Method for preparing laurolactam from cyclododecanone oxime

Abstract

The invention discloses a method for preparing laurolactam from cyclododecanone oxime, which comprises the following steps: diluting a cyclododecanone oxime raw material, mixing with a fluorocarbon auxiliary agent, preheating, enabling the preheated cyclododecanone oxime raw material and concentrated acid to pass through a dynamic mixer and then enter a microchannel for reaction, neutralizing and washing reaction liquid, and separating to obtain a laurolactam product, the reaction conversion rate and selectivity can be effectively enhanced, the stability and safety of device operation are improved, and the product quality is improved.

Description

Technical Field

[0001] The invention discloses a method for preparing laurolactam from cyclododecanone oxime, and belongs to the field of organic synthesis. Background Art

[0002] Lauryl lactam is an important monomer for producing nylon 12. It is usually prepared by oximation and rearrangement of cyclododecanone. The reaction equation is as follows:

[0003]

[0004] The rearrangement reaction of cyclododecanone oxime is a typical Beckmann rearrangement reaction. Usually, under the action of concentrated sulfuric acid or fuming sulfuric acid catalyst, cyclododecanone oxime undergoes rearrangement reaction with a very high conversion rate, and lauryl lactam is quickly generated. At the same time, concentrated acid will also quickly absorb the water in the system to avoid side reactions. The reaction mechanism is as follows:

[0005]

[0006] In the rearrangement reaction of cyclododecanone oxime, concentrated acid has a strong dehydrating property, which can cause many side reactions in the system. In severe cases, a large amount of carbonization will occur, so the reaction residence time and temperature need to be precisely controlled. Concentrated acid and ketoxime raw materials are highly viscous fluids with poor fluidity. In addition, cyclododecanone oxime is produced in an organic solvent system, while concentrated acid is produced in an aqueous phase system. The two-phase reaction increases the difficulty of mixing the system, and a strong stirring system is usually required. The rearrangement reaction process releases a large amount of reaction heat, which is prone to local overheating and production hazards. In addition, the concentration distribution of various substances in the system is uneven, and the conversion rate and selectivity of the reaction are affected. The main heat transfer methods in current engineering include external circulation condenser heat transfer, solvent evaporation heat transfer, etc., but the above methods do not solve the problem of uneven concentration and temperature distribution during the rearrangement reaction process, and it is difficult to control the occurrence of side reactions in the reaction, resulting in low selectivity.

[0007] Patent CN113769683 describes a short-process continuous preparation system and method for laurolactam, which uses an ultra-gravity reactor to couple distillation, neutralization, and phase separation processes to carry out rearrangement reactions. However, the system involves operations such as rearrangement reactions, neutralization, and phase separation, which makes it difficult to achieve continuous production in engineering, and does not solve the problem of many side reactions in the rearrangement reaction. Patent CN109867616 mentions that the rearrangement reaction uses a composite stirring form of propellers and emulsifiers to enhance the mass transfer effect, but because the stirring requires full-frequency high-speed operation, it is very easy to be damaged, and there are no control measures for the side reactions in the rearrangement reaction. After the reaction of this invention, the content of rearranged carbides is high and difficult to separate in the subsequent system. Patent CN115260073 mentions replacing concentrated sulfuric acid or fuming sulfuric acid with 65-98% sulfuric acid. On the one hand, the reduction in 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 equipment is particularly serious, and the equipment material needs to be upgraded. Even HC material cannot be used for a long time, and materials such as enamel glass are very easy to break, which greatly increases the production cost.

[0008] In summary, there is an urgent need to develop a more efficient and more environmentally friendly method for preparing laurolactam to solve the problems of low efficiency, low safety, many side reactions, high heat release, and strong corrosiveness in the production of laurolactam. Summary of the invention

[0009] In view of the above problems existing in the prior art, the object of the present invention is to provide a method for preparing lauryl lactam from cyclododecanone oxime, which has good mass transfer and heat transfer effects. By adding auxiliary agents, the Beckmann rearrangement reaction can be rapidly promoted, while the residence time can be reduced, the occurrence of side reactions can be reduced, and the product quality can be effectively improved.

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

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

[0012] (2) mixing the above-mentioned continuous organic phase solution and the continuous aqueous phase solution, reacting the mixed solution, causing cyclododecanone oxime to undergo a Beckmann rearrangement reaction under acid catalysis, and then ripening;

[0013] (3) The reaction solution after aging is neutralized, washed, and separated to obtain laurolactam.

[0014] In the present invention, since the Beckmann rearrangement uses concentrated sulfuric acid as a catalyst, the selected solvent should not contain active groups, and the organic solvent is one or two or more of inert solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, benzene, toluene, and xylene, preferably methylcyclohexane and ethylcyclohexane;

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

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

[0017] In the present invention, the auxiliary agent is a fluorocarbon surfactant having the following structure:

[0018]

[0019] Wherein, R1 is a long-chain fluoroalkyl non-polar group, preferably a fluorocarbon chain with 6-12 carbon atoms, and R2 is a polar group such as a sulfonic acid group, a nitrate group, a formic acid group, etc., preferably a sulfonic acid group as a substituent;

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

[0021] In the present invention, a fluorocarbon surfactant is used as an auxiliary agent, which has extremely high surface activity and can significantly reduce the surface tension of the aqueous solution at an extremely low application concentration; in addition, the fluorine-carbon bond energy of the fluorocarbon surfactant is high and difficult to be destroyed. In addition, the fluorine atom has a shielding effect on the carbon-carbon bond. Since the radius of the fluorine atom is larger than that of the hydrogen atom, the fully fluorinated carbon-carbon bond can be effectively shielded and protected, reducing the possibility of the carbon-carbon bond being destroyed, thereby making the fluorocarbon chain more stable and will not decompose even in a high temperature environment;

[0022] In the present invention, the long-chain fluorocarbon additive has a high boiling point and is discharged from the system as a heavy component in the distillation system and treated as waste liquid, without any effect on the product.

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

[0024] In the present invention, the temperature of the preheater is 40-160°C, preferably 60-100°C. The viscosity of concentrated sulfuric acid and cyclododecanone oxime solution is relatively high, resulting in poor fluidity in pipeline transportation. Therefore, the present invention reduces the viscosity of ketone oxime by preparing the solution. Preferably, the continuous organic phase solution and the continuous aqueous phase solution are preheated separately before reacting, and the fluidity of sulfuric acid and cyclododecanone oxime solution is improved by preheating, so as to enhance the transportation and mixing effects;

[0025] In the present invention, the reaction in step (2) is carried out in a microchannel reactor.

[0026] In the present invention, a dynamic mixer is used to pre-mix the preheated continuous organic phase solution and the continuous aqueous phase solution, and then react. The pre-mixing and microchannel reaction can effectively solve the problem of mass transfer and heat transfer in the rearrangement reaction. The residence time of the reaction solution in the dynamic mixer is 30-90s, and the residence time in the microchannel is 120-600s, preferably 180-300s.

[0027] After the reaction is completed, the above-mentioned matured reaction liquid is passed into the neutralization system, neutralized with a neutralizer, and then enters the water washing system. The organic phase after water washing enters the product separation system, and the neutralized water phase and the water phase after water washing are combined and enter the by-product separation system.

[0028] In the present invention, 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 invention, washing is performed with water, and PW water is used for washing, and the added mass is 10%-200% of the mass of the oil phase, preferably 50%-100%;

[0030] In the present invention, in order to prevent concentrated sulfuric acid from continuing to catalyze the product to produce a side reaction, the reaction liquid needs to be quenched in time. The present invention uses alkali solution to neutralize the acid to quench the reaction. The neutralized oil phase is washed with water again. The neutralization and washing are both performed by a rotary disc extraction tower, and the reaction liquid is added through the bottom of the tower, and the water phase is added to the top of the tower. The height-to-diameter ratio of the rotary disc extraction tower is 5-10:1, and a three-blade stirring paddle is distributed in the tower, with a spacing of 100-150mm and a stirring speed of 10-20rpm / min.

[0031] In the present invention, since the solubility of laurolactam in organic solvents is limited, it is necessary to control the temperature of neutralization and water washing to be above 60° C. to avoid precipitation of laurolactam;

[0032] In the present invention, the organic phase enters the product separation system and is separated by conventional distillation, and the product purity is ≥99%, and the ethanol solubility color number is ≤10; the aqueous phase enters the by-product separation system and obtains the corresponding sulfate by-product by conventional recrystallization; distillation and recrystallization are conventional processes, which can be implemented by ordinary technicians in this field according to physical property data, and will not be described in detail in the present invention.

[0033] Compared with conventional technologies, the present invention has the following beneficial effects:

[0034] 1) The present invention provides a method for preparing lauryl lactam from cyclododecanone oxime using microchannel technology. The reaction form of the microchannel reactor can improve the mass transfer and heat transfer effect of the reaction and avoid adverse effects caused by heat accumulation;

[0035] 2) The present invention enhances the mixing of the oil phase and the concentrated sulfuric acid phase by adding a fluorocarbon additive, which has the characteristics of low dosage, high activity and good stability, can promote the rapid progress of the Beckmann rearrangement reaction, and at the same time reduce the residence time and the generation of side reactions, which can effectively improve the product quality;

[0036] 3) The present invention ensures the fluidity of the material and the solubility of the product by screening the process conditions and solvents, while improving the conversion rate of the raw materials, avoiding the adverse effects of the decomposition of the raw materials in the subsequent system, effectively improving the production efficiency, reducing energy consumption, and greatly saving the production cost;

[0037] 4) In the present invention, the reaction solution is neutralized with alkaline solution, and corresponding sulfate byproducts are produced, thereby increasing the overall added value of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a process flow chart of Example 1 of the present invention,

[0039] In the figure, 1 is solvent, 2 is cyclododecanone oxime, 3 is auxiliary agent, 4 is acid, 5 is alkali solution, 6 is PW water, 7 is laurolactam, 8 is sulfate, A1 is organic phase, A2 is acid phase, B1 / B2-preheater, C-dynamic mixer, D-microchannel reactor, E-neutralization, F-water washing, G1-distillation, and G2-recrystallization. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments. It should be noted that these specific embodiments are only for illustration and should not be construed as limiting the scope of protection claimed by the present invention.

[0041] The analytical test methods used in the following embodiments of the present invention are:

[0042] Gas phase analysis: Shimadzu 2010 Plus; Inlet temperature: 280 °C; Split ratio: 30:1; Chromatographic column: DB-5 (30 m × 0.25 mm × 0.25 μm); Temperature program: 50 °C for 2 min, increase to 80 °C at 5 °C / min, maintain for 10 min, increase to 300 °C at 15 °C / min, maintain for 10 min; FID detector temperature: 300 °C.

[0043] Chromaticity analysis: HACH LICO620 desktop colorimeter, color values ​​in line with ASTM standards, measurement results are consistent with ASTM standards.

[0044] The sources of the main raw materials used in the following examples of the present invention are as follows. Unless otherwise specified, other raw materials are common commercially available raw materials:

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

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

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

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

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

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

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

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

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

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

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

[0056] Sodium hydroxide (32% solution), concentrated sulfuric acid (98%), ammonia water (25%), cyclododecanone oxime, PW pure water, produced by the device;

[0057] Example 1

[0058] The feed rate of the raw material cyclododecanone oxime is 19.73 g / h (0.1 mol / h), the feed rate of the solvent ethylcyclohexane is 98.5 g / h, and the feed rate of the auxiliary agent 4-dodecylbenzenesulfonic acid is 0.197 g / h to obtain a mixed organic phase material A1, and the feed rate of 98% concentrated sulfuric acid is 29.42 g / h (0.3 mol / h) as the aqueous phase material A2; the temperature of the preheaters B1 and B2 are both 100°C, After preheating, stream A1 (118.43 g / h) was mixed with preheated stream A2 (29.42 g / h) in a dynamic mixer, wherein the residence time in the dynamic mixer was controlled to be 90 s. The mixed materials entered the microchannel reactor at a flow rate of 149.62 g / h, and the residence time in the microchannel was 300 s. The reaction sampling test components were calculated, and the conversion rate was 99.8%, and the selectivity of laurolactam was 99.6% ; After the reaction is completed, the material enters the neutralization extraction tower, the reaction liquid is added through the tower kettle, and the alkali solution is added to the top of the tower. The extraction tower is 1200mm high and 120mm in diameter. The tower is separated by 150mm and stirred at a speed of 20rpm / min. The alkali solution is 32% sodium hydroxide solution, and the addition flow rate is 112.50g / h (NaOH: 0.9mol / h). The neutralization tower is controlled at a temperature of 60°C. After mixed phase separation, the oil phase at the top of the neutralization tower enters the tower kettle of the water washing tower. The parameters of the water washing tower are consistent with those of the neutralization tower. The amount of PW water added at the top of the tower is 118.4g / h. After water washing, the water phase is mixed with the water phase of the tower kettle of the neutralization tower and enters the crystallization system. The sodium sulfate product is obtained by recrystallization; the oil phase enters the rectification system, and the lauryl lactam product is obtained by vacuum distillation. After gas chromatography analysis, the purity is 99.85%, and the calculated product yield is 98.77%. The ethanol dissolution color number is 4Hazen;

[0059] Example 2

[0060] The feed rate of the raw material cyclododecanone oxime is 19.73 g / h (0.1 mol / h), the feed rate of the solvent methylcyclohexane is 394.6 g / h, and the feed rate of the auxiliary agent 3-dodecylbenzenesulfonic acid is 0.02 g / h to obtain a mixed organic phase material A1, and the feed rate of 98% concentrated sulfuric acid is 19.61 g / h (0.2 mol / h) as the aqueous phase material A2; the temperature of the preheaters B1 and B2 is 60°C, and the stream A1 (414.35 g / h) is preheated and mixed with the preheated stream A2 (19.61 g / h) in a dynamic mixer, wherein the residence time in the dynamic mixer is controlled to be 30 s, and the mixed material enters the microchannel reactor at a flow rate of 433.96 g / h, and the residence time in the microchannel is 180 s. The reaction sampling test components, the calculated conversion rate is 99.7%, and the laurolactam selectivity is 99.4%; after the reaction is completed, the material enters the neutralization extraction tower, the reaction liquid is added through the tower kettle, and the alkali solution is added to the tower top. The extraction tower is 1200mm high and 240mm in diameter. Stirring is set every 100mm in the tower, the speed is 10rpm / min, the alkali solution is 25% ammonia water, the addition flow rate is 56g / h (NH3: 0.4mol / h), the neutralization tower is controlled at 80°C, after mixed phase separation, the oil phase at the top of the neutralization tower enters the water washing tower kettle, the water washing tower parameters are consistent with the neutralization tower parameters, the amount of PW water added at the top of the tower is 207.2g / h, the water phase after water washing is mixed with the water phase of the neutralization tower kettle and enters the crystallization system, and the ammonium sulfate product is obtained by recrystallization; the oil phase enters the distillation system, and the lauryl lactam product is obtained by vacuum distillation. After gas chromatography analysis, the purity is 99.82%, and the calculated product yield is 98.74%. The ethanol dissolution color number is 5Hazen;

[0061] Example 3

[0062] Referring to the method of Example 1, the only difference is that the added auxiliary agent is 4-fluorohexylbenzenesulfonic acid, the material flow rate and process conditions are the same, and the reaction results are shown in the following table;

[0063] Comparative Example 1

[0064] The method of Example 1 was used with reference to the method of Example 1, except that the auxiliary agent was replaced by a solvent of equal mass, that is, 0.197 g / h of ethylcyclohexane solvent was added, and the other process parameters were the same. The reaction results are shown in the following table;

[0065] Comparative Example 2

[0066] Referring to the method of Example 1, the only difference is that the auxiliary agent is replaced by dodecylbenzenesulfonic acid of the same mass, that is, 0.197 g / h of dodecylbenzenesulfonic acid is added, and the other process parameters are the same. The reaction results are shown in the following table;

[0067] Comparative Example 3

[0068] The method of Example 1 was used with reference to the difference that the acid was dilute sulfuric acid, 50% dilute sulfuric acid was prepared, the amount of sulfuric acid added was 58.84 g / h (0.3 mol / h), and the other process parameters were the same. The reaction results are shown in the following table;

[0069] Table 1, summary of characterization results of examples and comparative examples

[0070]

[0071]

[0072] It can be seen from the above embodiments and comparative examples that the method for preparing lauryl lactam from cyclododecanone oxime using a microchannel technology of the present invention can reduce the viscosity of the material, improve the mixing effect of the reaction through engineering equipment such as a dynamic mixer and a microchannel, introduce a stable and efficient fluorocarbon additive, and further improve the mixing effect of the acid oxime, thereby enhancing the conversion rate and selectivity of the reaction; at the same time, the present invention adopts a microchannel reaction form to reduce the residence time, avoid the phenomenon of a large amount of carbonization in the reaction, and at the same time enhance the mass transfer and heat transfer effect of the system, improve production efficiency, and enhance process safety;

[0073] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing laurolactam from cyclododecanone oxime, characterized in that: The following steps are involved: (1) mixing cyclododecanone oxime with an organic solvent, and adding an auxiliary agent to the above solution to form a continuous organic phase solution; using a concentrated sulfuric acid solution as a continuous aqueous phase solution; (2) mixing the above-mentioned continuous organic phase solution and the continuous aqueous phase solution, reacting the mixed solution, causing cyclododecanone oxime to undergo a Beckmann rearrangement reaction under acid catalysis, and then ripening; (3) The reaction solution after aging is neutralized, washed, and separated to obtain laurolactam.

2. The preparation method according to claim 1, characterized in that: The organic solvent is one or two or more of cyclohexane, methylcyclohexane, ethylcyclohexane, benzene, toluene and xylene, preferably methylcyclohexane and ethylcyclohexane; Preferably, in the organic solvent solution of cyclododecanone oxime, the cyclododecanone oxime concentration is 5-20wt% of the cyclododecanone oxime solution; Preferably, the concentrated sulfuric acid is concentrated sulfuric acid or fuming sulfuric acid with a mass fraction of more than 95%, preferably 98% concentrated sulfuric acid.

3. The preparation method according to claim 1 or 2, characterized in that: The auxiliary agent is a fluorocarbon surfactant having the following structure: Wherein, R1 is a long-chain fluoroalkyl non-polar group, preferably a fluorocarbon chain with 6-12 carbon atoms, and R2 is a polar group such as a sulfonic acid group, a nitrate group, a formic acid group, etc., preferably a sulfonic acid group as a substituent; Preferably, the amount of the additive added is 0.1-1 wt % of the mass of cyclododecanone oxime.

4. The preparation method according to any one of claims 1 to 3, characterized in that The molar ratio of concentrated sulfuric acid to cyclododecanone oxime is 1.5-5, preferably 2-3; Preferably, the temperature of the preheater is 40-160°C, preferably 60-100°C; Preferably, the reaction in step (2) is carried out in a microchannel reactor; Preferably, a dynamic mixer is used to pre-mix the preheated continuous organic phase solution and the continuous aqueous phase solution before reacting. The residence time of the reaction solution in the dynamic mixer is 30-90 s, and the residence time in the microchannel is 120-600 s, preferably 180-300 s.

5. The preparation method according to any one of claims 1 to 4, characterized in that: After the reaction is completed, the above-mentioned matured reaction liquid is passed into the neutralization system, neutralized with a neutralizer, and then enters the water washing system. The organic phase after water washing enters the product separation system, and the neutralized water phase and the water phase after water washing are combined and enter the by-product separation system; Preferably, 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%; Preferably, PW water is used for water washing, and the added mass is 10%-200% of the mass of the oil phase, preferably 50%-100%.

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