Binderless Zeolite X Adsorbent for Para-Xylene Separation
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Solution Overview
Problem
There is a need for improved adsorbents and processes to efficiently separate para-xylene from relatively impure mixtures of C8 alkylaromatic hydrocarbons, which typically contain other xylene isomers and ethylbenzene, as existing methods face limitations in selectivity and capacity.
Innovation Solution
The use of binderless adsorbents comprising zeolite X with a water content of 3% to 5.5% by weight, specifically with small-crystallite-size or nano-size zeolite X, which enhances adsorptive selectivity and mass transfer rates, overcoming conventional adsorbent limitations by modifying the crystallite size and silica to alumina molar ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional adsorbents comprising zeolite X and a non-selective binder are used, then the adsorbent structure is stable and easy to manufacture, but the adsorbent capacity and mass transfer rate are limited
Solution Approach 1:
The patent removes the non-selective binder component from the conventional adsorbent structure, creating a binderless adsorbent. This extraction of the binder eliminates the harmful effect of non-selective pores while maintaining the zeolite X crystal structure, thereby improving para-xylene capacity and mass transfer rate without compromising structural stability
Solution Approach 2:
The patent utilizes the natural porous structure of zeolite X crystals, optimizing the pore characteristics by removing binder material. The binderless design allows for improved pore accessibility and mass transfer while maintaining the selective adsorption properties of the zeolite framework
2Speed
If the crystallite size of zeolite X is reduced to improve mass transfer, then the mass transfer rate increases, but the mechanical strength and attrition resistance decrease
Solution Approach 1:
The patent optimizes the crystallite size parameter of zeolite X to achieve a balance between mass transfer rate and mechanical strength. By controlling the crystallite size within a specific range and removing the binder, the patent improves mass transfer while the binderless structure compensates for potential strength losses through enhanced pore accessibility
3Manufacturing precision
If the water content of the binderless adsorbent is increased to improve selectivity, then the adsorptive selectivity increases, but the capacity may be reduced
Solution Approach 1:
The patent optimizes the water content parameter of the binderless adsorbent to achieve optimal separation performance. By controlling water content within a specific range, the patent enhances the selectivity for para-xylene while maintaining adequate capacity, as the binderless structure provides more available pore volume compared to conventional binder-containing adsorbents
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 significantly improves para-xylene productivity and process economics by increasing adsorbent capacity and selectivity, achieving a 15-35% improvement in para-xylene productivity compared to conventional adsorbents, while maintaining desorbent strength and attrition properties.
Implementation Method 1
The invention relates to adsorbents that selectively adsorb para-xylene over at least one other C8 alkylaromatic compound present in a mixture
Implementation Method 2
an adsorbent comprising zeolite X
Data Source
AI summary
Adsorbents and methods for the adsorptive separation of para-xylene from a mixture containing at least one other C8 aromatic hydrocarbon (e.g., a mixture of ortho-xylene, meta-xylene, para-xylene, and ethylbenzene) are described. Suitable binderless adsorbents (e.g., formulated with the substantial absence of an amorphous material that normally reduces selective pore volume), particularly those with a water content from about 3% to about 5.5% by weight, improve capacity and/or mass transfer. These properties are especially advantageous for improving productivity in low temperature, low cycle time adsorptive separation operations in a simulated moving bed mode.