A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor

Abstract

The invention discloses a method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor, comprising the following steps: adding anhydrous aluminum chloride to nitrobenzene, heating and stirring to dissolve the anhydrous aluminum chloride fully, and obtaining a clarified uniform solution, i.e., acylation solution, after suction filtration; adding 2 methyl naphthalene to nitrobenzene, and then adding acyl chlorides, and mixing to obtain a stock solution; respectively drawing acylation solution and stock solution with a metering pump, injecting the two liquids into a three-way micro mixer through a syringe, and the total reaction solution after mixing flows out from the channel outlet of the micro mixer, and then flows into a multi-tank series reactor, and an acylation reaction liquid is obtained after the reaction, and the acylation reaction liquid is hydrolyzed, and rectification obtains 2 methyl 6 acyl naphthalene. The synthetic method of the present invention combines the advantages of reaction mechanism, micro mixer and kettle reactor, and performs continuous flow reaction synthesis, and can improve reaction efficiency, ensure sufficient reaction, and obtain products with higher yield, selectivity and purity.

Description

Technical Field

[0001] The invention belongs to the technical field of acyl naphthalene synthesis, and particularly relates to a method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reaction kettle. Background Art

[0002] 2,6-Naphthalene dicarboxylic acid is an important intermediate for the manufacture of polyester fibers and insulating materials, and 2-methyl-6-acylnaphthalene is an important raw material for the preparation of 2,6-naphthalene dicarboxylic acid. At present, the synthesis of 2-methyl-6-acylnaphthalene mostly uses 2-methylnaphthalene as raw material, acyl chloride as acylating agent, aluminum chloride as Lewis acid catalyst, nitrobenzene as solvent, and Friedel-Crafts acylation reaction at a certain temperature and normal pressure. The selectivity and yield of the Friedel-Crafts acylation product are related to factors such as mixing temperature, reaction temperature, feeding and mixing method, reactant ratio, reaction time, etc.

[0003] At present, two types of reactors are used for acylation reactions, namely intermittent reactors or continuous microchannel reactors. Intermittent reactors have the advantages of simple equipment, relatively uniform material concentration, wide application range, and low investment, but the disadvantages are that they are not suitable for scaled-up continuous mixing production, small heat exchange area, difficult to control reaction temperature, and difficult to stabilize product quality. Continuous microchannel reactors have the advantages of high mass transfer and heat transfer efficiency, high specific surface area, precise temperature control, good airtightness, high safety, and low pollution, but the disadvantages are the risk of blockage, high scale-up cost, and complex operation.

[0004] As for the mixing method of the reaction raw materials, the first method is to first dissolve the acyl chloride and aluminum chloride in nitrobenzene solvent to obtain an acylation drop solution, and then drop the resulting solution into nitrobenzene containing 2-methylnaphthalene. In this mixing method, the acyl chloride and aluminum chloride in the nitrobenzene solution first form an acyl cation intermediate CH3CH2CO + Then the liquid is added intermittently at low temperature or continuously mixed with 2-methylnaphthalene solution to react, CH3CH2CO + The reaction with 2-methylnaphthalene will immediately react for a period of time under kinetic control to produce the main product and isomer byproducts. The second method is to add the nitrobenzene solution of 2-methylnaphthalene back dropwise to the nitrobenzene solution of acyl chloride and aluminum chloride for reaction. The reaction selectivity of method one (about 85.0%) is much greater than that of method two (about 79.0%). This is because in method two, 2-methyl reacts with a large amount of acyl cation intermediate CH3CH2CO + The kinetic reaction time is longer.

[0005] However, the selectivity of the reaction products of the above reactors and raw material mixing methods did not exceed 90.0%, and the selectivity was still relatively low. How to further improve the selectivity of the reaction products of 2-methyl-6-acylnaphthalene is a technical problem to be solved by the present invention. Summary of the invention

[0006] The purpose of the present invention is to provide a method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor, so as to solve the problem that the selectivity of the reaction product of 2-methyl-6-acyl naphthalene is low and cannot exceed 90%.

[0007] To achieve the above object, the present invention provides a method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor, comprising the following steps:

[0008] (1) Preparation of acylation solution

[0009] Add anhydrous aluminum chloride to nitrobenzene, heat and stir to fully dissolve the anhydrous aluminum chloride, and filter to obtain a clear and uniform solution, i.e., the acylated solution;

[0010] (2) Preparation of raw material solution

[0011] Add 2-methylnaphthalene to nitrobenzene, then add acyl chloride, mix well to obtain a raw material solution;

[0012] (3) Acylation reaction

[0013] A metering pump is used to suck the acylation liquid and the raw material liquid respectively, and the two liquids are injected into a three-way micro mixer through a syringe. The mixed total reaction liquid flows out from the channel outlet of the micro mixer and then flows into a multi-reactor series reactor to obtain an acylation reaction liquid after the reaction. The acylation reaction liquid is hydrolyzed and distilled to obtain 2-methyl-6-acylnaphthalene.

[0014] Preferably, the molar ratio of 2-methylnaphthalene, acyl chloride and anhydrous aluminum chloride in step (1) and step (2) is 1:1.1-1.3:1.25-1.5.

[0015] Preferably, the heating temperature in step (1) is 45-55°C.

[0016] Preferably, the acyl chloride in step (2) is acetyl chloride or propionyl chloride.

[0017] Preferably, in step (3), the flow rate of the acylation solution is 395-405 g / h, and the flow rate of the raw material solution is 300-310 g / h.

[0018] Preferably, in step (3), the mixing time of the micro mixer is 80 to 120 ms, and the temperature of the micro mixer is controlled at 15° C. in a thermostatic bath.

[0019] Preferably, the multi-reactor series reactor in step (3) comprises 2-3 reactors.

[0020] Preferably, the total residence time of the multiple reactors in series in step (3) is 120 to 180 min, and the temperature is controlled at 40°C.

[0021] Preferably, in step (3), the internal volume of the micromixer is 15 L, and the size of the mixing channel is 45×200 um.

[0022] Preferably, the reaction selectivity of 2-methyl-6-acylnaphthalene in step (3) is 90-95%.

[0023] Therefore, the method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor using the above structure has the following beneficial effects:

[0024] (1) The present invention uses a micro-mixer and a reactor coupled to a reactor to continuously synthesize acyl naphthalene, deeply combining the reaction mechanism of Friedel-Crafts acylation of 2-methylnaphthalene with the advantages of a micro-mixer and a continuous tank reactor, and improves the selectivity and yield of 2-methyl-6-acyl naphthalene by reducing the generation of kinetically controlled products and increasing the generation of thermodynamic products.

[0025] (2) The micro mixer used in the present invention has the characteristics of high mass and heat transfer efficiency. The material can quickly transfer heat under continuous flow, avoiding local overheating in batch reactions and achieving precise temperature control of the reaction. For this reaction, the micro mixer is used to increase the mixing speed (millisecond level) and the mixing reaction temperature (relative to low-temperature mixing), increase the chemical reaction rate, and greatly reduce the reaction time.

[0026] (3) The present invention improves the mixing method of the acylation liquid and the raw material liquid. The total reaction liquid can quickly enter the high temperature zone for reaction. After coupling with the kettle reactor, a higher temperature reaction is carried out. The operation is simple and the cost is low. The increase in the overall reaction temperature can further improve the reaction selectivity.

[0027] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0028] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0029] Example 1

[0030] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0031] (1) Preparation of acylation solution: Place a stirring container in a thermostatic bath, add 600 g of nitrobenzene, then add 200 g (1.5 mol) of anhydrous aluminum chloride, heat and stir at 45-55° C. for 1 hour to fully dissolve, and filter to obtain a clear and uniform solution, i.e., the acylation solution. The mass ratio of nitrobenzene to anhydrous aluminum chloride is 3:1.

[0032] (2) Preparation of raw material solution: At room temperature, 350 g of nitrobenzene, then 142 g of 2-methylnaphthalene (1.0 mol), and then 120 g (1.3 mol) of acyl chloride were added into a container and mixed to obtain a raw material solution. The mass ratio of nitrobenzene, 2-methylnaphthalene and acyl chloride was 175:71:60, and the acyl chloride was propionyl chloride.

[0033] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3=1:1.3:1.5). The two materials were injected into a three-way micro mixer (internal volume of 15L, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, a total reaction liquid was obtained. The total reaction liquid flowed out from the channel outlet of the micro mixer, wherein the temperature of the micro mixer was controlled at 15°C in a thermostatic bath, and flowed into a multi-reactor series reactor. The reaction was stirred in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors was 120min. The temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid flowing out of the multi-reactor series reactor was hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity was 93.0%, the yield was 86.7%, and the purity was 98.0%.

[0034] Example 2

[0035] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0036] (1) Preparation of acylation solution: same as in Example 1.

[0037] (2) Preparation of raw material solution: same as in Example 1.

[0038] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1:1.1:1.25). The two materials were injected into a three-way micro mixer (internal volume of 15uL, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, a total reaction liquid was obtained. The total reaction liquid flowed out from the channel outlet of the micro mixer, wherein the temperature of the micro mixer was controlled at 10°C in a thermostatic bath, and flowed into a multi-reactor series reactor. The reaction was stirred in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors was 120min. The temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid flowing out of the multi-reactor series reactor was hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity was 90.5%, the yield was 84.4%, and the purity was 98.0%.

[0039] Example 3

[0040] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0041] (1) Preparation of acylation solution: same as in Example 1.

[0042] (2) Preparation of raw material solution: same as in Example 1.

[0043] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1:1.3:1.5). The two materials were injected into a three-way micro mixer (internal volume of 15L, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, a total reaction liquid was obtained. The total reaction liquid flowed out from the micro mixer channel outlet, wherein the micro mixer was controlled at a temperature of 15°C in a thermostatic bath, and flowed into a multi-kettle series reactor. The reaction was stirred in the multi-kettle series reactor. The total residence time after passing through 2-3 reactors was 180min. The temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid flowing out of the multi-kettle series reactor was hydrolyzed and rectified to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity was 92.0%, the yield was 85.5%, and the purity was 98.0%.

[0044] Comparative Example 1

[0045] A method for continuously synthesizing acyl naphthalene by coupling a microchannel reactor with a reaction kettle comprises the following steps:

[0046] (1) Preparation of acylation solution: same as in Example 1.

[0047] (2) Preparation of raw material solution: same as in Example 1.

[0048] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1:1.3:1.5). The two materials are injected into a three-way mixer with an inner diameter of 200×200um through a syringe for mixing, and then enter a microchannel reactor with an inner diameter of 200×200um. After 5 hours, the three-way mixer and the microchannel reactor are placed in a thermostatic bath to control the temperature to 0°C. The total reaction liquid flows into a multi-reactor series reactor, and is stirred for reaction in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors is 120min. The temperature of the reactor is controlled to be 40°C and the pressure is normal. The acylation reaction liquid flowing out of the multi-reactor series reactor is hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene, and the reaction selectivity is 89.5%, the yield is 83.7%, and the purity is 98.0%.

[0049] Comparative Example 2

[0050] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0051] (1) Preparation of acylation solution: Place a container equipped with a stirrer in a thermostatic bath, add 600 g of nitrobenzene, then add 200 g (1.5 mol) of anhydrous aluminum chloride, heat and stir at 45-55°C for 1 hour to fully dissolve, then add 120 g (1.3 mol) of acyl chloride at 5°C, and filter to obtain a clear and uniform solution. The mass ratio of nitrobenzene, acyl chloride and anhydrous aluminum chloride is 15:5:3; the acyl chloride is propionyl chloride.

[0052] (2) Preparation of raw material liquid: At room temperature, 350 g of nitrobenzene and then 142 g of 2-methylnaphthalene (1.0 mol) were added into a container and mixed to obtain a raw material liquid. The mass ratio of nitrobenzene to 2-methylnaphthalene was 175:71.

[0053] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 455-465 g / h, and the flow rate of the raw material liquid was 240-250 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3=1:1.3:1.5). The two materials were injected into a three-way micro mixer (internal volume of 15uL, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, a total reaction liquid was obtained. The total reaction liquid flowed out from the channel outlet of the micro mixer, wherein the temperature of the micro mixer was controlled at 10°C in a thermostatic bath, and flowed into a multi-reactor series reactor. The reaction was stirred in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors was 120min. The temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid flowing out of the multi-reactor series reactor was hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity was 88.0%, the yield was 81.5%, and the purity was 98.0%.

[0054] Comparative Example 3

[0055] A method for continuously synthesizing acyl naphthalene by coupling a microchannel reactor with a reaction kettle comprises the following steps:

[0056] (1) Preparation of acylation solution: Place a container equipped with a stirrer in a thermostatic bath, add 600 g of nitrobenzene, then add 200 g (1.5 mol) of anhydrous aluminum chloride, heat and stir at 45-55°C for 1 hour to fully dissolve, then add 120 g (1.3 mol) of acyl chloride at 5°C, and filter to obtain a clear and uniform solution. The mass ratio of nitrobenzene, acyl chloride and anhydrous aluminum chloride is 15:5:3; the acyl chloride is propionyl chloride.

[0057] (2) Preparation of raw material solution: At room temperature, 350 g of nitrobenzene and then 142 g of 2-methylnaphthalene (1.0 mol) were added into a container, and the raw material solution was obtained after mixing. The mass ratio of nitrobenzene, 2-methylnaphthalene and acyl chloride was 175:71.

[0058] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 455-465 g / h, and the flow rate of the raw material liquid was 240-250 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1:1.3:1.5). The two materials are injected into a three-way mixer with an inner diameter of 200×200um through a syringe for mixing, and then enter a microchannel reactor with an inner diameter of 200×200um for reaction. After 5 hours, the three-way mixer and the microchannel reactor are placed in a thermostatic bath to control the temperature to 0°C. The total reaction liquid flows into a multi-reactor series reactor, and is stirred for reaction in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors is 120min. The temperature of the reactor is controlled to be 40°C and the pressure is normal. The acylation reaction liquid flowing out of the multi-reactor series reactor is hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity is 85.6%, the yield is 79.2%, and the purity is 98.0%.

[0059] Comparative Example 4

[0060] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0061] (1) Preparation of acylation solution: same as in Example 1.

[0062] (2) Preparation of raw material solution: same as in Example 1.

[0063] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3=1:1.3:1.5). The two materials were injected into a three-way micro mixer (internal volume of 15L, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, the total reaction liquid was discharged from the channel outlet of the micro mixer, wherein the temperature of the micro mixer was controlled at 0°C in a thermostatic bath. The total reaction liquid flowed into a multi-reactor series reactor, and was stirred for reaction in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors was 120min. The temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid discharged from the multi-reactor series reactor was hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene, with a reaction selectivity of 89.0%, a yield of 83.5%, and a purity of 98.0%.

[0064] Comparative Example 5

[0065] A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor comprises the following steps:

[0066] (1) Preparation of acylation solution: same as in Example 1.

[0067] (2) Preparation of raw material solution: same as in Example 1.

[0068] (3) Acylation reaction: The raw material liquid and the acylation liquid were drawn separately by metering pumps, wherein the flow rate of the acylation liquid was 395-405 g / h, and the flow rate of the raw material liquid was 300-310 g / h (i.e., according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1:1.3:1.5). The two materials were injected into a three-way micro mixer (internal volume of 15L, mixing channel size of 45×200um) through a syringe for mixing. After mixing for 100ms, a total reaction liquid was obtained, and the total reaction liquid flowed out from the channel outlet of the micro mixer, wherein the temperature of the micro mixer was controlled at 15°C in a thermostatic bath. The total reaction liquid flowed into a multi-reactor series reactor, and was stirred and reacted in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors was 60min, and the temperature of the reactor was controlled at 40°C and normal pressure. The acylation reaction liquid flowing out of the multi-reactor series reactor was hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene, with a reaction selectivity of 85.0%, a yield of 79.2%, and a purity of 98.0%.

[0069] The improved methods and acylation reaction effects of Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0070]

[0071]

[0072] As can be seen from Table 1, the specific formulation and specific reaction apparatus used in Examples 1-3 enable the reaction selectivity of 2-methyl-6-acylnaphthalene to exceed 90%, thereby reducing the generation of by-products.

[0073] Therefore, the present invention adopts a method for continuously synthesizing acyl naphthalene by coupling a micro mixer and a reactor of the above structure, and adopts a micro mixer and a reactor coupled reactor to continuously synthesize acyl naphthalene. The use of the micro mixer in the Friedel-Crafts acylation reaction of 2-methylnaphthalene increases the temperature when the two materials are mixed, greatly shortens the residence time of the materials during continuous mixing, and reduces the large pressure drop problem caused by the materials by millisecond-level mixing. The present invention combines the reaction mechanism with the coupling of a continuous tank reactor, and reacts at a high temperature for a long time in the reactor to form more main products (2-methyl-6-acyl naphthalene) in thermodynamic equilibrium. The process has good economy and practicability, excellent reaction effect, and no obvious amplification effect, providing a solid foundation for industrial amplification.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for continuously synthesizing acyl naphthalene by coupling a micro mixer with a reactor, characterized in that: The following steps are involved: (1) Preparation of acylation solution: Place a stirring container in a thermostatic bath, add 600 g of nitrobenzene, then add 200 g of anhydrous aluminum chloride, heat and stir at 45-55° C. for 1 hour to fully dissolve, and filter to obtain a clear and uniform solution, i.e., the acylation solution; (2) Preparation of the raw material solution: At room temperature, 350 g of nitrobenzene, 142 g of 2-methylnaphthalene, and 120 g of propionyl chloride were added to a container, and the mixture was mixed to obtain a raw material solution; (3) Acylation reaction: The raw material liquid and the acylation liquid are sucked separately by a metering pump, wherein the flow rate of the acylation liquid is 395-405 g / h, and the flow rate of the raw material liquid is 300-310 g / h. The two materials are injected into a three-way micro mixer through a syringe according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3=1:1.3:1.5 for mixing. After mixing for 100 ms, a total reaction liquid is obtained. The total reaction liquid flows out from the channel outlet of the micro mixer, wherein the temperature of the micro mixer is controlled at 15°C in a thermostatic bath, and flows into a multi-reactor series reactor. The reaction is stirred in the multi-reactor series reactor. The total residence time after passing through 2-3 reactors is 120 min. The temperature of the reactor is controlled at 40°C and atmospheric pressure. The acylation reaction liquid flowing out of the multi-reactor series reactor is hydrolyzed and distilled to obtain 2-methyl-6-propionylnaphthalene. The reaction selectivity is 93.0%, the yield is 86.7%, and the purity is 98.0%.

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