Device and method for preparing 2, 6-naphthalic acid

Abstract

The invention provides a device and a method for preparing 2, 6-naphthalic acid. The device comprises an oxidation reactor for carrying out oxidation reaction on acyl naphthalene, a catalyst and air in a solvent, at least two crystallizing tanks for crystallizing and purifying products of the oxidation reaction, and a rectifying tower for carrying out distillation separation on water, the solvent and impurities, the oxidation reactor is a full-backmixing double-sleeve bubbling bed reactor; all the crystallizing tanks are connected with the oxidation reactor, the softened water source and the filter; the rectifying tower is connected with the filter and the oxidation reactor, and the rectifying tower is a continuous efficient filler rectifying tower. According to the device for preparing the 2, 6-naphthalic acid, the full-backmixing double-sleeve bubbling bed reactor is used, the purity and yield of products are ideal, through reasonable system configuration and technological process design, whole-process continuous production can be achieved, and the production efficiency is high.

Description

Technical Field

[0001] This application relates to the technical field of refining and purification of fine chemicals, and particularly relates to an apparatus and method for preparing 2,6-naphthalenedicarboxylic acid. Background Art

[0002] Polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and high-performance liquid crystal (LCP) are important raw materials for photovoltaic backsheets, liquid crystal displays, high-performance fibers, and electrical insulation encapsulation processes. The above high-performance polymer materials are respectively prepared by polycondensation reactions of 2,6-naphthalenedicarboxylic acid (2,6-NDA) with ethylene glycol, butanediol, and aromatic polyols. 2,6-NDA is one of the various isomers of naphthalenedicarboxylic acid and has a wide range of applications in the field of fine chemicals as a synthetic raw material. Currently, due to the complex production process and high production cost of 2,6-NDA, the applications of PEN, PBN, and LCP are restricted to a certain extent. Therefore, developing a reasonable synthetic process route for 2,6-NDA and reducing the production cost of 2,6-NDA are of great significance for the large-scale production and application of high-end materials such as PEN, PBN, and LCP.

[0003] Currently, the methods for preparing 2,6-NDA include the Henkel method, the oxidation method of 2,6-dimethylnaphthalene (2,6-DMN), etc. However, when using the Henkel method to prepare 2,6-NDA, a large amount of precious and toxic catalysts such as cadmium are required, with high energy consumption and serious pollution; when using the 2,6-DMN oxidation method to prepare naphthalenedicarboxylic acid, the yield is low, the process flow is complex, and the cost is high, so it is gradually no longer used. Currently, most of the methods for preparing 2,6-NDA from 2-methyl-6-propionylnaphthalene use continuous or indirect single reactors, with low production efficiency and high costs.

[0004] Specifically, in the related art, some use 2,6-dimethylnaphthalene as a reaction raw material, and carry out a carboxylation reaction with air under the action of a catalyst containing bromine, cobalt and manganese, and obtain 2,6-naphthalenedicarboxylic acid after cooling crystallization, centrifugal filtration and drying. The catalyst used in this method does not contain alkali metal cations, the reaction conditions are mild (reaction temperature 80-120 °C), the purity of the obtained 2,6-naphthalenedicarboxylic acid is low (90.8-93.5%), and the yield is not high; moreover, the entire process uses batch equipment, with low production efficiency and high operating costs, and is only suitable for laboratories and not suitable for industrial production. Some are prepared by a two-step method. The first step is the selective oxidation of lead tetraacetate in the presence of a catalyst to prepare 6-methyl-2-naphthoic acid, and the second step is the continuous reaction of 6-methyl-2-naphthoic acid to prepare 2,6-naphthalenedicarboxylic acid. This method includes process steps such as one-step oxidation reaction, hydrolysis, acidification, filtration, drying, two-step oxidation reaction, water washing, filtration, and drying, and the operation is very complicated; moreover, the reaction process involves strong acids and strong bases, which have great corrosiveness to equipment and high costs. Still others use a batch high-pressure reactor as a reactor and obtain an oxidation product through an oxidation reaction and freeze crystallization. This method uses compounds of cobalt, manganese, bromine and chromium as catalysts, and the chromium catalyst is highly toxic and harmful to human health; the volume of the reactor used is small, the oxidation product is about 10 g, the calculation error is large, and the purity and yield data are unreliable, and the yield is low. Still others use 2-methyl-6-propionylnaphthalene as a raw material, use a Co-Mn-Br series catalyst as the main catalyst, potassium salt, sodium salt or nickel salt as a co-catalyst in a continuous oxidation reactor, and use one or a mixture of two of glacial acetic acid or propionic acid as a solvent, and continuously introduce an oxygen-containing gas into the oxidation reactor to continuously oxidize 2-methyl-6-propionylnaphthalene to synthesize 2,6-naphthalenedicarboxylic acid. This method uses a batch reactor with stirring, with low efficiency and high costs, and the gas-liquid mass transfer and heat transfer effects in the reactor are poor; the solvent in this method cannot be recycled, and the steps of centrifugal separation, washing and drying result in large material losses, resulting in a low product yield.

[0005] In summary, at present, the preparation of 2,6-naphthalenedicarboxylic acid all uses batch reactors, with poor heat and mass transfer effects, low production efficiency, high operating costs, and is not easy to industrialize. At the same time, the existing technology solvents are not recycled, resulting in low use efficiency of the solvents used in the oxidation reaction and increasing the cost of preparing 2,6-naphthalenedicarboxylic acid. In addition, in the current technologies and methods for preparing 2,6-naphthalenedicarboxylic acid, there is a lack of integrated and continuous devices for reaction and purification, and the obtained 2,6-naphthalenedicarboxylic acid has a low yield and low purity, which is not conducive to engineering scale-up and industrial production. Summary of the Invention

[0006] To solve the problems existing in the existing preparation methods of 2,6-naphthalenedicarboxylic acid, such as batch operation, low production efficiency, high preparation cost, low product purity and yield, an object of the present application is to provide a device for preparing 2,6-naphthalenedicarboxylic acid. By using a fully back-mixed double-sleeve bubble column reactor, the product purity and yield are ideal. Through reasonable system configuration and process flow design, continuous production throughout the process can be achieved, with high production efficiency, providing a design basis and technical support for the subsequent industrial production of 2,6-NDA.

[0007] Another object of the present application is to provide a method for preparing 2,6-naphthalenedicarboxylic acid.

[0008] To achieve the above object, a first aspect of the present application proposes a device for preparing 2,6-naphthalenedicarboxylic acid, including:

[0009] An oxidation reactor for carrying out an oxidation reaction of acyl naphthalene, a catalyst and air in a solvent, and the oxidation reactor is a fully back-mixed double-sleeve bubble column reactor;

[0010] At least two crystallization tanks for crystallizing and purifying the product of the oxidation reaction, and all the crystallization tanks are connected to the oxidation reactor, a softened water source and a filter;

[0011] A distillation column for distilling and separating water, solvent and impurities, and the distillation column is connected to the filter and the oxidation reactor, and the distillation column is a continuous high-efficiency packed distillation column.

[0012] In some embodiments, the oxidation reactor includes a reactor outer cylinder, the reactor outer cylinder has a liquid inlet, an air inlet, a gas outlet and a reaction product outlet, and a baffle plate, a reactor inner cylinder and a flow guide cone are sequentially arranged at certain intervals from top to bottom inside the reactor outer cylinder, and there is a gap between the outer side wall of the reactor inner cylinder and the inner side wall of the reactor outer cylinder.

[0013] In some embodiments, the bottom of the reactor outer cylinder is provided with a liquid inlet and an air inlet, the top is provided with a gas outlet, and the upper end is provided with a reaction product outlet.

[0014] In some embodiments, the top of the flow guide cone extends into the reactor inner cylinder and there is a gap between it and the side wall of the reactor inner cylinder.

[0015] In some embodiments, the baffle plate is an annular baffle plate, and the inner diameter of the baffle plate is equal to the outer diameter of the reactor inner cylinder, and the wall thickness of the baffle plate is 0.5-2 cm.

[0016] In some embodiments, the baffle plate is horizontally arranged.

[0017] In some embodiments, the inner cylinder of the reactor, the outer cylinder of the reactor, the baffle plate, and the baffle cone are coaxially arranged.

[0018] In some embodiments, the wall thickness of the inner cylinder of the reactor is 0.5 - 2 cm, and the inner diameter of the inner cylinder of the reactor is 5 / 8 - 7 / 8 of the inner diameter of the outer cylinder of the reactor.

[0019] In some embodiments, the bottom diameter of the baffle cone is 1.05 - 1.2 times the outer diameter of the inner cylinder of the reactor.

[0020] In some embodiments, the diameters of both the air inlet pipe and the reaction product outlet pipe are 1 / 12 - 1 / 8 of the inner diameter of the outer cylinder of the reactor.

[0021] In some embodiments, the diameter of the liquid inlet pipe is 1 / 25 - 1 / 18 of the inner diameter of the outer cylinder of the reactor.

[0022] In some embodiments, the liquid inlet pipe is connected to the air inlet pipe and they are perpendicular to each other; the top of the air inlet pipe is connected to the bottom of the outer cylinder of the reactor.

[0023] In some embodiments, the crystallization tank has a stirring motor, stirring paddles, a discharging valve, and a jacket; the jacket is arranged around the outside of the crystallization tank, and a cooling medium or a heating medium is stored in the jacket, and the jacket is connected to a liquid temperature control machine through a pipeline.

[0024] In some embodiments, the cooling medium includes at least one of ethylene glycol solution and glycerol solution.

[0025] In some embodiments, the heating medium includes at least one of silicone oil and heat transfer oil.

[0026] In some embodiments, the packing in the distillation column is a high-efficiency corrugated plate structured packing, the corrugation line changes at an angle of 30° - 60° - 30°, the fillet has a smooth transition, the surface is roughened, and the specific surface area is 1500 - 3000 m 2 / m 3 。

[0027] In some embodiments, the apparatus for preparing 2,6-naphthalenedicarboxylic acid further includes:

[0028] A raw material preparation tank for mixing the acyl naphthalene, the solvent, and the catalyst, and the raw material preparation tank is connected to the solvent outlet and the circulation pump of the distillation column;

[0029] A raw material metering tank, and the raw material metering tank is connected to the circulation pump and the raw material preparation tank through a three-way valve;

[0030] A heating furnace, the heating furnace is connected to the raw material metering tank and the oxidation reactor through a feed pump; and / or,

[0031] An air compressor, the air compressor is connected to the oxidation reactor to provide air for the oxidation reaction.

[0032] In some embodiments, the distillation column includes a vacuum system, a condensation system and a heating system.

[0033] In some embodiments, the number of the filters is at least 2, and the filters are operated intermittently.

[0034] In some embodiments, the apparatus for preparing 2,6-naphthalenedicarboxylic acid further includes:

[0035] A heat exchanger, the heat exchanger is connected to the tail gas outlet of the oxidation reactor; and / or,

[0036] A dryer, the dryer is connected to the filter cake outlet of the filter; and / or,

[0037] A filtrate feed pump, the filtrate feed pump is connected to the filtrate outlet of the dryer and the distillation column.

[0038] A second aspect of the present application provides a method for preparing 2,6-naphthalenedicarboxylic acid by using the apparatus for preparing 2,6-naphthalenedicarboxylic acid described in the present application, including:

[0039] Performing an oxidation reaction on the acylnaphthalene, the catalyst and air in a solvent to obtain an oxidation mixture;

[0040] Mixing the oxidation mixture with softened water and then performing crystallization and purification to obtain a crystallization mixture;

[0041] Filtering the crystallization mixture to obtain a filter cake and a filtrate;

[0042] Drying the filter cake to obtain the 2,6-naphthalenedicarboxylic acid;

[0043] Performing rectification separation on the filtrate to obtain the softened water, the solvent and the heavy impurity removal.

[0044] In some embodiments, the performing an oxidation reaction on the acylnaphthalene, the catalyst and air in a solvent includes:

[0045] Mixing the acylnaphthalene, the catalyst and the solvent in the raw material preparation tank to obtain an oxidation raw material liquid;

[0046] Quantitatively transporting, preheating the oxidation raw material liquid and then mixing it with air to obtain the oxidation mixture.

[0047] In some embodiments, the method for preparing 2,6-naphthalenedicarboxylic acid further comprises:

[0048] reusing the softened water obtained by rectification separation as a crystallization aid in the crystallization tank; and / or,

[0049] reusing the solvent obtained by rectification separation as the solvent participating in the oxidation reaction.

[0050] In some embodiments, the acyl naphthalene includes at least one of 2-methyl-6-acetylnaphthalene and 2-methyl-6-propionylnaphthalene.

[0051] In some embodiments, the solvent includes at least one of glacial acetic acid and propionic acid.

[0052] In some embodiments, the mass ratio of the solvent to the acyl naphthalene is (12 - 20):1.

[0053] In some embodiments, the catalyst is a mixture of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide, and the mass ratios of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide in the catalyst are 10 - 20%, 15 - 30%, 15 - 30%, 20 - 40%, and 20 - 40% respectively.

[0054] In some embodiments, the mass dosage of the catalyst is 0.3 - 2% of the total mass dosage of the acyl naphthalene, the catalyst, and the solvent.

[0055] In some embodiments, the air is compressed air, the gas-liquid ratio of the air to the oxidation raw material liquid is 200 - 600, and the oxidation raw material liquid is composed of acyl naphthalene, catalyst, and solvent.

[0056] In some embodiments, the temperature of the oxidation reaction is 180 - 250 °C, the reaction pressure is 1.5 - 3.2 Mpa, and the residence time of the reaction material in the reactor is 20 - 60 min.

[0057] In some embodiments, the added mass of the softened water is 10 - 30% of the mass of the oxidation mixture.

[0058] In some embodiments, during the crystallization and purification process, the cooling rate of freeze crystallization is 3 - 8 °C / h, the final crystallization temperature is 5 - 10 °C, the duration of the final crystallization temperature is 1 - 3 h, stirring is started during the cooling process, the stirring speed is 500 - 800 r / min, and stirring stops when the crystallization tank reaches the final crystallization temperature.

[0059] In some embodiments, the rectification column is a vacuum rectification column, the top pressure is -100 kPa to -20 kPa, the reflux ratio is 15 - 30, the top temperature is 50 - 110 °C, and the bottom temperature is 150 - 200 °C.

[0060] The apparatus for preparing 2,6-naphthalenedicarboxylic acid according to the present application can at least bring the following beneficial effects:

[0061] 1. The oxidation reactor adopts a fully back-mixed double-sleeve bubble column reactor, with continuous operation. The materials in the reactor form a circulating flow, having good heat and mass transfer effects, good oxidation reaction effects, short reaction residence time, high production efficiency, and being easy to scale up in engineering.

[0062] 2. The crystallization tank is used to purify and wash 2,6-naphthalenedicarboxylic acid by the method of cooling crystallization. By adding an appropriate amount of softened water, the size of the crystallization products can be made uniform, avoiding the problem of impurities being entrained due to over-sized crystallization products, and improving the product yield; in addition, the addition of softened water also plays a washing role, washing the catalyst residual impurities in the filter cake into the filtrate, and improving the purity of the 2,6-naphthalenedicarboxylic acid product.

[0063] 3. A continuous high-efficiency packed rectification column is adopted, specifically a high-efficiency corrugated packing rectification column, with continuous operation. The uniquely designed packing has the advantages of high number of theoretical plates per meter, low pressure drop, high production efficiency, and being easy to scale up in engineering. The separation effect of the solvent and softened water is good, and they can be recycled, reducing the production cost.

[0064] The method for preparing 2,6-naphthalenedicarboxylic acid according to the present application, in addition to at least having the beneficial effects of the apparatus for preparing 2,6-naphthalenedicarboxylic acid according to the present application, can at least bring the following beneficial effects:

[0065] 1. A five-component catalyst system is adopted, with high synergistic effect among the components, less catalyst addition amount, and the catalyst does not contain strong acids or strong bases, being green and environmentally friendly.

[0066] 2. The yield of the prepared 2,6-naphthalenedicarboxylic acid product is 88.1 - 93.4%, and the purity reaches 97.5 - 99.2%.

[0067] The additional aspects and advantages of the present application will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present application. Description of the Drawings

[0068] The above-mentioned and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings,

[0069] wherein:

[0070] Figure 1Schematic structural diagram of the apparatus for preparing 2,6-naphthalenedicarboxylic acid shown in an exemplary embodiment of the present application (i.e., the flow chart of the method for preparing 2,6-naphthalenedicarboxylic acid).

[0071] Figure 2 Schematic structural diagram of the oxidation reactor shown in an exemplary embodiment of the present application.

[0072] Figure 3 is Figure 2 Schematic structural diagram of the middle baffle.

[0073] Reference numerals:

[0074] M, stirring motor; V1, raw material preparation tank; V2, raw material metering tank; P1, circulation pump; P2, feed pump; E1, heating furnace; E2, heat exchanger; P3, air compressor; R1, oxidation reactor; V3, crystallization tank; V4, filter; V5, dryer; P4, filtrate feed pump; T1, distillation column;

[0075] 1, raw materials (acylnaphthalene, solvent, catalyst); 2, oxidation raw material liquid; 3, compressed air; 4, tail gas; 5, oxidation mixture; 6, crystallization mixture; 7, filter cake; 8, filtrate; 9, softened water; 10, fresh softened water; 11, recycled solvent; 12, heavy residue (discharged externally); 13, 2,6-naphthalenedicarboxylic acid product;

[0076] R1-1, baffle; R1-2, reactor outer cylinder; R1-3, reactor inner cylinder; R1-4, flow guiding cone; R1-5, liquid inlet; R1-6, air inlet; R1-7, gas outlet; R1-8, reaction product outlet. Detailed description of the specific implementation

[0077] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.

[0078] In the present application, the disclosure of a numerical range includes all values within the entire range and the disclosure of further sub-ranges, including the endpoints and sub-ranges given for these ranges.

[0079] In the present application, the raw materials, equipment, etc. involved, unless otherwise specified, are raw materials and equipment that can be obtained through commercial channels or prepared by known methods; the methods involved, unless otherwise specified, are conventional methods.

[0080] The apparatus for preparing 2,6-naphthalenedicarboxylic acid and the system for preparing 2,6-naphthalenedicarboxylic acid according to an embodiment of the present application will be described below with reference to the accompanying drawings.

[0081] Figure 1Schematic structural diagram of the apparatus for preparing 2,6-naphthalenedicarboxylic acid shown in an exemplary embodiment of the present application (i.e., the flow chart of the method for preparing 2,6-naphthalenedicarboxylic acid).

[0082] <Apparatus for preparing 2,6-naphthalenedicarboxylic acid>

[0083] As Figure 1 shown, the apparatus for preparing 2,6-naphthalenedicarboxylic acid according to the embodiment of the present application includes an oxidation reactor R1, at least two crystallization tanks V3, and a rectification column T1. Among them:

[0084] The oxidation reactor R1 is used for the oxidation reaction of acylnaphthalene, a catalyst, and air in a solvent, and the oxidation reactor R1 is a fully back-mixed double-sleeve bubble column reactor.

[0085] In some embodiments, as Figure 2 shown, the oxidation reactor includes a reactor outer cylinder R1-2, the reactor outer cylinder R1-2 has a liquid inlet R1-5, an air inlet R1-6, a gas outlet R1-7, and a reaction product outlet R1-8. A baffle plate R1-1, a reactor inner cylinder R1-3, and a draft cone R1-4 are sequentially arranged at certain intervals from top to bottom inside the reactor outer cylinder R1-2. A gap is left between the outer side wall of the reactor inner cylinder R1-3 and the inner side wall of the reactor outer cylinder R1-2.

[0086] In some embodiments, the bottom of the reactor outer cylinder R1-2 is provided with a liquid inlet R1-5 and an air inlet R1-6, the top is provided with a gas outlet R1-7, and the upper end is provided with a reaction product outlet R1-8.

[0087] In some embodiments, the baffle plate R1-1 is located below the reaction product outlet R1-8.

[0088] In some other embodiments, the baffle plate R1-1 is at the same height as the reaction product outlet R1-8.

[0089] In some embodiments, the top of the draft cone R1-4 extends into the reactor inner cylinder R1-3, and a gap is left between the draft cone R1-4 and the side wall of the reactor inner cylinder R1-3.

[0090] It should be noted that in the embodiments of the present application, the draft cone is also called a draft conical body in some cases.

[0091] In some embodiments, as Figure 3 shown, the baffle plate R1-1 is an annular baffle plate, and the inner diameter of the baffle plate R1-1 is equal to the outer diameter of the reactor inner cylinder. The wall thickness of the baffle plate R1-1 is 0.5-2 cm.

[0092] In the embodiments of the present application, the wall thickness of the deflector refers to the distance from the inner hole wall of the annular deflector to the outer circumferential wall.

[0093] Exemplarily, the wall thickness of the deflector R1-1 includes, but is not limited to, 1 cm or 1.5 cm, etc.

[0094] In some embodiments, the deflector R1-1 is horizontally arranged.

[0095] In some embodiments, the outer circumferential wall of the deflector R1-1 is fixed on the inner wall of the reactor outer cylinder R1-2.

[0096] In some embodiments, there are gaps between the reactor inner cylinder R1-3 and the deflector cone R1-4, between the deflector cone R1-4 and the bottom of the reactor outer cylinder R1-2, and between the deflector cone R1-4 and the inner side wall of the reactor outer cylinder R1-2.

[0097] In some embodiments, the reactor outer cylinder R1-2 is a closed hollow shell, and the reactor inner cylinder R1-3 is a tubular structure arranged inside it and parallel to its side wall. At this time, the gap between the inner side wall of the reactor outer cylinder R1-2 and the outer side wall of the reactor inner cylinder R1-3 is an annular or quasi-annular gap.

[0098] In some embodiments, the reactor inner cylinder R1-3, the reactor outer cylinder R1-2, the deflector R1-1 and the deflector cone R1-4 are coaxially arranged.

[0099] In some embodiments, the wall thickness of the reactor inner cylinder R1-3 is 0.5 - 2 cm, including, but is not limited to, 1 cm or 1.5 cm, etc.

[0100] In some embodiments, the inner diameter of the reactor inner cylinder R1-3 is 5 / 8 - 7 / 8 of the inner diameter of the reactor outer cylinder R1-2, including, but is not limited to, 3 / 4, etc.

[0101] In some embodiments, the bottom diameter of the deflector cone R1-4 is 1.05 - 1.2 times the outer diameter of the reactor inner cylinder R1-3, including, but is not limited to, 1.1 times or 1.15 times, etc.

[0102] In some embodiments, the diameters of both the air inlet R1-6 pipe and the reaction product outlet R1-8 pipe are 1 / 12 - 1 / 8 of the inner diameter of the reactor outer cylinder R1-2, including, but is not limited to, 1 / 11, 1 / 10 or 1 / 9, etc.

[0103] In some embodiments, the diameter of the liquid inlet R1-5 pipe is 1 / 25 - 1 / 18 of the inner diameter of the reactor outer cylinder R1-2, including, but is not limited to, 1 / 24, 1 / 22 or 1 / 20, etc.

[0104] In some embodiments, the liquid inlet R1-5 pipe communicates with the air inlet R1-6 pipe, and the two are vertically arranged; the top of the air inlet R1-6 pipe is connected to the bottom of the outer cylinder R1-2 of the reactor.

[0105] In the embodiments of the present application, the crystallization tank mainly crystallizes and purifies the products of the oxidation reaction. The crystallization tank operates intermittently. At least two crystallization tanks are provided, with at least one in use and one in reserve, and they are used alternately to achieve continuous operation of the entire process flow.

[0106] In some embodiments, all the crystallization tanks V3 are connected to the oxidation reactor R1, the softened water source, and the filter V4.

[0107] In some embodiments, the crystallization tank V3 is provided with a stirring motor M, a stirring paddle, a discharge valve, and a jacket; the jacket is provided around the outside of the crystallization tank V3, and a cooling medium or a heating medium is stored in the jacket, and the jacket is connected to a liquid temperature control machine through a pipe.

[0108] Exemplarily, the rotation speed of the stirring paddle is 500-800 r / min.

[0109] Exemplarily, the discharge valve is connected to the filter V4.

[0110] In some embodiments, the cooling medium includes but is not limited to at least one of ethylene glycol solution, glycerol solution, etc.

[0111] Exemplarily, the ethylene glycol solution is a mixed solution of ethylene glycol and water in a mass ratio of 1:1.

[0112] Exemplarily, the glycerol solution is a mixed solution of glycerol and water in a mass ratio of 1:1.

[0113] In some embodiments, the heating medium includes but is not limited to at least one of silicone oil, heat transfer oil, etc.

[0114] Exemplarily, the crystallization tank is provided with a mixture feeding port, a softened water inlet, etc., and the softened water inlet is connected to the softened water source.

[0115] In the embodiments of the present application, the main function of the filter is to perform solid-liquid separation.

[0116] In some embodiments, the number of the filters V4 is at least 2, and the filters V4 operate intermittently.

[0117] Specifically, at least one of the multiple filters V4 is in use and one is in reserve. Similar to the crystallization tank, a single filter operates intermittently, and the multiple filters are used alternately to achieve continuous operation of the entire process flow.

[0118] Exemplarily, the filter is a plate and frame filter.

[0119] In the embodiments of the present application, the main function of the rectification column is to perform the distillation separation of water, solvent, and impurities, and recover the softened water and solvent therein so that they can be recycled.

[0120] In some embodiments, the rectification column T1 is connected to the filter V4 and the oxidation reactor R1, and the rectification column T1 is a continuous high-efficiency packed rectification column T1.

[0121] In some embodiments, the rectification column T1 includes a vacuum system, a condensation system, and a heating system. The structural selection of the vacuum system, the condensation system, and the heating system, etc. are all conventional settings in the art and will not be elaborated here.

[0122] In some embodiments, the packing in the rectification column T1 is a high-efficiency corrugated plate structured packing, the corrugation line changes at an angle of 30°-60°-30°, the fillet has a smooth transition, the surface is roughened, and the specific surface area is 1500-3000m 2 / m 3 .

[0123] Exemplarily, the specific surface area of the packing in the rectification column T1 includes but is not limited to 2000m 2 / m 3 or 2500m 2 / m 3 etc.

[0124] In some embodiments, the rectification column is a continuous high-efficiency packed rectification column.

[0125] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a raw material preparation tank V1.

[0126] In the embodiments of the present application, the main function of the raw material preparation tank is to prepare the oxidation raw material liquid (that is, the mixing of acyl naphthalene, solvent, and catalyst).

[0127] In some embodiments, the raw material preparation tank is equipped with a heating jacket, a circulation pump, a three-way valve, a stirring motor M, and a stirring paddle. The temperature control range of the material in the tank is 70-100°C, and the stirring speed is 600-1000r / min.

[0128] In some embodiments, the raw material preparation tank V1 is connected to the solvent outlet of the rectification column T1 and the circulation pump P1.

[0129] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a raw material metering tank V2.

[0130] In the embodiments of the present application, the main function of the raw material metering tank is to quantitatively transport materials, and it is equipped with a heating jacket, a circulation pump, a stirring motor M and a stirring paddle. The temperature control range of the materials in the tank is 70 - 100 °C, and the stirring speed is 600 - 1000 r / min.

[0131] It should be noted that the materials in the raw material preparation tank need to be stirred for more than 4 hours before being fed into the raw material metering tank. The stirring in the raw material metering tank continues throughout the preparation process of 2,6-naphthalenedicarboxylic acid.

[0132] In some embodiments, the raw material metering tank V2 is connected to the circulation pump P1 and the raw material preparation tank V1 through a three-way valve.

[0133] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a heating furnace E1.

[0134] In the embodiments of the present application, the main function of the heating furnace is to preheat the oxidation raw material liquid from the raw material metering tank V2. It is a coil-type heating furnace, and the heating temperature is 150 - 190 °C.

[0135] In some embodiments, the heating furnace E1 is connected to the raw material metering tank V2 and the oxidation reactor R1 through a feed pump P2.

[0136] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes an air compressor P3, and the air compressor P3 is connected to the oxidation reactor R1 to provide air for the oxidation reaction, specifically compressed air.

[0137] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a heat exchanger E2, and the heat exchanger E2 is connected to the tail gas outlet of the oxidation reactor R1.

[0138] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a dryer V5, and the dryer V5 is connected to the filter cake outlet of the filter V4.

[0139] In the embodiments of the present application, the main function of the dryer is to dry the filter cake, and the drying temperature is 100 - 150 °C.

[0140] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid further includes a filtrate feed pump P4P2, and the filtrate feed pump P4P2 is connected to the filtrate outlet of the dryer V5 and the rectification column T1. Specifically, the rectification column inlet is connected through a valve, a pipeline and the filtrate feed pump outlet.

[0141] In some embodiments, the device for preparing 2,6-naphthalenedicarboxylic acid in the embodiments of the present application further includes accessory pipelines, valves and other spare parts.

[0142] A method for preparing 2,6-naphthalenedicarboxylic acid by using the apparatus for preparing 2,6-naphthalenedicarboxylic acid according to the embodiments of the present application includes the following steps:

[0143] S101. Performing an oxidation reaction on the acyl naphthalene, the catalyst, and air in a solvent to obtain an oxidation mixture 5.

[0144] S102. Mixing the oxidation mixture 5 with softened water and then performing crystallization purification to obtain a crystallization mixture 6.

[0145] S103. Filtering the crystallization mixture 6 to obtain a filter cake 7 and a filtrate 8.

[0146] S104. Drying the filter cake 7 to obtain the 2,6-naphthalenedicarboxylic acid 13.

[0147] S105. Performing rectification separation on the filtrate 8 to obtain the softened water, the solvent, and the heavy impurity removal.

[0148] Among them, the order of step S104 and step S105 can be adjusted according to needs, or they can be performed simultaneously.

[0149] In some embodiments, in step S101, the performing an oxidation reaction on the acyl naphthalene, the catalyst, and air in a solvent includes the following steps:

[0150] (1) Mixing the acyl naphthalene, the catalyst, and the solvent in the raw material preparation tank V1 to obtain an oxidation raw material liquid 2.

[0151] (2) Quantitatively transporting, preheating the oxidation raw material liquid 2 obtained in step (1), and mixing it with air to obtain the oxidation mixture.

[0152] In some embodiments, the quantitative transportation in step (1) is achieved through a raw material metering tank V2 and a feed pump P2.

[0153] Specifically, acylnaphthalene, a catalyst, and a solvent form Feedstock 1. The preparation process of the oxidation feedstock liquid from Feedstock 1 is carried out in the feedstock preparation tank V1. First, close the three-way valve at the outlet of the circulation pump P1 of the preparation tank leading to the feedstock metering tank V2 to make the three-way valve in the circulation state. Then, add acylnaphthalene, the solvent, and the catalyst into the feedstock preparation tank V2 through the material inlet in a certain proportion, start the agitation of the feedstock preparation tank V1, and start the bottom circulation pump P1 of the feedstock preparation tank V1 to circulate the materials in the feedstock preparation tank V1. After all the raw materials are added, after agitation and circulation for a certain period of time, the materials are evenly mixed before feeding into the feedstock metering tank V2. Subsequently, the evenly mixed oxidation feedstock liquid is pumped into the feedstock metering tank V2 through the three-way valve at the outlet of the circulation pump P1 of the feedstock preparation tank V1. When the volume of the materials in the feedstock metering tank V2 reaches 90% of the tank volume, stop feeding. Start the agitation of the feedstock metering tank V2 and start the metering pump (i.e., the feed pump P2), and then the oxidation feedstock liquid can be quantitatively transported to the oxidation reactor at a certain flow rate.

[0154] In some embodiments, the preheating in step (2) is carried out in the heating furnace E1.

[0155] Specifically, after the oxidation feedstock liquid 2 is preheated to a certain temperature in the heating furnace, it is mixed with compressed air 3 and then enters the oxidation reactor. The oxidation reaction takes place in the oxidation reactor, which is a full backmixing double-sleeve bubble column reactor. Due to the density difference between the inner cylinder and the annulus (the aforementioned annular or quasi-annular gap) of the reactor, the materials form a circulating flow along the inner cylinder of the reactor, reaching the full backmixing state. In the oxidation reactor, the oxidation feedstock liquid 2 undergoes an oxidation reaction to obtain an oxidation mixture 5, and the gas after the oxidation reaction is cooled by the heat exchanger E2 to form the tail gas 4 discharged to the atmosphere.

[0156] In some embodiments, in step S101, the acylnaphthalene includes but is not limited to at least one of 2-methyl-6-acetylnaphthalene, 2-methyl-6-propionylnaphthalene, etc.

[0157] In some embodiments, in step S101, the solvent includes but is not limited to at least one of glacial acetic acid, propionic acid, etc.

[0158] In some embodiments, in step S101, the mass ratio of the solvent to the acylnaphthalene is (12 - 20):1, including but not limited to 13:1, 15:1, or 18:1, etc.

[0159] In some embodiments, in step S101, the catalyst is a mixture of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide.

[0160] Exemplarily, the mass ratios (i.e., mass percentages) of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide in the catalyst are 10-20%, 15-30%, 15-30%, 20-40%, and 20-40% respectively.

[0161] Exemplarily, the mass ratio of cobalt acetate in the catalyst includes but is not limited to 12.5%, 15%, 17.5%, etc.

[0162] Exemplarily, the mass ratio of manganese acetate in the catalyst includes but is not limited to 17.5%, 20%, 25%, etc.

[0163] Exemplarily, the mass ratio of manganese oxide in the catalyst includes but is not limited to 17.5%, 20%, 25%, etc.

[0164] Exemplarily, the mass ratio of potassium bromide in the catalyst includes but is not limited to 25%, 30%, 35%, etc.

[0165] Exemplarily, the mass ratio of sodium bromide in the catalyst includes but is not limited to 25%, 30%, 35%, etc.

[0166] In some embodiments, the mass dosage of the catalyst is 0.3-2% of the total mass of acylnaphthalene, the catalyst, and the solvent (i.e., the total mass of the aforementioned oxidation raw material liquid), including but not limited to 0.5%, 1%, 1.5%, etc.

[0167] In some embodiments, in step S101, the air is compressed air, and the gas-liquid ratio of the air to the oxidation raw material liquid is 200-600, including but not limited to 300, 400, 500, etc.

[0168] It should be noted that the above gas-liquid ratio is the gas-liquid ratio of the air entering the oxidation reactor to participate in the oxidation reaction and the oxidation raw material liquid.

[0169] In some embodiments, in step S101, the temperature of the oxidation reaction is 180-250 °C, including but not limited to 200 °C, 225 °C, etc.

[0170] In some embodiments, in step S101, the reaction pressure of the oxidation reaction is 1.5-3.2 Mpa, including but not limited to 2 Mpa, 2.5 Mpa, 3 Mpa, etc.

[0171] In some embodiments, in step S101, the residence time of the reaction materials in the reactor for the oxidation reaction is 20-60 min, including but not limited to 30 min, 40 min, 50 min, etc.

[0172] In some embodiments, in step S102, the oxidation mixture flows into the crystallization tank from the outlet at the upper part of the oxidation reactor, and after being mixed with a certain amount of softened water in the crystallization tank, crystallization purification is carried out.

[0173] It should be noted that the softened water in step S102 is initially fresh softened water 10. When the softened water 9 in the subsequent distillation column is recycled to the crystallization tank, the softened water in step S102 can be fresh softened water 10 and softened water 9, or just softened water 9.

[0174] In some embodiments, in step S102, the added mass of the softened water is 10 - 30% of the mass of the oxidation mixture, including but not limited to 15%, 20% or 25%, etc.

[0175] In some embodiments, during the crystallization purification process, the cooling rate of freeze crystallization is 3 - 8 °C / h, the final crystallization temperature is 5 - 10 °C, the duration of the final crystallization temperature is 1 - 3 h, stirring is started during the cooling process, the stirring speed is 500 - 800 r / min, and stirring stops when the crystallization tank V3 reaches the final crystallization temperature.

[0176] Exemplarily, the cooling rate of freeze crystallization includes but is not limited to 4 °C / h, 5 °C / h or 6 °C / h, etc.

[0177] Exemplarily, the final crystallization temperature includes but is not limited to 7 °C or 9 °C, etc.

[0178] Exemplarily, the duration of the final crystallization temperature includes but is not limited to 1.5 h, 2 h or 2.5 h, etc.

[0179] Exemplarily, during the crystallization purification process, the stirring speed includes but is not limited to 600 r / min or 700 r / min, etc.

[0180] In some embodiments, in step S103, the material in the crystallization tank obtains a crystallization mixture after cooling crystallization, and the crystallization mixture enters the filter, and solid-liquid separation is carried out in the filter to obtain a filter cake and a filtrate.

[0181] In some embodiments, in step S103, the filtration is pressure filtration, the filtration pressure is 0.5 - 1.0 bar, and the filtration temperature is 10 - 30 °C.

[0182] Exemplarily, the filtration pressure includes but is not limited to 0.6 bar, 0.7 bar or 0.9 bar, etc.

[0183] Exemplarily, the filtration temperature includes but is not limited to 15 °C, 20 °C or 25 °C, etc.

[0184] In some embodiments, in step S104, the filter cake obtained in step S103 enters a dryer for drying. After drying for a certain period of time, a qualified 2,6-naphthalenedicarboxylic acid product is obtained.

[0185] In some embodiments, in step S104, the drying temperature is 100 - 150 °C, the drying time is 1 - 3 h, the purity of the obtained 2,6-naphthalenedicarboxylic acid is 97.5 - 99.2%, and the yield is 88.1 - 93.4%.

[0186] Exemplarily, the drying temperature includes but is not limited to 110 °C, 130 °C, or 140 °C, etc.

[0187] Exemplarily, the drying time includes but is not limited to 1.5 h or 2 h, etc.

[0188] In some embodiments, the method for preparing 2,6-naphthalenedicarboxylic acid further includes: recycling the softened water obtained by rectification separation to the crystallization tank V3 as a crystallization aid.

[0189] In some embodiments, the method for preparing 2,6-naphthalenedicarboxylic acid further includes: recycling the solvent obtained by rectification separation as the solvent participating in the oxidation reaction.

[0190] As an optional example, the filtrate obtained in step S103 enters the rectification tower T1 through the filtrate feed pump P4 for continuous and efficient rectification. Softened water 9, solvent (i.e., recycled solvent 11), and heavy impurity removal are distilled out in sequence. The distilled softened water and solvent are recycled. The softened water is re-added to the crystallization tank V3 as a crystallization aid, and the solvent is re-added to the raw material preparation tank V1 for raw material preparation. The bottom residual liquid containing impurities that is not distilled out (i.e., heavy residual liquid 12) is discharged.

[0191] In some embodiments, the rectification tower T1 is a vacuum rectification tower T1, the top pressure is -100 kPa to -20 kPa, the reflux ratio is 15 - 30, the top temperature is 50 - 110 °C, and the bottom temperature is 150 - 200 °C.

[0192] As an optional example, as Figure 2 shown, the method for preparing 2,6-naphthalenedicarboxylic acid using the 2,6-naphthalenedicarboxylic acid preparation device of the embodiment of the present application includes:

[0193] Raw materials 1 such as acylnaphthalene, solvent, catalyst, etc. are added into the raw material preparation tank V1 through the material inlet. Start the agitation of the preparation tank and start the circulation pump P1 to mix the materials evenly. After the materials are mixed evenly, open the three-way valve at the outlet of P1 to pump the prepared oxidation raw material liquid into the raw material metering tank V2. Start the agitation of the raw material metering tank and start the feed pump P2 to pump the oxidation raw material liquid 2 into the oxidation reactor R1 through the heating furnace E1. The oxidation raw material liquid undergoes an oxidation reaction with the compressed air from the air compressor P3 in the oxidation reactor R1. After the reaction, the gas is cooled by the heat exchanger E2 and then the tail gas 4 is discharged into the atmosphere. The solid-liquid mixture after the reaction (i.e., the oxidation mixture) is discharged into the crystallization tank V3. Fresh softened water 10 and recycled softened water 9 are added to the crystallization tank V3, and then the materials in the crystallization tank V3 are cooled for crystallization. The obtained crystallization mixture 6 after crystallization is subjected to solid-liquid separation in the filter V4. The obtained filter cake 7 enters the dryer V5 for drying treatment, and finally the 2,6-naphthalenedicarboxylic acid product 13 is obtained. The filtrate 8 obtained from the filter V4 is pumped into the distillation column T1 by the filtrate feed pump P4. Distillation separation is carried out in the distillation column. Softened water 9 is obtained at the top of the column for recycling, the solvent obtained from the side line is recycled for preparing the raw material liquid, and the heavy residue 12 obtained at the bottom of the column is discharged.

[0194] The device and method for preparing 2,6-naphthalenedicarboxylic acid described in this application can at least bring the following beneficial effects:

[0195] 1. The oxidation reactor adopts a full backmix double-sleeve bubble column reactor, with continuous operation. The materials in the reactor form a circulating flow, having good heat and mass transfer effects, good oxidation reaction effects, short reaction residence time, high production efficiency, and being easy to scale up for engineering.

[0196] 2. The crystallization tank is used to purify and wash 2,6-naphthalenedicarboxylic acid by the method of cooling crystallization. By adding an appropriate amount of softened water, the size of the crystallization product can be made uniform, avoiding the problem of the crystallization product entraining impurities due to excessive size, and improving the product yield; in addition, the addition of softened water also plays a washing role, washing the catalyst residual impurities in the filter cake into the filtrate, and improving the purity of the 2,6-naphthalenedicarboxylic acid product.

[0197] 3. A continuous high-efficiency packed distillation column is adopted, specifically a high-efficiency corrugated packing distillation column, with continuous operation. The uniquely designed packing has the advantages of high number of theoretical plates per meter, low pressure drop, high production efficiency, and being easy to scale up for engineering. The separation effect of the solvent and softened water is good and can be recycled, reducing the production cost.

[0198] 4. A five-component catalyst system is adopted, with a high synergistic effect among the components, a small amount of catalyst added, and the catalyst does not contain strong acids or strong bases, being green and environmentally friendly.

[0199] 5. The yield of the prepared 2,6-naphthalenedicarboxylic acid product is 88.1 - 93.4%, and the purity reaches 97.5 - 99.2%.

[0200] Certain features of the present technology are further illustrated in the following non-limiting examples.

[0201] The method for preparing 2,6-naphthalenedicarboxylic acid in each of the following examples is carried out using the device for preparing 2,6-naphthalenedicarboxylic acid in the examples of the present application.

[0202] Example 1

[0203] The method for preparing 2,6-naphthalenedicarboxylic acid in this example includes the following steps:

[0204] As Figure 2 shown, the raw material 1-acylnaphthalene, the solvent, and the catalyst are added into the raw material preparation tank V1 through the material inlet. Start the agitation of the preparation tank and start the circulation pump P1 to make the materials mix evenly. After the materials are mixed evenly, open the three-way valve at the outlet of P1 and pump the prepared oxidation raw material liquid into the raw material metering tank V2. Start the agitation of the raw material metering tank and start the feed pump P2 to pump the oxidation raw material liquid 2 into the oxidation reactor R1 through the heating furnace E1. The oxidation raw material liquid undergoes an oxidation reaction with the compressed air from the air compressor P3 in the oxidation reactor R1. After the reaction, the gas is cooled by the heat exchanger E2 and then forms the tail gas 4 which is discharged into the atmosphere. The solid-liquid mixture after the reaction (i.e., the oxidation mixture 5) is discharged into the crystallization tank V3. Fresh softened water 10 and recycled softened water 9 are added to the crystallization tank V3, and then the materials in the crystallization tank V3 are cooled for crystallization. The crystallization mixture 6 obtained after crystallization is subjected to solid-liquid separation in the filter V4. The obtained filter cake 7 enters the dryer V5 for drying treatment, and finally the 2,6-naphthalenedicarboxylic acid product 13 is obtained. The filtrate 8 obtained from the filter V4 is pumped into the distillation column T1 by the filtrate feed pump P4. Distillation separation is carried out in the distillation column. Softened water 9 is obtained at the top of the column for recycling, the solvent obtained from the side line is recycled for preparing the raw material liquid, and the heavy residue liquid 12 obtained at the bottom of the column is discharged.

[0205] Among them:

[0206] The acylnaphthalene is 2-methyl-6-acetylnaphthalene, the solvent is propionic acid; the catalyst is a mixture of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide. The mass contents of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide in the catalyst are 15%, 20%, 20%, 25%, and 20% respectively; the mass ratio of the solvent to the acylnaphthalene is 16:1, and the mass content of the catalyst in the oxidation raw material liquid is 1.2%.

[0207] In the raw material preparation tank V1, the material preparation temperature is 85 °C, the agitation speed is 800 r / min, and the agitation time is 5 h.

[0208] In the raw material metering tank V2, the material temperature is controlled at 85 °C, the stirring speed is 800 r / min, and continuous stirring is carried out throughout the preparation process of 2,6-naphthalenedicarboxylic acid.

[0209] The heating temperature of the heating furnace E1 is 170 °C.

[0210] The oxidation reactor is a fully back-mixed double-sleeve bubble column reactor as shown in Figure 2-3 The inner cylinder R1-3 of the reactor, the outer cylinder R1-2 of the reactor, the baffle R1-1 and the draft cone R1-4 are coaxially arranged. The wall thickness of the inner cylinder R1-3 of the reactor is 1 cm, and the inner diameter of the inner cylinder R1-3 of the reactor is 3 / 4 of the inner diameter of the outer cylinder R1-2 of the reactor. The bottom diameter of the draft cone R1-4 is 1.1 times the outer diameter of the inner cylinder R1-3 of the reactor. The diameters of the air inlet R1-6 pipe and the reaction product outlet R1-8 pipe are both 1 / 10 of the inner diameter of the outer cylinder R1-2 of the reactor. The diameter of the liquid inlet R1-5 pipe is 1 / 20 of the inner diameter of the outer cylinder R1-2 of the reactor. The inner diameter of the baffle R1-1 is equal to the outer diameter of the inner cylinder R1-3 of the reactor, and the wall thickness of the baffle R1-1 is 1 cm; the baffle R1-1 is horizontally arranged.

[0211] In the oxidation reactor, the oxidation reaction temperature is 215 °C, the reaction pressure is 2 Mpa, the residence time of the reaction material in the reactor is 40 min, and the gas-liquid ratio of the compressed air and the oxidation raw material liquid is 400.

[0212] In the crystallization tank V3, the mass ratio of fresh softened water 10 and recycled softened water 9 is 1:5, and their total mass is 20% of the solid-liquid mixture (i.e., oxidation mixture 5); the freezing crystallization cooling rate is 5.5 °C / h, the final crystallization temperature is 7.5 °C, the duration of the final crystallization temperature is 2 h, stirring is started during the cooling process, the stirring speed is 650 r / min, and the stirring is stopped when the crystallization tank reaches the final crystallization temperature.

[0213] In the filter V4, the filtration is pressure filtration, the filtration pressure is 0.8 bar, and the filtration temperature is 20 °C.

[0214] In the dryer V5, the drying temperature is 125 °C and the drying time is 2 h. After testing by liquid chromatography, the purity of the obtained 2,6-naphthalenedicarboxylic acid is 97.9% and the yield is 92.5%.

[0215] The distillation column T1 is a continuous high-efficiency packed distillation column, and the packing is high-efficiency corrugated plate structured packing. The corrugation line changes at an angle of 30°-60°-30°, the fillet has a smooth transition, the surface is roughened, and the specific surface area is 2400 m 2 / m 3; The rectifying column T1 is a vacuum distillation column with a top pressure of -50 kPa, a reflux ratio of 22, a top temperature of 80 °C, and a bottom temperature of 180 °C.

[0216] Example 2 (compared with Example 1, the key dimensions of the oxidation reactor are different - the annular gap is increased, and the bottom diameter of the flow guiding cone is increased)

[0217] This example is basically the same as Example 1, except that:

[0218] In the oxidation reactor: the inner diameter of the reactor inner cylinder R1-3 is 5 / 8 of the inner diameter of the reactor outer cylinder R1-2, and the bottom diameter of the flow guiding cone R1-4 is 1.2 times the outer diameter of the reactor inner cylinder R1-3.

[0219] Tested by liquid chromatography, the purity of 2,6-naphthalenedicarboxylic acid obtained is 98.3%, and the yield is 90.6%.

[0220] Example 3 (compared with Example 1, the key dimensions of the oxidation reactor are different - the annular gap is decreased, and the bottom diameter of the flow guiding cone is decreased)

[0221] This example is basically the same as Example 1, except that:

[0222] In the oxidation reactor: the inner diameter of the reactor inner cylinder R1-3 is 7 / 8 of the inner diameter of the reactor outer cylinder R1-2, and the bottom diameter of the flow guiding cone R1-4 is 1.05 times the outer diameter of the reactor inner cylinder R1-3.

[0223] Tested by liquid chromatography, the purity of 2,6-naphthalenedicarboxylic acid obtained is 97.6%, and the yield is 90.8%.

[0224] Example 4 (compared with Example 1, the oxidation reaction conditions are different)

[0225] This example is basically the same as Example 1, except that:

[0226] In the oxidation reactor, the oxidation reaction temperature is 180 °C, the reaction pressure is 1.5 Mpa, the residence time of the reaction materials in the reactor is 20 min, and the gas-liquid ratio of the compressed air and the oxidation raw material liquid is 200.

[0227] Tested by liquid chromatography, the purity of 2,6-naphthalenedicarboxylic acid obtained is 98.8%, and the yield is 89.4%.

[0228] Example 5 (compared with Example 1, the catalyst ratio is different)

[0229] This example is basically the same as Example 1, except that:

[0230] The mass contents of cobalt acetate, manganese acetate, manganese oxide, potassium bromide, and sodium bromide in the catalyst are 10%, 15%, 15%, 30%, and 30% respectively; the mass content of the catalyst in the oxidation raw material liquid is 2%.

[0231] After liquid chromatography test, the purity of 2,6-naphthalenedicarboxylic acid obtained is 99.1%, and the yield is 88.7%.

[0232] Comparative Example 1 (compared with Example 1, the oxidation reactor is an existing conventional reactor)

[0233] This example is basically the same as Example 1, the difference is that:

[0234] The oxidation reactor is an existing batch reactor.

[0235] After liquid chromatography test, the purity of 2,6-naphthalenedicarboxylic acid obtained is 93.8%, and the yield is 86.5%.

[0236] Comparative Example 2 (compared with Example 1, softened water is not added during the crystallization and purification process)

[0237] This example is basically the same as Example 1, the difference is that:

[0238] Fresh softened water 10 and recycled softened water 9 are not added to the crystallization tank.

[0239] After liquid chromatography test, the purity of 2,6-naphthalenedicarboxylic acid obtained is 86.3%, and the yield is 87.6%.

[0240] Comparative Example 3 (compared with Example 1, the catalyst does not contain potassium bromide and sodium bromide)

[0241] This example is basically the same as Example 1, the difference is that:

[0242] The catalyst is a mixture of cobalt acetate, manganese acetate, and manganese oxide mixed in a mass ratio of 1:1:1.

[0243] After liquid chromatography test, the purity of 2,6-naphthalenedicarboxylic acid obtained is 91.2%, and the yield is 88.4%.

[0244] In this application, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0245] Although the embodiments of this application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting this application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A device for preparing 2,6-naphthalenedicarboxylic acid, characterized in that: include: An oxidation reactor, used for carrying out oxidation reaction of acylnaphthalene, catalyst and air in a solvent, wherein the oxidation reactor is a fully back-mixed double-sleeve bubbling bed reactor; At least two crystallization tanks are used to crystallize and purify the product of the oxidation reaction, and all of the crystallization tanks are connected to the oxidation reactor, the softened water source and the filter; A distillation tower is used for distilling and separating water, solvent and impurities. The distillation tower is connected to the filter and the oxidation reactor. The distillation tower is a continuous high-efficiency packed distillation tower.

2. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 1, characterized in that: The oxidation reactor comprises a reactor outer cylinder, which has a liquid inlet, an air inlet, a gas outlet and a reaction product outlet. A guide plate, a reactor inner cylinder and a guide cone are arranged in sequence from top to bottom at a certain interval. A gap is left between the outer wall of the reactor inner cylinder and the inner wall of the reactor outer cylinder.

3. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 2, characterized in that, The reactor outer tube is provided with a liquid inlet and an air inlet at the bottom, a gas outlet at the top, and a reaction product outlet at the upper end; and / or, The top of the guide cone extends into the inner tube of the reactor, and a distance is left between the top of the guide cone and the side wall of the inner tube of the reactor; and / or, The guide plate is an annular guide plate, and the inner diameter of the guide plate is equal to the outer diameter of the inner tube of the reactor, and the wall thickness of the guide plate is 0.5-2 cm; and / or, the guide plate is horizontally arranged; and / or, The reactor inner tube, the reactor outer tube, the guide plate and the guide cone are coaxially arranged; and / or, The wall thickness of the inner cylinder of the reactor is 0.5-2 cm, and the inner diameter of the inner cylinder of the reactor is 5 / 8-7 / 8 of the inner diameter of the outer cylinder of the reactor; The bottom diameter of the guide cone is 1.05-1.2 times the outer diameter of the inner tube of the reactor; and / or, The diameters of the air inlet pipe and the reaction product outlet pipe are both 1 / 12-1 / 8 of the inner diameter of the reactor outer cylinder; and / or, The diameter of the liquid inlet pipe is 1 / 25-1 / 18 of the inner diameter of the reactor outer cylinder; and / or, The liquid inlet pipe is communicated with the air inlet pipe, and the two are vertically arranged; the top of the air inlet pipe is connected to the bottom of the reactor outer tube.

4. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 1, characterized in that: The crystallization tank has a stirring motor, a stirring paddle, a discharge valve and a jacket; the jacket is arranged around the outside of the crystallization tank, and a cooling medium or a heating medium is stored in the jacket, and the jacket is connected to a liquid temperature controller through a pipeline; Preferably, the cooling medium includes at least one of ethylene glycol solution and propylene glycol solution; and / or the heating medium includes at least one of silicone oil and heat transfer oil.

5. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 1, characterized in that: The packing in the distillation tower is a high-efficiency corrugated tube-shaped regular packing, the corrugation line changes at an angle of 30°-60°-30°, the rounded corners are smoothly transitioned, the surface is roughened, and the specific surface area is 1500-3000m 2 / m 3 .

6. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 1, characterized in that: The device for preparing 2,6-naphthalenedicarboxylic acid also includes: A raw material preparation tank, used for mixing the acylnaphthalene, the solvent and the catalyst, wherein the raw material preparation tank is connected to the solvent outlet of the distillation tower and a circulation pump; A raw material metering tank, wherein the raw material metering tank is connected to a circulation pump and the raw material preparation tank via a three-way valve; A heating furnace, wherein the heating furnace is connected to the raw material metering tank and the oxidation reactor via a feed pump; and / or, An air compressor is connected to the oxidation reactor to provide air for the oxidation reaction.

7. The device for preparing 2,6-naphthalenedicarboxylic acid according to claim 1, characterized in that: The distillation tower comprises a vacuum system, a condensation system and a heating system; and / or, The number of the filters is at least 2, and the filters are operated intermittently; and / or, The device for preparing 2,6-naphthalenedicarboxylic acid also includes: a heat exchanger connected to the tail gas outlet of the oxidation reactor; and / or, a dryer connected to a filter cake outlet of the filter; and / or, A filtrate feed pump is connected to the filtrate outlet of the dryer and the distillation tower.

8. A method for preparing 2,6-naphthalenedicarboxylic acid using the device according to any one of claims 1 to 7, characterized in that: include: The acylnaphthalene, the catalyst and air are subjected to an oxidation reaction in a solvent to obtain an oxidation mixture; The oxidation mixture is mixed with demineralized water and then subjected to crystallization purification to obtain a crystallized mixture; filtering the crystallization mixture to obtain a filter cake and a filtrate; Drying the filter cake to obtain the 2,6-naphthalene dicarboxylic acid; The filtrate is subjected to rectification and separation to obtain the softened water, the solvent and the removed heavy impurities.

9. The method according to claim 8, characterized in that The method of subjecting acyl naphthalene, a catalyst and air to an oxidation reaction in a solvent comprises: The acyl naphthalene, the catalyst and the solvent are mixed in the raw material preparation tank to obtain an oxidation raw material liquid; The oxidation raw material liquid is quantitatively transported, preheated and mixed with air to obtain the oxidation mixture; And / or, the method for preparing 2,6-naphthalenedicarboxylic acid further comprises: The softened water obtained by the distillation separation is recycled into the crystallization tank as a crystallization aid; and / or, The solvent obtained by the distillation separation is recycled as the solvent participating in the oxidation reaction.

10. The method according to claim 8, characterized in that The acylnaphthalene includes at least one of 2-methyl-6-acetylnaphthalene and 2-methyl-6-propionylnaphthalene; and / or, The solvent comprises at least one of glacial acetic acid and propionic acid; and / or, The mass ratio of the solvent to the acyl naphthalene is (12-20):1; and / or, The catalyst is a mixture of cobalt acetate, manganese acetate, manganese oxide, potassium bromide and sodium bromide, wherein the mass ratios of cobalt acetate, manganese acetate, manganese oxide, potassium bromide and sodium bromide in the catalyst are 10-20%, 15-30%, 15-30%, 20-40% and 20-40% respectively; and / or, The mass amount of the catalyst is 0.3-2% of the total mass amount of acyl naphthalene, catalyst and solvent; and / or, The air is compressed air, the gas-liquid ratio of the air to the oxidation raw material liquid is 200-600, and the oxidation raw material liquid is composed of acyl naphthalene, a catalyst, and a solvent; The temperature of the oxidation reaction is 180-250° C., the reaction pressure is 1.5-3.2 MPa, and the residence time of the reaction materials in the reactor is 20-60 min; and / or, The added mass of the demineralized water is 10-30% of the mass of the oxidation mixture; and / or, During the crystallization purification process, the freezing crystallization cooling rate is 3-8°C / h, the final crystallization temperature is 5-10°C, the final crystallization temperature duration is 1-3h, stirring is turned on during the cooling process, the stirring speed is 500-800r / min, and stirring is stopped when the crystallization tank reaches the final crystallization temperature; and / or, The distillation tower is a vacuum distillation tower, the tower top pressure is -100kPa to -20kPa, the reflux ratio is 15-30, the tower top temperature is 50-110°C, and the tower bottom temperature is 150-200°C.

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