Recycled Polyester Depolymerization via Microwave Titanium Catalysis
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Solution Overview
Problem
Current chemical recycling methods for polyester waste face issues such as contamination from heavy metal catalysts, high energy consumption, complex by-products, and difficulty in achieving closed-loop recycling, which hinder the effectiveness and environmental sustainability of the process.
Innovation Solution
A method involving depolymerization of waste polyester under microwave conditions using titanium-containing catalysts, followed by purification and co-esterification, allows for efficient recycling with reduced by-product production and energy use, enabling closed-loop recycling of waste polyester.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chemical recycling methods are used, then depolymerization can be achieved, but heavy metal catalyst residues contaminate the recycled polyester and reduce its quality
Solution Approach 1:
The patent removes harmful heavy metal catalysts from the recycling process and replaces them with non-metallic catalysts. This extraction of harmful substances allows the process to maintain depolymerization efficiency while eliminating contamination that would otherwise degrade recycled polyester quality.
Solution Approach 2:
The patent changes the chemical parameters of the catalyst system by switching from heavy metal-based catalysts to alternative non-metallic catalysts. This parameter change maintains the catalytic function needed for efficient depolymerization while eliminating the harmful contamination associated with heavy metal residues.
2Productivity
If high temperature and long time depolymerization conditions are used, then complete depolymerization is achieved, but energy consumption increases significantly
Solution Approach 1:
The patent changes the reaction parameters by using alternative catalysts that enable depolymerization to proceed efficiently at lower temperatures and shorter times. This parameter optimization maintains complete depolymerization while significantly reducing the energy input required for the process.
Solution Approach 2:
The patent substitutes the high-energy thermal field with a catalytic field that promotes depolymerization through chemical catalysis rather than purely thermal decomposition. This substitution allows the reaction to proceed more efficiently at milder conditions, reducing overall energy consumption while maintaining completeness.
3Productivity
If conventional depolymerization methods are used, then polyester can be recycled, but complex by-products are produced that require disposal and reduce efficiency
Solution Approach 1:
The patent converts the harmful effect of producing complex by-products into a benefit by using selective catalysts that steer the reaction toward desired products. The catalytic system is designed to promote depolymerization while minimizing unwanted side reactions, effectively converting what would be harmful by-products into useful or easily manageable substances.
Solution Approach 2:
The patent extracts and eliminates the formation of complex by-products through careful selection of catalysts and reaction conditions. By removing the chemical pathways that lead to unwanted by-products, the process maintains recycling capability while producing a cleaner, more manageable product profile.
4Productivity
If existing chemical recycling processes are used, then waste polyester can be processed, but the process requires pressurized conditions and high safety requirements
Solution Approach 1:
The patent changes the pressure and temperature parameters of the reaction conditions to operate under milder, less hazardous conditions. By optimizing the catalytic system, the process achieves waste polyester processing without requiring high pressure or extreme temperatures, thereby reducing safety requirements and device complexity.
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 high depolymerization efficiency with low temperature and short reaction time, reduces by-product yield, and allows for direct reuse of the catalyst, resulting in high-quality recycled polyester with reduced carbon emissions, aligning with green and low-carbon development goals.
Implementation Method 1
dissolving the waste polyester in a polyol solvent including a depolymerization catalyst and a microwave absorbent, and carrying out a depolymerization reaction under microwave conditions
Implementation Method 2
the depolymerization catalyst includes one or more of a titanate nanotube, titanium phosphate, titanium dioxide, butyl titanate, titanium glycolate, or titanium butanediol
Data Source
AI summary
A method with typical green and low-carbon characteristics for preparing recycled polyester by closed-loop recycling of waste polyester is disclosed. The method includes subjecting the waste polyester to depolymerization by using a specific depolymerization catalyst; removing a polyol solvent from a depolymerization product, and removing a by-product by purification to obtain a depolymerization monomer; mixing the depolymerization monomer with a binary acid, a polyol, a polymerization catalyst, and a chain extender to carry out an esterification reaction; and then adding a stabilizer and a catalyst for condensation polymerization to obtain the recycled polyester. The method of the present invention has low depolymerization temperature, high efficiency, low use amount of the polyol solvent, and extremely low content of a by-product. Meanwhile, the depolymerization catalyst can be directly used for the co-esterification of the recycled polyester without separation, and adverse effects on properties of the prepared recycled polyester cannot be caused.