A process for the preparation of laurolactam from cyclododecanone oxime

Abstract

The application discloses a method for preparing dodecanolactam from cyclododecanone oxime, wherein the cyclododecanone oxime raw material is diluted, mixed with fluorocarbon auxiliary agent, preheated, and then reacted in a microchannel after passing through a dynamic mixer and entering the microchannel, and the reaction liquid is separated into dodecanolactam product after neutralization and water washing; the method can effectively enhance reaction conversion rate and selectivity, improve stability and safety of device operation, and improve product quality.

Description

TECHNICAL FIELD

[0001] The application discloses a method for preparing dodecanolactam from cyclododecanone oxime and belongs to the field of organic synthesis. BACKGROUND

[0002] Dodecanolactam is an important monomer for producing nylon 12, which is usually prepared from cyclododecanone through oximation and rearrangement reaction, and a reaction equation is shown as follows:

[0003]

[0004] The rearrangement reaction of cyclododecanone oxime belongs to a typical Beckmann rearrangement reaction, and cyclododecanone oxime is subjected to rearrangement reaction under the action of concentrated sulfuric acid or fuming sulfuric acid catalyst, the conversion rate is extremely high, dodecanolactam is rapidly generated, meanwhile, the concentrated acid can rapidly absorb water in the system to avoid side reactions, and a reaction mechanism is shown as follows:

[0005]

[0006] In the rearrangement reaction of cyclododecanone oxime, the concentrated acid has extremely strong dehydration property, can cause the system to have more side reactions, and a large amount of carbonization can occur in severe cases, so that the reaction residence time and temperature need to be accurately controlled. The concentrated acid and the ketone oxime raw material are high-viscosity fluids with poor fluidity, and cyclododecanone oxime is generated in an organic solvent system, while the concentrated acid is generated in an aqueous system, so that the two-phase reaction increases the mixing difficulty of the system, and strong stirring of the system is usually required. A large amount of reaction heat is released in the rearrangement reaction process, local overheating is easily caused, production hazards are easily caused, and the concentration distribution of substances in the system is uneven, so that the conversion rate and selectivity of the reaction are affected. Current main heat removal methods in engineering include external circulation condenser heat removal and solvent evaporation heat removal, but the above methods cannot solve the problem of uneven concentration and temperature distribution in the rearrangement reaction process, and it is also difficult to control the occurrence of side reactions in the reaction, so that the selectivity is low.

[0007] A short process continuous preparation system and method of dodecanolactam is described in patent CN113769683, which uses a supergravity reactor to couple rectification, neutralization, and phase separation processes for rearrangement reaction. However, the system involves rearrangement reaction, neutralization, and phase separation operations, which are difficult to achieve continuous production in engineering, and the problem of multiple side reactions in rearrangement reaction has not been solved. Patent CN109867616 mentions the use of composite stirring form of push paddle and emulsification paddle for rearrangement reaction to enhance mass transfer effect, but due to the need for high-speed operation of the stirring at full frequency, it is prone to damage, and there is no control measure for the side reactions in the rearrangement reaction. The content of rearranged carbide is high after the reaction of the invention, which is difficult to separate in the subsequent system. Patent CN115260073 mentions the replacement of concentrated sulfuric acid or oleum with 65-98% sulfuric acid. On the one hand, the reduction of acid concentration is not conducive to the occurrence of rearrangement reaction, and the production efficiency and reaction selectivity are limited. On the other hand, the corrosion problem of the equipment is particularly serious, and the equipment material needs to be upgraded. Even the HC material cannot be used for a long time, and the materials such as enamel glass are easily broken, which greatly increases the production cost.

[0008] In summary, there is an urgent need to develop a more efficient and more environmentally friendly dodecanolactam preparation method to solve the problems of low efficiency, low safety, multiple side reactions, large heat release, strong corrosion, etc. in dodecanolactam production. SUMMARY

[0009] In view of the above problems existing in the prior art, the present application aims to provide a method for preparing dodecanolactam from cyclododecanone oxime, which has good mass transfer and heat transfer effect, and can promote the Beckmann rearrangement reaction to proceed quickly by adding an additive, while reducing the residence time and reducing the generation of side reactions, thereby effectively improving the product quality.

[0010] A method for preparing dodecanolactam from cyclododecanone oxime, comprising the following steps:

[0011] (1) mixing cyclododecanone oxime with an organic solvent, and adding an additive to the above solution to form a continuous organic phase solution; and using a concentrated sulfuric acid solution as a continuous aqueous phase solution;

[0012] (2) mixing the above continuous organic phase solution and continuous aqueous phase solution, and then performing reaction after mixing, so that the cyclododecanone oxime undergoes Beckmann rearrangement reaction under acid catalysis and is aged;

[0013] (3) neutralizing, washing, and separating the aged reaction liquid to obtain dodecanolactam.

[0014] In the present application, since concentrated sulfuric acid is used as the catalyst for Beckmann rearrangement, the selected solvent should not contain active groups, and the organic solvent is one or more than two of the following inert solvents: cyclohexane, methylcyclohexane, ethylcyclohexane, benzene, toluene, xylene, etc., preferably methylcyclohexane and ethylcyclohexane;

[0015] In the present application, the concentration of cyclododecanone oxime in the organic solvent solution is 5-20wt%.

[0016] In the present application, the concentrated sulfuric acid is concentrated sulfuric acid with a mass fraction of 95% or more, or fuming sulfuric acid, preferably 98% concentrated sulfuric acid;

[0017] In the present application, the additive is a fluorocarbon surfactant, which has the following structure:

[0018]

[0019] In the present application, R1 is a long-chain fluorocarbon nonpolar group, preferably a fluorocarbon chain with a carbon atom number of 6-12, and R2 is a polar group such as sulfonic acid group, nitric acid group, formic acid group, etc., preferably sulfonic acid group as a substituent;

[0020] In the present application, the amount of additive added is 0.1-1wt% of the mass of cyclododecanone oxime.

[0021] In the present application, fluorocarbon surfactant is used as an additive, which has extremely high surface activity and can significantly reduce the surface tension of aqueous solution at very low application concentration. In addition, the fluorine-carbon bond of fluorocarbon surfactant is difficult to be broken due to its high bond energy. Moreover, fluorine atoms have a shielding effect on carbon-carbon bonds. Since the radius of fluorine atom is larger than that of hydrogen atom, the perfluorinated carbon-carbon bond can be effectively shielded and protected, reducing the possibility of carbon-carbon bond breakage, thus making the fluorocarbon chain more stable and not decomposing even in high temperature environment.

[0022] In the present application, the boiling point of long-chain fluorocarbon additive is relatively high, and it is discharged from the system as waste liquid in the form of heavy components in the rectification system, which has no effect on the product.

[0023] In the present application, the molar ratio of concentrated sulfuric acid to cyclododecanone oxime is 1.5-5, preferably 2-3.

[0024] In the present application, the temperature of the preheater is 40-160℃, preferably 60-100℃. The viscosity of concentrated sulfuric acid and cyclododecanone oxime solution is relatively large, resulting in poor flowability in pipeline transportation. Therefore, the present application reduces the viscosity of ketoxime by preparing a solution. Preferably, the continuous organic phase solution and the continuous aqueous phase solution are preheated before reaction, and the flowability of sulfuric acid and cyclododecanone oxime solution is improved by preheating, so as to enhance the transportation and mixing effect.

[0025] In the present application, the reaction of step (2) is carried out in a micro-channel reactor.

[0026] In the present application, the preheated continuous organic phase solution and the continuous aqueous phase solution are mixed by a dynamic mixer before the reaction, and the pre-mixing and micro-channel reaction can effectively solve the mass transfer and heat transfer problems of the rearrangement reaction, the residence time of the reaction liquid in the dynamic mixer is 30-90s, and the residence time in the micro-channel is 120-600s, preferably 180-300s.

[0027] After the reaction is completed, the above-mentioned matured reaction liquid is introduced into a neutralization system, a neutralizing agent is used for neutralization, and after neutralization, it is introduced into a water washing system, the organic phase after water washing is introduced into a product separation system, and the aqueous phase after neutralization and the aqueous phase after water washing are combined and introduced into a by-product separation system.

[0028] In the present application, the neutralizing agent is an alkali solution, preferably an alkali solution such as ammonia and sodium hydroxide, and the amount of the neutralizing agent added is 200%-500% of the molar amount of the acid, preferably 200%-300%;

[0029] In the present application, water washing is used for washing, and PW water is used for water washing, and the mass of the water added is 10%-200% of the mass of the oil phase, preferably 50%-100%;

[0030] In the present application, in order to avoid the occurrence of side reactions of the product catalyzed by concentrated sulfuric acid, the reaction liquid needs to be quenched in time, and the present application uses an alkali solution to neutralize the acid to quench the reaction, and the oil phase after neutralization is washed again, and the neutralization and water washing are carried out by using a rotating disc extraction column, the reaction liquid is added to the column kettle, and the water phase is added to the top of the column; the rotating disc extraction column has a height-diameter ratio of 5-10:1, three-blade stirring paddles are distributed in the column, the spacing is 100-150mm, and the stirring speed is 10-20rpm / min;

[0031] In the present application, since the solubility of lauryl lactam in the organic solvent is limited, the temperature of neutralization and water washing needs to be controlled above 60℃ to avoid the precipitation of lauryl lactam;

[0032] In the present application, the organic phase enters the product separation system and is separated by conventional rectification, the purity of the product is ≥99%, and the ethanol solubility color number is ≤10; the aqueous phase enters the by-product separation system and is obtained by conventional recrystallization; rectification and recrystallization are conventional processes, which can be realized by ordinary skilled personnel in the art according to the physical property data, and will not be described in detail in the present application.

[0033] Compared with the conventional technology, the present application has the following beneficial effects:

[0034] 1) The present application provides a method for preparing lauryl lactam from cyclododecanone oxime by micro-channel technology, which can improve the mass transfer and heat transfer effect of the reaction, and avoid the adverse effects caused by heat accumulation through the reaction form of micro-channel reactor;

[0035] 2) The present application strengthens the mixing of the oil phase and the concentrated sulfuric acid phase by adding fluorocarbon additives, has the characteristics of low dosage, high activity and good stability, can promote the Beckmann rearrangement reaction to proceed quickly, at the same time reduces the residence time and reduces the generation of side reactions, and can effectively improve the product quality;

[0036] 3) The present application selects the process conditions and solvents to ensure the fluidity of the materials and the solubility of the products, at the same time, improves the conversion rate of the raw materials, avoids the decomposition of the raw materials in the subsequent system, effectively improves the production efficiency, reduces the energy consumption, and greatly saves the production cost;

[0037] 4) In the present application, the reaction liquid is neutralized with lye, and the corresponding sulfate by-product is produced at the same time, which improves the overall added value of the device. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The process flow chart of Example 1 of the present application is as follows,

[0039] In the figure, 1 is a solvent, 2 is cyclododecanone oxime, 3 is an additive, 4 is an acid, 5 is lye, 6 is PW water, 7 is lauryl lactam, 8 is a sulfate, A1 is an organic phase, A2 is an acid phase, B1 / B2 is a preheater, C is a dynamic mixer, D is a micro-channel reactor, E is neutralization, F is water washing, G1 is rectification, and G2 is recrystallization. DETAILED DESCRIPTION

[0040] The present application will be further described below in conjunction with specific examples. It should be noted that these specific examples are only used as examples and should not be understood as limiting the scope of protection claimed by the present application.

[0041] The analysis test methods used in the following examples of the present application are as follows:

[0042] Gas phase analysis: Shimadzu 2010Plus; injection port temperature: 280℃; split ratio: 30:1; chromatographic column: DB-5(30m x 0.25mm x 0.25μm); temperature program: 50℃ for 2min, increased to 80℃ at 5℃ / min, kept for 10min, increased to 300℃ at 15℃ / min, kept for 10min; FID detector temperature: 300℃.

[0043] Colorimetric analysis: HACH LICO620 benchtop colorimeter, color value consistent with ASTM standard, measurement result consistent with ASTM standard.

[0044] The following embodiments of the present invention use information on the main sources of raw materials. Unless otherwise specified, all other raw materials are common commercially available materials:

[0045] Methylcyclohexane (99%), CAS: 108-87-2, Beijing Innocare Technology Co., Ltd.

[0046] Ethylcyclohexane (99%), CAS: 1678-91-7, Beijing Innocare Technology Co., Ltd.;

[0047] Benzene (AR), CAS: 71-43-2, Beijing Innocare Technology Co., Ltd.;

[0048] Toluene (99.85%), CAS: 108-88-3, Beijing Innocare Technology Co., Ltd.

[0049] Xylene (99%), CAS: 1330-20-7, Beijing Innocare Technology Co., Ltd.;

[0050] 4-Dodecylfluoroalkylbenzenesulfonic acid, CAS: 758683-30-6, Beijing Innocare Technology Co., Ltd.;

[0051] 3-Dodecylfluoroalkylbenzenesulfonic acid, CAS: 104748-19-8, Beijing Innocare Technology Co., Ltd.;

[0052] 4-Fluorohexylbenzenesulfonic acid, CAS: 712264-01-2, Beijing Innocare Technology Co., Ltd.;

[0053] 4-Dodecylbenzenesulfonic acid, CSA: 85536-14-7, Beijing Innocare Technology Co., Ltd.;

[0054] Fuming hydrochloric acid (37% aqueous solution), CAS: 7647-01-0, Beijing Innocare Technology Co., Ltd.;

[0055] Anhydrous ethanol (AR), CAS: 64-17-5, Beijing Innocare Technology Co., Ltd.;

[0056] Sodium hydroxide (32% solution), concentrated sulfuric acid (98%), ammonia (25%), cyclododecanone oxime, and PW pure water are produced in-house.

[0057] Example 1

[0058] The feed flow rate of cyclododecanone oxime was 19.73 g / h (0.1 mol / h), the feed flow rate of ethylcyclohexane solvent was 98.5 g / h, and the feed flow rate of 4-dodecylbenzenesulfonic acid auxiliary agent was 0.197 g / h, resulting in a mixed organic phase material A1. 98% concentrated sulfuric acid was fed at a flow rate of 29.42 g / h (0.3 mol / h) as the aqueous phase material A2. The temperature of preheaters B1 and B2 was both 100℃. Stream A1 (118.43 g / h), after preheating, was mixed with preheated stream A2 (29.42 g / h) in a dynamic mixer, with a residence time of 90 s. The mixed material was then fed into a microchannel reactor at a flow rate of 149.62 g / h, where it remained for 300 s. Reactions were sampled and tested, and the conversion rate was calculated to be 99.8%, with a dodecyl lactam selectivity of 99.6%. After the reaction, the material enters the neutralization extraction tower. The reaction solution is added through the bottom of the tower, and the alkali solution is added at the top of the tower. The extraction tower is 1200 mm high and 120 mm in diameter. Stirring is set every 150 mm in the tower at a speed of 20 rpm / min. The alkali solution is a 32% sodium hydroxide solution, and the addition flow rate is 112.50 g / h (NaOH: 0.9 mol / h). The temperature of the neutralization tower is controlled at 60℃. After mixing and phase separation, the oil phase at the top of the neutralization tower enters the bottom of the water washing tower. The parameters of the water washing tower are the same as those of the neutralization tower. The PW water addition rate at the top of the water washing tower is 118.4 g / h. The aqueous phase after washing is mixed with the aqueous phase at the bottom of the neutralization tower and enters the crystallization system. Sodium sulfate product is obtained by recrystallization. The oil phase enters the distillation system and obtains dodecyl lactam product by vacuum distillation. After gas chromatography analysis, the purity is 99.85%, and the product yield is calculated to be 98.77%. The color number of the ethanol solution is 4 Hazen.

[0059] Example 2

[0060] The feed flow rate of cyclododecanone oxime was 19.73 g / h (0.1 mol / h), the feed flow rate of methylcyclohexane solvent was 394.6 g / h, and the feed flow rate of 3-dodecylbenzenesulfonic acid auxiliary agent was 0.02 g / h, resulting in a mixed organic phase material A1. 98% concentrated sulfuric acid was fed at a flow rate of 19.61 g / h (0.2 mol / h) as the aqueous phase material A2. The temperatures of preheaters B1 and B2 were both 60℃. Stream A1 (414.35 g / h) was preheated and then mixed with preheated stream A2 (19.61 g / h) in a dynamic mixer, with a residence time of 30 s. The mixed material was then fed into a microchannel reactor at a flow rate of 433.96 g / h, with a residence time of 180 s. Reactions were sampled and tested, and the conversion rate was calculated to be 99.7%. The selectivity for dodecyl lactam was [not specified]. 99.4%; After the reaction, the material enters the neutralization extraction tower. The reaction solution is added through the bottom of the tower, and the alkali solution is added at the top of the tower. The extraction tower is 1200 mm high and 240 mm in diameter. Stirring is set every 100 mm in the tower at a speed of 10 rpm / min. The alkali solution is 25% ammonia water, and the addition flow rate is 56 g / h (NH3: 0.4 mol / h). The temperature of the neutralization tower is controlled at 80℃. After mixing and phase separation, the oil phase at the top of the neutralization tower enters the bottom of the water washing tower. The parameters of the water washing tower are the same as those of the neutralization tower. The PW water addition rate at the top of the tower is 207.2 g / h. After washing, the aqueous phase is mixed with the aqueous phase at the bottom of the neutralization tower and enters the crystallization system. The ammonium sulfate product is obtained by recrystallization. The oil phase enters the distillation system and the dodecyl lactam product is obtained by vacuum distillation. After gas chromatography analysis, the purity is 99.82%, and the product yield is calculated to be 98.74%. The color number of the ethanol solution is 5 Hazen.

[0061] Example 3

[0062] The method is the same as in Example 1, except that the added additive is 4-fluorohexylbenzenesulfonic acid, and the material flow rate and process conditions are the same. The reaction results are shown in the table below.

[0063] Comparative Example 1

[0064] The method of Example 1 is the same, except that the additive is replaced with an equivalent mass of solvent, that is, 0.197 g / h of ethylcyclohexane solvent is added. All other process parameters are the same. The reaction results are shown in the table below.

[0065] Comparative Example 2

[0066] The method of Example 1 is the same, except that the additive is replaced by an equal mass of dodecylbenzenesulfonic acid, that is, 0.197 g / h of dodecylbenzenesulfonic acid is added. All other process parameters are the same. The reaction results are shown in the table below.

[0067] Comparative Example 3

[0068] The method in Example 1 was followed, except that dilute sulfuric acid was used as the acid, 50% dilute sulfuric acid was prepared, and the amount of sulfuric acid added was 58.84 g / h (0.3 mol / h). All other process parameters were the same, and the reaction results are shown in the table below.

[0069] Table 1. Summary of Characterization Results of Examples and Comparative Examples

[0070]

[0071]

[0072] As can be seen from the above examples and comparative examples, the microchannel technology of the present invention for preparing dodecyl lactam from cyclododecanone oxime can reduce the viscosity of the material, improve the mixing effect of the reaction through engineering equipment such as dynamic mixers and microchannels, and further enhance the mixing effect of acid oxime by introducing stable and efficient fluorocarbon additives, thereby enhancing the conversion rate and selectivity of the reaction. At the same time, the microchannel reaction mode of the present invention reduces the residence time, avoids the phenomenon of large-scale carbonization in the reaction, and enhances the mass and heat transfer effect of the system, thereby improving production efficiency and process safety.

[0073] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing dodecanolactam from cyclododecanone oxime, characterized in that, Includes the following steps: (1) Mix cyclododecanone oxime with an organic solvent and add an auxiliary agent to the above solution to form a continuous organic phase solution; use concentrated sulfuric acid solution as a continuous aqueous phase solution; (2) The above continuous organic phase solution and continuous aqueous phase solution are mixed and reacted. Cyclododecone oxime undergoes Beckmann rearrangement under acid catalysis and is then ripened. The reaction in step (2) is carried out in a microchannel reactor. (3) The matured reaction solution is neutralized, washed, and separated to obtain dodecyl lactam; The aforementioned additive is a fluorocarbon surfactant with the following structure: Wherein, R1 is a long-chain fluoroalkyl nonpolar group, and R2 is a sulfonic acid group; The concentrated sulfuric acid mentioned is concentrated sulfuric acid or fuming sulfuric acid with a mass fraction of 95% or higher.

2. The preparation method according to claim 1, characterized in that, The organic solvent is one or more of cyclohexane, methylcyclohexane, ethylcyclohexane, benzene, toluene, and xylene.

3. The preparation method according to claim 2, characterized in that, The organic solvent is methylcyclohexane or ethylcyclohexane.

4. The preparation method according to claim 1, characterized in that, In organic solvent solutions of cyclododecanone oxime, cyclododecanone oxime solutions with a concentration of 5-20 wt% are prepared.

5. The preparation method according to claim 1, characterized in that, The concentrated sulfuric acid mentioned is 98% by mass.

6. The preparation method according to claim 1 or 2, characterized in that, In the aforementioned additive, R1 is a fluorocarbon chain with 6-12 carbon atoms, and R2 is a sulfonic acid group.

7. The preparation method according to claim 1, characterized in that, The amount of the adjuvant added is 0.1-1 wt% of the mass of cyclododecanone oxime.

8. The preparation method according to claim 1, characterized in that, The molar ratio of concentrated sulfuric acid to cyclododecanone oxime is 1.5-5.

9. The preparation method according to claim 8, characterized in that, The molar ratio of concentrated sulfuric acid to cyclododecanone oxime is 2-3.

10. The preparation method according to claim 1, characterized in that, The continuous organic phase solution and the continuous aqueous phase solution are preheated separately before the reaction is carried out. The preheating temperature is 40-160℃.

11. The preparation method according to claim 10, characterized in that, The preheating temperature is 60-100℃.

12. The preparation method according to claim 1, characterized in that, A dynamic mixer is used to mix the preheated continuous organic phase solution and the continuous aqueous phase solution before the reaction is carried out. The residence time of the reaction solution in the dynamic mixer is 30-90s, and the residence time in the microchannel is 120-600s.

13. The preparation method according to claim 12, characterized in that, The residence time of the reaction solution in the microchannel is 180-300 s.

14. The preparation method according to claim 1, characterized in that, After the reaction is completed, the matured reaction solution is passed into the neutralization system and neutralized with a neutralizing agent. After neutralization, it enters the water washing system. The organic phase after water washing enters the product separation system. The neutralized aqueous phase and the water-washed aqueous phase are combined and enter the by-product separation system.

15. The preparation method according to claim 14, characterized in that, The neutralizing agent is an alkaline solution.

16. The preparation method according to claim 14, characterized in that, The amount of neutralizing agent added is 200%-500% of the molar amount of acid.

17. The preparation method according to claim 16, characterized in that, The amount of neutralizing agent added is 200%-300% of the molar amount of acid.

18. The preparation method according to claim 1, characterized in that, PW water is used for washing, and the amount added is 10%-200% of the mass of the oil phase.

19. The preparation method according to claim 18, characterized in that, PW water is used for washing, and the amount added is 50%-100% of the mass of the oil phase.

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