Recycled Ethylene Glycol Purification for High-Purity BHET
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing bis(2-hydroxyethyl) terephthalate from recycled ethylene glycol suffer from the accumulation of acetate-based compounds, which are difficult to separate and degrade the quality of the final product due to similar boiling points with ethylene glycol, leading to impurities and reduced purity.
Innovation Solution
A process involving depolymerization of waste polyester using glycolysis, followed by distillation to separate ethylene glycol, removal of acetate-based compounds through side draw purging in a multi-stage distillation column, and reuse of purified ethylene glycol for continuous glycolysis, ensuring high purity and quality of bis(2-hydroxyethyl) terephthalate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ethylene glycol is reused in continuous glycolysis process, then cost efficiency is improved, but acetate-based compounds accumulate causing product quality deterioration
Solution Approach 1:
The patent extracts and removes acetate-based compounds from the recycled ethylene glycol through a specific purification step. This extraction process eliminates the harmful impurities that would otherwise accumulate and degrade product quality, allowing continuous reuse of ethylene glycol without compromising manufacturing precision.
Solution Approach 2:
The patent changes the physical parameters (temperature, pressure) during the purification process to selectively separate acetate-based compounds from ethylene glycol. By controlling these parameters, the system removes impurities while preserving the ethylene glycol quality, enabling sustained cost efficiency through reuse.
2Manufacturing precision
If multi-stage distillation is used to remove acetate-based compounds, then separation effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary purification step between the glycolysis reactor and the distillation column. This intermediary stage pre-treats the ethylene glycol stream, reducing the burden on the distillation column and enabling effective separation with fewer stages, thus balancing separation effectiveness with device complexity.
3Manufacturing precision
If side draw purging is applied at specific fraction, then acetate compound removal is improved, but process complexity increases
Solution Approach 1:
The patent applies preliminary action by performing side draw purging at a specifically predetermined fraction in the distillation column. This pre-planned removal point is optimized to eliminate acetate-based compounds at the most effective location, achieving high removal efficiency without requiring complex real-time control adjustments.
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 process effectively prevents the concentration of acetate-based compounds, resulting in bis(2-hydroxyethyl) terephthalate with excellent purity and quality, suitable for producing environmentally friendly polyester products with high melting points.
Implementation Method 1
distilling the crude bis(2-hydroxyethyl) terephthalate solution to separate a distillate comprising ethylene glycol
Implementation Method 2
removing an acetate-based compound from the distillate to recover the ethylene glycol
Data Source
AI summary
A method for producing bis(2-hydroxyethyl)terephthalate is disclosed. The method includes recovering and reusing ethylene glycol with an acetate removed, after the glycolysis of a waste polyester. According to the method, an acetate is not concentrated even though ethylene glycol is reused in a continuous process, leading to bis(2-hydroxyethyl)terephthalate with excellent purity and quality.