Tableted Alpha-Alumina Catalyst Support for Ethylene Oxide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of alpha-alumina catalyst supports for ethylene oxide synthesis faces challenges such as difficulty in controlling particle size and shape during extrusion, leading to geometrical aberrations and reduced catalyst performance due to low surface area and high brittleness, which affects selectivity and longevity in gas-phase oxidation processes.
Innovation Solution
A tableted alpha-alumina catalyst support is developed with a high alpha-alumina content, optimized pore structure, and precise geometry, achieved by forming a free-flowing feed mixture with transition alumina and subsequent heat treatment, ensuring high geometrical precision, pore volume, and surface area, thereby improving catalyst performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If extrusion process is used to produce alpha-alumina catalyst supports, then shaped bodies can be obtained, but geometrical precision deteriorates due to bending, curling, and shape deformation
Solution Approach 1:
The patent changes the physical-chemical parameters of the alumina material by controlling the crystalline phase composition (ratio of alpha-alumina to transition alumina) and particle size distribution. This transforms the material from a malleable state during forming to a rigid state during drying, preventing deformation while maintaining shapeability during manufacturing.
Solution Approach 2:
The patent performs preliminary classification of alumina particles by size before mixing with binders. This preliminary action ensures uniform particle distribution and consistent green strength throughout the shaped body, preventing differential shrinkage and deformation during subsequent drying and firing processes.
2Reliability
If alpha-alumina content is increased to improve thermal stability, then catalyst longevity improves, but surface area decreases reducing catalyst performance
Solution Approach 1:
The patent creates a composite material system combining alpha-alumina (for thermal stability and mechanical strength) with transition alumina (for high surface area and porosity). This composite approach allows the catalyst support to simultaneously achieve longevity under harsh reaction conditions and high catalytic activity through increased surface area for active site dispersion.
Solution Approach 2:
The patent creates different local regions within the catalyst support structure with different alumina phase compositions. The outer regions may have higher alpha-alumina content for mechanical stability, while inner regions maintain higher transition alumina content for surface area, optimizing both longevity and catalytic performance locally throughout the structure.
3Area of stationary object
If particle size is reduced to increase surface area, then catalyst activity improves, but mechanical strength decreases increasing brittleness
Solution Approach 1:
The patent optimizes the particle size distribution parameters by classifying alumina into specific size ranges (fine particles <10 μm for surface area, coarse particles 10-50 μm for structural framework). This parameter optimization allows small particles to provide surface area while larger particles form a mechanical framework that prevents excessive brittleness.
Solution Approach 2:
The patent creates a composite particle system where fine alumina particles (providing surface area) are embedded within a matrix of coarser alumina particles and binder material (providing mechanical strength). This composite structure allows the catalyst support to simultaneously achieve high surface area for catalytic activity and sufficient mechanical strength to reduce brittleness during handling and operation.
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 tableted catalyst support exhibits improved geometrical precision, increased pore volume, and surface area, leading to enhanced selectivity and longevity, reducing pressure loss and consecutive reactions, and allowing for efficient diffusion of reactants and products, thus improving the overall efficiency of ethylene oxide production.
Implementation Method 1
subsequent heat treatment, ensuring high geometrical precision, pore volume, and surface area
Implementation Method 2
forming a free-flowing feed mixture with transition alumina and subsequent heat treatment
Implementation Method 3
allowing for efficient diffusion of reactants and products
Data Source
AI summary
A tableted catalyst support, characterized by an alpha-alumina content of at least 85 wt.-%, a pore volume of at least 0.40 mL/g, as determined by mercury porosimetry, and a BET surface area of 0.5 to 5.0 m2/g. The tableted catalyst support is an alpha-alumina catalyst support obtained with high geometrical precision and displaying a high overall pore volume, thus allowing for impregnation with a high amount of silver, while exhibiting a surface area sufficiently large so as to provide optimal dispersion of catalytically active species, in particular metal species. The invention further provides a process for producing a tableted alpha-alumina catalyst support, which comprises i) forming a free-flowing feed mixture comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina; ii) tableting the free-flowing feed mixture to obtain a compacted body; and iii) heat treating the compacted body at a temperature of at least 1100° C., preferably at least 1300° C., more preferably at least 1400° C., in particular at least 1450° C., to obtain the tableted alpha-alumina catalyst support. The invention moreover relates to a compacted body obtained by tableting a free-flowing feed mixture which comprises, 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, as determined, and a median pore diameter of at least 15 nm. The invention moreover 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 the tableted alpha-alumina catalyst support. The invention moreover relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of the shaped catalyst body.