IP Library › Granted Patent US 12,528,928
Granted Patent B2
US 12,528,928 · App. 17/915,299 · Granted Jan 20, 2026

Methods for depolymerizing polyesters

Inventors: Tobin J. Marks (Evanston, IL); Yanshan Gao (Evanston, IL); Yosi Kratish (Evanston, IL); Jiaqi Li (Evanston, IL)
Assignee: Northwestern University
C08J11/16C07C51/09C08K3/012C08J2367/02C08K2003/2258
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Quick Facts
Patent No.
US 12,528,928
App. No.
17/915,299
Granted
Jan 20, 2026
Kind
B2
Abstract

A method for depolymerizing a polyester may comprise heating a polyester at a temperature and for a period of time in the presence of a supported metal-dioxo catalyst, optionally, in the presence of H 2 , to induce hydrogenolysis of ester groups in the polyester and provide monomers of the polyester.

Claims (20)

1 . A method for depolymerizing a polyester, the method comprising heating a polyester at a temperature and for a period of time in the presence of a supported metal-dioxo catalyst to induce hydrogenolysis of ester groups in the polyester and provide monomers of the polyester, wherein the monomers comprise a dicarboxylic acid.

2 . The method of claim 1 , wherein the method is carried out in the presence of H 2 .

3 . The method of claim 1 , wherein the dicarboxylic acid is an aromatic dicarboxylic acid or a heterocyclic dicarboxylic acid.

4 . The method of claim 1 , wherein the dicarboxylic acid is terephthalic acid.

5 . A method for depolymerizing a polyester, the method comprising heating a polyester at a temperature and for a period of time in the presence of a supported metal-dioxo catalyst to induce hydrogenolysis of ester groups in the polyester and provide monomers of the polyester, wherein the monomers comprise a dicarboxylic acid, and further wherein the hydrogenolysis further provides an alkene.

6 . The method of claim 1 , wherein the polyester is a polymerization product of reactants comprising an aromatic dicarboxylic acid or a heterocyclic dicarboxylic acid, and an aliphatic diol.

7 . The method of claim 6 , wherein the monomers comprise the aromatic dicarboxylic acid or the heterocyclic dicarboxylic acid and the hydrogenolysis further provides an alkene corresponding to the aliphatic diol.

8 . The method of claim 1 , wherein the polyester is polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyethylene 2,5-furandicarboxylate (PEF), polyethylene terephthalate glycol-modified (PETG), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT), or combinations thereof.

9 . The method of claim 8 , wherein the polyester is PET.

10 . The method of claim 9 , wherein the monomers comprise terephthalic acid and the hydrogenolysis further provides ethylene.

11 . The method of claim 2 , wherein the H 2 is at a pressure of no more than 50 atm.

12 . The method of claim 11 , wherein the pressure is no more than 10 atm.

13 . A method for depolymerizing a polyester, the method comprising heating a polyester at a temperature and for a period of time in the presence of a supported metal-dioxo catalyst to induce hydrogenolysis of ester groups in the polyester and provide monomers of the polyester, wherein the method is carried out in the absence of a solvent.

14 . A method for depolymerizing a polyester, the method comprising heating a polyester at a temperature and for a period of time in the presence of a supported metal-dioxo catalyst to induce hydrogenolysis of ester groups in the polyester and provide monomers of the polyester, wherein the metal of the supported metal-dioxo catalyst is a Group 6 transition metal.

15 . The method of claim 14 , wherein the Group 6 transition metal is Cr, Mo, W, or combinations thereof.

16 . The method of claim 1 , wherein the metal of the supported metal-dioxo catalyst is a Group 6 transition metal; the method is carried out in the presence of H 2 at a pressure of no more than 50 atm; the method is carried out in the absence of a solvent; and the hydrogenolysis further provides an alkene.

17 . The method of claim 16 , wherein the dicarboxylic acid is terephthalic acid.

18 . The method of claim 1 , further comprising recovering the catalyst and carrying out the method one or more additional times with the recovered catalyst.

19 . The method of claim 1 , further comprising recovering the monomers and repolymerizing the monomers to form a polymer.

20 . The method of claim 1 , wherein the polyester is provided in a mixture with a non-polyester polymer and the non-polyester polymer remains intact after the method.

Assignments (2)
CONFIRMATORY LICENSE Recorded May 30, 2023
From: NORTHWESTERN UNIVERSITY
To: UNITED STATES DEPARTMENT OF ENERGY
Reel/Frame 063803/0106 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Oct 31, 2022
From: MARKS, TOBIN J.; GAO, YANSHAN; KRATISH, YOSI; LI, JIAQI
To: NORTHWESTERN UNIVERSITY
Reel/Frame 061594/0499 →
Continuity (2)
Provisional Application 63008948 · Apr 13, 2020
Related Publication 20230145136A1 · May 11, 2023
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