Method for converting polyethylene glycol terephthalate into glycollic acid, formic acid and H2 by using Rudelta+-Ru0 double-site catalyst

Abstract

The invention discloses a method for converting polyethylene glycol terephthalate into glycollic acid, formic acid and H2 by using a Ru delta < + >-Ru0 double-site catalyst. PET and a Ru delta < + >-Ru0 double-site catalyst are in contact with alkali liquor, PET is degraded through a hydrolysis reaction, and monomers TPA and EG are generated; and catalyzing the EG by the Ru delta < + >-Ru0 double-site catalyst to continue reforming reaction to generate products of glycollic acid, formic acid and H2. The Ru delta < + >-Ru0 double-site catalyst effectively adsorbs-CH2OH groups in PET hydrolysate ethylene glycol, and reduces the dissociation energy of C-H bonds, thereby promoting the generation of H2 fuel and glycollic acid. Meanwhile, the Ru delta < + >-Ru0 double sites further synergistically catalyze the breakage of a C-C bond, so that GA is converted into formic acid, the condition that GA is excessively oxidized into CO2 or CO is avoided, and efficient degradation and high-valued upgrading of PET are realized. A feasible scheme is provided for green degradation and resource utilization of the polyester plastic.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial catalysis, specifically to the preparation of a dual-site catalyst and a method for depolymerizing polyethylene terephthalate into high-value chemicals under mild conditions. In particular, it relates to a method for converting polyethylene terephthalate into glycolic acid, formic acid and H2 by a dual-site catalyst. Background Art

[0002] Plastics play an indispensable role in modern society, but the continuous accumulation of post-consumer waste plastics is threatening human health and the ecosystem. Polyethylene terephthalate (PET) is the most widely used polyester, which is polymerized from terephthalic acid (TPA) and ethylene glycol (EG), accounting for 12% of global solid waste. Mechanical treatment is a simple method for recycling PET plastic waste, but it often leads to a decrease in its mechanical properties. Chemical recycling can depolymerize waste PET into monomers TPA and EG without affecting its functionality. However, it should be noted that although TPA can be easily obtained in an aqueous solution by adjusting the pH value, EG is difficult to separate from the aqueous phase due to its high water solubility and relatively high boiling point (197 °C), which requires high-temperature energy consumption to complete the subsequent distillation operation. In addition, considering the low price of EG (about $1.1 per kilogram), its renewability, and its relatively high hydrogen content (6.5 wt%), upgrading it to high-value chemicals and hydrogen is extremely attractive. Therefore, integrating the chemical depolymerization of PET with the reforming reaction of EG under mild conditions would be a very promising technical route.

[0003] In recent years, a variety of innovative technical routes have been developed to combine PET conversion with EG upgrading. For example, emerging photocatalytic / electrocatalytic technologies can convert EG into high-value chemicals under mild conditions. These processes generally include three independent unit operations: in a strong base environment The process of high-temperature reforming of PET or EG is still limited by the following defects: 1) Harsh reaction conditions, such as high temperature (>250°C) and high pressure. Due to the chemical inertness of PET plastic and the slow solid-solid reaction kinetics between plastic and catalyst, high temperature and high pressure are required in the depolymerization process, which inevitably leads to high cost investment. 2) Low product selectivity and excessive carbon emissions. Harsh reaction conditions (especially high temperature) can easily lead to non-selective adsorption, decomposition or over-oxidation of PET, EG and their intermediates, resulting in complex product distribution, including alkanes, alkenes, organic acids, and excessive carbon emissions such as CO2 and CO. Therefore, it is a very challenging task to develop an efficient, energy-saving and green catalytic system to achieve the tandem catalysis of PET chemical depolymerization and in situ reforming of EG into high-value target products. Summary of the invention

[0004] Aiming at the problem that the recycling conditions of polyester polymer PET are harsh and EG is difficult to separate, the present invention prepares Dual-site catalyst for efficient PET recovery and upgrading.

[0005] The purpose of this application is to develop an efficient, green and energy-saving catalytic system to achieve the combined reaction of PET depolymerization and EG reforming under mild conditions, and to generate formic acid (FA), glycolic acid (GA) and H2 with high selectivity. This system can not only achieve efficient conversion of PET and EG, but also achieve industrial-grade H2 production (2.01m 3 kg PET -1 d -1 g Cat -1 ).

[0006] The technical solution of the present invention is as follows:

[0007] A method for converting polyethylene terephthalate into glycolic acid, formic acid and H2 using a dual-site catalyst; the method comprising: The dual-site catalyst comes into contact with the alkaline solution and degrades PET through a hydrolysis reaction to generate monomers TPA and EG; The dual-site catalyst catalyzes the reforming reaction of EG to produce glycolic acid (GA), formic acid (FA) and H2.

[0008] The The tandem hydrolysis and reforming reaction of the dual-site catalyst and the polyester polymer PET at a temperature of 30°C to 160°C, with the pH value adjusted to 13 to 14 by an alkaline solution and a reaction time of 0.5 days to 4 days, yields monomers TPA, formic acid, glycolic acid, and H2.

[0009] The dual-site catalyst includes Ru / CeO2, Ru / TiO2, Ru / ZnO, Ru / C, Ru / ZrO2, or Ru / CNTs.

[0010] The weight of the Ru metal atoms supported in the dual-site catalyst is 0.5% to 8%.

[0011] The weight ratio of the dual-site catalyst to PET is 1:1 to 1:10.

[0012] The preparation method of the dual-site catalyst includes the following steps:

[0013] The impregnation step, where the metal precursor salts corresponding to the dual-site catalyst and the support are each independently dissolved in a solvent to form an aqueous RuCl3 solution and a support solution;

[0014] The loading step, where the aqueous RuCl3 solution and the support solution are mixed to load the metal precursor salts onto the support, obtaining a support loaded with metal precursor salts;

[0015] The reduction step, where the support loaded with metal precursor salts is subjected to a reduction treatment to obtain the dual-site catalyst solution;

[0016] The drying step, where the obtained dual-site catalyst solution is centrifuged and dried to obtain the dual-site catalyst.

[0017] In the impregnation step, the solvent is selected from at least one of deionized aqueous solution, methanol aqueous solution, and ethanol aqueous solution.

[0018] In the methanol aqueous solution, the volume ratio of methanol to water is 1:(1 to 4), and in the ethanol aqueous solution, the volume ratio of ethanol to water is 1:(1 to 4).

[0019] In the drying step: at a temperature of 40°C to 100°C, the support loaded with metal precursor salts is subjected to vacuum drying for 8h to 16h.

[0020] In the preferred drying step, the carrier loaded with the metal precursor salt is subjected to vacuum drying at a temperature of 60 °C to 80 °C for 10 h to 14 h.

[0021] The specific description is as follows:

[0022] To achieve the above object, a first aspect of the present application provides a method for one-pot tandem PET depolymerization and EG reforming reaction, including:

[0023] PET and The dual-site catalyst is contacted with an alkali solution, and PET is degraded by hydrolysis reaction to generate monomer TPA and EG. Subsequently The dual-site catalyst catalyzes EG to continue the reforming reaction to generate products glycolic acid (GA), formic acid (FA) and H2. Among them, after extending the reaction time, GA can be completely converted to FA.

[0024] Among them, the dual-site catalyst includes Ru / CeO2, Ru / TiO2, Ru / ZnO, Ru / C, Ru / ZrO2, Ru / CNTs catalysts.

[0025] According to any one of the embodiments of the first aspect of the present application, the method further includes:

[0026] Providing the dual-site catalyst and the polyester PET;

[0027] At a temperature of 30 °C to 160 °C, preferably 60 °C to 120 °C, the combination of the dual-site catalyst and the polyester PET is contacted with an alkali solution having a pH value of 13 to 14, preferably 13.3 to 13.6, and subjected to a tandem hydrolysis and reforming reaction for 0.5 days to 4 days, preferably 1 day to 4 days, to obtain monomer TPA, FA, GA and H2. PET is first hydrolyzed into EG and TPA by the action of an alkali solution, and EG is adsorbed on the dual-site catalyst, and then further converted into intermediate GA under the action of the catalyst. GA can also continue to react to be converted into FA and trace AA, and at the same time H2 is generated during the conversion of EG (as Figure 1 ).

[0028] According to any one of the embodiments of the first aspect of the present application, providing the dual-site catalyst includes:

[0029] The impregnation step includes dissolving the metal precursor salt corresponding to the dual-site catalyst and the carrier independently in a solvent, an aqueous RuCl3 solution and a carrier solution;

[0030] The loading step includes mixing the RuCl3 aqueous solution carrier solution to load the metal precursor salt onto the carrier, obtaining a carrier loaded with the metal precursor salt;

[0031] The reduction step includes subjecting the carrier loaded with the metal precursor salt to a reduction treatment to obtain the dual-site catalyst solution;

[0032] The drying step includes centrifuging and drying the obtained dual-site catalyst solution to obtain the dual-site catalyst. It can be seen from the transmission electron microscopy (TEM) image that the circled part in the circle is the Ru metal cluster, and it can be seen that the Ru metal clusters are evenly dispersed on the metal oxide carrier ( Figure 2 ).

[0033] According to any of the embodiments of the second aspect of the present application, in the impregnation step, the solvent is selected from at least one of deionized aqueous solution, methanol aqueous solution and ethanol aqueous solution.

[0034] Preferably, the volume ratio of methanol to water in the methanol aqueous solution is 1:(1-4), and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:(1-4).

[0035] According to any of the embodiments of the first aspect of the present application, the drying step further includes:

[0036] Vacuum drying the carrier loaded with the metal precursor salt at a temperature of 40°C to 100°C, preferably 60°C to 80°C, for 8h to 16h, preferably 10h to 14h.

[0037] The second aspect of the present application provides a dual-site catalyst that can realize tandem PET depolymerization reaction and EG reforming reaction, including Ru metal clusters loaded on various alkali-resistant inert carriers: Ru / CeO2, Ru / TiO2, Ru / ZnO, Ru / C, Ru / ZrO2, Ru / CNTs.

[0038] According to any of the embodiments of the second aspect of the present application, the weight ratio of the dual-site catalyst to PET is 1:1 to 1:10, preferably 1:1 to 1:2.

[0039] According to any of the embodiments of the first aspect of the present application, in the inert carrier corresponding to the dual-site catalyst, the carrier includes at least one of CeO2, TiO2, ZnO, ZrO2, C, CNTs.

[0040] Compared with the prior art, the present application has at least the following beneficial effects:

[0041] 1. Low cost and simple preparation: The dual-site catalyst prepared by the present invention has the characteristics of simple preparation process, short time consumption, low energy consumption, etc. The dual-site catalyst has the characteristics of simple preparation process, short time consumption, and low energy consumption.

[0042] 2. Efficient and green conversion: Under mild conditions (90 °C, atmospheric pressure), the present invention realizes the tandem PET depolymerization and EG in-situ reforming reaction in one pot. Among them, the conversion rate of PET is 100%, the conversion rate of EG is 100%, and the yield of monomer TPA is 100%. The operation is simple, there are no additional complex separation steps, and the whole process is green and environmentally friendly without CO2 and CO emissions.

[0043] 3. High-selectivity product generation: The present invention overcomes the technical problem of difficult separation of EG in aqueous solution, and efficiently converts EG into high-value GA / FA products and high-purity H2 fuel. Among them, the yields of GA and FA are as high as over 90%, and the H2 production is 17.8 mol / kg PET , realizing the efficient recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic diagram of the tandem PET depolymerization and EG reforming reaction in one pot provided in Example 1 of the present application.

[0045] Figure 2 is provided in Example 1 of the present application Transmission electron microscope (TEM) image of the dual-site catalyst.

[0046] Figure 3 is a graph showing the change of H2 production over time provided in Example 1 of the present application.

[0047] Figure 4 is the conversion rate and product selectivity graph of the dual-site catalyst with loadings of 1 wt%, 2.5 wt%, and 5 wt% for catalyzing PET provided in Examples 1-3 of the present application of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] In order to make the application purpose, technical solution and beneficial technical effects of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application and not for limiting the present application. The drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0049] For simplicity, only some numerical ranges are explicitly disclosed in this text. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, each point or single value between the range endpoints is included within the range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recited.

[0050] In the description of this application, it should be noted that unless otherwise specified, "above" and "below" include the recited number, and the meaning of "multiple" in "one or more" is two or more.

[0051] The above application content of this application does not intend to describe every disclosed embodiment or every implementation manner in this application. The following description more specifically illustrates exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. In each instance, the listing is only a representative group and should not be construed as exhaustive.

[0052] A first aspect of an embodiment of this application provides a method for one-pot tandem PET depolymerization and EG reforming, including:

[0053] contacting a combination of polyester PET and a dual-site catalyst with an alkali solution to degrade and upgrade the polyester PET through a one-pot tandem PET depolymerization and EG reforming reaction.

[0054] In the method for one-pot tandem PET depolymerization and EG reforming provided by this application, by contacting a combination of polyester PET and a dual-site catalyst with an alkali solution, in the alkali solution, the polyester PET undergoes a hydrolysis reaction, thereby degrading it into monomer TPA and EG. Among them, EG further reacts in the aqueous solution. EG first adsorbs on the site of the dual-site catalyst, and the -CH2OH functional group dehydrogenates to produce H2. The hydrogen production at 4 h, 8 h, 16 h, and 24 h was collected and measured, and it was found that the H2 production rate gradually increased with the increase of time. At 24 h, the H2 production rate reached a maximum of 17.8 mol / kg ( PET ( Figure 3 ). In addition, after dehydrogenation, EG generates intermediate GA. GA breaks its C-C bond to generate FA under the synergistic effect of the dual-site catalyst, and after extending the reaction time, such as Figure 4It is the NMR spectrum of the solution after the reaction with GA as the substrate. The NMR peaks of GA disappear, and only the product peaks of FA are present, indicating that GA is completely converted to FA.

[0055] In some embodiments, the method further includes:

[0056] providing the dual-site catalyst and the polyester PET;

[0057] at a temperature of 30°C to 160°C, preferably 60°C to 120°C, contacting the combination of the dual-site catalyst and the polyester PET with an alkaline solution having a pH value of 13 to 14, preferably 13.3 to 13.6, and performing a tandem PET hydrolysis and EG reforming reaction for 0.5 days to 4 days, preferably 1 day to 4 days, to obtain monomers TPA, formic acid, glycolic acid, and H2.

[0058] In some embodiments, the temperature of the above reaction is 30°C to 160°C. For example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C,... 160°C or any value within the range composed of the above values. Preferably, the temperature of the reaction is 60°C to 120°C.

[0059] In some embodiments, the alkaline solution includes, but is not limited to, a 0.1 mol / L to 5.0 mol / L KOH solution, a 0.1 mol / L to 5.0 mol / L NaOH solution, a 0.1 mol / L to 5.0 mol / L Ca(OH)2 solution, etc.

[0060] In the embodiments of the present application, by controlling the pH value of the alkaline solution within a suitable range, it is beneficial to catalyze the occurrence of the PET hydrolysis and EG reforming reactions, and is beneficial to the depolymerization and upgrading of the polyester PET.

[0061] In some embodiments, the time for the above tandem PET hydrolysis and EG reforming reaction is 0.5 days to 4 days, and this time can be adjusted according to the ratio of the dual-site catalyst to the polyester PET. For example, it can be 0.5 days, 1 day, 2 days, 3 days, 4 days or any value within the range composed of the above values. Preferably, the time for the above tandem hydrolysis and reforming reaction is 1 day to 4 days.

[0062] In some embodiments, providing the dual-site catalyst includes:

[0063] an impregnation step, including the same as the The metal precursor salt and the support corresponding to the dual-site catalyst are each independently dissolved in a solvent to obtain a first solution and a second solution respectively;

[0064] The loading step includes mixing the first solution and the second solution so that the metal precursor salt is loaded onto the support to obtain a support loaded with the metal precursor salt;

[0065] The reduction step includes subjecting the support loaded with the metal precursor salt to a reduction treatment to obtain the dual-site catalyst solution;

[0066] The drying step includes subjecting the obtained dual-site catalyst solution to centrifugation and drying treatments to obtain the dual-site catalyst.

[0067] In some embodiments, in the above steps, the solvent can be selected from at least one of deionized aqueous solution, methanol aqueous solution and ethanol aqueous solution. Preferably, the volume ratio of methanol to water in the methanol aqueous solution is 1:(4 - 1), and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:(4 - 1).

[0068] In the embodiments of the present application, the solvent can play a good role in dissolving and dispersing the metal precursor salt corresponding to the above dual-site catalyst, which is beneficial to better loading of the precursor salt onto the support.

[0069] In some embodiments, in the above steps, after mixing the first solution and the second solution, it further includes stirring and filtering the obtained mixed solution to obtain a support loaded with the metal precursor salt.

[0070] In some embodiments, the above drying step further includes:

[0071] Vacuum drying the support loaded with the metal precursor salt at a temperature of 40°C - 100°C, preferably 60°C - 80°C, for 8h - 16h, preferably 10h - 14h.

[0072] In some embodiments, the temperature of the vacuum drying treatment is 40°C - 100°C, for example, it can be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or any range composed of the above values. Preferably, the temperature of the vacuum drying treatment is 60°C - 80°C.

[0073] In some embodiments, in the above steps, the vacuum drying time is 8 h to 16 h. For example, it can be 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h or any value within the range composed of the above values. Preferably, the time for the vacuum drying treatment is 10 h to 14 h.

[0074] The second aspect of the embodiments of the present application provides a polyester plastic PET and its degradation and upgrading method, including:

[0075] Polyester PET and a dual-site catalyst, wherein the dual-site catalyst includes Ru / CeO2, Ru / TiO2, Ru / ZnO, Ru / C, Ru / ZrO2, Ru / CNTs catalysts.

[0076] In some embodiments, the weight ratio of the dual-site catalyst to polyester PET is 1:1 to 1:10. For example, the weight ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any value within the range composed of the above values. Preferably, the weight ratio is 1:1 to 1:4; more preferably, the weight ratio is 1:1 to 1:2.

[0077] In the embodiments of the present application, by controlling the weight ratio of the dual-site catalyst to polyester PET within a suitable range, it is beneficial to enable PET to have a good degradation effect. When the weight ratio is higher than 1:4, PET cannot be fully degraded; while when the weight ratio is lower than 1:1, it will cause an excess of the dual-site catalyst.

[0078] In some embodiments, the metal precursor salt corresponding to the dual-site catalyst can be selected from one or several of the metal precursor salts corresponding to the dual-site catalyst. Preferably, it can be selected from one or two of the metal precursor salts corresponding to the dual-site catalyst. For example, it can be ruthenium nitrate, ruthenium sulfate, ruthenium chloride, ruthenium acetate or a mixture of any two of the above compounds, etc.

[0079] In some embodiments, based on the total weight of the dual-site catalyst, the The weight of the supported Ru metal in the dual-site catalyst is 0.5% to 8%. For example, the weight of the Ru metal can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or any value within the range above. Preferably, the weight of the Ru metal is 1% to 5%.

[0080] In some embodiments, The supports corresponding to the dual-site catalysts include, but are not limited to, carbon supports, metal oxides, etc. For example, they can be CeO2, TiO2, ZnO, ZrO2, C, CNTs, etc.

[0081] Examples

[0082] The following examples more specifically describe the content disclosed in the present application. These examples are only for illustrative purposes, because various modifications and variations within the scope of the present application disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0083] Example 1

[0084] 0.25 g of PET and 0.2 g of the dual-site catalyst were combined and placed in 10 mL of 2 mol / L NaOH solution, and then put into a high-temperature and high-pressure reactor. Under the conditions of a temperature of 90 °C and a stirring rate of 1000 r / min, a one-day tandem hydrolysis and reforming reaction was carried out.

[0085] Examples 2 - 14

[0086] Examples 2 - 14 The method of using the dual-site catalyst to catalyze PET and the degradation method were similar to those in Example 1, but the composition of the catalyst and PET and the product parameters, as well as the relevant reaction parameters in the degradation method, were adjusted. The specific product and method parameters are shown in Table 1.

[0087] In addition, the conversion rates of the tandem hydrolysis and reforming reactions of PET catalyzed by the dual-site catalysts in Examples 1 - 14 were tested, and the test results are also shown in Table 1.

[0088] Table 1: Parameters and test results of Examples 1 - 15

[0089]

[0090]

[0091] Test section

[0092] In Table 1, the conversion rate = the amount of PET reacted / the total input amount of PET. Among them, the amount of PET reacted is obtained by conversion based on the amount of TPA monomers obtained from the reaction, and the amount of TPA monomers obtained from the reaction is measured by nuclear magnetic resonance hydrogen spectrum.

[0093] Comparative analysis of Examples 1 to 4 shows that The presence of double sites can promote tandem PET hydrolysis and EG reforming reactions.

[0094] Comparative analysis of Example 1 and Examples 7 to 11 shows that The number of double sites is related to the interaction between the metal support. The metal support effects in the examples are all beneficial to the conversion of PET. At the same time, #imgpt66# the number of double sites will affect the selectivity of the products GA and FA.

[0095] Comparative analysis of Examples 12 to 14 and 4 to 6 shows that all the temperature gradients and alkali concentration gradients in the examples are beneficial to PET conversion.

[0096] Comparative analysis of Examples 14 to 19 shows that the reaction times in the examples are all beneficial to the conversion rate of PET. When the reaction times are different and the alkali concentrations of the solutions are different, the selectivities of the products GA and FA will show differences.

[0097] As described above, the above are only the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. Ru δ+ -Ru 0 Method for converting polyethylene terephthalate into glycolic acid, formic acid and H2 by a two-site catalyst; characterized in that, PET and Ru δ+ -Ru 0 The two-site catalyst contacts with the lye and degrades PET through hydrolysis reaction to generate monomers TPA and EG; subsequently, Ru δ+ -Ru 0 The two-site catalyst catalyzes the reforming reaction of EG to generate products glycolic acid (GA), formic acid (FA) and H2.

2. The method according to claim 1, characterized in that Ru δ+ -Ru 0 The tandem hydrolysis and reforming reaction of the two-site catalyst and the polyester polymer PET at a temperature of 30 °C to 160 °C, with the pH value adjusted to 13 to 14 by an alkaline solution and a reaction time of 0.5 days to 4 days, yields the monomers TPA, formic acid, glycolic acid, and H2.

3. The method according to claim 1, characterized in that The Ru δ+ -Ru 0 The dual-site catalysts include Ru / CeO2, Ru / TiO2, Ru / ZnO, Ru / C, Ru / ZrO2 or Ru / CNTs.

4. The method according to claim 3, wherein Ru δ+ -Ru 0 The weight of the supported Ru metal atoms in the two-site catalyst is 0.5% to 8%.

5. The method according to claim 1, wherein Ru δ+ -Ru 0 The weight ratio of the double-site catalyst to PET is 1:1 to 1:

10.

6. The method according to claim 1, wherein The Ru δ+ -Ru 0 The preparation method of the dual-site catalyst comprises the following steps: Impregnation step, Ru δ+ -Ru 0 The metal precursor salts and supports corresponding to the dual-site catalyst are independently dissolved in a solvent to form an aqueous RuCl3 solution and a support solution; Loading step: Mix the RuCl3 aqueous solution and the carrier solution so that the metal precursor salt is loaded onto the carrier, obtaining a carrier loaded with the metal precursor salt. Reduction step: subject the carrier loaded with the metal precursor salt to reduction treatment to obtain the Ru δ+ -Ru 0 Double-site catalyst solution Drying step, the obtained Ru δ+ -Ru 0 The two-site catalyst solution is centrifuged and dried to obtain the Ru δ+ -Ru 0 two-site catalyst.

7. The method according to claim 6, characterized in that, In the impregnation step, the solvent is selected from at least one of deionized aqueous solution, methanol aqueous solution, and ethanol aqueous solution.

8. The method according to claim 7, wherein In the methanol aqueous solution, the volume ratio of methanol to water is 1:(1 - 4), and in the ethanol aqueous solution, the volume ratio of ethanol to water is 1:(1 - 4).

9. The method according to claim 6, wherein In the drying step: At a temperature of 40°C to 100°C, perform vacuum drying treatment on the carrier loaded with the metal precursor salt for 8h to 16h.

10. The method according to claim 6, wherein In the drying step: At a temperature of 60°C to 80°C, perform vacuum drying treatment on the carrier loaded with the metal precursor salt for 10h to 14h.

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