Apparatus and method for synthesizing 2-methyl-6-acylnaphthalene by continuous acylation

Abstract

The application belongs to the technical field of fine chemical product synthesis, and discloses a device and a synthesis method for continuously acylating 2-methyl-6-acylnaphthalene. After 2-methylnaphthalene raw material liquid, propionyl chloride or acetyl chloride and aluminum chloride mixed acylation liquid obtained thereby are uniformly mixed in a feeding mixer provided by the device, the product material is rapidly sent into an L-shaped tubular reactor for reaction, and the product material can not only remove reaction heat in time after heat exchange and cooling, but also realize continuous synthesis and simple operation. After the material is uniformly mixed by the feeding mixer and then removed for reaction, the synthesis effect caused by non-uniform raw materials during reaction can be avoided, so that the product purity and yield are both high. For the synthesis system of 2-methyl-6-acylnaphthalene, the L-shaped tubular reactor specific to the application can further improve the product yield and purity, and since the L-shaped tubular reactor has small back mixing, uniform radial concentration and temperature distribution, the reaction conversion rate and selectivity are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fine chemical product synthesis, and particularly relates to a device and a method for synthesizing 2-methyl-6-acyl naphthalene through continuous acylation. BACKGROUND

[0002] Polyethylene naphthalate (PEN) is a new type of polyester, which has far superior performance to traditional polyethylene terephthalate (PET), and thus the market demand for it is increasing. 2,6-naphthalene dicarboxylic acid is a key monomer for synthesizing PEN, which is mainly synthesized through liquid-phase catalytic oxidation of 2,6-disubstituted naphthalene. Therefore, to improve the production efficiency of PEN, the synthesis efficiency of 2,6-disubstituted naphthalene should be improved first. However, 2,6-dialkyl naphthalenes such as 2,6-dimethylnaphthalene, 2,6-diethylnaphthalene and 2,6-diisopropyl naphthalene have the disadvantages of long synthesis route and high technical requirements, and due to the use of poor-selectivity alkylation reaction in production, they also cause problems such as difficult product separation. For the above reasons, the current synthesis efficiency of 2,6-dialkyl naphthalene is at a low level, which in turn limits the production of 2,6-naphthalene dicarboxylic acid. In recent years, the synthesis process of 2-methyl-6-acyl naphthalene from 2-methylnaphthalene through Friedel-Crafts acylation reaction has attracted widespread attention. Since the acylation reaction is irreversible and the acyl group has a passivation effect on the naphthalene ring, it is difficult to generate poly-substituted products, and thus the reaction has good selectivity, and after simple separation and purification of the crude product, high-purity 2,6-disubstituted naphthalene can be obtained.

[0003] There are some studies on the synthesis route of 2-methyl-6-acyl naphthalene. Patent CN1817843A discloses a method for preparing 2-alkyl-6-acyl naphthalene, in which halogenated hydrocarbon is used as a solvent and nitro compound is used as a complexing agent, which increases the complexity of the reaction, and the introduction of halogenated hydrocarbon will exacerbate environmental pollution. The selected acylation reaction temperature is relatively low, although the selectivity of the product is improved, but the reaction rate is reduced, and a long reaction time is required, which reduces the production efficiency. Patent CN107879909A discloses a method for synthesizing acyl naphthalene using a micro-channel reactor, but the micro-channel reactor is expensive, difficult to detect and control, and has high requirements for the corrosion resistance of the equipment, which greatly increases the production cost, making it difficult to realize industrialization. Patent CN114621066A discloses a method for synthesizing acyl naphthalene using a stirred reactor, but the kettle-type reactor inevitably has back mixing, and the residence time of the raw materials is inconsistent, which leads to a decrease in product quality. At the same time, since the acylation reaction is a fast and strong exothermic reaction, the kettle-type reactor with small heat exchange area and difficult to control the reaction temperature is not conducive to the synthesis.

[0004] The processes for synthesizing 2-methyl-6-acyl naphthalene in the prior art all adopt a batch method, the process route is relatively mature, but auxiliary operations such as loading and unloading are needed in the batch production process, the cycle is long, the personnel operation is frequent, and the batch product quality is unstable, which is easy to cause loss of materials and energy, and is not conducive to large-scale production. SUMMARY

[0005] In order to overcome the defects of the prior art, the present application provides a simple and efficient device for continuously acylating and synthesizing 2-methyl-6-acyl naphthalene and a method for continuously acylating and synthesizing 2-methyl-6-acyl naphthalene, which overcomes a series of defects such as long cycle, frequent personnel operation and unstable batch product quality caused by the fact that the prior art mainly adopts batch production.

[0006] The above-mentioned object of the present application is achieved by the following technical solutions:

[0007] A device for continuously acylating and synthesizing 2-methyl-6-acyl naphthalene comprises a feed mixer, a plurality of feed pipelines connected to the top of the feed mixer, a first adjusting valve for adjusting the flow of each feed pipeline, a stirring motor connected to the top of the feed mixer, a stirring unit arranged in the feed mixer, and a connecting pipeline arranged at the bottom of the feed mixer.

[0008] The stirring unit comprises a stirring rod and a paddle stirring paddle arranged axially along the stirring rod.

[0009] The storage tank is preferably a small-capacity double-layer glass storage tank with a jacket.

[0010] The L-shaped tubular reactor is provided with a temperature sensor, and the feed mixer is provided with a liquid level meter; the temperature sensor and the liquid level meter are not limited in type, and can realize their working functions, the device is further provided with a control system, and the control system is a PLC control system or a DCS control system; the temperature sensor, the liquid level meter, the first regulating valve, the stirring motor, the second regulating valve and the third regulating valve are connected with the control system. The temperature sensor, the liquid level meter, the first regulating valve, the stirring motor, the second regulating valve and the third regulating valve are not limited to a specific type, and can realize their working functions.

[0011] The application further provides a method for continuously acylating and synthesizing 2-methyl-6-acylnaphthalene by using the device, which comprises the following steps: taking 2-methyl naphthalene as a raw material, propionyl chloride or acetyl chloride as an acylating agent, aluminum chloride as a catalyst, and nitrobenzene as a solvent, and performing acylation reaction in a reactor to obtain product material, and then purifying the product material to obtain 2-methyl-6-propionyl naphthalene or 2-methyl-6-acetyl naphthalene.

[0012] The mass ratio of the 2-methyl naphthalene, the acylating agent, the catalyst and the solvent nitrobenzene is 1:1-2:1-3:4-10, preferably, the mass ratio of the 2-methyl naphthalene, the propionyl chloride and the anhydrous aluminum chloride is 1:1.1-1.5:1.2-1.7, and the mass ratio of the 2-methyl naphthalene, the acetyl chloride and the anhydrous aluminum chloride is 1:1.1-1.5:1.2-1.7.

[0013] The mixing temperature condition in the feed mixer is that the temperature is-10 to 5 DEG C, and is further preferably-5 to 3 DEG C.

[0014] The acylation reaction condition in the L-shaped tubular reactor is that the temperature is 15-45 DEG C, and is further preferably 20-35 DEG C.

[0015] The acylation reaction condition in the L-shaped tubular reactor is that the residence time is 1-7 h, and is further preferably 1-5 h.

[0016] The application has the following beneficial effects compared with the prior art:

[0017] The kettle reactor used in the traditional continuous process inevitably has back mixing, which leads to inconsistent residence time of raw materials, thus reducing product purity and yield, and leading to product quality decline. Meanwhile, the kettle reactor has small heat exchange area, and it is difficult to control the reaction temperature. Since the acylation reaction is a fast and strong exothermic reaction, the kettle reactor is not conducive to the synthesis. The L-shaped tubular reactor provided by the present application has large specific surface area and large heat transfer area, and is particularly suitable for reactions with large heat effect, such as acylation reaction. In addition, the L-shaped tubular reactor has high volume efficiency and fast flow rate, which can significantly improve the process production capacity. Compared with the kettle reactor, the L-shaped tubular reactor has less back mixing, and the fluid flow pattern in the tube is close to ideal fluid at a high flow rate, and the reaction effect is better. And since the amplification effect is much smaller than the kettle reactor, the L-shaped tubular reactor is more suitable for large-scale and continuous chemical production. However, the traditional straight tubular reactor often occupies a large area. The L-shaped configuration of the device in the present application can not only effectively reduce the occupied area, but also facilitate installation and replacement of components.

[0018] It is found in the research process of the present application that the existing process for producing 2-methyl-6-acyl naphthalene all adopts batch method. Since the acylation reaction is a fast and strong exothermic reaction, if the reaction heat cannot be removed in time during continuous production, the reaction system temperature will continue to rise, the reaction will be out of control, and there is even a risk of over-temperature and material flushing. It is further found in the research process of the present application that after the acylation liquid obtained by mixing 2-methyl naphthalene raw material liquid, propionyl chloride or acetyl chloride and aluminum chloride in a solvent of nitrobenzene is uniformly mixed in a feeding mixer provided in the device, it is rapidly sent into the L-shaped tubular reactor for reaction. The product material is cooled after heat exchange, and not only the reaction heat can be removed in time to realize continuous synthesis, but also the operation is simple. Mixing the materials uniformly by using the feeding mixer and then removing the reaction can avoid the decline of the synthesis effect caused by the non-uniformity of the raw materials during the reaction, so that the product purity and yield are both high. In addition, for the synthesis system of 2-methyl-6-acyl naphthalene, the L-shaped tubular reactor specific to the present application can further improve the product yield and purity. It is speculated that the reason is that the L-shaped tubular reactor has small back mixing, and the radial concentration and temperature distribution are uniform, thereby improving the reaction conversion rate and selectivity.

[0019] According to the method for continuously acylating and synthesizing 2-methyl-6-acyl naphthalene provided by the present application, the preferred mass ratio range of 2-methyl naphthalene, acylating agent, catalyst and solvent nitrobenzene is lower than that in the existing synthesis process, which can save cost. This is because for the same amount of 2-methyl naphthalene, there is an optimal amount of catalyst and acylating agent, and excessive catalyst or acylating agent will occupy more solvent, which is not conducive to the reaction. Among them, the preferred residence time is also lower than that in the traditional process, which can improve the production efficiency.

[0020] The continuous acylation synthesis device provided by the application has small floor space, low cost, high automation degree, simple process, and can save manpower while ensuring the quality stability of acylation products, and is very suitable for industrial application. The method for continuously acylating and synthesizing 2-methyl-6-acylnaphthalene provided by the application can greatly reduce the use amount of acylating agent and catalyst, and the purity and yield of the obtained product are higher than those of the existing production process. Since the purification process is currently difficult, the improvement of purity is particularly important.

[0021] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and together with the specific embodiments below, serve to explain the application, but do not constitute a limitation on the application.

[0023] Figure 1 is a schematic diagram of a device for continuously acylating and synthesizing 2-methyl-6-acylnaphthalene.

[0024] Figure 2 is a total ion current gas chromatogram of the crude 2-methyl-6-propionyl naphthalene in Example 1.

[0025] Figure 3 is a total ion current gas chromatogram of the crude 2-methyl-6-acetyl naphthalene in Example 7.

[0026] In the figure: 1. feed pipe, 2. first regulating valve, 3. feed mixer, 4. first heat exchanger, 5. stirring motor, 6. stirring rod, 7. second regulating valve, 8. connecting pipe, 9. L-shaped tubular reactor, 10. second heat exchanger, 11. discharge pipe, 12. third regulating valve, 13. gas line, 14. storage tank, 15. third heat exchanger. DETAILED DESCRIPTION

[0027] The following further illustrates the application, but does not limit the application, and the following non-limiting examples can make those skilled in the art more fully understand the application, but do not limit the application in any way.

[0028] Any value disclosed in the scope of the present application is not limited to the exact range or value, and the ranges or values should be understood to include values close to the ranges or values. For numerical ranges, the end points of each range, the end points of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] In the present application, the orientation words such as "upper" and "lower" refer to the upper and lower directions shown in the drawings, the orientation words such as "top" and "bottom" refer to the top and bottom directions shown in the drawings, and the orientation words such as "inner" and "outer" refer to the inner and outer directions relative to the contour of each component.

[0030] The device for synthesizing 2-methyl-6-acyl naphthalene by continuous acylation comprises a feed mixer 3, a plurality of feed pipelines 1 connected to the top of the feed mixer 3, a first adjusting valve 2 arranged on each feed pipeline 1 to adjust the feed flow, a stirring motor 5 connected to the top of the feed mixer 3, a stirring unit arranged in the feed mixer 3, and the stirring motor 5 connected to the stirring unit; a connecting pipeline 8 arranged at the bottom of the feed mixer 3, and the feed mixer 3 connected to the horizontal section of an L-shaped tubular reactor 9 through the connecting pipeline 8; the top of the vertical section of the L-shaped tubular reactor 9 connected to a discharge pipeline 11 and a gas pipeline 13; the end of the discharge pipeline 11 and the end of the gas pipeline 13 connected to a storage tank 14; a second adjusting valve 7 arranged on the connecting pipeline 8, and a third adjusting valve 12 arranged on the discharge pipeline 11.

[0031] The feed pipelines 1 are used to send raw materials 2-methyl naphthalene, acylating agents, catalysts and solvents into the feed mixer 3; the discharge pipelines 11 are used to output product materials into the storage tank 14; the feed mixer 3 is externally sleeved with a first heat exchanger 4, the L-shaped tubular reactor 9 is externally sleeved with a second heat exchanger 10, and the storage tank 14 is externally sleeved with a third heat exchanger 15; the first heat exchanger 4, the second heat exchanger 10 and the third heat exchanger 15 all change the reaction temperature by introducing cooling media of different temperatures to exchange heat according to the reading of the temperature sensor arranged at the top end of the L-shaped tubular reactor 9; and the gas pipelines 13 are used to discharge the generated gas and balance the gas pressure.

[0032] After the raw materials 2-methyl naphthalene, acylating agents, catalysts and solvents enter the feed mixer 3 through the feed pipelines 1 and are fully mixed, the materials enter the L-shaped tubular reactor 9 through the feeding pipeline 8 to react, and the product materials obtained by the reaction flow into the storage tank 14 as acylation completion liquid through the discharge pipelines 11.

[0033] The device for synthesizing 2-methyl-6-acyl naphthalene by continuous acylation is connected between the components and the pipelines through standardized ground joints in accordance with the provisions of GB / T 15725.6-1995, so that the device is convenient to disassemble, assemble, replace and clean.

[0034] The material of the feed pipeline 1, the feed mixer 3, the connecting pipeline 8, the L-shaped tubular reactor 9, the discharge pipeline 11, the gas pipeline 13 and the storage tank 14 is glass material. Since the various raw materials for the acylation reaction are highly corrosive, ordinary stainless steel material cannot meet the demand, but ordinary or higher quality glass material can, the glass has strong corrosion resistance, can withstand various solvents, and has low price, good thermal conductivity and excellent air tightness.

[0035] The feed mixer 3 is not particularly limited in the present application, and no specific model is limited, but preferably the feed mixer includes a double-layer glass mixing kettle with a jacket, a stirring unit provided in the double-layer glass mixing kettle with a jacket, and the feed mixer 3 is externally connected with a stirring motor 5 for driving the stirring unit. The position of the stirring motor 5 is not particularly limited in the present application, as long as it can drive the stirring unit, and preferably the stirring motor 5 is arranged at the central position of the top outside of the feed mixer 3. The stirring unit is used to stir the material in the feed mixer 3, and the stirring unit includes a stirring rod 6 and a paddle stirring paddle arranged along the axial direction of the stirring rod.

[0036] The number of the feed pipelines 1 is at most 3, and preferably 2. In the preferred embodiment of the present application, the acylation liquid obtained by mixing the 2-methylnaphthalene raw material liquid, the acylating agent and the catalyst through the two feed pipelines 1 can further improve the purity and yield of the obtained 2-methyl-6-acylnaphthalene product.

[0037] An adjusting valve is arranged on each feed pipeline 1, and the adjusting valve is used to control the flow of the reaction feed. In the present application, in order to realize continuous acylation reaction, the feed flow is preferably equal to the discharge flow, the control of the acylation completion liquid extraction amount is equal to the total of the raw material feed amount, and the balance of the material in and out of the system is ensured. In the present application, the liquid level position height in the feed mixer 3 is observed, the valve opening degree is controlled, and the material balance is ensured by keeping the liquid level position unchanged.

[0038] The L-shaped tubular reactor 9 is a double-layer glass L-shaped tubular reactor 9 with a jacket. The L-shaped tubular reactor 9 is used to provide a pipeline with a length-diameter ratio greater than 30, to continuously flow the material in a flow pattern close to a plug flow, and to complete the reaction between the raw materials. The tubular reactor is composed of a horizontal tubular reactor, a vertical tubular reactor and an L-shaped standard ground joint connector, and the two tubular reactors are connected through the L-shaped standard ground joint connector. All the connecting interfaces are standard ground joints specified in GB / T 15725.6-1995.

[0039] The storage tank 14 is not particularly limited in the present application, and any model is not limited, but the storage tank 14 is preferably a small-capacity double-layer glass storage tank with a jacket. The storage tank 14 is only used for temporary storage of the acylation completion liquid for subsequent processes.

[0040] The gas passage 13 is not particularly limited as long as it can discharge the generated gas and balance the gas pressure. By connecting the gas passage 13 to the L-shaped tubular reactor 9, the generated hydrogen chloride gas can be discharged in time, and pressure build-up can be prevented, thereby ensuring the safety of the L-shaped tubular reactor 9.

[0041] The first heat exchanger 4 is not particularly limited in type as long as it can sufficiently cool the material in the feed mixer 3. By providing the first heat exchanger 4 outside the feed mixer 3 and passing a mixture of ethylene glycol and water as a cooling medium, the heat generated during mixing of the feed can be removed in time.

[0042] The second heat exchanger 10 is not particularly limited in type as long as it can cool the material flowing through the L-shaped tubular reactor 9. By providing the second heat exchanger 10 on the L-shaped tubular reactor 9 and passing a mixture of ethylene glycol and water as a cooling medium, the heat generated during the acylation reaction can be removed in time.

[0043] The third heat exchanger 15 is not particularly limited in type. The reaction rate of the material in the low-temperature storage tank 14 is close to zero at low temperature, and as long as the low temperature can be maintained by a cooling medium such as a mixture of ethylene glycol and water, the requirement for temporary storage of the storage tank 14 can be met.

[0044] The device for continuously acylating and synthesizing 2-methyl-6-acylnaphthalene provided by the present application is preferably an L-shaped tubular reactor 9. The traditional continuous process uses a tank reactor, which inevitably has back mixing, resulting in inconsistent residence time of the raw materials, thereby reducing the product purity and yield and causing the product quality to decrease. At the same time, the tank reactor has a small heat exchange area and is not easy to control the reaction temperature. Since the acylation reaction is a fast and strong exothermic reaction, the tank reactor is not suitable for this synthesis. The L-shaped tubular reactor 9 defined by the present application has a large specific surface area and a large heat transfer area, and is particularly suitable for reactions with large heat effects, such as acylation reactions. In addition, the reaction speed and flow rate in the L-shaped tubular reactor 9 are fast, which can significantly improve the production capacity. Compared with the tank reactor, the back mixing is smaller, and the flow pattern of the fluid in the tube is close to that of an ideal fluid at a low flow rate. Due to the much smaller scale-up effect than the tank reactor, the L-shaped tubular reactor 9 is suitable for large-scale and continuous chemical production. The traditional straight tubular reactor often occupies a large area, and the use of the L-shaped tubular reactor 9 can not only reduce the occupied area, but also improve the sealing performance of the reactor and facilitate the installation and replacement of components.

[0045] The application also provides a method for continuously acylating 2-methyl-6-acylnaphthalene by using the device, which comprises the following steps: dissolving 2-methyl naphthalene in nitrobenzene to prepare a raw material solution, dissolving an acylating agent and a catalyst in nitrobenzene to prepare an acylating solution, stirring the mixture in the feeding mixer 3, and then feeding the mixture into the L-shaped tubular reactor 9 to start the reaction, so as to obtain a product material, and continuously discharging the product material from the L-shaped tubular reactor 9 after heat exchange and cooling.

[0046] At present, the existing technology for synthesizing 2-methyl-6-acylnaphthalene mainly adopts a batch method. Since the acylation reaction is a rapid and strong exothermic reaction, if the reaction heat cannot be removed in time during continuous production, the temperature of the reaction system will continue to rise, the reaction will be out of control, and there is even a risk of over-temperature and material overflow. In the research process, it is further found that after the acylating solution obtained by mixing 2-methyl naphthalene raw material solution, propionyl chloride or acetyl chloride and aluminum chloride in nitrobenzene is uniformly mixed in the feeding mixer 3 provided by the device, the mixture is rapidly sent into the L-shaped tubular reactor 9 for acylation reaction, and the product material can be removed in time after heat exchange and cooling, so that continuous synthesis is realized, and the operation is simple. Rapid transfer of the mixed and uniform material can avoid the reaction caused by strong exothermic, and thus the synthesis effect is reduced, so that the product purity and yield are relatively high. In addition, for the synthesis system of 2-methyl-6-acylnaphthalene, the L-shaped tubular reactor 9 specially defined in the application can further improve the product yield and purity. It is speculated that the reason is that the L-shaped tubular reactor 9 inhibits back mixing, so that the raw materials and catalysts in the reaction are fully mixed, and the generated product is uniformly dispersed. After being uniformly mixed in the feeding mixer 3, the mixture is rapidly sent into the L-shaped tubular reactor 9 for reaction, and the product material can be removed in time after heat exchange and cooling, so that continuous synthesis is realized, the operation is simple, and the product purity and yield are relatively high.

[0047] The mass ratio of the 2-methyl naphthalene, the acylating agent, the catalyst and the solvent nitrobenzene is 1:1-2:1-3:4-10. Preferably, the mass ratio of the 2-methyl naphthalene, the propionyl chloride and the anhydrous aluminum chloride is 1:1.1-1.5:1.2-1.7, and the mass ratio of the 2-methyl naphthalene, the acetyl chloride and the anhydrous aluminum chloride is 1:1.1-1.5:1.2-1.7.

[0048] The mixing temperature in the feeding mixer 3 is -10 to 5°C, and is further preferably -5 to 3°C.

[0049] The acylation reaction condition in the L-shaped tubular reactor is that the temperature is 15-45°C, and is further preferably 20-35°C.

[0050] The acylation reaction condition in the L-shaped tubular reactor is that the residence time is 1-7h, and is further preferably 1-5h.

[0051] According to the method for synthesizing 2-methyl-6-acyl naphthalene by continuous acylation provided by the present application, preferably, the acylating agent is selected from one of carboxylic acid derivatives such as acyl chloride, acyl fluoride, acid anhydride, acid and ester, and most preferably is propionyl chloride or acetyl chloride.

[0052] According to the method for synthesizing 2-methyl-6-acyl naphthalene by continuous acylation provided by the present application, preferably, the catalyst is selected from one of Lewis acid, protonic acid and acidic oxide, and most preferably is anhydrous aluminum chloride.

[0053] According to the method for synthesizing 2-methyl-6-acyl naphthalene by continuous acylation provided by the present application, preferably, the solvent is selected from one of nitrobenzene, trimethyl nitrobenzene, halogenated hydrocarbon and chlorobenzene, and most preferably is nitrobenzene.

[0054] According to the device for continuous synthesis method provided by the present application, 2-methylnaphthalene, propionyl chloride or acetyl chloride, aluminum chloride and nitrobenzene solvent can be fed into the feed mixer 3 through two feed pipelines 1 (2-methylnaphthalene is fed through one feed pipeline after being dissolved in the solvent nitrobenzene, and propionyl chloride or acetyl chloride and aluminum chloride are fed through the other feed pipeline 1 after being dissolved in the solvent nitrobenzene), or 2-methylnaphthalene, propionyl chloride or acetyl chloride and aluminum chloride can be respectively dissolved in the nitrobenzene solvent and fed through three feed pipelines 1. Preferably, the raw material liquid, i.e. the nitrobenzene solution of 2-methylnaphthalene, and the acylating liquid, i.e. the nitrobenzene solution of propionyl chloride or acetyl chloride and aluminum chloride, are respectively fed through two feed pipelines 1, and the flow rate can be controlled by the first adjusting valve 2 arranged on the feed pipeline 1. The materials entering the feed mixer 3 are uniformly mixed under stirring (driven by the stirring motor 5 installed on the top of the outer side of the body of the feed mixer 3) and low temperature conditions, the stirring is implemented by the stirring unit, and the low temperature is achieved by the first heat exchanger 4. The stirred materials are fed into the L-shaped tubular reactor 9 through the hard straight pipeline feeding pipeline 8, the materials flow naturally in a state close to ideal plug flow and react, and after a certain residence time, the materials will overflow from the L-shaped tubular reactor 9 as the acylation completed liquid, and then enter the storage tank 14 through the discharge pipeline 11 for temporary storage.

[0055] The present application will be described in detail below through specific examples, but the protection scope of the present application is not limited. Unless otherwise specified, the experimental methods used in the present application are conventional methods, and the experimental apparatus, materials and reagents used can be obtained from commercial channels.

[0056] In the following examples, the purity of the acylation product is determined by the following method: first, the components of the acylation product are analyzed by the GC-MS method, and the retention time of each component is determined. Then, quantitative analysis is performed using a gas chromatograph, and the chromatographic column is BPX-5 (25 m x 0.32 mm x 0.25 μm).

[0057] The yield of the crude product after the acylation reaction and the purity of the target product are calculated as follows:

[0058]

[0059]

[0060] The theoretical mass of the target product is the mass of 2-methylnaphthalene when it is completely converted into the target product 2-methyl-6-acylnaphthalene.

[0061] 2-Methylnaphthalene (2-MN), industrial grade, purity >98.3%; propionyl chloride (PC); acetyl chloride (AC); nitrobenzene; and anhydrous aluminum trichloride (AlCl3) were all commercially available products of analytical grade.

[0062] Example 1

[0063] like Figure 1 As shown, the mass ratio of 2-methylnaphthalene:propionyl chloride:aluminum trichloride is 1:1.3:1.5. The nitrobenzene solution of 2-methylnaphthalene, the propionyl chloride solution, and the nitrobenzene solution of aluminum trichloride are pumped into the feed mixer 3 (50 mL volume) through two feed lines 1 at flow rates of 0.78 mL / min and 1.33 mL / min, respectively, with a residence time of 0.2 h. A stirring motor 5, installed on the top of the feed mixer 3, drives a stirring rod 6 for stirring. A low-temperature ethanol-water mixture is used as the heat exchange medium in the first heat exchanger 4 outside the feed mixer 3 to cool the materials and maintain the temperature inside the feed mixer 3 at -5 to -3 °C, ensuring thorough mixing. Next, the feed flow rate is adjusted to 2.11 mL / min using the second regulating valve 7. The mixture flows into the L-shaped tubular reactor 9 through the connecting pipe 8, and the overall flow state is close to plug flow. Meanwhile, the L-shaped tubular reactor 9 is jacketed with a second heat exchanger 10, through which a mixture of ethylene glycol and water at 20-25°C is introduced as a cooling medium to maintain the temperature inside the L-shaped tubular reactor 9 at 25°C. After 3 hours of feeding, the material flows to a position close to the liquid level in the feed mixer 3. Since the overflow port, located on the top side wall of the vertical section of the L-shaped tubular reactor 9 and connected to the discharge pipeline 11, is at the same height as the lowest liquid level in the feed mixer 3, the material will continuously flow out through the overflow port and into the storage tank 14 via the discharge pipeline 11. The storage tank 14 is equipped with a third heat exchanger 15, which circulates a low-temperature ethanol-water mixture to cool the completed liquid and inhibit further reaction. The storage tank 14 is connected to the L-shaped tubular reactor 9 via a gas passage 13 to ensure gas pressure balance between the two, allowing the product material to flow out naturally. Gas chromatography analysis of the product material revealed a purity of 84.55% for 2-methyl-6-propionylnaphthalene and a yield of 96.23%.

[0064] Example 2

[0065] The method of Example 1 was followed, except that the nitrobenzene solution of 2-methylnaphthalene, propionyl chloride and the nitrobenzene solution of aluminum trichloride were fed at a flow rate of 2.34 mL / min, 3.99 mL / min, respectively, and the flow rate was adjusted to 6.33 mL / min using the second regulating valve 7 to maintain the material balance, and the rest of the conditions were kept the same. Under this condition, the residence time was shortened to 1 h, and the purity of the obtained 2-methyl-6-propionyl naphthalene was 83.27%, and the yield was 89.94%.

[0066] Example 3

[0067] The method of Example 1 was followed, except that the reaction temperature was 35°C, and the rest of the conditions were kept the same. The purity of the obtained 2-methyl-6-propionyl naphthalene was 83.86%, and the yield was 96.07%.

[0068] Example 4

[0069] The method of Example 1 was followed, except that the mass ratio of 2-methylnaphthalene: propionyl chloride: aluminum trichloride was 1:1.3:1.6, and the rest of the conditions were kept the same. The purity of the obtained 2-methyl-6-propionyl naphthalene was 85.52%, and the yield was 94.60%.

[0070] Example 5

[0071] The method of Example 1 was followed, except that the mass ratio of 2-methylnaphthalene: propionyl chloride: aluminum trichloride was 1:1.4:1.5, and the rest of the conditions were kept the same. The purity of the obtained 2-methyl-6-propionyl naphthalene was 84.14%, and the yield was 93.61%.

[0072] Example 6

[0073] The method of Example 1 was followed, except that the mass ratio of 2-methylnaphthalene: propionyl chloride: aluminum trichloride was 1:1.3:1.4, and the feeding time was changed to 6 h, and under the condition that the residence time remained unchanged, two batches of acylation completion liquid were collected separately. The two batches of completion liquid were analyzed and tested respectively, and the purity of the obtained 2-methyl-6-propionyl naphthalene was 84.88% and the yield was 90.91% for the first batch; and the purity of the obtained 2-methyl-6-propionyl naphthalene was 85.46% and the yield was 92.56% for the second batch. The yield of the two batches was relatively small, indicating that the production process was relatively stable.

[0074] Example 7

[0075] The method of Example 1 was followed, except that the acylating agent was selected to be acetyl chloride, the mass ratio of 2-methylnaphthalene: acetyl chloride: aluminum chloride was 1:1.2:1.45, the residence time was 4 h, and the remaining conditions were kept the same. The purity of the obtained 2-methyl-6-acetylnaphthalene was 81.85%.

[0076] Comparative Example 1

[0077] 2-methyl-6-propionylnaphthalene was synthesized by a batch process. The best ratio reported in the prior art (mass ratio of 2-methylnaphthalene: propionyl chloride: aluminum chloride was 1:1.4:1.7) was implemented, and in a 500 mL reaction kettle, a nitrobenzene solution of 2-methylnaphthalene was added dropwise with a nitrobenzene solution of aluminum chloride and propionyl chloride, the dropwise addition time was controlled within 0.5 h, the temperature was controlled within -5 to -3°C, and after the dropwise addition was completed, the mixture was stirred for 0.5 h. Then the reaction was carried out by changing the ambient temperature, and the reaction temperature was maintained at 25°C, and the reaction time was controlled for 5 h. The purity of the obtained 2-methyl-6-propionylnaphthalene was 81.70%, and the yield was 92.00%. The batch operation of the batch production device was tedious, the equipment utilization was low, and the production time was long.

[0078] Comparative Example 2

[0079] The method of Comparative Example 1 was followed, except that the mass ratio, mixing temperature, reaction time, and reaction temperature of Example 1 were used. The purity of the obtained 2-methyl-6-propionylnaphthalene was 87.16%, and the yield was 92.60%.

[0080] Comparative Example 3

[0081] The method of Example 1 was followed, except that 2-methylnaphthalene, propionyl chloride, and anhydrous aluminum chloride were all dissolved in the nitrobenzene solvent at low temperature, and the mixture was fed into the reaction through one feed pipe after being uniformly mixed. The purity of the obtained 2-methyl-6-propionylnaphthalene was 84.31%, and the yield was 85.85%.

[0082] Comparative Example 4

[0083] The method of Comparative Example 1 was followed, except that the mass ratio, mixing temperature, reaction time, and reaction temperature of Example 3 were used. The purity of the obtained 2-methyl-6-acetylnaphthalene was 75.32%.

[0084] In the comparative example 1, the 2-methyl-6-propionyl naphthalene was synthesized by using a kettle reactor in a batch reaction mode, and compared with the examples, it can be seen that the purity and yield are greatly reduced. In the comparative example 2, the synthesis was still carried out by using a kettle reactor in a batch reaction mode, and by modifying the mass ratio of raw materials and other process parameters, the yield and purity were improved, but still not as high as the continuous production. In the comparative example 3, the mixture was fed into the device, and due to the strong heat release, the reaction was advanced, which greatly reduced the yield. In the comparative example 4, the 2-methyl-6-acetyl naphthalene was synthesized by using a kettle reactor in a batch reaction mode, and the purity of the product was greatly reduced. Through the comparison of the above examples and comparative examples, it can be seen that the device and synthesis method for continuously acylating to synthesize 2-methyl-6-acyl naphthalene provided by the present application not only has high automation degree and can realize continuous production, reduces the reaction time, improves the production efficiency, reduces the amount of acylating agent and catalyst, reduces the synthesis cost, reduces the difficulty of subsequent treatment and recovery of solvent, and has high product purity and yield. Due to the difficulty of the current purification process, the improvement of the purity is particularly important.

[0085] The above-described embodiments are only preferred embodiments of the present application, and not all the embodiments that can be implemented by the present application. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present application should be considered to be within the scope of protection of the claims of the present application.

[0086] The above describes the preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0087] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0088] In addition, various different embodiments of the present application can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present application, and they should also be considered as disclosed by the present application.

Claims

1. An apparatus for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene, characterized in that, The device comprises a feed mixer, a plurality of feed pipelines connected to the top of the feed mixer, a first adjusting valve arranged on each feed pipeline to adjust the flow of the feed, a stirring motor connected to the top of the feed mixer, a stirring unit arranged in the feed mixer, and a liquid level meter arranged in the feed mixer.

2. An apparatus for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 1, characterized in that The stirring unit comprises a stirring rod and a paddle stirring paddle arranged along the axial direction of the stirring rod.

3. An apparatus for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 2, characterized in that The storage tank is a small-capacity double-layer glass storage tank with a jacket.

4. An apparatus for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 3, characterized in that The device is also provided with a control system, which is a PLC control system or a DCS control system.

5. A process for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to any one of claims 1 to 4, characterized in that, The method comprises: using 2-methylnaphthalene as a raw material, propionyl chloride or acetyl chloride as an acylating agent, aluminum chloride as a catalyst, and nitrobenzene as a solvent to perform an acylation reaction in a reactor to obtain a product material, and then purifying the product material to obtain 2-methyl-6-propionyl naphthalene or 2-methyl-6-acetyl naphthalene.

6. The process for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 5, characterized in that, The mass ratio of the 2-methylnaphthalene, the acylating agent, the catalyst, and the solvent nitrobenzene is 1:1-2:1-3:4-10.

7. The process for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 6, characterized in that, The mixing temperature in the feed mixer is -10 to 5°C.

8. The process for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 7, characterized in that, The acylation reaction in the L-shaped tubular reactor is performed at a temperature of 15-45°C.

9. The process for the continuous acylation synthesis of 2-methyl-6-acylnaphthalene according to claim 8, characterized in that, The acylation reaction in the L-shaped tubular reactor is performed for a residence time of 1-7h.

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