Cu-Zeolite SCR/DPF Catalyst for Low-Clogging NOx Purification
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Solution Overview
Problem
Zeolite-based SCR catalysts have low bulk specific gravity, leading to clogged pores in DPFs when used in large amounts, reducing NOx purification capability.
Innovation Solution
An SCR/DPF catalyst using a Cu-containing zeolite with primary particle size ≤ 0.5 µm, 50% particle size ≤ 2.0 µm, and 90% particle size ≤ 2.5 µm, prepared with a viscosity ≤ 20 mPa·s slurry, to prevent pore clogging and maintain NOx purification capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of zeolite-based SCR catalyst is used to improve NOx purification capability, then the NOx purification capability is improved, but the pores of the DPF become clogged which obstructs exhaust gas flow and reduces NOx purification capability
Solution Approach 1:
The patent changes the particle size parameter of the zeolite catalyst to primary particles of 0.5 μm or less, and controls the slurry viscosity to 20 mPa·s or less at 25°C. These parameter changes allow sufficient catalyst amount to be loaded without clogging DPF pores, resolving the contradiction between NOx purification capability and pore clogging.
2Productivity
If the DPF pores are kept open to maintain exhaust gas flow, then the exhaust gas flow is maintained, but the amount of SCR catalyst that can be loaded is limited which reduces NOx purification capability
Solution Approach 1:
The patent uses ultra-fine zeolite particles (0.5 μm or less primary particle size) and controls slurry viscosity (20 mPa·s or less) to enable high catalyst loading density. This allows sufficient catalyst amount to be loaded while maintaining open DPF pores and proper exhaust gas flow, resolving the contradiction between productivity and reliability.
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 catalyst achieves both PM collection and NOx purification capabilities even with a large amount of zeolite-based SCR catalyst, maintaining high NOx purification rates in the 200°C to 400°C temperature range.
Implementation Method 1
Selective catalytic reduction (SCR) catalyst is a catalyst with which NOx is reduced to N 2 and H 2 O using urea or ammonia produced by hydrolysis of urea as a reducing agent
Implementation Method 2
a slurry, the slurry having a viscosity equal to or less than 20 mPa·s at 25°C
Implementation Method 3
A diesel particulate filter (DPF) includes a diesel particulate collection filter for removing PM
Data Source
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AI summary
To provide an exhaust gas purification catalyst capable of achieving both PM collection capability and NOx purification capability even with the use of a large amount of zeolite-based SCR catalyst. The exhaust gas purification catalyst includes a DPF substrate provided with a slurry. The slurry has a viscosity equal to or less than 20 mPa·s at 25°C and is prepared using a Cu-containing zeolite having a primary particle size equal to or less than 0.5 µm.