize the active catalyst surface area per unit volume, providing high NOx treatment efficiency without increasing the overall catalyst size and weight.
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 honeycomb structure achieves both sufficient strength and high NOx treating efficiency, effectively utilizing all cell walls for catalyst action while maintaining a compact and lightweight design, suitable for automotive exhaust gas treatment.
Implementation Method 1
a NOx reduction system called an SCR system which uses ammonia as a reducing agent has been proposed
Implementation Method 2
a material is prepared by mixing γ alumina, ceria, zirconia, zeolite, and the like with inorganic fibers and an inorganic binder
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A honeycomb structure (1) includes a honeycomb unit (2) containing zeolite and an inorganic binder and having a shape in which a plurality of cells (3) extending from one end to the another end along the long length direction of the honeycomb unit (2) are separated by cell walls (4). An amount of zeolite contained per apparent unit volume of the honeycomb unit (2) is 230 g/L or more, and mathematical formulae [1] and [2] are satisfied when the thickness of the cell wall (4) is defined as X mm, and the porosity of the cell wall (4) is defined as Y%. 40X+20≤Y≤40X+30 0.15≤X≤0.35