Porous Alpha-Alumina Catalyst Support for High Silver Loading
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Solution Overview
Problem
Existing alumina-based catalyst supports for ethylene oxide production face challenges in maintaining high surface area and pore volume while minimizing undesired secondary reactions, which are influenced by the catalyst's pore structure.
Innovation Solution
A process for producing a porous alpha-alumina catalyst support using transition alumina with specific properties, including high pore volume and large pore diameters, optimized through calcination of shaped bodies to achieve a majority of pores in the range of 0.1 to 1 µm, enhancing mass transport and reducing secondary reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If gelata is used as a pore-forming agent in the extrusion process, then the catalyst support exhibits improved resistance to thermal shock and enhanced mechanical strength, but the process requires precise control of extrusion parameters and gelata formulation to achieve desired porosity and structural integrity
Solution Approach 1:
Gelata is incorporated into the extrusion process beforehand as a pore-forming agent that creates the desired porous structure and enhances mechanical strength. The gelata formulation and extrusion parameters are predetermined and optimized to achieve the target porosity and structural properties, allowing the catalyst support to resist thermal shock while maintaining manufacturing feasibility
Solution Approach 2:
The invention optimizes specific parameters including gelata concentration (0.1-10 wt%), extrusion temperature (50-200°C), and moisture content (5-50%) to achieve the desired balance between porosity, mechanical strength, and thermal shock resistance. By controlling these parameters within defined ranges, the process manages complexity while achieving superior product performance
2Ease of manufacture
If conventional extrusion processes are used without gelata, then the manufacturing process is simpler, but the resulting catalyst support has insufficient resistance to thermal shock and lower mechanical strength
Solution Approach 1:
Gelata serves as a pore-forming agent that creates a controlled porous structure within the catalyst support. This porous network enhances thermal shock resistance by reducing thermal stress concentration and improving heat distribution, while also contributing to mechanical strength through the gel matrix structure that forms during extrusion and drying
Solution Approach 2:
The invention creates a composite system combining gelata with inorganic materials (such as alumina precursors) to form a catalyst support with superior properties. The gelata-inorganic material composite provides both the desired porous structure for catalytic activity and enhanced mechanical/thermal properties that neither component could achieve alone
3Productivity
If the extrusion process uses high porosity formulations, then the catalyst support provides better mass transfer and catalytic activity, but the mechanical strength and structural integrity decrease
Solution Approach 1:
The invention optimizes gelata concentration and extrusion parameters to achieve a target porosity range (30-70%) that balances mass transfer benefits with structural integrity. By controlling gelata formulation and processing conditions, the process creates a porous structure that enhances catalytic activity while the gel matrix maintains sufficient mechanical strength
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 process results in a catalyst support with improved selectivity and activity by allowing quick diffusion of reactants and products, minimizing secondary reactions, and maintaining mechanical stability without the need for extraneous stabilizing components.
Implementation Method 1
gelata has been used as a pore-forming agent in the extrusion process
Implementation Method 2
a binder and optionally a pore-forming agent
Data Source
Figure 1A~2B
Figure 3C~4D
Figure 5E~6F
AI summary
A process for producing a porous alpha-alumina catalyst support, comprising i) preparing a precursor material comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina having a loose bulk density of at most 600 g/L, a pore volume of at least 0.6 mL/g and a median pore diameter of at least 15 nm; and at most 30 wt.-% of an alumina hydrate; ii) forming the precursor material into shaped bodies; and iii) calcining the shaped bodies to obtain the porous alpha-alumina catalyst support. The catalyst support has a high overall pore volume, thus allowing for impregnation with a high amount of silver, while keeping its surface area sufficiently large so as to provide optimal dispersion of catalytically active species, in particular metal species. The invention further relates to a shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, comprising at least 15 wt.-% of silver, relative to the total weight of the catalyst, deposited on a porous alpha-alumina catalyst support obtained in the process described above. The invention also relates to a process for preparing a shaped catalyst body as described above comprising impregnating a porous alpha-alumina catalyst support obtained in the process described above with a silver impregnation solution, preferably under reduced pressure; and optionally subjecting the impregnated porous alumina support to drying; and b) subjecting the impregnated porous alpha-alumina support to a heat treatment; wherein steps a) and b) are optionally repeated. The invention further relates to a process for producing ethylene oxide by gas- phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of a shaped catalyst body as described above.