阅读说明：本技术 2,6-萘二甲酸的合成方法 (Synthesis method of 2,6-naphthalene dicarboxylic acid ) 是由 朱庆才 张海涛 畅延青 于 2019-09-04 设计创作，主要内容包括：本发明2,6-萘二甲酸的合成方法,主要解决2,6-二异丙基萘空气氧化生成的醛衍生物含量较高的问题。本发明通过采用2,6-萘二甲酸的合成方法,包括如下步骤：(1)将催化剂和溶剂加入反应釜中；(2)向所述反应釜中进料2,6-二异丙基萘和含自由氧的气体进行反应；(3)2,6-二异丙基萘进料完成后,继续反应0.5-2h,得物料A1；(4)对物料A1进行固液分离,得固相物料A2；(5)将固相物料A2与溶剂混合,打浆得浆液,在催化剂存在下,通入含自由氧的气体继续反应0.5-2h；步骤(1)和步骤(5)所述催化剂含Co、Mn、Br和K的技术方案,较好的解决了该问题,可用于2,6-萘二甲酸的生产中。(The invention relates to a method for synthesizing 2,6-naphthalene dicarboxylic acid, which mainly solves the problem that the content of aldehyde derivatives generated by air oxidation of 2, 6-diisopropyl naphthalene is high. The invention adopts a synthetic method of 2,6-naphthalene dicarboxylic acid, which comprises the following steps: (1) adding a catalyst and a solvent into a reaction kettle; (2) feeding 2, 6-diisopropyl naphthalene and gas containing free oxygen into the reaction kettle for reaction; (3) after the feeding of the 2, 6-diisopropyl naphthalene is finished, continuously reacting for 0.5-2h to obtain a material A1; (4) carrying out solid-liquid separation on the material A1 to obtain a solid-phase material A2; (5) mixing the solid-phase material A2 with a solvent, pulping to obtain slurry, and introducing gas containing free oxygen in the presence of a catalyst to continuously react for 0.5-2 h; the technical proposal that the catalyst in the step (1) and the step (5) contains Co, Mn, Br and K better solves the problem and can be used for producing 2,6-naphthalene dicarboxylic acid.)

The synthesis process of 2,6-naphthalene dicarboxylic acid includes the following steps:

(1) adding a catalyst and a solvent into a reaction kettle;

(2) feeding 2, 6-diisopropyl naphthalene and gas containing free oxygen into the reaction kettle for reaction;

(3) after the feeding of the 2, 6-diisopropyl naphthalene is finished, continuously reacting for 0.5-2h to obtain a material A1;

(4) carrying out solid-liquid separation on the material A1 to obtain a solid-phase material A2;

(5) mixing the solid-phase material A2 with a solvent, pulping to obtain slurry, and introducing gas containing free oxygen in the presence of a catalyst to continuously react for 0.5-2 h; the catalyst in the step (1) and the step (5) contains Co, Mn, Br and K.

2. The method according to claim 1, wherein the solvent in step (1) and/or step (5) is selected from acetic acid and/or propionic acid.

3. The synthesis method according to claim 1, wherein the molar ratio of Mn to Co in the catalyst in the step (1) and/or the step (5) is independently 0.5 to 2.

4. The synthesis method according to claim 1, wherein in the catalyst in step (1) and/or step (5), the molar ratio of Br to Co + Mn is independently 1-4.

5. The synthesis method according to claim 1, wherein in the catalyst in step (1) and/or step (5), the molar ratio of K to Co + Mn is independently 2 to 5.

6. Synthesis according to claim 1, characterized in that Co is used in the form of cobalt acetate, and/or Mn is used in the form of manganese acetate, and/or K is used in the form of potassium bromide or potassium acetate, and/or Br is used in the form of an alkali metal bromide, preferably potassium bromide.

7. The method of claim 6, wherein the cobalt acetate is Co (OAc)₂·4H₂Calculated as O, manganese acetate Mn (OAc)₂·4H₂O, Br in KBr, K in KBr and CH₃COOK is total, and the mass ratio of the solvent to the catalyst in the step (1) is 4-20; and/or cobalt acetate in Co (OAc)₂·4H₂Calculated as O, manganese acetate Mn (OAc)₂·4H₂O is counted and Br is compoundedMeasured as KBr, K compounds as KBr and CH₃COOK, wherein the mass ratio of the solvent in the step (5) to the 2, 6-diisopropyl naphthalene is 1-10.

8. The synthesis method according to claim 1, wherein the reaction temperature of the step (1) and the step (5) is independently selected from 160-220 ℃; and/or the reaction pressure of the step (1) and the step (5) is independently 2-3 MPa.

9. The synthesis method according to claim 1, wherein the feed rate of the free oxygen-containing gas in the step (1) is 10 to 30 in terms of air in a molar ratio to the feed rate of 2, 6-diisopropylnaphthalene in the step (1); and/or the feeding speed of the free oxygen-containing gas in the step (5), wherein the molar ratio of the free oxygen-containing gas to the feeding speed of the 2, 6-diisopropyl naphthalene in the step (1) is 0.5-8 calculated by air.

10. The synthesis method according to claim 1, wherein the space velocity of the 2, 6-diisopropylnaphthalene fed in the step (2) is 0.001-0.003 min relative to the mass of the solvent in the reaction kettle in the step (1)^-1。

Technical Field

The invention relates to a method for synthesizing 2,6-naphthalene dicarboxylic acid.

Background

2,6-naphthalene dicarboxylic acid (2,6-NDA) and derivatives thereof are important monomers for preparing various polyesters, polyurethane materials, Liquid Crystal Polymers (LCP) and the like, and particularly polyethylene naphthalate (PEN) prepared by polycondensation of 2,6-NDA and ethylene glycol has wide application prospects in films, packaging containers (especially beer bottles) and industrial fibers. Due to the high degree of symmetry in the 2,6-NDA structure. The PEN has the characteristics of a straight-chain polymer, and is a high-performance material with good rigidity, high strength and excellent hot workability. Compared with polyethylene terephthalate (PET), PEN has better heat resistance, barrier property, mechanical property, chemical resistance, ultraviolet resistance and the like. Currently, the industry mainly synthesizes 2,6-NDA by air liquid phase oxidation of dialkyl naphthalene under Co-Mn-Br catalyst, for example, U.S. Pat. No. 5, 5183933 (titled: Process for preparation 2,6-naphthalene-dicarboxylic acid) uses 2, 6-dimethylnaphthalene (2,6-DMN) to prepare 2,6-NDA with 93% yield. In various liquid-phase oxidation methods of 2, 6-dialkylnaphthalene, because the physical properties of 2, 6-dimethylnaphthalene are similar to the physical and chemical properties of 2, 7-dimethylnaphthalene, separation is difficult and operation cost is high; and 2, 6-diisopropyl naphthalene (2,6-DIPN) is easy to separate and purify from raw materials (isomer mixture), and the operation cost is lower. Therefore, the process route for preparing 2,6-NDA by the 2,6-DIPN oxidation method has more development prospect in view of industrial production and economic cost. For example, U.S. Pat. No. 4,4681978 (titled: Process for preparing 2,6-naphthalene-dicarboxylic acid) is oxidized by heating and pressurizing in a batch reactor step by step to obtain an intermediate 6-isopropyl-2-naphthoic acid (NMCA) in the first step, and then reacted under the same conditions to finally obtain 24% 2, 6-NDA. U.S. Pat. No. 4,4709088 (titled: Process for preparing 2,6-naphthalene-dicarboxylic acid) is carried out in a semi-continuous manner by continuously adding raw material 2,6-DIPN into a mixed solution of a catalyst and a solvent at a certain rate for reaction, and deeply oxidizing for 2 hours after the feeding is finished, wherein the yield of 2,6-DNA is 91.7 mol%, but the catalyst dosage is very large. In any event, these patents focus on the yield of 2,6-NDA rather than the by-products produced, and in fact, for 2,6-NDA to be used in the polymerization of PEN, the impurities must be present in a certain amount and in a certain amount to meet the requirements. The crude 2,6-NDCA contains a plurality of impurities, different reaction raw materials and different reaction processes, the types and the contents of the impurities in the crude product are completely different, the main impurities comprise trimellitic acid (TMA), bromo-2, 6-NDA, aldehyde derivatives (2-formyl-6-naphthoic acid), 2-naphthoic acid, colored substances, Co, Mn, Br residues and the like, and if the impurities are not removed, the quality of the polyester is seriously influenced. For example, TMA causes branching in the polymer, affects the linearity thereof, and decreases the mechanical strength of the polymer; bromo-2, 6-NDA lowers the softening point of the polymer; aldehyde derivatives can disrupt the polymer chain, affect polymerization rate and molecular weight, and also darken the color of the polymer, affecting its appearance quality (pyronin et al. 2, 6-naphthalenedicarboxylic acid synthesis and purification technology advances [ J ]. petrochemical technology and applications 2002, 20 (6): 410-. Taking 2,6-NDA produced by taking 2,6-DMN as a raw material as an example, AMOCO has the following requirements on the content of impurities in the oxidized crude product 2, 6-NDA: trimellitic acid <5 wt%, bromo 2,6-naphthalene dicarboxylic acid <3 wt%, aldehyde derivative (2-formyl-6-naphthoic acid) <1 wt%. Because of the difference in raw materials, 2,6-NDA is produced by oxidation of 2,6-DIPN, and the reaction pathway is shown in chemical formula 1 (Junipear et al, 2, 6-diisopropylnaphthalene [ J ] prepared by liquid-phase air oxidation [ J ]. Proc. Chemicals 2007,58(8):1996-2003), and the impurities mainly include aldehyde derivatives, including 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid, and the content of the impurities greatly affects the performance and color of the polymer, similar to p-carboxybenzaldehyde (4-CBA) in Terephthalic Acid (TA) prepared by oxidation of p-xylene (PX), while in the PTA industry, the content of 4-CBA is strictly limited before hydrorefining, and is usually 0.25-0.35 wt%.

Disclosure of Invention

The invention aims to solve the technical problem that the content of aldehyde derivatives in crude 2,6-naphthalene dicarboxylic acid generated by air oxidation of 2, 6-diisopropyl naphthalene in the prior art is high, and provides a method for synthesizing 2,6-naphthalene dicarboxylic acid, which can obviously reduce the content of aldehyde derivatives.

In order to solve the technical problems, the technical scheme of the invention is as follows:

the synthesis process of 2,6-naphthalene dicarboxylic acid includes the following steps:

(1) adding a catalyst and a solvent into a reaction kettle;

(2) feeding 2, 6-diisopropyl naphthalene and gas containing free oxygen into the reaction kettle for reaction;

(3) after the feeding of the 2, 6-diisopropyl naphthalene is finished, continuously reacting for 0.5-2h to obtain a material A1;

(4) carrying out solid-liquid separation on the material A1 to obtain a solid-phase material A2;

(5) mixing the solid-phase material A2 with a solvent, pulping to obtain slurry, and introducing gas containing free oxygen in the presence of a catalyst to continuously react for 0.5-2 h; the catalyst in the step (1) and the step (5) contains Co, Mn, Br and K.

In the above technical solutions, the solvent in step (1) and/or step (5) is preferably independently selected from acetic acid and/or propionic acid, and acetic acid is more preferred from the industrial point of view and cost.

In the above technical solution, in the catalyst in step (1) and/or step (5), the molar ratio of Mn to Co is preferably 0.5 to 2, for example, but not limited to, 0.52, 0.55, 1, 1.12, 1.52, 1.82, and 1.98.

In the above technical solution, in the catalyst in step (1) and/or step (5), the molar ratio of Br to Co + Mn is preferably 1 to 4, for example, but not limited to, 1.5, 2, 2.5, 3, 3.5, and the like.

In the above technical solution, in the catalyst in the step (1) and/or the step (5), the molar ratio of K to Co + Mn is preferably 2 to 5, for example, but not limited to, 2.5, 3, 3.5, 4, 4.5, and the like.

In the above-mentioned technical solutions, Co is preferably used in the form of cobalt acetate, Mn is preferably used in the form of manganese acetate, K is preferably used in the form of potassium bromide or potassium acetate, Br is preferably used in the form of an alkali metal bromide, preferably potassium bromide, and cobalt acetate is conveniently Co (OAc)₂·4H₂Calculated as O, manganese acetate Mn (OAc)₂·4H₂O, Br in KBr, K in KBr and CH₃COOK is in total.

In the above technical solution, the mass ratio of the solvent to the catalyst in the step (1) is preferably 4-20, for example, but not limited to, the mass ratio of the solvent to the catalyst may be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and the like, wherein the mass of the catalyst refers to the mass of elements Co, Mn, Br, and K, but not the mass of the compound.

In the above technical solution, the mass ratio of the solvent in the step (5) to the 2, 6-diisopropylnaphthalene is preferably 1 to 10, for example, but not limited to, the mass ratio of the solvent in the step (5) to the 2, 6-diisopropylnaphthalene may be 2, 3, 4, 5, 6, 7, 8, 9, and the like. The addition amount of the solvent is at least enough to enable the solid-phase material A2 to form slurry better, but the economical efficiency is considered, and in the actual experiment, the addition amount is more preferably 3-5.

In the above technical solution, the feeding speed of 2, 6-diisopropylnaphthalene in step (2) has a great effect on the oxidation effect, and although a high feeding rate can achieve a high yield, the purity of the obtained 2,6-naphthalene dicarboxylic acid is not high, and in order to achieve a high purity for the convenience of subsequent purification treatment, it is preferable that the feeding airspeed of 2, 6-diisopropylnaphthalene in step (2) is 0.001-0.003 min relative to the mass of the solvent in the reaction kettle in step (1)^-1For example, but not limited to, 2, 6-diisopropylnaphthalene feed space velocity of 0.0011min^-1、0.0012min^-1、0.0013min^-1、0.0014min^-1、0.0015min^-1、0.0016min^-1、0.0017min^-1、0.0018min^-1、0.0019min^-1、0.002min^-1、0.0021min^-1、0.0022min^-1、0.0023min^-1、0.0024min^-1、0.0025min^-1、0.0026min^-1、0.0027min^-1、0.0028min^-1、0.0029min^-1And so on.

In the technical scheme, the solid-liquid separation in the step (4) is a method known by persons skilled in the art, such as filtration, centrifugal separation and the like, and under the condition of not washing by an additional solvent, the moisture content of the solid-phase material A2 is 8-30 w%, and the solid-phase material A2 can be used for the operation in the step (5); for example, but not limited to, the moisture content of the solid phase material A2 is 8.5 w%, 9 w%, 9.5 w%, 10 w%, 11 w%, 12 w%, 13 w%, 14 w%, 15 w%, 16 w%, 17 w%, 18 w%, 19 w%, 20 w%, 21 w%, 22 w%, 23 w%, 24 w%, 25 w%, 26 w%, 27 w%, 28 w%, 29 w%, etc. The moisture content of A2 in the embodiment of the invention is controlled to be 10.5 +/-0.5 w%, and the operation error has negligible influence on the subsequent operation.

In the above technical solution, the reaction temperature in step (1) and step (5) is preferably 160-220 ℃, such as but not limited to 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, and the like, and more preferably 180-200 ℃.

In the above technical scheme, the reaction pressure of the step (1) and the step (5) is independently preferably 2-3MPa, such as but not limited to 2.1MPa, 2.2MPa, 2.3MPa, 2.4MPa, 2.5MPa, 2.6MPa, 2.7MPa, 2.8MPa, 2.9MPa and the like. In this case, the pressure is a gauge pressure.

In the above technical solution, the feeding rate of the free oxygen-containing gas in the step (1) is preferably 10 to 30, for example, but not limited to, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, etc. in terms of air, relative to the feeding rate of the 2, 6-diisopropylnaphthalene in the step (1).

In the above technical solution, the feeding rate of the free oxygen-containing gas in the step (5) is 0.5 to 8, for example, but not limited to, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, etc. in terms of air, relative to the feeding rate of the 2, 6-diisopropylnaphthalene in the step (1).

In the above technical solutions, the step (5) may be followed by a step of solid-liquid separation, and/or acetic acid washing of the solid phase, and/or water washing of the solid phase, and preferably comprises a step of drying. The acetic acid wash temperature is preferably greater than 60 ℃ to below the acetic acid boiling point, and/or the water wash temperature is preferably greater than 60 ℃ to below the water boiling point.

The technical key point of the invention is the step (5), and the adoption of the step (5) reduces the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the final product; on the other hand, if step (5) is omitted, the technical effect of the present invention cannot be achieved by merely prolonging the reaction time of step (3).

The invention adopts the following components: mn: br: the catalyst proportion of K ═ 1:1:2:5 (molar ratio) is that acetic acid is used as solvent, the reaction temperature is 200 deg.C, the reaction pressure is 2.75MPa, and 2, 6-diisopropyl naphthalene is compared with solvent acetic acidIs 0.0013min^-1The reaction product is washed and analyzed to obtain the impurity 2-formyl-6-naphthoic acid with the content of only 0.12 wt% and the impurity 2-acetyl-6-naphthoic acid with the content of only 0.08 wt%, so that the difficulty of subsequent separation and purification is greatly reduced, and a better technical effect is achieved.

Detailed Description

[ example 1 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed liquid containing crude 2, 6-naphthalenedicarboxylic acid is subjected to vacuum filtration, after the filtration is finished, the obtained filter cake is added with 5000g acetic acid for pulping, then the mixture is sent into a second reaction kettle, the reaction is carried out for continuous reaction for 1 hour under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa, and the air is introduced at the speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, washing by using 60 ℃ acetic acid and 80 ℃ water respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the reaction product mixed liquor are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 2 ]

415.13gCo (OAc)₂·4H₂O、204.24gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, and thenStarting stirring and heating to 200 ℃, controlling the pressure of a reaction kettle at 2.75MPa, heating 1000g of 2, 6-diisopropylnaphthalene to a molten state, then feeding the mixture into the reaction kettle at a speed of 10g/min (equivalent to 0.047mol/min), simultaneously introducing 80L/min (equivalent to 0.75mol/min) of air for reaction, after the feeding is finished, maintaining the reaction temperature and pressure for continuous reaction for 1h, after the reaction is finished, carrying out vacuum filtration on the reaction product mixed solution containing crude 2, 6-naphthalenedicarboxylic acid, after the filtration is finished, adding 5000g of acetic acid into the obtained filter cake for pulping, then feeding the filter cake into a second reaction kettle, continuing the reaction for 1h under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa and the air is introduced at a speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering the reaction product mixed solution containing the crude 2, 6-naphthalenedicarboxylic acid, and respectively adopting acetic acid washing at 60 ℃ and water washing at 80 ℃, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the washing acetic acid and the washing water are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 3 ]

207.56gCo (OAc)₂·4H₂O、408.48gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed liquid containing crude 2, 6-naphthalenedicarboxylic acid is subjected to vacuum filtration, after the filtration is finished, the obtained filter cake is added with 5000g acetic acid for pulping, then the mixture is sent into a second reaction kettle, the reaction is carried out for continuous reaction for 1 hour under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa, and the air is introduced at the speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering the reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, respectively washing with 60 ℃ acetic acid and 80 ℃ waterWashing, wherein the consumption of washing acetic acid is 1000g, the consumption of washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the washing are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 4 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed liquid containing crude 2, 6-naphthalenedicarboxylic acid is subjected to vacuum filtration, after the filtration is finished, the obtained filter cake is added with 3000g acetic acid for pulping, then the mixture is sent into a second reaction kettle, the reaction is carried out for continuous reaction for 1 hour under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa, and the air is introduced at the speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, washing by using 60 ℃ acetic acid and 80 ℃ water respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the reaction product mixed liquor are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 5 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled to be 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to be molten, then the mixture enters the reaction kettle at the speed of 20g/min (equivalent to 0.094mol/min), and 80L/min (equivalent to 0.75mol/min) is introduced at the same timemol/min), keeping the reaction temperature and pressure for continuous reaction for 1h after the feeding is finished, carrying out vacuum filtration on a reaction product mixed solution containing crude 2, 6-naphthalenedicarboxylic acid after the reaction is finished, adding 5000g of acetic acid into the obtained filter cake for pulping after the filtration is finished, then sending the filter cake into a second reaction kettle, continuously reacting for 1h at the temperature of 200 ℃ and the pressure of the reaction kettle of 2.75MPa and under the condition of introducing air at the speed of 20L/min (equivalent to 0.19mol/min), filtering the reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid after the reaction is finished, and respectively adopting acetic acid washing at 60 ℃ and water washing at 80 ℃, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the washing acetic acid and the washing water are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 6 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、892.5gKBr、245.35gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed liquid containing crude 2, 6-naphthalenedicarboxylic acid is subjected to vacuum filtration, after the filtration is finished, the obtained filter cake is added with 5000g acetic acid for pulping, then the mixture is sent into a second reaction kettle, the reaction is carried out for continuous reaction for 1 hour under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa, and the air is introduced at the speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, washing by using 60 ℃ acetic acid and 80 ℃ water respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the reaction product mixed liquor are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ example 7 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5gKBr、1256.2gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour, after the reaction is finished, the reaction product mixed liquid containing crude 2, 6-naphthalenedicarboxylic acid is subjected to vacuum filtration, after the filtration is finished, the obtained filter cake is added with 5000g acetic acid for pulping, then the mixture is sent into a second reaction kettle, the reaction is carried out for continuous reaction for 1 hour under the conditions that the temperature is 200 ℃, the pressure of the reaction kettle is 2.75MPa, and the air is introduced at the speed of 20L/min (equivalent to 0.19mol/min), after the reaction is finished, filtering reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, washing by using 60 ℃ acetic acid and 80 ℃ water respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the reaction product mixed liquor are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ COMPARATIVE EXAMPLE 1 ]

In contrast to example 1, the amount of potassium bromide was increased, but without step (5), as follows:

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5KBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started, the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters the reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), at the same time, 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 1 hour,after the reaction is finished, filtering reaction product mixed liquor containing crude 2,6-naphthalene dicarboxylic acid, washing by using 60 ℃ acetic acid and 80 ℃ water respectively, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the reaction product mixed liquor are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

[ COMPARATIVE EXAMPLE 2 ]

311.25gCo (OAc)₂·4H₂O、306.25gMn(OAc)₂·4H₂O、297.5gKBr、367.5gCH₃COOK and 7700g acetic acid are mixed and added into a reaction kettle, then stirring is started and the temperature is raised to 200 ℃, the pressure of the reaction kettle is controlled at 2.75MPa, 1000g2, 6-diisopropyl naphthalene is heated to a molten state, then the mixture enters a reaction kettle at the speed of 10g/min (equivalent to 0.047mol/min), and 80L/min (equivalent to 0.75mol/min) of air is introduced for reaction at the same time, after the feeding is finished, the reaction temperature and the pressure are maintained for continuous reaction for 2 hours, after the reaction is finished, the reaction product mixed liquor containing the crude 2,6-naphthalene dicarboxylic acid is filtered, and respectively adopting acetic acid washing at 60 ℃ and water washing at 80 ℃, wherein the dosage of the washing acetic acid is 1000g, the dosage of the washing water is 1000g, and the contents of impurities 2-formyl-6-naphthoic acid and 2-acetyl-6-naphthoic acid in the washing acetic acid and the washing water are analyzed after sampling and drying.

For convenience, the main process conditions and experimental results are listed in table 1.

TABLE 1