Wall Flow Catalyst Pore Optimization for NOx Purification
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Solution Overview
Problem
Existing exhaust gas purification catalysts face challenges in achieving enhanced NOx purification performance, particularly under stricter emission regulations, due to limitations in exhaust gas permeability and contact efficiency between the catalyst and harmful components.
Innovation Solution
The development of an exhaust gas purification catalyst with a substrate of wall flow structure and a catalyst layer that satisfies specific pore volume and permeability conditions, ensuring improved exhaust gas permeability and contact with the catalyst body, thereby enhancing NOx purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the catalyst layer is made denser to increase contact between exhaust gas and catalyst body, then purification performance improves, but exhaust gas permeability deteriorates
Solution Approach 1:
The patent applies porous materials by controlling the pore size distribution and pore volume of the catalyst layer. Specifically, it limits pores larger than 5 μm to 20% or less of total pore volume and ensures pores no larger than 5 μm constitute 80% or more of total pore volume, while maintaining pore volume at 0.2 mL/g or more. This porous structure increases the contact surface area between exhaust gas and catalyst body, improving purification performance while preserving adequate exhaust gas permeability.
2Productivity
If the catalyst layer thickness is increased to improve purification performance, then contact ability increases, but pressure loss increases
Solution Approach 1:
The patent applies parameter changes by optimizing the pore size distribution parameters and pore volume of the catalyst layer. By controlling that pores larger than 5 μm are 20% or less of total pore volume and pores no larger than 5 μm are 80% or more, while maintaining pore volume at 0.2 mL/g or more, the patent achieves improved purification performance with reduced pressure loss compared to conventional catalyst layers.
3Quantity of substance
If the pore size is increased to improve exhaust gas permeability, then permeability coefficient increases, but contact ability between exhaust gas and catalyst body decreases
Solution Approach 1:
The patent applies porous materials with controlled pore size distribution, specifically limiting pores larger than 5 μm to 20% or less of total pore volume and ensuring pores no larger than 5 μm constitute 80% or more of total pore volume. This creates an optimized porous structure that maintains adequate exhaust gas permeability while maximizing the contact surface area between exhaust gas and catalyst body for improved purification performance.
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 significantly improves NOx purification performance by increasing the contact ability between exhaust gas and the catalyst, reducing slip-through, and suppressing pressure loss, while maintaining effective permeability, thus meeting stringent emission standards.
Implementation Method 1
The NOx in the exhaust gas is converted into nitrogen and water as a result of the reducing action of the ammonia adsorbed on the catalyst body, and the NOx in the exhaust gas becomes purified as a result
Implementation Method 2
diffusion and convection of the exhaust gas inside the catalyst layer is facilitated
Implementation Method 3
diffusion and convection of the exhaust gas inside the catalyst layer is facilitated
Data Source
AI summary
The present invention provides an exhaust gas purification catalyst provided with: a substrate of wall flow structure in which inlet cells and outlet cells are partitioned by porous partition walls; and a catalyst layer disposed at least inside the partition wall and including a catalyst body. The catalyst layer satisfies the following conditions: (1) the pore volume of pores no larger than 5 μm, as measured in accordance with a mercury intrusion technique, is 24000 mm3 or greater per L of volume of the substrate; and (2) a permeability coefficient measured by a Perm porometer is 0.6 μm2 to 4.4 μm2.