Acylation solution and process for continuously synthesizing acylnaphthalene using the acylation solution

Abstract

The embodiments of the present application propose an acylation liquid and a process method for continuously synthesizing acylnaphthalenes using the acylation liquid, which belongs to the field of chemical industrial synthesis technology, and includes the steps of preparing an acylation liquid using a preparation system, mixing the acylation liquid with a raw material liquid containing 2-methylnaphthalene in a ratio of 2-methylnaphthalene:acylating agent:Lewis catalyst of 1:1.3:1.5 to form an acylation reaction liquid, which is sequentially introduced into a microchannel reactor and a kettle reactor in which multiple kettle reactors are connected in series to undergo acylation reaction, and then carrying out hydrolysis, rectification and crystallization to continuously synthesize acylnaphthalenes.

Description

Technical Field

[0001] <Cross-reference to Related Applications> This application is filed based on Chinese patents with application numbers 202111075055.5, filing date September 14, 2021; 202111093577.8, filing date September 17, 2021; 202210095938.0, filing date January 26, 2022; 202111638857.2, filing date December 29, 2021; 202210530956.7, filing date May 16, 2022; and 202210135569.3, filing date February 14, 2022, and claims the priority of these 6 Chinese patent applications. The entire contents of these 6 Chinese patent applications are hereby incorporated by reference into this application.

[0002] This application relates to the field of chemical industrial synthesis technology. Specifically, it relates to an acylating solution and a process method for continuously synthesizing acylnaphthalene using the acylating solution.

Background Art

[0003] 2,6-Naphthalenedicarboxylic acid is an important monomer for polyethylene naphthalate (PEN), a special high-grade polyester. It is also a crucial monomer for synthesizing various high-performance polyethylene naphthalates, polyurethanes, and liquid crystal polyester resins. In particular, polyethylene naphthalate (PEN) obtained by reacting with ethylene glycol is superior to polyethylene terephthalate (PET), which is currently widely used, in terms of physicochemical properties and other aspects, and has prospects for extensive applications in fields such as fibers, films, packaging containers, and electronic components. The industrial production methods of 2,6-naphthalenedicarboxylic acid (2,6-NDCA) can be divided into two types. One is the conventional process method using petroleum-based benzene compounds as raw materials. For example, BP-Amoco, Mitsubishi Chemical in Japan, Chevron, and Optatech in Finland use this method. This method has many steps and high production costs. The other is the improved process method using coal-based naphthalene compounds as raw materials. Using naphthalene and methylnaphthalene as raw materials, 2,6-dimethylnaphthalene (2,6-DMN) is synthesized, and DMN products can be produced in one step. Then, 2,6-DMN can be obtained through isomerization and separation and purification. Exxon-Mobil uses this method. This method has simple steps and relatively low costs.

[0004] The industrialization route and semi-industrialization route are as follows. (1) Alkylate, cyclize, dehydrogenate, and isomerize orthoxylene to produce 2,6-dimethylnaphthalene, and then oxidize it to produce naphthalenedicarboxylic acid. This reaction has a complex process, with five steps, a long synthesis route, high technical requirements, strict reaction conditions, and a total yield of about 36%. (2) Naphthalene is liquid-phase alkylated to produce 2,6-diisopropylnaphthalene, and then oxidized to produce 2,6-naphthalenedicarboxylic acid. Naphthalene is reacted with propylene under the catalytic action of acid-treated mordenite zeolite, and the reacted mixture is rectified to obtain crude dialkylnaphthalene (a mixture of isomers), which is further separated to obtain 2,6-dialkylnaphthalene, and then air liquid-phase oxidized to produce 2,6-naphthalenedicarboxylic acid. This method has many steps in the reaction process, and alkylation and purification are the key points of the technology. Currently, there are mainly two industrial synthesis routes for 2,6-NDCA. One is to acetylate 2-methylnaphthalene to obtain 2-methyl-6-acetylnaphthalene, and then further oxidize it to produce 2,6-NDCA. The other is to oxidize 2,6-dialkylnaphthalene to produce 2,6-NDCA, including liquid-phase catalytic oxidation of 2,6-dimethylnaphthalene, 2,6-diethylnaphthalene, and 2,6-diisopropylnaphthalene. The former has the advantages of high yield and selectivity and relatively easy process, but the catalyst used in the production of 2-methyl-6-acetylnaphthalene is expensive, difficult to recover, high in cost, and the reactants have high toxicity and large pollution, so the production scale is small. The latter, after alkylating naphthalene, uses a Co-Mn-Br catalyst system, with lower fatty acids as solvents, reacts in a titanium reactor, with a temperature of about 200 °C and a pressure of about 3.0 MPa. The reaction conditions are mild and easy to control.

[0005] Using 2-methylnaphthalene as a raw material, after generating 2-methyl-6-propionylnaphthalene through an acylation reaction, it is oxidized to obtain 2,6-naphthalenedicarboxylic acid. This synthesis method has abundant raw material sources, few side reactions, and the product is easy to purify. It is much easier compared to the synthesis route of oxidizing 2,6-dialkylnaphthalene to produce 2,6-naphthalenedicarboxylic acid. In contrast, in the acylation reaction using 2-methylnaphthalene as a raw material, a highly stable and highly homogeneous acylation solution is extremely important. In the acylation reaction, a Lewis acid is used as a catalyst to generate an electrophilic complex, which is likely to enter the para position of the acylatable substance, so the selectivity of the reaction is high. However, due to the high activity of the catalyst and the acylating agent, they are likely to react with water and deteriorate. When contacting with humid air, a large amount of white acidic mist is generated, and precipitation occurs after the catalytic reaction. Therefore, the acylation solution is unstable in air. Also, the reaction needs to be carried out in a homogeneous phase, and any undissolved catalyst or particles generated by deterioration in the solution will affect the efficiency of the acylation solution reaction and the final yield and purity of the product.

[0006] In the prior art, 2-methylnaphthalene is used as a raw material, propionyl chloride is used as an acylating agent, aluminum trichloride is used as a catalyst, and nitrobenzene is used as a solvent. The Friedel-Crafts acylation reaction is carried out at normal temperature and pressure to prepare 2-methyl-6-propionylnaphthalene. After the acylation reaction is completed, the reaction needs to be hydrolyzed and quenched, and the pH of the oil phase needs to be hydrolyzed to 6-7. Furthermore, highly pure 2-methyl-6-propionylnaphthalene is obtained by purification methods such as vacuum rectification, rectification, and recrystallization. The reaction temperature of this reaction has certain characteristics. The two materials need to be first mixed and reacted at a low temperature, and then the temperature is raised and reacted for a certain period of time. The purpose of the low-temperature mixing has two aspects. One is that when the two materials are mixed, heat is released violently, and it is necessary to transfer heat at a low temperature. The other is that the acylation reaction in the low-temperature area is affected by kinetics, and 60%-70% of the raw materials (2-methylnaphthalene) have reacted. The current acylation reaction uses an intermittent kettle reactor or a continuous microchannel reactor. However, the kettle reactor has a small heat exchange area, is difficult to control the reaction temperature, the residence times do not match, and the product quality is not easy to stabilize. In contrast, the microchannel reactor has a risk of clogging, a high expansion cost, and a complex operation. Therefore, the disadvantages of using an intermittent kettle reactor for the acylation reaction are that the heat exchange area is small, it is difficult to control the reaction temperature, the reaction time is long, the residence times do not match, the product quality is not easy to stabilize, and the yield of the product is low. The disadvantages of using a continuous microchannel reactor for the acylation reaction are that there is a risk of clogging, a high expansion cost, and a complex operation. The reaction temperature of this reaction has certain characteristics. The two materials, namely the acylation liquid and the raw material liquid, need to be first mixed and reacted at a low temperature, and then the temperature is raised and reacted for a certain period of time. The conventional devices do not fully meet the requirements of the characteristics of this reaction.

[0007] In addition, in this reaction, after the acylation reaction, the hydrolysis process of the acylation reaction solution containing 2-methyl-6-acylnaphthalene plays an important role in obtaining 2-methyl-6-acylnaphthalene with high purity and high yield. Specifically, hydrolysis can stop the acylation reaction, hydrolyze aluminum trichloride and the acylating agent, dissolve the HCl gas generated during the reaction, and retain the generated 2-methyl-6-acylnaphthalene in the oil phase. By raising the pH value of the oil phase after hydrolysis to 6 - 7, the influence of acidity on the product can be eliminated. During vacuum rectification and temperature-raising purification, the acyl group is prone to oxidation, condensation, and asphaltenization in weak acid, resulting in the formation of tar and a decrease in the yield and purity of the product. Therefore, when hydrolyzing the acylation reaction solution, it is necessary to perform synchronous continuous hydrolysis to ensure high-purity 2-methyl-6-propionylnaphthalene.

[0008] When hydrolyzing the acylation reaction solution in the prior art, there are the following three solutions. The first is to first flow the acylation reaction solution into a mixer for storage, mix it with water, and then flow it into the microchannel reactor in the subsequent hydrolysis section. However, the simultaneous progress of the acylation reaction and the hydrolysis reaction cannot be achieved, and when the acylation reaction solution contacts water, a large amount of heat is released and the temperature cannot be quickly lowered. The second is to pass the product obtained from the reaction through a hydrolysis reactor, put the reaction mixture into a large beaker containing ice, continuously stir it mechanically during the process, add rectified water after putting it in, and continue to stir for 30 minutes to completely hydrolyze the acylating product. This solution is an intermittent hydrolysis reaction, which takes a long time, has a complicated operation, and the hydrolysis effect is mediocre. The third is to add the acylation reaction solution to an ethanol aqueous solution for quenching, stratify to obtain the nitrobenzene phase, perform vacuum rectification on the nitrobenzene phase to collect the solvent nitrobenzene, and obtain the crude product 2-methyl-6-acetylnaphthalene. This solution is ethanol aqueous solution hydrolysis, and its advantages are not prominent.

[0009] In short, the prior art has the following drawbacks. It is an intermittent or semi - continuous hydrolysis, and synchronous continuous hydrolysis has not been achieved. There is a certain time interval between obtaining the acylation reaction solution and performing the hydrolysis reaction. The acylation reaction solution cannot be hydrolyzed promptly. When left standing, it is likely to cause a hydrolysis reaction with water in the air, and there is also a leakage of HCl gas, polluting the air. The hydrolysis reaction generates an Al(OH)3 emulsion. When using a micro - channel reactor for the hydrolysis reaction, the acylation reaction solution may block the pipeline when contacting water. The hydrolysis reaction is an exothermic reaction. Due to the heat released instantaneously, the hydrolysis section generates pressure in the pipeline and there is also volatilization of a small amount of acidic gas. The liquid obtained by hydrolysis has a large volume and is turbid, making liquid - separation operation difficult and time - consuming.

[0010] Finally, the wastewater after the acylation reaction is mainly highly toxic, high - salinity, and difficult - to - biodegrade organic wastewater (Table 1), and its treatment is extremely difficult. That is, in the current situation where supervision and management are becoming increasingly strict day by day, the difficult - to - biodegrade organic wastewater generated by the acylation reaction is the main point restricting the industrialization of the Friedel - Crafts acylation reaction.

[0011] JPEG0007702429000001.jpg26170

[0012] Therefore, there is a sufficient need to research and develop treatment technologies for the difficult - to - biodegrade organic wastewater generated by the acylation reaction.

Summary of the Invention

Problems to be Solved by the Invention

[0013] This application aims to solve to some extent one of the technical problems in the related art, and proposes an acylation liquid and a process method for continuously synthesizing acylnaphthalene using the acylation liquid. In the prior art, the acylation liquid is not stable and has poor uniformity, and the reaction efficiency of producing acylnaphthalene using the acylation liquid is low, the consumption is high, the hydrolysis process is unstable and the pipeline is easily blocked, and the acylnaphthalene yield is low and the purity is low. In view of the technical defects, a new acylation liquid is proposed. Using the acylation liquid, the reaction rate of synthesizing acylnaphthalene and the stability of hydrolysis are improved, thereby improving the yield of acylnaphthalene. In addition, the embodiments of this application also treat the hydrolysis wastewater after synthesizing acylnaphthalene with the acylation liquid, and realize green production considering the environment.

Means for Solving the Problem

[0014] In view of this, the embodiments of this application propose an acylation liquid prepared using a preparation system. The preparation system includes a kettle body that defines a first chamber and has a first inlet, a second inlet, a stirring port, and a liquid discharge port communicating with the first chamber, an inlet cover removably sealed and mounted on the first inlet, an inlet pump sealingly connected to the second inlet to add an acylating agent into the second inlet, a stirrer, a part of the stirrer is sealingly inserted into the stirring port, the stirrer includes a stirring shaft and stirring blades, the stirring blades are provided on the stirring shaft, and at least a part of the stirring shaft and each of the stirring blades are provided in the first chamber.

[0015] Preparing the acylation liquid using the preparation system includes a: weighing a Lewis catalyst under the protection of an inert gas; b: adding a solvent and the Lewis catalyst weighed in step a into the first chamber through the first inlet, and uniformly stirring using the stirrer to obtain a mixed solution; c: A step of adding an acylating agent to the mixed solution obtained in step b using the input pump to obtain an acylated solution, and the method includes this step.

[0016] In some embodiments, the kettle body is a first housing, the liquid discharge port is provided in the first housing, and the upper end of the first housing is open; a top cover, the top cover is sealingly mounted on the first housing, the first chamber is defined by the first housing and the top cover, and the first input port, the second input port, and the stirring port are all provided on the top cover; and a jacket attached to the first housing and having a first heat exchange medium inlet for the inflow of the heat exchange medium and a first heat exchange medium outlet for the outflow of the heat exchange medium.

[0017] In some embodiments, the preparation system is a heating device, the heating device has a second heat exchange medium inlet and a second heat exchange medium outlet, the first heat exchange medium outlet is connected to the second heat exchange medium inlet, and the first heat exchange medium inlet is connected to the second heat exchange medium outlet; a temperature sensor, the kettle body has a temperature detection port communicating with the first chamber, a part of the temperature sensor is sealingly inserted into the temperature detection port, and the detection side of the temperature sensor is provided in the first chamber; and a controller connected to each of the heating device and the temperature sensor to control the heating device based on the temperature detected by the temperature sensor.

[0018] In some embodiments, the preparation system further includes a suction filtration device, and the suction filtration device A filtration device, wherein the filtration device includes a second housing and a filtration film, a second chamber is defined by the second housing, the filtration film is provided in the second chamber, the filtration film partitions the second chamber into a first part and a second part, the second housing is provided with a filtration device inlet and a filtration device outlet communicating with the second chamber, the filtration device inlet is provided corresponding to the first part, the filtration device outlet is provided corresponding to the second part, and the filtration device inlet is connected to the liquid discharge port. A liquid storage tank, wherein the liquid storage tank includes a third housing, a third chamber is defined by the third housing, the third housing is provided with a liquid storage tank inlet and a liquid storage tank outlet, and the liquid storage tank inlet communicates with the filtration device outlet. A vacuum exhaust pump, wherein the vacuum exhaust pump has a first vacuum exhaust port, the third housing is provided with a second vacuum exhaust port communicating with the third chamber, and the first vacuum exhaust port communicates with the second vacuum exhaust port.

[0019] In some embodiments, the first housing, the second housing, and the third housing are of an integral structure, the liquid discharge port is provided at the bottom of the first housing, the filtration device inlet is provided at the top of the second housing, the filtration device is provided at the bottom of the kettle body, the outlet of the filtration device is provided at the bottom of the second housing, the inlet of the liquid storage tank is provided at the top of the third housing, and the liquid storage tank is provided at the bottom of the filtration device.

[0020] In some embodiments, the solvent is nitrobenzene, and step b is First, add the nitrobenzene into the first chamber through the first inlet. Next, add the Lewis catalyst weighed in step a into the nitrobenzene. Then, heat the nitrobenzene and the Lewis catalyst to 50°C to 60°C using a heat exchange medium and stir at 200 rpm to 400 rpm using the stirrer.

[0021] In some embodiments, preparing the acylating solution using a preparation system further includes step d, and under an inert gas atmosphere, using the suction filtration device to perform a suction filtration process on the acylating solution obtained in step c to obtain a filtered acylating solution.

[0022] In some embodiments, in step c, the addition rate of the acylating agent is 3 to 10 drops per second, and the stirring rate of the stirrer is 200 rpm to 400 rpm.

[0023] In some embodiments, the molar mass ratio of the acylating agent to the Lewis catalyst is (1.1 to 1.5):(1.3 to 1.7), and / or the molar mass ratio of the Lewis catalyst to the solvent is (1.3 to 1.7):5.

[0024] In some embodiments, a method for continuously synthesizing acylnaphthalene is proposed, and synthesizing using the acylating solution described in any one of the above is S1: A step of mixing a raw material solution containing 2-methylnaphthalene with the acylating solution described in any one of the above embodiments to form an acylation reaction solution in a ratio of the 2-methylnaphthalene: the acylating agent: the Lewis catalyst of 1:1.3:1.5; S2: A step of allowing the acylation reaction solution to enter a microchannel reactor and a tank reactor in which a plurality of tanks are connected in series to perform an acylation reaction and simultaneously perform hydrolysis, and obtaining 2-methyl-6-propionylnaphthalene by subsequent rectification and crystallization.

[0025] In some embodiments, a plurality of the microchannel reactors are provided and connected in parallel with each other.

[0026] In some embodiments, in step S1, the raw material solution and the acylating solution are injected into a three-way mixer through a syringe and mixed.

[0027] In some embodiments, the three-way mixer is a T-shaped mixer or a Y-shaped mixer.

[0028] In some embodiments, the three-way mixer and the microchannel reactor are arranged in a first thermostat, and the temperature is controlled at -5 to 0 °C. The kettle reactor is arranged in a second thermostat, and the temperature is controlled at 30 to 50 °C.

[0029] In some embodiments, two to four kettle reactors are provided and connected in series with each other.

[0030] In some embodiments, the total residence time of the acylation reaction solution in the kettle reactor is 50 to 80 min.

[0031] In some embodiments, the materials of both the microchannel reactor and the kettle reactor are strong acid corrosion-resistant materials.

[0032] In some embodiments, the inner diameter of the microchannel reactor is 0.5 to 3.175 millimeters.

[0033] In some embodiments, the acylating agent in the acylating solution is any one of propionyl chloride, acetyl chloride, acetic anhydride, and propionic anhydride.

[0034] In some embodiments, in the hydrolysis method, in the hydrolysis section, before passing the acylation reaction solution after the acylation reaction through the hydrolysis section, water is passed through the aqueous phase pipeline of the hydrolysis section. When the water flows out from the outlet of the hydrolysis section, the acylation reaction solution is further passed through the oil phase pipeline of the hydrolysis section, rapidly mixed with water in a low-temperature cold bath, and then enters a tubular reactor for hydrolysis reaction. The mixed solution after hydrolysis flows out from the outlet of the tubular reactor, and a liquid separator is used to collect the mixed solution for separation of the aqueous phase and the oil phase. At this stage, water always maintains a flowing state until the mixed solution is completely discharged, realizing the synchronous progress of the hydrolysis reaction and the acylation reaction.

[0035] In some embodiments, the water injection pump is started to pass water through the water phase pipeline in the hydrolysis section, so as to control the water flow rate in the water phase pipeline to be 3 - 15 mL / min.

[0036] In some embodiments, the acylation reaction solution passes through the check valve in the pipeline and directly enters the oil phase pipeline in the hydrolysis section.

[0037] In some embodiments, the check valve is a stainless steel ferrule check valve, and the material of the internal flow path is polytetrafluoroethylene.

[0038] In some embodiments, the temperature of the low-temperature cold bath is 0 - 20 °C.

[0039] In some embodiments, the reaction temperature of the tubular reactor is 30 - 40 °C.

[0040] In some embodiments, the liquid distributor includes a container, a stirring device, a supply port, a discharge port, and an exhaust port. The stirring device enters the container and is connected to an external speed reducer for driving. The discharge port communicates with the bottom end of the container. The supply port and the exhaust port both communicate with the upper end of the container. The supply port is connected to the outlet of the tubular reactor in the hydrolysis section through a pipeline. The exhaust port is connected to an exhaust pump through a pipeline. Control valves are provided at the supply port, the discharge port, and the exhaust port.

[0041] In some embodiments, a hydrolysis reaction is carried out in the tubular reactor in the hydrolysis section, and the exhaust pump draws out the generated exhaust gas.

[0042] In some embodiments, the method for continuously synthesizing acylnaphthalene further includes step S3, the treatment of acylation wastewater. Specifically, (1) adjusting the pH of the water phase separated by the liquid distributor to be alkaline to obtain a suspension containing aluminum hydroxide precipitate, and filtering the suspension to obtain aluminum hydroxide filter cake and filtrate; (2) After adjusting the pH of the filtrate to acidic, transfer it to an extraction solvent, stir, let it stand, and obtain a stratified raffinate phase and an extraction phase; (3) Biochemically treat the raffinate phase and discharge it after reaching the standard; (4) After subjecting the extraction phase to rectification separation, obtain nitrobenzene and the extraction solvent, reuse the nitrobenzene as an organic solvent, and use the extraction solvent again for extracting the filtrate; (5) Add the filter cake to concentrated hydrochloric acid, heat to dissolve it, add an auxiliary agent, and then polymerize to obtain polyaluminum chloride.

[0043] In some embodiments, in step (1), the method of adjusting the pH of the aqueous phase separated by the liquid separator to alkaline includes adjusting the pH of the aqueous phase to 8 - 10 using an alkaline raw material, and the alkaline raw material is one or more of sodium hydroxide, potassium hydroxide, or liquefied ammonia.

[0044] In some embodiments, in step (2), the method of adjusting the pH of the filtrate to acidic includes adjusting the pH of the filtrate to 2 - 3 using an acid, and the acid is one or more of hydrochloric acid, nitric acid, or sulfuric acid.

[0045] In some embodiments, in step (2), the extraction solvent is a non - polar organic solvent, and the volume ratio of the extraction solvent to the filtrate is 0.5 - 5:1.

[0046] In some embodiments, the extraction solvent is at least one of normal heptane, normal octane, normal hexane, benzene, toluene, xylene, and carbon tetrachloride.

[0047] In some embodiments, in step (3), the biochemical treatment uses the activated sludge method, in step (5), the temperature of heating and dissolving is 40 - 50°C, and the weight ratio of the filter cake to concentrated hydrochloric acid is 0.5 - 2.5:1.

[0048] In some embodiments, in step (5), the addition amount of the auxiliary agent is 2 to 10 wt% of the dry weight of the filter cake, and the auxiliary agent is calcium aluminate or / and magnesium aluminate.

[0049] In some embodiments, the rectification comprises (1) feeding the oil phase from the middle part of the first rectification column into the first rectification column for rectification, evaporating the light fraction from the top of the column, condensing it and then recovering it, and the bottom liquid flowing out from the bottom of the column; and (2) pumping the bottom liquid of step (1) into the second rectification column while it is hot for further rectification, evaporating the light fraction of the second rectification column from the top of the column, condensing it and then collecting it, collecting the product from the side line of the second rectification column, the bottom high-boiling component entering the bottom of the column, heating it with the bottom reboiler, and then pumping the bottom high-boiling component into the bottom material collection tank while it is hot.

[0050] In some embodiments, the pressure of the first rectification column is 0.05 KPa to 210 KPa, and the reflux ratio is (1 to 2):1.

[0051] In some embodiments, the condensation temperature of the first rectification column is 10 to 220 °C.

[0052] In some embodiments, the pressure of the second rectification column is 0.05 KPa to 210 KPa, and the reflux ratio is (5 to 210):1.

[0053] In some embodiments, the condensation temperature of the second rectification column is 50 to 290 °C.

[0054] In some embodiments, the 2-methylnaphthalene is extracted from wash oil, and the purity is 99.0 to 99.9%. The extraction method is I Rectifying and separating the wash oil to obtain a methylnaphthalene concentrated fraction, II Passing the methylnaphthalene concentrated fraction through an azeotropic rectification column for azeotropic rectification to obtain an azeotropic distillate, III Passing the azeotropic distillate through a separator to obtain a 2-methylnaphthalene crude product, IV The crude 2-methylnaphthalene product is passed through a plurality of batch melting crystallizers installed in parallel connection to crystallize and purify 2-methylnaphthalene.

Advantages of the Invention

[0055] The acylation solution prepared and obtained in the examples of this application has good solution uniformity, high stability, can be used in a microchannel reactor, and when an acylation reaction is carried out using the acylation solution to produce 2-methyl-6-propionylnaphthalene, the acylation reaction solution is immediately connected to the hydrolysis section, and synchronous hydrolysis is carried out continuously and stably, improving the equilibrium rate of the material and having no risk of pipeline blockage. The liquid obtained by hydrolysis can directly enter the liquid separator, and liquid separation is carried out synchronously. The oil phase can be easily collected, and the generated exhaust gas can be extracted from the exhaust port at the upper end of the liquid separator. Also, the pH value of the oil phase obtained by synchronous hydrolysis is 6-7, meeting the requirements for purification.

Brief Description of the Drawings

[0056] The above and / or additional aspects and advantages of this application will become clear and easier to understand from the description of the examples with reference to the following drawings.

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Embodiments for Carrying Out the Invention

[0057] To better understand the above objects, features and advantages of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments. Unless there is a contradiction, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0058] The following description includes details for a full understanding of the present application, however, the present application can be implemented in other ways different from the ways described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0059] As shown in FIGS. 1 to 3, a preparation system 100 for preparing an acylation solution according to an embodiment of the present application includes a kettle body 1, an inlet cover 2, a feed pump 6, and a stirrer 3. The kettle body 1 defines a first chamber 110, and the kettle body 1 has a first inlet 101, a second inlet 102, a stirring port 103, and a liquid discharge port 104 that communicate with the first chamber 110.

[0060] Optionally, each of the first inlet 101, the second inlet 102, and the stirring port 103 is provided above the liquid discharge port 104.

[0061] Thereby, the solvent and the Lewis catalyst for preparing the acylation solution can be added into the first chamber 110 through the first inlet 101, and the acylating agent can be added into the first chamber 110 through the second inlet 102.

[0062] The inlet cover 2 is removably and sealingly mounted on the first inlet 101. When it is necessary to introduce (the solvent and the Lewis catalyst) into the kettle body 1, the inlet cover 2 is removed from the first inlet 101. After the introduction is completed, the inlet cover 2 is quickly and sealingly mounted on the first inlet 101, thereby reducing the time for the solvent and the Lewis catalyst to contact the external environment and reducing the time for the first chamber 110 to be exposed to the external environment through the first inlet 101.

[0063] Since the feed pump 6 is sealingly connected to the second inlet 102, it is easy to add the acylating agent into the second inlet 102. Thereby, during the process of introducing into the first chamber 110 using the feed pump 6 and after the introduction is completed, the contact between the acylating agent and the external environment can be effectively avoided, and the first chamber 110 can be prevented from being exposed to the external environment through the second inlet 102.

[0064] A part of the stirrer 3 is sealingly inserted into the stirring port 103. The stirrer 3 includes a stirring shaft 301 and a stirring blade 302. The stirring blade 302 is provided on the stirring shaft 301, and at least a part of the stirring shaft 301 and each of the stirring blades 302 are provided in the first chamber 110.

[0065] By doing so, by using the stirrer 3, the materials in the first chamber 110 can be sufficiently stirred and mixed, the Lewis catalyst can be sufficiently dissolved, and the preparation efficiency of the acylation solution can be improved. Moreover, since a part of the stirrer 3 is sealed and inserted into the stirring port 103, during the operation of the stirrer 3, the stirring port 103 is always sealed, avoiding the exposure of the first chamber 110 to the external environment through the stirring port 103.

[0066] The method for preparing an acylation solution implemented by using the preparation system 100 for preparing the acylation solution according to the embodiment of the present application is as follows: a. A step of weighing a Lewis catalyst under the protection of an inert gas; b. A step of adding a solvent and the Lewis catalyst weighed in step a into the first chamber 110 through the first inlet 101, and stirring by using the stirrer 3 to dissolve the Lewis catalyst weighed in step a to obtain a mixed solution; c. A step of adding an acylating agent to the mixed solution obtained in step b by using the charging pump 6 and stirring by using the stirrer 3 to obtain an acylation solution.

[0067] When preparing the acylation solution of the embodiment of this application, when weighing the Lewis catalyst, it is weighed under the protection of an inert gas to effectively ensure the activity of the Lewis catalyst, without being affected by the weather or environment, and avoid the generation of acidic mist in summer when the humidity is high. In the method for preparing the acylation solution of the embodiment of this application, after weighing the Lewis catalyst in an inert environment, it is added to the solvent, the inlet cover 2 is provided, and the contact time between the Lewis catalyst and air is reduced by the liquid sealing method. Thereby, in the process of preparing the acylation solution, the contact between the Lewis catalyst, the acylating agent and water, etc. can be effectively reduced. Therefore, the stability and uniformity of the prepared acylation solution are good. In the method for preparing the acylation solution of the embodiment of this application, by the stirring of the stirrer 3, the Lewis catalyst can be dissolved in the solvent sufficiently and quickly, which is advantageous for shortening the preparation time of the acylation solution and improving the preparation efficiency of the acylation solution. The acylation solution prepared by the method for preparing the acylation solution of the embodiment of this application has good solution uniformity and high stability, can be used in a microchannel reactor, and improves the reaction efficiency.

[0068] Optionally, in step a, the Lewis catalyst is at least one selected from AlCl3, BF3, ZnCl2 or FeCl3. In the embodiment of this application, the Lewis catalyst is not particularly limited, and any Lewis catalyst that can be used in the synthesis of 2-methyl-6-propionylnaphthalene can be used to prepare the acylation solution by using the method for preparing the acylation solution of the embodiment of this application. The acylating agent is at least one selected from an acetylating agent, a propionylating agent or a butylating agent.

[0069] Optionally, the second inlet 102 is in a butted form, the second inlet 102 is sealingly connected to a pagoda joint, and the discharge pipe of the peristaltic pump is sealingly connected to the pagoda joint.

[0070] Optionally, the feed pump 6 is a peristaltic pump.

[0071] Thus, by adjusting the flow rate of the peristaltic pump, the flow rate of the acylating agent added into the first chamber 110 of the kettle body 1 can be controlled, making it easier to control the amount of the acylating agent added into the first chamber 110, and helping to further improve the stability and uniformity of the prepared acylating solution.

[0072] Optionally, the input pump 6 and the second input port 102 are connected via a first hose 600. The first hose 600 may be a polytetrafluoroethylene tube.

[0073] In some embodiments, the materials of the stirring shaft 301 and the stirring blade 302 are metal, and the stirrer 3 includes a shaft anticorrosion layer and a blade anticorrosion layer. The shaft anticorrosion layer covers a part of the stirring shaft 301, and the blade anticorrosion layer covers the stirring blade 302.

[0074] In some embodiments, the materials of the stirring shaft 301 and the stirring blade 302 are stainless steel, and the materials of the shaft anticorrosion layer and the blade anticorrosion layer are polytetrafluoroethylene.

[0075] The stirring shaft 301 and the stirring blade 302 are made of metal materials, which can effectively ensure that the stirring shaft 301 and the stirring blade 302 have sufficient structural strength. By coating the stirring shaft 301 with a shaft anticorrosion layer and coating the stirring blade 302 with a blade anticorrosion layer, it is possible to avoid the metal material parts of the stirring shaft 301 and the stirring blade 302 from contacting with the solvent, Lewis catalyst and acylating agent, not only avoiding the corrosion of the stirring shaft 301 and the stirring blade 302, but also avoiding the corrosion products from entering the acylating solution and affecting the quality of the prepared acylating solution.

[0076] Optionally, in the above step c, the addition rate of the acylating agent is 3 to 10 drops per second, and the stirring speed of the stirrer 3 is 200 rpm to 400 rpm.

[0077] In some embodiments, as shown in FIG. 2, the kettle body 1 includes a first housing 107, a top cover 108, and a jacket 109. The liquid discharge port 104 is provided in the first housing 107, and the upper end of the first housing 107 is open. The top cover 108 is sealingly attached to the first housing 107, and the first housing 107 and the top cover 108 define a first chamber 110. Each of the first inlet 101, the second inlet 102, and the stirring port 103 is provided in the top cover 108. The jacket 109 is externally fitted to the first housing 107, and the jacket 109 has a first heat exchange medium inlet 1091 for the heat exchange medium to flow in and a first heat exchange medium outlet 1092 for the heat exchange medium to flow out.

[0078] Thereby, when processing the kettle body 1, the first housing 107 and the top cover 108 can be processed independently, facilitating the processing of the kettle body 1. When performing the dissolution operation of the Lewis catalyst, the heat exchange medium can flow into the jacket 109 through the first heat exchange medium inlet 1091, perform heat exchange with the material in the first chamber 110 through the first housing 107, and then the heat exchange medium flows out of the jacket 109 through the first heat exchange medium outlet 1092. Thereby, heating of the material in the first chamber 110 is realized, and by maintaining the temperature in the first chamber 110 at a predetermined temperature suitable for the Lewis catalyst solvent, the Lewis catalyst is quickly dissolved in the solvent, thereby significantly shortening the preparation time of the acylation solution and improving the preparation efficiency of the acylation solution.

[0079] Liquids such as water and oil can be used as the heat exchange medium.

[0080] In some embodiments, the solvent is nitrobenzene, and the above step b is First, add nitrobenzene into the first chamber 110 through the first inlet 101, Next, add the Lewis catalyst weighed in step a into the nitrobenzene, Thereafter, the nitrobenzene and the Lewis catalyst are heated to 50°C to 60°C through the heat exchange medium in the jacket 109, and stirred at 200 rpm to 400 rpm using the stirrer 3 to dissolve the Lewis catalyst weighed in step a to obtain a mixed solution.

[0081] Thereby, the temperature in the first chamber 110 is maintained at a predetermined temperature suitable for the dissolution of the Lewis catalyst, and the stirring speed of the stirrer 3 is similarly maintained at a stirring speed suitable for the dissolution of the Lewis catalyst, so that the Lewis catalyst is quickly dissolved in the nitrobenzene, significantly shortening the preparation time of the acylation solution and improving the preparation efficiency of the acylation solution.

[0082] In some embodiments, the acylation solution preparation system further includes a heating device, a temperature sensor 5 and a controller. The heating device has a second heat exchange medium inlet and a second heat exchange medium outlet. The first heat exchange medium outlet 1092 is connected to the second heat exchange medium inlet, and the first heat exchange medium inlet 1091 is connected to the second heat exchange medium outlet.

[0083] The kettle body 1 has a temperature measuring port 105 communicating with the first chamber 110. A part of the temperature sensor 5 is sealed and inserted into the temperature measuring port 105, and the detection side of the temperature sensor 5 is provided in the first chamber 110. The controller is connected to each of the heating device and the temperature sensor 5, thereby facilitating the controller to control the heating device based on the temperature detected by the temperature sensor 5.

[0084] Thereby, the heat exchange medium after being heated by the heating device flows to the first heat exchange medium inlet 1091 through the second heat exchange medium outlet, the heat exchange medium flows into the jacket 109 through the first heat exchange medium inlet 1091, and the heat exchange medium in the jacket 109 is used to heat the material in the first chamber 110. Thereafter, the heat exchange medium in the jacket 109 flows out of the jacket 109 through the first heat exchange medium outlet 1092, returns to the heating device through the second heat exchange medium inlet, and is heated by the heating device, realizing the circulating flow of the heat exchange medium between the heating device and the kettle body 1.

[0085] By using the temperature sensor 5, the temperature of the material in the first chamber 110 can be detected in real time. By transmitting the temperature of the material in the first chamber 110 detected by the temperature sensor 5 to the controller, the heating device is controlled using the controller. In some embodiments, when the temperature detected by the temperature sensor 5 is higher than a predetermined temperature, the controller controls the heating device to stop heating, avoiding the material in the first chamber 110 being higher than the predetermined temperature. When the temperature detected by the temperature sensor 5 is lower than the predetermined temperature, the controller controls the heating device to start heating, avoiding the material in the first chamber 110 being lower than the predetermined temperature. Thereby, during the dissolution process of the Lewis catalyst, the temperature in the first chamber 110 is maintained at a predetermined temperature suitable for the dissolution of the Lewis catalyst, which is beneficial to improving the dissolution rate of the Lewis catalyst and improving the preparation efficiency of the acylation solution.

[0086] Optionally, the model number of the controller is DSC350.

[0087] In the above step c, the temperature of the mixed solution obtained in the above step b is 60°C or lower.

[0088] In the method for preparing the acylation solution according to the embodiment of the present application, after the Lewis catalyst is dissolved in the solvent in step b, it is not necessary to perform a process of cooling the mixed solution. The acylation agent is directly added to prepare the acylation solution, which not only reduces energy consumption, but also shortens the preparation time of the acylation solution and improves the preparation efficiency.

[0089] Of course, after the Lewis catalyst is dissolved in the solvent in step b, the acylation agent can be added into the first chamber 110 using the input pump 6, and at the same time, a heat exchange medium (for example, cooling water or coolant) can be passed into the jacket 109 through the first heat exchange medium inlet 1091 to achieve cooling of the mixed solution.

[0090] As shown in FIGS. 1 and 2, the preparation system 100 for preparing the acylation solution further includes a pH meter 4. The kettle body 1 has a pH meter port 106 communicating with the first chamber 110. A part of the pH meter 4 is sealed and inserted into the pH meter port 106, and the detection side of the pH meter 4 is provided in the first chamber 110.

[0091] Thereby, the pH of the material in the first chamber 110 can be detected in real time using the pH meter 4, which helps to improve the preparation efficiency of the acylation solution and the quality of the prepared acylation solution.

[0092] In some embodiments, the pH meter port 106 is in a lapped form. This facilitates the sealing of the pH meter port 106.

[0093] For example, as shown in FIG. 3, a glass cover 10 is provided outside the pH meter 4. The glass cover 10 has a tapered fitting surface 1001, and the fitting surface 1001 is sealingly fitted to the pH meter port 106.

[0094] Optionally, the model number of the pH meter 4 is SIN-PH6.3-5022-AL / Y.

[0095] In some embodiments, it further includes a suction filtration device. The suction filtration device includes a filtration device 7, a liquid storage tank 8, and a vacuum exhaust pump 9.

[0096] The filtration device 7 includes a second housing 701 and a filtration film 702. The second housing 701 defines a second chamber. The filtration film 702 is provided in the second chamber. The filtration film 702 divides the second chamber into a first part 7013 and a second part 7014. The second housing 701 is provided with a filtration device inlet 7011 and a filtration device outlet 7012 communicating with the second chamber. The first part 7013 is installed adjacent to the filtration device inlet 7011, and the second part 7014 is installed adjacent to the filtration device outlet 7012. The filtration device inlet 7011 is connected to the liquid discharge port 104.

[0097] The liquid storage tank 8 includes a third housing 801. The third housing 801 defines a third chamber. The third housing 801 is provided with a liquid storage tank inlet 8011 and a liquid storage tank outlet 8012. The liquid storage tank inlet 8011 communicates with the filter device outlet 7012. The vacuum exhaust pump 9 has a first vacuum exhaust port 901. The third housing 801 is provided with a second vacuum exhaust port 8013 communicating with the third chamber. The first vacuum exhaust port 901 communicates with the second vacuum exhaust port 8013.

[0098] Optionally, the method for preparing the acylating solution further includes step d. The acylating solution obtained in step c is subjected to suction filtration treatment in an inert gas atmosphere to remove solid particles. In the method for preparing the acylating solution of the present application, after the acylating solution is prepared, suction filtration treatment is performed in an inert atmosphere to remove all undissolved solid particles in the solution, further improving the uniformity of the solution. Then, a negative pressure is generated in the filter device 7 by the vacuum exhaust pump 9. The acylating solution prepared using the kettle body 1 quickly passes through the filter film 702 of the filter device 7 under the action of the negative pressure and flows into the liquid storage tank 8 for storage, thereby further improving the overall preparation efficiency of the acylating solution.

[0099] Optionally, as shown in FIG. 1, the first vacuum exhaust port 901 and the second vacuum exhaust port 8013 are connected via a second hose 900.

[0100] In some embodiments, when performing the suction filtration operation, it can be connected to a gas source of an inert gas through the first inlet 101. By filling the acylating solution preparation system with an inert gas through the first inlet 101, the acylating solution prepared is subjected to suction filtration treatment in an inert atmosphere. Alternatively, before adding the solvent to the first inlet 101, an inert gas is passed through the first housing 107, the second housing 701, and the third housing 801 through the first inlet 101, and the entire preparation process of the acylating solution is carried out in an inert atmosphere.

[0101] In some embodiments, the first housing 107, the second housing 701, and the third housing 801 have an integral structure. The liquid discharge port 104 is provided at the bottom of the first housing 107, the filter device inlet 7011 is provided at the top of the second housing 701, and the filter device 7 is provided at the lower part of the kettle body 1. The filter device outlet 7012 is provided at the bottom of the second housing 701, the liquid storage tank inlet 8011 is provided at the top of the third housing 801, and the liquid storage tank 8 is provided at the lower part of the filter device 7.

[0102] Thereby, the acylation liquid prepared in the kettle body 1 can directly flow out of the kettle body 1 through the liquid discharge port 104 by its own gravity and enter the filter device 7 through the filter device inlet 7011. It is not necessary to additionally provide a liquid pump for pumping the acylation liquid between the liquid discharge port 104 and the filter device inlet 7011, and between the filter device outlet 7012 and the liquid storage tank inlet 8011. This simplifies the overall structure of the preparation system 100 for preparing the acylation liquid and is advantageous for reducing the manufacturing and running costs of the preparation system 100 for preparing the acylation liquid. Also, when assembling the preparation system 100 for preparing the acylation liquid, the connection between the liquid discharge port 104 and the filter device inlet 7011 and the connection between the filter device outlet 7012 and the liquid storage tank inlet 8011 can be omitted, facilitating the assembly of the preparation system 100 for preparing the acylation liquid.

[0103] Optionally, the materials of the first housing 107, the jacket 109, the second housing 701, and the third housing 801 are borosilicate glass. Thereby, the situation inside the kettle body 1, the filter device 7, and the liquid storage tank 8 can be easily observed.

[0104] In some embodiments, the preparation system 100 for preparing the acylation liquid further includes a first control valve 1041, and the first control valve 1041 is provided at the liquid discharge port 104 to control the opening and closing of the liquid discharge port 104.

[0105] Thus, when the first control valve 1041 is open, the prepared acylated liquid flows out of the kettle body 1 through the liquid discharge port 104. When the first control valve 1041 is closed, the kettle body 1 is sealed, and the prepared acylated liquid is stored in the kettle body 1.

[0106] In some embodiments, the preparation system 100 for preparing the acylated liquid further includes a second control valve, which is provided at the liquid storage tank outlet 8012 to control the opening and closing of the liquid storage tank outlet 8012.

[0107] Thus, by opening the second control valve, the filtered acylated liquid flows out of the liquid storage tank 8 through the liquid storage tank outlet 8012. When the second control valve is closed, the liquid storage tank 8 is sealed, and the filtered acylated liquid is stored in the liquid storage tank 8.

[0108] In some embodiments, the molar mass ratio of the acylating agent, Lewis catalyst, and solvent is (1.1 - 1.5):(1.3 - 1.7):5, and / or the molar mass ratio of the Lewis catalyst to the solvent is (1.3 - 1.7):5. In other words, the molar masses of the acylating agent, Lewis catalyst, and solvent satisfy that the molar mass ratio of the acylating agent, Lewis catalyst, and solvent is (1.1 - 1.5):(1.3 - 1.7):5 and the molar mass ratio of the Lewis catalyst to the solvent is (1.3 - 1.7):5, or the molar mass ratio of the acylating agent, Lewis catalyst, and solvent is (1.1 - 1.5):(1.3 - 1.7):5, or the molar mass ratio of the Lewis catalyst to the solvent is (1.3 - 1.7):5.

[0109] In the method for preparing the acylated liquid according to the embodiments of the present application, the ratio of each substance can be optimized, the raw materials can be fully utilized, and the production cost can be reduced.

[0110] As shown in FIG. 12, in some embodiments, continuously synthesizing acylnaphthalene with the prepared acylated liquid includes the following.

[0111] Preparation of the raw material liquid 14: Taking the case where the acylation liquid is 5 L as an example, 700 g of nitrobenzene and 284 g of 2-methylnaphthalene are added at room temperature together with 5 L of the acylation liquid into a reactor equipped with a stirring device to produce the raw material liquid 14. The 2-methylnaphthalene is extracted from wash oil, and its purity is 99.0 - 99.9%. The method for extracting 2-methylnaphthalene from wash oil is I. Rectifying and separating the wash oil to obtain a methylnaphthalene concentrated fraction, II. Passing the methylnaphthalene concentrated fraction through an azeotropic rectification column to perform azeotropic rectification to obtain an azeotropic distillate, III. Passing the azeotropic distillate through a separator to obtain a 2-methylnaphthalene crude product, IV. Passing the 2-methylnaphthalene crude product through a plurality of intermittently operated melt crystallization apparatuses connected in parallel to perform crystallization and purification of 2-methylnaphthalene.

[0112] In some embodiments, in step I, the wash oil is rectified and separated in an atmospheric rectification column to obtain a naphthalene fraction light oil, a methylnaphthalene concentrated fraction, and a heavy fraction oil. A part of the heavy fraction oil is refluxed to the atmospheric rectification column, and another part is recovered and reused. The naphthalene fraction light oil is obtained at the top of the atmospheric rectification column, the methylnaphthalene concentrated fraction is obtained from the side stream of the atmospheric rectification column, and the heavy fraction oil is obtained at the bottom of the atmospheric rectification column. The top temperature is 210 - 225 °C, the side stream temperature is 235 - 260 °C, and the bottom temperature is 290 - 310 °C.

[0113] In Step II, the methylnaphthalene concentrated fraction and the entrainer are mixed according to a certain ratio, and after heating the mixture to a certain temperature, it is put into an azeotropic rectification column for azeotropic rectification. The entrainer is a single compound entrainer or a mixture type entrainer. The single compound entrainer is any one of ethylene glycol, diethylene glycol, ethanolamine, diethylene glycol, and N-methylformamide. The mixture type entrainer is a mixture of heptane and ethanolamine or a mixture of heptane and ethylene glycol. The top temperature of the azeotropic rectification column is 150 - 175 °C, the top pressure is 1 - 4 KPa, the reflux ratio is 5 - 15, the bottom temperature is 220 - 245 °C, and the bottom pressure is 10 - 15 KPa.

[0114] Based on using a single compound entrainer, the mixing mass ratio of the methylnaphthalene concentrated fraction to the entrainer is 1 - 3:1. In response to using a mixture type entrainer, the mass ratio of heptane to ethanolamine or the mass ratio of heptane to ethylene glycol in the mixture type entrainer is 0.2 - 1:1, and the mixing mass ratio of the methylnaphthalene concentrated fraction to the entrainer is 1:0.8 - 2. In Step III, the azeotropic distillate and water are passed through an ultrasonic static mixer for ultrasonic mixing, and then passed through a separator for oil-water static separation. The operating temperature of the separator is 50 - 80 °C, the static time is 0.2 - 1 hour. The aqueous phase and the oil phase are separated from the separator. Here, the aqueous phase is the entrainer and water. The aqueous phase enters a rectification column for distillation separation of the entrainer and water. The separated entrainer is returned to Step II and mixed with the methylnaphthalene concentrated fraction for recycling. The separated water is returned and mixed with the azeotropic distillate for recycling. The oil phase is the 2-methylnaphthalene crude product. The oil phase enters an intermittent melting crystallizer for crystal purification of 2-methylnaphthalene.

[0115] In Step IV, there are two intermittent melting crystallizers. The initial temperature of the crystal growth process is 35 - 40°C, the temperature reduction rate is 3 - 8°C / h, the final temperature is 8 - 12°C, the constant temperature time is 0.5 - 1 h. The temperature increase rate of the sweating process is 2 - 6°C / h, the final temperature is 30 - 32°C. The temperature increase rate of the melting process is 2 - 8°C / h, the final temperature is 45 - 50°C, and the constant temperature time at the final temperature is 0.5 - 1 h.

[0116] In some embodiments, the method for extracting 2 - methylnaphthalene from wash oil is as follows. Add wash oil 1801 to wash oil storage tank V1, stir and mix it, then use a pump to send wash oil 1801 to atmospheric distillation column V2. By rectifying and separating wash oil 1801, naphthalene fraction light oil 1802 can be obtained from the top of the column, which can be used as the raw material for extracting naphthalene, and it can also be returned to atmospheric distillation column V2. Methylnaphthalene concentrated fraction 1803 is obtained from the side line, and the bottom product is heavy oil fraction 1804. A part of heavy oil fraction 1804 is returned to atmospheric distillation column V2, and the other part is sent to a coal tar processing plant to further separate products such as acenaphthene, fluorenone, and industrial fluorene. The top temperature of atmospheric distillation column V2 is 210 - 225°C, the side line temperature is 235 - 260°C, and the bottom temperature is 290 - 310°C. Mix the obtained methylnaphthalene concentrated fraction 1803 and azeotropic agent 1810 according to a certain ratio, heat the mixture to a certain temperature, and then send it to azeotropic distillation column V3 for azeotropic distillation. The azeotropic distillate 1805 obtained from the top of azeotropic distillation column V3 is sent to a separator to recycle azeotropic agent 1810, and residual oil 1806 is obtained from the bottom. Discharge residual oil 1806 and use it as the raw material for extracting other fine chemicals.

[0117] Since the mutual solubility of the azeotropic agent 1810 and water 1809 is strong, in this application, the azeotropic agent 1810 is recovered by a method of extracting water. After mixing the azeotropic distillate 1805 and water 1809 obtained in step (2), first, ultrasonic mixing is performed in the ultrasonic static mixer V4, and then it is sent to the separator V5 for static separation of oil and water. The water phase and the oil phase are separated from the separator. The water phase is the azeotropic agent mixture 1807 containing the azeotropic agent 1810 and water 1809, and the oil phase is the 2-methylnaphthalene crude product.

[0118] The water phase discharged from the separator V5 is sent to the rectification column V6 for distillation separation of the azeotropic agent 1810 and water 1809. After separation, the azeotropic agent 1810 obtained from the bottom of the column is returned to step (2) and mixed with the methylnaphthalene concentrated fraction 1803 for recycling. The water obtained from the top of the column after separation is returned and mixed with the azeotropic distillate 1805 for recycling. The 2-methylnaphthalene crude product discharged from the separator V5 is subjected to melt crystallization purification. Also, a method of connecting two batch melt crystallizers V8 in parallel is used to alternately perform the crystallization purification of 2-methylnaphthalene to achieve the goal of continuous crystallization purification. In the batch melt crystallizer V8, the methylnaphthalene crude product 1808 undergoes processes such as crystal growth, sweating, and melting in the batch melt crystallizer V8, and finally realizes the purpose of crystallization purification. The methylnaphthalene crude product 1808 obtains a high-purity 2-methylnaphthalene product 1813 through melt crystallization purification. The liquid discharged during the processes of crystal growth and sweating is the residual mother liquor 1812, and the residual mother liquor 1812 can be used as a raw material for extracting 1-methylnaphthalene. The purity of the 2-methylnaphthalene product 1813 obtained after crystallization purification is 99.0 - 99.9%, and the product yield is 70% - 90%.

[0119] In the method of extracting the above 2-methylnaphthalene from wash oil, the atmospheric distillation column V2 is a packed column, and the packing height corresponds to a stainless steel packed column with a theoretical plate number of 30 to 50 trays. A part of the heavy oil fraction 1804 at the bottom of the column circulates and is mixed with the wash oil and then enters the atmospheric distillation column V2. A part is discharged, and the ratio of discharge to circulation is 2 to 5:1. The content of 2-methylnaphthalene in the obtained methylnaphthalene concentrated fraction 1803 is 50 to 70%. The azeotropic distillation column V3 uses a concentric tube precision fractionation column as shown in Fig. 13. The fractionation column is obtained by fusing two precisely designed and calibrated concentric tubes. A helical groove 1822 is provided on the surface of the inner tube to enable efficient mass transfer and heat conduction between the vertically rising vapor and the liquid thin film in the concentric annular gap. The material is glass or stainless steel, and the theoretical plate number of the fractionation column is 80 to 120. The melting crystallizer is a full-filled cubic static crystallizer as shown in Fig. 14. Its outer shape is a cube, and a temperature control medium outlet 1814, a temperature control medium inlet 1815, a material inlet 1816, and a material outlet 1817 are provided. Inside the melting crystallizer, a plurality of sets of crystal plates parallel to each other are provided. As shown in Fig. 15, each set of crystal plates is provided with a spiral protrusion 1820. During crystallization, the crystal layer grows on the protrusion 1820 and is not easily fallen off. In the sweating process, the crystal layer falls from the growth surface of the crystal plate and enters the groove 1821 between the protrusions 1820 to maintain contact with the heat exchange surface and avoid the crystal layer from falling during sweating. Inside the crystal plate, a heating and condensing medium (i.e., the temperature control medium) is circulated. The temperature control medium flows in through the crystal plate temperature control medium inlet 1818 and flows out through the crystal plate temperature control medium outlet 1819, and circulates to the next group of crystal plates, and finally flows out from the temperature control medium outlet 1814 of the melting crystallizer. The material of the crystal plate is stainless steel, organic glass, or other alloys. Each batch melting crystallizer V8 is connected to a digitally temperature controllable oil bath V7, and a heating and cooling medium 1811 is conveyed between the digitally temperature controllable oil bath V7 and the batch melting crystallizer V8.

[0120] Therefore, in the examples of this application, in the conventional process method using benzene-based compounds in related technologies and the improved process method using coal-based naphthalene compounds as raw materials, the method of synthesizing 2,6-dimethylnaphthalene using naphthalene and methylnaphthalene as raw materials is completely changed. High-purity 2-methylnaphthalene is extracted using coal tar wash oil to improve the production efficiency, product purity, and yield of the 2-methylnaphthalene separation and purification process, reduce pollution, and lower the probability of equipment corrosion. Using the raw material 2-methylnaphthalene as the raw material liquid, acylations such as acylation with the acylating liquid and hydrolysis are carried out to obtain 2-methyl-6-propionylnaphthalene, achieving the goal of realizing the industrial production of 2-methyl-6-propionylnaphthalene through a non-petroleum-based route.

[0121] Reacting the prepared acylating liquid with the raw material liquid 14 is as shown in Figure 4. The raw material liquid 14 and the acylating liquid 15 are respectively sucked using metering pumps. The flow rate of the acylating liquid 15 (metering pump) is 158 - 162 g / min, and the flow rate of the raw material liquid 14 (metering pump) is 82 - 84 g / min, that is, according to the molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 being 1:1.3:1.5, the raw material liquid 14 and the acylating liquid 15 are injected into the three-way mixer 11 through a syringe and mixed. After mixing, they are put into the microchannel reactor 12 for reaction. After 5 - 10 minutes, the acylation reaction liquid flows out from the outlet of the microchannel reactor 12 and directly flows into the tank reactor 13 with multiple tanks connected in series. Stirring and reacting are carried out in the tank reactor 13. After passing through 2 - 4 tank reactors 13, the total residence time of the acylation reaction liquid in the tank reactor 13 with multiple tanks connected in series is 50 - 80 minutes. Synchronous hydrolysis is carried out on the acylation reaction liquid flowing out from the tank reactor 13, and after rectification, 2-methyl-6-propionylnaphthalene is obtained.

[0122] The kettle reactor 13 is a reactor in which a plurality of kettles are connected in series to realize a continuous reaction, and the flow rate is controlled through a regulating valve, thereby controlling the residence time of the materials in the kettle reactor 13. A plurality of microchannel reactors 12 are provided and connected in parallel with each other, and the flow rates of the acylating solution 15 and the raw material solution 14 are proportional to the number of parallel connections.

[0123] The three-way mixer 11 and the microchannel reactor 12 are arranged in the first constant temperature bath, and the temperature is controlled at -5 to 0 °C. In some embodiments, the temperature of the three-way mixer 11 and the microchannel reactor 12 is controlled at -5 °C. The kettle reactor 13 is arranged in the second constant temperature bath, and the temperature is controlled at 30 to 50 °C. In some embodiments, the temperature of the kettle reactor 13 is controlled at 35 °C.

[0124] In some embodiments, the raw material solution 14 of all the parallel-branched microchannel reactors 12 is transported by the same raw material solution pump, and the acylating solution 15 is transported by the same acylating solution pump.

[0125] In some embodiments, the microchannel reactor 12 connected in parallel and the kettle reactor 13 in which a plurality of kettles are connected in series use the method of direct connection.

[0126] In some embodiments, the three-way mixer 11 is a T-shaped mixer or a Y-shaped mixer with an inner diameter of 0.5 mm to 3 mm.

[0127] In some embodiments, the materials of both the microchannel reactor 12 and the kettle reactor 13 are strong acid corrosion-resistant materials and completely seal off the air.

[0128] In some embodiments, the inner diameter of the microchannel reactor 12 is 0.5 to 3.175 millimeters.

[0129] In some embodiments, the acylating agent in the acylating solution 15 is any one of propionyl chloride, acetyl chloride, acetic anhydride, and propionic anhydride.

[0130] In some embodiments, the method of directly hydrolyzing the acylation reaction solution through a water stage is as follows. In the hydrolysis section, the water injection pump is pre-operated, and before passing the acylation reaction solution through the hydrolysis section, water (deionized water) is passed through the aqueous phase pipeline of the hydrolysis section, and the flow rate of water in the aqueous phase pipeline is controlled to be 3 - 15 mL / min, preferably 10 mL / min. When water flows out from the outlet of the hydrolysis section, the acylation reaction solution is passed through the check valve in the pipeline and directly added to the oil phase pipeline of the hydrolysis section, and added to a low-temperature cold bath at 0 - 20°C, and in some embodiments, 0°C, together with water. After rapid mixing, it is added to a tubular reactor to carry out the hydrolysis reaction. The reaction temperature of the tubular reactor is 30 - 40°C, and in some embodiments, 30°C, and the inner diameter is 2 - 5 mm. At the same time, ultrasonic vibration is turned on to vibrate and stir the liquid in the tubular reactor, and the air extraction pump of the liquid separator 16 at the end is operated. Since the inner diameter of the tubular reactor is 2 - 5 mm, the liquid can proceed slowly, taking about 5 - 10 minutes from the inlet to the outlet of the tubular reactor, and the hydrolysis reaction can occur sufficiently.

[0131] When a turbid light brown liquid (the mixed solution after hydrolysis) flows out from the outlet of the tubular reactor, the liquid separator 16 collects the mixed solution. At this stage, water is always maintained in a flowing state until the mixed solution is completely discharged, and the hydrolysis reaction and the acylation reaction in the reaction section are carried out simultaneously.

[0132] The liquid separator 16 is a liquid-liquid separator. After the mixed solution is stratified in the liquid separator 16, the oil phase can be discharged from the discharge port, and the pH value of the oil phase is measured to be 6 - 7. The upper end of the liquid separator 16 is connected to an air extraction pump through a pipeline, and the exhaust gas (such as HCl) generated by hydrolysis can be drawn out, enter the alkali liquid tank at the rear end, collect the exhaust gas, and will not pollute the air.

[0133] In some embodiments, the specific structure of the liquid distributor 16 is as shown in FIG. 5, including a container 1604, a stirring device, a supply port 1602, a discharge port 1605, and an exhaust port 1601. The stirring device enters into the container 1604 and is connected and driven via an external speed reducer. Since the stirring device has a normal structure and is not a key point of this solution, the stirring device is not fully depicted in the drawings of this solution, and the stirring device is not used in this solution. The discharge port 1605 communicates with the bottom end of the container 1604, and both the supply port 1602 and the exhaust port 1601 communicate with the upper end of the container 1604. The supply port 1602 is connected to the outlet of the tubular reactor in the hydrolysis section via a pipeline, and the exhaust port 1601 is connected to an extraction pump via a pipeline. Control valves 1603 are respectively provided at the supply port 1602, the discharge port 1605, and the exhaust port 1601. The control valve 1603 at the discharge port 1605 initially maintains a closed state and the control valve 1603 is opened when attempting to discharge the stratified oil phase. Stratification is for separating the water phase and the oil phase. The oil phase is located below the water, and the discharge port 1605 discharges the oil phase first. After the oil phase is completely drained, it is inevitable that some water will be discharged together with it, and it can be purified by rectification in the later stage.

[0134] It should be noted that the space of the container 1604 of the liquid distributor 16 is large enough, the effective volume is 10 L, there is no worry about the liquid distributor 16 being filled, the inner diameter of the passage in the tubular reactor is small, the progress of the liquid is slow, and finally, even if the mixed liquid completely flows into the liquid distributor 16, it will not be filled. The temperature that the liquid distributor 16 can withstand is -80 to 200 °C, and there is no worry about the liquid distributor 16 being damaged due to temperature during use.

[0135] In some embodiments, the check valve is a stainless steel ferrule check valve, and the material of the internal flow path is polytetrafluoroethylene, with better corrosion prevention performance. The flow path in a normal check valve is usually made of ordinary rubber material or corrosion-resistant rubber. However, through experiments, its corrosion prevention effect is not good, so it is changed to polytetrafluoroethylene material to greatly improve the corrosion prevention performance.

[0136] In this synchronous hydrolysis method, first start the water pump, immediately connect the acylation reaction liquid flowing out from the kettle reactor 13 to the hydrolysis section, perform hydrolysis continuously and stably, and both the hydrolysis efficiency and the material balance rate are greatly improved.

[0137] In this solution, the synchronization between the acylation reaction and the hydrolysis reaction avoids the temporary storage of the acylation reaction liquid and reduces the leakage and pollution of HCl gas.

[0138] The hydrolysis reaction is an exothermic reaction and should be added to the tubular reactor after being quickly mixed with water in a low-temperature cold bath (0°C), which can quickly reduce the temperature of hydrolysis.

[0139] When performing the hydrolysis reaction using a tubular reactor, an additional check valve is installed in the front part of the pipeline where the acylation reaction liquid merges with water to avoid the liquid from flowing back from the hydrolysis section to the acylation section and avoid the risk of clogging the passage of the tubular reactor.

[0140] The liquid obtained from hydrolysis can directly enter from the upper end of the liquid separator 16 to perform liquid separation synchronously. The oil phase can be easily discharged from the discharge port. It is obtained by measurement that the pH value of the oil phase obtained by hydrolysis is 6 - 7, meeting the requirements of purification.

[0141] This hydrolysis method directly connects the acylation reaction liquid flowing out from the tubular reactor to the hydrolysis section, continuously and stably performs synchronous hydrolysis, improves the material balance rate, and importantly, there is no risk of clogging. The liquid obtained by hydrolysis can be directly added to the liquid separator 16 to perform liquid separation synchronously. The oil phase is discharged from the discharge port to perform rectification and crystallization treatment to obtain 2 - methyl - 6 - propionylnaphthalene. The generated exhaust gas can be drawn out from the upper exhaust port 1601 of the liquid separator 16, and the aqueous phase is treated in the acylation wastewater treatment process.

[0142] In some embodiments, a method for rectifying the oil phase separated in the hydrolysis reaction is proposed, as shown in Figure 6.

[0143] (1) The oil phase separated by the hydrolysis reaction is sent from the middle part of the first rectification column to the first rectification column for rectification. The light fraction evaporates from the top of the column, is condensed, and then recovered. The bottom liquid flows out from the bottom of the column.

[0144] In some embodiments, the oil phase separated by the hydrolysis reaction is passed through the first rectification column. The inside of the first rectification column is an acyl light component removal column, and the packing material used is is ceramics, spring, θ-ring or a combination thereof. The light fraction at the top of the light component removal column mainly enters the advanced oxidation treatment of wastewater after a small amount of water is condensed, and is nitrobenzene collected from the side line of the light component removal column, which can be recovered and recycled. The bottom liquid flowing out from the bottom of the kettle of the light component removal column is sent to the second rectification column as a crude product.

[0145] In some embodiments, the pressure of the first rectification column is 0.05 KPa to 10 KPa, and in some embodiments it is 0.1 KPa to 2 KPa, and the reflux ratio is (1 to 2):1.

[0146] In some embodiments, the condensation temperature of the first rectification column is 10 to 20 °C, and in some embodiments it is 10 to 15 °C.

[0147] (2) The bottom liquid of step (1) is pressure-fed to the second rectification column while it is hot for further rectification. The light fraction of the second rectification column evaporates from the top of the column, is condensed, and then collected. The product is collected from the side line of the second rectification column. The high-boiling components at the bottom of the column enter the bottom of the column. After being heated by the bottom reboiler, the high-boiling components at the bottom are pressure-fed into the bottom material collection tank while they are hot.

[0148] In some embodiments, the second rectification column is a heavy component removal column, and the packing material used isIt is ceramics, a spring, a θ-ring or a combination thereof. Isomers and light components other than 2-methyl-6-propionylnaphthalene (2,6-MPN) distill from the top of the heavy component removal column, are condensed, and then recovered. A small amount of heavy colored impurities are periodically collected from the bottom of the heavy component removal column and then treated. The crude 2,6-MPN fraction in the acylation section is taken from the side line of the heavy component removal column, cooled, and then sent to a recrystallizer. The acyl group of 2 -methyl-6-acylnaphthalene is any one of a methyl group, an ethyl group, or an isopropyl group, that is, the product 2-methyl-6-acylnaphthalene is 2-methyl-6-formylnaphthalene, 2-methyl-6-acetylnaphthalene or 2-methyl-6-isopropylnaphthalene selected from .

[0149] In some embodiments, the pressure of the second rectification column is 0.05 KPa to 10 KPa, in some embodiments 0.1 KPa to 2 KPa, and the reflux ratio is (5 to 10):1.

[0150] In some embodiments, the condensation temperature of the second rectification column is 50 to 90 °C, in some embodiments 70 to 90 °C.

[0151] In some embodiments, the method for recrystallizing the crude product 2,6-MPN is as follows. An aqueous methanol solution (mass ratio of methanol: water is 85:15) and the crude product 2,6-MPN are mixed in a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser according to a mass ratio of 8:1, and stirred in a water bath at 55 °C until the pale yellow solid is completely dissolved. After continuous stirring for 20 minutes, the recrystallization solution is crystallized at 10 °C for 6 hours. After complete crystallization, suction filtration is performed to separate the solid from the liquid, and white fine powder 2-methyl-6-propionylnaphthalene can be obtained. The product is placed in a dryer to remove the solvent, and the 2,6-MPN slurry obtained by recrystallization is separated by a product filter to obtain a filter cake and a filtrate. The mother liquor and the washing liquid enter a methanol recovery tower, and methanol distills out from the top and is reused. The bottom distillate enters the sewage system. The wet filter cake is dried in a dryer, and the exhaust from the dryer enters the methanol recovery system. After drying, the product 2,6-MPN is obtained.

[0152] In addition, the specific process for treating the aqueous phase separated in the liquid separator 16 in the treatment process of the acylation wastewater is as shown below.

[0153] As shown in FIG. 7, the resource-recoverable acylation wastewater treatment system according to the embodiment of the present application includes a sedimentation tank 1702, a filtration unit 1703, an extraction unit 1704, a rectification column 1705, a biochemical treatment unit 1706, a dissolution tank 1707, and a reaction kettle 1708. The sedimentation tank 1702 is used to generate aluminum hydroxide precipitate. The inlet of the filtration unit 1703 communicates with the outlet of the sedimentation tank 1702. The inlet of the extraction unit 1704 communicates with the filtrate outlet of the filtration unit 1703. An extraction solvent inlet is provided in the extraction unit 1704. The inlet of the rectification column 1705 communicates with the extraction phase outlet of the extraction unit 1704. The extraction solvent outlet of the rectification column 1705 communicates with the extraction solvent inlet. The nitrobenzene outlet of the rectification column 1705 communicates with the production organic solvent pipeline. The inlet of the biochemical treatment unit 1706 communicates with the raffinate phase outlet of the extraction unit 1704. The outlet of the biochemical treatment unit 1706 communicates with the wastewater standard-compliant discharge pipeline. The outlet of the dissolution tank 1707 communicates with the filter cake outlet of the filtration unit 1703. A concentrated hydrochloric acid inlet is provided in the dissolution tank 1707. The inlet of the reaction kettle 1708 communicates with the outlet of the dissolution tank 1707.

[0154] In some embodiments, the extraction unit 1704 is a centrifugal extraction device, such as a commercially available centrifugal extractor.

[0155] In some embodiments, the biochemical treatment unit 1706 can use an activated sludge treatment system. Since the activated sludge system is not the focus of the present application, a normal activated sludge treatment system can be used. As shown in FIG. 8, a normal activated sludge treatment system includes an aeration tank 17061, a secondary sedimentation tank 17602, a reflux system, a surplus sludge discharge system, an oxygen supply system, etc. In some embodiments of the present application, when the raffinate phase outlet of the extraction unit 1704 is communicated with the water inlet of the aeration tank 17061, the raffinate phase can be introduced into the activated sludge treatment system and treated by the normal activated sludge method to achieve discharge meeting the standards.

[0156] Regarding the resource-recoverable acylation wastewater treatment system according to the embodiments of the present application, the communication method between each component may be selected to communicate through a pipeline according to the nature of the material, or realized by transporting with a relay transport vehicle, etc. When communicating with a pipeline, valves and pumps can be installed on the corresponding pipeline as needed, and these are all common technologies and not the focus of the present application.

[0157] In some embodiments, in order to adjust the water volume, balance the water quality, and pretreat the acylation wastewater, the resource-recoverable acylation wastewater treatment system according to the embodiments of the present application further includes an adjustment tank 1701 provided in front of the sedimentation tank 1702. The acylation wastewater first enters the adjustment tank 1701, where the water quality and volume are adjusted and pretreated, and then enters the sedimentation tank 1702.

[0158] In some embodiments, a stainless steel reaction kettle or the like can be used for the reaction kettle. A cross-flow sedimentation tank or a vertical-flow sedimentation tank or the like can be used for the sedimentation tank 1702, and a plate-frame filter press can be used for the filtration unit 1703. An ordinary dissolution tank can be used for the dissolution tank, and a packed tower or a plate column or the like can be used for the rectification column.

[0159] The operating principle of the resource-recoverable acylation wastewater treatment system according to the embodiments of the present application is as follows.

[0160] During use, the aqueous phase first enters the adjustment tank 1701 to adjust the water volume, balance and pretreat the water quality, and then enters the sedimentation tank 1702. The acylation wastewater entering the sedimentation tank 1702 has its pH adjusted to alkaline by at least one of an alkali source, namely sodium hydroxide, potassium hydroxide or liquefied ammonia, that is, the pH is 8 - 10, and in some embodiments the pH is about 9. The aluminum ion precipitate in the acylation wastewater is aluminum hydroxide. The suspension containing the aluminum hydroxide precipitate enters the filtration unit 1703 for filtration, and a filtration cake of aluminum hydroxide and a filtrate are obtained. After the pH of the filtrate is adjusted to 2 - 3 using at least one of hydrochloric acid, nitric acid or sulfuric acid, it enters the extraction unit 1704 and is extracted by the extraction solvent in the extraction unit 1704 under stirring conditions to form a layered structure, generating an extraction phase and a raffinate phase. Here, the extraction solvent is a non-polar organic solvent and is at least one of normal heptane, normal octane, normal hexane, benzene, toluene, xylene, carbon tetrachloride, and the volume ratio of the extraction solvent to the filtrate is 0.5 - 5:1.

[0161] After that, the extraction phase enters the rectification column 1705 to achieve efficient separation of nitrobenzene and the extraction solvent, obtaining raw material nitrobenzene and the extraction solvent. The extraction solvent exiting the rectification column 1705 enters the extraction unit 1704 again to participate in the extraction of the filtrate. The nitrobenzene exiting the rectification column 1705 enters the production organic solvent pipeline and is used in the production of related chemicals. The raffinate phase exiting the extraction unit 1704 enters the biochemical treatment unit 1706, where it is biochemically treated and discharged after reaching the standard. The aluminum hydroxide filter cake exiting the filtration unit 1703 enters the dissolving tank 1707, where it is heated and dissolved at 40 - 50°C under the action of concentrated hydrochloric acid in the dissolving tank 1707. The weight ratio of the filter cake to the concentrated hydrochloric acid is 0.5 - 2.5:1. Then it enters the reaction kettle and polymerizes with the auxiliary agent added to the reaction kettle 1708 to obtain polyaluminum chloride as a water treatment agent. The quality of the obtained polyaluminum chloride meets the national standard of polyaluminum chloride 《GB / T22627 - 2014 Water treatment agent - Polyaluminum chloride》. The auxiliary agent is calcium aluminate or / and magnesium aluminate, and its addition amount is 2 - 10wt% of the dry weight of the filter cake.

[0162] It should be noted that the acylating wastewater treatment process with resource recovery in the embodiments of the present application can treat acylating wastewater and recover its resources by using the acylating wastewater treatment system with resource recovery in the embodiments of the present application. However, the system devices on which its realization depends are not limited to the acylating wastewater treatment system with resource recovery in the embodiments of the present application.

[0163] Hereinafter, the acylating wastewater treatment process with resource recovery in the embodiments of the present application will be described in conjunction with specific examples.

[0164] The raw material reagents and equipment related to the embodiments of the present application are reagents and equipment obtained by commercial methods unless otherwise specified. Unless otherwise specified, the detection methods and the like related to the embodiments of the present application are all ordinary methods.

[0165] The following examples of this application are all carried out under laboratory conditions. For suction filtration, a laboratory suction filtration device assembled with a Buchner funnel, a suction filtration flask, a rubber tube, a vacuum pump, and filter paper can be used.

[0166] Hereinafter, a method for preparing an acylation solution of an example of this application will be described in detail according to the examples.

[0167] <Example 1> <Preparation of acylation solution> Add 600.4 g of nitrobenzene to a three-necked flask, weigh 200.41 g of aluminum chloride under the protection of nitrogen gas, add it into the nitrobenzene in the first chamber 110, stir with a stirrer 3, heat to 60 °C with a heat exchange medium, and stir the dissolution at 300 rpm to obtain a mixed solution. Under the condition that the temperature of the mixed solution is 50 °C, use a feeding pump 6 to dropwise add 120.13 g of a propionylating agent at a dropping rate of 5 drops per second, stir at 300 rpm, and after the dropping is completed, obtain the prepared acylation solution. The acylation solution is subjected to suction filtration treatment using a suction filtration device under the protection of nitrogen gas to remove solid particles in the acylation solution to obtain an acylation solution, store it in a liquid storage tank for 30 days, and its solid content is less than 0.2%.

[0168] <Continuous synthesis of acylnaphthalene with acylation solution> Using a metering pump, the raw material liquid 14 and the acylating liquid 15 in Example 1 were each sucked up. The flow rate of the acylating liquid 15 (metering pump) was 160 g / min, and the flow rate of the raw material liquid 14 (metering pump) was 83 g / min. That is, the raw materials were blended according to a molar ratio of 2-methylnaphthalene: propionyl chloride: AlCl3 = 1: 1.3: 1.5. Two types of materials were injected into a three-way mixer 11 with an inner diameter of 3 mm through a syringe and mixed. After mixing, they were added to a microchannel reactor 12 with an inner diameter of 3 mm for reaction. After 5 minutes, the acylating reaction liquid flowed out from the outlet of the microchannel reactor 12. Here, the three-way mixer 11 and the microchannel reactor 12 were arranged in the first constant temperature bath, and the reaction temperature was controlled at -5°C. It was flowed into a tank reactor 13 in which a plurality of tanks were connected in series. The tank reactor 13 was arranged in the second constant temperature bath, and the reaction temperature was controlled at 40°C. Stirring was carried out in the tank reactor 13 for reaction. The total residence time through the three tank reactors 13 was 60 minutes. The acylating reaction liquid flowing out from the tank reactor 13 underwent a hydrolysis reaction with demineralized water in a tubular reactor.

[0169] That is, the method for carrying out the hydrolysis reaction in the tubular reactor is as follows. In the hydrolysis section, the water injection pump was started in advance. Before passing the acylating reaction liquid through the hydrolysis section, deionized water was passed through the aqueous phase pipeline in the hydrolysis section, and the flow rate of the water in the aqueous phase pipeline was controlled at 10 mL / min. When water flowed out from the outlet of the hydrolysis section, the acylating reaction liquid flowing out from the tank reactor 13 was passed through a check valve in the pipeline and directly introduced into the oil phase pipeline in the hydrolysis section. It was quickly mixed with water at 0°C in a low-temperature cold bath and then introduced into the tubular reactor, and the hydrolysis reaction was carried out at 30°C. At the same time, ultrasonic vibration was turned on to vibrate and stir the liquid in the tubular reactor, and the air extraction pump of the end liquid separator 16 was started. After the acylating reaction was completed, the obtained hydrolysis liquid was put into the liquid separator 16, stirred at 80°C in the liquid separator 16, and after 4 hours, the stratification of the oil phase and the aqueous phase could be completed. The oil phase solution after liquid separation was prepared for rectification, and the aqueous phase solution was sent to the sewage treatment plant in the industrial park after advanced oxidation treatment of the wastewater. The conversion rate of 2-methylnaphthalene in the acylating reaction was greater than 99.0%, and the selectivity was 88.0%.

[0170] The method of rectifying the oil phase separated by the hydrolysis reaction includes the following steps, as shown in Figure 6.

[0171] (1) The oil phase is sent to the first rectification column from the middle part of the first rectification column for rectification. The acylation reaction solution contains 80 wt% nitrobenzene solvent and 20 wt% crude fraction of 2-methyl-6-propionylnaphthalene. The pressure of the first rectification column is 0.1 kPa, the rectification temperature is 45 - 130 °C, nitrobenzene evaporates from the top of the column at 45 °C, the reflux ratio is 1:1, the condensation temperature at the top of the column is 10 °C, the gaseous nitrobenzene at the top of the column is condensed and then nitrobenzene solvent C is recovered from the top of the column, the temperature of the bottom liquid B is 130 °C and it flows out from the bottom of the column. After rectification by the first rectification column, 98% of the nitrobenzene solvent C is recovered, and the bottom liquid B contains 78% of crude 2-methyl-6-propionylnaphthalene.

[0172] (2) The discharge temperature of the bottom liquid B in step (1) is 130 °C. While it is hot, it is pumped to the second rectification column for further rectification. The pressure of the second rectification column is 1 kPa, the rectification temperature is 110 - 150 °C, the reflux ratio is 5:1, the condensation temperature is 75 °C, 17 wt% of the isomer light fraction D of 2-methyl-6-propionylnaphthalene evaporates from the top of the column at 114 °C, is condensed and then collected, 80 wt% of the product E, 2-methyl-6-propionylnaphthalene, is collected from the side line of the second rectification column at 136 °C, 3% of the high-boiling components F at the bottom of the column enter the bottom of the column, are heated by the bottom reboiler, and then pumped into the bottom material collection tank while it is hot.

[0173] The number of theoretical plates of the first rectification column is 30, the feeding position is at the 15th theoretical plate, the number of theoretical plates of the second rectification column is 40, the feeding position is at the 25th theoretical plate, and the product side line collection is at the 22nd theoretical plate.

[0174] The method for recrystallizing crude 2,6-MPN is as follows: In a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, an aqueous methanol solution (mass ratio of methanol to water is 85:15) and crude 2,6-MPN are mixed according to a mass ratio of 8:1. Stir the mixture in a water bath at 55°C until the light yellow solid completely dissolves, and continue stirring for 20 minutes. Then, crystallize the recrystallization solution at 10°C for 6 hours. After complete crystallization, perform suction filtration to separate the solid and liquid, and white fine powder 2-methyl-6-propionylnaphthalene can be obtained. Put the product into a dryer to remove the solvent, separate the 2,6-MPN slurry obtained by recrystallization with a product filter to obtain a filter cake and a filtrate. The mother liquor and the washing liquid enter a methanol recovery tower, and methanol distills out from the top and is reused. The bottom distillate enters the sewage system. Dry the wet filter cake with a dryer, the exhaust gas from the dryer enters the methanol recovery system, and the product 2,6-MPN is obtained after drying.

[0175] The acylation solution prepared by the method of Example 1 is mixed with the prepared 2-methylnaphthalene raw material liquid 14, and an acylation reaction is carried out in a combined microchannel and kettle reactor. After the reaction, hydrolysis, vacuum rectification, and recrystallization are carried out to obtain a 2-methyl-6-propionylnaphthalene product with a yield of 80% and a purity of 98.0%.

[0176] In Examples 2 to 7 and Comparative Examples 1 to 9, except for adjusting the preparation of the acylation solution, the reaction conditions of acylation hydrolysis, and the oil phase rectification process according to Table 1, the others are the same as in Example 1. The solid content of the acylation solution, the conversion rate, selectivity of 2-methylnaphthalene in the acylation reaction, and the yield and purity results of obtaining a 2-methyl-6-propionylnaphthalene product after recrystallization in each example and comparative example are as shown in Table 1 below.

[0177] Performance detection results at different stages of each example and comparative example JPEG0007702429000002.jpg255166JPEG0007702429000003.jpg255161JPEG0007702429000004.jpg255166

[0178] As shown in Table 1, compared with Example 1, the data of Example 2 removed all the undissolved solid particles in the acylation solution by performing suction filtration treatment without using a suction filtration device. In Example 2, since the acylation solution may block the microchannel reactor 12 in the later acylation reaction stage, the yield of obtaining the 2-methyl-6-propionylnaphthalene product after recrystallization is reduced. Also, the protective atmosphere and control parameters in the process of preparing the acylation solution 15 are extremely important. For example, as can be seen from the comparison between Comparative Example 1 and Example 1, when weighing aluminum chloride, it is not carried out under the protection of nitrogen gas, and it is observed that white smoke comes out from the mouth of the bottle, the color of aluminum chloride changes from light yellow to white, indicating that the surface of aluminum chloride is inactivated. Therefore, since the AlCl3 catalyst is easily inactivated by contacting with moisture in the air, the conversion of 2-methylnaphthalene in the acylation reaction stage becomes incomplete. Further, in the acylation reaction stage, as can be seen from the comparison between Example 1 and Comparative Examples 5 to 7, the small addition amount of propionyl chloride also results in incomplete conversion of 2-methylnaphthalene. When the addition amounts of propionyl chloride and the catalyst are large, it does not affect the conversion of 2-methylnaphthalene. From the above, the small addition amount of propionyl chloride, the small amount of catalyst, and the inappropriate catalyst temperature all result in incomplete conversion of 2-methylnaphthalene.

[0179] As shown in Examples 1 and 4 to 7 of the table, the influence of different acylation reaction conditions on the acylation reaction process is shown. Here, when Examples 4 to 7 and Comparative Examples 2 to 8 are compared with Example 1, in the acylation process, by changing the temperature at which the triangular mixer 11 and the microchannel reactor 12 are arranged in the first constant temperature bath, the reaction temperature at which the kettle reactor 13 is arranged in the second constant temperature bath, the number of kettle reactors 13 connected in series, the residence time, and the ratio relationship of 2-methylnaphthalene:propionyl chloride:AlCl3, it is found that all different acylation reaction conditions affect the selectivity of 2-methylnaphthalene and the yield of obtaining the 2-methyl-6-propionylnaphthalene product after recrystallization.

[0180] The triangular mixer 11 and the microchannel reactor 12 are arranged in the first constant temperature bath for low-temperature mixing. When the raw material liquid 14 and the acylation liquid 15 are mixed and violently release heat, not only can heat be transferred at a low temperature, but also the acylation reaction is controlled by kinetics in the low-temperature microreactor region and the reaction is fast. Therefore, 60% - 70% of 2-methylnaphthalene is converted into the acylation product, the temperature of the kettle reactor 13 rises, and by reacting the mixed liquid in the kettle reactor 13 for a certain period of time, the unreacted 2-methylnaphthalene can be continuously reacted, improving the conversion rate of the reaction. At the same time, industrially, the cost of using only the microchannel reactor 12 can be reduced. By accurately controlling the temperatures of the first constant temperature bath and the second constant temperature bath, a high conversion rate of the reaction and a high selectivity of the reaction are ensured. For example, as can be seen from comparing Example 1 and Comparative Example 2 in the table, changing the temperature of the first constant temperature bath has a great influence on the selectivity of 2-methylnaphthalene. As can be seen from comparing Example 1 and Comparative Example 3, changing the temperature of the second constant temperature bath has a great influence on the selectivity of 2-methylnaphthalene and the yield of the 2-methyl-6-propionylnaphthalene product.

[0181] As can be seen from comparing Example 1 and Comparative Example 4, using five kettle reactors 13 and setting the total residence time to 90 min is almost the same as the data of Example 1, only the experimental time is extended. As can be seen from comparing Examples 4 - 7 and Comparative Example 8, in Comparative Example 8, only the microchannel reactor 12 with an inner diameter of 3 mm is used for the reaction and not used together with the kettle reactor 13, so the selectivity of 2-methylnaphthalene is low. It has been found that the microchannel reactor 12 has a high specific surface area, high safety performance, fast temperature response, mainly mass transfer by diffusion, removes heat from the reaction system, ensures that the reactants react at the optimal reactant temperature, and helps to improve the selectivity and yield of the reactants. However, using only the microchannel reactor 12 results in a long acylation reaction time and is disadvantageous for the subsequent hydrolysis.

[0182] In Comparative Example 9, batch hydrolysis was performed on the acylation reaction solution flowing out of the kettle reactor. Compared with Example 1, instead of directly passing the acylation reaction solution flowing out of the kettle reactor 13 through the tubular reactor to directly carry out the synchronous hydrolysis reaction, that is, there is a certain time interval from obtaining the acylation reaction solution to before the hydrolysis reaction. Water is directly added into the storage tank for hydrolysis. The acylation reaction solution cannot be hydrolyzed immediately. When left standing, it easily reacts with the water in the air during hydrolysis, and there is also a leakage of HCl gas itself, which pollutes the air and is disadvantageous for adjusting the hydrolysis reaction time, temperature, and material balance rate, and increases the water consumption by 2 to 3 times. Compared with Example 1, in Comparative Example 10, the acylation reaction solution flowing out of the kettle reactor and demineralized water are subjected to a hydrolysis reaction in a continuous synchronous hydrolysis reactor. Instead of stopping the acylation reaction and separating the obtained hydrolysis solution with the liquid separator in Example 1, after 24 hours of static separation, the oil phase and the water phase are stratified, which not only requires a long liquid separation time of 24 hours, but also the exhaust gas generated during the liquid separation process pollutes the environment.

[0183] In addition, Examples 8 to 12 exemplarily show a specific process in which the hydrolysis solution is put into the liquid separator 16 and the aqueous solution after liquid separation is treated in the treatment process of the acylation wastewater.

[0184] <Example 8> Prepare 500 mL of acylated wastewater (COD: 6530 mg / L, nitrobenzene: 3200 mg / L, chloride ions: 3000 mg / L, aluminum ions: 3000 mg / L), add it to a beaker, add 8 g of sodium hydroxide, adjust the pH to 9.0, and react for 0.5 h to obtain a suspension containing aluminum hydroxide precipitate. Then, after suction filtration of the suspension, obtain a filter cake and a filtrate, and naturally dry the filter cake. Adjust the pH of the filtrate to 2 with 18 wt% hydrochloric acid, transfer the filtrate to a separatory funnel containing 500 mL of normal heptane, shake it uniformly, and then let it stand for 30 min to stratify. Transfer the supernatant (extraction phase) to a packed column for rectification recovery (the number of trays is 15, the reflux ratio is 0.06, the top temperature of the column is 98 °C, and the bottom temperature of the column is 176 °C) to obtain nitrobenzene raw material with a purity of 99% and extraction solvent normal heptane with a purity of 98%. The nitrobenzene recovery rate reaches 90%, and the loss of the extraction solvent normal heptane is only 3%. Transfer the lower layer solution (raffinate phase) of the separatory funnel to an activated sludge treatment system for further treatment for 10 h. Add 10000 mg of dry filter cake to a beaker containing 5000 mL of concentrated hydrochloric acid, dissolve it at 40 °C, and then react with 500 mg of calcium aluminate at 70 °C and 0.5 MPa to obtain the product polyaluminum chloride.

[0185] By detection, after treatment by the activated sludge treatment system, in the wastewater, COD = 55 mg / L (as shown in Figure 9), nitrobenzene concentration = 0.5 mg / L, both of which meet the requirements of the discharge standard "Integrated Wastewater Discharge Standard GB8978 - 1996" (COD < 100 mg / L, nitrobenzene < 1.0 mg / L). The main indicators of the obtained product polyaluminum chloride are that the mass fraction of aluminum chloride is 29%, the basicity is 55%, the mass fraction of water-insoluble substances is 0.2, the pH value is 4.5, the mass fraction of iron is 1.0%, and arsenic, lead, chromium, mercury, and cadmium are not detected. Each index of the product polyaluminum chloride meets the requirements of the national standard "Water Treatment Agent - Polyaluminum Chloride GB / T22627 - 2014".

[0186] <Example 9> Prepare 500 mL of acylated wastewater (COD: 6900 mg / L, nitrobenzene: 2700 mg / L, chloride ions: 3000 mg / L, aluminum ions: 3000 mg / L), add it to a beaker, add 7.5 g of potassium hydroxide, adjust the pH to 9.2, and react for 0.5 h to obtain a suspension containing aluminum hydroxide precipitate. Then, suction filter the suspension to obtain a filter cake and a filtrate, and naturally dry the filter cake. Adjust the pH of the filtrate to 2.5 with 50 wt% sulfuric acid, transfer the filtrate to a separatory funnel containing 600 mL of normal heptane, shake it uniformly, and then let it stand for 30 min to stratify. Transfer the supernatant (extraction phase) to a rectification column for rectification recovery (the number of trays is 15, the reflux ratio is 0.06, the top temperature of the column is 98 °C, and the bottom temperature of the column is 176 °C) to obtain nitrobenzene raw material with a purity of 99% and extraction solvent normal heptane with a purity of 98%. The nitrobenzene recovery rate reaches 92%, and the loss of extraction solvent normal heptane is only 4%. Transfer the lower layer solution (raffinate phase) of the separatory funnel to an activated sludge treatment system for further treatment for 12 h. Add 10000 mg of dry filter cake to a dissolution tank containing 6000 mL of concentrated hydrochloric acid, dissolve it at 45 °C, and then react with 400 mg of magnesium aluminate at 80 °C and 0.7 MPa to obtain the product polyaluminum chloride.

[0187] By detection, after treatment by the activated sludge treatment system, in the effluent, COD = 50 mg / L (as shown in Figure 10), nitrobenzene concentration = 0.5 mg / L, both meet the requirements of the discharge standard "Integrated Wastewater Discharge Standard GB8978 - 1996" (COD < 100 mg / L, nitrobenzene < 1.0 mg / L). The main indicators of the obtained product polyaluminum chloride are that the mass fraction of aluminum chloride is 30%, the basicity is 56%, the mass fraction of water-insoluble substances is 0.3, the pH value is 5.0, the mass fraction of iron is 1.0%, and arsenic, lead, chromium, mercury, and cadmium are not detected. Each index of the product polyaluminum chloride meets the requirements of the national standard "Water Treatment Agent - Polyaluminum Chloride GB / T22627 - 2014".

[0188] <Example 10> Prepare 500 mL of acylated wastewater (COD: 7200 mg / L, nitrobenzene: 4200 mg / L, chloride ions: 3000 mg / L, aluminum ions: 2500 mg / L) and add it to a beaker. Add 8.2 g of potassium hydroxide, adjust the pH to 9.0, and react for 0.5 h to obtain a suspension containing aluminum hydroxide precipitate. Then, suction filter the suspension to obtain a filter cake and a filtrate, and naturally dry the filter cake. Adjust the pH of the filtrate to 3 with 15 wt% hydrochloric acid, transfer the filtrate to a separatory funnel containing 600 mL of normal heptane, shake it uniformly, and let it stand for 30 min to stratify. Transfer the supernatant (extraction phase) to a rectification column for rectification recovery (the number of trays is 15, the reflux ratio is 0.06, the top temperature of the column is 98 °C, and the bottom temperature of the column is 176 °C) to obtain nitrobenzene raw material with a purity of 99% and extraction solvent normal heptane with a purity of 99%. The nitrobenzene recovery rate reaches 88%, and the loss of extraction solvent normal heptane is only 6%. Transfer the lower layer solution (raffinate phase) of the separatory funnel to an activated sludge treatment system for further treatment for 12 h. Add 8000 mg of dry filter cake to a dissolution tank containing 5000 mL of concentrated hydrochloric acid, dissolve it at 50 °C, and then react with 450 mg of magnesium aluminate at 80 °C and 0.7 MPa to obtain the product polyaluminum chloride.

[0189] By detection, after treatment by the activated sludge treatment system, the COD = 55 mg / L (as shown in Figure 11) and the concentration of nitrobenzene = 0.5 mg / L in the wastewater both meet the requirements of the discharge standard 《Integrated Wastewater Discharge Standard GB8978-1996》(COD < 100 mg / L, nitrobenzene < 1.0 mg / L). The main indicators of the obtained product polyaluminum chloride are that the mass fraction of aluminum chloride is 31%, the basicity is 62%, the mass fraction of water-insoluble substances is 0.4, the pH value is 6.5, the mass fraction of iron is 2.0%, and arsenic, lead, chromium, mercury, and cadmium are not detected. All the indicators of the product polyaluminum chloride meet the requirements of the national standard 《Water Treatment Agent - Polyaluminum Chloride GB / T22627-2014》.

[0190] <Example 11> The example of this application is almost the same as Example 18. The difference is that the extraction solvent is carbon tetrachloride.

[0191] <Example 12> The example of this application is almost the same as Example 18. The difference is that the extraction solvent is a mixture of normal octane and xylene mixed at a volume ratio of 1:1.

Explanation of Symbols

[0192] 100 Preparation System 1 Kettle Body 101 First Inlet 102 Second Inlet 103 Stirring Port 104 Liquid Outlet 1041 First Control Valve 105 Temperature Detection Port 106 pH Meter Port 107 First Housing 108 Top Cover 109 Jacket 1091 First Inlet of Heat Exchange Medium 1092 First Outlet of Heat Exchange Medium 110 First Chamber 2 Inlet Cover 3 Stirrer 301 Stirring Shaft 302 Stirring Blade 4 pH Meter 5 Temperature Sensor 6 Feed Pump 600 First Hose 7 Filtration Device 701 Second Housing 7011 Inlet of Filtration Device 7012 Outlet of Filtration Device 7013 First Part 7014 Second Part 702 Filter Film 8 Liquid Storage Tank 801 Third Housing 8011 Inlet of Liquid Storage Tank 8012 Outlet of Liquid Storage Tank 8013 Second vacuum exhaust port 9 Vacuum exhaust pump 900 Second hose 901 First vacuum exhaust port 10 Glass cover 1001 Fitting surface 11 Triangular mixer 12 Microchannel reactor 13 Kettle reactor 14 Feed liquid 15 Acylation liquid 16 Liquid distributor 1601 Exhaust port 1602 Supply port 1603 Control valve 1604 Container 1605 Discharge port 1701 Adjustment tank 1702 Sedimentation tank 1703 Filtration unit 1704 Extraction unit 1705 Rectification column 1706 Biochemical treatment unit 17061 Aeration tank 17602 Secondary sedimentation tank 1707 Dissolution tank 1708 Reaction kettle 1801 Wash oil 1802 Naphthalene fraction light oil 1803 Methylnaphthalene concentrated fraction 1804 Heavy fraction oil 1805 Azeotropic distillate 1806 Residual oil 1807 Azeotropic agent mixture 1808 Methylnaphthalene crude product 1809 Water 1810 Azeotropic agent 1811 Heating and cooling medium 1812 Residual mother liquor 1813 Methylnaphthalene product 1814 Temperature control medium outlet 1815 Temperature control medium inlet 1816 Material inlet 1817 Material outlet 1818 Crystallization plate temperature control medium inlet 1819 Crystallization plate temperature control medium outlet 1820 Protrusion 1821 Groove 1822 Helical groove V1 Wash oil storage tank V2 Atmospheric distillation column V3 Azeotropic distillation column V4 Ultrasonic static mixer V5 Separator V6 Distillation column V7 Oil bath with digital temperature control V8 Batch melting crystallizer.

Claims

1. A method for continuously synthesizing acylnaphthalene, comprising: mixing a raw material liquid containing 2-methylnaphthalene and an acylation liquid to obtain an acylation reaction liquid, wherein the acylation liquid contains a solvent, an acylating agent, and a Lewis catalyst, and in the acylation reaction liquid, the molar ratio of 2-methylnaphthalene: the acylating agent: the Lewis catalyst is 1:1.3:1.5; the acylation reaction liquid successively enters a microchannel reactor and a tank reactor in which a plurality of tanks are connected in series to carry out an acylation reaction, and then the reaction liquid flowing out of the tank reactor enters a tubular reactor in a hydrolysis section to carry out hydrolysis, and 2-methyl-6-propionylnaphthalene is obtained by rectification and crystallization of the liquid after the hydrolysis reaction; A method for continuously synthesizing acylnaphthalene, characterized by the above.

2. Injecting the raw material liquid and the acylation liquid into a three-way mixer through a syringe for mixing; the three-way mixer and the microchannel reactor are arranged in a first constant temperature bath, and the temperature is controlled at -5 to 0 °C, and the tank reactor is arranged in a second constant temperature bath, and the temperature is controlled at 30 to 50 °C; The method according to claim 1, characterized by the above.

3. Two to four tank reactors are provided and connected in series with each other; the total residence time of the acylation reaction liquid in the tank reactor is 50 to 80 min; The method according to claim 1, characterized by the above.

4. In the hydrolysis reaction, in the hydrolysis section, before passing the reaction liquid flowing out of the tank reactor through the hydrolysis section, water is passed through the aqueous phase pipeline of the hydrolysis section. When water flows out from the outlet of the hydrolysis section, the reaction liquid flowing out of the tank reactor is further passed through the oil phase pipeline of the hydrolysis section, rapidly mixed with water in a low-temperature cold bath, and then enters the tubular reactor to carry out a hydrolysis reaction. The mixed liquid after hydrolysis flows out from the outlet of the tubular reactor. At this stage, water always maintains a flowing state until the mixed liquid is completely discharged, realizing the synchronous progress of the hydrolysis reaction and the acylation reaction; The method according to claim 1.

5. The hydrolysis reaction further includes the step of collecting the mixed liquid using a liquid separator to separate the aqueous phase and the oil phase; The method according to claim 4, characterized by the above.

6. Start the water injection pump and pass water through the aqueous phase pipeline in the hydrolysis section to control the flow rate of water in the aqueous phase pipeline to 3 - 15 mL / min. The temperature of the low-temperature cold bath is 0 - 20 °C. The reaction temperature of the tubular reactor is 30 - 40 °C. The method according to claim 4, characterized in that.

7. Further comprising an acylated wastewater treatment step, specifically: Adjust the pH of the aqueous phase separated by the liquid separator to be alkaline to obtain a suspension containing aluminum hydroxide precipitate, and filter the suspension to obtain aluminum hydroxide filter cake and filtrate; After adjusting the pH of the filtrate to be acidic, transfer it to an extraction solvent, stir and let it stand to obtain a stratified raffinate phase and extraction phase; Biochemically treat the raffinate phase and discharge it after reaching the standard; After subjecting the extraction phase to rectification separation, obtain nitrobenzene and the extraction solvent, reuse the nitrobenzene as an organic solvent, and use the extraction solvent again for extracting the filtrate; Adding the filter cake to concentrated hydrochloric acid, heating and dissolving it, adding an auxiliary agent and then polymerizing to obtain polyaluminum chloride. The method according to claim 5, characterized in that.

8. The method for adjusting the pH of the aqueous phase separated by the liquid separator to be alkaline includes adjusting the pH of the aqueous phase to 8 - 10 using an alkaline raw material, and the alkaline raw material is one or more of sodium hydroxide, potassium hydroxide or liquefied ammonia. The method according to claim 7, characterized in that.

9. The method for adjusting the pH of the filtrate to be acidic includes adjusting the pH of the filtrate to 2 - 3 using an acid, and the acid is one or more of hydrochloric acid, nitric acid or sulfuric acid. The method according to claim 7, characterized in that.

10. The extraction solvent is a non-polar organic solvent, and the volume ratio of the extraction solvent to the filtrate is 0.5 - 5:

1. The extraction solvent is at least one of normal heptane, normal octane, normal hexane, benzene, toluene, xylene, carbon tetrachloride. The method according to claim 7, characterized in that.

11. The temperature of heating and dissolving is 40 - 50 °C, and the weight ratio of the filter cake to concentrated hydrochloric acid is 0.5 - 2.5:

1. The method according to claim 7, characterized in that.

12. The rectification is Feeding the oil phase into the middle part of the first rectification column for rectification, where the light fraction evaporates from the top of the column, is condensed, and then recovered, and the bottom liquid flows out from the bottom of the column; Pressuring and feeding the bottom liquid into the second rectification column while it is hot for further rectification. The light fraction of the second rectification column evaporates from the top of the column, is condensed, and then collected. The product is taken from the side line of the second rectification column. The high-boiling components at the bottom of the column enter the bottom of the column, are heated by the bottom reboiler, and then the high-boiling components at the bottom are pressured and fed into the bottom material collection tank while they are hot. The pressure of the first rectification column is 0.05 kPa to 10 kPa, and the reflux ratio is (1 to 2):1; The condensation temperature of the first rectification column is 10 to 20 °C; The pressure of the second rectification column is 0.05 kPa to 10 kPa, and the reflux ratio is (5 to 10):1; The condensation temperature of the second rectification column is 50 to 90 °C. The method according to claim 11, characterized in that.

13. The 2-methylnaphthalene is extracted from wash oil, with a purity of 99.0% to 99.9%. The extraction method is as follows: Rectifying and separating the wash oil to obtain a methylnaphthalene concentrated fraction; Subjecting the methylnaphthalene concentrated fraction to azeotropic rectification in an azeotropic rectification column to obtain an azeotropic distillate; Passing the azeotropic distillate through a separator to obtain a 2-methylnaphthalene crude product; Subjecting the 2-methylnaphthalene crude product to crystallization and purification of 2-methylnaphthalene by passing it through a plurality of intermittent melting crystallizers installed in parallel connection. The method according to any one of claims 1 to 12, characterized in that.

14. The preparation of the acylating solution includes: Weighing a Lewis catalyst under the protection of an inert gas; Mixing the solvent and the Lewis catalyst to obtain a mixed solution; Adding the acylating solution to the mixed solution. The method according to any one of claims 1 to 13, characterized in that.

15. The method according to claim 14, characterized in that the temperature of the mixed solution is 60 °C or lower.

16. The method according to claim 14, characterized in that suction filtration treatment is performed on the acylating solution under an inert gas atmosphere to remove solid particles.

17. The method according to any one of claims 14 to 16, characterized in that the molar ratio of the acylating agent, the Lewis catalyst, and the solvent is (1.1 - 1.5):(1.3 - 1.7):

5.

18. The method according to any one of claims 14-17, wherein the acylating agent is any one of propionyl chloride, acetyl chloride, acetic anhydride, and propionic anhydride.

19. The Lewis catalyst is AlCl ３ , BF ３ , ZnCl ２ or FeCl ３ The method according to any one of claims 14 to 18, characterized in that it is at least one selected from the group consisting of.

20. The method according to any one of claims 14-19, wherein the solvent is nitrobenzene.

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