Diesel Oxidation Catalyst Heat Profile for Stable NO Oxidation
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Solution Overview
Problem
Existing diesel oxidation catalysts face challenges in maintaining consistent performance across their service life, particularly in stabilizing NO oxidation activity while minimizing the impact on CO/HC oxidation and exotherm generation capabilities.
Innovation Solution
A method involving a two-stage thermal treatment process is applied to a diesel oxidation catalyst, where a first heat treatment at a high temperature stabilizes the NO oxidation activity, followed by a second treatment at a lower temperature to maintain CO/HC oxidation and exotherm generation properties, with a higher platinum-group-metal concentration at the inlet end for efficient exotherm generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single high-temperature heat treatment is applied to stabilize NO oxidation activity, then NO oxidation performance is improved, but CO/HC oxidation and exotherm generation capabilities deteriorate
Solution Approach 1:
The heat treatment process is segmented into two distinct stages: a first heat treatment at a first maximum temperature to stabilize NO oxidation activity, and a second heat treatment at a second maximum temperature (at least 25°C lower) to preserve CO/HC oxidation and exotherm generation capabilities. This segmentation allows each treatment to optimize specific catalyst functions independently, resolving the contradiction between stabilizing NO oxidation and maintaining other catalytic activities.
Solution Approach 2:
The invention changes the temperature parameter between the two heat treatment stages, with the second maximum temperature being at least 25°C lower than the first maximum temperature. This parameter change enables differential effects on various catalytic components, stabilizing NO oxidation activity while preserving the exotherm generation capability and CO/HC oxidation performance.
2Power
If platinum-group-metal concentration is increased at the inlet end for exotherm generation, then exotherm generation capability is improved, but manufacturing complexity increases
Solution Approach 1:
The invention applies local quality by concentrating platinum-group-metals at the inlet end of the catalyst where exotherm generation is most needed, rather than uniformly distributing them throughout. This localized concentration optimizes exotherm generation capability at the critical inlet region while reducing overall manufacturing complexity compared to uniform high-concentration distribution.
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 method results in a catalyst with stabilized NO oxidation performance and maintained CO/HC oxidation and exotherm generation capabilities, reducing the performance delta over the catalyst's lifetime and optimizing the NO2/NO ratio for downstream components like SCR catalysts.
Implementation Method 1
subjecting the first coated substrate to a first heat treatment to form a heat-treated coated substrate, wherein the first heat treatment comprises heating the first coated substrate to a first maximum temperature and holding the first coated substrate at the first maximum temperature
Implementation Method 2
This catalyst converts particulate matter (PM), hydrocarbons, and carbon monoxide to carbon dioxide and water
Implementation Method 3
The DOC can also be used to promote the conversion of NO to NO2 for downstream passive filter regeneration
Implementation Method 4
subjecting the second coated substrate to a second heat treatment to form the diesel oxidation catalyst, wherein the second heat treatment comprises heating the second coated substrate to a second maximum temperature and holding the second coated substrate at the second maximum temperature
Data Source
AI summary
A method for the manufacture of a diesel oxidation catalyst comprises: (i) providing a carrier substrate; (ii) forming one or more platinum-group-metal-containing washcoat layers each comprising a refractory metal oxide support material on the carrier substrate to provide a first coated substrate; (iii) subjecting the first coated substrate to a first heat treatment to form a heat-treated coated substrate, wherein the first heat treatment comprises heating the first coated substrate to a first maximum temperature and holding the first coated substrate at the first maximum temperature; (iv) depositing a platinum-group-metal-containing composition comprising a refractory metal oxide support material on at least a portion of the heat-treated coated substrate to form a second coated substrate; and (v) subjecting the second coated substrate to a second heat treatment to form the diesel oxidation catalyst, wherein the second heat treatment comprises heating the second coated substrate to a second maximum temperature and holding the second coated substrate at the second maximum temperature; wherein the first maximum temperature is at least 600° C. and wherein the second maximum temperature is at least 25° C. lower than the first maximum temperature.