Zeolite adsorbents having a high external surface area and uses thereof
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Solution Overview
Problem
Existing gas adsorbent technologies face challenges with low volumetric efficiency, mechanical resistance, and high energy consumption due to the use of small particle sizes and inert binders, leading to inefficient gas separation and purification processes.
Innovation Solution
Development of zeolitic adsorbents with a high external surface area, specifically FAU-type zeolites, having a nitrogen adsorption surface area greater than 20 m2/g and a controlled non-zeolite phase content, combined with sodium exchange and specific Si/Al ratios, to enhance adsorption and desorption kinetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of adsorbent particles is reduced to improve mass transfer kinetics, then the diffusion of gases becomes faster, but the pressure drops in the adsorbers increase and energy consumption rises
Solution Approach 1:
The patent employs faujasite-type zeolites with a well-defined porous structure consisting of micropores and macropores. The micropores provide high adsorption capacity while the macropores facilitate rapid gas diffusion, eliminating the need to reduce particle size to improve kinetics. This hierarchical porosity allows maintaining larger particle sizes without sacrificing mass transfer performance, thereby reducing pressure drops and energy consumption.
Solution Approach 2:
The adsorbent is formulated as a composite material containing faujasite-type zeolite crystals dispersed in a binder matrix. The zeolite provides the active adsorption sites and porous structure, while the binder holds the crystals together in a mechanically stable form. This composite approach enables the use of optimized zeolite crystal sizes that balance diffusion efficiency with acceptable pressure drops, without requiring excessive size reduction.
2Speed
If the size of adsorbent particles is reduced to improve mass transfer kinetics, then the diffusion of gases becomes faster, but the mechanical resistance of the adsorbent decreases
Solution Approach 1:
The hierarchical porous structure of faujasite-type zeolites with micropores and macropores allows maintaining larger particle sizes that inherently possess better mechanical strength. The macropores enable sufficient gas diffusion without requiring extreme size reduction, thus preserving both kinetics and mechanical resistance.
Solution Approach 2:
The composite structure of zeolite crystals embedded in a binder matrix provides mechanical support to the adsorbent particles. This composite formulation enhances the mechanical resistance of the overall adsorbent material, allowing the use of particle sizes that optimize both mass transfer kinetics and structural integrity.
3Strength
If inert binders are used in adsorbent formulations to maintain mechanical strength, then the structural stability is improved, but the volumetric efficiency and adsorption capacity decrease
Solution Approach 1:
The faujasite-type zeolite possesses an intrinsic hierarchical porous structure with both micropores and macropores that provides high adsorption capacity and rapid mass transfer. This eliminates the need for excessive binder content to achieve acceptable performance, as the zeolite itself offers the required functional properties.
Solution Approach 2:
The patent optimizes the Si/Al ratio of the faujasite-type zeolite to tune the adsorption properties and enhance the adsorption capacity. By adjusting this compositional parameter, the zeolite achieves high volumetric efficiency without requiring large amounts of binder, thus improving the overall productivity of the adsorbent material.
4Ease of manufacture
If conventional adsorbents with low external surface area are used, then the manufacturing is simpler, but the adsorption kinetics and productivity are reduced
Solution Approach 1:
The faujasite-type zeolite with its hierarchical porous structure (micropores and macropores) inherently provides high external surface area and rapid mass transfer kinetics. This structure can be obtained through established hydrothermal synthesis methods, maintaining manufacturing feasibility while dramatically improving adsorption productivity.
Solution Approach 2:
The patent optimizes the Si/Al ratio of the faujasite-type zeolite to enhance adsorption capacity and kinetics. By adjusting this compositional parameter, the adsorbent achieves high productivity while maintaining compatibility with conventional manufacturing processes for zeolite synthesis.
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 zeolitic adsorbents demonstrate improved adsorption capacities and kinetics, reducing pressure drops and energy consumption while maintaining mechanical strength, thus enabling more efficient gas separation and purification processes.
Implementation Method 1
The invention relates to the use of zeolite adsorbent materials in the form of agglomerates comprising at least one faujasite-type zeolite, said adsorbents having a large external surface characterized by nitrogen adsorption, and a high micropore volume, for gas phase separation
Implementation Method 2
an external surface, measured by nitrogen adsorption and expressed in m2 per gram of adsorbent, greater than 20 m2.g-1
Data Source
AI summary
The present invention concerns the use, for gas separation, of at least one zeolite adsorbent material comprising at least one FAU zeolite, said adsorbent having an external surface area greater than 20 m2 ⋅ g-1, a non-zeolite phase (PNZ) content such that 0 < PNZ ≤ 30%, and an Si/Al atomic ratio of between 1 and 2.5. The invention also concerns a zeolite adsorbent material having an Si/Al ratio such that 1 ≤ Si/Al < 2.5, a mesoporous volume of between 0.08 cm3 ⋅ g-1 and 0.25 cm3 ⋅ g-1, a (Vmicro - Vmeso)/Vmicro ratio of between -0.5 and 1.0, non-inclusive, and a non-zeolite phase (PNZ) content such that 0 < PNZ ≤ 30%.