Depolymerization of recovered plastic materials

Patent metadata

Field	Value
Publication number	US-11840667-B2
Application number	US-202217859644-A
Country	US
Kind code	B2
Filing date	Jul 7, 2022
Priority date	Jul 7, 2021
Publication date	Dec 12, 2023
Grant date	Dec 12, 2023

Abstract

Described herein are systems and methods for the depolymerization of polyethylene-based plastics. In one embodiment, a method is disclosed that comprises combining a polyethylene-based plastic with a solvent in a reactor to generate a plastic solvent mixture, heating the plastic solvent mixture in the reactor, and fractionating the plastic solvent mixture into a gas phase product, a solid phase product, and a liquid phase product. In another embodiment, a system is disclosed that comprises a solvent, and a reactor configured to receive the polyethylene-based plastic and the solvent and convert the polyethylene-based plastic into a gas phase product, a solid phase product, and a liquid phase product, the reactor being configured to operate at a temperature greater than 275° C. and at a pressure greater than 2 megapascals.

First claim

What is claimed is:

1. A method for depolymerizing a polyethylene-based plastic, the method comprising:
combining the polyethylene-based plastic with a solvent in a reactor to generate a plastic solvent mixture;
heating the plastic solvent mixture in the reactor at a temperature no greater than 360° C. for no less than 70 minutes and no greater than 120 minutes; and
fractionating the plastic solvent mixture into a gas phase product, a solid phase product, and a liquid phase product wherein the plastic solvent mixture is further combined with an ionic liquid catalyst prior to heating with.

2. The method according to claim 1 , wherein the solvent comprises at least one of water, methanol, ethanol, butanol, isopropyl alcohol, or acetone.

3. The method according to claim 2 , wherein the solvent comprises acetone.

4. The method according to claim 1 , wherein the ionic liquid catalyst comprises 1-butyl-3-methylimidazolium, bis[(perfluoroethyl)sulfonyl]-imide ([BMIM][PF2]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), or combinations thereof.

5. The method according to claim 1 , wherein the heating is performed at about 300° C. to 360° C.

6. The method according to claim 5 , wherein the heating is performed between about 340° C. to 360° C.

7. The method according to claim 1 , wherein the heating is performed at a pressure of about 2 megapascals to about 20 megapascals.

8. The method according to claim 7 , wherein the heating is performed at a pressure of about 8 megapascals to about 11 megapascals.

9. The method according to claim 1 , wherein the heating is performed for about 80 minutes to about 100 minutes.

10. The method according to claim 1 , wherein the plastic solvent mixture is combined in a weight/volume ratio of about 1 gram plastic:6 mL solvent to about 1 gram plastic:20 mL solvent.

11. The method according to claim 1 , further comprising separating the gas phase product and the liquid phase product using a combined membrane and adsorption process.

12. The method according to claim 1 , wherein at least 60% of the polyethylene-based plastic is converted into the gas phase product and the liquid phase product.

13. The method according to claim 1 , wherein at least 30% of the polyethylene-based plastic is converted into the liquid phase product.

14. The method according to claim 1 , wherein the liquid phase product has an oxygen/carbon ratio of about 0.01 to about 0.70.

15. The method according to claim 1 , wherein the liquid phase product has a hydrogen/carbon ratio of about 1.4 to about 2.0.

16. The method according to claim 1 , wherein the liquid phase product has a high heat value of about 35 MJ/kg to about 45 MJ/kg.

17. A method for depolymerizing a polyethylene-based plastic, the method comprising:
combining the polyethylene-based plastic with a solvent comprising acetone in a reactor to generate a plastic solvent mixture;
heating the plastic solvent mixture in the reactor at a temperature no greater than 360° C., at a pressure greater than 2 megapascals, and for no less than 70 minutes and no greater than 120 minutes;
fractionating the plastic solvent mixture into a gas phase product, a solid phase product, and a liquid phase product; and

separating the gas phase product and the liquid phase product using a combined membrane and adsorption process.

18. A method for depolymerizing a polyethylene-based plastic, the method comprising:
combining the polyethylene-based plastic with a solvent comprising acetone in a reactor to generate a plastic solvent mixture;
heating the plastic solvent mixture in the reactor at a temperature no greater than 360° C. for no less than 70 minutes and no greater than 120 minutes; and
fractionating the plastic solvent mixture into a gas phase product, a solid phase product, and a liquid phase product.

Assignees

• Deng Shuguang
• Liu Yixin
• Akula Kapil Chandra
• Dandamudi Kodanda Phani Raj
• Univ Arizona State

Inventors

• Deng Shuguang
• Liu Yixin
• Akula Kapil Chandra
• Dandamudi Kodanda Phani Raj

Classifications

• C10G1/10 Primary

  from rubber or rubber waste · CPC title

• B01D3/145

  One step being separation by permeation · CPC title

• B01D53/229

  Integrated processes (Diffusion and at least one other process, e.g. adsorption, absorption) · CPC title

• B01J6/008

  Pyrolysis reactions (of hydrocarbons C10G9/00) · CPC title

• C08J11/08

  using selective solvents for polymer components · CPC title