Modified LNT Catalyst for Low-Temperature NOx Storage
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Solution Overview
Problem
Current exhaust gas treatment systems for internal combustion engines are inefficient in reducing NOx emissions during the cold start period, as they require temperatures above 180°C for effective NOx conversion, leading to increased CO2 emissions and deactivation issues.
Innovation Solution
A modified exhaust system comprising a lean NOx trap (LNT) with a platinum:palladium molar ratio of at least 3:1, including barium and a ceria-containing material, which stores NOx at temperatures below 200°C and releases it at higher temperatures, combined with an ammonia-selective catalytic reduction filter (NH3-SCRF) and a urea injection system to enhance NOx conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heating strategies are used to enable NOx conversion below 180°C, then NOx conversion efficiency is improved, but CO2 emissions increase
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by using a platinum:palladium molar ratio of at least 3:1, which alters the catalytic properties to enable effective NOx conversion at lower temperatures without requiring additional heating, thus avoiding increased CO2 emissions
Solution Approach 2:
The patent employs a composite catalyst material consisting of platinum, palladium, barium, and a ceria-containing material, where the synergistic combination of these materials enables low-temperature NOx storage and conversion while maintaining CO oxidation activity without requiring thermal heating
2Productivity
If conventional LNT operation is used, then NOx storage is achieved, but system deactivation by sulfation occurs
Solution Approach 1:
The patent modifies the catalyst composition by incorporating barium and ceria-containing material, which changes the chemical properties to enhance resistance to sulfation deactivation while maintaining NOx storage capacity
Solution Approach 2:
The patent converts the harmful effect of sulfation into a beneficial feature by using barium and ceria-containing material that resist sulfation deactivation, allowing the catalyst to maintain its NOx storage function even in the presence of sulfur compounds
3Productivity
If conventional LNT with standard Pt:Pd ratio is used, then NOx conversion is achieved, but CO oxidation activity is reduced
Solution Approach 1:
The patent optimizes the platinum:palladium molar ratio to at least 3:1, which changes the catalytic properties to simultaneously enhance both NOx conversion and CO oxidation activities
Solution Approach 2:
The patent uses a composite catalyst formulation with platinum, palladium, barium, and ceria-containing material, where the specific composition and synergistic interactions enable dual functionality for both NOx conversion and CO oxidation
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 system effectively reduces NOx emissions during cold start conditions while maintaining good CO oxidation activity and resistance to deactivation by sulfation, achieving efficient NOx conversion and minimizing CO2 emissions.
Implementation Method 1
The modified LNT stores NOx at temperatures below about 200°C and releases the stored NOx at temperatures above about 200°C
Implementation Method 2
The modified LNT stores NOx at temperatures below about 200°C and releases the stored NOx at temperatures above about 200°C
Implementation Method 3
maintaining good CO oxidation activity
Implementation Method 4
ammonia-selective catalytic reduction filter (NH3-SCRF)
Data Source
AI summary
An exhaust system for treating an exhaust gas from an internal combustion engine is disclosed. The system comprises a modified lean NO x trap (LNT), a urea injection system,and anammonia-selective catalytic reduction (NH 3 -SCR) catalyst. The modified LNT comprises platinum, palladium, barium, and a ceria- containing material, and has a platinum:palladium molar ratio of at least 3:1. The modified LNT stores NO x at temperatures below about 200°C and releases the stored NO x at temperatures above about 200°C. The urea injection system injects urea at temperatures above about 180°C.