Research ArticleChemistry

Molecular catalyst systems as key enablers for tailored polyesters and polycarbonate recycling concepts

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Science Advances  10 Aug 2018:
Vol. 4, no. 8, eaat9669
DOI: 10.1126/sciadv.aat9669
  • Scheme 1 Reductive depolymerization of polymeric waste with a molecular ruthenium catalyst.
  • Fig. 1 Overview of the commercially available PET sources used for the catalytic hydrogenolysis.
  • Fig. 2 Selective separation of two different polyesters via the catalytic hydrogenolysis approach.

    Top: Selective polymer hydrogenolysis of PLA and PET using [Ru(triphos-xyl)methylallyl]NTf2; reaction conditions: PLA (2 mmol), PET (2 mmol), [Ru(triphos-xyl)methyllaly]NTf2 (10 μmol), 1,4-dioxane (4 ml), H2 (100 bar), 16 hours. Conversion and selectivity were determined by 1H NMR spectroscopy using mesitylene as internal standard. Bottom: Flow diagram, illustrating the envisioned processing of polymer mixtures.

  • Fig. 3 Hydrogenolysis up-scaling for selected polyesters and polycarbonate consumer products.
  • Table 1 Hydrogenolysis of selected polyesters and polycarbonate material using [Ru(triphos)tmm] (A) or [Ru(triphos-xyl)tmm] (B) and HNTf2.*
    Embedded Image

    *Reaction conditions: H2 (100 bar), polymer (1 mmol; calculated on the repetition unit), 1 mol % [Ru(triphos)tmm] (A) and HNTf2, 3 ml of 1,4-dioxane, 140°C, 16-hour reaction time.

    †Conversion and selectivity were determined by 1H NMR spectroscopy using mesitylene as internal standard.

    ‡[Ru(triphos-xyl)tmm] (B) (1 mol %) was used instead of A.

    • Table 2 Hydrogenolysis of PET of commercially available sources using [Ru(triphos-xyl)tmm] (B)/HNTf2 as catalyst.*
      Embedded Image

      *Reaction conditions: H2 (100 bar), PET (2 mmol), 1 equivalent HNTf2 related on the catalyst [Ru(triphos-xyl)tmm] (B), 16 hours, 140°C, 4 ml of 1,4-dioxane.

      †Conversion and selectivity were determined by 1H NMR spectroscopy using mesitylene as internal standard.

      • Table 3 Hydrogenolysis of polymer granules and commercially available products using [Ru(triphos)tmm] (A)/[Ru(triphos-xyl)tmm] (B) and HNTf2 as catalyst.*
        Embedded Image

        *Reaction conditions: H2 (100 bar), x mol % [Ru(triphos)tmm] (A)/[Ru(triphos-xyl)tmm] (B) and HNTf2, 16-hour reaction time, 140°C, x ml of 1,4-dioxane.

        †Yield was determined via 1H NMR spectroscopy using mesitylene as internal standard.

        ‡Reaction was performed in 3 ml of 1,2-propanediol.

        • Table 4 Hydrogenolysis scale-up of consumer polymer products using [Ru(triphos)tmm] (A)/[Ru(triphos-xyl)tmm] (B) and HNTf2.*
          EntryConversion (%)Selectivity (%)Polymer source (g)Catalyst (mol %)
          1>99>99Drinking cup, PLA (11.4)A 0.05
          2>99980.5-Liter water bottle, PET (13.2) + screw cap, PP and labeling, PE (2.9)B 0.2
          3>99>990.5-Liter water bottle, PET (13.2)B 0.1
          4>99>99CD, PC (16.1)A 0.5

          *Reaction conditions: The reactions were performed in a 500-ml steel autoclave using 16-hour reaction time, x mol % [Ru(triphos)tmm] (A) and HNTf2, 140°C, 120 ml of 1,4-dioxane, and 90-bar constant hydrogen pressure.

          †Conversion and selectivity were determined by 1H NMR spectroscopy using mesitylene as internal standard.

          ‡[Ru(triphos-xyl)tmm] (B) and HNTf2 were used.

          Supplementary Materials

          • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/8/eaat9669/DC1

            Section S1. General procedure

            Section S2. Synthesis of the catalysts

            Section S3. General procedure for autoclave reactions

            Section S4. Additional Information

            Section S5. NMR spectroscopy data of the products

            Section S6. Crude NMR spectra of the products

            Section S7. NMR spectra of the isolated products

            Table S1. Hydrogenolysis of PLA derived from S-PLA granulate and a beverage cup using [Ru(triphos-derivative)tmm] complexes and HNTf2.

            Table S2. Hydrogenolysis of PET with [Ru(triphos-xyl)tmm] and HNTf2 in the presence of a polymer “additive/impurity.”

            Table S3. Hydrogenolysis of PCL in the polymer melt using [Ru(triphos)tmm] and HNTf2.

            Table S4. Separation of PLA and PET via selective hydrogenolysis at low temperatures using [Ru(triphos-xyl)tmm] and HNTf2.

            Fig. S1. Pressure drop curves of the hydrogenolysis of PCL with different molecular weights using [Ru(triphos)tmm] and HNTf2 as catalyst.

            Fig. S2. Pressure drop curve of the hydrogenolysis of polyesters and polycarbonates.

            Fig. S3. 1H NMR spectrum (600 MHz) [0 to 7.5 parts per million (ppm)] of the crude 1,4-dioxane reaction mixture of the PLA (1) hydrogenolysis to 1,2-propanediol (1a).

            Fig. S4. 13C NMR spectrum (150 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the PLA (1) hydrogenolysis to 1,2-propanediol (1a).

            Fig. S5. 1H NMR spectrum (600 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PCL (2) to 1,6-hexanediol (2a).

            Fig. S6. 13C NMR spectrum (150 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PCL (2) to 1,6-hexanediol (2a).

            Fig. S7. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PET (4) obtained from a water bottle to benzene dimethanol (4a) and ethylene glycol (4b).

            Fig. S8. 13C NMR spectrum (100 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PET (4) obtained from a water bottle to benzene dimethanol (4a) and ethylene glycol (4b).

            Fig. S9. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PBT (5) to benzene dimethanol (4a) and 1,4-butanediol (5b).

            Fig. S10. 13C NMR spectrum (100 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PBT (5) to benzene dimethanol (4a) and 1,4-butanediol (5b).

            Fig. S11. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of polycarbonate (bisphenol A) (3), obtained from a CD, to 4,4′(propane-2,2-diyl)diphenol (bisphenol A, 3a) and methanol (3b).

            Fig. S12. 13C NMR spectrum (75 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of polycarbonate (bisphenol A) (3), obtained from a CD, to 4,4′(propane-2,2-diyl)diphenol (bisphenol A, 3a) and methanol (3b).

            Fig. S13. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the isolated 1,2-propanediol (1a) obtained from a postconsumed beverage cup in CDCl3.

            Fig. S14. 13C NMR spectrum (100 MHz) (10 to 230 ppm) of the isolated 1,2-propanediol (1a) obtained from a postconsumed beverage cup in CDCl3.

            Fig. S15. 1H NMR spectrum (400 MHz) (0 to 12.5 ppm) of the isolated bisphenol A (3a) obtained from a postconsumed CD in dimethyl sulfoxide (DMSO)–d6.

            Fig. S16. 13C NMR spectrum (100 MHz) (0 to 230 ppm) of the isolated bisphenol A (3a) obtained from a postconsumed CD in DMSO-d6.

            Fig. S17. 1H NMR spectrum (400 MHz) (0 to 8 ppm) of the isolated 1,4-benzene dimethanol (4a) obtained from a postconsumed PET bottle in a mixture of CDCl3 and DMSO-d6.

            Fig. S18. 13C NMR spectrum (100 MHz) (0 to 210 ppm) of the isolated 1,4-benzene dimethanol (4a) obtained from a postconsumed PET bottle in a mixture of CDCl3 and DMSO-d6.

          • Supplementary Materials

            This PDF file includes:

            • Section S1. General procedure
            • Section S2. Synthesis of the catalysts
            • Section S3. General procedure for autoclave reactions
            • Section S4. Additional Information
            • Section S5. NMR spectroscopy data of the products
            • Section S6. Crude NMR spectra of the products
            • Section S7. NMR spectra of the isolated products
            • Table S1. Hydrogenolysis of PLA derived from S-PLA granulate and a beverage cup using Ru(triphos-derivative)tmm complexes and HNTf2.
            • Table S2. Hydrogenolysis of PET with Ru(triphos-xyl)tmm and HNTf2 in the presence of a polymer “additive/impurity.”
            • Table S3. Hydrogenolysis of PCL in the polymer melt using Ru(triphos)tmm and HNTf2.
            • Table S4. Separation of PLA and PET via selective hydrogenolysis at low temperatures using Ru(triphos-xyl)tmm and HNTf2.
            • Fig. S1. Pressure drop curves of the hydrogenolysis of PCL with different molecular weights using Ru(triphos)tmm and HNTf2 as catalyst.
            • Fig. S2. Pressure drop curve of the hydrogenolysis of polyesters and polycarbonates.
            • Fig. S3. 1H NMR spectrum (600 MHz) 0 to 7.5 parts per million (ppm) of the crude 1,4-dioxane reaction mixture of the PLA (1) hydrogenolysis to 1,2-propanediol (1a).
            • Fig. S4. 13C NMR spectrum (150 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the PLA (1) hydrogenolysis to 1,2-propanediol (1a).
            • Fig. S5. 1H NMR spectrum (600 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PCL (2) to 1,6-hexanediol (2a).
            • Fig. S6. 13C NMR spectrum (150 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PCL (2) to 1,6-hexanediol (2a).
            • Fig. S7. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PET (4) obtained from a water bottle to benzene dimethanol (4a) and ethylene glycol (4b).
            • Fig. S8. 13C NMR spectrum (100 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PET (4) obtained from a water bottle to benzene dimethanol (4a) and ethylene glycol (4b).
            • Fig. S9. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PBT (5) to benzene dimethanol (4a) and 1,4-butanediol (5b).
            • Fig. S10. 13C NMR spectrum (100 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of PBT (5) to benzene dimethanol (4a) and 1,4-butanediol (5b).
            • Fig. S11. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of polycarbonate (bisphenol A) (3), obtained from a CD, to 4,4′(propane-2,2-diyl)diphenol (bisphenol A, 3a) and methanol (3b).
            • Fig. S12. 13C NMR spectrum (75 MHz) (0 to 160 ppm) of the crude 1,4-dioxane reaction mixture of the hydrogenolysis of polycarbonate (bisphenol A) (3), obtained from a CD, to 4,4′(propane-2,2-diyl)diphenol (bisphenol A, 3a) and methanol (3b).
            • Fig. S13. 1H NMR spectrum (400 MHz) (0 to 7.5 ppm) of the isolated 1,2-propanediol (1a) obtained from a postconsumed beverage cup in CDCl3.
            • Fig. S14. 13C NMR spectrum (100 MHz) (10 to 230 ppm) of the isolated 1,2-propanediol (1a) obtained from a postconsumed beverage cup in CDCl3.
            • Fig. S15. 1H NMR spectrum (400 MHz) (0 to 12.5 ppm) of the isolated bisphenol A (3a) obtained from a postconsumed CD in dimethyl sulfoxide (DMSO)–d6.
            • Fig. S16. 13C NMR spectrum (100 MHz) (0 to 230 ppm) of the isolated bisphenol A (3a) obtained from a postconsumed CD in DMSO-d6.
            • Fig. S17. 1H NMR spectrum (400 MHz) (0 to 8 ppm) of the isolated 1,4-benzene dimethanol (4a) obtained from a postconsumed PET bottle in a mixture of CDCl3 and DMSO-d6.
            • Fig. S18. 13C NMR spectrum (100 MHz) (0 to 210 ppm) of the isolated 1,4-benzene dimethanol (4a) obtained from a postconsumed PET bottle in a mixture of CDCl3 and DMSO-d6.

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