A highly efficient catalytic system and method for pyrolysis of polyβ-hydroxybutyrate.

Abstract

A highly efficient catalytic system and method for the pyrolysis of poly(β-hydroxybutyrate). This invention belongs to the field of organic material chemical recycling technology. This invention addresses the technical problem that existing methods for pyrolyzing waste poly(β-hydroxybutyrate) typically use metal catalysts and require harsh conditions (high temperature, high pressure), lacking a green catalytic system and method for the rapid and efficient pyrolysis of poly(β-hydroxybutyrate) under mild conditions. The catalytic system of this invention, using an organic base as a catalyst, can achieve a yield of ≥80% within 1-3 hours under normal pressure and temperature not exceeding 150°C, exhibiting high catalytic efficiency. It can catalyze the rapid and efficient pyrolysis of poly(β-hydroxybutyrate) under mild conditions, avoiding the increased energy consumption caused by high temperature and high pressure reaction conditions. Furthermore, the organic base catalyst is metal-free, posing less environmental harm and avoiding the ecological damage caused by using other toxic metal catalysts.

Description

Technical Field

[0001] This invention belongs to the field of organic material chemical recycling technology, specifically relating to a highly efficient catalytic system and method for catalytic pyrolysis of polyβ-hydroxybutyrate. Background Technology

[0002] Poly(β-hydroxybutyrate) (PHB) is a microbially synthesized polyester that is not only biodegradable and biocompatible, but also possesses excellent physical and mechanical properties. Therefore, PHB has attracted widespread attention as an alternative to petroleum-based plastics and non-biodegradable plastics.

[0003] With the large-scale production of poly(β-hydroxybutyrate) plastics, poly(β-hydroxybutyrate) plastic waste is also generated. Recycling and reusing poly(β-hydroxybutyrate) plastics remains a significant challenge. Poly(β-hydroxybutyrate) can be chemically recycled into high-value small molecules, and some research has been conducted on the pyrolysis of poly(β-hydroxybutyrate) to recover crotonic acid. For example, using MgO or Mg(OH)₂ as a catalyst in a glass tube oven at 240°C can yield crotonic acid with high yield and selectivity. Ionic liquids can also be used as catalysts and solvents, achieving conversion rates as high as 97% at 140°C. However, most of the currently reported methods for the pyrolysis of poly(β-hydroxybutyrate) to recover crotonic acid require harsh high-temperature reaction conditions, complex synthesis processes, or expensive catalysts. Therefore, a catalytic system for the rapid, economical, and efficient pyrolysis of poly(β-hydroxybutyrate) under mild conditions is lacking. Summary of the Invention

[0004] This invention addresses the technical problem that existing methods for pyrolyzing waste poly(β-hydroxybutyrate) typically use metal catalysts and require harsh conditions (high temperature, high pressure), lacking a green catalytic system and method for rapid and efficient pyrolysis of poly(β-hydroxybutyrate) under mild conditions. Therefore, this invention provides a green and efficient catalytic system and method for the pyrolysis of poly(β-hydroxybutyrate), which helps to achieve the green recycling of waste poly(β-hydroxybutyrate) plastics.

[0005] The technical solution of this invention:

[0006] One objective of this invention is to provide a highly efficient catalytic system for the pyrolysis of polyβ-hydroxybutyrate, the catalytic system comprising an organic base catalyst and a polar organic solvent.

[0007] Further specifying, the organic base catalyst is selected from phosphazene bases or nitrogen-containing organic bases.

[0008] Furthermore, the phosphazene base is one or a mixture of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1), 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2Λ5,4Λ5-di-bi(phosphine nitrogen compound) (t-BuP2), and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-di[tris(dimethylamino)-phosphine imino]-2Λ5,4Λ5-di-bi(phosphine nitrogen compound) (t-BuP4).

[0009] Furthermore, the nitrogen-containing organic base is one or a mixture of 1,8-diazobisspirocyclic [5.4.0]undec-7-ene (DBU), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 157-triazidobiscyclo[4.4.0]dec-5-ene (TBD), and 4-dimethylaminopyridine (DMAP).

[0010] Further specified, the polar organic solvent is one or a mixture of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile (MeCN), and toluene.

[0011] The second objective of this invention is to provide a method for catalytic pyrolysis of polyβ-hydroxybutyrate using the above-mentioned catalytic system. The method is as follows: under normal pressure and inert gas protection, the catalytic system is used to catalyze the depolymerization of polyβ-hydroxybutyrate to obtain crotonic acid (CA).

[0012] Further specifying, the amount of organic base catalyst in the catalytic system is 0.1 to 50 wt% of polyβ-hydroxybutyrate.

[0013] Further, the concentration of poly-β-hydroxybutyrate in the catalytic system is specified to be 0.01M to 100M.

[0014] Further, the depolymerization temperature is specified as 20–300℃, and the time is specified as 1–6 hours.

[0015] Furthermore, the depolymerization temperature is specified as 110–150°C.

[0016] Further specifying, the number-average molecular weight (M) of polyβ-hydroxybutyrate is... n ) is 10 2 ~10 7 g / mol.

[0017] The advantages of this invention compared to the prior art are as follows:

[0018] (1) The present invention uses a green and environmentally friendly metal catalyst to catalyze the pyrolysis of polyβ-hydroxybutyrate. The organic base catalyst does not contain metal, has little harm to the environment, and can avoid the harm to the ecological environment caused by other toxic metal catalysts.

[0019] (2) The catalytic system of the present invention can achieve a yield of ≥80% within 1-3 hours under normal pressure conditions not exceeding 150°C. It can be seen that the catalytic system of the present invention has high catalytic efficiency and can catalyze the rapid and efficient pyrolysis of polyβ-hydroxybutyrate under mild conditions, avoiding the energy consumption increase caused by reaction conditions such as high temperature and high pressure.

[0020] (3) This invention can use organic solvents of various polarities. It can recover high-value-added small organic molecules with high yield, thereby realizing the high-yield recycling of polyβ-hydroxybutyrate materials. Attached Figure Description

[0021] Figure 1 Crotonic acid, a degradation product of polyβ-hydroxybutyrate in Example 1. 1 HNMR spectrum;

[0022] Figure 2 Crotonic acid, a degradation product of polyβ-hydroxybutyrate in Example 1. 13 C10 NMR spectrum. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0027] Example 1: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0028]

[0029] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =69.4 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out with stirring at 150 °C in a fume hood. After 1 hour of reaction, samples were taken for NMR monitoring. The 1H and 1C NMR spectra of the product crotonic acid are shown below. Figure 1-2 As shown, the results indicated that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 400 mg of white crotonic acid crystals were obtained, with a yield of 93%.

[0030] Example 2: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0031]

[0032] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =69.4 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMSO. The reaction was carried out in a fume hood at 150 °C with stirring. After 1.5 hours of reaction, a sample was taken for NMR monitoring. The characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 386 mg of white crotonic acid crystals were obtained, with a yield of 89%.

[0033] Example 3: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0034]

[0035] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n=69.4 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of MeCN. The reaction was carried out in a fume hood at 150 °C with stirring. After 1.5 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 375 mg of white crotonic acid crystals were obtained, with a yield of 87%.

[0036] Example 4: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0037]

[0038] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =69.4 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of Toluene. The reaction was carried out in a fume hood at 150 °C with stirring. After 2 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 360 mg of white crotonic acid crystals were obtained, with a yield of 83%.

[0039] Example 5: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0040]

[0041] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out with stirring at 130 °C in a fume hood. After 3 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 398 mg of white crotonic acid crystals were obtained, with a yield of 92%.

[0042] Example 6: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0043]

[0044] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out with stirring at 110 °C in a fume hood. After 5 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 390 mg of white crotonic acid crystals were obtained, with a yield of 90%.

[0045] Example 7: The reaction process of tert-butylimino-tris(dimethylamino)phosphine (t-BuP1) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0046]

[0047] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 860 mg (10 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 24.43 mg of t-BuP1 catalyst (0.1 mmol, 1 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 6 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 380 mg of white crotonic acid crystals were obtained, with a yield of 88%.

[0048] Example 8: The reaction process of 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2Λ5,4Λ5-di-di(phosphorus nitrogen compound) (t-BuP2) catalyzed pyrolysis of polyβ-hydroxybutyrate is shown below:

[0049]

[0050] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n=75.1 kg / mol), 50 μL of t-BuP2 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 1 hour of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 370 mg of white crotonic acid crystals were obtained, with a yield of 86%.

[0051] Example 9: The reaction process of 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-n-phosphine-iminoamino]-2Λ5,4Λ5-di-bi(phosphine-nitrogen compound) (t-BuP4) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0052]

[0053] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 125 μL of t-BuP4 catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out with stirring at 150 °C in a fume hood. After 1 hour of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 355 mg of white crotonic acid crystals were obtained, with a yield of 82%.

[0054] Example 10: The reaction process of 1,8-diazobispiro[5.4.0]undecyl-7-ene (DBU) catalyzing the pyrolysis of polyβ-hydroxybutyrate is shown below:

[0055]

[0056] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 g / mol), 15.2 mg of DBU catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 1 hour of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 380 mg of white crotonic acid crystals were obtained, with a yield of 88%.

[0057] Example 11: The reaction process of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) catalyzed pyrolysis of polyβ-hydroxybutyrate is shown below:

[0058]

[0059] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 15.3 mg of MTBD catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 1 hour of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 362 mg of white crotonic acid crystals were obtained, with a yield of 84%.

[0060] Example 12: The reaction process of 157-triazidobicyclo(4.4.0)dec-5-ene (TBD) catalyzed pyrolysis of polyβ-hydroxybutyrate is shown below:

[0061]

[0062] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n =75.1 kg / mol), 13.9 mg of TBD catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 2 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 350 mg of white crotonic acid crystals were obtained, with a yield of 81%.

[0063] Example 13: The reaction process of 4-dimethylaminopyridine (DMAP) catalyzed pyrolysis of polyβ-hydroxybutyrate is shown below:

[0064]

[0065] Take a 5 mL Schlenk flask, heat it under vacuum and replace it with argon gas, then add 430 mg (5 mmol polymer repeating unit) of poly-β-hydroxybutyrate (M) in a glove box. n=75.1 kg / mol), 12.2 mg of DMAP catalyst (0.1 mmol, 2 mol% relative to the polymer repeating unit) was added, followed by 2 mL of DMF. The reaction was carried out in a fume hood at 150 °C with stirring. After 6 hours of reaction, NMR monitoring showed that the characteristic peaks of the polymer disappeared, and the conversion rate of polymer pyrolysis was greater than 99%. After removing the solvent by vacuum distillation and then purifying by column chromatography, 373 mg of white crotonic acid crystals were obtained, with a yield of 86%.

[0066] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A catalytic polymerization β The method for pyrolysis of hydroxybutyrate, characterized in that... Catalytic polymerization is carried out under normal pressure and inert gas protection using a catalytic system. β The hydroxybutyrate is depolymerized to yield crotonic acid. The catalytic system is selected from an organic base catalyst and a polar organic solvent. The organic base catalyst is selected from phosphazene bases or nitrogen-containing organic bases. The phosphazene base is... t -BuP1、 t -BuP2、 t One or more of -BuP4, nitrogen-containing organic bases are one or more of DBU, MTBD, TBD, and DMAP, and polar organic solvents are one or more of DMF, DMSO, acetonitrile, and toluene.

2. The method according to claim 1, characterized in that, The amount of organic base catalyst used in the catalytic system is poly β 0.1 to 50 wt% of hydroxybutyrate.

3. The method according to claim 1, characterized in that, Polymerization in catalytic systems β The concentration of hydroxybutyrate is 0.01M~100M.

4. The method according to claim 1, characterized in that, The depolymerization temperature is 20~300℃, and the time is 1~6 h.

5. The method according to claim 4, characterized in that, The depolymerization temperature is 110~150℃.

6. The method according to claim 1, characterized in that, Gather β 2-hydroxybutyrate M n 10 2 ~10 7 g / mol.

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