Hollow Spherical Catalyst With Internal Fluidization for Fixed Beds
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Solution Overview
Problem
Existing fixed-bed and fluidized-bed reactors face challenges in material mixing, mass transfer, and heat transfer, leading to inefficient catalytic processes and catalyst loss, necessitating a novel internally fluidizable catalyst particle for fixed-bed reactors to combine their advantages and reduce active component losses.
Innovation Solution
A hollow spherical catalyst is prepared using a coaxial dual-dropper forming apparatus, combining precious metal nanopowder with an aluminum oxide carrier, forming a mesoporous structure through aging, calcination, and reduction processes to ensure smooth reactant diffusion and full contact with active components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fluidized bed reactor is used to increase contact areas between heterogeneous components, then catalytic efficiency is improved, but catalyst particles suffer from severe collisions and crushing, causing active components to be lost and difficult to recycle
Solution Approach 1:
The catalyst system is segmented into mobile inner cores (precious metal nanoparticles) and fixed outer shells (alumina). This segmentation allows the inner core to benefit from fluidized bed mixing and contact while the outer shell provides mechanical protection against crushing, resolving the contradiction between catalytic efficiency and particle strength.
Solution Approach 2:
The precious metal nanopowder is nested inside the hollow alumina spherical shell, creating a core-shell structure. This nesting allows the catalyst to combine the advantages of both fixed-bed (mechanical strength, recyclability) and fluidized-bed (mixing, contact area) reactors, as the inner nanopowder can move freely within the constrained shell volume.
2Ease of operation
If a fixed-bed reactor is used with immobile catalyst, then structure is simple and operations are convenient, but material mixing and mass transfer are difficult
Solution Approach 1:
The catalyst particles are designed with dynamic inner cores (precious metal nanopowder) that can move and fluidize within the hollow shell during reaction. This dynamic behavior improves mass transfer and material mixing while the overall particle remains fixed in the bed, maintaining operational simplicity.
Solution Approach 2:
The alumina shell is designed with a porous structure containing channels and cavities that facilitate mass transfer and diffusion of reactants and products. The porous structure allows efficient material exchange while maintaining the fixed-bed configuration and operational simplicity.
3Manufacturing precision
If hollow spheres of aluminum oxide are prepared using carbon microspheres as templates, then nanometer-level hollow spheres are obtained, but millimeter-level carriers suitable for industrial fixed bed are not achieved
Solution Approach 1:
The synthesis parameters are changed from nanometer-scale conditions to millimeter-scale conditions. The emulsion dropwise addition method with controlled coalescence allows formation of hollow spheres in the millimeter range while maintaining the porous shell structure, achieving both structural control and appropriate size for industrial application.
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 catalyst achieves a micro-fluidization reaction system, enhancing catalytic efficiency by ensuring smooth diffusion and full contact with reactants and products, combining the advantages of fixed-bed and fluidized-bed reactors while reducing catalyst losses.
Implementation Method 1
ensure smooth diffusion and full contact with reactants and products
Implementation Method 2
internal fluidization of particles
Data Source
AI summary
A hollow spherical catalyst for a fixed bed with internal fluidization of particles and a method for preparing the same. The preparation method includes: fully mixing precious metal nanopowder with an organic oil phase to form an internal oil phase; preparing a gel ball of an oil-in-water structure by taking an aluminum oxide molding solution as an outer aqueous phase using an independently researched and developed coaxial dual-dropper forming apparatus; and then preparing a hollow aluminum oxide catalyst containing precious metal powder from the gel ball through processes of aging, calcination, and reduction. The resulting catalyst is expressed as X@Al2O3, where the precious metal nanopowder X is wrapped inside hollow Al2O3, and the catalyst has an outer diameter of 1.5-5.0 mm, a shell pore diameter (aluminum oxide) of 10-50 nm, and the precious metal nanopowder sized 200-500 nm.