Three-Way Catalyst with Metal Oxide Monolayer for Low-Temperature Emissions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current automotive catalysts face challenges in effectively reducing hydrocarbons, carbon monoxide, and nitrogen oxides at low temperatures and varying engine operating conditions, particularly during cold starts and in fuel-efficient powertrains with lower operating temperatures, where traditional catalysts are less active.
Innovation Solution
A three-way catalytic converter is developed with particles comprising a first metal oxide center, a second metal oxide monolayer, and catalytically active metal, where the molar ratio of metal in the monolayers to metal in the centers is between 0.01 and 0.2, and the catalyst is coated onto a ceramic or metallic monolith substrate, enabling effective conversion of pollutants across a wide range of temperatures and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional catalysts are used, then they work at high temperatures, but they are less active at low temperatures and during cold starts
Solution Approach 1:
The patent modifies the chemical composition parameters of the catalyst by incorporating specific metal oxides (ceria, zirconia, titania) in controlled ratios, and adjusting the precious metal loading (0.5-2.0 wt% Pd, 0.1-0.5 wt% Rh). These parameter changes enable the catalyst to maintain high activity across a broader temperature range, particularly improving low-temperature performance while retaining high-temperature effectiveness.
Solution Approach 2:
The patent creates a composite catalyst structure combining multiple metal oxides (alumina support with ceria, zirconia, or titania overlays) and precious metals (Pd and Rh). This composite material approach synergistically combines the thermal stability of alumina with the low-temperature activity enhancement from ceria/zirconia/titania and the catalytic function of Pd/Rh, resolving the contradiction between high-temperature stability and low-temperature activity.
2Productivity
If catalyst loading is increased to improve conversion rates, then conversion efficiency increases, but cost and device complexity increase
Solution Approach 1:
The patent optimizes the concentration parameters of catalyst components, specifically limiting precious metal loading to 0.5-2.0 wt% Pd and 0.1-0.5 wt% Rh. This parameter optimization achieves high conversion rates (90%+ for CO, HC, and NOx) while controlling cost and complexity by avoiding excessive metal loading.
Solution Approach 2:
The patent introduces metal oxide intermediaries (ceria, zirconia, titania) that mediate between the alumina support and precious metals. These intermediaries enhance the catalytic activity per unit of precious metal, allowing lower metal loadings to achieve the same conversion rates, thereby reducing cost and complexity while maintaining productivity.
3Adaptability or versatility
If catalyst is designed for stoichiometric conditions, then it performs well at stoichiometry, but it cannot effectively treat rich and lean conditions simultaneously
Solution Approach 1:
The patent designs a universal catalyst formulation that performs effectively across stoichiometric, rich, and lean operating conditions. The combination of Pd (effective for oxidation in rich/lean conditions) and Rh (effective for reduction in stoichiometric/rich conditions), supported by redox-active metal oxides like ceria that can buffer oxygen storage, creates multi-functional catalyst behavior suitable for all three operating modes.
Solution Approach 2:
The patent adjusts compositional parameters including the ratio of Pd to Rh, the type and amount of metal oxide overlay (ceria, zirconia, titania), and the surface area of the alumina support. These parameter adjustments optimize the catalyst's adaptability to varying oxygen concentrations and exhaust compositions across different operating conditions while maintaining high conversion efficiency.
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 high conversion rates (at least 90%) of CO, NO, and hydrocarbons at temperatures between 150°C and 350°C, maintaining effectiveness under stoichiometric, rich, and lean conditions, even at low temperatures, thus addressing the limitations of existing catalysts.
Implementation Method 1
a catalytically active metal to decrease concentration of hydrocarbons, carbon monoxide, and nitrogen oxides in exhaust gas
Implementation Method 2
converting HC species, CO, and NOx have been developed
Data Source
AI summary
A method utilizes a three-way catalytic converter, having a catalyst formed from a plurality of particles each including a first metal oxide center, a second metal oxide monolayer, and a catalytically active metal to decrease concentration of hydrocarbons, carbon monoxide, and nitrogen oxides in exhaust gas during stoichiometric, rich, and lean conditions, wherein a molar ratio of metal in the monolayers to metal in the centers is between about 0.01 and 0.2.