Process for the catalytic alcoholysis of pet

Abstract

The application provides a method for catalytic alcoholysis of PET, which comprises blending PET with an alcoholysis agent, a co-solvent and an alcoholysis catalyst for catalytic alcoholysis; the co-solvent comprises a nitrile compound; the alcoholysis agent comprises an alcohol compound; and the alcoholysis catalyst comprises a metal porphyrin complex, and the structural formula of the metal porphyrin complex is as follows: wherein R 1 Each is independently one of -H, -C6H5, -C6H4-C(CH3)3 or -C6F5; R 2 Each is independently -H or -CH2CH3; and M is Zn. The method can efficiently alcoholize PET under mild conditions, and improves the PET conversion rate and DMT yield.

Description

Technical Field

[0001] This application relates to the field of polyester degradation technology, and in particular to a method for catalytic alcoholysis of PET. Background Technology

[0002] PET (polyethylene terephthalate) is a thermoplastic polyester copolymerized from terephthalic acid (PTA) and ethylene glycol (EG). Waste PET cannot be completely biodegraded naturally, and its slow decomposition process produces harmful microplastics and chemicals, posing a threat to plants, animals, and the surrounding environment. Currently, the main methods for PET disposal are incineration and landfill. In recent years, with the booming development of the plastics industry and continuous technological advancements, chemical recycling methods for PET have gradually developed into pyrolysis, hydrolysis, alcoholysis, and ammonolysis, among which alcoholysis is the most widely used. However, current alcoholysis reactions suffer from low PET conversion rates and demanding reaction conditions (mostly carried out under high temperature and high pressure). Summary of the Invention

[0003] Therefore, it is necessary to provide a method for catalytic alcoholysis of PET that improves PET conversion under mild reaction conditions.

[0004] This application provides a method for catalytic alcoholysis of PET, comprising the following steps:

[0005] PET was catalytically alcoholized by blending it with an alcoholysis agent, a co-solvent, and an alcoholysis catalyst.

[0006] The co-solvent includes nitrile compounds; the alcoholysis agent includes alcohol compounds; and the alcoholysis catalyst includes a metalloporphyrin complex, the structural formula of which is as follows:

[0007] , where R 1 Each is independently one of -H, -C6H5, -C6H4-C(CH3)3, or -C6F5; R 2 Each is independently -H or -CH2CH3; M is Zn.

[0008] The above method uses a metalloporphyrin complex as a catalyst and a nitrile compound as a co-solvent to catalytically alcoholyze PET. This method eliminates the need for high temperature and pressure, enabling efficient alcoholysis of PET under mild conditions, thus improving PET conversion and dimethyl terephthalate (DMT) yield. The nitrile compound not only activates the alcoholysis agent and promotes PET swelling, but also increases the contact area between the ester bonds of PET and the alcoholysis agent and metalloporphyrin complex, thereby enhancing the alcoholysis reaction rate and PET conversion. The metal ions in the metalloporphyrin complex can coordinate with oxygen atoms in methanol, ethanol, and ethylene glycol, enhancing the nucleophilicity of the alcohol molecules and thus more effectively attacking the carbonyl carbon atoms on the PET chain, destroying the PET chain without high temperature. The nitrile compound, alcohol, and metalloporphyrin complex interact synergistically, improving PET conversion and DMT yield under mild alcoholysis conditions.

[0009] The alcoholysis catalyst described above has high catalytic efficiency, which greatly reduces the temperature and catalyst dosage of PET alcoholysis. The alcoholysis catalyst also has good stability and still maintains high PET conversion and DMT yield after multiple cycles.

[0010] Traditional PET alcoholysis requires a temperature of 180℃ to 220℃, while the above method can still achieve high PET conversion and DMT yield even at a temperature as low as 40℃.

[0011] The aforementioned alcoholysis catalyst reduces colored impurities in the degradation products, facilitating efficient separation and purification of the products; the ester products generated by alcoholysis can then be used as raw materials for the construction of polyester compounds.

[0012] The aforementioned alcoholysis catalyst reduces the energy consumption and cost of PET alcoholysis.

[0013] In some embodiments, the nitrile compound includes at least one of acetonitrile, trimethylacetonitrile, and benzonitrile.

[0014] In some embodiments, the nitrile compound includes at least one of trimethylacetonitrile and acetonitrile; and / or,

[0015] The alcohol compounds include at least one of methanol, ethanol, and ethylene glycol.

[0016] In some embodiments, the metalloporphyrin complex comprises one or more of the following compounds:

[0017] .

[0018] In some embodiments, the molar ratio of the alcoholysis agent to the PET is (15~55):1; and / or,

[0019] The molar ratio of the co-solvent to the alcoholysis agent is (0.25~1.25):1; and / or,

[0020] The mass ratio of the alcoholysis catalyst to the PET is (0.05~0.5):100.

[0021] In some embodiments, the molar ratio of the alcoholysis agent to the PET is (25~45):1; and / or,

[0022] The molar ratio of the co-solvent to the alcoholysis agent is (0.75~1.25):1; and / or,

[0023] The mass ratio of the alcoholysis catalyst to the PET is (0.05~0.2):100.

[0024] In some embodiments, the co-solvent is trimethylacetonitrile, and the alcoholysis agent is methanol.

[0025] In some embodiments, the molar ratio of trimethylacetonitrile to methanol is (0.75~1.0):1.

[0026] In some embodiments, the catalytic alcoholysis satisfies at least one of the following conditions:

[0027] (1) The temperature of the catalytic alcoholysis is 40℃~140℃; optionally, the temperature of the catalytic alcoholysis is 60℃~100℃;

[0028] (2) The catalytic alcoholysis time is 1h to 12h; optionally, the catalytic alcoholysis time is 1h to 2h.

[0029] (3) The pressure of the catalytic alcoholysis is 0.1 MPa ~ 2.0 MPa;

[0030] (4) The atmosphere for the catalytic alcoholysis is nitrogen.

[0031] In some embodiments, the PET satisfies at least one of the following conditions:

[0032] (1) The molecular weight of the PET is 20,000 to 35,000;

[0033] (2) The degree of polymerization of the PET is 100~180. Attached Figure Description

[0034] Figure 1 This is the gas chromatogram of the DMT standard sample from Example 1.

[0035] Figure 2 This is a gas chromatogram of the PET alcoholysis products from Example 1. Detailed Implementation

[0036] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] Polyethylene terephthalate (PET) is a thermoplastic polyester copolymerized from terephthalic acid (PTA) and ethylene glycol (EG). It boasts high strength and safety, and is widely used in textiles, beverage containers, and food packaging. The raw materials for PET production are fossil resources, with limited and non-renewable reserves. Furthermore, PET is essentially non-biodegradable, producing harmful microplastics and chemicals during its slow decomposition, posing a threat to plants, animals, and the surrounding environment. Chemical recycling methods for PET include pyrolysis, hydrolysis, alcoholysis, and ammonolysis, with alcoholysis being the most widely used. However, alcoholysis of PET suffers from low conversion rates and demanding reaction conditions, typically requiring temperatures of 180℃ to 220℃ and pressures of 2MPa to 4MPa.

[0039] Currently, those skilled in the art are dedicated to developing alcoholysis catalysts to promote efficient alcoholysis. For example, some researchers have attempted to prepare defective zinc oxide nanosheets as catalysts for the alcoholysis of waste PET. However, the preparation process of these catalysts is complex, energy-intensive, and involves high metal content, which can lead to metal spillage affecting the purity of the alcoholysis products and hindering product yield improvement. Other methods involve mixing PET fragments with zinc compounds such as zinc oxide and zinc hydroxide, and then catalytically degrading them with steam at 180°C–320°C and atmospheric pressure to produce a solid mixture of terephthalic acid and catalyst, as well as liquid ethylene glycol. However, this method also suffers from complex processes and high energy consumption. Therefore, improving the PET conversion rate during PET alcoholysis under mild reaction conditions is a pressing technical challenge.

[0040] Based on this, this embodiment provides a method for catalytic alcoholysis of PET, comprising the following steps:

[0041] PET was catalytically alcoholized by blending it with an alcoholysis agent, a co-solvent, and an alcoholysis catalyst.

[0042] The co-solvent includes nitrile compounds; the alcoholysis agent includes alcohol compounds; and the alcoholysis catalyst includes a metalloporphyrin complex, the structural formula of which is as follows:

[0043] , where R 1 Each is independently one of -H, -C6H5, -C6H4-C(CH3)3, or -C6F5; R 2 Each is independently -H or -CH2CH3; M is Zn.

[0044] The above method uses a metalloporphyrin complex as a catalyst and a nitrile compound as a co-solvent to catalytically alcoholyze PET. This method eliminates the need for high temperature and pressure, enabling efficient alcoholysis of PET under mild conditions, thus improving PET conversion and dimethyl terephthalate (DMT) yield. The nitrile compound not only activates the alcoholysis agent and promotes PET swelling, but also increases the contact area between the ester bonds of PET and the alcoholysis agent and metalloporphyrin complex, thereby enhancing the alcoholysis reaction rate and PET conversion. The metal ions in the metalloporphyrin complex can coordinate with oxygen atoms in methanol, ethanol, and ethylene glycol, enhancing the nucleophilicity of the alcohol molecules and thus more effectively attacking the carbonyl carbon atoms on the PET chain, destroying the PET chain without high temperature. The nitrile compound, alcohol, and metalloporphyrin complex interact synergistically, improving PET conversion and DMT yield under mild alcoholysis conditions.

[0045] The alcoholysis catalyst described above has high catalytic efficiency, which greatly reduces the temperature and catalyst dosage of PET alcoholysis. The alcoholysis catalyst also has good stability and still maintains high PET conversion and DMT yield after multiple cycles.

[0046] Traditional PET alcoholysis requires a temperature of 180℃ to 220℃, while the above method can still achieve a PET conversion rate and DMT yield of over 97% even at a temperature as low as 40℃.

[0047] The aforementioned alcoholysis catalyst reduces colored impurities in the degradation products, facilitating efficient separation and purification of the products; the ester products generated by alcoholysis can then be used as raw materials for the construction of polyester compounds.

[0048] The aforementioned alcoholysis catalyst reduces the energy consumption and cost of PET alcoholysis.

[0049] In some of these implementations, for R 1 =H,R 2 =H and R1 =H,R 2 =CH2CH3 metalloporphyrin complexes are commercially available reagents and can be purchased directly.

[0050] In some embodiments, the metalloporphyrin complex includes one or more of the following compounds: .

[0051] Furthermore, the above-mentioned metalloporphyrin complexes can be prepared by the following method:

[0052] S1: Pyrrole is catalytically condensed with aryl formaldehyde compounds to obtain porphyrin compounds;

[0053] S2: Metallization reaction of porphyrin compounds with metal salts to prepare metalloporphyrin complexes.

[0054] In some embodiments, the metalloporphyrin complex is:

[0055] .

[0056] This zinc porphyrin complex does not require high temperature and high pressure, and can efficiently alcoholyze PET under mild conditions, improving PET conversion and dimethyl terephthalate (DMT) yield. The alcoholysis catalyst has high catalytic efficiency, which greatly reduces the temperature and catalyst dosage of PET alcoholysis. The alcoholysis catalyst has good stability and still has high PET conversion and DMT yield after multiple cycles.

[0057] Furthermore, the preparation method of the above zinc porphyrin complex is as follows:

[0058] S1: Pyrrole is reacted with 4-tert-butylbenzaldehyde by catalytic condensation to obtain porphyrin compounds;

[0059] S2: Metallization reaction of porphyrin compounds with zinc salts yields zinc porphyrin complexes, which serve as alcoholysis catalysts.

[0060] In some embodiments, in S1, pyrrole and 4-tert-butylbenzaldehyde are dissolved in an acid solution to carry out an acid-catalyzed condensation reaction. After the reaction solution is cooled to room temperature, the acid is removed by vacuum distillation. The residue is purified by column chromatography using a mixed solvent of cyclohexane and dichloromethane as the developing solvent. After removing the solvent by vacuum distillation, a porphyrin compound is obtained. The reaction formula for this process is as follows:

[0061]

[0062] Among them, R 1 It is -C6H4-C(CH3)3.

[0063] In some embodiments, in S2, the porphyrin compound and the zinc salt are heated and reacted to obtain a zinc porphyrin complex, which serves as the alcoholysis catalyst. The reaction formula for this process is as follows:

[0064]

[0065] Among them, R 1 It is -C6H4-C(CH3)3.

[0066] In some embodiments, in S1, the molar ratio of pyrrole to 4-tert-butylbenzaldehyde is 1.025:1.

[0067] In some embodiments, in S2, the molar ratio of zinc salt to porphyrin compound is 2:1.

[0068] Furthermore, zinc salts include zinc acetate.

[0069] In some embodiments, in S1, the temperature of the catalytic condensation reaction is 140°C to 145°C.

[0070] In some embodiments, in S1, the catalyst used for the catalytic condensation reaction includes propionic acid.

[0071] In some embodiments, the metallization reaction temperature in S2 is 135°C to 145°C;

[0072] In some embodiments, the nitrile compound includes at least one of acetonitrile, trimethylacetonitrile, and benzonitrile.

[0073] Furthermore, the nitrile compounds include at least one of trimethylacetonitrile and acetonitrile.

[0074] Furthermore, nitrile compounds include trimethylacetonitrile. Trimethylacetonitrile not only activates alcohols and promotes the swelling of PET, but also possesses strong steric hindrance and electronic effects. Its tert-butyl group is attached to the nitrile group, making the trimethylacetonitrile molecule itself very stable under reaction conditions and less prone to side reactions, thereby improving the purity and conversion rate of the alcoholysis product. Due to the aforementioned activation and swelling effects, the crystallinity of PET can be destroyed without high temperatures, further reducing the alcoholysis reaction temperature and increasing the PET conversion rate.

[0075] In some embodiments, the alcohol compound includes at least one of methanol, ethanol, and ethylene glycol.

[0076] Furthermore, the alcoholysis agent includes at least one of methanol and ethanol.

[0077] Furthermore, methanol is included as an alcoholysis agent. Methanol is more beneficial for improving PET conversion rate and DMT yield when used as an alcoholysis agent.

[0078] In some embodiments, the molar ratio of the alcoholysis agent to PET is (15~55):1.

[0079] As an example, the molar ratio of the alcoholysis agent to PET can be 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, 51:1, 52:1, 53:1, 54:1, or 55:1, or any two of the above values ​​can be used as endpoints within the range.

[0080] Furthermore, the molar ratio of the alcoholysis agent to PET was (25~45):1. With the increase of the amount of alcoholysis agent added, the PET conversion rate and DMT yield first increased and then decreased, achieving the best balance between the improvement of PET conversion rate and DMT yield at the molar ratio of (25~45):1.

[0081] In some embodiments, the molar ratio of the co-solvent to the alcoholysis agent is (0.25~1.25):1.

[0082] As an example, the molar ratio of the co-solvent to the alcoholysis agent can be 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, or 1.25:1, or any two of the above values ​​can be used as endpoints within the range.

[0083] Furthermore, the molar ratio of the co-solvent to the alcoholysis agent is (0.75~1.25):1. At this molar ratio, the co-solvent can increase the reaction rate, promote the alcoholysis reaction, and further improve the PET conversion rate and DMT yield.

[0084] In some embodiments, the mass ratio of alcoholysis catalyst to PET is (0.05~0.5):100.

[0085] As an example, the mass ratio of alcoholysis catalyst to PET can be 0.05:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, 0.45:100 or 0.5:100, or any two of the above values ​​can be used as endpoints within the range.

[0086] Furthermore, the mass ratio of the alcoholysis catalyst to PET was (0.05~0.2):100. Increasing the amount of alcoholysis catalyst is beneficial to promoting PET alcoholysis, but when the catalyst reaches a certain amount, the PET alcoholysis efficiency is not significantly improved. However, at this mass ratio, not only is the catalyst efficiency high, but the PET conversion rate and DMT yield are further improved.

[0087] In some embodiments, the co-solvent is trimethylacetonitrile and the alcoholysis agent is methanol.

[0088] In some embodiments, the molar ratio of trimethylacetonitrile to methanol is (0.75~1.0):1. At this molar ratio, trimethylacetonitrile not only greatly activates methanol but also significantly increases the contact area and accessibility between the ester bonds of PET and methanol molecules, as well as the catalyst, allowing the reaction to penetrate from the surface into the interior of the material. Moreover, at this molar ratio, trimethylacetonitrile, methanol, and the alcoholysis catalyst interact synergistically, stabilizing the reaction intermediate of the catalyst and helping the catalyst and PET to better disperse and contact in the solvent system, further improving the purity and conversion rate of the alcoholysis reaction products.

[0089] In some embodiments, the temperature for catalytic alcoholysis is 40°C to 140°C.

[0090] As an example, the temperature for catalytic alcoholysis can be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, or 140°C, or any two of the above values ​​as endpoints. In conventional technologies, the alcoholysis temperature for PET is typically between 180°C and 220°C. This application significantly reduces the alcoholysis reaction temperature, achieving PET conversion and DMT yields exceeding 97% even at temperatures as low as 40°C, resulting in unexpected technical advantages.

[0091] Furthermore, the catalytic alcoholysis temperature is 60℃~100℃. At this temperature, not only is the PET conversion rate and DMT yield high, but the reaction conditions are also mild, reducing the process difficulty and cost.

[0092] In some embodiments, the catalytic alcoholysis time is 1 h to 12 h.

[0093] As an example, the catalytic alcoholysis time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, or it can be within the range formed by any two of the above point values ​​as endpoints.

[0094] Furthermore, the catalytic alcoholysis time is 1 h to 2 h.

[0095] In some embodiments, the pressure for catalytic alcoholysis is 0.1 MPa to 2.0 MPa. At this pressure, the reaction conditions are mild, reducing the process difficulty and cost, while traditional alcoholysis of PET requires high temperature and high pressure.

[0096] In some embodiments, the atmosphere for catalytic alcoholysis is nitrogen.

[0097] In some embodiments, the molecular weight of PET is 20,000 to 35,000.

[0098] In some embodiments, the degree of polymerization of PET is 100 to 180.

[0099] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0100] To better illustrate this application, the following description, in conjunction with specific embodiments, further explains its content. The following are specific embodiments.

[0101] Raw material sources: The metal acetate compounds, pyrrole compounds, and aryl formaldehyde compounds involved in this application are all commercially available reagents and can be purchased directly from reagent suppliers.

[0102] Example 1

[0103] Step 1), Preparation of zinc porphyrin complex:

[0104] Freshly distilled 20.5 mmol of pyrrole and 20.0 mmol of 4-tert-butylbenzaldehyde were dissolved in 100 mL of propionic acid solution for acid-catalyzed condensation reaction. The mixture was refluxed and stirred for 8 h until no raw material remained as monitored by TLC (thin-layer chromatography). After the reaction solution was cooled to room temperature, propionic acid was removed by vacuum distillation. The residue was purified by column chromatography using a 3:2 mixture of cyclohexane and dichloromethane as the developing solvent. After removing the solvent by vacuum distillation, 5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrin, also known as m-tetrakis(4-tert-butylphenyl)porphyrin (CAS: 110452-48-7), was obtained.

[0105] 0.5 mmol of Zn(CH3COO)2 and 0.25 mmol of 5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrin were added to a 100 mL round-bottom flask. 30 mL of DMF solvent was added, and the mixture was heated to 140 °C and stirred for 1 h. The solution was then purified by column chromatography using dichloromethane as the developing solvent. The solvent was removed by vacuum distillation to obtain the zinc porphyrin complex. The structural formula of the zinc porphyrin complex is as follows:

[0106]

[0107] The preparation method of zinc porphyrin complexes is from the literature (J. Porphyrins Phthalocyanines, 2017, 21, 465-475, DOI: 10.1142 / S1088424617500456).

[0108] Step 2), using the zinc porphyrin complex obtained above as an alcoholysis catalyst to catalyze the alcoholysis of waste PET:

[0109] Waste PET was cut into 1cm × 1cm sheets. 5.7 g of PET sheets (0.025 mol), 28.5 mg of zinc porphyrin complex (0.5 wt% relative to PET), 24 g of methanol (0.75 mol), and 60.1 g (0.75 mol) of trimethylacetonitrile were placed in a mechanically stirred high-pressure reactor. N2 was introduced into the high-pressure reactor as a protective gas, and the reactor was sealed after the air was replaced three times. The reactor was then stirred and heated to 60°C under stirring. The reaction pressure was controlled at 0.9 MPa, and the catalytic alcoholysis reaction was carried out for 2 hours. After the reaction was completed, the reaction solution was naturally cooled to room temperature and then filtered for the first time to obtain the first filtrate and the first filter residue. The first filter residue was added to 50 mL of ethyl acetate and filtered again to obtain the second filtrate and the second filter residue. The second filter residue was unreacted PET. The first and second filtrates were mixed and the ethyl acetate was removed by vacuum distillation to obtain the DMT product (dimethyl terephthalate).

[0110] Example 2

[0111] Example 2 is basically the same as Example 1, except that the temperature of the catalytic alcoholysis reaction is 100°C and the time is 8 h.

[0112] Example 3

[0113] Example 3 is basically the same as Example 1, except that the temperature of the catalytic alcoholysis reaction is 40°C and the time is 12 h.

[0114] Example 4

[0115] Example 4 is basically the same as Example 1, except that trimethylacetonitrile is replaced with acetonitrile in equimolar mass.

[0116] Example 5

[0117] Example 5 is basically the same as Example 1, except that benzonitrile is used instead of trimethylacetonitrile in equimolar mass.

[0118] Example 6

[0119] Example 6 is basically the same as Example 1, except that ethanol is replaced with equimolar mass.

[0120] Example 7

[0121] Example 7 is basically the same as Example 1, except that the molar ratio of methanol to PET is 55:1.

[0122] Example 8

[0123] Example 8 is basically the same as Example 1, except that the amount of the zinc porphyrin complex used as the alcoholysis catalyst relative to PET is 0.1 wt%.

[0124] Example 9

[0125] Example 9 is basically the same as Example 1, except that the molar ratio of trimethylacetonitrile to methanol is 0.5.

[0126] Example 10

[0127] Example 10 is basically the same as Example 1, except that: 4-tert-butylbenzaldehyde is replaced with an equimolar amount of benzaldehyde to prepare the following alcoholysis catalyst:

[0128] .

[0129] Example 11

[0130] Example 11 is basically the same as Example 1, except that: 4-tert-butylbenzaldehyde is replaced with an equimolar amount of formaldehyde to prepare the following alcoholysis catalyst:

[0131] .

[0132] Example 12

[0133] Example 12 is basically the same as Example 1, except that: 4-tert-butylbenzaldehyde is replaced with an equimolar amount of pentafluorobenzaldehyde to prepare the following alcoholysis catalyst:

[0134]

[0135] Comparative Example 1

[0136] Comparative Example 1 is basically the same as Example 1, except that in step 2), methanol of the same molar mass is used instead of trimethylacetonitrile in Example 1.

[0137] Comparative Example 2

[0138] Comparative Example 2 is basically the same as Example 1, except that in step 2), tetraphenylporphyrin copper is used instead of the zinc porphyrin complex in Example 1.

[0139] The PET conversion rate and DMT yield of each embodiment and comparative example were tested, and the test results are shown in Table 1 below.

[0140] The formula for calculating PET conversion rate is as follows:

[0141]

[0142] Among them, C PET This represents the conversion rate of PET, where m0 represents the initial mass of PET raw material, and m d This indicates the mass of PET remaining after the reaction.

[0143] The formula for calculating the yield of DMT (dimethyl terephthalate) is as follows:

[0144]

[0145] Among them, Y DMT This represents the conversion rate of DMT, m DMT Indicates the mass of the separated DMT; M DMT and M PET represents the relative molecular weights of DMT and PET, respectively, and m0 represents the initial mass of PET raw material.

[0146] The formula for calculating the yield of DET (diethyl terephthalate) is as follows:

[0147]

[0148] Among them, Y DET This represents the conversion rate of DET, m DET Indicates the mass of the separated DET; M DET and M PET represents the relative molecular weights of DET and PET, respectively, and m0 represents the initial mass of PET raw material.

[0149] Table 1

[0150]

[0151] 5.7 g of PET film (0.025 mol) was added back to the filtrate from the first filtration in step 2 of Example 1 and placed in a reaction vessel. The catalytic alcoholysis reaction was repeated multiple times under the same conditions. The results of the cycle are shown in Table 2 below.

[0152] Table 2

[0153]

[0154] contrast Figure 1 and Figure 2 It can be seen that the PET catalytic alcoholysis method in Example 1 successfully alcoholyzed PET into DMT.

[0155] As shown in Tables 1 and 2 above, the alcoholysis methods in Examples 1-11 use metalloporphyrin complexes as catalysts and nitriles as co-solvents to catalyze the alcoholysis of PET. This eliminates the need for high temperature and pressure, and both PET conversion and DMT yield are high at 40°C. The alcoholysis catalyst exhibits high catalytic efficiency, significantly reducing the temperature and catalyst dosage required for PET alcoholysis. Furthermore, the catalyst demonstrates good recyclability; after seven cycles, both PET conversion and DMT yield remain above 83%.

[0156] Moreover, when the co-solvent is trimethylacetonitrile, the alcoholysis agent is methanol, the molar ratio of alcoholysis agent to PET is (25~45):1, the molar ratio of co-solvent to alcoholysis agent is (0.75~1.25):1, the mass ratio of alcoholysis catalyst to PET is (0.05~0.2):100, or the catalytic alcoholysis temperature is 60℃~100℃, the PET conversion rate and DMT yield are higher.

[0157] When the co-solvent is trimethylacetonitrile, the alcoholysis agent is methanol, and the molar ratio of trimethylacetonitrile to methanol is (0.75~1.0):1, the PET conversion rate and DMT yield are both above 99.8%.

[0158] In addition, the catalyst prepared in Example 1 still achieved a PET conversion rate of up to 84% after being recycled 7 times, demonstrating excellent catalyst stability.

[0159] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for catalytic alcoholysis of PET, characterized in that, Includes the following steps: PET was catalytically alcoholized by blending it with an alcoholysis agent, a co-solvent, and an alcoholysis catalyst. The co-solvent includes nitrile compounds; the alcoholysis agent includes alcohol compounds; and the alcoholysis catalyst includes a metalloporphyrin complex, the structural formula of which is as follows: , where R 1 Each is independently one of -H, -C6H5, -C6H4-C(CH3)3, or -C6F5; R 2 Each is independently -H or -CH2CH3; M is Zn.

2. The method for catalytic alcoholysis of PET as described in claim 1, characterized in that, The nitrile compounds include at least one of acetonitrile, trimethylacetonitrile, and benzonitrile.

3. The method for catalytic alcoholysis of PET as described in claim 1 or 2, characterized in that, The nitrile compound includes at least one of trimethylacetonitrile and acetonitrile; and / or, The alcohol compounds include at least one of methanol, ethanol, and ethylene glycol.

4. The method for catalytic alcoholysis of PET as described in any one of claims 1 to 3, characterized in that, The metalloporphyrin complex includes one or more of the following compounds: 。 5. The method for catalytic alcoholysis of PET as described in any one of claims 1 to 4, characterized in that, The molar ratio of the alcoholysis agent to the PET is (15~55):1; and / or, The molar ratio of the co-solvent to the alcoholysis agent is (0.25~1.25):1; and / or, The mass ratio of the alcoholysis catalyst to the PET is (0.05~0.5):

100.

6. The method for catalytic alcoholysis of PET according to any one of claims 1 to 5, characterized in that, The molar ratio of the alcoholysis agent to the PET is (25~45):1; and / or, The molar ratio of the co-solvent to the alcoholysis agent is (0.75~1.25):1; and / or, The mass ratio of the alcoholysis catalyst to the PET is (0.05~0.2):

100.

7. The method for catalytic alcoholysis of PET according to any one of claims 1 to 6, characterized in that, The co-solvent is trimethylacetonitrile, and the alcoholysis agent is methanol.

8. The method for catalytic alcoholysis of PET as described in claim 7, characterized in that, The molar ratio of trimethylacetonitrile to methanol is (0.75~1.0):

1.

9. The method for catalytic alcoholysis of PET according to any one of claims 1 to 8, characterized in that, The catalytic alcoholysis satisfies at least one of the following conditions: (1) The temperature of the catalytic alcoholysis is 40℃~140℃; optionally, the temperature of the catalytic alcoholysis is 60℃~100℃; (2) The catalytic alcoholysis time is 1h to 12h; optionally, the catalytic alcoholysis time is 1h to 2h. (3) The pressure of the catalytic alcoholysis is 0.1 MPa ~ 2.0 MPa; (4) The atmosphere for the catalytic alcoholysis is nitrogen.

10. The method for catalytic alcoholysis of PET according to any one of claims 1 to 9, characterized in that, The PET satisfies at least one of the following conditions: (1) The molecular weight of the PET is 20,000 to 35,000; (2) The degree of polymerization of the PET is 100~180.

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