Method for absorbing dimethyl ketene

Abstract

The invention discloses a method for absorbing dimethyl ketene. The method comprises the following steps: absorbing gas rich in dimethyl ketene through an absorbent; the absorbent comprises an absorption solvent and a dimethyl ketene oligomer dissolved in the absorption solvent. The method provided by the invention can overcome the defects of large solvent consumption and low absorption efficiency in the dimethyl ketene DMK absorption process in the prior art, and can significantly improve the concentration of DMK in the solution after absorption.

Description

Technical Field

[0001] The invention relates to a method for absorbing dimethyl ketene. Background Art

[0002] Dimethyl ketone (DMK) is an important member of the ketene class of substances. Due to its carbon-carbon double bond and carbon-oxygen double bond being directly connected, it is extremely active and can only stably exist in solution for about 5 hours at low temperatures. On the other hand, DMK is also a key intermediate for the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione (TMCB). The obtained TMCB can be hydrogenated to obtain the high value-added polyester monomer 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO).

[0003] The commonly used method for capturing DMK in industry is the solution absorption method. However, this method has the following problems: (1) DMK has low solubility in ester absorption solvents. The reported DMK concentration after absorption in ester solvents is all below 20 wt%, resulting in a huge amount of solvent used in the absorption process. (2) Although the selectivity of the dimerization process has been reported to be as high as 99%, in actual processes, the absorbed DMK is prone to side reactions during the dimerization process, and the yield is generally between 80% and 99%. In addition, certain trace impurities generated during the dimerization process will affect the catalyst activity in the subsequent TMCB hydrogenation process to prepare CBDO. Summary of the invention

[0004] In order to solve the above two problems, the purpose of the present invention is to overcome the defects of the prior art in the absorption process of dimethyl vinyl ketone (DMK), such as large amount of solvent used and low absorption efficiency, and to provide a method for absorbing dimethyl vinyl ketone, which can significantly increase the concentration of DMK in the solution after absorption.

[0005] In order to achieve the above object, the present invention provides a method for absorbing dimethyl ketene, which comprises: absorbing a gas rich in dimethyl ketene through an absorbent; the absorbent comprises an absorption solvent and a dimethyl ketene oligomer dissolved in the absorption solvent.

[0006] 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. DETAILED DESCRIPTION

[0007] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0008] The present invention provides a method for absorbing dimethyl ketone, which comprises: absorbing a gas rich in dimethyl ketone through an absorbent; the absorbent comprises an absorption solvent and a dimethyl ketone oligomer dissolved in the absorption solvent. The method of the present invention can overcome the defects of the prior art in the absorption process of dimethyl ketone (DMK), such as large amount of solvent used and low absorption efficiency, and can significantly increase the concentration of DMK in the solution after absorption.

[0009] In the present invention, the absorbent can achieve the purpose of the present invention, and there is no special requirement for the specific composition of the absorbent, which can be determined according to the concentration of dimethyl ketene in the raw material; according to a preferred embodiment of the present invention, in the absorbent, the concentration of dimethyl ketene oligomer 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%. Thereby, the absorption efficiency can be further improved and the concentration of DMK in the solution after absorption can be increased.

[0010] In the present invention, there is no special requirement for the absorption conditions. According to a preferred embodiment of the present invention, the absorption conditions include: a temperature of -30°C to 30°C, preferably -20°C to 10°C, for example, -20°C, -10°C, 0°C, 10°C. This can further improve the absorption efficiency and the concentration of DMK in the solution after absorption.

[0011] In the present invention, all dimethyl ketene oligomers can be used in the present invention, for example, can be selected from one or more of dimethyl ketene carbon-carbon double bond addition homopolymers, dimethyl ketene carbon-oxygen double bond addition homopolymers, dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition block copolymers.

[0012] In the present invention, the dimethyl ketene oligomer is preferably selected from a homopolymer of dimethyl ketene carbon-carbon double bond addition and / or a block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition.

[0013] According to a preferred embodiment of the present invention, preferably, the dimethyl ketene oligomer is a block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition, thereby further improving the absorption efficiency and the concentration of DMK in the solution after absorption.

[0014] In the present invention, there is no special requirement for the molecular weight of the dimethyl ketene oligomer. For the present invention, the number average molecular weight of the dimethyl ketene oligomer is preferably 300-1500, preferably 400-1300, for example, 400, 420, 450, 500, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, etc., but the present invention is not limited thereto. The molecular weight is determined by GPC.

[0015] In the present invention, the optional range of the absorption solvent is relatively wide, and the absorption solvent types commonly used in the art can be used in the present invention. For the present invention, the absorption solvent is preferably selected from any one or more of fatty acid alkyl esters, fatty acid anhydrides, and alkanes.

[0016] 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.

[0017] According to one embodiment of the present invention, the structure of the fatty acid alkyl ester is as follows:

[0018]

[0019] 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;

[0020] 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.

[0021] According to one embodiment of the present invention, the structure of the fatty acid anhydride is as shown in formula (II):

[0022]

[0023] Wherein, R3 and R4 are H, alkyl with 1-6 carbon atoms;

[0024] Preferably, the fatty acid anhydride is one or more of isobutyric anhydride, acetic isobutyric anhydride, acetic anhydride, propionic anhydride, and propionic isobutyric anhydride.

[0025] 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.

[0026] 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.

[0027] 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%.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] According to one embodiment of the present invention, the pressure is 1 kPa to 0.3 MPa, preferably 10 kPa to 0.1 MPa.

[0033] According to one embodiment of the present invention, the residence time is 0.1 to 4 s, preferably 0.1 to 1 s.

[0034] According to one embodiment of the present invention, a dilution gas is introduced during thermal cracking.

[0035] 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.

[0036] 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).

[0037] According to one embodiment of the present invention, the dilution gas is selected from inert gases, preferably nitrogen.

[0038] In the following examples, the DMK-rich gas 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 material is a quartz tube, the size is a diameter of 15 mm, the tube length is 800 mm, and the temperature in 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%.

[0039] The structural formula of DMK is:

[0040] The DMK concentration in the solution was calculated by chromatographic analysis of the test substance content, and the equilibrium concentration of DMK after absorption was calculated as: DMK mass in the solution / total mass of the absorption solution.

[0041] In the present invention, the homopolymer prepared by addition of dimethyl ketene carbon-carbon double bonds has a structural formula as shown below: n>4;

[0042] In the present invention, the homopolymer prepared by addition of carbon and oxygen double bonds of dimethyl ketene has a structural formula as shown below: n>4;

[0043] In the present invention, the block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition contains at least part of the following units in its molecular chain segments:

[0044] Example 1

[0045] The additive used in this embodiment is a homopolymer prepared by the addition of carbon-carbon double bonds of dimethyl ketene, and its molecular weight is 1050. The main absorption solvent is n-butyl acetate, and the mass content of DMK homopolymer in the absorbent is 0.5wt%.

[0046] 300 mL of the absorption solution was used to absorb 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%.

[0047] Table 1

[0048]

[0049] Example 2

[0050] The additive used in this embodiment is a block copolymer prepared by addition of carbon-carbon double bonds and carbon-oxygen double bonds of dimethyl ketone, and its molecular weight is 420. The main absorption solvent is n-butyl acetate, and the mass content of DMK homopolymer in the absorbent is 0.5wt%.

[0051] 300 mL of the above absorption solution was used to absorb DMK 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 can reach 36.51 wt%.

[0052] Table 2

[0053]

[0054] Comparative Example 1

[0055] In this comparative example, only n-butyl acetate was used as the absorption solvent. 300 mL of the above absorption solution was used to absorb DMK 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 only 16.93 wt%.

[0056] Table 3

[0057]

[0058] Comparative Example 2

[0059] This comparative example uses a butyl acetate solution containing 0.5 wt% tetramethylcyclobutanedione TMCB as the absorption solvent. 300 mL of the above absorption solution is used to absorb DMK at a temperature of -10°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 is only 22.31 wt%.

[0060] Table 4

[0061]

[0062] Example 3

[0063] The additive used in this embodiment is a homopolymer prepared by the addition of carbon-carbon double bonds of dimethyl ketone, and its molecular weight is 600. The main absorption solvent is n-butyl acetate, and the mass content of DMK homopolymer in the absorbent is 0.9wt%.

[0064] 300 mL of the absorption solution was used to absorb 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 33.08 wt%.

[0065] Table 5

[0066]

[0067] Example 4

[0068] The additive used in this embodiment is a homopolymer prepared by the addition of carbon-carbon double bonds of dimethyl ketene, and its molecular weight is 600. The main absorption solvent is n-butyl acetate, and the mass content of the DMK homopolymer in the absorbent is 1.2wt%.

[0069] 300 mL of the absorption solution was used to absorb 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 28.24 wt%.

[0070] Table 6

[0071]

[0072]

[0073] Example 5

[0074] The additive used in this embodiment is a homopolymer prepared by the addition of carbon-carbon double bonds of dimethyl ketene, and its molecular weight is 600. The main absorption solvent is n-butyl acetate, and the mass content of the DMK homopolymer in the absorbent is 0.05wt%.

[0075] 300 mL of the absorption solution was used to absorb 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 19.48 wt%.

[0076] Table 7

[0077]

[0078] Example 6

[0079] The method of Example 1 was followed, except that the oligomer was a homopolymer of dimethyl ketene carbon-oxygen double bond addition, and the other conditions were the same. The DMK absorption results are shown in Table 8.

[0080] Table 8

[0081]

[0082] Example 7

[0083] The method of Example 1 was followed, except that the oligomer was a block copolymer of dimethyl ketone carbon-carbon double bond addition and carbon-oxygen double bond addition, and the other conditions were the same. The DMK absorption results are shown in Table 9.

[0084] Table 9

[0085]

[0086] Example 8

[0087] The method of Example 1 was followed, except that the molecular weight of the oligomer was 350. The other conditions were the same. The DMK absorption results are shown in Table 10.

[0088] Table 10

[0089]

[0090] Example 8

[0091] The method of Example 1 was followed, except that the main absorption solvent was isobutyric anhydride. The other conditions were the same. The DMK absorption results are shown in Table 10.

[0092] Table 10

[0093]

[0094] Example 9

[0095] The method of Example 1 was followed, except that the main absorption solvent was n-octane and the other conditions were the same. The DMK absorption results are shown in Table 11.

[0096] Table 11

[0097]

[0098] 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 specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, 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 absorbing dimethyl ketone, the method comprising: The gas rich in dimethyl ketene is absorbed by an absorbent; the absorbent comprises an absorption solvent and dimethyl ketene oligomers dissolved in the absorption solvent.

2. The method according to claim 1, wherein: In the absorbent, the concentration of dimethyl ketene oligomer is 0.1-3 wt %, preferably 0.1-1 wt %.

3. The method according to claim 1 or 2, wherein: The absorption conditions include: a temperature of -30°C to 30°C, preferably -20°C to 10°C.

4. The method according to any one of claims 1 to 3, wherein: The dimethyl ketene oligomer is selected from one or more of a homopolymer of dimethyl ketene carbon-carbon double bond addition, a homopolymer of dimethyl ketene carbon-oxygen double bond addition, and a block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition; Preferably, the dimethyl ketene oligomer is selected from a homopolymer of dimethyl ketene carbon-carbon double bond addition and / or a block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition; Preferably, the dimethyl ketene oligomer is a block copolymer of dimethyl ketene carbon-carbon double bond addition and carbon-oxygen double bond addition.

5. The method according to any one of claims 1 to 4, wherein: The number average molecular weight of the dimethyl ketene oligomer is 300-1500, preferably 400-1300.

6. The method according to any one of claims 1 to 5, wherein: The absorption solvent is 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 each H or an alkyl group having 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.

7. The method according to any one of claims 1 to 6, wherein: The volume content of dimethyl ketene in the dimethyl ketene-rich gas is 5-90%; Preferably, the dimethyl ketene-rich gas contains 5-70 wt % of dimethyl ketene, and the remainder is inert gas.

8. The method according to any one of claims 1 to 7, 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.

9. The method according to claim 8, wherein: The reaction conditions of the thermal cracking process include: a temperature of 350-650°C, preferably 350-550°C.

10. The method according to claim 8 or 9, wherein: A diluent gas is introduced during the thermal cracking, and 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); Preferably, the diluent gas is selected from inert gases, preferably nitrogen.

Images