Dual Catalyst for NOx Removal at Low Temperatures
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Solution Overview
Problem
Current nitrogen oxide (NOx) removal catalysts, particularly Lean NOx Trap (LNT) catalysts, face challenges in maintaining effective NOx purification performance at low temperatures and after hydrothermal aging, due to limitations in NOx storage and reduction efficiency, especially in diesel engines where cerium-based materials exhibit weak storage strength and thermal desorption issues.
Innovation Solution
A catalyst comprising a physical mixture of a first catalyst with Pt, Ba, and Ce supported on reduced alumina, and a second catalyst with Cu and Ce supported on another reduced alumina, enhancing NOx storage and reduction efficiency at low temperatures and improving heat resistance through specific synthesis methods and support materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cerium (Ce) is used as the NOx storage material to improve low temperature storage performance, then low temperature storage performance is improved, but storage strength becomes weaker causing thermal desorption phenomenon
Solution Approach 1:
The patent combines barium (Ba) and cerium (Ce) as dual NOx storage materials in the catalyst composition. Ba provides strong storage strength while Ce enhances low temperature storage performance. The synergistic effect of combining these two materials resolves the contradiction between storage strength and low temperature performance.
Solution Approach 2:
The catalyst uses a composite material system comprising Ba-Ce-Oxide on alumina support. This composite structure integrates the advantages of both Ba (high storage capacity and strength) and Ce (excellent low temperature activity), creating a material that simultaneously achieves strong storage capability and low temperature performance without thermal desorption issues.
2Quantity of substance
If barium (Ba) content is increased to improve NOx storage capacity, then NOx storage capacity is improved, but thermal desorption phenomenon increases at rapid temperature increase
Solution Approach 1:
The patent merges Ba and Ce in a specific compositional ratio where Ba provides the primary storage capacity while Ce stabilizes the stored NOx against thermal desorption. This combination allows the catalyst to maintain high NOx storage capacity while preventing the thermal desorption phenomenon that occurs with Ba alone at rapid temperature increases.
Solution Approach 2:
The patent optimizes the Ba/Ce ratio and their respective content percentages to achieve the right balance between storage capacity and thermal stability. By adjusting these compositional parameters, the catalyst maintains high NOx storage capacity while the Ce component prevents thermal desorption during rapid temperature increases.
3Temperature
If a separate three-way catalyst is disposed at the front of the LNT catalyst to handle high temperature reactions, then high temperature NOx reduction is improved, but device complexity increases
Solution Approach 1:
The patent designs a single LNT catalyst that performs multiple functions: NOx storage at low temperatures, NOx reduction at high temperatures, and maintains stability after hydrothermal aging. This multi-functional catalyst eliminates the need for a separate three-way catalyst, reducing device complexity while maintaining high temperature reduction performance through the Ba-Ce-Oxide system.
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 catalyst achieves significantly improved NOx purification performance at low temperatures and maintains high efficiency even after hydrothermal aging, with enhanced heat resistance and stability, effectively addressing the limitations of existing LNT catalysts.
Implementation Method 1
A storage type of lean NOx trap (LNT) catalyst is a catalyst that suppresses emission of nitrogen oxides (NOx) by storing (or absorbing) NOx as nitrates
Implementation Method 2
the stored nitrates react with a reduction agent (for example, HC, CO, H2, etc.) to be reduced to nitrogen (N2)
Data Source
AI summary
A catalyst for removing nitrogen oxides, and the catalyst for removing the nitrogen oxides includes a first catalyst having a component including Pt, Ba, and Ce supported on a first support, and a second catalyst physically mixed with the first catalyst and having a component including Cu and Ce supported on a second support.