Highly efficient organic catalyst-based plastic recycling method

Abstract

1. A method for decomposing polymeric waste into at least one useful decomposition product, wherein the polymeric waste comprises at least one condensation polymer, the method comprising contacting the polymeric waste with a catalyst comprising an organic nitrogen-containing base and a carboxylic acid or ester thereof in the presence of a protic molecule selected from alcohols, diols, polyols, and amines at an elevated temperature effective to induce alcoholysis or aminolysis of the condensation polymer, wherein the useful decomposition product comprises a monomeric species capable of polymerization, and the organic nitrogen-containing base has the structure: TIFF2025527501000047.tif36167 [where R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently selected from a hydrogen atom, an electron pair, and an alkyl group containing 1 to 3 carbon atoms; R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 Any adjacent two of may optionally be joined to each other to form a 5-, 6-, or 7-membered ring.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 397,919, filed August 15, 2022, the entire contents of which are incorporated herein by reference.

[0002] STATEMENT REGARDING FEDERALLY FUNDED RESEARCH This invention was made with government support under prime contract numbers DE-AC05-00OR22725 and AC02-07CH11358 awarded by the U.S. Department of Energy. The government has certain rights in this invention.

[0003] Field of Disclosure This disclosure relates generally to methods for breaking down and recycling plastic waste, and more particularly to methods for breaking down polymeric waste into monomers or other useful molecular products through the use of catalysts. [Background technology]

[0004] Plastics have transformed everyday life due to their stable mechanical properties, light weight, scalability, versatility, and functional performance. 10.5 billion metric tons of plastics have been produced worldwide, with an annual production rate exceeding 380 million metric tons (Mt) (M. Chu et al., ACS Catalysis, 2022, 12(18), 4659-4679). Due to inadequate recycling and upcycling pathways, plastic-derived waste poses a global challenge for end-of-life management. It is estimated that nearly 79% of manufactured plastics are landfilled or accumulate in the natural environment, and 12% are incinerated (R. Geyer et al., Science Advances 2017, 3(7), e1700782). Only about 9% of plastic waste is recycled, typically through mechanical recycling, and most recycled plastics are currently downcycled into less recyclable, lower-value products (BC Gibb, Nat. Chem. 2019, 11(5), 394-395). Commercial plastics used annually in the United States alone account for an estimated 3,200 trillion BTUs (quads) of energy and 104 Mt of CO2 equivalent greenhouse gas (GHG) emissions (SR Nicholson et al., Joule 2021, 5(3), 673-686).

[0005] One of the most effective strategies for mitigating GHG emissions involves establishing closed-loop circularity for plastics, such as chemical recycling, to replace fossil carbon feedstocks and minimize energy and carbon inputs throughout the plastics supply chain (R. Meys et al., Science 2021, 374(6563), 71-76). Significant scientific advances are needed to achieve closed-loop circularity for plastics by replacing fossil carbon feedstocks to a much greater extent with bio-based or waste-source feedstocks from chemical recycling of discarded plastics. It is estimated that establishing circular plastics recycling on a global scale would mitigate energy consumption equivalent to 3.5 billion barrels of oil, valued at approximately $176 billion, annually (M. Hong et al., Green Chemistry 2017, 19(16), 3692-3706).

[0006] Among various commodity plastics, condensation polymers, such as poly(ethylene terephthalate) (PET), poly(carbonate) (PC), poly(urethane) (PU), and poly(amide) (PA), comprise approximately 30% of global plastic production, with PET and PU ranking fifth and sixth most produced plastics, respectively (J.C. Worch et al., ACS Macro Letters 2020, 9(11), 1494-1506). Chemical recycling of condensation polymers through methods such as glycolysis is an evolving and versatile route to creating value-added materials from plastic waste or to recover essential monomers for use in plastic circularity. Several innovative solutions, such as metal-based catalysts, ionic liquids, or deep eutectic solvents, have recently been reported to achieve the depolymerization of individual polar plastics (PET, PC, PU, ​​and PA) into their monomeric products (Figure 1) (G.W. Coates et al., Nature Reviews Materials 2020, 5(7), 501-516). Despite these advances, many challenges remain, including the possible presence of metals in the final product, limited monomer yields, the need for specific catalysts for each polymer, laborious fractionation procedures, and purification procedures that involve high environmental and economic costs.

[0007] Organocatalysts offer many advantages for the degradation of condensation polymers. Their environmentally friendly properties, such as good selectivity, thermal stability, nonvolatility, and low flammability, make them a good alternative to traditional heterogeneous catalysts (C. Jehanno et al., Green Chemistry 2018, 20(6), 1205-1212). Protic ionic salt (PIS)-based organocatalysts have been used for the degradation of condensation polymers. The catalytic activity of PIS is governed by a dual activation mechanism, where the anion activates nucleophiles and the cation activates electrophiles (C=O bonds) (C. Jehanno et al., Angewandte Chemie International Edition 2021, 60(12), 6710-6717). One such PIS catalyst, triazabicyclododecane:methanesulfonic acid (TBD:MSA), has shown promise for the degradation of PC and PET individually and in their mixtures (C. Jehanno et al., Green Chemistry 2018, 20(6), 1205-1212). While the development of TBD:MSA sheds light on the design of PIS organocatalysts, significant challenges remain in achieving degradation of a wide variety of condensation polymers and their mixtures, as well as various other mixed plastics (J.C. Worch et al., ACS Macro Letters 2020, 9(11), 1494-1506). [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] M. Chu et al., ACS Catalysis, 2022, 12(18), 4659-4679 [Non-patent document 2] R. Geyer et al., Science Advances 2017, 3(7), e1700782 [Non-patent document 3] BCGibb, Nat.Chem.2019, 11(5), 394-395 [Non-patent document 4] S.R.Nicholson et al., Joule 2021, 5(3), 673-686 [Non-Patent Document 5] R. Meys et al., Science 2021, 374(6563), 71-76 [Non-patent document 6] M. Hong et al., Green Chemistry 2017, 19(16), 3692-3706 [Non-Patent Document 7] JCWorch et al., ACS Macro Letters 2020, 9(11), 1494-1506 [Non-patent document 8] GW Coates et al., Nature Reviews Materials 2020, 5(7), 501-516 [Non-Patent Document 9] C. Jehanno et al., Green Chemistry 2018, 20(6), 1205-1212 [Non-Patent Document 10] C. Jehanno et al., Angewandte Chemie International Edition 2021, 60(12), 6710-6717 Summary of the Invention [Problem to be solved by the invention]

[0009] Currently, mixed plastics are difficult to recycle from post-consumer waste because they must be sorted and separated before reprocessing. From a cost perspective, producing new plastic products from virgin feedstock is typically more cost-effective than sorting and reusing reprocessed materials. Low recycling rates are exacerbated by the increase in mixed waste streams of multi-component plastics, such as composites and packaging. No single catalyst or technology is currently available for selectively converting mixtures of plastics into valuable chemicals in one pot. There would be significant benefit in a method that can efficiently decompose mixed plastic waste, with the ability to simultaneously or sequentially decompose different polymers in the mixture. [Means for solving the problem]

[0010] In a first aspect, the present disclosure relates to a highly efficient PIS organocatalyst that can efficiently decompose mixed wastes of PC, PU, ​​PET, and PA in a single batch through the selective cleavage of amide, carbonate, urethane, and ester bonds. The designed organocatalyst can selectively decompose condensation polymers while leaving other polymers, such as polyolefins (e.g., poly(ethylene) (PE) and poly(propylene) (PP)) or cotton, intact, allowing for their easy separation from the mixture. The chemical degradation process described herein can advantageously be applied to a significant portion of existing mixed plastics, providing a way to achieve closed-loop circularity and carbon neutrality for plastics.

[0011] The catalyst comprises an organic nitrogen-containing base and a carboxylic acid or ester thereof, which are typically complexed with each other. In particular, carboxylic acid esters may be used, which are typically converted to the corresponding carboxylic acid during the decomposition process.

[0012] The organic nitrogen-containing base (i.e., the "base") can be more specifically represented by the following formula:

[0013] [ka] In the formula, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are independently selected from a hydrogen atom, an electron pair, and an alkyl group containing 1 to 3 carbon atoms; R 1 and R 2 may optionally be interconnected to form a 5-, 6-, or 7-membered ring, and R 2 and R 3may optionally be interconnected to form a 5-, 6-, or 7-membered ring, and R 3 and R 4 may optionally be interconnected to form a 5-, 6-, or 7-membered ring, and R 4 and R 6 may optionally be interconnected to form a 5-, 6-, or 7-membered ring, and R 5 and R 6 may optionally be interconnected to form a 5-, 6-, or 7-membered ring, and R 1 and R 5 may optionally be interconnected to form a 5-, 6-, or 7-membered ring, X is C or N, and the dotted line represents an optional double bond. In certain embodiments, the base may have any of the structures shown in formulas (1a), (1b), (1c), (1d), (1e), (1f), (1g), (1h), and (1i).

[0014] The catalyst may comprise, or may comprise exclusively, any of the above bases in combination with a carboxylic acid or ester thereof, where the carboxylic acid or ester thereof may have the following structure:

[0015] [ka] where R is a hydrogen atom or a hydrocarbon group containing 1 to 12 carbon atoms, and one or more fluorine atoms and / or OR b group, and may be substituted with another carboxylic acid group or ester thereof, R b is selected from a hydrogen atom and an alkyl group containing 1 to 3 carbon atoms. In some embodiments, R is a hydrocarbon group containing 1 to 6, 1 to 5, 1 to 4, 1 to 3, or 1 to 2 carbon atoms, optionally substituted with one or more halogen (e.g., fluorine, chlorine, bromine, and / or iodine) atoms. In some embodiments, the carboxylic acid or ester thereof is trifluoroacetic acid or ester thereof.

[0016] Any one or more of the above types of carboxylic acid or ester species can be combined with any one or more bases of formulas (1), (1a), (1b), (1c), (1d), (1e), (1f), (1g), (1h), and (1i) to provide a catalyst, as further described below. The carboxylic acid or ester (A) species can be combined with the base (B) species in any desired B:A molar ratio, such as a B:A molar ratio in the range of 0.05:1 to 1:0.05, a B:A molar ratio in the range of 0.2:1 to 1:0.2, a B:A molar ratio in the range of 0.5:1 to 1:0.5, or a B:A molar ratio of about 1:1.

[0017] In another aspect, the present disclosure relates to a method for decomposing polymeric waste into at least one useful degradation product, wherein the polymeric waste contains at least one condensation polymer. The method comprises contacting the polymeric waste with any of the above catalysts in the presence of a protic molecule selected from alcohols, diols, polyols, and amines at an elevated temperature effective to induce alcoholysis or aminolysis of the condensation polymer, wherein the useful degradation product comprises a monomeric species capable of polymerization. In some embodiments, the protic molecule is a diol such as ethylene glycol. In some embodiments, the condensation polymer is selected from at least one of the group consisting of polyesters, polyurethanes, polycarbonates, and polyamides. In some embodiments, the condensation polymeric waste contains at least two different types of condensation polymers. In some embodiments, the condensation polymeric waste contains a polyester such as polyethylene terephthalate, and the at least one useful degradation product can be bis(2-hydroxyethyl) terephthalate. An exemplary schematic of this process is shown in FIG. 1B. [Brief explanation of the drawings]

[0018] [Figure 1](Parts A and B) Illustrates methods for mixed plastics degradation. Part A shows a schematic of conventional methods for decomposing plastics, which involve fractionation of individual polymers followed by mechanical recycling or chemical recycling using specific catalysts. Part B shows possible valuable products produced by the disclosed method, which provides efficient decomposition of mixed plastics (PC, PU, ​​PET, and PA) with tailored organic catalysts to produce valuable chemicals. [Figure 2A-2B] Figure 2A shows the catalytic activity of TBD:TFA. Figure 2A shows the formation of TBD:TFA. 1H NMR spectrum (Figure 2B) shows the disappearance of the TFA peak at δ 13.84 ppm (·) (Figure 2B, top) and a shift of the TBD peak from δ 4.14 ppm (·) (Figure 2B, bottom) to δ 8.12 ppm (·), indicating the formation of TBD:TFA (Figure 2B, center). [Figure 2C-2D] Figure 2C shows the catalytic activity of TBD:TFA. Figure 2C shows the degradation of PET using TBD:TFA, resulting in pure BHET crystals upon recrystallization in water. H NMR spectra before (Figure 2D, bottom) and after (Figure 2D, top) purification demonstrate the successful removal of pure BHET and the catalyst and excess EG. [Figures 2E-2F] Figure 2E shows the catalytic activity of TBD:TFA (gold), which shows complete conversion at 2 hours compared to TBD:MSA (purple), TBD (gray), TBD:mTFA (brown), and mTBD:TFA (orange). Figure 2F shows the recyclability of the catalyst during PC, PU, ​​PET, and PA degradation. [Figures 2G-2H] Figure 2G and 2H show the catalytic activity of TBD:TFA. The results and conditions of the kinetic studies of PC, PU, ​​PET, and PA to produce the corresponding monomers BPA (black), MDA (red), BHET (blue), and CPL (green), respectively, are shown. Reaction conditions: polymer (1 equiv.), EG (10 equiv.), catalyst (0.05 equiv.) at 180 °C (110–210 °C for H) for 2 h. [Figure 3]1 is a scheme showing the proposed degradation mechanism of PET by EG using TBD:TFA as a catalyst based on computational analysis. Step-1: Dual activation mechanism via association and dissociation between TBDH+ and TFA anion for the degradation of PET using EG as a nucleophile and TBD:TFA as a catalyst, yielding BHET as the product; Step-2: Interaction between TBDH+ and PET (ΔE=24.7 kcal / mol) and TFA anion with EG (ΔE=30.4 kcal / mol); Steps 3 and 4: Simultaneous chemical bond formation between PET and EG and proton abstraction by TFA anion; Step 5: Cleavage of PET to form oligomers and finally monomers. [Figure 4A] Figure 4A shows the sequential and selective degradation of mixed plastics. Figure 4A shows the sequential degradation of mixed PC, PU, ​​PET, and PA using TBD:TFA (0.05 equivalents) and EG (10 equivalents) for 2 hours, where open circles represent PC, red triangles represent PU, blue diamonds represent PET, and green squares represent PA. At 130°C (I), PC is completely converted to BPA, while PU, PET, and PA remain intact (B&B'). At 160°C (II), PA remains intact (C&C'), while PU is completely converted to MDA, with less PET conversion. At 180°C (III), PET is completely converted to BHET, while PA remains unreacted (D&D'). Finally, at 210°C (IV), the remaining unreacted PA is completely converted to CPL (E&E'). Alternatively, PC, PU, ​​PET, and PA can be decomposed in one go by direct heating at 210°C (V) to yield the corresponding mixtures of BPA, MDA, BHET, and CPL. [Figure 4B]Figure 4B shows the sequential and selective degradation of mixed plastics. Figure 4B (top) shows the degradation of a PET bottle and PP cap mixture to produce BHET, while keeping the PP intact. Figure 4B (middle) shows the degradation of PC, PU, ​​PET, and PA consumer products combined with a PE bag piece to produce the corresponding monomers BPA, MDA, BHET, and CPL, respectively, while keeping the PE intact. Figure 4B (bottom) shows the degradation of a polyester (40%) and cotton (60%)-based fabric to produce BHET monomer, while the unreacted cotton can be easily separated. [Figure 4C-4D] Figure 4C shows the sequential and selective degradation of mixed plastics. TBD: Energy footprint (Figure 4C) and carbon footprint (Figure 4D) of the production of PC, PU, ​​PET, and PA by a conventional petroleum-based approach versus the reconstitution of PC, PU, ​​PET, and PA using degraded monomers by a TFA-based process. DETAILED DESCRIPTION OF THE INVENTION

[0019] In a first aspect, the present disclosure relates to a catalyst containing an organic nitrogen-containing base (i.e., "base" or "B species") and a carboxylic acid or ester thereof (i.e., "acid" or "A species"). The base is typically complexed with the acid in the catalyst. The carboxylic acid or ester (A) species can be combined with the base (B) species in any desired B:A molar ratio, which can have B and A molar values ​​independently selected from, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1. The B:A molar ratio can also be within a range of B:A molar ratios. In some embodiments, the B:A molar ratio is within the range of 0.05:1 to 1:0.05 (1:20 to 20:1). In other embodiments, the B:A molar ratio is in the range of 0.2:1 to 1:0.2 (or 1:5 to 5:1). In other embodiments, the B:A molar ratio is in the range of 0.5:1 to 1:0.5 (or 1:2 to 2:1). In other embodiments, the B:A molar ratio is about 1:1.

[0020] In embodiments, the organic nitrogenous base has the structure:

[0021] [ka]

[0022] In equation (1), the variable R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are independently selected from hydrogen atoms, electron pairs, and alkyl groups containing 1 to 3 carbon atoms. Examples of alkyl groups containing 1 to 3 carbon atoms include methyl, ethyl, n-propyl, and isopropyl. The dotted line represents an optional double bond. When a nitrogen atom in formula (1) or a subformula thereof is involved in a carbon-nitrogen double bond, the substituent shown attached to the nitrogen atom is an electron pair to maintain charge neutrality. The variable X can be any of C, CR, a or N, wherein R ais selected from hydrogen atoms and alkyl groups containing 1 to 3 carbon atoms. In particular, according to the rules of chemistry, the variable R 1 , R 2 , R 3 , R 4 , R 5 or R 6 can only be an electron pair if the electron pair is attached to a nitrogen atom involved in a carbon-nitrogen double bond. Similarly, by the rules of chemistry, X is a C only if C is involved in a carbon-carbon double bond, and X is a C only if CR a CR only when the carbon atoms in the a In some embodiments, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are hydrogen atoms. In other embodiments, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 one, two, three, four, five, or all of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are selected from methyl groups, ethyl groups, n-propyl groups, or isopropyl groups, or combinations thereof.

[0023] In a first set of embodiments, R 1 and R 2 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 1 and R 2 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 1 and R 2 are not mutually coupled.

[0024] In a second set of embodiments, R 2 and R 3 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 2 and R 3 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 2 and R 3 are not mutually coupled.

[0025] In a third set of embodiments, R 3 and R 4 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 3 and R 4 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 3 and R 4 are not mutually coupled.

[0026] In a fourth set of embodiments, R 4 and R 6 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 4 and R 6 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 4 and R 6 are not mutually coupled.

[0027] In a fourth set of embodiments, R 5 and R 6 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 5 and R 6 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 5 and R 6 are not mutually coupled.

[0028] In a fifth set of embodiments, R 1 and R 5are optionally interconnected to form a 5-, 6-, or 7-membered ring. In some embodiments, R 1 and R 5 are interconnected to form a 5-, 6-, or 7-membered ring, but in other embodiments, R 1 and R 5 are not mutually coupled.

[0029] Any two of the above first to fifth embodiments can be combined to obtain a bicyclic compound within the scope of formula (1). Any three of the above first to fifth embodiments can be combined to obtain a tricyclic compound within the scope of formula (1).

[0030] In some embodiments of Formula (1), the organic nitrogenous base has the following structure:

[0031] [ka]

[0032] In formula (1a), R 2 , R 3 , R 4 , R 6 and X are as previously defined above, and the variable r has a value of 0, 1, or 2. When r is 0, a 5-membered ring occurs. When r is 1, a 6-membered ring occurs. When r is 2, a 7-membered ring occurs. In some embodiments of formula (1a), X is C or CR a In other embodiments of Formula (1a), X is N. In some embodiments, R 2 , R 3 , R 4 , R 6 are hydrogen atoms. In other embodiments, R 2 , R 3 , R 4 , R 6 one, two, three, or all of R are alkyl groups containing 1 to 3 carbon atoms, or more specifically, R 2 , R 3 , R 4 , R 6are selected from methyl, ethyl, n-propyl, or isopropyl groups, or combinations thereof. When the nitrogen atom in formula (1a) is bonded to a hydrogen atom or an alkyl group, the nitrogen atom is not involved in a double bond, since the presence of a double bond in such a situation would result in a positively charged molecule, but for purposes of this disclosure, the molecules of formula (1) and its subformulas are uncharged (neutral). When the nitrogen atom in formula (1) or its subformulas is bonded to a carbon-nitrogen double bond, a substituent (e.g., R 4 or R 6 ) is then an electron pair to maintain charge neutrality (no charge). In some embodiments, when the remaining optional double bond shown in formula (1a) is not present, R 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 2 and R 3 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In further or alternative embodiments, R 3 and R 4 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In further or alternative embodiments, R 4 and R 6 are optionally interconnected to form a 5-, 6-, or 7-membered ring.

[0033] In some embodiments of Formula (1a), the organic nitrogenous base has the structure:

[0034] [ka]

[0035] In formula (1b), R 2 , R 3 , R 4 , R 6and X is as previously defined above. In some embodiments of formula (1b), X is C or CR a In other embodiments of formula (1b), X is N. In some embodiments, R 2 , R 3 , R 4 , R 6 are hydrogen atoms. In other embodiments, R 2 , R 3 , R 4 , R 6 one, two, three, or all of R are alkyl groups containing 1 to 3 carbon atoms, or more specifically, R 2 , R 3 , R 4 , R 6 In some embodiments, one, two, three, or all of R are selected from methyl, ethyl, n-propyl, or isopropyl groups, or combinations thereof. 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond, and the remaining optional double bond shown in formula (1a) is absent. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 2 and R 3 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In further or alternative embodiments, R 3 and R 4 are optionally interconnected to form a 5-, 6-, or 7-membered ring. In further or alternative embodiments, R 4 and R 6 are optionally joined to each other to form a 5-, 6-, or 7-membered ring.

[0036] In some embodiments of Formula (1), the organic nitrogenous base has the structure:

[0037] [ka]

[0038] In formula (1c), R 4 , R 6 and X are as previously defined above, and the variables r and s each independently have a value of 0, 1, or 2. When r or s is 0, a 5-membered ring is obtained. When r or s is 1, a 6-membered ring is obtained. When r or s is 2, a 7-membered ring is obtained. In different embodiments, r and s are both 0, or r and s are both 1, or r and s are both 2, or r is 0 and s is 1, or r is 0 and s is 2, or r is 1 and s is 0, or r is 1 and s is 2, or r is 2 and s is 0, or r is 2 and s is 1. In some embodiments of formula (1c), X is C or CR a In other embodiments of Formula (1c), X is N. In some embodiments, R 4 and R 6 is a hydrogen atom. In another embodiment, R 4 and R 6 is an alkyl group containing 1 to 3 carbon atoms, or more specifically, R 4 and R 6 In some embodiments, one or both of R 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond, and the remaining optional double bond shown in formula (1c) is absent. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 4 and R 6 are optionally joined to each other to form a 5-, 6-, or 7-membered ring.

[0039] In some embodiments of Formula (1c), the organic nitrogenous base has the structure:

[0040] [ka]

[0041] In formula (1d), R 4 , R 6 and X is as previously defined above. In some embodiments of formula (1d), X is C or CR a In other embodiments of formula (1d), X is N. In some embodiments, R 4 and R 6 is a hydrogen atom. In another embodiment, R 4 and R 6 is an alkyl group containing 1 to 3 carbon atoms, or more specifically, R 4 and R 6 In some embodiments, one or both of R 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond, and the remaining optional double bond shown in formula (1d) is absent. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 4 and R 6 are optionally joined to each other to form a 5-, 6-, or 7-membered ring.

[0042] In some embodiments of Formula (1c), the organic nitrogenous base has the structure:

[0043] [ka]

[0044] In formula (1e), R 4 and R 6is as previously defined above, and the variables r and s each independently have a value of 0, 1, or 2. When r or s is 0, a 5-membered ring is obtained. When r or s is 1, a 6-membered ring is obtained. When r or s is 2, a 7-membered ring is obtained. In different embodiments, r and s are both 0, or r and s are both 1, or r and s are both 2, or r is 0 and s is 1, or r is 0 and s is 2, or r is 1 and s is 0, or r is 1 and s is 2, or r is 2 and s is 0, or r is 2 and s is 1. In some embodiments, R 4 and R 6 is a hydrogen atom. In another embodiment, R 4 and R 6 is an alkyl group containing 1 to 3 carbon atoms, or more specifically, R 4 and R 6 In some embodiments, one or both of R 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond, and the remaining optional double bond shown in formula (1e) is absent. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 4 and R 6 are optionally joined to each other to form a 5-, 6-, or 7-membered ring.

[0045] In some embodiments of Formula (1e), the organic nitrogenous base has the structure:

[0046] [ka]

[0047] In formula (1f), R 4 and R 6is as previously defined above. In some embodiments, R 4 and R 6 is a hydrogen atom. In another embodiment, R 4 and R 6 is an alkyl group containing 1 to 3 carbon atoms, or more specifically, R 4 and R 6 In some embodiments, one or both of R 6 is an electron pair, and R 6 is involved in a carbon-nitrogen double bond, in which case the remaining optional double bond shown in formula (1f) is absent. 4 is an alkyl group, such as any of the alkyl groups provided above, in particular methyl or ethyl. In further or alternative embodiments, R 4 and R 6 are optionally joined to each other to form a 5-, 6-, or 7-membered ring.

[0048] In some embodiments of Formula (1), the organic nitrogenous base has the structure:

[0049] [ka]

[0050] In formula (1g), R 6 is as previously defined above. In some embodiments, R 6 is a hydrogen atom. In another embodiment, R 6 is an alkyl group containing 1 to 3 carbon atoms, or more specifically R 6 is selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, or a combination thereof. 6 When R is a hydrogen atom or an alkyl group, the optional double bond is not present. 6 is an electron pair, and R6 The nitrogen atom attached to is involved in a carbon-nitrogen double bond.

[0051] In some embodiments of Formula (1), the organic nitrogenous base has the structure:

[0052] [ka]

[0053] In formula (1h), R 4 is as previously defined above. In some embodiments, R 4 is a hydrogen atom. In another embodiment, R 4 is an alkyl group containing 1 to 3 carbon atoms, or more specifically R 4 is selected from a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, or a combination thereof. 4 When R is a hydrogen atom or an alkyl group, the optional double bond is not present. 4 is an electron pair, and R 4 The nitrogen atom attached to is involved in a carbon-nitrogen double bond.

[0054] In some embodiments of Formula (1), the organic nitrogenous base has the structure:

[0055] [ka]

[0056] In formula (1i), R 1 , R 3 , R 4 , R 5 , R 6 and X is R 1 , R 3 , R 4 , R 5 and R 6In some embodiments of formula (1i), X is as defined above except that CR a In other embodiments of formula (1i), X is N. In some embodiments, R 1 , R 3 , R 4 , R 5 , R 6 are hydrogen atoms. In other embodiments, R 1 , R 3 , R 4 , R 5 , R 6 one, two, three, four, or all of R 1 , R 3 , R 4 , R 5 , R 6 In some embodiments, one, two, three, four, or all of R are selected from methyl, ethyl, n-propyl, or isopropyl groups, or combinations thereof. 1 , R 3 and R 5 is selected from alkyl groups containing 1 to 3 carbon atoms, such as any of the alkyl groups provided above, or R 1 , R 3 and R 5 is a methyl group.

[0057] Some specific examples of organic nitrogen-containing bases include:

[0058] [ka]

[0059] As previously noted above, a base, which may have any of the structures within formula (1), (1a), (1b), (1c), (1d), (1e), (1f), (1h), (1i), or the specific structures provided above, is combined (typically complexed) with a carboxylic acid or ester thereof in the catalyst. The base and acid can be included in the catalyst in any suitable molar ratio, such as, for example, any of those previously provided above.

[0060] The carboxylic acid or ester thereof may have the following structure:

[0061] [ka]

[0062] In formula (2), R is a hydrogen atom (H) or a hydrocarbon group having 1 to 12 carbon atoms. In different embodiments, the hydrocarbon group R contains, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms, or a number of carbon atoms within a specific range bounded by any two of the aforementioned carbon numbers (e.g., 1 to 12, 1 to 8, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 2 to 12, 2 to 8, 2 to 6, 2 to 5, 2 to 4, or 2 to 3 carbon atoms). As used herein, the term "hydrocarbon group" (also represented by the group R) is defined as a chemical group containing at least carbon and hydrogen atoms. In some embodiments, R consists exclusively of carbon and hydrogen. In other embodiments, R is composed of carbon atoms and possibly hydrogen atoms, except that the hydrocarbon group may be (i.e., optionally) substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, which may result in partial or complete halogenation of the hydrocarbon group. The group R may be one or more OR b may or may not be substituted with a group, where R b is R aAs previously described above for R, the group R is selected from hydrogen atoms and alkyl groups containing 1 to 3 carbon atoms. The group R may or may not be substituted with another (additional) carboxylic acid group or ester thereof, resulting in a dicarboxylic acid. In different embodiments, the group R may be unsubstituted (i.e., contains only carbon and hydrogen), or may be substituted with one or more halogen atoms, or may be substituted with one or more OR b or may be substituted with an additional carboxylic acid group, or may be substituted with a halogen and OR b a combination of groups, or a combination of halogen and an additional carboxylic acid group, or OR b and additional carboxylic acid groups.

[0063] In a first set of embodiments, the hydrocarbon group (R) is a saturated straight-chain group, i.e., a straight-chain (linear) alkyl group. Some examples of straight-chain alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl groups. Any of the foregoing straight-chain alkyl groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the straight-chain alkyl group. Any of the foregoing straight-chain alkyl groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0064] In a second set of embodiments, the hydrocarbon group (R) is saturated and branched, i.e., a branched alkyl group. Some examples of branched alkyl groups include isopropyl (2-propyl), isobutyl (2-methylprop-1-yl), sec-butyl (2-butyl), t-butyl (1,1-dimethylethyl-1-yl), 2-pentyl, 3-pentyl, 2-methylbut-1-yl, isopentyl (3-methylbut-1-yl), 1,2-dimethylprop-1-yl, 1,1-dimethylprop-1-yl, neopentyl (2,2-dimethylprop-1-yl), 2-hexyl, 3-hexyl, 2-methylpent-1-yl, and 2-methylpent-1-yl. Examples of branched alkyl groups include 1,1-dimethylbut-1-yl, 3-methylpent-1-yl, isohexyl (4-methylpent-1-yl), 1,1-dimethylbut-1-yl, 1,2-dimethylbut-1-yl, 2,2-dimethylbut-1-yl, 2,3-dimethylbut-1-yl, 3,3-dimethylbut-1-yl, 1,1,2-trimethylprop-1-yl, 1,2,2-trimethylprop-1-yl, isoheptyl, isooctyl, and many other branched alkyl groups having up to 12 carbon atoms, with the "1-yl" suffix indicating the point of attachment of the group. Any of the aforementioned branched alkyl groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the branched alkyl group. Any of the aforementioned branched alkyl groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0065] In a third set of embodiments, the hydrocarbon group (R) is saturated and cyclic, i.e., a cycloalkyl group. Some examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. The cycloalkyl group can also be a polycyclic (e.g., bicyclic) group by having either a bond between two ring groups (e.g., dicyclohexyl) or a covalent (i.e., fused) side chain (e.g., decalin and norbornane). Any of the foregoing cycloalkyl groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the cycloalkyl group. Any of the foregoing cycloalkyl groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0066] In a fourth set of embodiments, the hydrocarbon group (R) is unsaturated and straight-chained, i.e., a straight-chained (linear), olefinic or alkenyl group. The unsaturation arises from the presence of one or more carbon-carbon double bonds and / or one or more carbon-carbon triple bonds. Some examples of straight-chain olefinic groups include vinyl, propen-1-yl (allyl), 3-buten-1-yl (CH═CH—CH—CH—), 2-buten-1-yl (CH—CH═CH—CH—), butadienyl, 4-penten-1-yl, 3-penten-1-yl, 2-penten-1-yl, 2,4-pentadien-1-yl, 5-hexen-1-yl, 4-hexen-1-yl, 3-hexen-1-yl, 3,5-hexadien-1-yl, 1,3,5-hexatrien-1-yl, 6-hepten-1-yl, ethynyl, propargyl (2-propynyl), 3-butynyl, and many other straight-chain alkenyl or alkynyl groups having up to 12 carbon atoms. Any of the foregoing linear alkenyl groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the linear alkenyl group. Any of the foregoing linear alkenyl groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0067] In a fifth set of embodiments, the hydrocarbon group (R) is unsaturated and branched, i.e., a branched olefinic group or an alkenyl group. Some examples of branched olefinic groups include propen-2-yl (CH=C.-CH), 1-buten-2-yl (CH=C.-CH-CH), 1-buten-3-yl (CH=CH-CH-CH), 1-propen-2-methyl-3-yl (CH=C(CH)-CH-), 1-penten-4-yl, 1-penten-3-yl, 1-penten-2-yl, 2-penten-2-yl, 2-penten-3-yl, 2-penten-4-yl, yl, and 1,4-pentadien-3-yl, as well as numerous other branched alkenyl groups having up to 12 carbon atoms, where the dot in any of the foregoing groups indicates the point of attachment. Any of the foregoing branched alkenyl groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the branched alkenyl group. Any of the foregoing branched alkenyl groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0068] In a sixth set of embodiments, the hydrocarbon group (R) is unsaturated and cyclic, i.e., a cycloalkenyl group. The unsaturated cyclic group can be aromatic or aliphatic. Some examples of unsaturated cyclic hydrocarbon groups include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclohexadienyl, phenyl, benzyl, cycloheptenyl, cycloheptadienyl, cyclooctenyl, cyclooctadienyl, and cyclooctatetraenyl. The unsaturated cyclic hydrocarbon group may also be a polycyclic group (e.g., a bicyclic or tricyclic polycyclic aromatic group) by having a bond between two of the ring groups (e.g., biphenyl) or a covalent (i.e., fused) side chain, such as in naphthalene, anthracene, phenanthrene, phenalene, or indene fused ring systems. All of the aforementioned ring groups are carbocyclic groups. Any of the foregoing unsaturated cyclic hydrocarbon groups may or may not be substituted with one or more halogen (e.g., fluorine, chlorine, bromine, or iodine) atoms, resulting in partial or complete halogenation of the cycloalkenyl group. Any of the foregoing unsaturated cyclic hydrocarbon groups may be substituted with one or more OR b may or may not be substituted with groups, or may be substituted with additional carboxylic acid groups, or may be substituted with halogens and OR b A combination of groups or a combination of halogen and an additional carboxylic acid group or OR b and additional carboxylic acid groups.

[0069] In a seventh set of embodiments, the hydrocarbon group (R) has more than 12 carbon atoms (e.g., at least 15, 20, 25, 30, 35, 40, 45, or 50 or more carbon atoms) and may be oligomeric or polymeric. In the case of oligomeric or polymeric groups, the group may be, for example, a polyethylenel, poly(tetrafluoroethylenyl), or polyethylene glycol group.

[0070] In equation (2), R b is selected from hydrogen atoms and alkyl groups having 1 to 3 carbon atoms. In one set of embodiments, R bis a hydrogen atom, and R can be any of the linear, branched, or cyclic (and alternatively, saturated or unsaturated) hydrocarbon groups provided above. In another set of embodiments, R b is an alkyl group, and R can be any of the linear, branched, or cyclic (and alternatively, saturated or unsaturated) hydrocarbon groups provided above.

[0071] Some specific examples of carboxylic acids or esters thereof include the following:

[0072] [ka]

[0073] Alternatively, the base is

[0074] [ka] The general formula is R-SO3R b (Wherein R and R b may be complexed with a sulfonic acid having an ester (i.e., one or more acidic hydrogen atoms are bonded to one or more R b alkyl substituted) are contemplated herein.

[0075] The catalyst can be prepared by combining a base component and an acid component (i.e., according to formulas (1) and (2), respectively) under conditions that allow the two components to form a complex with each other. Typically, the two components are combined in the absence or presence of a solvent and heated to a temperature of 40-80°C, or more specifically 50-70°C, or about 60°C, for a period of 15-45 minutes, more typically about 30 minutes.

[0076] In another aspect, the present disclosure relates to a method for decomposing polymer waste into at least one useful degradation product by contacting the polymer waste with the above-described catalyst at elevated temperatures and in the presence of protic molecules. For purposes of the present invention, the polymer waste should comprise at least one condensation polymer, such as polyester (e.g., PET, PBT, PHT, or unsaturated polyester), polyurethane, polycarbonate, and / or polyamide (e.g., nylon, such as nylon 6, nylon 6,6, or nylon 1,6). In some embodiments, the polymer waste comprises at least two or three different types of condensation polymers, such as polyester and polyurethane, polyester and polycarbonate, polyester and polyamide, polyurethane and polycarbonate, polyurethane and polyamide, or two different types of polyester, or two different types of polyurethane, or two different types of polycarbonate, or two different types of polyamide. The polymer waste may also contain different physical forms of the same type of polymer, such as a bottle and carpet both made from polyester, or more specifically, PET. Useful degradation products typically include monomer species that can be polymerized. For example, in some embodiments, the polymer waste contains polyester, such as polyethylene terephthalate (PET), and at least one useful degradation product can be bis(2-hydroxyethyl) terephthalate. An exemplary schematic of this process is shown in Figure 1B.

[0077] As described above, the polymer waste is contacted with the catalyst at elevated temperature and in the presence of protic molecules. The elevated temperature is effective to induce catalytic alcoholysis or aminolysis of the condensation polymer. The elevated temperature is typically at least 150°C and up to 250°C, provided that the elevated temperature is below the decomposition temperature of the polymer waste. In different embodiments, the temperature may be, for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C, or within a range bounded by any two of the foregoing values ​​(e.g., 150-250°C, 160-240°C, 170-230°C, 170-220°C, or 170-200°C). The process may be carried out at any of the foregoing temperatures for a period of, for example, 1 hour, 2 hours, 3 hours, or 4 hours, or within that range. The method can be carried out at ambient pressure (about 1 atm), although in some embodiments, the combined components (catalyst and polymer waste in contact with protic molecules) can be subjected to elevated pressures, for example, greater than 1 atm, or at least 2, 5, 10, 20, or 50 atm. In some embodiments, the polymer waste comprises two or more types of condensation polymer waste, and the two or more types of condensation polymer waste are catalytically decomposed simultaneously at a single temperature. In other embodiments, the polymer waste comprises two or more types of condensation polymer waste, and the two or more types of condensation polymer waste are catalytically decomposed sequentially at different temperatures.

[0078] Some common examples of protic molecules include alcohols, diols, polyols, and amines. Some examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Some examples of diols include methylene glycol, ethylene glycol, propylene glycol, 1,3-propanediol, poly(ethylene)diol, poly(ethylene glycol), polydimethylsiloxane, and poly(butadiene)diol. Some examples of polyols include glycerol, sugar alcohols (e.g., xylitol and erythritol), and polyether polyols. Some examples of amines include ammonia, methylamine, ethylamine, methylenediamine, ethylenediamine, and ethanolamine. The protic molecule is typically included in at least an equimolar amount relative to the polymer waste. More typically, the protic molecule is included in an excess amount relative to the polymer waste, for example, at least 2, 3, 4, 5, or 10 times the molar amount of the polymer waste. The catalyst is typically included in the reaction system in a lower molar amount compared to the molar amount of the polymer waste, for example, 0.25X, 0.2X, 0.1X, or 0.05X or less (wherein X represents the molar amount of the polymer waste). In some embodiments, after the reaction is complete or nearly complete, the crude product is mixed with excess water to remove excess protic molecules and catalyst from the decomposition product.

[0079] For illustrative purposes, examples are set forth below to describe certain specific embodiments of the present invention. However, the scope of the present invention is in no way limited by the examples set forth herein. [Example]

[0080] Overview

[0081] Herein, we describe a highly efficient PIS organocatalyst that can efficiently degrade mixed PC, PU, ​​PET, and PA waste in a single batch through the selective cleavage of amide, carbonate, urethane, and ester bonds. Figure 1 (part A) contains a schematic diagram of the conventional method, and Figure 1 (part B) shows the possible products produced by the disclosed method. The designed organocatalyst can selectively degrade condensation polymers while leaving other polymers, including polyolefins (e.g., poly(ethylene) (PE) and poly(propylene) (PP)), or cotton intact, allowing for the easy separation of non-condensation polymers from the mixture. The described chemical degradation process can be applied to the majority of known mixed plastics, thus providing a viable step toward closed-loop circularity and carbon neutrality of plastics.

[0082] method

[0083] Chemicals: All reactions were carried out in a thick-walled cylindrical pressure vessel. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) (98%), trifluoroacetic acid (TFA) (99%), ethylene glycol (EG) (99.8%), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) (98%), methyl trifluoroacetate (mTFA) (99%), dimethyl sulfoxide-d6 (DMSO-d6) (99.9%), and methanol (99%) were used as received without further purification. Polycarbonate (PC, Mw = 45,000 g / mol) and polyamide (PA, nylon 6, Mw = 35,000 g / mol) were purchased as granules from commercial sources and used as received. Poly(ethylene terephthalate) (i.e., PET, Mw 40,000 g / mol and 60,000 g / mol) was obtained from a commercial source. Polyurethane (PU) was synthesized. 1 It was characterized by H NMR. Gel permeation chromatography (GPC) determined that the molecular weight of the PU was Mw 24600 g / mol.

[0084] <Synthesis Procedure. TBD:TFA Synthesis> Different dual catalysts were prepared by mixing TBD and TFA in a base to acid molar ratio at 60°C for 30 or 60 minutes and used without further purification. Below is a schematic diagram of this process.

[0085] [ka]

[0086] Different organocatalysts were prepared using different ratios of TBD and TFA as follows:

[0087] [Table 1]

[0088] Using a 1:1 molar ratio of TBD and different acids, different organocatalysts were prepared as follows:

[0089] [Table 2] TIFF2025527501000021.tif213166TIFF2025527501000022.tif83161

[0090] Different organocatalysts were prepared as follows using a 1:1 molar ratio of different bases in combination with TFA.

[0091] [Table 3]

[0092] <TBD:TFA(1:1)>

[0093] [ka]

[0094] 11H NMR (400 MHz, DMSO) δ 8.07 (s, 2H), 3.27 (td, J = 6.2, 2.2 Hz, 4H), 3.18 (dq, J = 6.0, 2.9 Hz, 4H), 1.88 (dd, J = 8.6, 4.0 Hz, 4H). 13 13C NMR (101 MHz, DMSO) δ 159.72, 150.83, 118.10, 46.09, 37.33, 20.20.

[0095] <TBD:TFA(3:1)>

[0096]

Chem.

[0097] 1 1H NMR (400 MHz, DMSO) δ 5.10 (s, 2H), 3.08 (q, J = 5.6 Hz, 8H), 2.02 - 1.59 (m, 4H).

[0098] <TBD:TFA(1:3)>

[0099]

Chem.

[0100] 1 1H NMR (400 MHz, DMSO) δ 15.35 (s, 1H), 7.79 (s, 2H), 3.37 - 3.21 (m, 4H), 3.17 (s, 4H), 1.85 (s, 4H).

[0101] <TBD:mTFA(1:1) synthesis>

[0102]

Chem.

[0103] An equimolar amount of TBD and mTFA was mixed with a magnetic stirrer at 60 °C for 30 minutes and used without further purification. 11H NMR (400 MHz, DMSO) δ 3.33 - 3.13 (m, 8H), 2.90 (s, 3H), 1.89 (ddp, J = 16.1, 11.0, 5.9 Hz, 4H).

[0104] <Synthesis of 1:1 mTBD:TFA>

[0105]

Chem.

[0106] An equimolar amount of mTBD and TFA were mixed at 60 °C for 30 minutes and used without further purification. 1 1H NMR (400 MHz, DMSO) δ 3.27 (ddt, J = 22.1, 10.7, 5.8 Hz, 8H), 2.92 (s, 3H), 1.93 (p, J = 6.0 Hz, 2H), 1.86 (p, J = 5.9 Hz, 2H).

[0107] <Polyurethane synthesis>

[0108]

Chem.

[0109] Methylene diphenyl diisocyanate (MDI) (5.3 g, 21.2 mmol), ethylene glycol (1.4 g, 21.2 mmol), dibutyltin dilaurate (5.0 mg) and 50 mL of DMF were placed in a 500 mL round bottom flask and the reaction mixture was heated at 80 °C in an oil bath. Then, the mixture was reacted for 12 hours to achieve complete polymerization. The final viscous solution was poured into 1 L of ethanol. The precipitate was collected and dried in a vacuum oven at 60 °C for 12 hours to obtain pure polyurethane with Mw 24600 g / mol, and PDI 1.23 was confirmed by GPC. 1 1H NMR (400 MHz, DMSO) δ 9.64 (s, 2H), 7.35 (d, J = 8.1 Hz, 4H), 7.09 (d, J = 8.1 Hz, 4H), 4.30 (s, 4H), 3.78 (s, 2H).

[0110] <Decomposition of PET Polymer>

[0111] [Chemical formula]

[0112] <General Procedure> PET pellets (0.5 g, 2.60 mmol), EG (1.62 g, 26 mmol), and a catalyst (0.035 g, 0.13 mmol) were placed in a pressure vessel equipped with a magnetic stirrer. The decomposition reaction was carried out at 180 °C for 2 hours. When the reaction was complete, the crude product was cooled to room temperature and a large excess of distilled water was added. The resulting solution was vigorously stirred and filtered to separate EG, the catalyst, and the main product from the dimer, oligomer, and water-insoluble substances. The aqueous clear filtrate was stored in a refrigerator at 4 °C overnight. White needle-like crystals of bis(2-hydroxyethyl) terephthalate (BHET) formed in the solution and were then recovered by filtration and dried.

[0113] <bhet> 1 1H NMR (400 MHz, DMSO) δ 8.13 (s, 4H), 4.97 (t, J = 5.7 Hz, 2H), 4.36 - 4.29 (m, 4H), 3.72 (q, J = 5.3 Hz, 4H).

[0114] <BHET dimer> 1 1H NMR (400 MHz, DMSO) δ 8.15 - 8.05 (m, 8H), 4.97 (q, J = 5.4 Hz, 2H), 4.68 (s, 4H), 4.31 (q, J = 4.7 Hz, 4H), 3.71 (p, J = 6.4 Hz, 4H).

[0115] <Optimization of catalytic reaction> PET pellets (0.5 g, 2.6 mmol, 1 equivalent) were charged into a 10 mL pressure vessel equipped with a magnetic stirrer. Each depolymerization was carried out at 180 °C for 2 hours using 10 equivalents of EG and a catalyst. Using the catalyst signal (δ = 1.87 ppm, 4H) as an internal standard and the characteristic signal of BHET (δ = 8.10 ppm, 4H), the corresponding isolated yields were used to obtain the yields by 1H NMR spectroscopy in DMSO-d6. 1 The yields were obtained by 1H NMR spectroscopy.

[0116]

Table 4

[0117]

Table 5

[0118] <Catalytic activity of PET by using TBD:TFA vs TBD:MSA> In a typical experiment, 1:0.05:10 equivalents of PET pellets, catalyst, and EG were charged into a 10 mL pressure vessel equipped with a magnetic stirrer. Each decomposition was carried out at 180 °C for 2 hours.

[0119] Large-scale reaction: PET pellets (10 g, 52 mmol, 1 equiv.) were loaded into a 150 mL pressure vessel equipped with a magnetic stirrer. Decomposition was carried out at 180 °C for 4 h using 10 equiv. of EG and 0.05 equiv. of catalyst. The catalyst signal (d = 1.87 ppm, 4H) and the characteristic signal of BHET (d = 8.10 ppm, 4H) were used as internal standards. 1 Yields were calculated using the corresponding isolated yields using 1 H NMR spectroscopy.

[0120] Catalyst Optimization: PET pellets (0.5 g, 2.6 mmol, 1 equiv.) were loaded into a 10 mL pressure vessel equipped with a magnetic stirrer. Each decomposition reaction was carried out for 2 h at a specific temperature with a given EG and catalyst. The catalyst signal (d = 1.87 ppm, 4H) and the characteristic signal of BHET (d = 8.10 ppm, 4H) were used as internal standards in DMSO-d6. 1 Yields were calculated using the corresponding isolated yields using 1 H NMR spectroscopy.

[0121] <Decomposition of polycarbonate (PC) polymer>

[0122] [ka]

[0123] PC pellets (0.5 g, 1.97 mmol), EG (1.22 g, 19.7 mmol), and catalyst (0.025 g, 0.10 mmol) were placed in a pressure vessel equipped with a magnetic stirrer. The digestion was carried out at 130 °C for 2 h. The reaction mixture was then cooled to room temperature and dissolved in diethyl ether (30 mL) and water (30 mL). The organic phase was washed three times with water before being dried over MgSO. The mixture was then purified using CombiFlash® to give bisphenol A (BPA) (94%), ethylene carbonate (93%), and bis-(hydroxypropoxy)propane (bis-HPP) (5%). Yields were calculated using the catalytic signal (d = 1.87 ppm, 4H) as an internal standard and the characteristic signals of BPA (δ 6.67 ppm), EC (δ 4.48 ppm), and bis-HPP (δ 4.08 ppm, 2H) in DMSO-d6. 1 Calculated using H NMR spectroscopy. BPA: 1 H NMR (400MHz, DMSO) δ9.11(s, 2H), 6.98(d, J=8.4Hz, 4H), 6.64(d, J=8.3Hz, 4H), 1.53(s, 6H). EC: 1 H NMR (400 MHz, CDCl) δ 4.48 (s, 4H). Bis-HPP: 1 H NMR (400MHz, CDCl3) δ7.34-7.25(m, 4H), 7.22-7.15(m, 2H), 6.90-6.81(m, 2H), 4.09(dd, J=5.2, 3.9Hz, 4H), 4.01-3.95(m, 4H), 1.69(s, 6H).

[0124] <Decomposition of polyurethane (PU)>

[0125] [ka]

[0126] PU pellets (0.1 g, 0.32 mmol), EG (0.20 g, 3.20 mmol), and catalyst (0.004 g, 0.016 mmol) were placed in a pressure vessel equipped with a magnetic stirrer. The digestion was carried out at 150–170 °C for 2 h. After 2 h, a mixture of 1 M HCl (15 mL) and brine (5 mL) was added. The mixture was extracted with CHCl (4 × 10 mL), and the combined organic phase was washed with brine (1 × 15 mL), dried over anhydrous NaSO, filtered, and evaporated to dryness to obtain EG as a liquid. The acidic aqueous phase was basified with 4 M NaOH until the pH reached 11–12 and then extracted with CHCl (3 × 10 mL). The combined organic phases were dried using anhydrous Na2SO4, filtered, and evaporated to dryness to give methylenedianiline (MDA) (0.14 g, 80%) and bis(2-hydroxyethyl)methylenebis(4,1-phenylene)dicarbamate (BMDC) (<17%). Yields were determined using the catalytic signal (d = 1.87 ppm, 4H) as an internal standard and the characteristic signals of MDA (δ 6.8 and 6.5 ppm) and BMDC (δ 7.3 and 7.1 ppm) in DMSO-d6. 1 The yield of MDA increased and the yield of BMDC decreased as a result of increasing the temperature. 1 H NMR (400MHz, DMSO) δ6.81 (dd, J=7.8, 5.5Hz, 4H), 6.47 (dd, J=7.8, 5.5Hz, 4H), 4.82 (br, 4H), 3.59 (s, 2H).

[0127] <Decomposition of Polyamide (PA)>

[0128] [ka]

[0129] Nylon-6 pellets (0.5 g, 4.4 mmol), EG (2.73 g, 44 mmol), and catalyst (0.05 g, 0.22 mmol) were placed in a pressure vessel equipped with a magnetic stirrer. Decomposition was carried out at 210 °C for 3 h. After cooling the reaction mixture, water was added to the mixture, and the water was separated using CombiFlash®. This gave pure caprolactam (CPL) (83%) and 2-hydroxyethyl-6-aminohexanoate (HAH) (13%). The yields were calculated using the catalyst signal (d = 1.87 ppm, 4H) and the characteristic signal of BPA (d = 2.05 ppm, 4H) as internal standards in DMSO-d6. 1 Calculated by using 1 H NMR spectroscopy. 1 H NMR (400MHz, DMSO) δ7.72 (s, 1H), 3.00 (d, J=6.7Hz, 2H), 2.03 (t, J=7.4Hz, 2H), 1.63-1.11 (m, 6H).

[0130] <Selective decomposition of mixed polymer pellets>

[0131] PC pellets (0.33 g, 1.30 mmol), PU pellets (0.41 g, 1.33 mmol), PET pellets (0.25 g, 1.3 mmol), PA pellets (0.15 g, 1.30 mmol), EG (3.17 g, 52 mmol), and TBD:TFA catalyst (0.07 g, 0.26 mmol) were loaded into a 30 mL pressure vessel equipped with a magnetic stirrer. In Route A, each depolymerization was carried out at a predetermined temperature (130 °C, 160 °C, 180 °C, and 210 °C for PC, PU, ​​PET, and PA, respectively) for 2 h. At 130 °C, only PC was completely decomposed, while the remaining polymer pellets remained unreacted. At 160 °C, PU was decomposed, while PET and PA remained unchanged. Raising the temperature to 180 °C for another 2 h resulted in the decomposition of PET. Finally, raising the temperature to 210 °C resulted in the decomposition of PA. In Route B, the decomposition was carried out at 210 °C and atmospheric pressure for 3 h. The corresponding products (BPA, MDA, BHET, and CPL) were purified by flash column chromatography using different chloroform:methanol mixtures in ratios ranging from 1:0 to 1:1 to 0:1 as eluents. The crude products in DMSO-d6 were analyzed using the catalyst signal (d = 1.87 ppm, 4H) as an internal standard. 1 Kinetics, conversion, and yield were determined by H NMR spectroscopy: appearance of peaks at 6.99 / 6.44 / 1.53 ppm for BPA, 7.34 / 7.10 ppm for MDA, 8.17 ppm for BHET, and 2.05 ppm for CPL.

[0132] <Recyclability and water sensitivity>

[0133] Considering the environmental and economic viability of the proposed process, the residual reactants and catalyst need to be recycled for further PET degradation. The recyclability was studied after two processes as follows. In the first process (Process-1), after filtering the BHET crystals from the aqueous phase, the unreacted EG and catalyst were dried by vacuum evaporation at 60 °C and then stored overnight in a vacuum oven at 60 °C. Fresh PET flakes were then added to the recycled system [EG + catalyst] using the same procedure. In the second process (Process-2), after complete conversion of PET, another batch of PET and EG were added without catalyst to determine the catalytic activity of the catalyst. TBD: It was observed that in the presence of TFA, the BHET yield remains constant even after 5 recycle processes without loss of catalytic activity. These two methods resulted in BHET very efficiently up to 5 cycles. The catalyst also functions very efficiently in the presence of up to 30% water.

[0134] <Degradation of Commercial Polymers>

[0135] <Degradation of PC, PU, PET, and PA Consumer Goods> Consumer goods made of polymers contain additives and are often manufactured as blends of different polymers. Therefore, the catalytic stability with these composite products was tested in selected experiments. Combinations of plastics (0.5 g) derived from the corresponding polymer consumer goods, TBD:TFA (0.034 g) as catalyst, EG (1.61 g), and temperature for 2 hours (130 °C, 160 °C, 180 °C, and 210 °C for PC, PU, PET, and PA consumer goods, respectively) were subjected to glycolysis conditions. All consumer goods tested were completely degraded. The corresponding products (BPA, MDA, BHET, and CPL) were purified either by crystallization or flash column chromatography. The conversion and yield were determined for the crude product in DMSO-d6 using the catalyst signal (d = 1.87 ppm, 4H) as the internal standard. 1 The peaks were determined by H NMR spectroscopy: 6.99 / 6.44 / 1.53 ppm for BPA, 7.34 / 7.10 ppm for MDA, 8.17 ppm for BHET, and 2.05 ppm for CPL.

[0136] Degradation of Mixed Plastic Consumer Products: In a typical experiment, commercially available polymer-containing items, such as safety goggles (0.33 g, 1.30 mmol), foam (0.41 g, 1.33 mmol), colored bottles (0.25 g, 1.3 mmol), nylon rope (0.15 g, 1.30 mmol), ethylene glycol (3.17 g, 52 mmol), and TBD:TFA catalyst (0.07 g, 0.26 mmol), were loaded into a 30 mL pressure vessel equipped with a magnetic stirrer. For Route A, each decomposition was carried out at a predetermined temperature (130 °C, 160 °C, 180 °C, and 210 °C for PC, PU, ​​PET, and PA consumer products, respectively) for 2 hours. For Route B, decomposition was carried out at 210 °C and atmospheric pressure for 3 hours. The corresponding monomers from each commercial product were purified by flash column chromatography using chloroform:methanol mixtures in ratios of 1:0 to 1:1 to 0:1 as eluents. The crude products were purified in DMSO-d6 using the catalyst signal (d = 1.87 ppm, 4H) as an internal standard. 1 Kinetics, conversion, and yield were determined by H NMR spectroscopy, with peak appearances of 6.99 / 6.44 / 1.53 ppm for BPA, 7.34 / 7.10 ppm for MDA, 8.17 ppm for BHET, and 2.05 ppm for CPL.

[0137] Selective Degradation of Various Plastic Blends The effect of complex polymer blends on catalytic degradation reactions was also examined. The glycolysis of PET bottles and mixed condensation polymers was carried out under standard conditions using TBD:TFA as a catalyst in the presence of poly(propylene) (PP) caps and poly(ethylene) (PE) bags. In these experiments, complete conversion of the selected polymers was observed, and none of the additional polymers listed interfered with the selective degradation of the condensation polymers.

[0138] <Results and Discussion>

[0139] A PIS-based organocatalyst formed from equimolar amounts of TBD and trifluoroacetic acid (TFA) was prepared. The resulting catalyst is referred to herein as TBD:TFA. Figure 2A shows the formation of TBD:TFA. The structure of the aforementioned catalyst was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (PNMR), and NMR spectroscopy (NMR). 1 H NMR) spectroscopy (Figure 2B) and carbon nuclear magnetic resonance ( 13 This was confirmed by C NMR spectroscopy. 1 The H NMR spectrum (Figure 2B) shows the disappearance of the TFA peak at δ 13.84 ppm (Figure 2B, top) and a shift of the TBD peak from δ 4.14 ppm (Figure 2B, bottom) to δ 8.12 ppm, indicating the formation of TBD:TFA (Figure 2B, center). The design of TBD:TFA involves the protonation of TBD (TBDH) at the carbonyl (C=O) group. + ) and the high basicity of the TFA anion during decomposition. 50% =215℃) is the individual TBD (T 50% = 175 °C) and TFA (T 50% This indicates the formation of thermally stable PIS compared to that at 180 °C (=50 °C). Experiments were conducted to investigate the heterogeneous glycolysis of PET (MW 40,000 g / mol) with TBD:TFA as the catalyst and ethylene glycol (EG) as the reactant and solvent at 180 °C for 2 h (Figure 2C), yielding bis(2-hydroxyethyl) terephthalate (BHET) (Figures 2C and 2D). The TBD:TFA-catalyzed PET degradation efficiency was evaluated as a function of EG content (5–20 equiv), catalyst amount (0.05–0.5 equiv), and temperature (150–180 °C). Compared to the reported optimized conditions for PET glycolysis by TBD:MSA (using 10 times the catalyst (50 mol%, 0.5 equiv.) and twice the amount of EG (20 equiv.) to obtain approximately 90% BHET monomer (SR Nicholson et al., Annual Review of Chemical and Biomolecular Engineering, 13(1), 2022)), we degraded PET pellets at 180 °C within 2 h with a much lower catalyst loading (5 mol%, 0.05 equiv.) and a lower amount of EG (10 equiv.) to yield >96% BHET with a low oligomer mixture (<4%).

[0140] TBD:TFA and TBD:MSA were compared at the same loadings of catalyst (0.05 equivalents) and EG (10 equivalents) to decompose PET to BHET at 180°C for 2 hours. TBD:TFA showed significantly higher efficiency, achieving 100% conversion, while TBD:MSA only achieved about 60% conversion. The same experiment was also performed using TBD:TFA as the catalyst with PET of various molecular weights and on a larger scale (10 g) of PET, and no significant difference in the efficiency of PET degradation was observed.

[0141] The catalytic activity of different ratios of TBD:TFA, including 1:0, 1:1, 1:3, 3:1, and 0:1 TBD:TFA, was evaluated to degrade PET in the presence of EG at 180 °C. 1 Analysis of the final crude product by H NMR spectroscopy reveals that reactions using TFA alone or excess TFA degrade PET by only 0% and 20%, respectively, after 2 h at 180 °C. In contrast, TBD alone and excess TBD (3 equivalents) yielded 60% and 100% conversions, respectively, after 2 h, but also yielded mixtures of products other than the BHET monomer (31% and 42%, respectively) and showed poor recyclability due to the limited thermal stability of TBD. The highest yield of BHET monomer (>96%) (Figures 2C and 2D) and small amounts of other oligomers (<4%) was achieved in a solvent-free and facile crystallization method by using a 1:1 TBD:TFA mixture. Notably, the 1:1 TBD:TFA ratio is also referred to herein as TBD:TFA. The formation of BHET as the major product in PET degradation is 1 Further confirmation was achieved by H NMR spectroscopy, matrix-assisted laser desorption / ionization-time of flight mass spectrometry (MALDI-TOF MS), and small-angle neutron scattering (SANS).

[0142] The catalytic activity of TBD:TFA arises from a dual activation mechanism by activating both EG and the polymer chain (Figure 3). The TFA anion activates the intercalating nucleophile, TBDH + activates the polymer chain to be cleaved by coordinating with the C=O group of the polymer chain (Figure 3, Step 2). To understand the catalytic activity and mechanism, two additional catalysts were synthesized as controls. These are designated TBD:mTFA and mTBD:TFA, where mTFA and mTBD stand for methyl-TFA and methyl-TBD, respectively. The glycolysis of PET using TBD:mTFA and mTBD:TFA showed lower conversions (50% and 32%, respectively) and lower BHET yields (65% and 48%, respectively) due to the reduced proton-accepting capacity of mTBD and the absence of labile protons in mTFA (Figure 2E).

[0143] To further elucidate the highly efficient TBD:TFA catalysis, all-electron density functional theory (DFT) calculations using hybrid metafunctional m06-2x and aug-cc-pvdz basis sets were performed on the TBD:TFA catalyst. + This was performed on a model PET chain of eight monomers interacting with TBD and TFA anions. In particular, the TBD:TFA interaction energy in the continuum solvent model was calculated to be 13.6 kcal / mol (ΔG = 3.4 kcal / mol), and initial molecular dynamics (MD) simulations showed that the TBD:TFA complex reacts with TBDDH at relatively low temperatures. + Once dissociated into the cation and anion, DFT results show that TBDH has an interaction energy of 24.7 kcal / mol. + This shows the formation of a stable complex between EG and PET. At the same time, the TFA anion prefers to form a complex with EG with an interaction energy of 30.4 kcal / mol (Figure 3, Step 2). Successive bond formations (Figure 3, Step 3) and bond cleavages give rise to oligomers and finally to monomers.

[0144] Comparing these DFT results with those of the TBD:MSA complex reveals several notable differences. First, the interaction energy between TBD and MSA is slightly higher (14.8 kcal / mol). Second, the MSA anion forms a much stronger interaction with PET at 42 kcal / mol than with TFA at only 13 kcal / mol. Notably, the PET chain, and not just small molecule models, is required to observe this difference, thus indicating the fundamental role of PET conformation. The overall dynamics between TBD:TFA and TBD:MSA for PET degradation are governed by (i) interactions between EG and the anion, and (ii) the interaction of TBDH via hydrogen bonding to activate the electrophilicity of the O-C=O bond. + The stronger interaction between the MSA anion and PET (42 kcal / mol) is due to the interaction of EG and TBDH with OC=O on PET. + On the other hand, the weaker interaction between the TFA anion and PET (13 kcal / mol) and the strong conjugate basicity appear to hinder the activation of EG and TBDH, thus slowing the reaction rate. + and accelerate the interaction between O-C=O on PET, thus enhancing the overall catalytic activity of TBD:TFA (Figure 2E).

[0145] The efficient degradation mechanism of PET by TBD:TFA suggests that TBD:TFA can be applied to cleave all types of functional bonds in condensation polymers. Degradation of PC (bisphenol A-based PC, Mw 45,000 g / mol), PU (diphenylmethylene-ethylene glycol-based PU, Mw 24,600 g / mol), PET (Mw 40,000 g / mol), and PA (nylon 6, Mw 35,000 g / mol) was performed in the presence of TBD:TFA catalyst and EG (Figure 2G). The structural differences in carbonate, urethane, ester, and amide groups in PC, PU, ​​PET, and PA provide sufficiently different thermodynamics to induce tailored degradation rates (Figure 2H). First, PC, PU, ​​PET, and PA were individually degraded using 10 equivalents of EG and 0.05 equivalents of TBD:TFA catalyst at specific temperatures between 110 and 210 °C for 2 h. Complete degradation within 2 hours was demonstrated with yields exceeding 95% for PC to bisphenol A (BPA) at 130 °C (Figure 2H), PU to 4,4'-methylenedianiline (MDA) at 160 °C (Figure 2H), PET to BHET at 180 °C (Figure 2H), and PA to caprolactam (CPL) at 210 °C (Figure 2H). The highly efficient degradation of multiple condensation polymers by a single catalyst, TBD:TFA, represents an important milestone for the chemical recycling of plastics.

[0146] The structural stability of the carbonate, urethane, ester, and amide functional groups in PC, PU, ​​PET, and PA provides distinctly different degradation rates, enabling the selective and sequential degradation of mixed PC, PU, ​​PET, and PA using TBD:TFA catalysts. Therefore, the simultaneous degradation of the assorted PC, PU, ​​PET, and PA was investigated (Figure 4A). All polymer pellets (1.3 mmol each, corresponding to 0.33 g of PC, 0.41 g of PU, 0.25 g of PET, and 0.15 g of PA) were mixed with EG (10 equiv.) and TBD:TFA (0.05 equiv.) in the same vial, and the sequential degradation was monitored at different temperatures. The kinetics of the degradation degree were analyzed using the characteristic signals (B'-E') of each resulting molecule. 1 The decomposition was quantified by H NMR spectroscopy. At 130 °C, only PC was decomposed, yielding 97% BPA after 2 h (B, B'), demonstrating the ability to selectively decompose PC in the presence of PU, PET, and PA (B). By increasing the temperature to 160 °C, PU was decomposed to MDA, and a small amount of PET was also decomposed to BHET (C, C'). Further increasing the temperature to 180 °C decomposed the remainder of the PET to BHET (D, D'). Finally, at 210 °C, PA was decomposed to CPL (E, E'). Alternatively, direct heating of mixed PC, PU, ​​PET, and PA at 210 °C decomposed all polymers to a mixture of their respective monomers, which could be easily separated by fractional distillation or CombiFlash® (V). The ability to decompose these mixed condensation polymers provides a clear route to eliminating the costly separation and recovery of valuable chemicals from mixed plastic waste.

[0147] Figure 4B (top) shows the decomposition of a PET bottle and PP cap mixture to produce BHET while keeping the PP intact. Figure 4B (middle) shows the decomposition of PC, PU, ​​PET, and PA consumer products with PE bag pieces to produce the corresponding monomers BPA, MDA, BHET, and CPL, respectively, while keeping the PE intact. Figure 4B (bottom) shows the decomposition of a polyester (40%) and cotton (60%)-based fabric to produce BHET monomer, with the unreacted cotton easily separated. Figure 4C shows the energy footprints of the production of PC, PU, ​​PET, and PA using the decomposed monomers from the TBD:TFA-based process versus the conventional petroleum-based approach, and Figure 4D shows the carbon footprints.

[0148] The sustainability and economic viability of a catalyst depend on its reusability. Therefore, TBD:TFA was evaluated for multi-cycle reuse following two different glycolytic processes. The yield of each catalytic cycle was measured using the catalyst as an internal standard. 1 The catalytic activity was determined by H NMR spectroscopy. For both processes, the catalyst could be used for at least five cycles, with excellent yields (>90%) for all condensation polymers investigated (Figure 2F). Furthermore, because water tends to impair the efficiency of organocatalysts, the degradation of PET was performed in the presence of water to understand its effect on the TBD:TFA catalytic efficiency. The observed results indicated that up to 30% water did not interfere with the degradation, indicating that the catalyst can directly degrade plastic waste even without drying, thereby saving considerable energy and time in its industrial adoption.

[0149] The properties of plastics are often tailored to their intended use by blending different additives during their production, making the decomposition of discarded plastics even more challenging. Therefore, in this study, the effectiveness of the TBD:TFA catalyst was further evaluated by decomposing selected consumer products based on PC, PU, ​​PET, and PA. First, a commercially available colored PET water bottle was cut into small pieces (0.5 g) and decomposed by filling it with EG (10 equiv.) and TBD:TFA (0.05 equiv.) at 180 °C for 2 h. The water bottle was completely converted to BHET. The same degradation conditions were applied to polyester carpet and fabric, which also showed complete conversion. Similarly, PC-based consumer safety goggles were completely converted to pure BPA. PU and PA consumer PU foam and nylon rope were completely decomposed to the corresponding monomers. These results demonstrate the broad applicability of TBD:TFA for the decomposition of various consumer products and the negligible effect of polymer additives or color pigments on catalytic activity.

[0150] The decomposition of mixed post-consumer plastic waste by selective glycolysis was further investigated. A mixture of safety goggles (PC), PU foam, PET water bottle, and nylon rope (PA) (0.5 g each) from conventional sources was placed in a reaction vessel and heated continuously for 2 hours using EG (10 equivalents) and TBD:TFA (0.05 equivalents). The catalytic efficiency in mixed post-consumer plastic waste was verified. A reaction temperature of 130 °C resulted in the complete conversion of the PC waste to BPA, while the PU, PET, and PA waste remained unconverted. Due to their insolubility in EG, the unreacted PU, PET, and PA wastes could be easily filtered from the reaction solution and further decomposed in subsequent reactions. Increasing the temperature to 160 °C resulted in the complete conversion of the PU foam to MDA, and at a higher temperature of 180 °C, the PET water bottle was completely converted to BHET. The nylon rope remained intact after the decomposition conditions of 160 °C or 180 °C, allowing for easy separation of the nylon rope. The nylon rope is completely decomposed into CPLs when the residue is heated to 210° C. Alternatively, the same consumer mixed plastic waste was decomposed in the same reactor at 210° C. for 2 hours using TBD:TFA catalyst to give a mixture of BPA, MDA, BHET, and CPLs, which were subsequently separated by fractional distillation or CombiFlash®.

[0151] The organocatalyst TBD:TFA can degrade certain plastics (PC, PU, ​​PET, and PA) while leaving others intact due to differences in their reactivity in polymer structure, solvation, and physical and mass transport properties. To evaluate the efficiency and selectivity of TBD:TFA as a catalyst for multiple mixed wastes, we performed TBD:TFA-based glycolysis using (i) a PET bottle with a PP cap (Figure 4F), (ii) a PET bottle with a PE bag, (iii) a PC-, PU-, PET-, and PA-based consumer product mixture with a PE bag (Figure 4G), and (iv) a fabric consisting of 40% polyester and 60% cotton (Figure 4H). Due to the presence of labile bonds (OC=O, ester or NC=O, amide), the condensation polymers show complete conversion to yield their respective monomers while preserving unreacted PP (100%), PE (100%), and cotton (100%). This selective degradation method using TBD:TFA eliminates the need for prior separation of mixed plastics and can also be applied to multi-component plastics such as multi-layer packaging or textiles.

[0152] Assessing energy and carbon inputs is crucial to understanding circular plastics and their environmental impact. Generally, the production of virgin polymers involves a long list of processes, from raw material extraction to waste management processes, which consume between 1.9 and 5.8 kg CO2, respectively. 2 Equivalents / kg polymer and have a considerable impact on embodied carbon and energy demand in the final plastic product ranging from 51 to 176 MJ / kg (SR Nicholson et al., ibid.). Recycling polymer waste and reconstructing new polymer materials has, in some cases, reduced the impact on embodied carbon by a factor of 6 to 10 (PA Wager et al., Science of the Total Environment 2015, 529, 158-167). Life cycle assessment (LCA) modeling is an essential tool for assessing the environmental impact of developed approaches for the individual degradation of each polymer and the generation of reconstructed polymers from recycled monomers.

[0153] Herein, a cradle-to-gate LCA study was conducted to estimate the carbon and energy footprints of chemical recycling of PC, PET, PU, ​​and PA waste, followed by the production of PC, PET, PU, ​​and PA. The analysis considers all options that impact the environment through resource consumption or emissions, including resource use, human health, and ecological impacts. EG and electricity are major contributors to the environmental impact of the polymer degradation process, primarily through their impacts on ozone depletion, global warming, and acidification. Due to the efficient degradation process of each condensation polymer by the TBD:TFA catalyst, the resulting degradation monomers produce the corresponding polymers with low embodied carbon values ​​(0.34–1.41 kg CO2 equivalents) and cumulative energy demands (4.96–32.0 MJ / kg). Comparative LCA analysis shows that the synthesis of PC, PU, ​​PET, and PA from degraded monomers results in 82%, 81%, 75%, and 95% less GHG emissions (Figure 4I) and 68%, 72%, 84%, and 94% less energy input (Figure 4J), respectively, than that from conventional petroleum-based monomers. Furthermore, a comparative LCA model for mixed plastic waste PC, PU, ​​PET, and PA shows a 51% reduction in fossil energy consumption compared to the total energy demand of each polymer individually. The significant reduction in carbon and energy footprints in reconstructed polymers using degraded monomers from the TBD:TFA-based process is attributed to a combination of several factors, including catalyst effectiveness, the ability to recycle excess EG, fast reaction rates, and high yields of polymer degradation. Furthermore, the simultaneous recovery of intact plastics such as polyolefins and cellulose (Figures 4F, 4G, and 4H) is expected to further reduce GHG and energy inputs for the overall circularity of multiple plastics.

[0154] In summary, chemical recycling of condensation polymers, PC, PET, PU, ​​and PA, as well as various blends thereof, has been demonstrated herein to address the global challenge of plastics recycling. Using the process disclosed herein, a wide range of post-consumer plastic waste, such as bottles, packaging, foam, and carpet, can be easily decomposed into monomers with high efficiency. This process is also simple, solvent-free, low-energy, and more environmentally friendly than conventional processes. This approach using the TBD:TFA organocatalyst enables the efficient and versatile conversion of plastic waste into valuable chemicals that can be easily used to regenerate high-value plastics or other valuable materials. The tailored catalyst design enables 100% conversion of polymers to monomers within two hours, using one-tenth the amount of catalyst and half the amount of EG compared to prior art organocatalysts. Furthermore, the reagents and catalyst are easily recyclable, showing the same catalytic activity even after five reactions using the same catalyst. The developed organocatalyst also achieves the degradation of various consumer plastic blends, enabling selective glycolysis of condensation polymers and a facile route to separate other intact polymers. This approach offers highly efficient closed-loop chemical upcycling of mixed plastics through easy degradation and separation, resulting in over 80% reduction in energy and carbon footprint.

[0155] While we have shown and described what are presently considered to be the preferred embodiments of the invention, those skilled in the art can make various changes and modifications which remain within the scope of the invention as defined by the appended claims.< / bhet>

Claims

1. 1. A method for decomposing polymeric waste into at least one useful decomposition product, wherein the polymeric waste comprises at least one condensation polymer, the method comprising contacting the polymeric waste with a catalyst comprising an organic nitrogen-containing base and a carboxylic acid or ester thereof in the presence of protic molecules selected from alcohols, diols, polyols, and amines at an elevated temperature effective to induce alcoholysis or aminolysis of the condensation polymer, the useful decomposition product comprising a monomeric species capable of polymerization, the organic nitrogen-containing base having the structure: 【Chemistry 1】 [where: R １ , R ２ , R ３ , R ４ , R ５ , and R ６ are independently selected from a hydrogen atom, an electron pair, and an alkyl group containing 1 to 3 carbon atoms; R １ and R ２ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; R ２ and R ３ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; R ３ and R ４ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; R ４ and R ６ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; R ５ and R ６ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; R １ and R ５ may optionally be interconnected to form a 5-, 6-, or 7-membered ring; X is C, CR ａ , or N, and R ａ is selected from a hydrogen atom and an alkyl group containing 1 to 3 carbon atoms; The dotted line represents an optional double bond.]

2. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Chemistry 2】 [In the formula, R ２ , R ３ , R ４ , R ６ and X is as defined in claim 1, and r has a value of 0, 1 or 2.

3. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Transformation 3】 [where R ２ , R ３ , R ４ , R ６ and X is as defined in claim 1.

4. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Chemistry 4】 [where R ４ , R ６ and X are as defined in claim 1, and r and s each independently represent a value of 0, 1, or 2.

5. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Transformation 5】 [where R ４ , R ６ and X is as defined in claim 1.

6. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Transformation 6】 [where R ４ and R ６ is as defined in claim 1, and r and s each independently represent a value of 0, 1, or 2.

7. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Transformation 7】 [where R ４ and R ６ is as defined in claim 1.

8. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Transformation 8】 [where R ６ is as defined in claim 1.

9. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Chemistry 9】 [where R ４ is as defined in claim 1.

10. 2. The method of claim 1, wherein the organic nitrogenous base has the following structure: 【Chemistry 10】 [where R １ , R ３ , R ４ , R ５ , R ６ , and X is R １ , R ３ , R ４ , R ５ , and R ６ As defined in claim 1, except that none of the are permitted to be interconnected.

11. 11. The method of any one of claims 1 to 10, wherein the carboxylic acid or ester thereof has the following structure: 【Chemistry 11】 [where: R is a hydrogen atom or a hydrocarbon group containing 1 to 12 carbon atoms and one or more halogen atoms and / or OR ｂ group, or may be substituted by another carboxylic acid group or ester thereof, R ｂ is selected from a hydrogen atom and an alkyl group containing 1 to 3 carbon atoms.

12. 12. The method of claim 11, wherein R is a hydrocarbon group containing 1 to 6 carbon atoms optionally substituted with one or more halogen atoms.

13. 12. The method of claim 11, wherein R is a hydrocarbon group containing 1 to 3 carbon atoms optionally substituted with one or more halogen atoms.

14. 12. The method of claim 11, wherein the carboxylic acid or ester thereof is trifluoroacetic acid or an ester thereof.

15. The method according to any one of claims 1 to 10, wherein the protic molecule is a diol.

16. 16. The method of claim 15, wherein the diol is ethylene glycol.

17. The method of any one of claims 1 to 10, wherein the condensation polymer is selected from at least one of the group consisting of polyesters, polyurethanes, polycarbonates, and polyamides.

18. The method according to any one of claims 1 to 10, wherein the polymer waste contains at least two different types of condensation polymers.

19. The method of any one of claims 1 to 10, wherein the polymer waste comprises polyester.

20. 20. The method of claim 19, wherein the polyester is polyethylene terephthalate.

21. 21. The method of claim 20, wherein the at least one useful decomposition product is bis(2-hydroxyethyl) terephthalate.

22. 11. The process of any one of claims 1 to 10, wherein the organic nitrogen-containing base (B) and carboxylic acid or ester thereof (A) are present in a B:A molar ratio in the range of 0.05:1 to 1:0.

05.

23. 11. The process of any one of claims 1 to 10, wherein the organic nitrogen-containing base (B) and carboxylic acid or ester thereof (A) are present in a B:A molar ratio in the range of 0.2:1 to 1:0.

2.

24. 11. The process of any one of claims 1 to 10, wherein the organic nitrogen-containing base (B) and carboxylic acid or ester thereof (A) are present in a B:A molar ratio in the range of 0.5:1 to 1:0.

5.

25. 11. The process of any one of claims 1 to 10, wherein the organic nitrogen-containing base (B) and carboxylic acid or ester thereof (A) are present in a B:A molar ratio of about 1:1.

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