PET Recycling With Impurity Gradient and Oligomer Depolymerization
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Solution Overview
Problem
Existing chemical recycling methods for polyethylene terephthalate (PET) are energy inefficient, environmentally unfriendly, and produce large amounts of degradation products, often requiring mixing with virgin PET to achieve high-quality recycled PET, with issues like impurities, caustic presence, adhesive adherence, and blockages in production plants.
Innovation Solution
A method involving a controlled impurity concentration gradient using organic compounds like ethylene glycol to depolymerize PET, with specific zone arrangements and temperature control to produce PET oligomers, effectively removing impurities and increasing throughput while reducing energy consumption and carbon footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical recycling methods are used to depolymerize PET to monomers, then complete decomposition is achieved, 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 (molar mass 1,000-10,000 g/mol) as intermediates rather than complete monomer decomposition. This partial depolymerisation approach reduces depolymerisation time while avoiding excessive degradation products, as the oligomers can be directly polymerized without requiring complete breakdown to monomers
Solution Approach 2:
The patent extracts and removes specific degradation products and impurities from the depolymerisation mixture through filtration and separation processes. This allows the depolymerisation to proceed efficiently while removing harmful byproducts that would otherwise accumulate and slow down the process
2Quantity of substance
If PET is depolymerised to monomers, then complete recycling is achieved, but large amounts of degradation products are produced that can't be removed from the recycled PET
Solution Approach 1:
The patent changes the depolymerisation endpoint parameter to produce oligomers instead of complete monomers. This controlled partial depolymerisation reduces the formation of degradation products while still achieving effective recycling, as the oligomers maintain the essential PET structure and can be repolymerized
Solution Approach 2:
The patent converts the potential harm of incomplete depolymerisation into a benefit by utilizing the oligomers as valuable intermediates. These oligomers, which would be considered partially degraded products, are actually the ideal starting material for repolymerisation, eliminating the need for complete monomer breakdown and reducing degradation byproducts
3Manufacturing precision
If filtering means are used to remove impurities, then product purity is improved, but the lifetime of the filtering means decreases due to blockages
Solution Approach 1:
The patent performs preliminary removal of large impurities and adhesives from the feedstock before the depolymerisation process. This pre-cleaning action prevents these materials from accumulating in filters during processing, extending filter lifetime while still achieving high product purity through the subsequent controlled depolymerisation and filtration of oligomers
4Adaptability or versatility
If chemical recycling processes are used, then PET can be recycled, but the process is very energy inefficient
Solution Approach 1:
The patent changes the energy parameter by operating at moderate temperatures (150-250°C) to produce oligomers rather than requiring high-temperature complete depolymerisation to monomers. This reduces energy consumption while maintaining recycling capability, as the oligomers can be directly repolymerized without requiring additional high-energy processing steps
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 enhances impurity removal, increases production efficiency, reduces energy use, and improves the quality of PET oligomers and polymers, enabling higher purity and faster polymerization with minimal virgin PET content.
Implementation Method 1
contacting the first polyester with a further amount of a first organic compound in a volume section V2... reducing a weight average molar mass of the first polyester, preferably in the volume section V3, to obtain a first intermediate mixture
Implementation Method 2
A method involving a controlled impurity concentration gradient using organic compounds like ethylene glycol to depolymerize PET
Implementation Method 3
with specific zone arrangements and temperature control to produce PET oligomers
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 first polyester is contacted with a further amount of a first organic compound in a volume section V2.At least one impurity is present in the volume section V2, andthe volume section V2 has a first zone and a further zone.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; andthe further organic compound.A relative ratio of a particle count per area of the at least one impurity in the first zone to a particle count per area of the at least one impurity in the further zone is equal to or greater than 10.