Ionic Liquid Adsorption for Recycled BHET Hue Improvement
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Solution Overview
Problem
Conventional chemical recycling methods for polyester fabrics require complex purification processes to produce high-quality recycled polyester pellets, resulting in low recovery rates and high costs due to poor heat resistance and recovery quality of bis(2-hydroxylethyl) terephthalate (BHET).
Innovation Solution
A method involving the use of ionic liquids to adsorb impurities from recycled polyester fabrics, where a chemical de-polymerization liquid is used to form a de-polymerization product, mixed with water, and an ionic liquid impurity adsorption material is dispersed to separate impurities, followed by crystallization and pelletization to improve the hue and heat resistance of BHET.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional purification methods (activated carbon or ion exchange resin) are used to remove impurities from BHET, then impurity removal is achieved, but the recovery quality of BHET is poor and heat resistance deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the purification system by using ionic liquids with specific functional groups (sulfonic acid, carboxylic acid, phosphoric acid) instead of conventional activated carbon or ion exchange resins. This parameter change in the adsorbent material enables effective impurity removal while preserving BHET quality and heat resistance, resolving the technical contradiction between purification effectiveness and material quality preservation.
2Object-affected harmful factors
If conventional purification processes are used, then impurities are removed, but the recovery cost increases and recovery rate decreases
Solution Approach 1:
The patent implements a recovery system where the ionic liquid adsorbent can be regenerated and reused multiple times. The spent ionic liquid is recovered from the aqueous phase, regenerated through appropriate treatment, and reused for subsequent purification cycles. This discarding and recovering approach significantly improves the BHET recovery rate and reduces processing costs compared to single-use conventional purification methods.
3Object-affected harmful factors
If conventional purification methods are used, then some impurities are removed, but the purification process becomes complicated and costs increase
Solution Approach 1:
The patent extracts the purification function into a single, specialized step using ionic liquid-based adsorbents added directly to the aqueous phase containing BHET and impurities. This extraction approach eliminates the need for multiple sequential purification operations (such as filtration, distillation, and repeated adsorption steps) required by conventional methods, thereby simplifying the overall purification process while maintaining effective impurity removal.
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 method effectively improves the recycling quality and heat resistance of BHET while reducing costs, achieving a recovery rate of at least 95% and maintaining high quality with improved 'L', 'a', and 'b' values after heat testing.
Implementation Method 1
dispersing an ionic liquid impurity adsorption material in a solid state into the aqueous phase liquid, so that the ionic liquid impurity adsorption material adsorbs the impurities originally present in the recycled polyester fabric
Implementation Method 2
implementing a separation operation, which includes using a centrifugal method and/or a filtering method to collect the ionic liquid impurity adsorption material in the solid state that are dispersed in the aqueous phase liquid
Implementation Method 3
implementing a de-polymerization operation, which includes using a chemical de-polymerization liquid to chemically de-polymerize the recycled polyester fabric to form a de-polymerization product, which includes the bis-2-hydroxylethyl terephthalate (BHET)
Data Source
AI summary
A method for improving hue of recycled bis-2-hydroxylethyl terephthalate by using ionic liquids including providing a recycled polyester fabric; using a chemical de-polymerization liquid to chemically de-polymerize the recycled polyester fabric to form a de-polymerization product; mixing the de-polymerization product with water to form an aqueous phase liquid; dispersing an ionic liquid impurity adsorption material into the aqueous phase liquid to adsorb impurities originally present in the recycled polyester fabric.