A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione and its application

Abstract

This invention discloses a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione by absorbing dimethyl ketene and its application. The method includes the following steps: (1) absorbing a gas containing dimethyl ketene using an absorption solvent to obtain an absorption liquid; (2) subjecting the absorption liquid obtained in step (1) to a dimerization reaction to generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione. This invention achieves a selectivity and yield of over 99% for the dimerization of dimethyl ketene to 2,2,4,4-tetramethyl-1,3-cyclobutanedione by adding dimethyl ketene β-lactone dimer to the absorption solvent.

Description

Technical Field

[0001] This invention relates to the field of preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, and more specifically, to a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione by absorbing dimethyl ketene and its application. Background Technology

[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is an important monomer in the materials industry. Copolymerization with 1,4-cyclohexanediol (CHDM), terephthalic acid (PTA), and trace amounts of ethylene glycol (EG) yields CBDO-modified PCTG copolyesters. The key to CBDO production is obtaining 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB). Existing TMCB production routes use isobutyric anhydride as a base material, which is thermally cracked to produce dimethyl ketene (DMK), followed by quenching and dimerization to obtain the key intermediate 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB).

[0003] US Patent 5258556A discloses a method for absorbing dimethyl ketone (DMK), which involves adding approximately 0.2–5% of 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB) to the absorption solvent, while controlling the absorption temperature below 150°C. By adding a certain amount of TMCB, the solubility of DMK in the absorbent is increased, thereby increasing the DMK concentration in the absorbent. This results in reduced solvent consumption, lower energy consumption, and simplified subsequent processes.

[0004] Chinese patent CN 111875487A discloses a method for preparing tetramethylcyclobutanedione, comprising: 1) absorption: contacting dimethyl ketene gas phase with a liquid absorbent to obtain a dimethyl ketene solution; wherein the liquid absorbent is a fatty acid ester solution containing tetramethylcyclobutanedione; 2) dimerization reaction: heating the dimethyl ketene solution to induce a dimerization reaction to generate tetramethylcyclobutanedione; 3) solid-liquid separation: subjecting the product to multi-stage flash evaporation and cooling crystallization, and separating the slurry by solid-liquid separation to obtain crude tetramethylcyclobutanedione.

[0005] However, the addition of TMCB is known to those skilled in the art to affect the reaction rate and reaction equilibrium. The reaction rate of the dimerization process of DMK is reduced after the addition of TMCB. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a novel process for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione by absorption dimerization of dimethyl ketene. In this process, dimethyl ketene β-lactone dimer is added to the absorption solvent, resulting in a selectivity and yield of over 99% for the dimerization of dimethyl ketene to 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0007] One objective of this invention is to provide a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising the following steps:

[0008] (1) The gas containing dimethyl ketone is absorbed by an absorption solvent to obtain an absorption liquid;

[0009] (2) The absorbent obtained in step (1) is subjected to a dimerization reaction to generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0010] In the above scheme, the absorption solvent in step (1) includes fatty acid alkyl esters and dimethyl ketone β-lactone dimers.

[0011] In the above scheme, the content of dimethyl ketene β-lactone dimer in the absorption solvent in step (1) is 0.1-20 wt%, preferably 0.5-10 wt%, for example, it can be 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, etc. The remainder in the absorption solvent is fatty acid alkyl ester.

[0012] In the above scheme, the boiling point of the fatty acid alkyl ester in step (1) is higher than 75°C, and the fatty acid alkyl ester is preferably a C4-C12 fatty acid alkyl ester. Further, the boiling point of the fatty acid alkyl ester is higher than 100°C, and more preferably at least one of ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, n-butyl propionate, isobutyl propionate, n-butyl butyrate, propyl isobutyl isobutyl butyrate, and isobutyl isobutyl butyrate.

[0013] In the above scheme, the gas containing dimethyl ketone (DMK) in step (1) is a DMK-rich gas, including products of DMK processes prepared by any method known to researchers in the art, including but not limited to products of various processes such as thermal cracking of isobutyric acid or isobutyric anhydride, dehydrohalogenation of isobutyryl chloride or isobutyryl bromide, and thermal cracking reaction of malonic acid derivatives.

[0014] In the above scheme, the absorption temperature in step (1) is -20 to 100°C, preferably -10 to 50°C, for example, it can be -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc.

[0015] In the above scheme, the concentration of dimethyl ketone in the absorbent liquid after absorption in step (1) is less than 50 wt%, preferably 10 to 30 wt%, for example, 10 wt%, 20 wt%, 30 wt%, 35 wt%, 40 wt%, etc.

[0016] In the above scheme, the dimerization reaction in step (2) can be carried out using a process known to researchers in the art. The dimerization reaction temperature is preferably 0 to 120°C, more preferably 10 to 100°C. The dimerization reaction time is preferably 0.5 to 10 h, more preferably 1 to 5 h.

[0017] In the above scheme, step (2) may also include a purification step of 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The purification step may employ processes known to researchers in the art, preferably including methods such as evaporation crystallization and / or cooling crystallization.

[0018] According to a preferred embodiment of the present invention, the method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione by absorbing dimethyl ketene (DMK) and dimerizing it includes the following steps:

[0019] (1) The DMK-rich gas is absorbed using an absorption solvent;

[0020] (2) The absorbent obtained in step (1) is transferred into a dimerization reactor to dimerize and generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0021] A second objective of this invention is to provide the application of the method in the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione from dimethyl ketene.

[0022] This invention provides a novel process for the absorption dimerization of dimethyl ketene to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The selectivity and yield of 2,2,4,4-tetramethyl-1,3-cyclobutanedione can both reach over 99%, which is a highly selective synthetic method for 2,2,4,4-tetramethyl-1,3-cyclobutanedione.

[0023] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0024] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0025] In the context of this specification, except where expressly stated, any matters or issues not mentioned herein shall apply directly to those known in the art without any modification. Furthermore, any implementation described herein may be freely combined with one or more other implementations described herein, and any resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be clearly unreasonable.

[0026] The present invention will be further illustrated below through examples. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0028] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0029] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0030] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0031] The dimethyl ketone (DMK) used in the embodiments of this invention is obtained by thermal cracking of isobutyric anhydride, and the specific method of obtaining it is as follows:

[0032] Isobutyric anhydride was introduced into the vaporizer at a rate of 0.2 mL / min at a temperature of 300°C. Nitrogen gas, at a flow rate of 0.6 L / min and a preheating temperature of 300°C, was used as the dilution gas. After preheating, the dilution gas was mixed with the vaporized isobutyric anhydride and introduced into the pyrolysis tube for reaction. The residence time in the pyrolysis tube reactor was controlled at 0.5 s, and the temperature was maintained at 400°C. The product at the outlet of the pyrolysis tube was rapidly cooled to 40°C, and isobutyric acid and isobutyric anhydride were removed from the system, yielding a DMK-rich gas.

[0033] Example 1

[0034] In Example 1, the absorption solvent was a mixed solution of n-amyl acetate and dimethyl ketene β-lactone dimer, wherein the concentration of dimethyl ketene β-lactone dimer was 5 wt%, the amount of the mixed solution was 200 g, and the absorption temperature was 30 °C. A DMK-rich gas was passed into the absorption solvent. The absorption efficiency was calculated as the recovery rate of DMK in the gas before and after absorption after 1 hour of system operation, which was 83.57%. After 4 hours of system operation, the DMK concentration in the absorbent was analyzed by gas chromatography, and the value was 15.34%.

[0035] The absorbed solution was subjected to a dimerization reaction at 80°C for 5 hours. The selectivity of TMCB during the reaction was 99.5%, and the yield of TMCB in the system was 99.37%.

[0036] Example 2

[0037] The method is the same as in Example 1, except that the absorption temperature is changed to 20°C.

[0038] Example 3

[0039] The method is the same as in Example 1, except that the absorption temperature is changed to 10°C.

[0040] Example 4

[0041] The method is the same as in Example 1, except that the absorption temperature is changed to 0°C.

[0042] Example 5

[0043] The method is the same as in Example 1, except that the absorption temperature is changed to -10°C.

[0044] Examples 2-5 involve changing the absorption temperature under the conditions of Example 1, and the results are shown in Table 1.

[0045] Table 1

[0046]

[0047] Example 6

[0048] In this embodiment, the absorption solvent is a mixed solution of isopropyl acetate and dimethyl ketene β-lactone dimer, wherein the concentration of dimethyl ketene β-lactone dimer is 1 wt%, the amount of the mixed solution is 200 g, and the absorption temperature is 0 °C. A gas rich in DMK is passed into the above-mentioned absorption solvent. The absorption efficiency is calculated based on the recovery rate of DMK in the gas before and after absorption after 1 hour of system operation, which is 97.30%. After 4 hours of system operation, the concentration of DMK in the absorbent is analyzed by gas chromatography, and the value is 23.11%.

[0049] The absorbed solution was subjected to a dimerization reaction at 80°C for 5 hours. The selectivity of TMCB during the reaction was 99.9%, and the yield of TMCB in the system was 99.83%.

[0050] Example 7

[0051] The method is the same as in Example 6, except that the content of dimethyl ketene β-lactone dimer in the absorption solvent is changed to 0.5 wt%.

[0052] Example 8

[0053] The method is the same as in Example 6, except that the content of dimethyl ketene β-lactone dimer in the absorption solvent is changed to 3 wt%.

[0054] Example 9

[0055] Same as in Example 6, except that the content of dimethyl ketene β-lactone dimer in the absorption solvent is changed to 7 wt%.

[0056] Example 10

[0057] Same as in Example 6, except that the content of dimethyl ketene β-lactone dimer in the absorption solvent is changed to 10 wt%.

[0058] Examples 7-10 are based on Example 6, but with different contents of dimethyl ketene β-lactone dimer in the absorption solvent. The results are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 11

[0062] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with n-butyl acetate.

[0063] Example 12

[0064] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with ethyl acetate.

[0065] Example 13

[0066] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with isobutyl acetate.

[0067] Example 14

[0068] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with isobutyl propionate.

[0069] Example 15

[0070] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with propyl isobutyrate.

[0071] Example 16

[0072] The method is the same as in Example 6, except that isopropyl acetate in the absorption solvent is replaced with isobutyl isobutyrate.

[0073] Examples 11-16 are based on Example 6, but with different types of absorbent solvents (keeping the content of dimethyl ketene β-lactone dimer at 3%), and the results are shown in Table 3.

[0074] Table 3

[0075]

[0076] Comparative Example 1

[0077] In this comparative example, the absorption solvent was n-amyl acetate, with a dosage of 200 g, and the absorption temperature was 30 °C. A DMK-rich gas was passed into the absorption solvent. After the system ran for 4 hours, the DMK concentration in the absorbent was analyzed by gas chromatography. The absorption process was based on the amount of DMK in the gas. After absorption, the DMK concentration in the absorbent was 15.89%.

[0078] The absorbed solution was subjected to a dimerization reaction at 80°C for 5 hours. The selectivity of TMCB in the dimerization process was 93.3%, and the yield of TMCB in the system was 90.55%.

[0079] Comparative Example 2

[0080] This comparative example is compared with Example 6. The absorption solvent in this comparative example is a mixed solution of isopropyl acetate and 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB), wherein the concentration of TMCB is 1 wt%, the volume of the mixed solution is 200 g, and the absorption temperature is 0 °C. A DMK-rich gas was passed into the above-mentioned absorption solvent. The absorption efficiency was calculated as the recovery rate of DMK in the gas before and after absorption after 1 hour of system operation, which was 97.28%. After 4 hours of system operation, the DMK concentration in the absorbent was analyzed by gas chromatography, and the value was 23.59%.

[0081] The absorbed solution was subjected to a dimerization reaction at 80°C for 5 hours. The selectivity of TMCB in the dimerization process was 93.0%, and the yield of TMCB in the system was 89.73%.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, comprising the following steps: (1) The gas containing dimethyl ketone is absorbed by an absorption solvent to obtain an absorption liquid; (2) The absorbent obtained in step (1) is subjected to a dimerization reaction to generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione; The absorbent solvent includes fatty acid alkyl esters and dimethyl ketene β-lactone dimers, wherein the fatty acid alkyl esters are C4-C12 fatty acid alkyl esters.

2. The method according to claim 1, characterized in that: The boiling point of the fatty acid alkyl ester is above 75°C.

3. The method according to claim 1, characterized in that: The fatty acid alkyl ester is selected from at least one of ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, n-butyl propionate, isobutyl propionate, n-butyl butyrate, propyl isobutyl butyrate, and isobutyl isobutyl butyrate.

4. The method according to claim 1, characterized in that: The content of dimethyl ketene β-lactone dimer in the absorbent solvent is 0.1–20 wt%.

5. The method according to claim 4, characterized in that: The content of dimethyl ketene β-lactone dimer in the absorbent solvent is 0.5-10 wt%.

6. The method according to claim 1, characterized in that: The gas containing dimethyl ketone originates from the thermal decomposition products of isobutyric acid or isobutyric anhydride, the dehydrohalogenation products of isobutyryl chloride or isobutyryl bromide, and the thermal decomposition products of malonic acid derivatives.

7. The method of claim 1, wherein In step (1): The absorption temperature is -20 to 100°C; and / or, The concentration of dimethyl ketene in the absorbent is less than 50 wt%.

8. The method of claim 7, wherein In step (1): The absorption temperature is -10 to 50°C; and / or, The concentration of dimethyl ketene in the absorbent is 10–30 wt%.

9. The method of claim 1, wherein In step (2): The dimerization reaction is carried out at a temperature of 0–120°C; and / or, The dimerization reaction takes 0.5 to 10 hours.

10. The method of claim 9, wherein In step (2): The dimerization reaction is carried out at a temperature of 10–100°C; and / or, The dimerization reaction takes 1 to 5 hours.

11. The method according to claim 1, characterized in that: Step (2) includes a purification step of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, which includes evaporation crystallization and / or cooling crystallization.

12. Use of the method according to any one of claims 1 to 11 in the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione from dimethyl ketene.

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