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Method for depolymerizing waste polyester

A technology for waste polyester and polyester is applied in the field of depolymerizing waste polyester-polyethylene terephthalate PET waste, which can solve the difficulty in refining the reactants, the low polyester conversion rate and the complex depolymerization process. and other problems, to achieve the effect of saving energy consumption, low cost and high monomer selectivity

Inactive Publication Date: 2009-10-28
BEIJING UNIV OF CHEM TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Document 1, European Patent [EUR.0662466 A1, (1995)] reports that PET is depolymerized at 240-300°C and 0.2-0.7MPa. The reaction requires less equipment and is easy to achieve continuous operation, but the reaction rate is relatively low. Low, the polyester conversion rate is low, and there are some oligomers in the product, which brings certain difficulties to the purification of the reactant
[0005] Document 2.[GB.Patent 2 041 916, (1980), Eur.484 963, (1996)] introduces the method of low-pressure depolymerization, which is generally carried out at 180-280°C, 2.0-6.0MPa, and the depolymerization rate It can be increased to 3 hours, but the depolymerization process is complicated, and generally requires 2-3 steps of cyclic depolymerization to complete, and there are still a small amount of oligomers and hydroxy-ethyl terephthalate in the product

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] Embodiment 1: get polyethylene terephthalate waste material 6.8g, put into and be furnished with electromagnetic stirrer, in the 200ml high-temperature high-pressure reactor of thermocouple and temperature program controller, add methanol 68.74ml, fill into N 2 When the pressure in the kettle reaches 0.5MPa, start the stirrer, raise the temperature to 240°C at a rate of 5°C / min, and raise the pressure to 8.9MPa, start the stirrer, and the reaction is carried out at this temperature for 20 minutes. After the reaction was completed, the temperature was naturally lowered, and the solid and liquid were separated. The solid was washed with water, washed with methanol, dried, weighed 6.32 g, and the yield of monomer dimethyl terephthalate was 92.2%. The ethylene glycol in the filtrate is analyzed by the periodic acid method, and the ethylene glycol content in the filtrate is recorded to be 2.07g. The degradation rate of polyethylene terephthalate was 94.3%.

Embodiment 2

[0017] Embodiment 2: get polyethylene terephthalate waste material 6.8g, put into one and be furnished with electromagnetic stirrer, in the 200ml high-temperature high-pressure reactor of thermocouple and temperature program controller, add methyl alcohol 68.74ml, fill into N 2 When the pressure in the kettle reaches 1MPa, the temperature is raised to 250°C at a rate of 5°C / min, the pressure rises to 10.1MPa, the stirrer is started, and the reaction is carried out at this temperature for 30 minutes. After the reaction was finished and the temperature was lowered, the solid and liquid were separated. The solid was washed with water, washed with methanol, dried, and weighed 6.53g. The yield of monomer dimethyl terephthalate was 95.3%. Prepare Na 2 S 2 o 3 solution and periodic acid solution, the ethylene glycol in the liquid is analyzed by the periodic acid method, the content of ethylene glycol in the filtrate is 2.17g, and the degradation rate of polyethylene terephthalate ...

Embodiment 3

[0018] Embodiment 3: get polyethylene terephthalate waste material 6.8g, put into one and be furnished with electromagnetic stirrer, in the 200ml high-temperature high-pressure reactor of thermocouple and temperature program controller, add methyl alcohol 52.5ml, fill into N 2 When the pressure in the kettle reaches 2MPa, the temperature is raised to 260°C at a rate of 5°C / min, the pressure rises to 9.8MPa, the stirrer is started, and the reaction is carried out at this temperature for 30 minutes. After the reaction was finished and the temperature was lowered, the solid and liquid were separated. The solid was washed with water, washed with methanol, dried, and weighed 6.44g. The yield of monomer dimethyl terephthalate was 93.7%. Prepare Na 2 S 2 o 3 solution and periodic acid solution, the ethylene glycol in the liquid is analyzed by the periodic acid method, the content of ethylene glycol in the filtrate is 2.15g, and the degradation rate of polyethylene terephthalate is...

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Abstract

The invention provides a method for depolymerizing waste polyester, which comprises the following steps of: adding methanol and cosolvent gas into a reaction system and utilizing the methanol and the cosolvent gas for depolymerizing waste polyester-polyethylene glycol terephthalate material so as to obtain dimethyl terephthalate and ethylene glycol on thesupercritical condition. According to the invention, as the cosolvent is added, the depolymerizing reaction temperature of the waste polyester is lowered and the reaction time is shortened, thereby reducing the energy consumption. As the cost of the cosolvent is relatively lower and easy for recycling, the recycling cost of the waste polyester is further lowered. In the method, the degradation rate of the olyethylene glycol terephthalate is more than 99.9 percent, the monosomic selectivity is high, and the content of oligomers in the product is low.

Description

technical field [0001] The invention relates to a method for depolymerizing waste polyester, in particular to a method for depolymerizing waste polyester—polyethylene terephthalate PET waste—under supercritical conditions by utilizing methanol and co-solvent. Background technique [0002] PET (polyethylene terephthalate) is a saturated polyester of terephthalic acid and ethylene glycol. It is widely used in packaging materials in food, beverage, chemical, pharmaceutical, cosmetic and other industries. The rapid development of the PET industry is accompanied by a sharp increase in its waste. If it is not properly recycled, it will not only cause a huge waste of resources, but also cause serious environmental pollution. [0003] Waste PET has strong resistance to atmosphere and biological reagents. The recycling of PET is mainly based on chemical recycling. The ester bond of PET is very susceptible to chain breakage caused by solvents. Different degradation reagents will res...

Claims

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Application Information

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IPC IPC(8): C07C69/82C07C67/28C07C67/297C07C31/20C07C29/00
CPCY02P20/582
Inventor 张敬畅李晶淼曹维良杨秀英李海平
Owner BEIJING UNIV OF CHEM TECH
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