NOx Storage-Reduction Catalyst with Ceria Composite Support
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Solution Overview
Problem
Conventional NOx storage-reduction catalysts face issues with heat resistance and sulfur poisoning, leading to decreased catalytic activity and NOx purifying performance when exposed to high temperatures and sulfur.
Innovation Solution
A catalyst comprising a noble metal supported on a catalyst support with a predetermined amount of ceria on a composite oxide of alumina, zirconia, and titania, which suppresses noble metal grain growth and enhances sulfur desorption, maintaining high NOx purifying activity even in the presence of sulfur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst support containing titania is used to provide sulfur-poisoning resistance, then the catalyst maintains activity in sulfur-containing environments, but the noble metal undergoes grain growth at high temperatures and catalytic activity decreases
Solution Approach 1:
The patent uses a composite oxide support containing alumina, zirconia, and titania in specific proportions (alumina: 70-90 wt%, zirconia: 5-20 wt%, titania: 1-10 wt%). This composite structure combines the sulfur resistance of titania with the thermal stability of alumina and zirconia, preventing noble metal grain growth at high temperatures while maintaining sulfur-poisoning resistance.
2Reliability
If conventional NOx storage-reduction catalysts are used, then they can store and reduce NOx under normal conditions, but they become poisoned by sulfur and deteriorate in performance
Solution Approach 1:
The patent converts the harmful effect of sulfur into a beneficial one by utilizing the sulfur-resistant properties of titania within the composite oxide support. The titania component specifically resists sulfur poisoning while the overall composite structure maintains NOx storage and reduction capabilities, effectively turning the challenge of sulfur exposure into an opportunity to leverage titania's unique properties.
3Reliability
If the catalyst is designed for sulfur resistance using titania, then sulfur-poisoning resistance is improved, but the catalyst structure becomes more complex and manufacturing becomes more difficult
Solution Approach 1:
The patent specifies precise compositional parameters for the composite oxide support (alumina: 70-90 wt%, zirconia: 5-20 wt%, titania: 1-10 wt%) to optimize both sulfur resistance and manufacturability. By defining clear parameter ranges, the patent balances the need for complex multi-component composition with practical manufacturing considerations, ensuring reproducible catalyst performance.
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 exhibits high heat resistance and catalytic activity, effectively purifying NOx even when exposed to sulfur, with improved sulfur desorption and fuel efficiency.
Implementation Method 1
the anchoring effect of this ceria suppresses the grain growth of the noble metal
Implementation Method 2
this ceria promotes sulfur desorption during a reduction treatment
Implementation Method 3
the catalyst support...readily recovers the catalytic performance through a reduction reaction
Data Source
AI summary
Provided is a catalyst for purification of exhaust gas, which comprises a noble metal supported on a catalyst support comprising a predetermined amount of ceria supported on a surface of a composite oxide composed of alumina, zirconia, and titania, exhibiting a high heat resistance and a high catalytic activity; further, a NOx storage-reduction catalyst comprising the catalyst for purification of exhaust gas and a NOx storage material (such as alkali and alkaline earth metal(s)) promotes sulfur desorption during a reduction treatment, readily recovering the catalytic performance, and exhibiting a high NOx purifying activity even when the NOx storage-reduction catalyst is exposed to sulfur.