Exhaust Catalyst with Cerium-Zirconium Composite Support
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current diesel oxidation catalysts face challenges in achieving high hydrothermal stability and low-temperature performance, particularly when subjected to harsh automotive emissions environments, and increasing precious metal loading is cost-prohibitive.
Innovation Solution
A catalyst comprising an oxide support of silicon or aluminum oxide, with a cerium or zirconium oxide coating, and nanoparticles of palladium or platinum, designed to maintain performance even after hydrothermal aging, achieving high conversion rates of CO, hydrocarbons, and NOx at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If precious metal loading (e.g., Pt) is increased to improve low-temperature performance, then low-temperature conversion efficiency is improved, but cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst support by incorporating specific ratios of cerium oxide (3-20 wt%) and zirconium oxide (3-20 wt%) along with aluminum oxide, creating a multi-component oxide system that enhances low-temperature catalytic activity without requiring increased precious metal loading. This compositional parameter change allows maintaining high conversion efficiency at lower temperatures while controlling precious metal content at economical levels (0.1-4 wt% Pd or Pt).
Solution Approach 2:
The patent creates a composite oxide support material combining aluminum oxide, cerium oxide, and zirconium oxide in specific proportions. This composite structure synergistically enhances both low-temperature catalytic performance and hydrothermal stability, allowing effective pollutant conversion at temperatures below 150°C without needing excessive precious metal loading. The composite material approach resolves the contradiction by providing intrinsic catalytic activity that reduces dependence on precious metal quantity.
2Productivity
If catalyst materials are designed for enhanced low-temperature oxidation performance using novel materials (gold, silver, copper, manganese, or iron nanoparticles), then low-temperature conversion is improved, but hydrothermal stability deteriorates in harsh automotive emissions environments
Solution Approach 1:
The patent employs a composite oxide support system combining aluminum oxide, cerium oxide, and zirconium oxide that provides both low-temperature catalytic activity and high hydrothermal stability. The synergistic interaction among these oxides creates a stable framework that resists phase transformation and maintains structural integrity under hydrothermal aging conditions (800-900°C for 16 hours), while still enabling effective low-temperature oxidation of pollutants. This composite approach resolves the contradiction between novel material activity and thermal stability.
Solution Approach 2:
The patent optimizes the compositional parameters of the oxide support by controlling the weight percentages of cerium oxide (3-20 wt%), zirconium oxide (3-20 wt%), and aluminum oxide (balance), creating a stable crystalline structure that maintains hydrothermal stability. The specific parameter range ensures sufficient low-temperature activity while preventing excessive phase transformation at high temperatures, thus resolving the contradiction between low-temperature performance enhancement and hydrothermal stability.
3Reliability
If Pd/ZrO2 is used to achieve thermal stability through strong interaction, then thermal stability is improved, but performance loss occurs due to ZrO2 phase transformation
Solution Approach 1:
The patent transitions from a binary Pd/ZrO2 system to a ternary composite support of aluminum oxide, cerium oxide, and zirconium oxide. This composite structure stabilizes the zirconium oxide phase through interaction with cerium oxide and aluminum oxide, preventing harmful phase transformations at high temperatures. The multi-component system maintains thermal stability while preserving oxidation performance by creating a more robust support framework that resists structural degradation under hydrothermal aging conditions.
Solution Approach 2:
The patent changes the support composition parameters by adding cerium oxide (3-20 wt%) to the Pd/ZrO2 system, creating a Pd/Ce-Zr-Al mixed oxide catalyst. This compositional modification stabilizes the zirconium oxide phase and prevents performance loss due to phase transformation. The optimized parameter range of cerium and zirconium oxides ensures both thermal stability and maintained oxidation performance after aging at 800-900°C for 16 hours.
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 exceptional hydrothermal stability and low-temperature performance, achieving over 90% conversion of pollutants at temperatures as low as 150°C, maintaining effectiveness after aging, and reducing the need for high precious metal loading.
Implementation Method 1
A strong interaction between Pd and ZrO2 resulted in a greater thermal stability
Implementation Method 2
nanoparticles containing elemental palladium or platinum in contact with at least component (ii), wherein surfaces of the nanoparticles of elemental palladium or palladium are exposed and accessible to the fuel combustion exhaust
Data Source
AI summary
A catalyst for treating fuel combustion exhaust, the catalyst comprising the following components: (i) an oxide support comprising silicon oxide, aluminum oxide, or combination of silicon and aluminum oxides; (ii) cerium oxide, zirconium oxide, or a combination of cerium and zirconium oxides in contact with said oxide support; and (iii) nanoparticles comprising elemental palladium or platinum in contact with at least component (ii), wherein said palladium or platinum is present in an amount of 0.1-4 wt. % by weight of the particles, and wherein surfaces of said nanoparticles of elemental palladium or palladium are exposed and accessible to said fuel combustion exhaust. Methods of producing and using the catalyst are also described.