Agglomerated Zeolite Adsorbent Particle Size for Simulated Moving Bed Stability
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Solution Overview
Problem
The xylene separation process in simulated moving bed (LMS) faces challenges in maintaining long-term productivity due to the degradation of zeolite adsorbent particles, which is caused by mechanical stresses leading to the formation of fines and embankments on the surface of the bed, disrupting flow and reducing separation performance.
Innovation Solution
The process involves using agglomerated zeolite adsorbent particles with a specific particle size range (150 µm to 500 µm) and zeolite crystals with diameters between 0.1 µm and 1.2 µm, ensuring mechanical strength and preventing the formation of furrows or embankments, thereby maintaining performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the zeolite agglomerate has high adsorption capacity with maximum zeolite content, then the adsorption performance is improved, but the mechanical crush resistance decreases leading to formation of fines
Solution Approach 1:
The patent employs composite agglomerates consisting of zeolite crystals bound together by a binder material. This composite structure allows the agglomerate to maintain high zeolite content for adsorption capacity while the binder provides mechanical strength to resist crushing and prevent fine formation during operation.
2Speed
If the particle size of adsorbent particles is reduced to enhance mass transfer, then the transfer speed is improved, but the mechanical strength decreases and fines are formed
Solution Approach 1:
The patent segments the zeolite structure into two levels: fine zeolite crystals (0.1-2 µm) within agglomerates for high mass transfer, and larger agglomerate particles (150-500 µm) for mechanical strength. This hierarchical segmentation allows both fast intraparticle diffusion and resistance to mechanical degradation.
3Speed
If the zeolite crystals are made smaller to improve microporous transfer, then the mass transfer is enhanced, but the adsorption capacity is reduced due to water presence
Solution Approach 1:
The patent optimizes the size parameter of zeolite crystals to a specific range (0.1-2 µm) that balances microporous transfer and adsorption capacity. Additionally, the binder composition and agglomerate structure are adjusted to control water distribution, ensuring that smaller crystals maintain both fast transfer and adequate capacity.
4Speed
If the agglomerate size is reduced below 150 µm to improve transfer, then the mass transfer is enhanced, but embankments form on the bed surface disrupting flow
Solution Approach 1:
The patent establishes a minimum agglomerate size parameter of 150 µm that prevents embankment formation while maintaining adequate mass transfer. This size threshold ensures proper flow distribution across the bed surface and prevents the operational problems associated with finer particles.
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
This approach allows for high-purity production of paraxylene or metaxylene with improved productivity while preventing performance degradation, as evidenced by the absence of surface deformation and embankment formation in the adsorbent bed.
Implementation Method 1
by selective adsorption of a xylene isomer in the presence of a desorbent
Implementation Method 2
The adsorbed phase, enriched in para-xylene or meta-xylene depending on the zeolite used in the adsorbent, is desorbed under the action of a desorbent flow
Data Source
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AI summary
The invention relates to a method for separating xylenes by means of a simulated mobile bed using an agglomerated zeolitic adsorbent solid, preferably based on faujasite zeolite with a Si/Al ratio of between 1 and 6, said solid being used in the form of particles having a diameter of between 150 μm et 500 μm.