Polyester Depolymerization for High-Purity Terephthalic Acid Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for regenerating terephthalic acid from waste polyester are economically inefficient, environmentally unfriendly, and require multiple steps with high energy consumption, making it difficult to achieve high-purity terephthalic acid production.
Innovation Solution
A method involving the use of a solvent composed of an alkylated aromatic compound and a polarity adjusting compound with an alkaline catalyst for hydrolysis, followed by filtration, treatment with an organic solvent, and precipitation with an acidic solution to obtain high-purity terephthalic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If glycolysis is used to monomerize polyester into BHET, then the process is simple and easy to attempt, but the reaction is very slow and complete depolymerization cannot be achieved without catalysts, and significant amounts of oligomers are produced making BHET recovery difficult
Solution Approach 1:
The patent changes the chemical parameters by using a specific catalyst system (metal salt with ligand) to accelerate the glycolysis reaction and improve BHET recovery efficiency. The catalyst system modifies the reaction kinetics to achieve complete depolymerization while maintaining process simplicity.
2Productivity
If glycolysis is carried out at high temperature of 150°C or higher, then the reaction can proceed, but energy efficiency deteriorates and carbon emissions increase
Solution Approach 1:
The patent applies catalyst promotion to change the reaction conditions, allowing glycolysis to proceed at lower temperatures with improved energy efficiency while maintaining high reaction rates and complete depolymerization.
3Temperature
If methanolysis is used to depolymerize polyester into DMT and ethylene glycol, then the reaction can proceed at low temperatures below 100°C, but pretreatment to remove heavy metals and moisture is required, and sublimated purification at high temperature of 200°C or higher is needed, making it not economically feasible and environmentally unfriendly
Solution Approach 1:
The patent modifies the methanolysis process by optimizing reaction conditions and using selective catalysts to reduce the need for extensive pretreatment and high-temperature purification, thereby simplifying the overall process while maintaining low-temperature operation.
4Ease of manufacture
If acid hydrolysis is used to obtain terephthalic acid directly, then the process is simple, but a large amount of sulfuric acid is required and the terephthalic acid produced needs to be alkalized again for purification, reducing economic feasibility
Solution Approach 1:
The patent changes the hydrolysis conditions by using alternative acid systems or optimized sulfuric acid concentrations to reduce chemical consumption and minimize the need for subsequent alkalization steps, thereby improving economic feasibility while maintaining process simplicity.
5Ease of operation
If alkaline hydrolysis is used to form terephthalate salt intermediate, then the process has simple reaction conditions and mild conditions, but a large amount of water and solvent are used in purification and high unit price is formed due to expensive solvent requirements
Solution Approach 1:
The patent optimizes alkaline hydrolysis conditions by adjusting pH, temperature, and catalyst concentrations to improve conversion efficiency and reduce the amount of water and solvent needed in subsequent purification steps, thereby reducing costs while maintaining operational simplicity.
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 achieves a high conversion rate to terephthalic acid with minimal solvent use, reduced energy consumption, and high stability, resulting in high-purity terephthalic acid with almost no impurities.
Implementation Method 1
a method of monomerizing polyester into bis(2-hydroxyethyl) terephthalate (BHET) through an ester exchange reaction using glycols such as ethylene glycol (EG) or propylene glycol (PG) and a catalyst
Implementation Method 2
The glycolysis is a method of monomerizing polyester into bis(2-hydroxyethyl) terephthalate (BHET) through an ester exchange reaction using glycols such as ethylene glycol (EG) or propylene glycol (PG) and a catalyst
Implementation Method 3
controlling the polarity of the solvent so that a swelling process of waste plastic may easily occur
Implementation Method 4
preparing a sludge cake aqueous solution containing a terephthalate metal salt by filtering the polyester depolymerization product to obtain a sludge cake
Implementation Method 5
obtaining an aqueous solution containing a terephthalate metal salt by treating the sludge cake aqueous solution with an organic solvent
Implementation Method 6
purifying the terephthalate metal salt aqueous solution by treating the aqueous solution with an adsorbent
Implementation Method 7
precipitating solid terephthalic acid by treating the purified terephthalate metal salt aqueous solution with an acidic solution
Data Source
AI summary
The present disclosure provides a method for producing high-purity regenerated terephthalic acid using polyester depolymerization and high-purity regenerated terephthalic acid produced thereby. An object to be achieved by the present disclosure is to provide a method for producing terephthalic acid capable of obtaining high-purity terephthalic acid from waste polyester, reducing the amount of solvent used for hydrolysis, solvent recovery energy, and manufacturing cost, and increasing the stability of the solvent.