Preparation method and preparation system of 2, 6-naphthalic acid

Abstract

The invention provides a preparation method and a preparation system of 2, 6-naphthalic acid, and the preparation method of 2, 6-naphthalic acid comprises the following steps: mixing acyl naphthalene, a solvent, a catalyst and an auxiliary agent to obtain a raw material solution; carrying out continuous multi-stage oxidation reaction on the raw material liquid and an oxidizing agent to obtain a liquid-solid mixture; and purifying and drying the liquid-solid mixture to obtain the 2, 6-naphthalic acid. According to the preparation method of 2, 6-naphthalic acid disclosed by the invention, by designing a reasonable process flow and adopting a graded step-by-step reaction mode, whole-process continuous production is realized, the production efficiency is high, the product purity and yield are ideal, and a design basis and a technical support are provided for subsequent industrial production of 2, 6-NDA.

Description

Technical Field

[0001] The present application relates to the technical field of fine chemicals, and in particular to a preparation method and a preparation system of 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 backplanes, liquid crystal displays, high-performance fibers and electrical insulation packaging processes. Their industrial production directly affects the modernization and technological development of high-end electronic information materials in my country. The above-mentioned high-performance polymer materials are all prepared by polycondensation reaction of 2,6-naphthalene dicarboxylic acid (2,6-NDA) with ethylene glycol, butanediol and aromatic polyols. 2,6-NDA is one of the various isomers of naphthalene dicarboxylic acid. As a synthetic raw material, it is also widely used in the field of fine chemicals. At present, due to the complex production process of 2,6-NDA and the high production cost, the application of PEN, PBN and LCP is limited to a certain extent. It can be seen that developing a reasonable 2,6-NDA synthesis process route 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] At present, the methods for preparing 2,6-NDA include the Henkel process and the 2,6-dimethylnaphthalene (2,6-DMN) oxidation process. However, the Henkel process for preparing 2,6-NDA requires the use of a large amount of expensive and toxic catalysts such as cadmium, which consumes a lot of energy and causes serious pollution; the 2,6-DMN oxidation process for preparing naphthalene dicarboxylic acid has a low yield, a complex process flow, and a high cost, and is gradually no longer used. At present, intermittent reactors are used to prepare 2,6-naphthalene dicarboxylic acid, which has poor heat and mass transfer effects, low production efficiency, high operating costs, and is not easy for industrial production. The existing technical solvents are not recycled, resulting in low efficiency in the use of solvents used in the oxidation reaction, which increases the cost of preparing 2,6-naphthalene dicarboxylic acid. In the current technologies and methods for preparing 2,6-naphthalene dicarboxylic acid, there is a lack of integrated and continuous devices for reaction and purification, and the yield and purity of the obtained 2,6-naphthalene dicarboxylic acid are not high, which is not conducive to engineering amplification and industrial production. Summary of the invention

[0004] In order to solve the problems of intermittent operation, low production efficiency, high preparation cost, low product purity and yield in the existing preparation method of 2,6-naphthalenedicarboxylic acid, one object of the present application is to provide a preparation method of 2,6-naphthalenedicarboxylic acid, by designing a reasonable process flow and adopting a graded and step-by-step reaction mode to achieve continuous production throughout the whole process, with high production efficiency and ideal product purity and yield, thereby providing a design basis and technical support for the subsequent industrial production of 2,6-NDA.

[0005] Another object of the present application is to provide a system for preparing 2,6-naphthalene dicarboxylic acid.

[0006] To achieve the above object, the first aspect of the present application proposes a method for preparing 2,6-naphthalenedicarboxylic acid, comprising:

[0007] Mixing acylnaphthalene, solvent, catalyst and auxiliary agent to obtain raw material liquid;

[0008] The raw material liquid and the oxidant are subjected to continuous multi-stage oxidation reaction to obtain a liquid-solid mixture;

[0009] The liquid-solid mixture is purified and dried to obtain the 2,6-naphthalenedicarboxylic acid.

[0010] In some embodiments, the raw material liquid and the oxidant are subjected to a continuous multi-stage oxidation reaction, including: adding the liquid phase product obtained from the previous stage oxidation reaction as a raw material to the next stage oxidation reaction.

[0011] In some embodiments, the feedstock solution is subjected to a continuous multi-stage oxidation reaction with an oxidant, comprising:

[0012] The gas phase product obtained from the previous stage oxidation reaction is condensed to obtain a condensed liquid and a condensed gas; and the condensed liquid is added as a raw material to the next stage oxidation reaction.

[0013] In some embodiments, the raw material liquid and the oxidant are subjected to a continuous multi-stage oxidation reaction, and further comprises: discharging the condensed gas as tail gas.

[0014] In some embodiments, the oxidant is added to each oxidation reaction in the multi-stage oxidation reaction.

[0015] In some embodiments, the multi-stage oxidation reaction is carried out in a plurality of oxidation reactors connected in series.

[0016] In some embodiments, the oxidation reactor is a tank reactor.

[0017] In some embodiments, the reaction temperature of the multi-stage oxidation reaction increases sequentially.

[0018] In some embodiments, the reaction pressure of the multi-stage oxidation reaction decreases sequentially.

[0019] In some embodiments, the multi-stage oxidation reaction is carried out under stirring conditions.

[0020] In some embodiments, in the multi-stage oxidation reaction, the temperature difference between the reaction temperatures of two adjacent stages of oxidation reactions is 50-80°C.

[0021] In some embodiments, the pressure difference between the reaction pressures of two adjacent oxidation reactions is 0.1-0.8 MPa.

[0022] In some embodiments, the multi-stage oxidation reaction includes a first stage oxidation reaction, a second stage oxidation reaction, and a third stage oxidation reaction performed sequentially.

[0023] In some embodiments, the reaction temperature of the first stage oxidation reaction is 40-100° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 300-500 r / min.

[0024] In some embodiments, in the first stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (50-60):1.

[0025] In some embodiments, the reaction temperature of the second stage oxidation reaction is 100-180° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 500-900 r / min.

[0026] In some embodiments, in the second stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (40-55):1.

[0027] In some embodiments, the reaction temperature of the third stage oxidation reaction is 180-250° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 500-900 r / min.

[0028] In some embodiments, in the second stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (10-40):1.

[0029] In some embodiments, the oxidant includes at least one of air, industrial oxygen, and high-purity oxygen, preferably compressed air.

[0030] In some embodiments, the mass ratio of the acyl naphthalene, the solvent, the catalyst, and the auxiliary agent is (0.04-0.2):1:(0.01-0.03):(0.0005-0.005).

[0031] In some embodiments, the acylnaphthalene includes at least one of 2-methyl-6-propionylnaphthalene, 2-methyl-6-acetylnaphthalene, and 2-methyl-6-butyrylnaphthalene.

[0032] In some embodiments, the catalyst comprises a Co—Mn—Br catalytic system.

[0033] In some embodiments, the catalyst includes at least one of metallic cobalt, cobalt oxide, cobalt nitrate, cobalt acetate, cobalt sulfate, metallic manganese, manganese oxide, manganese nitrate, manganese acetate, manganese sulfate, sodium bromide, and hydrogen bromide.

[0034] In some embodiments, in the catalyst, the atomic ratio of cobalt, manganese and bromine satisfies the following relationship: 0.05≤Co / Mn≤10, 0.05≤Br / (Co+Mn)≤5.

[0035] In some embodiments, the auxiliary agent includes an iron-containing compound, a copper-containing compound, and a zinc-containing compound.

[0036] In some embodiments, in the auxiliary agent, the mass ratio of the iron-containing compound, the copper-containing compound and the zinc-containing compound is (0.01-1.0): (0.001-0.5): (0.001-0.2).

[0037] In some embodiments, the iron-containing compound includes at least one of ferric chloride, ferric bromide, and ferric acetate.

[0038] In some embodiments, the copper-containing compound includes at least one of copper sulfate, copper acetate, copper chloride, and copper bromide.

[0039] In some embodiments, the zinc-containing compound includes at least one of zinc chloride, zinc oxide, and zinc bromide.

[0040] In some embodiments, the solvent includes xylene and an aliphatic monocarboxylic acid.

[0041] In some embodiments, in the solvent, the molar ratio of the xylene to the acylnaphthalene is (5-30):1, and the molar ratio of the aliphatic monocarboxylic acid to the xylene is (5-7):(3-5).

[0042] In some embodiments, the aliphatic monocarboxylic acid includes at least one of formic acid, acetic acid, propionic acid, and butyric acid.

[0043] In some embodiments, the xylene comprises para-xylene.

[0044] In some embodiments, purifying and drying the liquid-solid mixture comprises:

[0045] Centrifuging the liquid-solid mixture to obtain a mother liquor and a crude naphthalene dicarboxylic acid product;

[0046] Using the mother solution for preparing the raw material solution;

[0047] The crude naphthalene dicarboxylic acid product is washed and dried to obtain a 2,6-naphthalene dicarboxylic acid product.

[0048] In some embodiments, the centrifugal separation temperature is 10-30°C, the rotation speed is 5000-8000r / min, the centrifugal force is 12500-14200×g, and the centrifugal time is 30-60min.

[0049] In some embodiments, the washing liquid used for the washing is methanol and water, and the mass ratio of the methanol to water is (6-9): (1-4).

[0050] In some embodiments, the drying temperature is 100-180°C.

[0051] The second aspect of the present application provides a preparation system of 2,6-naphthalene dicarboxylic acid, which is used in the preparation method of 2,6-naphthalene dicarboxylic acid described in the present application, comprising:

[0052] A raw material preparation unit, used for mixing acyl naphthalene, solvent, catalyst and auxiliary agent to obtain the raw material liquid;

[0053] A multi-stage oxidation reaction unit, used for carrying out the multi-stage oxidation reaction with the raw material liquid and the oxidant as raw materials; the multi-stage oxidation reaction unit comprises a plurality of oxidation reactors connected in series, and the oxidation reactor used for the first stage oxidation reaction in the multi-stage oxidation reaction is connected to the raw material preparation unit, and the bottom of each oxidation reactor is connected to the oxidant source;

[0054] A purification and drying unit, the purification and drying unit comprises a centrifugal device and a washing and drying device connected in sequence, the inlet of the centrifugal device is connected to the liquid phase outlet of the oxidation reactor used for the last stage oxidation reaction in the multi-stage oxidation reaction unit.

[0055] In some embodiments, in the multi-stage oxidation reaction unit, the plurality of oxidation reactors are connected in series in such a manner that the liquid phase outlet of the preceding oxidation reactor is connected to the feed inlet of the succeeding oxidation reactor.

[0056] In some embodiments, the top gas phase outlet of each oxidation reactor is connected to a condenser, and the liquid outlet of the condenser is connected to its corresponding oxidation reactor.

[0057] In some embodiments, the oxidation reactor is a tank reactor.

[0058] In some embodiments, the oxidation reactor has a heating jacket, a stirring motor and a stirring paddle, and a plurality of oxidant inlets are arranged at the bottom, and a material inlet and a liquid phase outlet for the reaction materials to enter are arranged in the middle.

[0059] In some embodiments, the oxidant source comprises an air compressor.

[0060] In some embodiments, the centrifugal device is a horizontal centrifuge or a vertical centrifuge.

[0061] In some embodiments, the liquid outlet of the centrifugal device is connected to the raw material preparation unit.

[0062] In some embodiments, the washing and drying device includes a washing tank, a vacuum filter, and a dryer.

[0063] In some embodiments, the raw material preparation unit is a raw material preparation tank having a heating jacket, a stirring motor and a stirring paddle, and the raw material preparation tank is connected to the oxidation reactor of the first-stage oxidation reaction through a feed pump.

[0064] The preparation method of 2,6-naphthalene dicarboxylic acid described in the present application can at least bring the following beneficial effects:

[0065] 1. The catalyst and the additive are used together. The synergistic effect between the catalyst and the additive is high, the amount of catalyst added is small, the additive does not contain strong acid or strong alkali, and is green and environmentally friendly.

[0066] 2. A kettle-type series oxidation reaction system is adopted. The reactor is a kettle reactor, which has low manufacturing cost and is easy to scale up. Multiple kettles are connected in series, and the oxidation reaction is carried out in stages, which improves the mass transfer and heat transfer effects of the materials, improves the oxidation reaction effect, overcomes the defect of uneven material reaction in a single kettle reactor, and is easy to operate continuously.

[0067] 3. The washing is carried out by using a mixture of methanol and deionized water. The operation is simple and it is easy to remove impurities in the product, thereby improving the purity of the 2,6-naphthalene dicarboxylic acid product.

[0068] 4. The use of a composite solvent containing xylene and aliphatic monocarboxylic acid and a graded oxidation reaction, and multi-pot step-by-step oxidation reduce the generation of by-products, facilitate the recovery and reuse of mother liquor and catalyst, and improve product purity and yield.

[0069] 5. The yield of the 2,6-naphthalene dicarboxylic acid product obtained in the present application is 90.2-94.1%, and the purity reaches 97.0-98.6%.

[0070] The system for preparing 2,6-naphthalene dicarboxylic acid described in the present application has at least the beneficial effects of the method for preparing 2,6-naphthalene dicarboxylic acid described in the present application.

[0071] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings.

[0073] in:

[0074] Figure 1 The present invention is a flow chart of a method for preparing 2,6-naphthalene dicarboxylic acid according to an exemplary embodiment of the present invention (i.e., a structural schematic diagram of a system for preparing 2,6-naphthalene dicarboxylic acid).

[0075] Figure 2 This is a schematic diagram of the structure of an oxidation reactor in a preparation system of 2,6-naphthalenedicarboxylic acid according to an exemplary embodiment of the present application.

[0076] Figure 3 This is a schematic structural diagram of a raw material configuration unit in a preparation system of 2,6-naphthalenedicarboxylic acid according to an exemplary embodiment of the present application.

[0077] Reference numerals:

[0078] V1, raw material preparation unit; R1, first stage oxidation reactor; R2, second stage oxidation reactor; R3, third stage oxidation reactor; E1, first condenser; E2, second condenser; E3, third condenser; P1, oxidant source; L1, centrifugal device; G1, washing and drying device;

[0079] 1. Solvent; 2. Catalyst; 3. Acylnaphthalene; 4. Auxiliary agent; 5. Raw material liquid; 6. Gas phase product; 7. Condensate (i.e. liquid phase after condensation); 8. Tail gas; 9. Liquid phase product of the first stage oxidation reaction; 10. Liquid phase product of the second stage oxidation reaction; 11. Oxidant; 12. Liquid-solid mixture; 13. Mother liquor; 14. Crude naphthalene dicarboxylic acid; 15. 2,6-naphthalene dicarboxylic acid product;

[0080] 20. Reactor body; 21. Reaction material inlet; 22. Condensate inlet; 23. First stirring motor; 24. Reaction tail gas outlet; 25. Reactant outlet; 26. Heating jacket; 27. First stirring paddle; 28. Oxidant inlet;

[0081] 30. Raw material preparation tank body; 31-Raw material addition port; 32-Mother liquor inlet; 33-Second stirring motor; 34-Second stirring paddle; 35-Material circulation pump; 36-Reaction raw material outlet. DETAILED DESCRIPTION

[0082] The embodiments of the present application are described in detail below, and 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 be used to explain the present application, but cannot be understood as limiting the present application.

[0083] In this application, the disclosure of numerical ranges includes all values ​​within the entire range and the disclosure of further subdivided ranges, including the endpoints and sub-ranges given in these ranges.

[0084] In this application, the raw materials, equipment, etc. involved, unless otherwise specified, are all raw materials and equipment that can be made through commercial channels or known methods; the methods involved, unless otherwise specified, are all conventional methods.

[0085] The term "and / or", when used in a list of two or more items, means that any of the listed items can be used alone or in combination with any one or more of the listed items. For example, the expression "A and / or B" is intended to mean A or B or A and B, that is, only A, only B, or a combination of A and B.

[0086] <Method for preparing 2,6-naphthalene dicarboxylic acid>

[0087] Figure 1 The present invention is a flow chart of a method for preparing 2,6-naphthalene dicarboxylic acid according to an exemplary embodiment of the present application.

[0088] like Figure 1 As shown, the preparation method of 2,6-naphthalene dicarboxylic acid in the embodiment of the present application comprises the following steps:

[0089] S101, mixing acyl naphthalene 3, solvent 1, catalyst 2, and auxiliary agent 4 to obtain raw material solution 5.

[0090] S102, subjecting the raw material liquid 5 to a continuous multi-stage oxidation reaction with the oxidant 11 to obtain a liquid-solid mixture 12.

[0091] S103, purifying and drying the liquid-solid mixture 12 to obtain the 2,6-naphthalene dicarboxylic acid product 15.

[0092] In some embodiments, the raw material liquid and the oxidant are subjected to a continuous multi-stage oxidation reaction, including: adding the liquid phase product obtained from the previous stage oxidation reaction as a raw material to the next stage oxidation reaction.

[0093] It should be noted that in the embodiments of the present application, the first oxidation reaction and the second oxidation reaction refer to two adjacent oxidation reactions, for example: the first oxidation reaction and the second oxidation reaction, the second oxidation reaction and the third oxidation reaction, and so on.

[0094] Exemplarily, the composition of the liquid phase product mainly includes solvent, catalyst, auxiliary agent, unreacted acyl naphthalene, oxidation product and the like.

[0095] In some embodiments, the feedstock solution is subjected to a continuous multi-stage oxidation reaction with an oxidant, comprising:

[0096] The gas phase product 6 obtained from the previous stage oxidation reaction is condensed to obtain a condensed liquid and a condensed gas; the condensed liquid is added as a raw material to the next stage oxidation reaction.

[0097] Exemplarily, the main components of the gas phase product include acetic acid, water, air, carbon monoxide, carbon dioxide, etc.

[0098] Exemplarily, the condensation temperature is 18-30°C, including but not limited to 20°C, 25°C or 28°C, etc.

[0099] Exemplarily, the composition of the condensed liquid is acetic acid and water.

[0100] Exemplarily, the composition of the condensed gas is air, carbon monoxide and carbon dioxide.

[0101] In some embodiments, the raw material liquid and the oxidant are subjected to a continuous multi-stage oxidation reaction, and further comprises: discharging the condensed gas as tail gas 8.

[0102] In some embodiments, the oxidant is added to each oxidation reaction in the multi-stage oxidation reaction.

[0103] In some embodiments, the multi-stage oxidation reaction is carried out in a plurality of oxidation reactors connected in series, in order to oxidize the acyl naphthalene as completely as possible, improve the oxidation reaction effect, and increase the yield of 2,6-naphthalenedicarboxylic acid.

[0104] In some embodiments, the oxidation reactor is a tank reactor.

[0105] In some embodiments, the reaction temperature of the multi-stage oxidation reaction increases sequentially.

[0106] In some embodiments, the reaction pressure of the multi-stage oxidation reaction decreases sequentially.

[0107] In some embodiments, the multi-stage oxidation reaction is carried out under stirring conditions.

[0108] In some embodiments, in the multi-stage oxidation reaction, the temperature difference between the reaction temperatures of two adjacent stage oxidation reactions is 50-80°C, including but not limited to 55°C, 65°C, 72°C, 75°C or 78°C.

[0109] In some embodiments, the pressure difference between the reaction pressures of two adjacent oxidation reactions is 0.1-0.8 MPa, including but not limited to 0.2 MPa, 0.4 MPa, 0.6 MPa or 0.7 MPa.

[0110] As an optional example, the multi-stage oxidation reaction includes a first stage oxidation reaction, a second stage oxidation reaction and a third stage oxidation reaction (such as Figure 1 shown).

[0111] In some embodiments, the reaction temperature of the first stage oxidation reaction is 40-100° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 300-500 r / min.

[0112] Exemplarily, the reaction temperature of the first stage oxidation reaction includes but is not limited to 50°C, 70°C or 90°C, etc.

[0113] Exemplarily, the reaction pressure of the first stage oxidation reaction includes but is not limited to 1.5 MPa, 2 MPa or 2.5 MPa, etc.

[0114] Exemplarily, the reaction time of the first stage oxidation reaction includes but is not limited to 40 min, 60 min, 75 min or 90 min, etc.

[0115] Exemplarily, the stirring speed of the first stage oxidation reaction includes but is not limited to 350 r / min, 400 r / min or 450 r / min, etc.

[0116] In some embodiments, in the first stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (50-60):1, including but not limited to 52:1, 55:1 or 58:1, etc.

[0117] In some embodiments, the reaction temperature of the second stage oxidation reaction is 100-180° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 500-900 r / min.

[0118] Exemplarily, the reaction temperature of the second stage oxidation reaction includes but is not limited to 120°C, 140°C or 160°C, etc.

[0119] Exemplarily, the reaction pressure of the second stage oxidation reaction includes but is not limited to 1.5 MPa, 2 MPa or 2.5 MPa, etc.

[0120] Exemplarily, the reaction time of the second stage oxidation reaction includes but is not limited to 40 min, 60 min, 75 min or 90 min, etc.

[0121] Exemplarily, the stirring speed of the second stage oxidation reaction includes but is not limited to 550 r / min, 650 r / min or 750 r / min, etc.

[0122] In some embodiments, in the second stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (40-55):1, including but not limited to 42:1, 45:1, 48:1 or 50:1, etc.

[0123] In some embodiments, the reaction temperature of the third stage oxidation reaction is 180-250° C., the pressure is 1.0-3.0 MPa, the reaction time is 30-120 min, and the stirring speed is 500-900 r / min.

[0124] Exemplarily, the reaction temperature of the third stage oxidation reaction includes but is not limited to 190°C, 210°C or 230°C, etc.

[0125] Exemplarily, the reaction pressure of the second stage oxidation reaction includes but is not limited to 1.5 MPa, 2 MPa or 2.5 MPa, etc.

[0126] Exemplarily, the reaction time of the second stage oxidation reaction includes but is not limited to 40 min, 60 min, 75 min or 90 min, etc.

[0127] Exemplarily, the stirring speed of the second stage oxidation reaction includes but is not limited to 550 r / min, 650 r / min or 750 r / min, etc.

[0128] In some embodiments, in the second stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (10-40):1, including but not limited to 15:1, 20:1, 25:1, 30:1 or 35:1, etc.

[0129] In some embodiments, the oxidant includes at least one of air, industrial oxygen, and high-purity oxygen, preferably compressed air.

[0130] In some embodiments, the mass ratio of the acyl naphthalene, the solvent, the catalyst, and the auxiliary agent is (0.04-0.2):1:(0.01-0.03):(0.0005-0.005), including but not limited to 0.1:1:0.01:0.0005, 0.1:1:0.03:0.005 or 0.1:1:0.02:0.0025, etc.

[0131] In some embodiments, the acylnaphthalene includes but is not limited to at least one of 2-methyl-6-propionylnaphthalene, 2-methyl-6-acetylnaphthalene, 2-methyl-6-butyrylnaphthalene, etc., preferably 2-methyl-6-propionylnaphthalene.

[0132] In some embodiments, the catalyst comprises a Co—Mn—Br catalytic system.

[0133] In some embodiments, the catalyst includes but is not limited to at least one of metallic cobalt, cobalt oxide, cobalt nitrate, cobalt acetate, cobalt sulfate, metallic manganese, manganese oxide, manganese nitrate, manganese acetate, manganese sulfate, sodium bromide, hydrogen bromide, and the like.

[0134] In some embodiments, in the catalyst, the atomic ratio of cobalt, manganese and bromine satisfies the following relationship: 0.05≤Co / Mn≤10, 0.05≤Br / (Co+Mn)≤5.

[0135] For example, the atomic ratio of cobalt to manganese (Co / Mn) includes, but is not limited to, 0.5, 2, 5 or 7.5.

[0136] Exemplarily, the atomic ratio of cobalt, manganese and bromine (Br / (Co+Mn)) includes, but is not limited to, 0.5, 1, 2, 3, 4 or 5, etc.

[0137] As a preferred example, 0.1≤Br / (Co+Mn)≤1.

[0138] In some embodiments, the auxiliary agent includes but is not limited to iron-containing compounds, copper-containing compounds, zinc-containing compounds, and the like.

[0139] As an optional example, the auxiliary agent consists of an iron-containing compound, a copper-containing compound and a zinc-containing compound.

[0140] In some embodiments, in the auxiliary agent, the mass ratio of the iron-containing compound, the copper-containing compound and the zinc-containing compound is (0.01-1.0):(0.001-0.5):(0.001-0.2), including but not limited to 0.1:0.25:0.1, 0.5:0.001:0.001, 0.5:0.25:0.2, 0.5:0.25:0.1, 1:0.25:0.1 or 1:0.5:0.1, etc.

[0141] As a preferred example, in the auxiliary agent, the mass ratio of the iron-containing compound, the copper-containing compound and the zinc-containing compound is (0.03-0.3): (0.002-0.05): (0.002-0.03).

[0142] In some embodiments, the concentration of the additive in the solvent is: the concentration of the iron-containing compound is 0.01-1.0wt%, preferably 0.03-0.3wt%; the concentration of the copper-containing compound is 0.001-0.5wt%, preferably 0.002-0.05wt%; the concentration of the zinc-containing compound is 0.001-0.2wt%, preferably 0.002-0.03wt%.

[0143] In some embodiments, the iron-containing compound includes but is not limited to at least one of ferric chloride, ferric bromide, ferric acetate, and the like.

[0144] In some embodiments, the copper-containing compound includes but is not limited to at least one of copper sulfate, copper acetate, copper chloride, copper bromide, and the like.

[0145] In some embodiments, the zinc-containing compound includes but is not limited to at least one of zinc chloride, zinc oxide, zinc bromide, and the like.

[0146] In some embodiments, the solvent includes, but is not limited to, xylene and aliphatic monocarboxylic acid.

[0147] As a preferred example, the solvent consists of xylene and aliphatic monocarboxylic acid.

[0148] In some embodiments, in the solvent, the molar ratio of the xylene to the acylnaphthalene is (5-30):1, and the molar ratio of the aliphatic monocarboxylic acid to the xylene is (5-7):(3-5).

[0149] Exemplarily, the molar ratio of the xylene to the acyl naphthalene includes but is not limited to 10:1, 15:1, 20:1 or 25:1, etc.

[0150] Exemplarily, the molar ratio of the aliphatic monocarboxylic acid to the xylene includes but is not limited to 5:4, 7:4, 6:3, 6:5 or 6:4, etc.

[0151] In some embodiments, the aliphatic monocarboxylic acid includes but is not limited to at least one of formic acid, acetic acid, propionic acid, butyric acid, and the like.

[0152] In some embodiments, the xylene includes at least one of p-xylene, o-xylene, m-xylene, etc., preferably p-xylene.

[0153] In some embodiments, purifying and drying the liquid-solid mixture comprises the following steps:

[0154] (1) centrifuging the liquid-solid mixture to obtain a mother liquor and a crude naphthalene dicarboxylic acid product;

[0155] (2) using the mother solution for preparing the raw material solution;

[0156] (3) washing and drying the crude naphthalene dicarboxylic acid to obtain a 2,6-naphthalene dicarboxylic acid product.

[0157] In some embodiments, the centrifugal separation temperature is 10-30°C, the rotation speed is 5000-8000r / min, the centrifugal force is 12500-14200×g, and the centrifugal time is 30-60min.

[0158] In some embodiments, the washing liquid used for washing is methanol and water, and the mass ratio of methanol to water is (6-9):(1-4), including but not limited to 7:2, 8:3 or 7.5:2.5, etc.

[0159] In some embodiments, the drying temperature is 100-180°C.

[0160] The preparation method of 2,6-naphthalene dicarboxylic acid in the embodiment of the present application can at least bring the following beneficial effects:

[0161] 1. The catalyst and the additive are used together. The synergistic effect between the catalyst and the additive is high, the amount of catalyst added is small, the additive does not contain strong acid or strong alkali, and is green and environmentally friendly.

[0162] 2. A kettle-type series oxidation reaction system is adopted. The reactor is a kettle reactor, which has low manufacturing cost and is easy to scale up. Multiple kettles are connected in series, and the oxidation reaction is carried out in stages, which improves the mass transfer and heat transfer effects of the materials, improves the oxidation reaction effect, overcomes the defect of uneven material reaction in a single kettle reactor, and is easy to operate continuously.

[0163] 3. The washing is carried out by using a mixture of methanol and deionized water. The operation is simple and it is easy to remove impurities in the product, thereby improving the purity of the 2,6-naphthalene dicarboxylic acid product.

[0164] 4. The use of a composite solvent containing xylene and aliphatic monocarboxylic acid and a graded oxidation reaction, and multi-pot step-by-step oxidation reduce the generation of by-products, facilitate the recovery and reuse of mother liquor and catalyst, and improve product purity and yield.

[0165] 5. The yield of the 2,6-naphthalene dicarboxylic acid product obtained in the present application is 90.2-94.1%, and the purity reaches 97.0-98.6%.

[0166] <2,6-Naphthalenedicarboxylic Acid Preparation System>

[0167] The system for preparing 2,6-naphthalene dicarboxylic acid in the embodiment of the present application can be used in the method for preparing 2,6-naphthalene dicarboxylic acid described in the present application.

[0168] Figure 1 The schematic diagram of the structure of a system for preparing 2,6-naphthalene dicarboxylic acid is shown as an exemplary embodiment of the present application.

[0169] like Figure 1 As shown, the preparation system of 2,6-naphthalene dicarboxylic acid in the embodiment of the present application includes a raw material preparation unit 1, a multi-stage oxidation reaction unit and a purification and drying unit. Among them:

[0170] The raw material preparation unit 1 is used to mix acyl naphthalene, solvent, catalyst and auxiliary agent to obtain the raw material liquid.

[0171] The multi-stage oxidation reaction unit is used to carry out the multi-stage oxidation reaction using the raw material liquid and the oxidant as raw materials; the multi-stage oxidation reaction unit includes a plurality of oxidation reactors connected in series, and the oxidation reactor used for the first-stage oxidation reaction in the multi-stage oxidation reaction is connected to the raw material preparation unit, and the bottom of each oxidation reactor is connected to an oxidant source.

[0172] The purification and drying unit comprises a centrifugal device L1 and a washing and drying device G1 which are connected in sequence. The inlet of the centrifugal device L1 is connected to the liquid phase outlet of the oxidation reactor for the last stage oxidation reaction in the multi-stage oxidation reaction unit.

[0173] In some embodiments, in the multi-stage oxidation reaction unit, the plurality of oxidation reactors are connected in series in such a manner that the liquid phase outlet of the preceding oxidation reactor is connected to the feed inlet of the succeeding oxidation reactor.

[0174] In some embodiments, the top gas phase outlet of each oxidation reactor is connected to a condenser, and the liquid outlet of the condenser is connected to its corresponding oxidation reactor.

[0175] As an optional example, in the multi-stage oxidation reaction unit, the number of oxidation reactors is 2-5, preferably 3.

[0176] In some embodiments, the oxidation reactor is a tank reactor.

[0177] In some embodiments, the oxidation reactor has a heating jacket, a stirring motor, a stirring paddle, at least one oxidant inlet, a reaction material inlet for the reaction material to enter, a reactant outlet for the reaction product to be discharged, a reaction exhaust gas outlet for the reaction exhaust gas to be discharged, etc.

[0178] In some embodiments, the multiple oxidant inlets at the bottom of each oxidation reactor are evenly distributed along the bottom of the oxidation reactor.

[0179] In some embodiments, the oxidation reactor is made of titanium.

[0180] In some embodiments, a reaction exhaust gas outlet for discharging reaction exhaust gas is provided at the top of each oxidation reactor.

[0181] As an alternative example, Figure 2As shown, the oxidation reactor comprises a reactor body 20, and a reaction material inlet 21, a reaction material outlet 25 and at least one heating jacket 26 are arranged on the side wall of the reactor body 20, and the reaction material inlet 21 and the reaction material outlet 25 are arranged above the heating jacket 26 and close to the top of the reactor body 20; a condensate inlet 22 and a reaction tail gas outlet 24 are arranged on the top of the reactor body 20, and a first stirring unit is installed on the reactor body 20, and the first stirring unit includes a first stirring motor 23 and a first stirring paddle 27, and the first stirring motor 23 is installed on the top of the reactor body 20, and its output shaft is connected to the first stirring paddle 27, and the first stirring paddle 27 is located inside the reactor body 20; at least one oxidant inlet 28 for adding oxidants such as compressed air is arranged at the bottom of the reactor body 20. At least one heating jacket 26 is also arranged at the bottom of the reactor body 20.

[0182] Exemplarily, the heating jacket 26 is an electric heating jacket.

[0183] Exemplarily, the first stirring paddle 27 is an axial flow stirring paddle.

[0184] Exemplarily, the reaction material inlet 21 and the reaction material outlet 25 are located above the middle of the side wall of the reactor body 20 .

[0185] In some embodiments, the oxidant source comprises an air compressor or a booster.

[0186] In the embodiments of the present application, the main function of the condenser is to condense and cool the gas phase of the reactor, and it is a jacketed condenser having a gas phase inlet, a gas phase outlet, and a liquid phase outlet.

[0187] In some embodiments, the centrifugal device is a horizontal centrifuge or a vertical centrifuge.

[0188] In some embodiments, the liquid outlet of the centrifugal device is connected to the raw material preparation unit. The main function of the centrifugal device is to separate the solid and liquid of the reaction mixture, and it is equipped with a cooling jacket, a centrifugal rotor, a bearing seat, a filter bag and various seals.

[0189] In some embodiments, the washing and drying device comprises a washing tank, a vacuum filter and a dryer. The main function of the washing and drying device is to wash and dry the crude naphthalene dicarboxylic acid.

[0190] In some embodiments, the raw material preparation unit is a raw material preparation tank having a stirring motor and a stirring paddle, etc., and the raw material preparation tank is connected to the oxidation reactor of the first-stage oxidation reaction through a material circulation pump.

[0191] In some embodiments, a pipeline is provided at the bottom of the raw material preparation tank, which is connected to the oxidation reactor of the first-stage oxidation reaction through a material circulation pump.

[0192] As an alternative example, Figure 3 As shown, the raw material preparation unit includes a raw material preparation tank body 30 and a material circulation pump 35. The raw material preparation tank body 30 is provided with a raw material addition port 31, a mother liquor inlet 32 ​​and a circulating material inlet at the top or the upper end of the side wall. The raw material preparation tank body 30 is provided with a second stirring unit. The second stirring unit includes a second stirring motor 33 and a second stirring paddle 34. The second stirring motor 33 is installed on the top of the raw material preparation tank body 30, and its output shaft is connected to the second stirring paddle 34. The second stirring paddle 34 is located inside the raw material preparation tank body 30; a raw material outlet is provided at the bottom of the raw material preparation tank body 30, and the raw material outlet is connected to the material circulation pump 35. The outlet pipeline of the material circulation pump 35 is connected to the inlet of the three-way valve, one outlet of the three-way valve is connected to the circulating material inlet, and the other outlet of the three-way valve is used as a reaction raw material outlet 6 to be connected to the oxidation reactor for the first stage oxidation reaction in the multi-stage oxidation reaction.

[0193] Exemplarily, a raw material addition port 31 is provided at the top of the raw material preparation tank body 30, and the mother liquor inlet 32 ​​and the circulating material inlet are provided at the upper end of the side wall of the raw material preparation tank body 30, the mother liquor inlet 32 ​​is located above the circulating material inlet, and the mother liquor inlet 32 ​​is adjacent to the top of the raw material preparation tank body 30.

[0194] Exemplarily, the raw material preparation tank body 30 is also provided with a heating jacket such as an electric heating jacket.

[0195] In some embodiments, the preparation system of 2,6-naphthalene dicarboxylic acid in each embodiment of the present application further includes auxiliary pipes, stirring, valves and other spare parts.

[0196] As an alternative example, Figure 1 As shown, the preparation system of 2,6-naphthalene dicarboxylic acid in the embodiment of the present application includes a raw material preparation unit V1, a first-stage oxidation reactor R1, a second-stage oxidation reactor R2, a third-stage oxidation reactor R3 and a centrifugal device L1 connected in sequence.

[0197] The raw material preparation unit V1 is as follows Figure 3The raw material preparation unit shown. The material addition port 1 of the raw material preparation unit V1 is used to add solvent 1, catalyst 2, acyl naphthalene 3 and auxiliary agent 4, and the mother liquor inlet 32 ​​of the raw material preparation unit V1 is connected to the liquid outlet of the centrifugal device L1, and is used to recycle the mother liquor 13 obtained by centrifugal separation of the centrifugal device 1. After the solvent 1, catalyst 2, acyl naphthalene 3 and auxiliary agent 4 (including mother liquor 13 when there is mother liquor 13) are stirred and mixed, a part of them is sent to the raw material preparation unit V1 for recycling by the material circulation pump 35 and the three-way valve, and a part of them is sent to the first-stage oxidation reactor R1 through the reaction raw material outlet 36.

[0198] The first stage oxidation reactor R1, the second stage oxidation reactor R2, and the third stage oxidation reactor R3 are all as follows Figure 2 The oxidation reactor is shown.

[0199] The reaction material inlet 22 of the first-stage oxidation reactor R1 is connected to the reaction raw material outlet 36 of the raw material preparation unit V1, so as to add the raw material liquid 5 into the first-stage oxidation reactor R1; the reactant outlet 25 of the first-stage oxidation reactor R1 is connected to the reaction material inlet 22 of the second-stage oxidation reactor R2, so as to send the first-stage oxidation reaction liquid-phase product 9 discharged from the first-stage oxidation reactor R1 into the second-stage oxidation reactor R2; the reactant outlet 25 of the second-stage oxidation reactor R2 is connected to the reaction material inlet 22 of the third-stage oxidation reactor R3, so as to send the second-stage oxidation reaction liquid-phase product 10 discharged from the second-stage oxidation reactor R2 into the third-stage oxidation reactor R3; the reactant outlet 25 of the third-stage oxidation reactor R3 is connected to the feed port of the centrifugal device L1, so as to send the liquid-solid mixture 12 discharged from the third-stage oxidation reactor R3 to the centrifugal device 11 for centrifugal separation.

[0200] The reaction tail gas outlet 25 of the first-stage oxidation reactor R1 that discharges the gaseous product 6 is connected to the first condenser E1, and the liquid outlet of the first condenser E1 is connected to the condensate inlet 22 of the first-stage oxidation reactor R1, so as to reuse the condensate (i.e., the condensed liquid phase) 7 obtained after condensing the gaseous product discharged from the first-stage oxidation reactor R1 in the first-stage oxidation reactor R1; the tail gas 8 discharged from the gas outlet of the first condenser E1 is directly discharged. The reaction tail gas outlet 25 of the second-stage oxidation reactor R2 that discharges the gaseous product 6 is connected to the second condenser E2, and the liquid outlet of the second condenser E2 is connected to the condensate inlet 22 of the second-stage oxidation reactor R2, so as to reuse the condensate (i.e., the condensed liquid phase) 7 obtained after condensing the gaseous product discharged from the second-stage oxidation reactor R2 in the second-stage oxidation reactor R2; the tail gas 8 discharged from the gas outlet of the second condenser E2 is directly discharged. The reaction tail gas outlet 25 of the third-stage oxidation reactor R3 from which the gas phase product 6 is discharged is connected to the third condenser E3, and the liquid outlet of the third condenser E3 is connected to the condensate inlet 22 of the third-stage oxidation reactor R3, so as to recycle the condensate (i.e., the condensed liquid phase) 7 obtained after the gas phase product discharged from the third-stage oxidation reactor R3 is condensed and reused in the third-stage oxidation reactor R3; the tail gas 8 discharged from the gas outlet of the third condenser E3 is directly discharged. The first condenser E1, the second condenser E2, and the third condenser E3 are all jacketed condensers.

[0201] The oxidant inlets 28 of the first-stage oxidation reactor R1, the second-stage oxidation reactor R2, and the third-stage oxidation reactor R3 are all connected to an oxidant source P1, and the oxidant source P1 is an air compressor, and the oxidant is compressed air.

[0202] The centrifugal device L1 is a centrifuge. The solid phase outlet of the centrifugal device L1 for discharging the crude naphthalene dicarboxylic acid product 14 is connected to the washing and drying device G1. The washing and drying device includes a washing tank, a vacuum filter and a dryer, and the crude naphthalene dicarboxylic acid product 14 is washed, filtered and dried to obtain a 2.6-naphthalene dicarboxylic acid product.

[0203] Using the above Figure 1 The method for preparing 2,6-naphthalenedicarboxylic acid by the preparation system of 2,6-naphthalenedicarboxylic acid shown in the figure comprises the following steps:

[0204] (1) Preparation of raw material solution

[0205] The acylnaphthalene, solvent, catalyst and auxiliary agent are added into the raw material preparation tank (ie the raw material preparation unit) through the material adding port 31 in a certain proportion, and the preparation tank is opened for stirring to make the materials evenly mixed.

[0206] (2) First stage oxidation reaction

[0207] The evenly mixed raw material liquid is pumped into the first-stage oxidation reactor R1 through the material circulation pump 5, and the compressed air enters the reactor from the bottom of the first-stage oxidation reactor R1 and flows upstream. Under the action of the reactor's axial flow stirring paddle, the raw material liquid and compressed air undergo a first-stage oxidation reaction in the first-stage oxidation reactor R1.

[0208] (3) Second stage oxidation reaction

[0209] The liquid phase product 9 of the first-stage oxidation reaction in the first-stage oxidation reactor R1 enters the second-stage oxidation reactor R2, and the second-stage oxidation reaction is carried out while being mixed with the compressed air entering the bottom of the second-stage oxidation reactor R2 under the action of the reactor's axial flow stirring paddle.

[0210] (4) Third stage oxidation reaction

[0211] The liquid product 10 of the second-stage oxidation reaction in the second-stage oxidation reactor R2 enters the third-stage oxidation reactor R3, and is mixed with the compressed air entering from the bottom of the third-stage oxidation reactor R3. Under the action of the reactor's axial flow stirring paddle, the third-stage oxidation reaction is carried out while mixing.

[0212] (5) Gas phase condensation at the top of the reactor

[0213] The gaseous products after the reactions in the first-stage oxidation reactor R1, the second-stage oxidation reactor R2 and the third-stage oxidation reactor R3 are separated into gas and liquid in the condensers at the tops of the three reactors respectively. The high-temperature gas is condensed by the condensers, and the condensed liquid re-enters the corresponding reactors for oxidation reaction, and the condensed gas is discharged as exhaust gas.

[0214] (6) Centrifugal separation of reaction mixture

[0215] In the third-stage oxidation reactor R3, the raw material liquid undergoes the third-stage oxidation reaction to obtain an oxidation reaction mixture which is a liquid-solid mixture. The reaction mixture flows into the centrifugal device L1 from the reactor reactant outlet 25, where solid-liquid separation is performed. The liquid mother liquor 13 obtained after separation is recycled and used to prepare the raw material liquid in the raw material preparation tank; the solid phase after centrifugal separation is the crude naphthalene dicarboxylic acid 14, which enters the washing and drying device G1 for washing and drying treatment.

[0216] (7) Washing and drying of crude naphthalene dicarboxylic acid

[0217] The crude naphthalene dicarboxylic acid product is washed and dried in the washing and drying device G1. After the washing and drying process, the crude product is enriched and purified to finally obtain a high-purity 2,6-naphthalene dicarboxylic acid product 15.

[0218] Certain features of the present technology are further illustrated in the following non-limiting examples.

[0219] The following examples all adopt Figure 1 The preparation system of 2,6-naphthalene dicarboxylic acid containing a first-stage oxidation reactor R1, a second-stage oxidation reactor R2, a third-stage oxidation reactor R3, etc. is carried out, wherein the raw material preparation unit V1 is as follows Figure 3 The raw material preparation unit shown, the first stage oxidation reactor R1, the second stage oxidation reactor R2, and the third stage oxidation reactor R3 are all as shown in Figure 2 The oxidation reactor is shown.

[0220] Example 1

[0221] The preparation method of 2,6-naphthalene dicarboxylic acid of this embodiment comprises the following steps:

[0222] (1) Preparation of raw material liquid: Solvent 1, catalyst 2, acyl naphthalene 3, and auxiliary agent 4 are added to the raw material preparation unit V1, and the raw material preparation unit V1 is started to stir so that the materials are evenly mixed to obtain a raw material liquid.

[0223] The mass ratio of acylnaphthalene, solvent, catalyst and auxiliary agent is 0.1:1:0.02:0.001; the solvent is composed of p-xylene and formic acid, and the molar ratio of formic acid to p-xylene is 6:4; the catalyst is composed of metal cobalt, manganese sulfate and sodium bromide, and the atomic ratio of cobalt, manganese and bromine satisfies the following relationship: Co / Mn=5, Br / (Co+Mn)=0.5; the acylnaphthalene is 2-methyl-6-propionylnaphthalene; the auxiliary agent is composed of ferric chloride, cupric chloride and zinc bromide, and the mass ratio of ferric chloride, cupric chloride and zinc bromide is 0.02:0.025:0.01.

[0224] (2) First-stage oxidation reaction: The raw liquid obtained in step (1) is fed into the first-stage oxidation reactor R1 through the material circulation pump 35, and undergoes a first-stage oxidation reaction with the oxidant compressed air 11 in the first-stage oxidation reactor R1. The gaseous product 6 in the first-stage oxidation reactor R1 is condensed by the first condenser E1 to form a condensate 7 and tail gas 8. The condensate 7 re-enters the first-stage oxidation reactor R1, and the tail gas 8 is discharged.

[0225] Among them, the reaction temperature of the first stage oxidation reaction is 70°C, the pressure is 1Mpa, the reaction time is 60min, the stirring speed is 400r / min; the molar ratio of the oxidant (compressed air) to the acylnaphthalene in the raw material liquid is 55:1.

[0226] (3) Second-stage oxidation reaction: The liquid product 9 of the first-stage oxidation reaction in the first-stage oxidation reactor R1 enters the second-stage oxidation reactor R2, where it is mixed with the oxidant compressed air 11 to undergo a second-stage oxidation reaction. The gaseous product 6 in the second-stage oxidation reactor R2 is condensed in the second condenser E2 to form a condensate 7 and tail gas 8. The condensate 7 re-enters the second-stage oxidation reactor R2, and the tail gas 8 is discharged.

[0227] Among them, the reaction temperature of the second stage oxidation reaction is 140°C, the pressure is 1.5Mpa, the reaction time is 60min, the stirring speed is 700r / min; the molar ratio of the oxidant (compressed air) to the acylnaphthalene in the raw material liquid is 50:1.

[0228] (4) Third-stage oxidation reaction: The liquid product 10 of the second-stage oxidation reaction in the second-stage oxidation reactor R2 enters the third-stage oxidation reactor R3, where it is mixed with the oxidant compressed air 11 to undergo a third-stage oxidation reaction. The gaseous product 6 in the third-stage oxidation reactor R3 is condensed in the third condenser E3 to form a condensate 7 and tail gas 8. The condensate 7 re-enters the third-stage oxidation reactor R3, and the tail gas 8 is discharged.

[0229] Among them, the reaction temperature of the third stage oxidation reaction is 220°C, the pressure is 2.3Mpa, the reaction time is 60min, the stirring speed is 700r / min; the molar ratio of the oxidant (compressed air) to the acylnaphthalene in the raw material liquid is 25:1.

[0230] (5) Centrifugal separation of the reaction mixture: The liquid-solid mixture 12 in the third-stage oxidation reactor R3 enters the centrifugal device L1 for solid-liquid separation to obtain a mother liquor 13 and a crude naphthalene dicarboxylic acid product 14. The mother liquor 13 is sent to the raw material preparation unit V1 for recycling.

[0231] The centrifugal separation temperature was 20°C, the rotation speed was 7000 r / min, the centrifugal force was 13200×g, and the centrifugal time was 40 min.

[0232] (6) Washing and drying of crude naphthalene dicarboxylic acid: The crude naphthalene dicarboxylic acid 14 is sent to the washing and drying device G1 for purification. After washing and drying, a 2,6-naphthalene dicarboxylic acid product 15 is finally obtained.

[0233] The washing liquid used for washing is a mixture of methanol and deionized water in a mass ratio of 7.5:2.5; the drying temperature is 140° C. and the drying time is 8 h.

[0234] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 90.6% and the purity was 98.1%.

[0235] Example 2 (Compared with Example 1, the catalyst is different)

[0236] This embodiment is basically the same as Embodiment 1, except that:

[0237] In step (1), the auxiliary agent consists of cobalt acetate, manganese oxide and hydrogen bromide.

[0238] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 91.3% and the purity was 97.9%.

[0239] Example 3 (Compared with Example 1, the atomic ratio of cobalt, manganese and bromine in the catalyst is different)

[0240] This embodiment is basically the same as Embodiment 1, except that:

[0241] In step (1), the atomic ratios of cobalt, manganese and bromine satisfy the following relationship: Co / Mn=10, Br / (Co+Mn)=5.

[0242] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 92.1% and the purity was 98.2%.

[0243] Example 4 (Compared with Example 1, the atomic ratio of cobalt, manganese and bromine in the catalyst is different)

[0244] This embodiment is basically the same as Embodiment 1, except that:

[0245] In step (1), the atomic ratios of cobalt, manganese and bromine satisfy the following relationship: Co / Mn=0.05, Br / (Co+Mn)=0.1.

[0246] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 93.3% and the purity was 97.8%.

[0247] Example 5 (Compared with Example 1, the amount of catalyst and co-catalyst is lower than the lower limit)

[0248] This embodiment is basically the same as Embodiment 1, except that:

[0249] In step (1), the mass ratio of acyl naphthalene, solvent, catalyst and auxiliary agent is 0.04:1:0.01:0.0005.

[0250] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 90.2% and the purity was 97.5%.

[0251] Example 6 (Compared with Example 1, the amount of catalyst and co-catalyst is lower than the upper limit)

[0252] This embodiment is basically the same as Embodiment 1, except that:

[0253] In step (1), the mass ratio of acyl naphthalene, solvent, catalyst and auxiliary agent is 0.2:1:0.03:0.005.

[0254] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 94.0% and the purity was 97.2%.

[0255] Example 7 (Compared with Example 1, the auxiliary agent is different)

[0256] This embodiment is basically the same as Embodiment 1, except that:

[0257] In step (1), the auxiliary agent consists of ferric acetate, cupric acetate and zinc oxide, and the mass ratio of ferric acetate, cupric acetate and zinc oxide is 0.02:0.02:0.02.

[0258] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 93.5% and the purity was 97.7%.

[0259] Example 8 (Compared with Example 1, all reaction temperatures and oxidant dosages are lower limits)

[0260] This embodiment is basically the same as Embodiment 1, except that:

[0261] In step (2), the reaction temperature of the first stage oxidation reaction is 40° C., the pressure is 1 MPa, the reaction time is 60 min, and the stirring speed is 400 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 50:1.

[0262] In step (3), the reaction temperature of the second stage oxidation reaction is 100° C., the pressure is 1.5 MPa, the reaction time is 60 min, and the stirring speed is 700 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 40:1.

[0263] In step (4), the reaction temperature of the third stage oxidation reaction is 180° C., the pressure is 2.3 MPa, the reaction time is 60 min, and the stirring speed is 700 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 10:1.

[0264] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 90.9% and the purity was 98.0%.

[0265] Example 9 (Compared with Example 1, all reaction temperatures and oxidant dosages are upper limits)

[0266] This embodiment is basically the same as Embodiment 1, except that:

[0267] In step (2), the reaction temperature of the first stage oxidation reaction is 100° C., the pressure is 1 MPa, the reaction time is 60 min, and the stirring speed is 400 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 60:1.

[0268] In step (3), the reaction temperature of the second stage oxidation reaction is 180° C., the pressure is 1.3 MPa, the reaction time is 60 min, and the stirring speed is 700 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 55:1.

[0269] In step (4), the reaction temperature of the third stage oxidation reaction is 250° C., the pressure is 1.9 MPa, the reaction time is 60 min, and the stirring speed is 700 r / min; the molar ratio of the oxidant (compressed air) to the acyl naphthalene in the raw material liquid is 40:1.

[0270] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 92.4% and the purity was 97.3%.

[0271] Embodiment 10 (Compared with Embodiment 1, the solvent ratio is different)

[0272] This embodiment is basically the same as Embodiment 1, except that:

[0273] In step (1), the solvent consists of p-xylene and formic acid, and the molar ratio of formic acid to p-xylene is 7:3.

[0274] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 93.1% and the purity was 97.5%.

[0275] Comparative Example 1 (Compared with Example 1, without additives)

[0276] This comparative example is basically the same as Example 1, except that:

[0277] In step (1), the raw material liquid does not contain an auxiliary agent.

[0278] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 87.2% and the purity was 95.4%.

[0279] Comparative Example 2 (Compared with Example 1, the solvent adopts the existing solvent)

[0280] This comparative example is basically the same as Example 1, except that:

[0281] In step (1), the solvent is the existing solvent acetic acid.

[0282] After testing, the yield of 2,6-naphthalene dicarboxylic acid product was 86.8% and the purity was 94.7%.

[0283] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0284] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0285] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing 2,6-naphthalenedicarboxylic acid, characterized in that: include: Mixing acyl naphthalene, solvent, catalyst and auxiliary agent to obtain raw material liquid; The raw material liquid and the oxidant are subjected to continuous multi-stage oxidation reaction to obtain a liquid-solid mixture; The liquid-solid mixture is purified and dried to obtain the 2,6-naphthalenedicarboxylic acid.

2. The preparation method according to claim 1, characterized in that: The raw material liquid and the oxidant are subjected to a continuous multi-stage oxidation reaction, comprising: Adding the liquid product obtained from the first oxidation reaction as a raw material to the second oxidation reaction; and / or, The gaseous product obtained from the previous stage oxidation reaction is condensed to obtain a condensed liquid and a condensed gas; the condensed liquid is added as a raw material to the next stage oxidation reaction; and / or the condensed gas is discharged as exhaust gas.

3. The preparation method according to claim 1, characterized in that: The oxidant is added to each oxidation reaction in the multi-stage oxidation reaction; And / or, the multi-stage oxidation reaction is carried out in a plurality of oxidation reactors connected in series; and / or, the oxidation reactor is a kettle reactor; and / or, the reaction temperature of the multi-stage oxidation reaction is increased sequentially; and / or, the reaction pressure of the multi-stage oxidation reaction is sequentially reduced; And / or, the multi-stage oxidation reaction is carried out under stirring conditions.

4. The preparation method according to claim 3, characterized in that: In the multi-stage oxidation reaction, the temperature difference between the reaction temperatures of two adjacent stages of oxidation reactions is 50-80° C., and / or the pressure difference between the reaction pressures of two adjacent stages of oxidation reactions is 0.1-0.8 MPa; And / or, the multi-stage oxidation reaction includes a first-stage oxidation reaction, a second-stage oxidation reaction and a third-stage oxidation reaction performed sequentially.

5. The preparation method according to claim 4, characterized in that: The reaction temperature of the first stage oxidation reaction is 40-100°C, the pressure is 1.0-3.0Mpa, the reaction time is 30-120min, and the stirring speed is 300-500r / min; and / or, in the first stage oxidation reaction, the molar ratio of the oxidant to the acylnaphthalene is (50-60):1; And / or, the reaction temperature of the second stage oxidation reaction is 100-180°C, the pressure is 1.0-3.0Mpa, the reaction time is 30-120min, and the stirring speed is 500-900r / min; and / or, in the second stage oxidation reaction, the molar ratio of the oxidant to the acylnaphthalene is (40-55):1; And / or, the reaction temperature of the third stage oxidation reaction is 180-250°C, the pressure is 1.0-3.0Mpa, the reaction time is 30-120min, and the stirring speed is 500-900r / min; And / or, in the second stage oxidation reaction, the molar ratio of the oxidant to the acyl naphthalene is (10-40):

1.

6. The preparation method according to claim 1, characterized in that: The acylnaphthalene includes at least one of 2-methyl-6-propionylnaphthalene, 2-methyl-6-acetylnaphthalene, and 2-methyl-6-butyrylnaphthalene; And / or, the catalyst comprises a Co-Mn-Br catalytic system; and / or, the auxiliary agent comprises an iron-containing compound, a copper-containing compound and a zinc-containing compound; And / or, the solvent comprises xylene and an aliphatic monocarboxylic acid.

7. The preparation method according to claim 6, characterized in that: The catalyst comprises at least one of metallic cobalt, cobalt oxide, cobalt nitrate, cobalt acetate, cobalt sulfate, metallic manganese, manganese oxide, manganese nitrate, manganese acetate, manganese sulfate, sodium bromide, and hydrogen bromide; And / or, in the catalyst, the atomic ratio of cobalt, manganese and bromine satisfies the following relationship: 0.05≤Co / Mn≤10, 0.05≤Br / (Co+Mn)≤5; And / or, in the auxiliary agent, the mass ratio of the iron-containing compound, the copper-containing compound and the zinc-containing compound is (0.01-1.0): (0.001-0.5): (0.001-0.2); And / or, the iron-containing compound includes at least one of ferric chloride, ferric bromide, and ferric acetate; And / or, the copper-containing compound includes at least one of copper sulfate, copper acetate, copper chloride and copper bromide; And / or, the zinc-containing compound includes at least one of zinc chloride, zinc oxide, and zinc bromide; and / or, in the solvent, the molar ratio of the xylene to the acylnaphthalene is (5-30):1, and the molar ratio of the aliphatic monocarboxylic acid to the xylene is (5-7):(3-5); And / or, the aliphatic monocarboxylic acid includes at least one of formic acid, acetic acid, propionic acid, and butyric acid; And / or, the xylene includes para-xylene.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the acyl naphthalene, the solvent, the catalyst and the auxiliary agent is (0.04-0.2):1:(0.01-0.03):(0.0005-0.005); and / or, the oxidant comprises at least one of air, industrial oxygen, and high-purity oxygen, preferably compressed air; And / or, purifying and drying the liquid-solid mixture, comprising: Centrifuging the liquid-solid mixture to obtain a mother liquor and a crude naphthalene dicarboxylic acid product; Using the mother solution for preparing the raw material solution; The crude naphthalene dicarboxylic acid product is washed and dried to obtain a 2,6-naphthalene dicarboxylic acid product; Preferably, the centrifugal separation temperature is 10-30°C, the rotation speed is 5000-8000r / min, the centrifugal force is 12500-14200×g, and the centrifugal time is 30-60min; Preferably, the washing liquid used for the washing is methanol and water, and the mass ratio of the methanol to water is (6-9): (1-4); Preferably, the drying temperature is 100-180°C.

9. A system for preparing 2,6-naphthalenedicarboxylic acid, used in the preparation method according to any one of claims 1 to 8, characterized in that: include: A raw material preparation unit, used for mixing acyl naphthalene, solvent, catalyst and auxiliary agent to obtain the raw material liquid; A multi-stage oxidation reaction unit, used for carrying out the multi-stage oxidation reaction with the raw material liquid and the oxidant as raw materials; the multi-stage oxidation reaction unit comprises a plurality of oxidation reactors connected in series, and the oxidation reactor used for the first stage oxidation reaction in the multi-stage oxidation reaction is connected to the raw material preparation unit, and the bottom of each oxidation reactor is connected to the oxidant source; A purification and drying unit, the purification and drying unit comprises a centrifugal device and a washing and drying device connected in sequence, the inlet of the centrifugal device is connected to the liquid phase outlet of the oxidation reactor used for the last stage oxidation reaction in the multi-stage oxidation reaction unit.

10. The preparation system according to claim 9, characterized in that: In the multi-stage oxidation reaction unit, the plurality of oxidation reactors are connected in series in such a manner that the liquid phase outlet of the preceding oxidation reactor is connected to the feed inlet of the succeeding oxidation reactor; And / or, the top gas phase outlet of each oxidation reactor is connected to a condenser, and the liquid outlet of the condenser is connected to its corresponding oxidation reactor; and / or, the oxidation reactor is a kettle reactor; And / or, the oxidation reactor has a heating jacket, a stirring motor and a stirring paddle, and is provided with a plurality of oxidant inlets at the bottom, and a material inlet and a liquid phase outlet for the reaction material to enter in the middle; and / or, the oxidant source comprises an air compressor; and / or, the centrifugal device is a horizontal centrifuge or a vertical centrifuge; And / or, the liquid outlet of the centrifugal device is connected to the raw material preparation unit; And / or, the washing and drying device comprises a washing tank, a vacuum filter and a dryer; And / or, the raw material preparation unit is a raw material preparation tank having a heating jacket, a stirring motor and a stirring paddle, and the raw material preparation tank is connected to the oxidation reactor of the first-stage oxidation reaction via a feed pump.

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