Alumina Composite Oxide for Exhaust Catalyst Support
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Solution Overview
Problem
Existing alumina-based composite oxides used as catalyst supports for exhaust gas purification are bulky, leading to increased coating layer thickness and pressure loss, while attempts to reduce thickness compromise purification performance and heat resistance.
Innovation Solution
Development of an alumina-based composite oxide with an initial crystallite diameter of 10 nm or less, specific surface area of 80 m2/ml or more, and a pore volume retention rate of 10% or more after calcination at 1200°C, featuring dispersed alumina and other metal oxide particles at the nano level, which maintains high heat resistance and reduces sintering of precious metal catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the coating layer is increased to increase catalyst amount, then purification performance is improved, but pressure loss increases and engine power output decreases
Solution Approach 1:
The patent changes the particle size parameter of the composite oxide from conventional large particles to ultrafine particles with diameter of 10 μm or less. This parameter change allows the coating layer to achieve the same catalyst amount with reduced thickness, thereby maintaining purification performance while reducing pressure loss and engine power consumption.
Solution Approach 2:
The patent utilizes porous composite oxide materials with controlled pore structure to increase the specific surface area. This allows more catalyst to be dispersed within a thinner coating layer, achieving high purification performance without increasing coating thickness and associated pressure loss.
2Object-generated harmful factors
If the thickness of the coating layer is decreased to reduce pressure loss, then pressure loss is reduced, but catalyst amount is reduced and purification performance becomes insufficient
Solution Approach 1:
The patent changes the particle size parameter to ultrafine particles (10 μm or less) and controls the pore size to 1 μm or less, which increases the surface area to volume ratio. This allows the same amount of catalyst to be packed into a thinner coating layer, maintaining purification performance while reducing pressure loss.
Solution Approach 2:
The patent creates a hierarchical pore structure with mesopores (2-50 nm) and macropores (0.5-5 μm) that allows efficient mass transport. The nested pore structure enables high catalyst loading density within the thin coating layer, ensuring sufficient purification performance despite reduced thickness.
3Temperature
If macropores (>50 nm) are increased to improve heat resistance, then heat resistance is improved, but pore volume increases making the composite oxide bulky
Solution Approach 1:
The patent changes the pore size distribution parameter by limiting macropores to 0.5-5 μm (reducing from >50 nm) and controlling total pore volume to 0.3 mL/g or less. This parameter change reduces the bulkiness of the composite oxide while maintaining heat resistance through controlled pore structure and ultrafine particle size.
Solution Approach 2:
The patent creates a simplified pore structure that copies only the essential heat resistance function without the excessive pore volume. By controlling pore size and distribution, the material achieves heat resistance with minimal pore volume, avoiding the bulky structure associated with large macropores.
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 composite oxide achieves a large specific surface area, excellent heat resistance, and reduced pore volume, enhancing catalyst support performance and reducing pressure loss, allowing for increased catalyst loading without increasing coating thickness.
Implementation Method 1
the alumina-based composite oxide after calcination at 1200° C. for 3 hours in air has a specific surface area of 10 m2/ml or more
Implementation Method 2
adding the plurality of aqueous solutions successively to an alkali aqueous solution, which can neutralize the total amount of the metallic acid salts, thereby generating precipitates
Data Source
AI summary
Provided is an alumina-based composite oxide having a large initial specific surface area and a small initial mean pore size, with excellent heat resistance of the specific surface area and pore volume; and a production method therefor. Specifically, provided is an alumina-based composite oxide wherein the initial crystallite diameter is 10 nm or less and the initial specific surface area is 80 m2/ml or more; after calcination at 1200° C. for 3 hours in air, the specific surface area is 10 m2/ml or more; the initial mean pore size is 10 nm or more and 50 nm or less; and after calcination at 1200° C. for 3 hours in air, the pore volume retention rate is 10% or more, which is determined by (P1/P0)×100 wherein P0 represents an initial pore volume (ml/g), and P1 represents a pore volume (ml/g) after calcination at 1200° C. for 3 hours in air.