Dual-Zone Oxidation Catalyst for Low-Temperature CO Conversion
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Solution Overview
Problem
Existing oxidation catalysts for compression ignition engines, such as diesel engines, face challenges in achieving low 'light-off' temperatures for efficient CO and HC oxidation, while also maintaining durability and stability over time.
Innovation Solution
The use of a catalyst formulation that includes a combination of an alkaline earth metal component, such as barium, and a modified alumina support material with a heteroatom component, like silica, in conjunction with platinum and palladium, enhances the low-temperature CO oxidation activity and maintains stable NO oxidation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst formulation includes both platinum and palladium to improve catalytic activity and durability, then the catalytic performance and stability are improved, but the cost of the catalyst increases
Solution Approach 1:
The invention changes the chemical parameters of the catalyst formulation by incorporating alkaline earth metals (calcium, strontium, or barium) at specific concentrations (0.1-10 wt%) alongside platinum and/or palladium. This parameter modification enables the catalyst to achieve improved durability and low-temperature activity while using optimized amounts of expensive platinum group metals, thus resolving the contradiction between reliability and cost.
Solution Approach 2:
The invention creates a composite catalyst material combining platinum group metals with alkaline earth metals and alumina support. This composite formulation synergistically enhances catalytic durability and low-temperature activity while allowing reduced loading of expensive platinum and palladium, thereby addressing both reliability improvement and cost reduction.
2Productivity
If the exhaust gas temperature is increased to improve catalyst activity, then the catalytic reaction efficiency is improved, but the energy consumption increases
Solution Approach 1:
The invention modifies the catalyst's chemical composition parameters by adding alkaline earth metals, which fundamentally change the catalyst's light-off temperature characteristics. This enables high catalytic activity at lower exhaust gas temperatures, thus improving productivity while reducing the energy that would otherwise be required to heat the exhaust gas to higher temperatures.
Solution Approach 2:
The invention replaces the mechanical/thermal approach of heating exhaust gas to increase reaction efficiency with a chemical approach - using alkaline earth metal-modified catalysts that inherently provide high activity at lower temperatures. This substitution achieves the same productivity goal with lower energy consumption.
3Temperature
If the light-off temperature is reduced to improve low-temperature oxidation activity, then the CO and HC conversion efficiency at low temperatures is improved, but the catalyst formulation complexity increases
Solution Approach 1:
The invention systematically changes the chemical composition parameters by incorporating specific alkaline earth metals (Ca, Sr, or Ba) at defined concentration ranges (0.1-10 wt%). This controlled parameter change achieves reduced light-off temperature and improved low-temperature activity while maintaining manageable formulation complexity through clear compositional specifications.
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
This catalyst formulation achieves excellent low-temperature CO oxidation activity, converting high levels of CO in exhaust gases below 250°C, and maintains stable NO oxidation performance, even after aging, making it suitable for use in combination with other emissions control devices.
Implementation Method 1
an oxidation catalyst (known as a diesel oxidation catalyst (DOC)) is typically used to treat the exhaust gas produced by such engines. Diesel oxidation catalysts generally catalyse the oxidation of (1) carbon monoxide (CO) to carbon dioxide (CO2), and (2) HCs to carbon dioxide (CO2) and water (H2O)
Implementation Method 2
Diesel oxidation catalysts generally catalyse the oxidation of (1) carbon monoxide (CO) to carbon dioxide (CO2), and (2) HCs to carbon dioxide (CO2) and water (H2O)
Data Source
Figure 1
AI summary
An exhaust system for a compression ignition engine comprises an oxidation catalyst for treating carbon monoxide (CO) and hydrocarbons (HCs) in exhaust gas from the compression ignition engine, wherein the oxidation catalyst is upstream of a selective catalytic reduction (SCR) catalyst or a selective catalytic reduction filter (SCRF) catalyst and an injector for injecting a nitrogenous reductant into exhaust gas downstream of the oxidation catalyst, wherein the oxidation catalyst comprises a first zone and a second zone having different compositions and in a side-by-side arrangement on a flow-through monolith substrate, wherein the first zone is upstream of the second zone; wherein the first zone comprises a combination of a platinum (Pt) component and a palladium (Pd) component as the only platinum group metal (PGM) component, an alkaline earth metal component and a support material comprising alumina doped with silica; wherein the second zone comprises a platinum (Pt) component as the only platinum group metal (PGM) component; and wherein the platinum group metal (PGM) components, the alkaline earth metal component and the support material are disposed on the substrate.