Eggshell Catalyst Coating via Horizontal Mixer Froude Control
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Solution Overview
Problem
Existing eggshell catalysts lack high pore volume and abrasion resistance, which are crucial for effective heterogeneously catalyzed partial gas phase oxidation processes.
Innovation Solution
A process for producing eggshell catalysts involves coating a geometric shaped support body with catalytically active multielement oxides and liquid binders in a horizontal mixer, where the Froude number is controlled between 0.0040 and 0.1200, allowing for a coherent and compact coating that enhances pore volume and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing eggshell catalysts are produced using conventional coating methods, then the catalyst structure is formed, but the pore volume is insufficient and abrasion resistance is low
Solution Approach 1:
The invention changes the physical parameters of the coating process by controlling the Froude number (Fr) within a specific range (0.0040 to 0.1200, preferably 0.0080 to 0.1000). This parameter control optimizes the coating formation, creating a structure with both high pore volume and improved abrasion resistance. The Fr number governs the balance between centrifugal forces and gravitational forces during coating, enabling precise control over coating thickness and porosity structure.
Solution Approach 2:
The invention employs dynamic coating conditions using a horizontal mixer where the support bodies are tumbled and coated under controlled rotational speeds. This dynamic process allows the coating material to be uniformly distributed while maintaining the porous structure. The continuous motion and varying forces during mixing create optimal conditions for forming a coherent yet porous coating layer that adheres strongly to the support body.
2Productivity
If the coating is applied to maximize catalyst loading, then the catalytic activity increases, but the abrasion resistance decreases
Solution Approach 1:
By precisely controlling the Froude number during coating, the invention achieves an optimal balance between catalyst loading and coating integrity. The Fr number range specified enables the formation of a coating that is sufficiently thick to provide high catalytic activity while maintaining the structural coherence needed for abrasion resistance. This parameter optimization prevents both under-coating and over-coating problems.
Solution Approach 2:
The invention uses composite coating materials comprising catalytically active multielement oxides (such as Mo-V-Cu oxides) combined with binders. This composite structure provides both the catalytic functionality and the mechanical strength needed for abrasion resistance. The multielement oxide composition enhances catalytic activity while the binder matrix provides structural integrity, creating a synergistic effect that satisfies both requirements simultaneously.
3Productivity
If a thick coating is applied to increase active composition content, then the catalytic activity improves, but the pore volume decreases
Solution Approach 1:
The invention specifically designs the coating to have a porous structure by controlling the coating process parameters. The horizontal mixing at controlled Froude numbers creates a coating with interconnected pores that maintain high pore volume even at increased active composition content. This porous structure allows reactants to access the catalytic sites deep within the coating, maintaining high catalytic activity while preserving pore volume for mass transfer.
Solution Approach 2:
The control of Froude number during coating is critical for achieving the desired pore structure. By optimizing this dimensionless number, the process creates a coating thickness and density profile that maximizes both catalytic activity and pore volume. The specific Fr range ensures that the coating is neither too dense (which would reduce pore volume) nor too thin (which would limit catalytic activity).
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 resulting eggshell catalysts exhibit improved pore volume and abrasion resistance, leading to increased catalytic activity and longevity in partial gas phase oxidation processes, such as the conversion of acrolein to acrylic acid.
Implementation Method 1
The rolling motion on the outer surface of the cylindrical or spherical shaped support bodies compacts it to form a coherent coating
Implementation Method 2
The first metering device appropriately corresponds to a nozzle, by means of which the rolling geometric shaped support bodies are sprayed with the liquid binder and moistened in a controlled manner
Implementation Method 3
one or more powders P and one or more liquid binders, wherein the powder(s) P, after the coating, is/are converted by thermal treatment to one or more catalytic reactive multielement oxides
Data Source
AI summary
A process for producing an eggshell catalyst, comprising the coating of the outer surface of a geometric shaped support body with a catalytically active multielement oxide or a powder P, wherein the powder P, after being coated, is converted by thermal treatment to a catalytically active multielement oxide, and one or more liquid binders, wherein the coating is conducted in a horizontal mixer and the Froude number during the coating in the horizontal mixer is from 0.0160 to 0.1200.