A method for preparing tetrahydrofuran by hydrolysis of polybutylene diglycolate catalyzed by ionic liquid

Abstract

The application discloses a method for preparing tetrahydrofuran by hydrolyzing polybutylene glycol diacid ester with ionic liquid as a catalyst. The method comprises the following steps: performing a polybutylene glycol diacid ester hydrolysis reaction in the temperature range of 50-200 DEG C with ionic liquid as a solvent and a catalyst, and distilling to obtain tetrahydrofuran. The method has the advantages of high efficiency, greenness, mild reaction conditions and the like, can catalyze polybutylene glycol diacid ester to hydrolyze to generate tetrahydrofuran, and has strong industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste plastic recycling, and particularly relates to a method for preparing tetrahydrofuran by hydrolysis of polybutylene succinate with ionic liquid as catalyst. BACKGROUND

[0002] Polybutylene succinate (such as polybutylene succinate, polybutylene adipate, polybutylene terephthalate, etc.) is a kind of polymer obtained by polycondensation of diacid and butanediol, and has excellent mechanical properties and biodegradable characteristics, and has been widely used in food, pesticide and packaging fields. With the rapid development of human society, the demand for polybutylene succinate is rapidly increasing, and its waste is also increasing. Although this kind of polyester can be naturally degraded, the time required is relatively long, and the degradation product is CO2, which is not conducive to carbon reduction and causes resource waste. Therefore, there is an urgent need for artificial methods to convert it into useful substances. Pyrolysis and chemical conversion are effective methods for rapidly degrading polybutylene succinate. The pyrolysis method needs to be carried out at high temperature, has poor selectivity of degradation products, high energy consumption and poor effect. By using the catalytic chemical depolymerization method, it is expected to depolymerize and convert this kind of polyester into high-value-added chemicals, such as diacid and its derivatives, and butanediol and its derivatives, etc. At present, there is no report on the preparation of tetrahydrofuran by hydrolysis of polybutylene succinate.

[0003] Ionic liquid is a kind of low-temperature molten salt composed of organic cation and inorganic / organic anion, and has the characteristics of molecular solvent and molten salt. Through different combinations of anions and cations, or complexing with Lewis acid, ionic liquid has a wide range of structure and function designability. Especially, in ionic liquid system, various interactions such as electrostatic interaction, hydrogen bonding interaction and metal coordination interaction coexist, and it is easy to form ionic microenvironment, so it is applied in many fields. In the resource utilization of waste plastics, ionic liquid plays an important role due to its unique solubility and catalytic characteristics. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing tetrahydrofuran by hydrolysis of polybutylene succinate with ionic liquid as catalyst.

[0005] The method for preparing tetrahydrofuran by hydrolysis of polybutylene succinate with ionic liquid as catalyst provided by the present application comprises the following steps: carrying out polybutylene succinate hydrolysis reaction with ionic liquid as solvent and catalyst in a temperature range of 50-200℃, and distilling to obtain tetrahydrofuran.

[0006] In the above method, the ionic liquid is a Lewis acid ionic liquid formed by 1-alkyl-3-alkyl imidazole halide and Lewis acid,

[0007] In the above method, the ionic liquid is a Lewis acid ionic liquid formed by 1-alkyl-3-alkyl imidazole halide and Lewis acid,

[0008] The structure of the 1-alkyl-3-alkyl imidazole halide is shown as follows:

[0009]

[0010] wherein R1, R2 are each independently selected from C1-C6 linear or branched alkyl, and can be selected from n-butyl, methyl, ethyl;

[0011] X is halogen, including chlorine, bromine and iodine;

[0012] In some embodiments of the present application, the 1-alkyl-3-alkyl imidazole halide can be selected from at least one of 1-butyl-3-methyl imidazole chloride, 1-butyl-3-methyl imidazole bromide, 1-butyl-3-methyl imidazole iodide, 1-ethyl-3-methyl imidazole chloride, 1-ethyl-3-methyl imidazole bromide, 1-ethyl-3-methyl imidazole iodide,

[0013]

[0014] The Lewis acid can be selected from at least one of ZnCl2, ZnBr2, ZnI2, FeCl3, CrCl3.

[0015] The polybutylene diacid can be selected from at least one of polybutylene succinate, polybutylene adipate, polybutylene terephthalate.

[0016] The specific operation of the above method is as follows: the 1-alkyl-3-alkyl imidazole halide and the Lewis acid are prepared into an ionic liquid, the polybutylene diacid, the ionic liquid and water are mixed, sealed, stirred and heated for reaction, after the reaction is completed, the mixture is cooled to room temperature, and then distilled to obtain tetrahydrofuran.

[0017] In the method, the molar ratio of the ionic liquid to the polyester structural unit can be 15:1-0.1:1, preferably 1-3:1, 1:1, 2:1 or 3:1.

[0018] The molar ratio of the polyester structural unit to water can be 1:1-1:10, preferably 1:2-5, 1:2, 1:3 or 1:5.

[0019] The temperature of the hydrolysis reaction can be 80-200℃, preferably 120-140℃.

[0020] The time of the hydrolysis reaction can be 8-36h, preferably 24h.

[0021] The above method further comprises the following operation: the distillation liquid from which tetrahydrofuran is removed is cooled and crystallized, the butanedioic acid solid is separated out, and then centrifuged to collect the butanedioic acid product; the ionic liquid is recovered from the filtrate, and the obtained ionic liquid is reused.

[0022] The present application can be used for the research and development of the preparation of tetrahydrofuran by hydrolysis of polybutylene succinate by the structural design of the ionic liquid, which has specific properties. The method provided by the present application has the advantages of high efficiency, greenness and mild reaction conditions, and can catalyze the hydrolysis of polybutylene succinate to generate tetrahydrofuran, and has strong industrial application value. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in combination with specific embodiments. The examples provided below are only used to illustrate the present application, and are not intended to limit the scope of the present application. The examples provided below can be used as a guide for further improvement by those skilled in the art, and do not constitute any limitation on the present application.

[0024] In the following examples, the experimental methods are conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents and the like used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0025] Example 1: Ionic liquid BmimCl·2ZnCl2catalyzing the hydrolysis of polybutylene succinate to prepare tetrahydrofuran

[0026] BmimCl was mixed with 2 equivalents of ZnCl2 to form ionic liquid BmimCl·2ZnCl2. 1.72 g of polybutylene succinate (10 mmol of monomer), 20 mmol of ionic liquid BmimCl·2ZnCl2 and 20 mmol of water were placed in a 25 ml single-neck flask, and sealed. Then, the mixture was moved to a 120℃ oil bath and stirred and heated for 24 hours. After the reaction was completed, the mixture was cooled to room temperature. The reaction liquid was moved to a 25 ml distillation flask, and tetrahydrofuran was collected by distillation at 80℃. The separation yield was 80%. The distillation liquid from which tetrahydrofuran was removed was cooled and crystallized, and after the separation of succinic acid solid by centrifugation, the separation yield was 83%.

[0027] NMR data of tetrahydrofuran: 1 H NMR (400 MHz, DMSO-d6, 25℃): δ = 3.56 (m, 4H), 1.71 ppm (m, 4H); 13 C NMR (101 MHz, DMSO-d6, 25℃): δ = 68.94, 26.62 ppm.

[0028] Example 2: Ionic liquid BmimCl·4ZnCl2catalyzing the hydrolysis of polybutylene succinate to prepare tetrahydrofuran

[0029] BmimCl was mixed with 4 equivalents of ZnCl2and stirred to form ionic liquid BmimCl-4ZnCl2. 1.72 g of polybutylene succinate (10 mmol of monomer), 10 mmol of ionic liquid BmimCl-4ZnCl2, and 20 mmol of water were placed in a 25 ml single-neck flask, sealed, and moved to a 120°C oil bath for stirring and heating for 24 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 25 ml distillation flask and distilled at 80°C to collect tetrahydrofuran with a separation yield of 88%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after the separation of succinic acid solid by centrifugation, the separation yield was 90%.

[0030] Example 3, Hydrolysis of polybutylene succinate catalyzed by ionic liquid BmimCl-4ZnCl2to prepare tetrahydrofuran

[0031] 1.72 g of polybutylene succinate (10 mmol of monomer), 20 mmol of ionic liquid BmimCl-4ZnCl2, and 30 mmol of water were placed in a 25 ml single-neck flask, sealed, and moved to a 140°C oil bath for stirring and heating for 18 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 25 ml distillation flask and distilled at 80°C to collect tetrahydrofuran with a separation yield of 92%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after the separation of succinic acid solid by centrifugation, the separation yield was 98%.

[0032] Example 4, Hydrolysis of polybutylene succinate catalyzed by ionic liquid BmimCl-4ZnCl2to prepare tetrahydrofuran

[0033] 2.0 g of polybutylene succinate (10 mmol of monomer), 20 mmol of ionic liquid BmimCl-4ZnCl2, and 20 mmol of water were placed in a 25 ml single-neck flask, sealed, and moved to a 120°C oil bath for stirring and heating for 24 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 25 ml distillation flask and distilled at 80°C to collect tetrahydrofuran with a separation yield of 80%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after the separation of succinic acid solid by centrifugation, the separation yield was 82%.

[0034] Example 5, Hydrolysis of polybutylene succinate catalyzed by ionic liquid BmimCl-4ZnCl2to prepare tetrahydrofuran

[0035] Put 2.0 g of polybutylene adipate (10 mmol of monomer), 30 mmol of ionic liquid BmimCl-4ZnCl2, and 30 mmol of water in a 50-milliliter single-neck flask, seal, move to a 140°C oil bath, and stir and heat for 24 hours. After the reaction is complete, cool to room temperature. Move the reaction liquid to a 50-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate at a yield of 85%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after adipic acid solid is separated out, and obtain a separation yield of 88%.

[0036] Example 6, Ionic liquid BmimBr-2ZnBr2 catalyzes polybutylene succinate hydrolysis to prepare tetrahydrofuran

[0037] Mix and stir BmimBr with 2 equivalents of ZnBr2 to form ionic liquid BmimBr-2ZnBr2. Put 1.72 g of polybutylene succinate (10 mmol of monomer), 20 mmol of ionic liquid BmimBr-2ZnBr2, and 20 mmol of water in a 25-milliliter single-neck flask, seal, move to a 120°C oil bath, and stir and heat for 24 hours. After the reaction is complete, cool to room temperature. Move the reaction liquid to a 25-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate at a yield of 90%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after succinic acid solid is separated out, and obtain a separation yield of 92%.

[0038] Example 7, Ionic liquid BmimBr-3ZnBr2 catalyzes polybutylene succinate hydrolysis to prepare tetrahydrofuran

[0039] Mix and stir BmimBr with 3 equivalents of ZnBr2 to form ionic liquid BmimBr-3ZnBr2. Put 1.72 g of polybutylene succinate (10 mmol of monomer), 30 mmol of ionic liquid BmimBr-3ZnBr2, and 20 mmol of water in a 50-milliliter single-neck flask, seal, move to a 130°C oil bath, and stir and heat for 24 hours. After the reaction is complete, cool to room temperature. Move the reaction liquid to a 50-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate at a yield of 93%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after succinic acid solid is separated out, and obtain a separation yield of 96%.

[0040] Example 8, Ionic liquid BmimBr-3ZnBr2 catalyzes polybutylene adipate hydrolysis to prepare tetrahydrofuran

[0041] Put 2.0 g of polybutylene adipate, 30 mmol of ionic liquid BmimBr-3ZnBr2, and 30 mmol of water in a 50-milliliter single-neck flask, seal; move to a 140°C oil bath, stir and heat for 24 hours; after the reaction is complete, cool to room temperature. Move the reaction liquid to a 50-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate with a yield of 90%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after adipic acid solid is precipitated, and obtain a separation yield of 92%.

[0042] Example 8, Ionic liquid BmimBr-4ZnBr2 catalyzes polybutylene adipate hydrolysis to prepare tetrahydrofuran

[0043] Put 2.0 g of polybutylene adipate, 20 mmol of ionic liquid BmimBr-4ZnBr2, and 20 mmol of water in a 25-milliliter single-neck flask, seal; move to a 150°C oil bath, stir and heat for 24 hours; after the reaction is complete, cool to room temperature. Move the reaction liquid to a 25-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate with a yield of 95%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after adipic acid solid is precipitated, and obtain a separation yield of 97%.

[0044] Example 9, Ionic liquid EmimCl-3ZnCl2 catalyzes polybutylene adipate hydrolysis to prepare tetrahydrofuran

[0045] Put 2.0 g of polybutylene adipate, 20 mmol of ionic liquid BmimCl-3ZnCl2, and 20 mmol of water in a 25-milliliter single-neck flask, seal; move to a 140°C oil bath, stir and heat for 24 hours; after the reaction is complete, cool to room temperature. Move the reaction liquid to a 25-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate with a yield of 90%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after adipic acid solid is precipitated, and obtain a separation yield of 93%.

[0046] Example 10, Ionic liquid BmimCl-3FeCl3 catalyzes polybutylene adipate hydrolysis to prepare tetrahydrofuran

[0047] Mix BmimCl and 3 equivalents of FeCl3 and stir to form ionic liquid BmimCl-3FeCl3. Put 1.72 g of polybutylene adipate, 30 mmol of ionic liquid BmimCl-3ZnCl2, and 30 mmol of water in a 50-milliliter single-neck flask, seal; move to a 140°C oil bath, stir and heat for 24 hours; after the reaction is complete, cool to room temperature. Move the reaction liquid to a 50-milliliter distillation flask, distill at 80°C, collect tetrahydrofuran, and separate with a yield of 91%. Perform cooling crystallization on the distillation liquid from which tetrahydrofuran has been removed, centrifuge after adipic acid solid is precipitated, and obtain a separation yield of 93%.

[0048] Example 11, Ionic liquid BmimCl-2CrCl3 catalyzed hydrolysis of poly(butylene succinate) to prepare tetrahydrofuran

[0049] BmimCl was mixed with 2 equivalents of CrCl3 and stirred to form ionic liquid BmimCl-2CrCl3. 1.72 g of poly(butylene succinate), 30 mmol of ionic liquid BmimCl-2CrCl3, and 30 mmol of water were placed in a 50 mL single-neck flask, sealed, and moved to a 140 °C oil bath for stirring and heating for 24 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 50 mL distillation flask and distilled at 80 °C to collect tetrahydrofuran with a separation yield of 92%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after succinic acid solid was separated out, centrifugation was performed to obtain a separation yield of 94%.

[0050] Example 12, Ionic liquid BmimI-2ZnI2 catalyzed hydrolysis of poly(butylene succinate) to prepare tetrahydrofuran

[0051] BmimI was mixed with 2 equivalents of ZnI2 and stirred to form ionic liquid BmimI-2ZnI2. 1.72 g of poly(butylene succinate), 30 mmol of ionic liquid BmimI-2ZnI2, and 30 mmol of water were placed in a 50 mL single-neck flask, sealed, and moved to a 130 °C oil bath for stirring and heating for 24 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 50 mL distillation flask and distilled at 80 °C to collect tetrahydrofuran with a separation yield of 88%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after succinic acid solid was separated out, centrifugation was performed to obtain a separation yield of 90%.

[0052] Example 13, Ionic liquid BmimI-2ZnI2 catalyzed hydrolysis of poly(butylene succinate) to prepare tetrahydrofuran

[0053] BmimI was mixed with 2 equivalents of ZnI2 and stirred to form ionic liquid BmimI-2ZnI2. 1.72 g of poly(butylene succinate), 30 mmol of ionic liquid BmimI-2ZnI2, and 30 mmol of water were placed in a 50 mL single-neck flask, sealed, and moved to a 130 °C oil bath for stirring and heating for 24 hours. After the reaction was completed, the reaction liquid was cooled to room temperature. The reaction liquid was moved to a 50 mL distillation flask and distilled at 80 °C to collect tetrahydrofuran with a separation yield of 88%. The distillation liquid from which tetrahydrofuran was removed was subjected to cooling crystallization, and after succinic acid solid was separated out, centrifugation was performed to obtain a separation yield of 90%.

[0054] Example 14, Ionic liquid BmimCl-4ZnCl2 catalyzed hydrolysis of poly(butylene succinate) to prepare tetrahydrofuran cyclic test experiment.

[0055] The experimental conditions and procedures were the same as in Example 3, except that the ionic liquid was replaced by the ionic liquid recovered in the example, and five repeated use experiments were carried out. The ionic liquid recovery process: the ionic liquid from which tetrahydrofuran and succinic acid were removed by distillation and centrifugation was placed in a vacuum drying oven at 60°C and dried for 24h. The results of repeated use of the ionic liquid are shown in Table 1.

[0056] Table 1: Circulation test conditions

[0057]

[0058] The above describes the present application in detail. For those skilled in the art, without departing from the purpose and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wide range of equivalent parameters, concentrations and conditions. Although the present application gives a special example, it should be understood that further improvements can be made to the present application. In summary, according to the principle of the present application, this application intends to include any change, use or improvement of the present application, including changes made by conventional techniques known in the art, which deviates from the range disclosed in the present application.

Claims

1. A method for preparing tetrahydrofuran by hydrolysis of polybutylene diacidate catalyzed by ionic liquid, comprising the following steps: hydrolyzing polybutylene diacidate in a temperature range of 50~200℃ using an ionic liquid as solvent and catalyst, followed by distillation to obtain tetrahydrofuran; The ionic liquid is a Lewis acid ionic liquid formed from a 1-alkyl-3-alkylimidazolium halide and a Lewis acid; The structural formula of the 1-alkyl-3-alkylimidazolium halide is shown below: in, R1 and R2 are each independently selected from C1-C6 straight-chain or branched alkyl groups; X represents halogens, including chlorine, bromine, and iodine.

2. The method according to claim 1, characterized in that, The molar ratio of 1-alkyl-3-alkylimidazolium halide to Lewis acid is 1:1 to 1:

5.

3. The method according to claim 1, characterized in that, The 1-alkyl-3-alkylimidazolium halide is selected from at least one of the following: 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, and 1-ethyl-3-methylimidazolium iodide.

4. The method according to claim 1, characterized in that, The Lewis acid is selected from at least one of ZnCl2, ZnBr2, ZnI2, FeCl3, and CrCl3.

5. The method according to claim 1, characterized in that, The polybutylene dibutyl succinate is selected from at least one of polybutylene succinate, polybutylene adipate, and polybutylene terephthalate.

6. The method according to claim 1, characterized in that, The method is as follows: 1-alkyl-3-alkylimidazolium halide and Lewis acid are prepared into an ionic liquid, polybutylene diacetate, ionic liquid and water are mixed, sealed, stirred and heated to react, after the reaction is completed, cooled to room temperature, and distilled to obtain tetrahydrofuran.

7. The method according to claim 6, characterized in that, The molar ratio of the ionic liquid to the polyester structural unit is 15:1 to 0.1:1; The molar ratio of the polyester structural unit to water is 1:1 to 1:

10.

8. The method according to claim 6, characterized in that, The hydrolysis reaction is carried out at a temperature of 80~200℃; The hydrolysis reaction takes 8 to 36 hours.

9. The method according to claim 6, characterized in that, The method further includes the following operations: cooling and crystallizing the distillate after removing tetrahydrofuran, centrifuging to precipitate succinic acid solid, collecting the succinic acid product; recovering the ionic liquid from the filtrate, and reusing the obtained ionic liquid.

Images