DOC Washcoat Precursor Using High-MW PVP for Lower PGM Loading
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Solution Overview
Problem
Existing diesel oxidation catalysts (DOCs) face challenges in achieving effective exotherm performance while minimizing the use of platinum-group metals (PGMs), which are costly, and there is a need for improved exotherm generation and NO to NO2 oxidation efficiency.
Innovation Solution
Incorporating a high molecular weight polyvinylpyrrolidone (PVP) polymer with a molecular weight of 1,000,000 to 1,750,000 g/mol into the washcoat of the DOC, particularly in Pt-rich layers, to enhance PGM dispersion and reduce calcination temperatures, thereby improving exotherm performance and NO to NO2 oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PGMs are used to achieve effective exotherm performance, then catalytic activity is improved, but cost increases
Solution Approach 1:
The patent introduces a high molecular weight PVP polymer as an intermediary substance that mediates between the catalyst support and PGMs. This polymer acts as a structural framework that enhances PGM dispersion and facilitates exotherm generation, allowing reduced PGM loading while maintaining catalytic performance. The polymer serves as a mediator that enables effective exotherm performance with lower metal content.
Solution Approach 2:
The patent creates a composite washcoat material combining high molecular weight PVP polymer with catalyst support and PGMs. This composite structure leverages the synergistic effects of each component: the polymer provides structural framework and exotherm generation capability, the support provides mechanical stability, and the PGMs provide catalytic activity. The composite approach allows optimization of each component's contribution to overall performance.
2Quantity of substance
If PGM content is reduced to lower cost, then cost decreases, but exotherm generation efficiency deteriorates
Solution Approach 1:
The high molecular weight PVP polymer serves as a mediator that compensates for reduced PGM content by providing alternative pathways for exotherm generation. The polymer's high molecular weight characteristics enable it to form a robust three-dimensional network that facilitates hydrocarbon oxidation and heat generation, maintaining productivity despite lower metal loading.
Solution Approach 2:
The patent changes the molecular weight parameter of the PVP polymer to a specific high range (greater than 1,000,000 g/mol), which fundamentally alters the polymer's physical and chemical properties. This parameter change enables the polymer to provide enhanced structural framework and exotherm generation capability, allowing the system to maintain efficiency with reduced PGM content.
3Reliability
If higher molecular weight PVP is used to improve exotherm performance, then catalytic activity is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies a clear parameter range for PVP molecular weight (greater than 1,000,000 g/mol), which simplifies the manufacturing process by providing a straightforward selection criterion. This parameter specification allows manufacturers to easily identify and source appropriate polymers without complex characterization requirements, making the enhanced performance achievable through a simple material specification rather than complex process adjustments.
4Productivity
If Pt:Pd ratio is increased to improve NO to NO2 oxidation, then oxidation efficiency is improved, but cost increases
Solution Approach 1:
The high molecular weight PVP polymer acts as a mediator that facilitates NO to NO2 oxidation by providing a structured environment for reactant concentration and reaction promotion. This intermediary structure enables enhanced oxidation efficiency at lower Pt loadings, as the polymer framework concentrates reactants and provides active sites for the oxidation reaction.
Solution Approach 2:
The patent applies local quality by creating Pt-rich zones within the washcoat structure where Pt:Pd ratio is greater than 2:1. The high molecular weight PVP polymer forms a three-dimensional network that concentrates Pt metals in specific regions, creating localized areas of high catalytic activity for NO to NO2 oxidation. This localized enrichment improves oxidation efficiency without requiring uniform high Pt content throughout the entire catalyst.
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 use of high molecular weight PVP polymer results in a DOC with reduced PGM content, lower exotherm quench temperatures, and enhanced NO to NO2 oxidation efficiency, offering a cost-effective solution with improved catalyst performance.
Implementation Method 1
enhance PGM dispersion
Implementation Method 2
Incorporating a high molecular weight polyvinylpyrrolidone (PVP) polymer... into the washcoat of the DOC
Implementation Method 3
the combustion of injected HC on the DOC will lead to the production of an exotherm, heating the exhaust gases
Implementation Method 4
injection of hydrocarbon fuel into exhaust gas upstream of the DOC... the combustion of injected HC on the DOC will lead to the production of an exotherm
Implementation Method 5
DOCs typically contain palladium and/or platinum... This catalyst converts particulate matter (PM), hydrocarbons, and carbon monoxide to carbon dioxide and water
Implementation Method 6
The DOC's role in the passive oxidation of HC, CO and NOx present in the exhaust gas flow
Implementation Method 7
the DOC can also be used to promote the conversion of NO to NO2 for downstream passive filter regeneration
Data Source
AI summary
An uncalcined catalyst article precursor for a diesel oxidation catalyst (DOC) comprises: a substrate comprising a plurality of channels extending from an inlet face to an outlet face, and a first washcoat layer provided in and/or on walls of the channels of the substrate, comprising Pt, or Pt and Pd in a weight ratio of Pt:Pd of greater than 2:1, a support material and a high molecular weight polymer, wherein the high molecular weight polymer is a PVP homo- or co-polymer and having a molecular weight of greater than 1,000,000 g/mol to 1,750,000 g/mol.