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Method for preparing disodium terephthalate and high-purity hydrogen through one-step low-temperature conversion of PET polyester waste plastics

A disodium terephthalate and low-temperature conversion technology, applied in chemical instruments and methods, carboxylic anhydride preparation, hydrogen, etc., can solve problems such as high content, loss of ethylene glycol, difficult disposal of tar, etc., to achieve rapid processing and avoid Glycol loss, effect of high market value

Pending Publication Date: 2022-05-06
ZHEJIANG UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] At present, the existing thermochemical depolymerization processes for PET waste plastics mainly include alcoholysis, hydrolysis, ammonolysis, etc. The main problem is the loss of ethylene glycol in PET depolymerization products, and the obtained target products are not pure. Moreover, the high-concentration alkaline solution used in the process will cause a large amount of waste liquid
However, the gas phase products of pyrolysis and gasification of waste plastics contain high content of by-products such as carbon dioxide and alkanes, and the tar produced during the pyrolysis and gasification process is difficult to dispose of.

Method used

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  • Method for preparing disodium terephthalate and high-purity hydrogen through one-step low-temperature conversion of PET polyester waste plastics
  • Method for preparing disodium terephthalate and high-purity hydrogen through one-step low-temperature conversion of PET polyester waste plastics
  • Method for preparing disodium terephthalate and high-purity hydrogen through one-step low-temperature conversion of PET polyester waste plastics

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] Preparation method of reforming catalyst: use impregnation method to prepare catalyst, according to 5wt.% theoretical Ru loading, add a certain amount of biochar and precursor ruthenium chloride to absolute ethanol, stir and impregnate at room temperature for 12 hours, Continue stirring at 80°C until absolute ethanol evaporates to dryness, and dry the obtained sample (Ru / C) in an oven at 105°C; at 500°C, 10% H 2 Reduction in -90% Ar for 5 hours.

[0039] One-step low-temperature transformation of PET polyester waste plastics in a high-pressure reactor to prepare disodium terephthalate and high-purity hydrogen: Weigh 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru / C catalyst and 0.874g NaOH, run for 120 minutes at 180°C, no initial pressure, and reaction pressure 0.5MPa. After the reaction was completed, rapid cooling was carried out, and the generated gas was collected with an air bag and analyzed by gas chromatography, and the yield of hydrogen wa...

Embodiment 2

[0041] The preparation method of the reforming catalyst is the same as in Example 1.

[0042] One-step low-temperature transformation of PET polyester waste plastics in a high-pressure reactor to prepare disodium terephthalate and high-purity hydrogen: Weigh 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru / C catalyst and 0.874g NaOH, run for 120 minutes at 200°C, no initial pressure, and reaction pressure 1MPa. After the reaction was completed, rapid cooling was carried out, and the gas produced was collected by an air bag and analyzed by gas chromatography, and the yield of hydrogen was 18.31mol / kg PET , The hydrogen concentration is 98.77%. After recycling the liquid phase product and solid catalyst for 5 times, filter the liquid phase product and solid catalyst; add terephthalic acid to the filtered aqueous solution until the terephthalic acid cannot be dissolved to remove the residual Na 2 CO 3 and a small amount of NaOH to obtain refined disodium te...

Embodiment 3

[0044] The preparation method of the reforming catalyst is the same as in Example 1.

[0045] One-step low-temperature transformation of PET polyester waste plastics in a high-pressure reactor to prepare disodium terephthalate and high-purity hydrogen: Weigh 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru / C catalyst and 0.874g NaOH, run for 120 minutes at 220°C, no initial pressure, and reaction pressure 1.5MPa. After the reaction was completed, rapid cooling was carried out, and the generated gas was collected with an air bag and analyzed by gas chromatography, and the yield of hydrogen was 22.45mol / kg PET , The hydrogen concentration is 97.99%. After recycling the liquid phase product and solid catalyst for 5 times, filter the liquid phase product and solid catalyst; add terephthalic acid to the filtered aqueous solution until the terephthalic acid cannot be dissolved to remove the residual Na 2 CO 3 and a small amount of NaOH to obtain refined disodi...

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Abstract

The invention provides a method for preparing disodium terephthalate and high-purity hydrogen through one-step low-temperature conversion of PET polyester waste plastics, which comprises the following steps: directly mixing the PET polyester waste plastics and a catalyst according to a certain ratio, adding the mixture into a low-concentration NaOH solution, and preparing the high-purity hydrogen from the PET polyester waste plastics under a specific low-temperature hydrothermal condition by taking multiple effects of NaOH and directional catalytic characteristics of the catalyst as links. According to the method, PET hydrothermal depolymerization reaction and in-situ reforming reaction of a PET depolymerization product are coupled, so that high-efficiency one-step complete conversion of PET is realized in a reaction system, and high-purity hydrogen with the purity close to 99% and a crude disodium terephthalate solution are directly obtained through a one-step method; according to the present invention, the PET polyester waste plastic is subjected to a simple refining and crystallization process to obtain the high-purity terephthalic acid disodium salt crystal, such that the high-valued recycling of the PET polyester waste plastic is achieved, the process is simple and ingenious, the energy consumption is low, the extremely high industrial application value is provided, and the secondary pollution to the environment is not caused.

Description

【Technical field】 [0001] The invention relates to the technical field of thermochemical conversion of waste plastics, in particular to a method for preparing disodium terephthalate and high-purity hydrogen by converting PET polyester waste plastics at low temperature in one step. 【Background technique】 [0002] In recent decades, plastics have played an important role in industrial production and daily life due to their low production cost as well as good durability and corrosion resistance. However, the efficient and safe disposal of waste plastics needs to be paid attention to urgently. At present, most waste plastics are treated as solid waste, mainly by landfill or incineration, while waste plastics that have not been centrally treated enter the ecological environment. Due to the refractory natural degradability of waste plastics, it will cause permanent harm to the soil and water environment. A part of waste plastics enters the ocean and breaks into microplastics, whic...

Claims

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Application Information

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IPC IPC(8): C07C51/083C07C63/28C01B3/22
CPCC07C51/083C01B3/22C07C63/28Y02W30/62
Inventor 王树荣苏红才朱玲君李天高翔严建华岑可法
Owner ZHEJIANG UNIV
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