Sulfolane Extractive Distillation for EG–EGDA Azeotrope Separation
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Solution Overview
Problem
Existing methods struggle to efficiently separate ethylene glycol (EG) and ethylene glycol diacetate (EGDA) due to their formation of azeotropic mixtures, leading to low purity and high production costs, especially when using toluene or benzene as entrainers.
Innovation Solution
Employing sulfolane as an entrainer in a two-stage distillation process involving an extractive distillation tower and an entrainer recovery tower, with specific operating conditions and plate configurations to achieve high purity separation of EG and EGDA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation is used to separate EG and EGDA, then the separation process is simple, but the purity of products cannot reach high levels due to azeotropic mixture formation
Solution Approach 1:
The patent introduces a third component (entrainer) as an intermediary substance to facilitate the separation of EG and EGDA. The entrainer selectively interacts with one component of the azeotropic mixture, disrupting the azeotrope and enabling high-purity separation through distillation. This mediator approach transforms an otherwise intractable separation problem into a solvable process.
Solution Approach 2:
The patent employs extractive distillation which involves changing the physical-chemical parameters of the system by introducing an entrainer with specific properties (boiling point, selectivity). This parameter change allows the separation of components that cannot be separated by conventional distillation alone, achieving high purity products despite the added process complexity.
2Manufacturing precision
If toluene is used as extractant to separate EG and EDGA, then the separation effectiveness is improved, but the input cost increases and specific operating conditions are not disclosed
Solution Approach 1:
The patent seeks to replace expensive extractants like toluene with cheaper alternatives. The entrainer used in this patent is selected to be less costly than toluene while maintaining or improving separation effectiveness. This reduces the input cost associated with the extractant, making the process more economically viable.
Solution Approach 2:
The patent optimizes operating parameters including the ratio of entrainer to feed (5-7:1), tower pressures (7-8 kPa at top of extractive distillation tower), and temperatures (120-130°C at top, 160-170°C at bottom) to achieve high purity separation while controlling costs. These parameter specifications provide a complete, reproducible process.
3Manufacturing precision
If excess acetic acid is added to make EG completely converted, then the azeotropic mixture problem is solved, but the input cost increases and the process becomes more complicated with additional reactors
Solution Approach 1:
Instead of adding more reaction steps or excess reagents, the patent extracts the separation problem from the reaction process. By using extractive distillation with an entrainer, the patent separates EG and EGDA directly from the reaction mixture without requiring complete conversion through excess acetic acid or additional reactors. This decouples the reaction and separation functions.
Solution Approach 2:
The patent changes the separation approach from chemical conversion (using excess acetic acid) to physical separation (extractive distillation). This parameter change in the separation mechanism avoids the need for additional reactors and excess reagents, simplifying the overall process while maintaining high product purity.
4Manufacturing precision
If extractive distillation with sulfolane is used to achieve high purity separation, then the purity and yield of products are improved, but the energy consumption and process complexity increase
Solution Approach 1:
The patent optimizes distillation parameters including operating pressure (7-8 kPa), temperatures (120-130°C at top, 160-170°C at bottom), and entrainer-to-feed ratio (5-7:1) to minimize energy consumption while achieving high purity separation. These optimized parameters reduce the energy penalty associated with extractive distillation compared to conventional approaches.
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 method achieves EG and EGDA purities of 99.50% and 99.90% respectively, with improved yield and reduced energy consumption, while minimizing entrainer loss and process costs.
Implementation Method 1
obtaining the EG and a mixture of the EDGA and the sulfolane through separating a mixture of the EG and the EDGA under an action of the sulfolane by an extractive distillation tower
Implementation Method 2
utilizing the feature that EG is difficult to dissolve in toluene while the EDGA is easily to dissolve in the toluene
Implementation Method 3
obtaining the EDGA and the sulfolane through separating the mixture of the EDGA and the sulfolane by an entrainer recovery tower
Implementation Method 4
obtaining recycled sulfolane through cooling the sulfolane by a heat exchanger
Implementation Method 5
cooling the sulfolane by a heat exchanger, and mixing the recycled sulfolane with fresh sulfolane
Data Source
AI summary
Method for separating ethylene glycol (EG) and ethylene glycol diacetate (EGDA) with sulfolane entrainer, including: obtaining EG and a mixture of EGDA and sulfolane through separating a mixture of EG and EGDA under an action of sulfolane by an extractive distillation tower; obtaining EGDA and sulfolane through separating the mixture of the EGDA and the sulfolane by an entrainer recovery tower; and obtaining recycled sulfolane through cooling the sulfolane by a heat exchanger, and mixing the recycled sulfolane with fresh sulfolane and circulating into the extractive distillation tower for recycling. Through the method, a yield of the EG is greater than or equal to 99.50% and a mass purity of the EG is greater than or equal to 99.50%, and a yield of the EGDA is greater than or equal to 99.80% and a mass purity of the EGDA is greater than or equal to 99.90%.