Use of pincer manganese complexes in the hydrogenative degradation of polyesters

Abstract

The application discloses application of a pincer manganese complex in polyester hydrogenation degradation, and the pincer manganese complex has the structure shown in the following formula: wherein R is selected from C1-C 20 alkyl or aryl. The application further discloses a method for catalyzing polyester hydrogenation degradation by using the pincer manganese complex. The polyester hydrogenation degradation method has the advantages of high catalyst activity, mild reaction condition, high yield, small environmental pollution, simple operation, easy industrialization and the like, and has a wide market application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to application of a pincer manganese complex in polyester hydrogenation degradation and belongs to the technical field of organic chemistry. BACKGROUND

[0002] With the continuous development of human society, plastics have brought countless conveniences to people's life. Whether it is clothing, food, shelter and transportation, we cannot do without plastics. However, at the same time, the large-scale use of plastics has also caused a global environmental crisis, and discarded plastic garbage can be seen everywhere, which has become one of the main sources of environmental pollution. At present, more than 400 million tons of plastics are produced globally every year, more than half of which is directly discarded in landfills or enters the natural environment after use. The structure of plastic molecules is stable, and it is difficult to be decomposed in the natural environment. Therefore, developing an efficient and green new method for plastic degradation can not only greatly alleviate the problem of environmental pollution, but also convert waste into treasure to transform into high-value-added chemicals, which will have important scientific significance and potential application value.

[0003] As an important class of plastics, polyesters mainly include polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyarylate, etc. Among them, PET products are the most common, with an annual global output of about 800 million tons, accounting for more than 20% of the total global polymer output. Although the output of PET is large, the recycling rate is very low, and only about 30% of PET materials are recycled. At present, PET plastics are mainly recycled by physical methods such as thermal mechanical method, through crushing, melting and reshaping to realize their reuse. However, this method has high requirements for the quality and purity of the plastic to be recycled, and is prone to cause the mechanical property of PET to decrease. In addition, in recent years, the biodegradation method using bacteria and enzymes, etc. can depolymerize PET into small organic molecules under relatively mild conditions. However, the biodegradation method often has the limitations of long degradation period, high cost, difficult product purification and the need for a large amount of buffer solution. In addition to the above two methods, a large amount of PET plastics with color and poor quality are mainly chemically degraded by high-temperature hydrolysis or alcoholysis, but often have problems such as harsh conditions, serious pollution and high cost. Considering that hydrogen is a green energy source with high yield and no pollution in reaction, it is of great significance to use homogeneous catalysts for hydrogenation degradation of PET. For homogeneous catalytic hydrogenolysis reaction, metal catalysts play a crucial role in the activity of the reaction. Metal catalysts include metal centers and ligands, and the ligands have a significant adjusting effect on the space and electronic effect of the metal center. Therefore, the design and synthesis of metal complex catalysts with suitable skeletons are of great significance to degradation. Among them, pincer metal complexes are a class of metal catalysts with high catalytic activity and selectivity, which have been successfully used in PET hydrogenation degradation. However, so far there have been only a few reports, and there are problems such as few types of catalysts (mainly limited to Ru), low catalytic efficiency and harsh reaction conditions. Considering that manganese is the third most abundant transition metal element in the earth's crust, compared with noble metals, it has the advantages of low cost, low toxicity and environmental friendliness, therefore, it is of great significance to develop a new type of pincer manganese complex for efficient and green degradation of polyesters, which not only solves the problem of environmental pollution, but also helps to realize the renewable use of waste plastics and develop circular economy. SUMMARY

[0004] The main purpose of the present application is to provide an application of a pincer manganese complex in polyester hydrogenation degradation to overcome the shortcomings of the prior art.

[0005] Another purpose of the present application is to provide a method for polyester hydrogenation degradation.

[0006] In order to achieve the above-mentioned purposes, the technical solutions adopted by the present application comprise:

[0007] The application provides an application of a pincer manganese complex in polyester hydrogenation degradation, wherein the pincer manganese complex has a structure as shown in formula (I).

[0008]

[0009] wherein R is selected from alkyl or aryl groups containing C1-C 20 alkyl groups.

[0010] The present application also provides a method for hydrogenation degradation of polyester, which comprises: reacting a reaction system containing polyester, an additive added selectively or not, a manganese pincer complex as a catalyst, an alkaline substance and a solvent at a temperature of 25 DEG C or above in a hydrogen atmosphere, so as to degrade the polyester;

[0011] wherein the manganese pincer complex has a structure as shown in formula (I):

[0012]

[0013] wherein R is selected from alkyl or aryl groups containing C1-C 20 alkyl groups.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] (1) The present application provides the application of the manganese pincer complex in the hydrogenation degradation of polyester, which uses a brand-new manganese pincer complex as a catalyst in the polyester degradation method, and improves the disadvantages of the previous method, such as low catalyst efficiency, harsh reaction conditions and high price, so as to efficiently degrade the polyester under relatively mild conditions; the degradation yield of the polyester degradation in the present application is greater than 80%, and the selectivity is greater than 95%;

[0016] (2) The present application proposes to use an additive to cut the macromolecular ester fragments into small molecules and then use the hydrogenation method to improve the efficiency of polyester degradation. DETAILED DESCRIPTION

[0017] In view of the defects of the prior art, the present inventors have long-term research and a large number of practices, and have proposed the technical solution of the present application, which mainly uses a tridentate manganese pincer complex with a quinaldine skeleton of NNP type for the hydrogenation degradation reaction of polyester (such as polyethylene terephthalate) in a hydrogen atmosphere.

[0018] The technical solution of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0019] The preparation method of the manganese pincer complex in the present application is disclosed in the patent application with the application number CN202211609091.X.

[0020] Specifically, as an aspect of the technical solution of the present application, the application of the pincer manganese complex in the hydrogenation degradation of polyester, wherein the pincer manganese complex has the structure as shown in formula (I):

[0021]

[0022] wherein R is selected from C1-C 20 alkyl or aryl.

[0023] Another aspect of the embodiment of the present application further provides a method for the hydrogenation degradation of polyester, which comprises: reacting a reaction system comprising polyester, optionally added additives, a pincer manganese complex as a catalyst, a basic substance and a solvent in a hydrogen atmosphere at a temperature above 25℃, so as to degrade the polyester;

[0024] wherein the pincer manganese complex has the structure as shown in formula (I):

[0025]

[0026] wherein R is selected from C1-C 20 alkyl or aryl.

[0027] In some preferred embodiments, the polyester has the structure as shown in formula (II):

[0028]

[0029] wherein R and R' are independently selected from C1-C 40 fatty groups or C6-C 60 aryl groups, and n has a value of 1-500.

[0030] In some preferred embodiments, the polyester includes polyethylene terephthalate (PET) and / or polybutylene terephthalate, and is not limited thereto.

[0031] In some preferred embodiments, the molar ratio of the polyester, the catalyst, the basic substance and the additives is 1:0.0001:0.0001:0-1:0.05:0.15:500.

[0032] In some preferred embodiments, the temperature of the reaction is 25-200℃.

[0033] Further, the temperature of the reaction is 25-150℃.

[0034] In some preferred embodiments, the time of the reaction is 1-120h.

[0035] In some preferred embodiments, the pressure of the hydrogen atmosphere is 1-100 bar.

[0036] Further, the pressure of the hydrogen atmosphere is 1-50 bar.

[0037] In some preferred embodiments, the additive includes any one or a combination of two or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, cyclohexylamine, n-propylamine, benzylamine, aniline, t-butylamine, and the like, without limitation. In this regard, the present application employs an additive to cut the macromolecular ester fragments into small molecules before hydrogenation to improve the efficiency of polyester degradation.

[0038] In some preferred embodiments, the basic substance includes any one or a combination of two or more of potassium t-butoxide, sodium t-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, and the like, without limitation.

[0039] In some preferred embodiments, the solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, n-hexane, methanol, ethanol, isopropanol, benzene, n-propanol, 1,4-dioxane, dimethyl sulfoxide, dimethylbenzene, anisole, ethylene glycol dimethyl ether, mesitylene, and the like, without limitation.

[0040] The aforementioned pincer manganese complex can efficiently catalyze the degradation of the polyester shown in the following formula, and the reaction is shown in the following formula:

[0041]

[0042] In some more specific embodiments, the method for hydrogenation degradation of the polyester includes:

[0043] In a glove box, the aforementioned pincer manganese complex, basic substance, and solvent are added to a reaction bottle, and after stirring, the polyester (e.g., polyethylene terephthalate) and additive are added. The reaction bottle is placed in a high-pressure reactor and removed from the glove box. Hydrogen gas at a certain pressure is added to the high-pressure reactor, and stirring is performed at a certain temperature for 1-120 hours. After the reaction is completed, the content of the target product, terephthalic alcohol, is detected by the GC internal standard method.

[0044] The technical solutions of the present application are further described in detail below in conjunction with several preferred embodiments. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0045] The experimental materials used in the examples below, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0046] Example 1

[0047] The pincer manganese complex (I) is used as a catalyst for the hydrogenolysis of polyesters:

[0048]

[0049] The catalyst has the following structure:

[0050]

[0051] In a glove box, the pincer manganese complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction bottle, after stirring for 10 minutes, PET (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction bottle was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 120°C for 4 days. After the reaction was completed, an internal standard n-dodecane was added, and the yield of the product terephthalic glycol 1 was 88% by GC detection.

[0052] Example 2

[0053] In a glove box, the pincer manganese complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction bottle, after stirring for 10 minutes, PBT (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction bottle was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80°C for 120h.

[0054] After the reaction was completed, an internal standard n-dodecane was added, and the yield of the product terephthalic glycol 1 was 85% by GC detection.

[0055]

[0056] The catalyst has the following structure:

[0057]

[0058] Example 3

[0059] In a glove box, a manganese pincer complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and methanol (1.5 mL) were added to a reaction vial, and PET (0.2 mmol) was added after stirring for 10 minutes. The reaction vial was placed in an autoclave, and the autoclave was removed from the glove box. Hydrogen gas was added to the autoclave at 5 bar, and the reaction was carried out at 80°C for 4 days. After the reaction was completed, an internal standard n-dodecane was added, and the yield of the product, p-xylene glycol 1, was 80% as detected by GC.

[0060]

[0061] The catalyst has the following structure:

[0062]

[0063] In addition, the present inventors also tested the case where R and R' are each selected from a C1 aliphatic group, a C4 aliphatic group, R is a C 10 aliphatic group, a C 40 aliphatic group, an aryl group containing C6, an aryl group containing C 20 , an aryl group containing C 60 , and the like. The results were similar to those of Application Examples 1-3.

[0064] Example 4

[0065] In a glove box, a manganese pincer complex (5.0 mol%), sodium tert-butoxide (5.0 mol%) and benzene (2.5 mL) were added to a reaction vial, and PET (0.2 mmol) was added after stirring for 10 minutes, and isopropanol (10 mmol) was added. The reaction vial was placed in an autoclave, and the autoclave was removed from the glove box. Hydrogen gas was added to the autoclave at 80 bar, and the reaction was carried out at 80°C for 3 days. After the reaction was completed, an internal standard n-dodecane was added, and the target product, p-xylene glycol 1, was obtained with a yield of 80% as detected by GC.

[0066]

[0067] The catalyst has the following structure:

[0068]

[0069] Example 5

[0070] In a glove box, a pincer manganese complex (0.01 mol%), sodium ethoxide (0.01 mol%) and tetrahydrofuran (1.5 mL) were added to a reaction vial, after stirring for 10 minutes, PET (0.2 mmol) was added, and aniline (1 mmol) was added. The reaction vial was placed in an autoclave, and the autoclave was removed from the glove box. 100 bar of hydrogen was added to the autoclave, and the reaction was carried out at 25°C for 4 days.

[0071] After the reaction was completed, an internal standard n-dodecane was added, and the target product p-xylenediol 1 was obtained by GC detection, with a yield of 80%.

[0072]

[0073] The catalyst has the following structure:

[0074]

[0075] Example 6

[0076] In a glove box, a pincer manganese complex (1.0 mol%), potassium phosphate (3.0 mol%) and 1,4-dioxane (1.5 mL) were added to a reaction vial, after stirring for 10 minutes, PET (0.2 mmol) was added, and t-butylamine (100 mmol) was added. The reaction vial was placed in an autoclave, and the autoclave was removed from the glove box. 1 bar of hydrogen was added to the autoclave, and the reaction was carried out at 200°C for 1 h.

[0077] After the reaction was completed, an internal standard n-dodecane was added, and the target product p-xylenediol 1 was obtained by GC detection, with a yield of 83%.

[0078]

[0079] The catalyst has the following structure:

[0080]

[0081] Example 7

[0082] In a glove box, a pincer manganese complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction vial, after stirring for 10 minutes, PET (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction vial was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80°C for 4 days. After the reaction was completed, an internal standard n-dodecane was added, and the target product p-xylenediol 1 was obtained by GC detection, with a yield of 90%.

[0083]

[0084] wherein the catalyst has a structure shown in the following formula:

[0085]

[0086] Example 8

[0087] In the glove box, the pincer manganese complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to the reaction bottle, after stirring for 10 minutes, the cut mineral water bottle (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction bottle was placed in the autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 80℃ for 4 days. After the reaction was completed, the internal standard n-dodecane was added, and the target product p-xylenediol 1 was obtained by GC detection, with a yield of 80%.

[0088]

[0089] wherein the catalyst has a structure shown in the following formula:

[0090]

[0091] Example 9

[0092] In the glove box, the pincer manganese complex (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to the reaction bottle, after stirring for 10 minutes, the PET film (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction bottle was placed in the autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 80℃ for 4 days.

[0093] After the reaction was completed, the internal standard n-dodecane was added, and the target product p-xylenediol 1 was obtained by GC detection, with a yield of 84%.

[0094]

[0095] wherein the catalyst has a structure shown in the following formula:

[0096]

[0097] Through the above examples, it can be found that the pincer manganese complex in the above technical scheme of the present application can realize the hydrogenation degradation of the polyester, and has good application prospect.

[0098] In addition, the present inventors have also carried out tests with other raw materials, process operations and process conditions described in the present specification with reference to the foregoing examples, and all ideal results have been obtained.

[0099] It should be understood that the technical solutions of the present application are not limited to the specific implementation cases described above, and any technical variations made according to the technical solutions of the present application without departing from the purpose of the present application and the scope protected by the claims all fall within the protection scope of the present application.

Claims

1. A method for the hydrogenation degradation of polyester, characterized in that, include: In a hydrogen atmosphere, a reaction system comprising polyester, additives, a pincer-shaped manganese complex as a catalyst, an alkaline substance, and a solvent is reacted at a temperature of 25°C, thereby degrading the polyester; wherein the additives include any one or a combination of two or more of cyclohexylamine, n-propylamine, benzylamine, aniline, and tert-butylamine. The pincer-shaped manganese complex has a structure as shown in formula (I): ; Wherein, R is selected from those containing C1-C 20 Alkyl or aryl groups; The polyester has a structure as shown in formula (II): ; Among them, R and R' are both independently selected from those containing C1-C 40 Fatty groups or containing C6-C 60 The aryl group, where n takes values ​​from 1 to 500.

2. The method according to claim 1, characterized in that, The polyester includes polyethylene terephthalate and / or polybutylene terephthalate.

3. The method according to claim 1, characterized in that: The reaction time is 1 to 120 hours.

4. The method according to claim 1, characterized in that: The pressure of the hydrogen atmosphere is 1~100 bar.

5. The method according to claim 4, characterized in that: The pressure of the hydrogen atmosphere is 1~50 bar.

6. The method according to claim 1, characterized in that: The alkaline substance includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amino, sodium bis(trimethylsilyl)amino, and lithium bis(trimethylsilyl)amino.

7. The method according to claim 1, characterized in that: The solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, n-hexane, methanol, ethanol, isopropanol, benzene, n-propanol, 1,4-dioxane, dimethyl sulfoxide, xylene, anisole, ethylene glycol dimethyl ether, and mesitylene.

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