Exhaust Gas Purifying Catalyst for 2-Stroke Engines
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Solution Overview
Problem
Conventional exhaust gas purifying catalysts for 2-stroke general-purpose engines face challenges in achieving high hydrocarbon (HC) purification performance while maintaining a compact size and low cost, as stricter emission regulations approach, and existing compositions are nearing their performance limits.
Innovation Solution
An exhaust gas purifying catalyst with a substrate and a coat layer containing palladium, platinum, or rhodium, along with specific metal oxides like zirconia, lanthana, and alkaline earth metal oxides, where zirconia content is limited to 0.07 mol or less and lanthana content is 0.05 mol or greater per 100 g of metal oxides, and palladium is diffused 60 μm or greater in depth, while platinum and rhodium are localized near the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amounts of catalysts (especially noble metals) are increased to conform to strict HC emission regulations, then HC purification performance is improved, but catalyst size and cost increase
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst, specifically using a metal oxide layer containing zirconia (7-30 mass%), lanthana (3-50 mass%), and alkaline earth metal oxides (3-50 mass%), along with controlled noble metal content (Pd: 1-5 g/L, Pt+Rh: 0.1-3 g/L). This compositional parameter optimization achieves high HC purification performance while maintaining compact catalyst size suitable for handheld power tools.
2Reliability
If the amounts of catalysts (especially noble metals) are increased to conform to strict HC emission regulations, then HC purification performance is improved, but cost increases
Solution Approach 1:
The invention optimizes the quantity parameters of noble metals to minimal effective levels (Pd: 1-5 g/L, Pt+Rh: 0.1-3 g/L) while compensating with enhanced metal oxide composition (zirconia 7-30 mass%, lanthana 3-50 mass%, alkaline earth metal oxides 3-50 mass%). This parameter substitution reduces noble metal content and cost while maintaining HC purification performance through the synergistic metal oxide system.
3Reliability
If conventional catalyst compositions are used to maximize current purification performance, then HC purification performance is improved, but adaptability to stricter future regulations is limited
Solution Approach 1:
The invention creates a composite catalyst structure with a metal oxide layer containing zirconia, lanthana, and alkaline earth metal oxides in specific proportions, combined with controlled noble metal content. This composite material system provides enhanced catalytic activity and stability, achieving high HC purification performance that can adapt to increasingly strict future emissions regulations while maintaining compatibility with current standards.
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
This configuration achieves high HC purification performance with reduced catalyst size and noble metal usage, conforming to stricter regulations while minimizing methane generation and noble metal poisoning, thus enabling compact and cost-effective designs for handheld power tools.
Implementation Method 1
hydrocarbons (HC) and carbon monoxide (CO) are purified by being converted to water (H2O) and carbon dioxide (CO2) by oxidation reaction
Implementation Method 2
hydrocarbons (HC) and carbon monoxide (CO) are purified by being converted to water (H2O) and carbon dioxide (CO2) by oxidation reaction
Implementation Method 3
the coat layer includes a noble metal and a metal oxide
Data Source
AI summary
An exhaust gas purifying catalyst for 2-stroke general-purpose engines, which is characterized in that: the exhaust gas purifying catalyst includes a base and a coat layer on the base; the coat layer contains noble metals and metal oxides; the noble metals include palladium and one or more elements selected from among platinum and rhodium; the zirconia content in the coat layer is 0.07 mole or less per 100 g of the metal oxides contained in the coat layer; and the total content of one or more metal oxides selected from among lanthana and alkaline earth metal oxides in the coat layer is 0.05 mole or more per 100 g of the metal oxides contained in the coat layer.