A method for degrading a polyester plastic

Abstract

The application provides a degradation method of polyester plastics, which comprises the following steps: adding a catalyst and polyester plastics into a reaction kettle, stirring under a hydrogen atmosphere, and reacting to obtain a degradation product; wherein the mass ratio of the catalyst to the polyester plastics is (0.1-1):1, the pressure of the hydrogen is 1-5 MPa, and the reaction temperature is 120-250 DEG C. The polyester plastics are degraded by the above steps, recycling of the polyester plastics is realized, and the polyester plastics are converted into high-value degradation products.

Description

Technical Field

[0001] This application relates to the field of organic intermediate synthesis technology, and in particular to a method for degrading polyester plastics. Background Technology

[0002] Since its invention, plastic has been widely used in various fields, bringing great convenience to human production and life. However, its enormous usage and waste have led to increasingly serious environmental pollution. The recycling and reuse of waste plastic has become a major issue concerning the ecological environment and the fate of humanity.

[0003] Polyester plastics are a general term for polymers obtained by the condensation polymerization of alcohols and acids. They come in many varieties, and their properties vary depending on the raw materials or intermediates. Because their units are linked by ester groups "-COO-", they are collectively called polyesters. The production capacity of polyester materials is about to exceed 100 million tons, and they are widely used in chemical fibers, packaging, films, foam materials, and engineering plastics. While bringing many conveniences, they have also caused serious environmental problems. Currently, most polyesters cannot be naturally degraded. Although some polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), and polybutylene succinate (PBS), are called biodegradable plastics, their degradation rate in the natural environment is extremely slow. Furthermore, the direct degradation of polyester plastics generates a large amount of carbon dioxide, increasing carbon emissions and losing carbon resources. Therefore, how to achieve the recycling of polyester plastics has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide a method for degrading polyester plastics, enabling the recycling of polyester plastics and converting them into high-value degradation products. The specific technical solution is as follows:

[0005] This application provides a method for degrading polyester plastics, which includes the following steps:

[0006] A catalyst and polyester plastic were added to a reaction vessel, and under a hydrogen atmosphere, the mixture was stirred to obtain degradation products.

[0007] The mass ratio of the catalyst to the polyester plastic is (0.1-1):1, the pressure of the hydrogen gas is 1-5 MPa, and the reaction temperature is 120-250℃.

[0008] By employing the above steps, a reaction route for the catalytic hydrogenation of polyester plastics to prepare degradation products was realized in a reactor, representing a novel pathway for the degradation and transformation of polyester plastics. The polyester plastic degradation method provided in this application effectively achieves the recycling of polyester plastics, converting them into high-value degradation products. The single-pass yield of the degradation products can reach over 99%.

[0009] This application does not impose any particular restrictions on the type of reaction vessel. Those skilled in the art can choose according to the actual situation, as long as the purpose of this application can be achieved.

[0010] This application does not impose any particular limitation on the reaction time described above. Those skilled in the art can select the appropriate time based on the actual degradation process, the size of the reaction vessel, and the amounts of polyester plastics, catalysts, solvents, etc. For example, the reaction time can be 2-200 hours.

[0011] In one embodiment of this application, a solvent is further added to the reaction vessel, and the mass ratio of the solvent to the polyester plastic is (3-100):1. The stirring method is mechanical stirring or magnetic stirring, with the mechanical stirring speed being 300-1000 rpm and the magnetic stirring speed being 300-800 rpm. Preferably, mechanical stirring is used, as it is more conducive to improving the yield of degradation products. Adding a solvent to the reaction vessel allows the solvent to react with the polyester plastic and the catalyst, which is more conducive to mass transfer in the reaction system and the depolymerization of the polyester plastic, thereby increasing the reaction rate of the polyester plastic and the yield of degradation products.

[0012] In one embodiment of this application, there is no particular limitation on the type of solvent, as long as it can achieve the purpose of this application. For example, the solvent is selected from at least one of dioxane, tetrahydrofuran, methanol, ethanol, ethylene glycol, 1,2-propanediol, 1,4-butanediol, and 1,6-hexanediol.

[0013] In one embodiment of this application, no solvent is added to the reaction vessel, and the stirring method is magnetic stirring at a speed of 300-800 rpm. When no solvent is added to the reaction vessel, the polyester plastic and the catalyst react in a solid-to-solid reaction. Using magnetic stirring ensures sufficient contact between the polyester plastic and the catalyst, which is more conducive to obtaining a higher yield of degradation products.

[0014] In one embodiment of this application, before use, the catalyst is pre-reduced in a reducing gas at 200-600°C for 4-12 hours, wherein the reducing gas is selected from hydrogen or diluted hydrogen. The catalyst pre-reduced by the above steps exhibits superior reactivity when applied to the degradation reaction of polyester plastics, resulting in excellent conversion rates of polyester plastics and higher yields of degradation products.

[0015] In one embodiment of this application, the volume ratio of argon to hydrogen in the diluted hydrogen is (80-95):(5-20). Using the aforementioned diluted hydrogen in the degradation of polyester plastics is more conducive to improving the yield of degradation products.

[0016] In one embodiment of this application, the catalyst is selected from any one of Co / SiO2, Ru / TiO2, Cu / ZnO, CeCu, ZrCu, CuZnZr, CuZnTi, CuZnAl, and CuZnSi. The selection of any of these catalysts allows for the catalytic hydrogenation of polyester plastics to yield degradation products. Preferably, when the catalyst is selected from ZrCu and CuZnSi, the degradation of polyester plastics yields a higher yield of degradation products. More preferably, when the catalyst is CuZnSi, the degradation of polyester plastics yields an even higher yield of degradation products.

[0017] This application does not impose any particular restrictions on the preparation method of the catalyst, as long as it can achieve the purpose of this application.

[0018] For example, a method for preparing Co / SiO2 (Ru / TiO2 or Cu / ZnO) includes the following steps: using a metal salt as a precursor, weigh 0.01-24.7 g of metal salt and 0.1-10 g of oxide support according to a metal loading of 1-50%. Dissolve the metal salt in 30 mL of water (the mass of the oxide support in g), and magnetically stir at 300 rpm for 30 min to form a precursor solution. Then, add the oxide support to the precursor solution and magnetically stir at 300 rpm for 24 h. The resulting suspension is evaporated to dryness at 45 °C, -0.09 MPa vacuum, and 100 rpm, and then dried at 110 °C for 12 h. After grinding the resulting solid, calcine it in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 6 h to obtain Co / SiO2 (Ru / TiO2 or Cu / ZnO). This application does not impose any particular restrictions on the types of metal salts and oxide supports mentioned above. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved. For example, when preparing Co / SiO2, the metal salt is Co(NO3)2·6H2O and the oxide support is SiO2; when preparing Ru / TiO2, the metal salt is RuCl3 and the oxide support is TiO2; when preparing Cu / ZnO, the metal nitrate is Cu(NO3)2·3H2O and the oxide support is ZnO.

[0019] For example, the preparation method of CeCu includes the following steps: Weigh 0.03-309.9 g of cerium nitrate hexahydrate and 0.38-38.0 g of copper nitrate trihydrate according to the molar ratio of Ce:Cu = 1:10-10:1, and prepare an ethanol solution with a total metal ion content of 0.2 mol / L. Under magnetic stirring at 300 rpm, add a 0.5 mol / L oxalic acid ethanol solution with a content five times that of the total metal ion content, and stir for 30 min. After centrifugation, the resulting suspension is washed three times with water and ethanol respectively, and the solid is dried at 110℃ for 12 h. After grinding, the resulting solid is calcined in a muffle furnace at a rate of 2℃ / min to 400℃ for 2 h to obtain CeCu.

[0020] For example, the preparation method of ZrCu includes the following steps: Weigh 0.05-470.6 g of zirconium nitrate pentahydrate and 0.38-38.0 g of copper nitrate trihydrate according to the Zr:Cu molar ratio of 1:10-10:1, and prepare an ethanol solution with a total metal ion content of 0.2 mol / L. Under magnetic stirring at 300 rpm, add a 0.5 mol / L oxalic acid ethanol solution with a content five times that of the total metal ion content, and stir for 30 min. After centrifugation, the resulting suspension is washed three times with water and ethanol respectively, and the solid is dried at 110℃ for 12 h. After grinding, the resulting solid is calcined in a muffle furnace at a rate of 2℃ / min to 400℃ for 2 h to obtain ZrCu.

[0021] For example, the preparation method of CuZnZr includes the following steps: Weigh 0.025-362.1g of copper nitrate trihydrate, 0.002-151.7g of zinc nitrate hexahydrate, and 0.47-47.0g of zirconium nitrate pentahydrate according to the molar ratio of Cu:Zn = 10:(0.5-5) and the molar ratio of (Cu+Zn):Zr = 1:10-10:1. Prepare an ethanol solution with a total metal ion content of 0.2mol / L. Under magnetic stirring at 300rpm, add a 0.5mol / L oxalic acid ethanol solution with a content 5 times that of the total metal ions, and stir for 30min. After centrifugation, the resulting suspension is washed three times with water and ethanol respectively, and the solid is dried at 110℃ for 12h. After grinding, the resulting solid is calcined in a muffle furnace at a rate of 2℃ / min to 400℃ for 2h to obtain CuZnZr.

[0022] For example, the preparation method of CuZnAl includes the following steps: Weigh 0.025-362.1g of copper nitrate trihydrate, 0.002-151.7g of zinc nitrate hexahydrate, and 1.39-139.0g of aluminum nitrate nonahydrate according to the molar ratio of Cu:Zn = 10:(0.5-5) and the molar ratio of (Cu+Zn):Al = 1:10-10:1, and prepare an aqueous solution with a total metal ion concentration of 1mol / L. Under stirring conditions of 65℃ and 300rpm, add 3mol / L of Na2CO3 aqueous solution to make the pH of the solution 8-9. After stirring the resulting suspension for 12 h, centrifuge and wash the solid, and dry it at 110℃ for 12 h. After grinding the obtained solid, calcine it in a muffle furnace at a rate of 2℃ / min to 400℃ for 2 h to obtain CuZnAl.

[0023] For example, the preparation method of CuZnTi includes the following steps: Weigh 0.025-362.1g of copper nitrate trihydrate, 0.002-151.7g of zinc nitrate hexahydrate, and 0.396-39.6g of titanium tetrachloride according to the molar ratio of Cu:Zn = 10:(0.5-5) and the molar ratio of (Cu+Zn):Ti = 1:10-10:1, and prepare an aqueous solution with a total metal ion concentration of 1mol / L. Under stirring conditions of 65℃ and 300rpm, add 3mol / L of Na2CO3 aqueous solution to make the pH of the solution 8-9. After stirring the resulting suspension for 12h, centrifuge and wash the solid, and dry it at 110℃ for 12h. After grinding the obtained solid, calcine it in a muffle furnace at a rate of 2℃ / min to 400℃ for 2h to obtain CuZnTi.

[0024] For example, the preparation method of CuZnSi includes the following steps: Weigh 0.025-362.1 g of copper nitrate trihydrate and 0.002-151.7 g of zinc nitrate hexahydrate according to a Cu:Zn molar ratio of 10:(0.5-5), and prepare a 0.2 mol / L ethanol + water aqueous solution, wherein the ethanol:water ratio is 2:1 (volume ratio), labeled as solution 1. Simultaneously, weigh 0.742-74.2 g of tetraethyl orthosilicate according to a Cu+Zn:Si molar ratio of 1:10-10:1, and prepare a 1.5 mol / L ethanol solution, labeled as solution 2. Mix solution 1 and solution 2, stir at 300 rpm for 30 min, labeled as solution 3. Take 0.1-20 g of ammonium carbonate and prepare a 0.25 mol / L aqueous solution, labeled as solution 4. Take the same volume of water as solution 3, label it solution 5, and heat it to 85°C at 300 rpm, then reflux the cooled water. Add solution 3 to solution 5 at a rate of 50 mL / min, while simultaneously adding solution 4 dropwise to maintain the pH of solution 5 at 7-7.5. After stirring the resulting suspension for 20 h, centrifuge, wash, and dry the solid at 110°C for 12 h. Grind the resulting solid and calcine it in a muffle furnace at a rate of 2°C / min to 400°C for 2 h to obtain CuZnSi.

[0025] In one embodiment of this application, there is no particular limitation on the type of polyester plastic, as long as it achieves the purpose of this application. For example, the polyester plastic is selected from any one of polylactic acid (PLA), polyglycolic acid (PGA), polybutylene succinate (PBS), and polybutylene adipate (PBA). This application also does not have a particular limitation on the weight-average molecular weight of the polyester plastic, as long as it achieves the purpose of this application.

[0026] In one embodiment of this application, there is no particular limitation on the type of degradation products, as long as they can achieve the purpose of this application. For example, the degradation products are selected from any one of 1,2-propanediol (PDO), ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

[0027] In this application, yield refers to the ratio of the actual product output obtained from inputting a unit quantity of raw materials (i.e., polyester plastics) to the theoretically calculated product output.

[0028] Beneficial effects of the embodiments in this application:

[0029] This application provides a method for degrading polyester plastics, comprising the following steps: adding a catalyst and polyester plastics to a reaction vessel, stirring under a hydrogen atmosphere, and reacting to obtain degradation products; wherein the mass ratio of the catalyst to the polyester plastics is (0.1-1):1, the pressure of the hydrogen is 1-5 MPa, and the reaction temperature is 120-250℃. By using the above steps to degrade polyester plastics, the recycling of polyester plastics is achieved, converting polyester plastics into high-value degradation products.

[0030] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0032] Figure 1 This is a reaction performance diagram of PLA hydrogenation to PDO at different reaction times in Example 13 of this application;

[0033] Figure 2 The graph shows the hydrogenation reaction performance of PLA (polyester plastic) in solvent PDO at different reaction times.

[0034] Figure 3 This is a graph showing the hydrogenation reaction performance of a large amount (5g) of polyester plastic PLA in solvent PDO at different reaction times in Example 25 of this application;

[0035] Figure 4 This is a graph showing the reaction performance of the polyester plastic PLA in Example 26 of this application under solvent-free conditions. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0037] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0038] Test methods and equipment

[0039] The reaction systems of each embodiment and comparative example were qualitatively and quantitatively analyzed by gas chromatography.

[0040] Example 1

[0041] <Preparation of Co / SiO2 catalyst>

[0042] Using Co metal salt Co(NO3)2·6H2O as a precursor, 0.0988 g of Co metal salt Co(NO3)2·6H2O and 0.18 g of oxide support SiO2 were weighed according to a metal loading of 10%. Co metal salt Co(NO3)2·6H2O was dissolved in 5.4 mL of water and magnetically stirred at 300 rpm for 30 min to form a precursor solution.

[0043] Subsequently, 0.18 g of the oxide support SiO2 was added to the precursor solution and magnetically stirred at 300 rpm for 24 h to obtain a suspension. The resulting suspension was evaporated to dryness by rotary evaporation at 45 °C, -0.09 MPa vacuum, and 100 rpm, followed by drying at 110 °C for 12 h. The resulting solid was ground and then calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 6 h to obtain 0.2 g of the catalyst Co / SiO2.

[0044] <Pre-reduction of catalyst>

[0045] 0.2 g of catalyst Co / SiO2 was placed in a reducing gas diluted with hydrogen (argon and hydrogen in a volume ratio of 95:5, referred to as 5% H2) and pre-reduced at 300 °C for 4 h.

[0046] <Degradation of Polyester Plastics>

[0047] 0.2 g of the pre-reduction treated catalyst Co / SiO2, 0.5 g of PLA (weight average molecular weight 80,000), and 30 g of ethylene glycol solvent were added to a reactor (manufacturer: Beijing Century Senlang Experimental Instrument Co., Ltd., model: AC100). The reactor was mechanically stirred at 700 rpm under a hydrogen atmosphere at 4 MPa and reacted at 180 °C for 4 h to obtain a solution containing the degradation product PDO. The yield of PDO was 21.8%.

[0048] Example 2

[0049] <Preparation of the catalyst Ru / TiO2>

[0050] Using Ru metal salt RuCl3 as a precursor, 0.0205 g of Ru metal salt RuCl3 and 0.19 g of oxide support TiO2 were weighed according to a metal loading of 5%. The Ru metal salt RuCl3 was dissolved in 5.7 mL of water and magnetically stirred at 300 rpm for 30 min to form a precursor solution.

[0051] The rest was the same as in Example 1, and 0.2 g of catalyst Ru / TiO2 was prepared.

[0052] <Pre-reduction of catalyst>

[0053] Except for replacing Co / SiO2 with Ru / TiO2, everything else is the same as in Example 1.

[0054] <Degradation of Polyester Plastics>

[0055] Except for replacing Co / SiO2 with Ru / TiO2, the rest is the same as in Example 1, wherein the yield of PDO is 7.6%.

[0056] Example 3

[0057] <Preparation of Cu / ZnO Catalyst>

[0058] Using Cu metal salt Cu(NO3)2·3H2O as a precursor, 0.0760 g of Cu(NO3)2·3H2O and 0.18 g of oxide support ZnO were weighed according to a metal loading of 10%. The Cu(NO3)2·3H2O was dissolved in 5.4 mL of water and magnetically stirred at 300 rpm for 30 min to form a precursor solution.

[0059] The rest was the same as in Example 1, and 0.2 g of the catalyst Cu / ZnO was prepared.

[0060] <Pre-reduction of catalyst>

[0061] Except for replacing Co / SiO2 with Cu / ZnO, everything else is the same as in Example 1.

[0062] <Degradation of Polyester Plastics>

[0063] Except for replacing Co / SiO2 with Cu / ZnO, the rest is the same as in Example 1, wherein the yield of PDO is 6.9%.

[0064] Example 4

[0065] <Preparation of the catalyst CeCu>

[0066] Weigh 0.1075 g of cerium nitrate hexahydrate and 0.5983 g of copper nitrate trihydrate according to a Ce:Cu molar ratio of 1:10, and prepare an ethanol solution with a total metal ion concentration of 0.2 mol / L. Under magnetic stirring at 300 rpm, add a 0.5 mol / L oxalic acid-ethanol solution, five times the amount of total metal ions, and stir for 30 min. After centrifugation, the resulting suspension is washed three times each with water and ethanol, and the solid is dried at 110 °C for 12 h. The resulting solid is then ground and calcined in a muffle furnace at a rate of 2 °C / min to 400 °C for 2 h to obtain 0.2 g of the catalyst CeCu.

[0067] <Pre-reduction of catalyst>

[0068] Except for replacing Co / SiO2 with CeCu, the rest is the same as in Example 1.

[0069] <Degradation of Polyester Plastics>

[0070] Except for replacing Co / SiO2 with CeCu, the rest is the same as in Example 1, wherein the yield of PDO is 5.5%.

[0071] Example 5

[0072] <Preparation of ZrCu catalyst>

[0073] Except for replacing cerium nitrate hexahydrate with zirconium nitrate pentahydrate, using 0.3929 g of zirconium nitrate pentahydrate, using 0.3317 g of copper nitrate trihydrate, and using a Zr:Cu molar ratio of 4:6, the rest was the same as in Example 4. 0.2 g of catalyst ZrCu was obtained.

[0074] <Pre-reduction of catalyst>

[0075] Except for replacing Co / SiO2 with ZrCu, the rest is the same as in Example 1.

[0076] <Degradation of Polyester Plastics>

[0077] Except for replacing Co / SiO2 with ZrCu, the rest is the same as in Example 1, wherein the yield of PDO is 46.9%.

[0078] Example 6

[0079] <Preparation of catalysts CuZnZr>

[0080] Except for replacing cerium nitrate hexahydrate with zirconium nitrate pentahydrate and adding zinc nitrate hexahydrate, with a zirconium nitrate pentahydrate mass of 0.4405 g, copper nitrate trihydrate mass of 0.2479 g, zinc nitrate hexahydrate mass of 0.0305 g, and a Cu:Zn:Zr molar ratio of 10:1:10, everything else was the same as in Example 4. 0.2 g of the catalyst CuZnZr was obtained.

[0081] <Pre-reduction of catalyst>

[0082] Except for replacing Co / SiO2 with CuZnZr, everything else is the same as in Example 1.

[0083] <Degradation of Polyester Plastics>

[0084] Except for replacing Co / SiO2 with CuZnZr, the rest is the same as in Example 1, wherein the yield of PDO is 15.9%.

[0085] Example 7

[0086] <Preparation of the catalyst CuZnAl>

[0087] Weigh out 0.3411 g of copper nitrate trihydrate, 0.1400 g of zinc nitrate hexahydrate, and 0.5296 g of aluminum nitrate nonahydrate according to a Cu:Zn:Al molar ratio of 3:1:3, and prepare an aqueous solution with a total metal ion concentration of 1 mol / L. Under stirring at 65℃ and 300 rpm, add 3 mol / L Na₂CO₃ aqueous solution to adjust the pH of the solution to 8-9. After stirring the resulting suspension for 12 h, centrifuge, wash, and dry the solid at 110℃ for 12 h. Grind the obtained solid and calcine it in a muffle furnace at a rate of 2℃ / min to 400℃ for 2 h to obtain 0.2 g of the catalyst CuZnAl.

[0088] <Pre-reduction of catalyst>

[0089] Except for replacing Co / SiO2 with CuZnAl, everything else is the same as in Example 1.

[0090] <Degradation of Polyester Plastics>

[0091] Except for replacing Co / SiO2 with CuZnAl, the rest is the same as in Example 1, wherein the yield of PDO is 11.3%.

[0092] Example 8

[0093] <Preparation of the catalyst CuZnTi>

[0094] Except for replacing aluminum nitrate nonahydrate with titanium tetrachloride, using 0.3188 g of copper nitrate trihydrate, 0.0393 g of zinc nitrate hexahydrate, 0.2503 g of titanium tetrachloride, and maintaining a Cu:Zn:Ti molar ratio of 10:1:10, the process was identical to Example 7. 0.2 g of the catalyst CuZnTi was obtained.

[0095] <Pre-reduction of catalyst>

[0096] Except for replacing Co / SiO2 with CuZnTi, everything else is the same as in Example 1.

[0097] <Degradation of Polyester Plastics>

[0098] Except for replacing Co / SiO2 with CuZnTi, the rest is the same as in Example 1, wherein the yield of PDO is 23.4%.

[0099] Example 9

[0100] <Preparation of the catalyst CuZnSi>

[0101] According to a Cu:Zn molar ratio of 10:1, weigh 0.1917 g of copper nitrate trihydrate and 0.0236 g of zinc nitrate hexahydrate, and prepare a 0.2 mol / L ethanol + water aqueous solution with a volume ratio of 2:1, labeled as solution 1. Simultaneously, according to a Cu:Zn:Si molar ratio of 1:0.1:3, weigh 0.4963 g of tetraethyl orthosilicate, and prepare a 1.5 mol / L ethanol solution, labeled as solution 2. Mix solution 1 and solution 2, stir at 300 rpm for 30 min, and label as solution 3. Take 1.4 g of ammonium carbonate and prepare a 0.25 mol / L aqueous solution, labeled as solution 4. Take the same volume of water as solution 3, labeled as solution 5, and heat it to 85°C at 300 rpm, then reflux the cooled water. Add solution 3 to solution 5 at a rate of 50 mL / min, while simultaneously adding solution 4 dropwise to maintain the pH of solution 5 at 7-7.5. The resulting suspension was stirred for another 20 hours, then centrifuged, washed, and the solid was dried at 110°C for 12 hours. The resulting solid was then ground and calcined in a muffle furnace at a rate of 2°C / min to 400°C for 2 hours to obtain 0.2 g of the catalyst CuZnSi.

[0102] <Pre-reduction of catalyst>

[0103] Except for replacing Co / SiO2 with CuZnSi, everything else is the same as in Example 1.

[0104] <Degradation of Polyester Plastics>

[0105] Except for replacing Co / SiO2 with CuZnSi, the rest is the same as in Example 1, wherein the yield of PDO is 61.7%.

[0106] Example 10

[0107] Except for the change from 4h to 12h in the section on <Degradation of Polyester Plastics>, the process is the same as in Example 5, in which the yield of PDO is 93.2%.

[0108] Example 11

[0109] Except for adjusting 300°C to 400°C in the <Pre-reduction of the catalyst> and adjusting 180°C to 120°C in the <Degradation of polyester plastics>, the rest is the same as in Example 9, wherein the yield of PDO is 1.0%.

[0110] Example 12

[0111] Except for adjusting 120°C to 150°C in the section on <Degradation of Polyester Plastics>, the rest is the same as in Example 11, wherein the yield of PDO is 6.6%.

[0112] Example 13

[0113] Except for adjusting 120°C to 180°C in the section on <Degradation of Polyester Plastics>, the rest is the same as in Example 11, wherein the yield of PDO is 99.5%.

[0114] Example 14

[0115] Except for adjusting the temperature from 120°C to 240°C in the section on <Degradation of Polyester Plastics>, the rest of the results were the same as in Example 11, in which the yield of PDO was 99.7%.

[0116] Example 15

[0117] Except for adjusting the hydrogen pressure to 3 MPa in <Degradation of Polyester Plastics>, the rest is the same as in Example 13, in which the yield of PDO is 61.8%.

[0118] Example 16

[0119] Except for adjusting the hydrogen pressure to 2 MPa in the <Degradation of Polyester Plastics> section, the rest was the same as in Example 13, in which the PDO yield was 56.1%.

[0120] Example 17

[0121] Except for adjusting the temperature from 300°C to 500°C in the <Pre-reduction of the catalyst>, the rest is the same as in Example 9, wherein the yield of PDO is 66.4%.

[0122] Example 18

[0123] Except for adjusting the temperature from 300°C to 600°C in the <Pre-reduction of the catalyst>, the rest is the same as in Example 9, wherein the yield of PDO is 56.8%.

[0124] Example 19

[0125] Except for the adjustment of 5% H2 to hydrogen and 4h to 12h in the <Pre-reduction of the catalyst>, the rest is the same as in Example 9, wherein the yield of PDO is 95.0%.

[0126] Example 20

[0127] Except for the substitution of ethylene glycol for dioxane in the section on "Degradation of Polyester Plastics", the process is the same as in Example 13, wherein the yield of PDO is 2.1%.

[0128] Example 21

[0129] Except for the substitution of ethylene glycol for tetrahydrofuran in the section on "Degradation of Polyester Plastics", the process is the same as in Example 13, in which the yield of PDO is 16.3%.

[0130] Example 22

[0131] Except for the substitution of ethylene glycol for methanol in the section on "Degradation of Polyester Plastics", the process is the same as in Example 13, in which the yield of PDO is 99.6%.

[0132] Example 23

[0133] Except for the substitution of ethylene glycol for ethanol in the section on "Degradation of Polyester Plastics", the process is the same as in Example 13, in which the yield of PDO is 53.9%.

[0134] Example 24

[0135] Except for the substitution of ethylene glycol for PDO in the section on "Degradation of Polyester Plastics", the process is the same as in Example 13, in which the yield of PDO is 92.1%.

[0136] Example 25

[0137] Except for adjusting the mass of the catalyst to 0.5 g, the mass of the polyester plastic PLA to 5 g, the mass of PDO to 20 g, and the reaction time to 9500 min in the <Degradation of Polyester Plastics>, the rest is the same as in Example 24, wherein the yield of PDO is 97.1%.

[0138] Example 26

[0139] Except for adjusting the mass of the catalyst to 0.5g, the mass of the polyester plastic PLA to 5g, the solvent-free process, the reaction time to 120h, and the stirring method to magnetic stirring at 400rpm in the <Degradation of Polyester Plastics>, the rest is the same as in Example 9, wherein the yield of PDO is 93%.

[0140] Example 27

[0141] Except for the substitution of PLA for PGA in the section on "Degradation of Polyester Plastics", the rest of the description is the same as in Example 22, wherein the yield of ethylene glycol is 92.4%.

[0142] Example 28

[0143] Except for the substitution of methanol for ethylene glycol in the section on "Degradation of Polyester Plastics", the process is the same as in Example 27, in which the yield of ethylene glycol is 99.0%.

[0144] Example 29

[0145] Except for the following changes in <Degradation of Polyester Plastics>: 0.5g of PGA was changed to 0.3g of PGA, 180°C was changed to 220°C, 4h was changed to 24h, and no solvent was used, the rest of the process was the same as in Example 27, wherein the yield of ethylene glycol was 90.7%.

[0146] Example 30

[0147] Except for the change in <Degradation of Polyester Plastics> from 0.5 g PLA to 0.3 g PBS and 4 h to 8 h, the rest was the same as in Example 13, wherein the yield of 1,4-butanediol was 58.1%.

[0148] Example 31

[0149] Except for adjusting 180°C to 220°C in the section on <Degradation of Polyester Plastics>, the rest is the same as in Example 30, wherein the yield of 1,4-butanediol is 72.5%.

[0150] Example 32

[0151] Except for adjusting 180°C to 250°C and 8h to 24h in the section on <Degradation of Polyester Plastics>, the rest is the same as in Example 30, wherein the yield of 1,4-butanediol is 88.3%.

[0152] Example 33

[0153] Except for the substitution of PBS with PBA in the section on "Degradation of Polyester Plastics", the procedure was the same as in Example 30, in which the yield of 1,4-butanediol was 22.7%.

[0154] Example 34

[0155] Except for adjusting 180°C to 250°C in <Degradation of Polyester Plastics>, the rest is the same as in Example 33, wherein the yield of 1,4-butanediol is 52.5% and the yield of 1,6-hexanediol is 16.8%.

[0156] Example 35

[0157] Except for the change from 8h to 24h in the section on <Degradation of Polyester Plastics>, the rest is the same as in Example 33, wherein the yield of 1,4-butanediol is 78.3% and the yield of 1,6-hexanediol is 53.1%.

[0158] Comparative Example 1

[0159] 0.5g of PLA (polyester plastic) was biodegraded according to the national standard—Determination of final aerobic biodegradability of plastic materials under controlled composting conditions (GB / T19277–2003 / ISO 14855-1:2005). The degradation temperature was 58±2℃, the relative humidity was 50-55%, and the degradation time was 90 days. The biodegradation rate of PLA was approximately 80% (this data comes from the following literature: Y.Luo, Z.Lin, G.Guo, Nanoscale Research Letters 2019, 14, 56.).

[0160] The test results for Examples 1-9 are shown in Table 1, and the test results for Examples 10-16 are shown in Table 2 and... Figure 1 The test results for Examples 17-19 are shown in Table 3, the test results for Examples 20-24 are shown in Table 4, and the test results for Example 25 are shown in Table 5. Figure 3 As shown, the test results of Example 26 are as follows: Figure 4 The test results of Examples 27-29 are shown in Table 5, the test results of Examples 30-32 are shown in Table 6, and the test results of Examples 33-35 are shown in Table 7.

[0161] Table 1. Reactivity of hydrogenation of polyester plastics to prepare degradation products under different catalyst types.

[0162]

[0163] As shown in Table 1, Examples 1-9 demonstrate that by using the catalyst and degradation method provided in this application, polyester plastics can be degraded, achieving recycling and converting them into high-value degradation products. Specifically, PLA is converted into the high-value degradation product PDO. In particular, using ZrCu and CuZnSi as catalysts yields higher yields of degradation products.

[0164] Table 2. Reactivity of hydrogenation of polyester plastics to prepare degradation products under different reaction conditions.

[0165]

[0166] As shown in Table 2, Examples 5 and 10 demonstrate that variations in reaction time typically affect the yield of degradation products. By controlling the reaction time during the degradation of polyester plastics, a higher yield of degradation products can be achieved. Examples 11-14 show that the yield of degradation products varies with the reaction temperature during the degradation of polyester plastics. Controlling the reaction temperature within the range specified in this application enables the recycling of polyester plastics, transforming them into high-value degradation products. Examples 13 and 15-16 show that the yield of degradation products varies with the hydrogen pressure during the degradation of polyester plastics. Controlling the hydrogen pressure within the range specified in this application enables the recycling of polyester plastics, transforming them into high-value degradation products.

[0167] Figure 1 The diagram shows the reaction performance of PLA hydrogenation to PDO at different reaction times in Example 13. From... Figure 1 As can be seen from the process, during the degradation of the polyester plastic PLA in Example 13, the yield of the degradation product PDO increases with the extension of the reaction time. When the reaction time is 4 hours (240 minutes), the yield of PDO can reach 99.5%.

[0168] Table 3. Reactivity of hydrogenation of polyester plastics to prepare degradation products under different catalyst reduction conditions.

[0169]

[0170] As shown in Table 3, Examples 9, 13, and 17-19 demonstrate that the reduction temperature, reduction time, and type of reducing gas typically affect the reduction effect of the catalyst during reduction. Consequently, the reduced catalyst, when applied to the degradation reaction of polyester plastics, influences the yield of the degradation products. By controlling the reduction temperature, reduction time, and type of reducing gas within the range specified in this application, the resulting reduced catalyst, when applied to the degradation reaction of polyester plastics, enables the recycling of polyester plastics, converting them into high-value degradation products with a high yield.

[0171] Table 4. Reactivity of the preparation of degradation products from hydrogenated polyester plastics under different solvent conditions.

[0172]

[0173] As shown in Table 4, examples 13 and 20-24 demonstrate that the yield of degradation products varies with the solvent used in the degradation of polyester plastics. Using solvents within the scope of this application enables the recycling of polyester plastics, converting them into high-value degradation products. In particular, the yield of degradation products reaches over 90% when ethylene glycol, methanol, and 1,2-propanediol are used as solvents.

[0174] Figure 2 The hydrogenation reaction performance of polyester plastic PLA in solvent PDO at different reaction times is shown. Figure 2 As can be seen, using PDO as a solvent can avoid the separation problem after the hydrogenation of polyester plastic PLA to form the degradation product PDO. From... Figure 2 As can be seen, the yield of PDO increases with the extension of reaction time. When the reaction time is 6 h (360 min), the yield of PDO can reach more than 99%.

[0175] Figure 3 The hydrogenation reaction performance of a large quantity (5g) of polyester plastic PLA in solvent PDO at different reaction times in Example 25 is shown. Figure 3 As can be seen, when using 5g PLA as substrate, 20g PDO as solvent, and 0.5g CuZnSi as catalyst, the reaction can achieve the conversion of polyester plastic PLA at 180℃ for 9500min (approximately 158.3h) under a hydrogen atmosphere, with a yield of 97.1% for the degradation product PDO generated by the reaction.

[0176] Figure 4 The reaction properties of the polyester plastic PLA in Example 26 under solvent-free conditions are shown, such as... Figure 4 As shown, 0.5g of polyester plastic PLA and 0.5g of catalyst CuZnSi were first added to the reactor and reacted for 48h under a hydrogen atmosphere of 4MPa to obtain approximately 0.55g of degradation product PDO. Then, 1.5g of polyester plastic PLA was added to the reactor and reacted for 24h to obtain a cumulative total of approximately 1.85g of degradation product PDO. Next, 1.5g of polyester plastic PLA was added to the reactor and reacted for 24h to obtain a cumulative total of approximately 3.4g of degradation product PDO. Finally, 1.5g of polyester plastic PLA was added to the reactor and reacted for 24h to obtain a cumulative total of approximately 4.9g of degradation product PDO. In Example 26, the cumulative amount of polyester plastic PLA added throughout the entire reaction process was 5g, and the degradation reaction yielded approximately 4.9g of degradation product PDO, with a yield of 93%.

[0177] Table 5. Reactivity of PGA hydrogenation for preparing degradation products

[0178]

[0179] Note: In Table 5, “\” indicates solvent-free.

[0180] As shown in Table 5, Examples 27-29 demonstrate that the method of this application for degrading PGA (polyester plastic) enables the recycling of PGA, converting it into the high-value degradation product ethylene glycol, with a high yield. The yield of the degradation product varies with the type of solvent, reaction temperature, and reaction time during the degradation of PGA.

[0181] In Example 28, compared to Example 27, ethylene glycol was used as the solvent, avoiding the separation problem of ethylene glycol after PGA hydrogenation, thus achieving a higher ethylene glycol yield. In Example 29, compared to Examples 27-28, no solvent was used, but a high ethylene glycol yield was also achieved by controlling the reaction temperature and time.

[0182] Table 6. Reactivity of degradation products prepared by hydrogenation of polyester plastics PBS.

[0183]

[0184]

[0185] As shown in Table 6, Examples 30-32 demonstrate that the method of this application for degrading polyester plastic PBS enables the recycling of PBS, converting it into the high-value degradation product 1,4-butanediol, with a high yield. The yield of the degradation product varies with the reaction temperature and time during the degradation of polyester plastic PBS. By controlling the reaction temperature and time within the range specified in this application, the degradation of polyester plastics can consistently achieve recycling and conversion into high-value degradation products, such as converting PBS into 1,4-butanediol, with a high yield.

[0186] Table 7 Reactivity of PBA Hydrogenation for Degradation Products

[0187]

[0188] As shown in Table 7, examples 33-35 demonstrate that the method of this application for degrading polyester plastic PBA enables the recycling of PBA, converting it into high-value degradation products 1,4-butanediol and 1,6-hexanediol. During the degradation of PBA, the yield of the degradation products varies with the reaction temperature and time. By controlling the reaction temperature and time within the range specified in this application, the degradation of polyester plastics can consistently achieve recycling, converting them into high-value degradation products, specifically, converting PBA into 1,4-butanediol and 1,6-hexanediol.

[0189] In Comparative Example 1, the existing biodegradation method was used to degrade the polyester plastic PLA. When the biodegradation rate of PLA was about 80%, the degradation time was up to 90 days, which is longer than the degradation method of this application. Moreover, the degradation products were carbon dioxide and water, which could not achieve the recycling of polyester plastic and could not convert polyester plastic into the high-value degradation products of this application.

[0190] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0191] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for degrading polyester plastics, comprising the following steps: A catalyst and polyester plastic were added to a reaction vessel, and under a hydrogen atmosphere, the mixture was stirred to obtain degradation products. The mass ratio of the catalyst to the polyester plastic is (0.1-1):1, the pressure of the hydrogen gas is 1-5 MPa, the reaction temperature is 120-250℃, and the catalyst is selected from any one of Co / SiO2, ZrCu, CuZnZr, CuZnTi, and CuZnSi.

2. The method according to claim 1, wherein, A solvent is also added to the reaction vessel, wherein the mass ratio of the solvent to the polyester plastic is (3-100):1; The stirring method is mechanical stirring or magnetic stirring, with the mechanical stirring speed being 300-1000 rpm and the magnetic stirring speed being 300-800 rpm.

3. The method according to claim 2, wherein, The solvent is selected from at least one of dioxane, tetrahydrofuran, methanol, ethanol, ethylene glycol, 1,2-propanediol, 1,4-butanediol and 1,6-hexanediol.

4. The method according to claim 1, wherein, No solvent is added to the reaction vessel, and the stirring method is magnetic stirring with a speed of 300-800 rpm.

5. The method according to claim 1, wherein, Before use, the catalyst is pre-reduced in a reducing gas at 200-600°C for 4-12 hours. The reducing gas is selected from hydrogen or diluted hydrogen.

6. The method according to claim 5, wherein, The volume ratio of argon to hydrogen in the diluted hydrogen is (80-95):(5-20).

7. The method according to claim 1, wherein, The polyester plastic is selected from any one of polylactic acid, polyglycolic acid, polybutylene succinate, and polybutylene adipate.

8. The method according to claim 1, wherein, The degradation products are selected from any one of 1,2-propanediol, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

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