Zeolite-PGM Cold Start Catalyst for Low-Temperature Emission Reduction
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Solution Overview
Problem
Current exhaust gas cleaning systems for internal combustion engines are inefficient at reducing NOx and hydrocarbons during the cold start period, which is becoming increasingly challenging due to stringent emission regulations.
Innovation Solution
A cold start catalyst system comprising a zeolite catalyst with iron and palladium, combined with a supported platinum group metal catalyst on a flow-through or filter substrate, enhances NOx storage and conversion, hydrocarbon storage and conversion, and CO oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional exhaust gas cleaning systems are used, then high emission reduction efficiency is achieved at operating temperature (200°C and higher), but efficiency deteriorates significantly during cold start period below operating temperature
Solution Approach 1:
The invention changes the chemical and physical parameters of the catalyst system by introducing specific zeolite structures (beta-zeolite, ZSM-5) with iron and palladium, along with platinum group metals (Pt, Pd, Rh) on oxide supports. These parameter changes enable the catalyst to maintain high emission reduction efficiency at low temperatures during cold start, resolving the contradiction between temperature and reliability.
Solution Approach 2:
The invention employs composite catalyst materials combining zeolite support structures with iron, palladium, and platinum group metals on oxide carriers. This composite structure synergistically enhances both cold start performance and high-temperature efficiency, simultaneously addressing the contradiction between low-temperature and high-temperature emission reduction effectiveness.
2Quantity of substance
If NOx storage and release catalysts are used during cold start, then NOx storage capacity is improved, but system complexity increases due to multiple catalyst components (NOx adsorbent, SCR catalyst, NAC)
Solution Approach 1:
The invention merges multiple catalyst functions into a single integrated catalyst structure combining zeolite support, iron, palladium, and platinum group metals on oxide carriers. This unified design achieves both NOx storage and conversion capabilities while reducing system complexity compared to separate NOx adsorbent, SCR catalyst, and NAC components.
Solution Approach 2:
The invention creates a universal catalyst system that performs multiple functions simultaneously: NOx storage, hydrocarbon storage, CO oxidation, and NOx conversion. This multi-functional catalyst eliminates the need for separate dedicated components for each function, thereby reducing overall system complexity while maintaining high NOx storage capacity.
3Quantity of substance
If zeolite-based hydrocarbon trapping components are used, then hydrocarbon storage during start-up is improved, but desorption and conversion efficiency requires high downstream catalyst temperature
Solution Approach 1:
The invention modifies the desorption temperature parameter by incorporating iron and palladium in the zeolite structure along with platinum group metals, which lower the desorption temperature requirement. This enables hydrocarbon desorption and conversion at lower temperatures, resolving the contradiction between hydrocarbon storage capacity and desorption temperature requirements.
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 emissions during cold start conditions with improved NOx storage and conversion, hydrocarbon storage, and CO oxidation, demonstrating higher NOx storage capacity and selectivity to nitrogen at low temperatures, while maintaining efficient conversion at higher temperatures.
Implementation Method 1
the zeolite adsorbs and stores hydrocarbons during the start-up period and releases the stored hydrocarbons when the exhaust temperature is high enough to desorb hydrocarbons
Implementation Method 2
The catalysts adsorb NOx during the warm-up period and thermally desorb NOx at higher exhaust temperatures
Implementation Method 3
improved CO oxidation
Implementation Method 4
Downstream catalysts, such as selective catalytic reduction ('SCR') or NOx adsorber catalysts ('NAC'), effectively reduce the desorbed NOx to nitrogen
Data Source
AI summary
A cold start catalyst is disclosed. The cold start catalyst comprises a zeolite catalyst and a supported platinum group metal catalyst. The zeolite catalyst comprises a base metal, a noble metal, and a zeolite. The supported platinum group metal catalyst comprises one or more platinum group metals and one or more inorganic oxide carriers. The invention also includes an exhaust system comprising the cold start catalyst. The cold start catalyst and the process result in improved NOx storage and NOx conversion, improved hydrocarbon storage and conversion, and improved CO oxidation through the cold start period.