Pt-Pd Diesel Catalyst Zeolite Light-Off
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Solution Overview
Problem
Diesel engines face challenges in reducing emissions of particulate matter, nitrogen oxides, unburned hydrocarbons, and carbon monoxide due to high light-off temperatures and potential poisoning effects of palladium in oxidation catalysts, which hinder effective conversion of pollutants, especially during cold-start periods.
Innovation Solution
A catalytic article comprising a Pt/Pd diesel oxidation catalyst with a zeolite that minimizes negative interactions between platinum group metals and the zeolite, using a high-surface area refractory metal oxide support with a silica-to-alumina molar ratio greater than 1200, and specific zeolite frameworks like beta, MFI, and MWW to enhance CO/HC light-off and storage functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Pt/Pd diesel oxidation catalyst is used to treat exhaust emissions, then the oxidation of hydrocarbons and carbon monoxide is enhanced, but the high light-off temperature and palladium poisoning effects hinder effective conversion during cold-start periods
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating specific zeolite structures (beta, MFI, or MWW) with controlled silica-to-alumina ratios (15-100), and optimizing the Pt:Pd ratio (1:4 to 4:1). These parameter changes enable the catalyst to achieve effective oxidation at lower temperatures while maintaining high conversion efficiency during cold-start periods
Solution Approach 2:
The patent creates a composite catalyst material combining platinum group metals (Pt and Pd) with zeolite structures supported on high-surface-area refractory metal oxide. This composite structure synergistically combines the oxidation activity of Pt/Pd with the hydrocarbon storage and low-temperature promotion capabilities of zeolite, resolving the contradiction between oxidation efficiency and light-off temperature
2Productivity
If palladium is used in the oxidation catalyst to reduce cost and maintain activity, then catalytic conversion is improved, but palladium poisoning effects occur that reduce catalyst performance
Solution Approach 1:
The patent optimizes the Pd content and Pt:Pd ratio within specific ranges (Pt:Pd from 1:4 to 4:1) to balance cost and performance. This parameter optimization prevents excessive Pd accumulation that causes poisoning while maintaining sufficient catalytic activity for effective exhaust treatment
Solution Approach 2:
The zeolite component acts as an intermediary that protects the Pt/Pd active sites from poisoning effects. The zeolite structure adsorbs harmful substances and regulates the interaction between Pd and the support material, thereby maintaining catalyst stability and preventing deactivation
3Quantity of substance
If zeolite is used to store hydrocarbons during cold-start periods, then HC storage function is improved, but premature release of stored hydrocarbons occurs that reduces treatment efficiency
Solution Approach 1:
The patent carefully controls the silica-to-alumina ratio of the zeolite (15-100) and selects specific zeolite structures (beta, MFI, or MWW) to optimize the balance between HC storage capacity and release timing. These parameter adjustments ensure that hydrocarbons are stored during cold-start and released at the appropriate time for complete oxidation, preventing premature release
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 effectively oxidizes hydrocarbons and carbon monoxide to carbon dioxide and water, reduces light-off temperatures, and prevents premature release of stored hydrocarbons, thereby improving diesel engine exhaust treatment efficiency and reducing emissions.
Implementation Method 1
a zeolite and a platinum group metal (PGM) comprising platinum and palladium supported on a high surface area refractory metal oxide support such that the zeolite minimizes negative interactions of these platinum group metals with the zeolite
Implementation Method 2
a catalytic article comprising a Pt/Pd diesel oxidation catalyst with carbon monoxide/hydrocarbon (CO/HC) light-off and hydrocarbon (HC) storage functions
Implementation Method 3
The solution effectively oxidizes hydrocarbons and carbon monoxide to carbon dioxide and water
Data Source
Figure 1~2
Figure 3
AI summary
A diesel oxidation catalyst for the treatment of exhaust gas emissions, such as the oxidation of unburned hydrocarbons (HC), and carbon monoxide (CO) and the reduction of nitrogen oxides (NOx) is described. More particularly, the present invention is directed to a washcoat composition comprising high silica to alumina zeolite and platinum and palladium such that the zeolite minimizes negative interactions of these platinum group metals with the zeolite.