Agglomerated Zeolite X Adsorbents for Para-Xylene Separation
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Solution Overview
Problem
Agglomerated zeolite adsorbents used for separating para-xylene from C8 aromatic cuts face a compromise between achieving optimal adsorption capacity and mechanical resistance, with existing methods either sacrificing mechanical strength for higher adsorption or vice versa.
Innovation Solution
Developing agglomerated zeolite adsorbents with a specific composition and structure, including zeolite X crystals with a number average diameter less than 1.7 µm, a Si/Al atomic ratio between 1.00 and 1.50, a non-zeolite phase content between 2% and 5% by weight, and optimized barium and potassium oxide content, to balance adsorption capacity and mechanical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If zeolite adsorbents are used in powder form to maximize adsorption capacity, then adsorption properties are improved, but pressure losses during handling increase significantly
Solution Approach 1:
The zeolite is divided into small crystals (number average diameter less than 1.7 µm) and then agglomerated into larger particles. This segmentation allows the internal surface area of small crystals to be preserved for adsorption while the external agglomerate structure reduces pressure losses during handling.
Solution Approach 2:
Small zeolite crystals are nested within an agglomerate structure formed by a binder. The small crystals provide the adsorption function while being contained within a larger agglomerate that provides mechanical strength and reduces pressure losses during fluid flow.
2Strength
If agglomerates are formed with binder to improve mechanical strength, then mechanical resistance is improved, but adsorption properties are reduced due to inert binder material
Solution Approach 1:
The binder material undergoes a chemical transformation through zeolithization treatment, changing from an inert organic binder to an active zeolitic phase. This parameter change converts the binder from a non-functional component to an active adsorption material, maintaining mechanical strength while restoring adsorption capacity.
Solution Approach 2:
The inert binder, which initially reduces adsorption capacity, is transformed through zeolithization into active zeolite material. The harmful effect of the inert binder is converted into a benefit by transforming it into a functional adsorption component that contributes to both mechanical strength and adsorption capacity.
3Quantity of substance
If zeolithization is performed to convert binder into active zeolite, then adsorption capacity is improved, but mechanical resistance may be compromised
Solution Approach 1:
The zeolithization process parameters (temperature, time, alkaline solution concentration) are optimized to achieve partial conversion of the binder. This controlled parameter change ensures that enough binder is converted to zeolite to provide adequate adsorption capacity while retaining sufficient unconverted binder to maintain the agglomerate structure and mechanical resistance.
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 adsorbents exhibit enhanced selectivity, material transfer properties, and mechanical strength, making them suitable for efficient separation of para-xylene in liquid phase processes like simulated counter-current processes.
Implementation Method 1
The use of agglomerated zeolite adsorbents consisting of X or Y zeolites comprising, in addition to sodium cations, barium, potassium or strontium ions, alone or in mixtures, to selectively adsorb para-xylene in a mixture of aromatic hydrocarbons
Implementation Method 2
zeolite adsorbents based on zeolite X crystals... to selectively adsorb para-xylene in a mixture of aromatic hydrocarbons
Implementation Method 3
the sodium cations can be replaced (exchanged) in whole or in part with other cations, for example barium or barium and potassium
Data Source
Figure 1
AI summary
The present invention relates to zeolitic adsorbents based on small agglomerated crystals of zeolite X comprising barium, combining optimum properties in terms of selectivity and of mechanical strength. These adsorbents have applications in the separation of fractions of aromatic C8 isomers and in particular xylenes, in the separation of substituted toluene isomers, such as nitrotoluene, diethyltoluene or toluenediamine, in the separation of cresols, and in the separation of polyhydric alcohols, such as sugars.