Dual Palladium Zeolite Catalyst for Cold Start NOx Reduction
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Solution Overview
Problem
Current exhaust gas treatment systems are inefficient in reducing NOx emissions during the cold start period of internal combustion engines, particularly below 180°C, and this inefficiency is exacerbated by stringent emission regulations, with existing methods often increasing CO2 emissions to achieve heating.
Innovation Solution
An exhaust gas catalyst comprising a noble metal and a molecular sieve, where a significant portion of the noble metal is located inside the pores of the molecular sieve, effectively adsorbing NOx and hydrocarbons at low temperatures and converting them at temperatures above 200°C, with improved sulfur tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SCR systems are used to reduce NOx emissions, then NOx conversion efficiency is improved at operating temperature, but the system becomes ineffective during cold start period below 180°C
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating specific molecular sieves (zeolites) with different pore structures and metal components. This allows the catalyst to maintain NOx conversion efficiency across a wider temperature range, particularly improving performance below 180°C while maintaining effectiveness at higher temperatures.
Solution Approach 2:
The patent uses composite catalyst materials combining molecular sieves (zeolites) with specific metal components (precious metals like Pt, Pd, Rh and base metals). This composite structure enables the catalyst to function effectively across different temperature regimes, resolving the contradiction between low-temperature and high-temperature performance.
2Reliability
If heating strategies are employed to improve low temperature NOx conversion, then NOx emissions during cold start are reduced, but CO2 emissions increase detrimentally
Solution Approach 1:
The catalyst is designed to be self-active at low temperatures through its intrinsic chemical properties and structure. The molecular sieve and metal component combination enables the catalyst to perform NOx conversion without requiring external heating, thereby eliminating the harmful CO2 emissions associated with heating strategies.
3Device complexity
If single molecular sieve catalyst is used, then catalyst structure is simple, but sulfur tolerance is insufficient
Solution Approach 1:
The patent employs composite catalyst structures combining molecular sieves with specific metal components and support materials. This composite approach enhances sulfur tolerance through synergistic effects while maintaining reasonable structural complexity. The different components work together to resist sulfur poisoning that would affect simpler single-material catalysts.
Solution Approach 2:
The catalyst design incorporates different materials with specific local functions - molecular sieves for NOx adsorption, metal components for catalytic conversion, and support materials for structural stability and sulfur resistance. Each component is optimized for its specific role, achieving high sulfur tolerance through localized functional optimization.
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 efficiently reduces NOx and hydrocarbon emissions at low temperatures, maintaining effectiveness even after sulfur exposure, and allows for improved temperature management in exhaust systems, enhancing overall emission control without detrimental CO2 emissions.
Implementation Method 1
The exhaust gas catalyst comprises a noble metal and a molecular sieve, where a significant portion of the noble metal is located inside the pores of the molecular sieve, effectively adsorbing NOx and hydrocarbons at low temperatures
Implementation Method 2
converting them at temperatures above 200°C
Implementation Method 3
a molecular sieve, where a significant portion of the noble metal is located inside the pores of the molecular sieve
Data Source
AI summary
Exhaust gas catalysts are disclosed. One exhaust gas catalyst comprises a noble metal and a molecular sieve, and has an infrared spectrum having a characteristic absorption peak from 750 cm-1 to 1050 cm-1 in addition to the absorption peaks for the molecular sieve itself. The exhaust gas catalyst also comprises a noble metal and a molecular sieve, having greater than 5 percent of the noble metal amount located inside pores of the molecular sieve. The exhaust gas catalyst also comprises a first and second molecular sieve catalyst. The first molecular sieve catalyst comprises a first noble metal and a first molecular sieve, and the second molecular sieve catalyst comprises a second noble metal and a second molecular sieve. The first and second molecular sieves are different. The invention also includes exhaust systems comprising the exhaust gas catalysts, and a method for treating exhaust gas utilizing the exhaust gas catalysts.