Preparation method of 1, 3-disubstituted cyclobutane-1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride

Abstract

The invention discloses a preparation method of 1, 3-disubstituted cyclobutane-1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride, which comprises the following steps: (1) uniformly stirring citraconic anhydride, ethyl acetate and a catalyst, carrying out microwave continuous flow reaction, and after the reaction is finished, carrying out suction filtration to obtain a 1, 3-dmcbda crude product I; (2) adding acetic anhydride, heating and stirring, cooling to room temperature, and carrying out suction filtration to obtain a 1, 3-dmcbda crude product II; and adding acetone, heating and refluxing, cooling to room temperature, and carrying out vacuum drying to obtain a 1, 3-dmcbda refined product. The preparation method provided by the invention can enable the 1, 3-dmcbda product to have high yield and high purity, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, and belongs to the technical field of video playback. Background Art

[0002] 1,3-Dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride (1,3-DMCBDA) is an alicyclic dianhydride monomer for synthesizing polyimide; 1,3-DMCBDA adds two methyl groups to the non-conjugated alicyclic structure, which can further increase the distance between polyimide molecular chains, improve the transparency, solubility and dielectric properties of polyimide, meet the needs of photoalignment films, and is widely used in the field of optoelectronic displays.

[0003] Existing patents CN105916866B, CN109422762A, etc. report methods for producing 1,3-dmcbda using citraconic anhydride as raw material. However, the yield of 1,3-dmcbda calculated based on the initial raw materials in the scheme is low, and the content of 1,2-dmcbda is still high, which has low economic benefits and is not conducive to industrial production. Therefore, how to prepare high-yield and high-purity 1,3-dmcbda is still a problem that needs to be solved by the current industry. Summary of the invention

[0004] In view of at least one problem existing in the above-mentioned prior art, the present invention provides a method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, which can make the 1,3-dmcbda product have a high yield and high purity, and is suitable for industrial production.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0006] (1) Citraconic anhydride, ethyl acetate and a catalyst are stirred uniformly, and a microwave continuous flow reaction is performed in a manner of cooling the reaction solution first and then controlling the microwave for multiple cycles. After the reaction is completed, the reaction is filtered to obtain a crude 1,3-dmcbda product I;

[0007] (2) Add acetic anhydride to the above 1,3-dmcbda crude product I, heat it up with stirring, then cool it down to room temperature, and filter it with suction to obtain 1,3-dmcbda crude product II;

[0008] (3) Acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated to reflux, then cooled to room temperature, and then vacuum dried to obtain the fine 1,3-dmcbda product.

[0009] Preferably, in step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -25 to -5°C, then the light wave frequency is controlled to 2350 MHz ± 50 Hz to 2550 MHz ± 50 Hz, the reaction temperature is 5 to 20°C, and the reaction is repeated for 15 to 48 hours.

[0010] Preferably, in step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -20 to -10°C, then the light wave frequency is controlled to 2400MHz±50Hz to 2500MHz±50Hz, the reaction temperature is 10 to 15°C, and the reaction is repeated for 20 to 40 hours.

[0011] Preferably, in step (1), the catalyst is one of p-toluenesulfonic acid, benzenesulfonic acid, dimethylbenzenesulfonic acid and the like.

[0012] Preferably, in step (1), the catalyst is p-toluenesulfonic acid.

[0013] Preferably, in step (1), the amount of the catalyst added is 1 to 2.5% of the mass of citraconic anhydride.

[0014] Preferably, in step (2), the mass ratio of the added amount of acetic anhydride to the mass of citraconic anhydride is 0.5 to 5:1, preferably 2 to 4:1.

[0015] Preferably, in step (2), the conditions for heating and stirring are: temperature of 110-140° C. for 2-10 h; preferably, temperature of 115-130° C. for 3.5-6 h.

[0016] Preferably, in step (3), the mass ratio of the added amount of acetone to the 1,3-dmcbda crude product II is 3 to 10:1, preferably 3 to 6:1.

[0017] Preferably, in step (3), the reflux time is 1 to 5 h, preferably 2.5 to 4 h.

[0018] Preferably, in step (3), the vacuum drying temperature is 50-60°C.

[0019] Beneficial effects of the present invention:

[0020] (1) The preparation method of the present invention can obtain a high-yield product 1,3-dmcbda, the yield is greater than 50%, and the product has high purity, 1,3-dmcbda:1,2-dmcbda≥99.85:0.15.

[0021] (2) The present invention adopts a microwave continuous flow reaction, which is carried out in a multiple cycle mode of first cooling the reaction liquid and then controlling the microwave, thereby increasing the production of 1,3-dmcbda and greatly reducing the production of 1,2-dmcbda isomers. Acetone is used to remove a small amount of residual 1,2-dmcbda by reflux, thereby obtaining a high-purity 1,3-dmcbda product.

[0022] (3) The ethyl acetate, acetic anhydride and acetone used in the present invention are safe, energy-saving and conducive to recycling.

[0023] (4) The present invention uses acetone reflux refining, which uses less amount and is conducive to industrial scale-up production.

[0024] (5) The preparation method of the present invention has controllable process operation, simple process, high product yield and purity, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the NMR spectrum of the reaction solution of Example 1;

[0026] Figure 2 This is the NMR spectrum of the finished product 1,3-dmcbda of Example 1;

[0027] Figure 3 The NMR spectrum of the reaction solution of Comparative Example 3;

[0028] Figure 4 This is the NMR spectrum of the finished product 1,3-dmcbda of Comparative Example 4. DETAILED DESCRIPTION

[0029] The technical scheme in the implementation of the present invention is clearly and completely described below in conjunction with the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the conditions recommended by the normal conditions or the manufacturers. If the manufacturers are not specified in the reagents, instruments, and components used, they are all conventional products that can be purchased commercially.

[0030] Example 1

[0031] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0032] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10°C, repeat the reaction for 24 hours, stop the reaction, filter, and obtain a white solid, i.e., 4.5 kg of crude 1,3-dmcbda I, with a yield of 60%;

[0033] (2) Add 30 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 4 kg of crude 1,3-dmcbda II with a yield of 53.33%;

[0034] (3) 16 kg of acetone was added to the crude 1,3-dmcbda II, heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 3.82 kg of product 1,3-dmcbda, with a yield of 50.93%. The NMR spectrum of the reaction solution was as follows: Figure 1 As shown, the NMR spectrum of the product 1,3-dmcbda is as follows Figure 2 As shown, the ratio of 1,3-dmcbda to 1,2-dmcbda is 99.89:0.11; the yield in this embodiment is calculated relative to citraconic anhydride.

[0035] Example 2

[0036] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0037] (1) 8 kg of citraconic anhydride was added to 36 kg of ethyl acetate, 0.16 kg of p-toluenesulfonic acid as a catalyst was added, and the mixture was stirred evenly. The circulating pump was turned on, and the reaction liquid was cooled to -15°C using an ice machine. The microwave continuous flow reactor was turned on, and the microwave frequency was controlled to be 2400 MHz ± 50 Hz, and the reaction temperature was 12°C. The reaction was repeated for 28 hours, and the reaction was stopped and filtered to obtain a white solid, i.e., 4.92 kg of crude 1,3-dmcbda I, with a yield of 61.5%;

[0038] (2) Add 26 kg of acetic anhydride to the crude product I, raise the temperature to 115°C and stir for 5 hours, then cool to room temperature and filter to obtain 4.42 kg of crude 1,3-dmcbda II with a yield of 55.25%;

[0039] (3) Add 20 kg of acetone to the crude 1,3-dmcbda product II, heat and reflux for 3.5 h, then cool to room temperature, filter, and vacuum dry at a temperature of 55 ° C to obtain 1,3-dmcbda fine product, i.e., product 1,3-dmcbda 4.25 kg, with a yield of 53.13%, 1,3-dmcbda: 1,2-dmcbda is 99.88:0.12; the yield in this embodiment is calculated relative to citraconic anhydride.

[0040] Example 3

[0041] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0042] (1) Add 6 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.06 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -5°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2550 MHz ± 50 Hz, the reaction temperature to 20°C, repeat the reaction for 15 hours, stop the reaction, filter, and obtain a white solid, namely 3.59 kg of crude 1,3-dmcbda I, with a yield of 59.83%;

[0043] (2) Add 15 kg of acetic anhydride to the crude product I, raise the temperature to 125°C and stir for 6 hours, then cool to room temperature and filter to obtain 3.18 kg of crude 1,3-dmcbda II with a yield of 53.0%;

[0044] (3) 18 kg of acetone was added to the crude 1,3-dmcbda product II, heated under reflux for 3 h, then cooled to room temperature, filtered, and vacuum dried at a temperature of 55 ° C to obtain 1,3-dmcbda fine product, i.e., product 1,3-dmcbda 3.01 kg, with a yield of 50.17%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.85:0.15; the yield in this embodiment is calculated relative to citric anhydride.

[0045] Example 4

[0046] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0047] (1) Add 7.5 kg of citraconic anhydride to 45 kg of ethyl acetate, add 0.225 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -25°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2350 MHz ± 50 Hz, the reaction temperature to 5°C, repeat the reaction for 48 hours, stop the reaction, filter, and obtain a white solid, i.e., 4.35 kg of crude 1,3-dmcbda I, with a yield of 58%;

[0048] (2) Add 18 kg of acetic anhydride to the crude product I, raise the temperature to 130° C. and stir for 5.5 h, then cool to room temperature and filter to obtain 3.94 kg of crude 1,3-dmcbda II with a yield of 52.53%;

[0049] (3) 12 kg of acetone was added to the crude 1,3-dmcbda product II, heated to reflux for 3, then cooled to room temperature, filtered, and vacuum dried at a temperature of 60°C to obtain 1,3-dmcbda fine product, i.e., product 1,3-dmcbda 3.75 kg, with a yield of 50.0%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.86:0.14; the yield in this embodiment is calculated relative to citric anhydride.

[0050] Example 5

[0051] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0052] (1) Add 7 kg of citraconic anhydride to 35 kg of ethyl acetate, add 0.105 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -20°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2500 MHz ± 50 Hz, the reaction temperature to 15°C, and cycle the reaction for 36 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.38 kg of crude 1,3-dmcbda I, with a yield of 62.57%;

[0053] (2) Add 21 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 5 h, then cool to room temperature and filter to obtain 4 kg of crude 1,3-dmcbda II with a yield of 57.14%;

[0054] (3) Add 20 kg of acetone to the crude 1,3-dmcbda product II, heat and reflux for 2.5 h, then cool to room temperature, filter, and vacuum dry at a temperature of 55 ° C to obtain 1,3-dmcbda fine product, that is, 3.84 kg of product 1,3-dmcbda, with a yield of 54.86%, and the ratio of 1,3-dmcbda to 1,2-dmcbda is 99.88:0.12; the yield in this embodiment is calculated relative to citric anhydride.

[0055] Example 6

[0056] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0057] (1) Add 6.5 kg of citraconic anhydride to 26 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10°C, repeat the reaction for 24 hours, stop the reaction, filter, and obtain a white solid, i.e., 3.8 kg of crude 1,3-dmcbda I, with a yield of 58.46%;

[0058] (2) Add 26 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 3.44 kg of crude 1,3-dmcbda II with a yield of 52.92%;

[0059] (3) 13.5 kg of acetone was added to the crude 1,3-dmcbda product II, heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum dried at a temperature of 60° C. to obtain 1,3-dmcbda fine product, i.e., 3.26 kg of product 1,3-dmcbda, with a yield of 50.15%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.88:0.15; the yield in this embodiment is calculated relative to citric anhydride.

[0060] Example 7

[0061] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0062] (1) Add 7 kg of citraconic anhydride to 28 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10°C, and cycle the reaction for 24 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.15 kg of crude 1,3-dmcbda I, with a yield of 59.29%;

[0063] (2) Add 28 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 3.72 kg of crude 1,3-dmcbda II with a yield of 53.14%;

[0064] (3) 14.5 kg of acetone was added to the crude 1,3-dmcbda product II, heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum dried at a temperature of 60° C. to obtain 1,3-dmcbda fine product, i.e., product 1,3-dmcbda 3.52 kg, with a yield of 50.29%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.88:0.15; the yield in this embodiment is calculated relative to citric anhydride.

[0065] The yield of the product 1,3-dmcbda prepared in the above embodiment is high and greater than 50%, the purity of the product 1,3-dmcbda is high and the ratio of 1,3-dmcbda:1,2-dmcbda≥99.85:0.15.

[0066] Comparative Example 1

[0067] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0068] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10 ° C, react for 24 hours, stop the reaction, filter, and obtain a white solid, i.e., 4.12 kg of crude 1,3-dmcbda I, with a yield of 54.93%;

[0069] (2) Add 30 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 3.55 kg of crude 1,3-dmcbda II with a yield of 47.33%;

[0070] (3) 14.2 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 33.29 kg of product 1,3-dmcbda, with a yield of 43.87%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.80:0.2; the yield in this comparative example was calculated relative to citric anhydride.

[0071] Comparative Example 2

[0072] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0073] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10°C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10°C, repeat the reaction for 24 hours, stop the reaction, filter, and obtain a white solid, i.e., 3.31 kg of crude 1,3-dmcbda I, with a yield of 44.13%;

[0074] (2) Add 30 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 2.82 kg of crude 1,3-dmcbda II with a yield of 37.6%;

[0075] (3) 11.2 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum dried at 60° C. to obtain 1,3-dmcbda fine product, i.e., 3.57 kg of product 1,3-dmcbda, with a yield of 34.27%, and the ratio of 1,3-dmcbda to 1,2-dmcbda was 99.87:0.13; the yield in this comparative example was calculated relative to citric anhydride.

[0076] Comparative Example 3

[0077] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, the specific steps are as follows:

[0078] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10°C, turn on the light wave reactor, control the wavelength to 365 nm, the reaction temperature to 10°C, repeat the reaction for 24 hours, stop the reaction, filter, and obtain a white solid, i.e., 2 kg of crude 1,3-dmcbda, with a yield of 26.67%;

[0079] (2) Add 15 kg of acetic anhydride to the crude product I, raise the temperature to 120°C and stir for 4 hours, then cool to room temperature and filter to obtain 1.7 kg of crude 1,3-dmcbda II with a yield of 22.67%;

[0080] (3) Add 6.8 kg of acetone to the crude 1,3-dmcbda II, heat and reflux for 4 h, then cool to room temperature, filter, and vacuum dry at 60°C to obtain 1,3-dmcbda fine product, i.e., 1.5 kg of product 1,3-dmcbda, with a yield of 20%. The NMR spectrum of the reaction solution is shown as follows: Figure 3 As shown, the NMR spectrum of the product 1,3-dmcbda is as follows Figure 4As shown, the ratio of 1,3-dmcbda to 1,2-dmcbda is 99.68:0.32; the yield in this comparative example is calculated relative to citraconic anhydride.

[0081] Compared with Comparative Example 1, in Example 1, the reaction solution was first cooled and then subjected to multiple cycle reactions controlled by microwave, and the yield of the prepared product 1,3-dmcbda was higher, with the yield increased by more than 16%, and the purity was also relatively improved.

[0082] Compared with Comparative Example 1, in Example 1, a catalyst was added, and with the same reaction time, the yield of the product 1,3-dmcbda was higher, with the yield increased by more than 48%.

[0083] In Example 1 and Comparative Example 3, microwave continuous flow reaction was used, which could promote the formation of the product 1,3-dmcbda and reduce the generation of by-products, with the yield increased by more than 30%.

[0084] In summary, the product 1,3-dmcbda prepared by the present invention has better quality, reduces the cost of raw materials, and enhances the market competitiveness.

[0085] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit and basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0086] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, characterized in that: The following steps are involved: (1) Citraconic anhydride, ethyl acetate and a catalyst are stirred uniformly, and a microwave continuous flow reaction is performed in a manner of cooling the reaction solution first and then controlling the microwave for multiple cycles. After the reaction is completed, the reaction is filtered to obtain a crude 1,3-dmcbda product I; (2) Add acetic anhydride to the above 1,3-dmcbda crude product I, heat it up with stirring, then cool it down to room temperature, and filter it with suction to obtain 1,3-dmcbda crude product II; (3) Acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated to reflux, then cooled to room temperature, and then vacuum dried to obtain the fine 1,3-dmcbda product.

2. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: Step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -25 to -5°C, then the light wave frequency is controlled to 2350MHz±50Hz to 2550MHz±50Hz, the reaction temperature is 5 to 20°C, and the reaction is repeated for 15 to 48 hours.

3. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (1), the catalyst is one of p-toluenesulfonic acid, benzenesulfonic acid or dimethylbenzenesulfonic acid.

4. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (1), the amount of the catalyst added is 1 to 2.5% of the mass of citraconic anhydride.

5. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (2), the mass ratio of the amount of acetic anhydride added to the mass of citraconic anhydride is 0.5 to 5:

1.

6. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: Step (2), heating and stirring conditions: temperature is 110-140° C., and time is 2-10 h.

7. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (3), the mass ratio of the added amount of acetone to the 1,3-dmcbda crude product II is 3 to 10:

1.

8. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (3), the reflux time is 1 to 5 hours.

9. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (3), the vacuum drying temperature is 50-60°C.

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