Method for preparing tetramethyl cyclobutanedione

Abstract

The invention provides a method for preparing tetramethyl cyclobutanedione, which comprises the following steps: (1) absorbing gas rich in dimethyl ketene DMK by a first absorbent to obtain a first absorption solution; (2) carrying out polymerization reaction on the first absorption solution, cooling and separating out a solid product; (3) dissolving the solid product in a second absorbent to prepare a third absorbent; (4) absorbing the gas rich in dimethyl ketene DMK by a third absorbent to obtain a second absorption solution; and (5) carrying out cyclization reaction on the second absorption solution to obtain a TMCB (tetramethyl cyclobutanedione)-containing solution. The method comprises the following steps: reacting an initial absorption solution under a certain condition to form an absorption aid; the auxiliary agent is used for absorbing and improving the yield of the cyclization process, the concentration of DMK in the solution after absorption can be remarkably improved, and the yield of TMCB in the cyclization process is higher than 99.5%.

Description

Technical Field

[0001] The invention relates to a method for preparing tetramethylcyclobutanedione. Background Art

[0002] Polyester is the most commonly used polymer in people's daily life. my country is a major polyester producer. By 2022, the output of polyethylene terephthalate (PET) in my country has reached more than 50 million tons. However, the operating temperature of PET needs to be below 80°C. To improve the heat resistance of polyester and make its operating temperature reach above 100°C, the most direct method is to use rigid diol monomer copolymerization modification. Among them, the most widely used rigid diol monomer is 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO).

[0003] CBDO is usually obtained from dimethyl ketone (DMK) through a series of complex reactions such as dimerization, hydrogenation, and isomerization. The basis of this series of complex reactions is to obtain a DMK solution of a certain concentration. The industrialized DMK preparation method is to produce DMK through thermal cracking of isobutyric anhydride, and then absorb it with ester solvents after concentration. Due to the low solubility of DMK in ester solvents, the amount of solvent used in the absorption process is huge, and the DMK solution after absorption is very easy to undergo addition of carbon-carbon double bonds and carbon-oxygen double bonds at low temperatures, resulting in an increase in product impurities. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a new process for DMK absorption and cyclization, which includes reacting the initial absorption solution under certain conditions to form an absorption aid; and using the aid for absorption and improving the yield of the cyclization process. This method can significantly increase the concentration of DMK in the solution after absorption and make the TMCB yield of the cyclization process higher than 99.5%.

[0005] To achieve the above-mentioned object, the present invention provides a method for preparing tetramethylcyclobutanedione, which comprises the following steps: (1) absorbing a gas rich in dimethyl ketone (DMK) by a first absorbent to obtain a first absorption solution;

[0006] (2) subjecting the first absorption solution to a polymerization reaction, and precipitating a solid product after cooling;

[0007] (3) dissolving the solid product in the second absorbent to prepare a third absorbent;

[0008] (4) absorbing the gas rich in dimethyl ketone (DMK) through a third absorbent to obtain a second absorption solution;

[0009] (5) subjecting the second absorption solution to a cyclization reaction to obtain a tetramethylcyclobutanedione TMCB solution. The method of the present invention comprises reacting the initial absorption solution under certain conditions to form an absorption aid; and using the aid for absorption and improving the yield of the cyclization process. The method can significantly increase the concentration of DMK in the solution after absorption, and make the TMCB yield of the cyclization process higher than 99.5%.

[0010] In the present invention, in step (1) and step (3), the optional range of types of the first absorbent and the second absorbent is relatively wide, and all types of absorption solvents commonly used in the art can be used in the present invention. For the present invention, it is preferred that the first absorbent and the second absorbent are selected from any one or more of fatty acid alkyl esters, fatty acid anhydrides, and alkanes.

[0011] In the present invention, there is no special requirement for the types of fatty acid alkyl esters, fatty acid anhydrides, and alkanes, and the types commonly used in the art can be used in the present invention. The types of substances are exemplified below, but the scope of the present invention is not limited thereby.

[0012] According to one embodiment of the present invention, the structure of the fatty acid alkyl ester is as follows:

[0013]

[0014] Wherein, R1 is H or an alkyl group having 1 to 6 carbon atoms, and R2 is an alkyl group having 1 to 6 carbon atoms;

[0015] Preferably, the fatty acid alkyl ester is one or more of n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, n-butyl propionate, n-butyl butyrate, ethyl isobutyrate, propyl isobutyrate and isobutyl isobutyrate.

[0016] According to one embodiment of the present invention, the structure of the fatty acid anhydride is as shown in formula (II):

[0017]

[0018] Wherein, R3 and R4 are H, alkyl with 1 to 6 carbon atoms;

[0019] Preferably, the fatty acid anhydride is one or more of isobutyric anhydride, acetic isobutyric anhydride, acetic anhydride, propionic anhydride, and propionic isobutyric anhydride.

[0020] According to one embodiment of the present invention, the alkane is a C6-10 alkane; preferably, the alkane is one or more of n-hexane, n-heptane, 2-methylheptane, and n-octane.

[0021] According to one embodiment of the present invention, the first absorbent is selected from one or more of n-hexane, isobutyl isobutyrate, and isobutyric anhydride.

[0022] According to one embodiment of the present invention, the second absorbent is selected from one or more of n-butyl acetate, n-pentyl acetate, and propionic acid isobutyric anhydride.

[0023] In the present invention, the optional range of the absorption conditions in step (1) and step (4) is relatively wide. Preferably,

[0024] The absorption conditions in step (1) and step (4) each include: a temperature of -30°C to 30°C, preferably -20°C to 10°C.

[0025] According to one embodiment of the present invention, the absorption conditions in step (1) include a temperature of -15°C to 10°C.

[0026] According to one embodiment of the present invention, the absorption conditions in step (4) include: a temperature of -20°C to -10°C.

[0027] In the present invention, there is no special requirement for the polymerization conditions. According to the present invention, the polymerization reaction conditions of step (2) include: the reaction pressure is 0.1-10 MPa, preferably 0.1-5 MPa, and more preferably 0.3-1.5 MPa.

[0028] Exemplarily, for the present invention, the polymerization reaction conditions of step (2) include: a temperature of -100°C to 20°C, preferably -80°C to 10°C, and more preferably -50°C to 10°C.

[0029] Exemplarily, for the present invention, the polymerization reaction conditions of step (2) include: reaction time of 2-20 h, preferably 4-15 h, more preferably 8-10 h.

[0030] In the present invention, there is no special requirement for the cooling conditions. According to one embodiment of the present invention, in step (2), the terminal temperature of cooling is -50°C to 10°C, preferably -50°C to -10°C.

[0031] In the present invention, the molecular weight of the solid product has a wide optional range. According to a preferred embodiment of the present invention, the molecular weight of the solid product is 300-1500, preferably 300-1000, more preferably 600-980, for example, 600, 650, 700, 750, 800, 850, 900, 950, etc.

[0032] In the present invention, the concentration range of the solid product in the third absorption solvent can be selected relatively wide and can be specifically selected according to needs. According to one embodiment of the present invention, the concentration of the solid product in the third absorption solvent is 0.1-3wt%, preferably 0.1-1wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%.

[0033] The present invention has no special requirements on the conditions of the cyclization reaction in step (5), which can be conventional cyclization reaction conditions. According to one embodiment of the present invention, an exemplary description includes: the cyclization pressure is 0.1-5MPa, preferably 0.1-3MPa, and more preferably 0.5-1MPa.

[0034] According to one embodiment of the present invention, exemplary descriptions include: the cyclization temperature is 80-180°C, preferably 100-160°C, and more preferably 100-130°C.

[0035] According to one embodiment of the present invention, exemplary description includes: the cyclization time is 0.5-6h, preferably 1-5h, more preferably 2-5h.

[0036] The present invention has no special requirements on the composition of the dimethyl ketene-rich gas. Any gas containing dimethyl ketene can be absorbed by the absorption method of the present invention. The following is an exemplary description of the implementation of the present invention, but the present invention is not limited to this scope.

[0037] According to one embodiment of the present invention, the volume content of dimethyl ketone in the dimethyl ketone-rich gas is 5-90%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%.

[0038] According to one embodiment of the present invention, preferably, the dimethyl ketene-rich gas contains 5-70% dimethyl ketene, and the rest is inert gas.

[0039] The present invention has no special requirements on the source of the dimethyl ketene-rich gas. According to the present invention, the dimethyl ketene-rich gas is preferably obtained by thermal cracking of isobutyric acid and / or isobutyric anhydride, and then cooling in multiple stages to remove isobutyric acid and / or isobutyric anhydride in the system.

[0040] In the present invention, there is no special requirement for the reaction conditions of the thermal cracking process. The following is an exemplary description of the implementation mode of the present invention, but the present invention is not limited to this scope.

[0041] According to one embodiment of the present invention, the reaction conditions of the thermal cracking process include: a temperature of 350 to 650°C, preferably 350 to 550°C.

[0042] According to one embodiment of the present invention, the pressure is 1 kPa to 0.3 MPa, preferably 10 kPa to 0.1 MPa.

[0043] According to one embodiment of the present invention, the residence time is 0.1 to 4 s, preferably 0.1 to 1 s.

[0044] According to one embodiment of the present invention, a dilution gas is introduced during thermal cracking.

[0045] In the present invention, there is no special requirement for the amount and type of the dilution gas. The following is an exemplary description of the implementation of the present invention, but the present invention is not limited to this scope.

[0046] According to one embodiment of the present invention, the volume ratio of isobutyric acid and / or isobutyric anhydride to the diluent gas is (1:30) to (1:0.2), preferably (1:20) to (1:0.5).

[0047] According to one embodiment of the present invention, the dilution gas is selected from inert gases, preferably nitrogen.

[0048] The method of the present invention can overcome the defects of the prior art in that the amount of solvent used in the dimethyl vinyl ketone (DMK) absorption process is large and the absorption efficiency is low, and can significantly increase the concentration of DMK in the solution after absorption.

[0049] According to the method of the present invention, the TMCB yield in the cyclization process is higher than 99.5%. DETAILED DESCRIPTION

[0050] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0051] In the present invention, the structural formula of dimethyl ketone DMK is as follows:

[0052]

[0053] In the present invention, the structural formula of tetramethylcyclobutanedione is as follows:

[0054]

[0055] The DMK concentration in the solution was obtained by chromatographic analysis of the test substance content, and the calculation method of the DMK equilibrium concentration after absorption was: the mass of DMK in the solution / the total mass of the absorption solution.

[0056] The DMK-rich gas in the present invention is produced by the following method: isobutyric anhydride is introduced into a 300° C. vaporizer at a rate of 1.2 mL / min, the vaporized isobutyric anhydride gas is mixed with hot nitrogen at a flow rate of 4.8 L / min (nitrogen preheating temperature is 300° C.), and the mixed gas is introduced into a thermal cracking reactor, the reactor is made of a quartz tube, the size is 15 mm in diameter, the tube length is 800 mm, and the temperature inside the reactor is 410° C. The obtained thermal cracking product is quickly cooled to 40° C. to remove isobutyric anhydride and isobutyric acid in the system, and a gas rich in dimethyl ketone (DMK) is obtained. After online gas chromatography analysis, the DMK content in the gas phase is 9.53%.

[0057] Example 1

[0058] In this embodiment, the absorption solvent I is n-hexane, and the absorption solvent II is n-butyl acetate.

[0059] (1) using 100 mL of n-hexane at 0° C. to carry out absorption in step (1);

[0060] (2) The absorbed solution was stirred and reacted for 10 h under the conditions of 0.3 MPa and 0° C. The solution after the reaction was cooled to −10° C. and solid-liquid separation was performed to obtain a solid product I. The molecular weight of the solid product I was 950 as determined by GPC analysis.

[0061] (3) dissolving the solid product I in the solvent II to prepare 0.5 wt % of the absorption solvent III;

[0062] (4) 300 mL of absorption solvent III was used to absorb the gas rich in dimethyl ketone (DMK) at a temperature of -10°C. The concentration change of DMK in the absorption solvent is shown in Table 1. It can be seen that the equilibrium concentration of DMK after absorption can reach 31.98 wt%.

[0063] Table 1

[0064]

[0065] (5) The absorption solution was then subjected to a cyclization reaction at 130° C. and 1 MPa for 3 h, and the TMCB yield in this process reached 99.8%.

[0066] Comparative Example 1

[0067] In this comparative example, the absorption solvent used is n-butyl acetate, and there is no step (1) to step (3). 300 mL of the absorption solvent is directly used to carry out the absorption in step (4) at a temperature of -10°C. The concentration change of DMK in the absorption solvent is shown in Table 2. It can be seen that the equilibrium concentration of DMK after absorption is 16.93 wt%.

[0068] Table 2

[0069]

[0070] The absorption solution was subjected to cyclization reaction at 130° C. and 1 MPa for 3 h. The TMCB yield in this process was only 80.3%, and a large amount of β-lactone cyclized product formed by DMK cyclization was detected in the system.

[0071] Comparative Example 2

[0072] In this comparative example, the absorption solvent is an n-butyl acetate solution containing 0.5 wt% tetramethylcyclobutanedione TMCB, and there is no step (1) to step (3). 300 mL of the absorption solvent is directly used to carry out step (4) absorption at a temperature of -10°C. The concentration change of DMK in the absorption solvent is shown in Table 3. It can be seen that the equilibrium concentration of DMK after absorption is 22.31 wt%.

[0073] Table 3

[0074]

[0075] The absorption solution was subjected to cyclization reaction at 130° C. and 1 MPa for 3 h. The TMCB yield in this process was only 97.1%, and a trace amount of DMK oligomers was present in the system.

[0076] Example 2

[0077] In this embodiment, the absorption solvent I is isobutyl isobutyrate, and the absorption solvent II is n-pentyl acetate.

[0078] (1) using 100 mL of isobutyl isobutyrate to carry out absorption in step (1) at a temperature of 10° C.;

[0079] (2) The absorbed solution was stirred and reacted for 8 h under the conditions of 1.0 MPa and 10° C. The solution after the reaction was cooled to −20° C. and solid-liquid separation was performed to obtain a solid product I. The molecular weight of the solid product I was 600 as determined by GPC analysis.

[0080] (3) dissolving the solid product I in the solvent II to prepare 1.0 wt% of the absorption solvent III;

[0081] (4) 300 mL of absorption solvent III was used to absorb the gas rich in dimethyl ketone (DMK) at a temperature of -15°C. The concentration change of DMK in the absorption solvent is shown in Table 4. It can be seen that the equilibrium concentration of DMK after absorption can reach 32.87 wt%.

[0082] Table 4

[0083]

[0084] (5) The absorption solution was then subjected to a cyclization reaction at 120° C. and 0.5 MPa for 2 h. The TMCB yield in this process reached 99.5%.

[0085] Example 3

[0086] In this embodiment, the absorption solvent I is isobutyric anhydride, and the absorption solvent II is propionic isobutyric anhydride.

[0087] (1) using 100 mL of isobutyric anhydride at a temperature of -15°C to carry out the absorption in step (1);

[0088] (2) The absorbed solution was stirred and reacted for 10 h at 1.5 MPa and -50°C. The solution after the reaction was maintained at -50°C and solid-liquid separation was performed to obtain a solid product I. The molecular weight of the solid product I was 980 as determined by GPC analysis.

[0089] (3) dissolving the solid product I in the solvent II to prepare 0.3 wt % of the absorption solvent III;

[0090] (4) 300 mL of absorption solvent III was used to absorb the gas rich in dimethyl ketone (DMK) at a temperature of -20°C. The concentration change of DMK in the absorption solvent is shown in Table 5. It can be seen that the equilibrium concentration of DMK after absorption can reach 33.81 wt%.

[0091] Table 5

[0092]

[0093] (5) The absorption solution was then subjected to a cyclization reaction at 100° C. and 0.5 MPa for 5 h. The TMCB yield in this process reached 99.1%.

[0094] Example 4

[0095] In this embodiment, the absorption solvent I is n-hexane, and the absorption solvent II is n-butyl acetate.

[0096] (1) using 100 mL of n-hexane at 0° C. to carry out absorption in step (1);

[0097] (2) The absorbed solution was stirred and reacted for 10 h under the conditions of 4 MPa and 0° C. The solution after the reaction was cooled to −10° C. and solid-liquid separation was performed to obtain a solid product I. The molecular weight of the solid product I was 1400 as determined by GPC analysis.

[0098] (3) dissolving the solid product I in the solvent II to prepare 0.5 wt % of the absorption solvent III;

[0099] (4) 300 mL of absorption solvent III was used to absorb the gas rich in dimethyl ketone (DMK) at a temperature of -10°C. The concentration change of DMK in the absorption solvent is shown in Table 6. It can be seen that the equilibrium concentration of DMK after absorption can reach 29.13 wt%.

[0100] Table 6

[0101]

[0102] (5) The absorption solution was then subjected to a cyclization reaction at 130° C. and 1 MPa for 3 h, and the TMCB yield in this process reached 98.9%.

[0103] Example 5

[0104] The method of Example 1 is followed, except that in step (3), the solid product I is dissolved in solvent II to prepare 0.05 wt % of absorption solvent III; the other conditions are the same.

[0105] The absorption results are shown in Table 7 below. The TMCB yield is 98.54%.

[0106] Table 7

[0107]

[0108] Example 6

[0109] The method of Example 1 is followed, except that in step (3), the solid product I is dissolved in solvent II to prepare 1.2 wt % of absorption solvent III, and insoluble matter is present; the other conditions are the same.

[0110] The absorption results are shown in Table 8 below. The TMCB yield is 98.19%.

[0111] Table 8

[0112]

[0113]

[0114] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing tetramethylcyclobutanedione, characterized in that: The method comprises the following steps: (1) absorbing gas rich in dimethyl ketone (DMK) by a first absorbent to obtain a first absorption solution; (2) subjecting the first absorption solution to a polymerization reaction, and precipitating a solid product after cooling; (3) dissolving the solid product in the second absorbent to prepare a third absorbent; (4) absorbing the gas rich in dimethyl ketone (DMK) through a third absorbent to obtain a second absorption solution; (5) subjecting the second absorption solution to a cyclization reaction to obtain a solution containing tetramethylcyclobutanedione (TMCB).

2. The method according to claim 1, wherein: In step (1) and step (3), the first absorbent and the second absorbent are each selected from any one or more of fatty acid alkyl esters, fatty acid anhydrides, and alkanes; The structure of the fatty acid alkyl ester is as shown in formula (I): Wherein, R1 is H or an alkyl group having 1 to 6 carbon atoms, and R2 is an alkyl group having 1 to 6 carbon atoms; Preferably, the fatty acid alkyl ester is one or more of n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, n-butyl propionate, n-butyl butyrate, ethyl isobutyrate, propyl isobutyrate, and isobutyl isobutyrate; The structure of the fatty acid anhydride is as shown in formula (II): Wherein, R3 and R4 are H, alkyl with 1 to 6 carbon atoms; Preferably, the fatty acid anhydride is one or more of isobutyric anhydride, acetic isobutyric anhydride, acetic anhydride, propionic anhydride, and propionic isobutyric anhydride; The alkane is a C6-10 alkane; Preferably, the alkane is one or more of n-hexane, n-heptane, 2-methylheptane and n-octane.

3. The method according to claim 2, wherein: The second absorbent is selected from one or more of n-butyl acetate, n-pentyl acetate, and propionic acid isobutyric anhydride; and / or The first absorbent is selected from one or more of n-hexane, isobutyl isobutyrate, and isobutyric anhydride.

4. The method according to any one of claims 1 to 3, wherein: The absorption conditions of step (1) and step (4) each include: The temperature is -30°C to 30°C, preferably -20°C to 10°C; Preferably, The absorption conditions in step (1) include a temperature of -15°C to 10°C; and / or The absorption conditions of step (4) include: a temperature of -20°C to -10°C.

5. The method according to any one of claims 1 to 4, wherein: The polymerization reaction conditions of step (2) include: The reaction pressure is 0.1 to 10 MPa, preferably 0.1 to 5 MPa, and more preferably 0.3 to 1.5 MPa; and / or The temperature is -100°C to 20°C, preferably -80°C to 10°C, more preferably -50°C to 10°C; and / or The reaction time is 2 to 20 hours, preferably 4 to 15 hours, and more preferably 8 to 10 hours.

6. The method according to any one of claims 1 to 5, wherein: In step (2), The cooling end point temperature is -50°C to 10°C, preferably -50°C to -10°C; and / or The molecular weight of the solid product is 300-1500, preferably 300-1000, more preferably 600-980.

7. The method according to any one of claims 1 to 6, wherein: The concentration of the solid product in the third absorption solvent is 0.1 to 3 wt %, preferably 0.1 to 1 wt %.

8. The method according to any one of claims 1 to 7, wherein: The conditions for the cyclization reaction in step (5) include: The pressure is 0.1 to 5 MPa, preferably 0.1 to 3 MPa, more preferably 0.5 to 1 MPa; and / or The temperature is 80 to 180°C, preferably 100 to 160°C, more preferably 100 to 130°C; and / or The time is 0.5 to 6 hours, preferably 1 to 5 hours, and more preferably 2 to 5 hours.

9. The method according to any one of claims 1 to 8, wherein: The dimethyl ketene-rich gas is obtained by thermal cracking of isobutyric acid and / or isobutyric anhydride, cooling the system, and removing isobutyric acid and / or isobutyric anhydride.

10. The method according to any one of claims 1 to 9, wherein: The volume content of dimethyl ketene in the dimethyl ketene-rich gas is 5 to 90%; Preferably, the dimethyl ketene-rich gas contains 5 to 70 wt % of dimethyl ketene, and the remainder is inert gas.

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