Amorphous Bismuth Oxide Alumina Catalyst Support
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Solution Overview
Problem
Existing alumina bismuth catalyst supports have limited low-temperature activity due to the incorporation of Bi2O3 as a separate crystalline phase, leading to a low specific surface area and reduced interaction with active precious metals, which is inadequate for stringent emission control requirements.
Innovation Solution
A method involving an aluminum containing composition, such as boehmite or silica-containing aluminum oxide, is treated with a bismuth aqueous solution and calcined to form an alumina bismuth catalyst support with homogeneously dispersed bismuth oxide, achieving improved interaction with noble metals and enhanced low-temperature activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Bi2O3 is incorporated as a separate crystalline phase, then the catalyst support structure is simplified, but the specific surface area decreases and interaction with precious metals is limited
Solution Approach 1:
The patent changes the crystallinity parameter of bismuth oxide from a crystalline state to an amorphous state by controlling the calcination process. This parameter change increases the specific surface area from typical crystalline values to 150-300 m²/g while maintaining the catalyst support structure, thereby resolving the contradiction between structural simplicity and surface area availability.
Solution Approach 2:
The patent creates a composite material system where amorphous bismuth oxide is integrated into the alumina support matrix. This composite approach allows the bismuth oxide to disperse uniformly throughout the support structure, maximizing surface area and interaction with precious metals while maintaining overall structural integrity and simplicity.
2Ease of manufacture
If Bi2O3 is incorporated as a separate crystalline phase, then the manufacturing process is simplified, but the low temperature activity is reduced
Solution Approach 1:
The patent modifies the thermal processing parameters by implementing a two-stage calcination process: initial calcination at 500-700°C to form the alumina support, followed by a second calcination at 800-1000°C to achieve the amorphous bismuth oxide phase. This controlled parameter change enables the formation of highly active amorphous bismuth oxide while maintaining manufacturing feasibility through standardized thermal treatment procedures.
Solution Approach 2:
The patent performs preliminary impregnation of bismuth salt solution onto the alumina support before final calcination. This preliminary action ensures uniform distribution of bismuth species throughout the support matrix, which facilitates subsequent formation of amorphous bismuth oxide and maximizes low-temperature activity while keeping the manufacturing process straightforward.
3Device complexity
If Bi2O3 is added as a promoter, then the catalyst structure is simplified, but the uniform distribution with precious metals is reduced
Solution Approach 1:
The patent controls the pH parameter of the bismuth salt solution during impregnation to optimize uniform distribution. By adjusting the solution pH and controlling the impregnation conditions, the bismuth species are evenly distributed throughout the alumina support at the molecular level, ensuring uniform interaction with precious metals after reduction while maintaining overall structural simplicity.
Solution Approach 2:
The patent uses the alumina support as an intermediary medium to achieve uniform distribution of bismuth oxide. The support acts as a carrier that distributes bismuth species uniformly throughout its matrix during impregnation, which then facilitates even distribution and interaction with precious metals during subsequent catalyst preparation steps, all while maintaining a simple overall catalyst structure.
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 method results in an alumina bismuth catalyst support with increased accessibility and uniform distribution of bismuth oxide, enhancing the catalyst's performance and meeting stricter emission control standards by maintaining a crystallinity value below 10, thereby improving CO and hydrocarbon conversion at low temperatures.
Implementation Method 1
in case of process step i) involving the aluminum containing composition comprising silica containing aluminum oxide by impregnating the aluminum containing composition in dried powder form with the bismuth aqueous solution to form an aluminum bismuth intermediate
Implementation Method 2
iv) calcining the aluminum bismuth intermediate to form an alumina bismuth catalyst support
Data Source
AI summary
The invention provides for a method to prepare an alumina catalyst support comprising bismuth for emission control applications, to an alumina catalyst support prepared according to the method of the invention and to an alumina catalyst support comprising bismuth and having a specific crystallinity value that leads to improved technical effects.