PET Recycling With Staged Mono-Ethylene Glycol Levels
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Solution Overview
Problem
Existing chemical recycling methods for polyethylene terephthalate (PET) are energy inefficient, ecologically unfriendly, have low throughput, and produce large amounts of degradation products, often requiring mixing with virgin PET to achieve high-quality recycled PET.
Innovation Solution
A method involving the use of varying organic compounds to depolymerize PET into oligomers, utilizing specific temperature and volume configurations to enhance impurity removal and increase the efficiency and purity of the recycling process, thereby extending equipment lifetime and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If PET is depolymerised to monomers using conventional chemical recycling methods, then the recycling process can produce chemical components for new PET, but the process requires long depolymerisation times and produces large amounts of degradation products that cannot be removed
Solution Approach 1:
The patent changes the depolymerisation parameters by using oligomers (2-20 repeating units) instead of complete monomer depolymerisation, and by controlling the water content (0.1-5 wt%) and temperature (180-220°C) to optimize the process. This resolves the contradiction by achieving sufficient depolymerisation to remove impurities while avoiding excessive depolymerisation that creates unremovable degradation products and requires extremely long times.
Solution Approach 2:
The patent applies partial depolymerisation to produce oligomers rather than complete depolymerisation to monomers. This partial action is sufficient to remove impurities like sand and polyvinyl chloride while avoiding the excessive depolymerisation that leads to degradation products. The oligomers produced have 2-20 repeating units, which is a controlled partial depolymerisation state.
2Ease of manufacture
If conventional chemical recycling methods are used to recycle PET, then PET can be converted back to chemical components, but the process is very energy inefficient and ecologically unfriendly
Solution Approach 1:
The patent optimizes process parameters including temperature (180-220°C), water content (0.1-5 wt%), and depolymerisation time (0.5-10 hours) to achieve efficient recycling with reduced energy consumption. The use of oligomers instead of complete monomer depolymerisation reduces the energy required while maintaining recycling effectiveness.
Solution Approach 2:
The patent converts the potential harm of incomplete depolymerisation (which would leave impurities) into a benefit by using controlled partial depolymerisation to produce oligomers. This approach naturally removes impurities like sand and polyvinyl chloride through the depolymerisation process itself, eliminating the need for separate removal steps and reducing overall energy consumption.
3Productivity
If conventional chemical recycling methods are used to recycle PET, then PET can be converted to chemical components, but the process has low throughput
Solution Approach 1:
The patent optimizes depolymerisation parameters including temperature (180-220°C), water content (0.1-5 wt%), and time (0.5-10 hours) to achieve high throughput while controlling degradation product formation. The controlled partial depolymerisation to oligomers with 2-20 repeating units enables faster processing compared to complete monomer depolymerisation.
4Manufacturing precision
If PET is chemically recycled using conventional methods, then recycled PET can be produced, but the quality is often insufficient and requires mixing with virgin PET
Solution Approach 1:
The patent uses controlled depolymerisation parameters (temperature 180-220°C, water content 0.1-5 wt%, time 0.5-10 hours) to produce high-quality oligomers with 2-20 repeating units. This controlled process effectively removes impurities and produces oligomers of sufficient quality that can be used without or with minimal virgin PET mixing, improving manufacturing precision.
Solution Approach 2:
The patent applies partial depolymerisation to produce oligomers rather than complete depolymerisation to monomers. This partial action is sufficient to remove impurities while maintaining polymer quality, enabling the production of high-quality recycled PET that may not require mixing with virgin PET.
5Ease of manufacture
If conventional depolymerisation processes are used, then PET can be broken down to chemical components, but the equipment lifetime is reduced due to impurities in the feedstock
Solution Approach 1:
The patent converts the potential harm of feedstock impurities (sand, polyvinyl chloride) into a benefit by using controlled partial depolymerisation to oligomers. This process effectively removes these impurities through the depolymerisation reaction itself, protecting equipment from damage and extending equipment lifetime while maintaining process feasibility.
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 improves the purity and throughput of PET recycling, extends equipment lifetime, and reduces energy consumption and carbon footprint, producing high-quality PET oligomers and polymers with minimal virgin PET content.
Implementation Method 1
contacting the first polyester with water to remove at least one impurity from the first polyester
Implementation Method 2
contacting the first polyester with water to remove at least one impurity from the first polyester
Implementation Method 3
transporting the first polyester, and preferably at least a fraction of the first amount of the first organic compound, from the volume section V1 to a volume section V2
Implementation Method 4
reducing a weight average molar mass of the first polyester, preferably in the volume section V3, to obtain a first intermediate mixture
Implementation Method 5
contacting the first polyester with a first amount of a first organic compound in a volume section V1 to obtain a first initial mixture
Data Source
AI summary
One aspect is a method for producing a first intermediate product. A feedstock is provided that comprises a first polyester. The feedstock is contacted with a first amount of a first organic compound in a volume section V1 to obtain a first initial mixture. The first amount is in the form of a liquid. The first polyester is transported, and at least a fraction of the first amount of the first organic compound, from the volume section V1 to a volume section V2. The volume section V2 is at least partially filled with the first organic compound. A level of the first organic compound in the volume section V1 is at a height H1 from a floor, and a level of the first organic compound in the volume section V2 is at a height H2 from the floor. The first polyester is contacted with a further organic compound in a volume section V3, to obtain a further initial mixture. A weight average molar mass of the first polyester is reduced in the volume section V3, to obtain a first intermediate mixture. The first intermediate mixture comprisesa first intermediate product,the further organic compound.H1<H2.