CN112876359A - Preparation method of dimethyl 2, 6-naphthalenedicarboxylate - Google Patents
Preparation method of dimethyl 2, 6-naphthalenedicarboxylate Download PDFInfo
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- CN112876359A CN112876359A CN202110172977.1A CN202110172977A CN112876359A CN 112876359 A CN112876359 A CN 112876359A CN 202110172977 A CN202110172977 A CN 202110172977A CN 112876359 A CN112876359 A CN 112876359A
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- C07C67/00—Preparation of carboxylic acid esters
- C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/45—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by condensation
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- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
- C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
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Abstract
The invention discloses a preparation method of dimethyl 2, 6-naphthalenedicarboxylate. Specifically, the preparation method of the dimethyl 2, 6-naphthalene dicarboxylate disclosed by the invention comprises the following steps of: under the condition of pressurization, carrying out esterification reaction on 2, 6-naphthalenedicarboxylic acid and methanol in the presence of a catalyst, filtering, and obtaining the 2, 6-naphthalenedicarboxylic acid dimethyl ester without further purification; the mass ratio of the methanol to the 2, 6-naphthalene dicarboxylic acid is 3:1-25: 1; the reaction temperature is 100-150 ℃. The preparation method of the invention simplifies the operation, improves the yield of the dimethyl 2, 6-naphthalene dicarboxylate and simultaneously maintains the purity of the dimethyl 2, 6-naphthalene dicarboxylate.
Description
Technical Field
The invention relates to a preparation method of dimethyl 2, 6-naphthalene dicarboxylate.
Background
Dimethyl 2, 6-Naphthalate (NDC) is a key intermediate of high-end special polyester PEN, is mainly used for producing polyethylene 2, 6-naphthalate (PEN) films, and a PEN material is a novel functional polymer resin material with excellent performance, is short for polyethylene naphthalate and is mainly prepared by esterifying 2, 6-naphthalene dicarboxylic acid (2,6-NDA) and then carrying out high-temperature high-vacuum polycondensation. Therefore, the PEN polyester material is widely applied to the fields of fiber textile materials, film materials, packaging materials, engineering plastics and the like. The PEN has huge market potential in China, only beer bottles are taken as an example, PEN or PEN alloy is used as a material to replace glass bottles, and the PEN has high recovery rate and cost which is not higher than that of the existing glass bottles.
Patent application CN110105191A takes beta-methylnaphthalene as raw material, and through Friedel-crafts acylation reaction, the reaction solution is decompressed, rectified and purified to obtain a crude product, then is recrystallized and purified by using a methanol-water mixed solvent to obtain a pure product of 2-methyl-6-acylnaphthalene, and then is catalytically oxidized with Co-Mn-Br to generate 2, 6-naphthalenedicarboxylic acid, which has the defect of complex post-treatment process.
The master paper (research on synthesis of 2-methyl-6-acylnaphthalene, li shuli, university of great graduate) clearly provides that an acylation product can meet the requirement of oxidation reaction after being purified, and provides that the boiling point and physical property difference of 2-methyl-6-acetylnaphthalene and an isomer are very small, complete purification is difficult to realize through vacuum rectification in an industrial process, and the consumption and energy consumption are high, and the purification cost is high.
The patent application US4764638 uses 2-alkyl-6-acylnaphthalene as raw material, uses Co-Mn-Br as catalyst, and produces 2, 6-naphthalene dicarboxylic acid by catalytic oxidation in air, and has the main defects of complex post-reaction treatment process, long reaction period and low yield.
The document (the technical progress of synthesis and purification of 2, 6-naphthalenedicarboxylic acid, pyronin, petrochemical technology and application, 2002,20 (6): 410- & lt416 >) describes in detail the synthesis method and purification method of 2, 6-naphthalenedicarboxylic acid, because 2, 6-naphthalenedicarboxylic acid has poor solubility and low vapor pressure, it is difficult to obtain pure products by conventional purification methods, the purification process is complicated, the cost is high, much material and energy are consumed, and the produced product lacks market competitiveness.
The document (2, 6-naphthalene dicarboxylic acid purification method, zhangchurong, chemistry and adhesion, 2012.) also clearly suggests that 2, 6-naphthalene dicarboxylic acid is difficult to purify by the conventional method due to the characteristics of physical parameters, poor solubility, high melting point, low steam pressure and the like, and simultaneously suggests that 2, 6-naphthalene dicarboxylic acid is difficult to separate, which is the main reason that the direct esterification method is not used for realizing industrialization at present.
The doctor paper (synthesis of 2, 6-naphthalene dicarboxylic acid and preparation of novel polyaramid containing phthalazinone structure, Kippe, university of great connecting theory) clearly indicates that the acylation product purity can not meet the requirement of oxidation reaction, which indicates that the acylation product needs to be separated and purified, and the paper also specifically describes that the synthesized 2, 6-naphthalene dicarboxylic acid needs to be purified by an alkali dissolution-acid precipitation chemical method and a recrystallization method to purify the 2, 6-naphthalene dicarboxylic acid, the process is complex, more materials and energy are consumed, the material loss of the 2, 6-naphthalene dicarboxylic acid is inevitably caused, and the yield is low.
A master paper (study on synthesis of 2, 6-naphthalene dicarboxylic acid by 2-methylnaphthoyl oxidation reaction, liuliang, 2012) clearly suggests that the purity of the raw material required for the oxidation reaction is preferably more than 99%, and at least 98%, so that the acylation product obtained by the experiment needs to be purified to meet the requirement of the oxidation reaction, and because the physical parameters of isomers are close, the acylation product needs to be purified by two purification methods, i.e. rectification under reduced pressure and recrystallization, so that large energy consumption and solvent are consumed, and industrialization is difficult to realize; the oxidation product 2, 6-naphthalene dicarboxylic acid is almost insoluble in all solvents and is difficult to purify by a recrystallization method, and meanwhile, the 2, 6-naphthalene dicarboxylic acid has high melting point and low vapor pressure and is difficult to purify by a rectification method and a sublimation method, so that acid and alkali are used in the conventional chemical purification method, a large amount of material consumption is caused, too many industrial three wastes are generated, and the environmental protection is not facilitated.
78.4g of 2-methyl-6-propionylnaphthalene was synthesized in the literature (discussion on synthesis of 2, 6-naphthalenedicarboxylic acid, Wuhonghui, Shanghai chemical industry, 1999.) in a reaction yield of 94.2% and a purity of 2-methyl-6-propionylnaphthalene of 89.6%, and the acylation product was recrystallized from a 90% methanol aqueous solution to obtain 56.7g of white crystals in a yield of 81.2%.
Comparison of literature yields:
| No. | propionylation reaction yield |
| Yield of crude product | 94.2％ |
| After recrystallization | 81.2％ |
。
Disclosure of Invention
The invention provides a method for preparing dimethyl 2, 6-naphthalene dicarboxylate, aiming at overcoming the defect of complicated operation of the existing method for preparing dimethyl 2, 6-naphthalene dicarboxylate. The preparation method of the invention simplifies the operation, improves the yield of the dimethyl 2, 6-naphthalene dicarboxylate and simultaneously maintains the purity of the dimethyl 2, 6-naphthalene dicarboxylate.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of 2, 6-naphthalenedicarboxylic acid dimethyl ester, which comprises the following steps:
under the condition of pressurization, carrying out esterification reaction on 2, 6-naphthalenedicarboxylic acid and methanol in the presence of a catalyst, filtering, and obtaining the 2, 6-naphthalenedicarboxylic acid dimethyl ester without further purification;
the mass ratio of the methanol to the 2, 6-naphthalene dicarboxylic acid is 3:1-25: 1;
the reaction temperature is 100-150 ℃.
In one embodiment, the dimethyl 2, 6-naphthalenedicarboxylate may have a purity of 99% or more.
In one embodiment, the catalyst may be an inorganic acid and/or an organic acid, and may be one or more of sulfuric acid, trifluoromethanesulfonic acid, and phosphotungstic acid, such as sulfuric acid, and further such as 98% sulfuric acid by mass.
In one embodiment, the mass ratio of the methanol to the 2, 6-naphthalenedicarboxylic acid may be 3:1 to 20:1, such as 3:1, 4:1, 6:1, 10:1 or 20: 1.
In one embodiment, the pressure under the pressurization condition may be a pressure conventional in the art, and may be 0.1 to 3MPa (e.g., 1MPa, 1.5MPa, or 3MPa), preferably 0.5 to 3MPa, and more preferably 1 to 3 MPa.
In one embodiment, the esterification reaction may be carried out at 100 ℃, 120 ℃, 140 ℃ or 150 ℃.
In one embodiment, the progress of the esterification reaction can be monitored by means conventional in the art (e.g., TLC, HPLC, etc.) based on the disappearance of the 2, 6-naphthalenedicarboxylic acid. The esterification reaction time may be 3 to 7 hours, for example 3 hours, 5 hours, 6 hours or 7 hours.
In one embodiment, the method may further comprise cooling the reaction solution before the filtering.
In one embodiment, the 2, 6-naphthalenedicarboxylic acid can be crude 2, 6-naphthalenedicarboxylic acid without purification. The purity of the 2, 6-naphthalenedicarboxylic acid crude product can be 60% or more, preferably 80% or more.
The preparation method of the crude 2, 6-naphthalenedicarboxylic acid can comprise the following steps: 2-methyl-6-acyl naphthalene is used as a raw material, and a crude product of 2, 6-naphthalene dicarboxylic acid containing a byproduct is obtained through oxidation reaction. The by-products may be those conventional in the art for such reactions and may include other isomers formed in the oxidation reaction.
In one embodiment, when the 2, 6-naphthalenedicarboxylic acid is crude 2, 6-naphthalenedicarboxylic acid without purification, the process for preparing the crude 2, 6-naphthalenedicarboxylic acid may comprise the steps of: in a solvent, under the existence of a catalyst and an oxidant, carrying out oxidation reaction on the 2-methyl-6-acyl naphthalene to obtain the crude product of the 2, 6-naphthalene dicarboxylic acid.
In one embodiment, the solvent may be a solvent conventional in the art, and may be an acidic solvent, and may be an organic acid, such as acetic acid, propionic acid, or a mixed solvent of the two.
In a certain scheme, the catalyst can be a conventional catalyst in the field, can also be a Co-Mn-Br system, can also be a cobalt acetate-manganese acetate-potassium bromide system, and can also be a cobalt acetate tetrahydrate-manganese acetate tetrahydrate-potassium bromide system. The mass ratio of the cobalt acetate to the manganese acetate to the potassium bromide can be 1: (1-2): (0.2-0.6), for example 1.9:1.9:0.5, 2:2:0.5, 3:3:0.8 or 2.5:2.5: 0.6.
In one embodiment, the oxidant may be an oxidant conventional in the art, and may be air, such as compressed air. The pressure of the compressed air may be 0.5-3.5MPa, for example 1MPa, 2MPa, 2.5MPa or 3 MPa.
In one embodiment, the mass ratio of the catalyst to the 2-methyl-6-acylnaphthalene can be any mass ratio conventional in the art, and can be from 0.1:1 to 0.7:1, such as 0.32:1, 0.36:1, 0.62:1, or 0.65: 1.
In one embodiment, the mass ratio of the solvent to the 2-methyl-6-acylnaphthalene can be a mass ratio conventional in the art, and can be from 10:1 to 30:1, such as 13:1, 14:1, 23:1, or 25: 1.
In a certain embodiment, the temperature of the oxidation reaction may be a temperature conventional in the art, and may be 150 to 240 ℃, for example, 170 ℃, 180 ℃, 190 ℃ or 220 ℃.
In one embodiment, the progress of the oxidation reaction can be monitored by methods conventional in the art (e.g., TLC, HPLC, etc.) such that the concentration of the 2, 6-naphthalenedicarboxylic acid does not change. The oxidation reaction time may be any time conventional in the art, and may be from 1 to 10 hours, for example, 3 hours, 5 hours, or 7 hours.
In a certain scheme, after the oxidation reaction is finished, the crude 2, 6-naphthalenedicarboxylic acid is obtained without further purification.
In one embodiment, the post-treatment of the oxidation reaction may comprise the steps of: filtering the reaction solution to obtain the crude product of the 2, 6-naphthalenedicarboxylic acid.
In one embodiment, the 2-methyl-6-acylnaphthalene can be a crude 2-methyl-6-acylnaphthalene without purification. The purity of the 2-methyl-6-acyl naphthalene crude product can be more than 60%.
The preparation method of the crude methyl-6-acylnaphthalene product can comprise the following steps: taking 2-methylnaphthalene as a raw material, and obtaining a 2-methyl-6-acylnaphthalene crude product containing a byproduct through Friedel-crafts acylation reaction; the by-products may be those conventional in the art and may comprise other isomers formed by friedel-crafts acylation.
In one embodiment, when the 2-methyl-6-acylnaphthalene is a crude 2-methyl-6-acylnaphthalene, the method for preparing the crude 2-methyl-6-acylnaphthalene may further comprise the following steps: in an organic solvent, under the existence of a catalyst, carrying out Friedel-crafts acylation reaction on 2-methylnaphthalene and an acylating agent to obtain the crude product of the 2-methyl-6-acylnaphthalene.
In one embodiment, the conditions and operation of the friedel-crafts acylation reaction are the same as those conventional in the art for such reactions.
In one embodiment, the organic solvent may be an organic solvent conventional in the art, and may be an aromatic solvent and/or a sulfur-containing solvent. The aromatic solvent may be nitrobenzene. The sulfur-containing solvent may be carbon disulfide.
In one embodiment, the catalyst can be a catalyst conventional in the art, and can be a lewis acid, and can be one or more of aluminum trichloride, ferric trichloride, and zinc chloride, such as aluminum trichloride and/or ferric trichloride.
In one embodiment, the acylating agent may be an acylating agent conventional in the art, and may be acetyl chloride, acetic anhydride, acetic acid, propionyl chloride, propionic anhydride, or propionic acid, such as acetyl chloride, acetic anhydride, propionyl chloride, or acetic acid.
In one embodiment, the 2-methyl-6-acylnaphthalene may be 2-methyl-6-acetylnaphthalene and/or 2-methyl-6-propionylnaphthalene.
In certain embodiments, the molar ratio of the acylating agent to the 2-methylnaphthalene can be a molar ratio conventional in the art, and can be from 1:1 to 3:1, such as 1.1:1, 1.6:1, 2.1:1, or 2.5: 1.
In one embodiment, the molar ratio of the catalyst to the 2-methylnaphthalene may be a molar ratio conventional in the art, and may again be from 1:1 to 4:1, such as 1.2:1, 1.6:1, 2.5:1, or 3.0: 1.
In one embodiment, the mass ratio of the organic solvent to the 2-methylnaphthalene may be a mass ratio conventional in the art, and may be 3:1 to 30:1, such as 6.7:1, 12:1, 15.0:1, or 21.7: 1.
In a certain scheme, the temperature of the friedel-crafts acylation reaction can be the temperature which is conventional in the field, and can also be-10 to 60 ℃, such as-5 ℃,20 ℃ or 50 ℃.
In one embodiment, the Friedel-crafts acylation reaction can be monitored by means conventional in the art (e.g., TLC, GC, etc.) such that the concentration of 2-methylnaphthalene does not change. The time of the Friedel-crafts acylation reaction can be the time which is conventional in the art, and can be 0.5 to 5 hours, such as 0.5 hour, 1 hour, 3 hours or 4 hours.
In a certain scheme, after the Friedel-crafts acylation reaction is finished, the crude product of the 2-methyl-6-acyl naphthalene is obtained without further purification.
In one embodiment, the post-treatment of the friedel-crafts acylation reaction may comprise the steps of: adding solvent for quenching, separating to obtain an organic phase, and removing the organic solvent to obtain the crude product of the 2-methyl-6-acyl naphthalene. The solvent can be a conventional solvent, and can also be a mixed solvent of an alcohol solvent and water, such as an ethanol water solution. The manner of removing the organic solvent may be a conventional manner in the art, such as distillation under reduced pressure.
The invention provides a preparation method of 2, 6-naphthalenedicarboxylic acid dimethyl ester, which comprises the following steps:
(1) carrying out Friedel-crafts acylation reaction on 2-methylnaphthalene and an acylating agent in an organic solvent in the presence of a catalyst to obtain a crude product of the 2-methyl-6-acylnaphthalene;
(2) in a solvent, under the existence of a catalyst and an oxidant, carrying out oxidation reaction on the 2-methyl-6-acyl naphthalene crude product prepared in the step (1) to obtain a 2, 6-naphthalene dicarboxylic acid crude product;
(3) carrying out esterification reaction on the 2, 6-naphthalenedicarboxylic acid crude product prepared in the step (2) and methanol in the presence of a catalyst under a pressurized condition, filtering, and obtaining the dimethyl 2, 6-naphthalenedicarboxylate without further purification;
the mass ratio of the methanol to the 2, 6-naphthalene dicarboxylic acid is 3:1-25: 1;
the reaction temperature is 100-150 ℃.
In one embodiment, in step (1), the conditions and operations of the friedel-crafts acylation reaction are the same as those conventional in the art for such reactions.
In a certain embodiment, in step (1), the organic solvent may be an organic solvent conventional in the art, and may be an aromatic solvent and/or a sulfur-containing solvent. The aromatic solvent may be nitrobenzene. The sulfur-containing solvent may be carbon disulfide.
In one embodiment, in step (1), the catalyst may be a catalyst conventional in the art, and may be a lewis acid, and may be one or more of aluminum trichloride, ferric trichloride, and zinc chloride, such as aluminum trichloride and/or ferric trichloride.
In a certain embodiment, in step (1), the acylating agent may be an acylating agent conventional in the art, and may be acetyl chloride, acetic anhydride, acetic acid, propionyl chloride, propionic anhydride or propionic acid, such as acetyl chloride, acetic anhydride, propionyl chloride or acetic acid.
In one embodiment, in step (1), the 2-methyl-6-acylnaphthalene may be 2-methyl-6-acetylnaphthalene and/or 2-methyl-6-propionylnaphthalene.
In one embodiment, in step (1), the molar ratio of the acylating agent to the 2-methylnaphthalene may be a molar ratio conventional in the art, and may be 1:1 to 3:1, such as 1.1:1, 1.6:1, 2.1:1, or 2.5: 1.
In one embodiment, in step (1), the molar ratio of the catalyst to the 2-methylnaphthalene may be a molar ratio conventional in the art, and may be 1:1 to 4:1, such as 1.2:1, 1.6:1, 2.5:1, or 3.0: 1.
In a certain embodiment, in step (1), the mass ratio of the organic solvent to the 2-methylnaphthalene may be a mass ratio conventional in the art, and may be 3:1 to 30:1, such as 6.7:1, 12:1, 15.0:1, or 21.7: 1.
In a certain embodiment, in the step (1), the temperature of the friedel-crafts acylation reaction may be a temperature conventional in the art, and may be-10 to 60 ℃, for example-5 ℃,20 ℃ or 50 ℃.
In one embodiment, in step (1), the Friedel-crafts acylation reaction can be monitored by means conventional in the art (e.g., TLC, GC, etc.) such that the concentration of 2-methylnaphthalene does not change. The time of the Friedel-crafts acylation reaction can be the time which is conventional in the art, and can be 0.5 to 5 hours, such as 0.5 hour, 1 hour, 3 hours or 4 hours.
In a certain scheme, in the step (1), after the friedel-crafts acylation reaction is finished, the crude product of the 2-methyl-6-acylnaphthalene is obtained without further purification.
In one embodiment, in step (1), the crude 2-methyl-6-acylnaphthalene comprises a byproduct. The by-products may be those conventional in the art and may comprise other isomers formed by friedel-crafts acylation.
In one embodiment, in step (1), the post-treatment of the friedel-crafts acylation reaction may comprise the following steps: adding solvent for quenching, separating to obtain an organic phase, and removing the organic solvent to obtain the crude 2, 6-naphthalenedicarboxylic acid. The solvent can be a conventional solvent, and can also be a mixed solvent of an alcohol solvent and water, such as an ethanol water solution. The manner of removing the organic solvent may be a conventional manner in the art, such as distillation under reduced pressure.
In a certain scheme, in the step (2), the solvent can be a solvent which is conventional in the art, and can also be an acidic solvent, and can also be an organic acid, such as acetic acid, propionic acid or a mixed solvent of the two.
In a certain scheme, in the step (2), the catalyst may be a catalyst conventional in the art, or may be a Co-Mn-Br system, or may be a cobalt acetate-manganese acetate-potassium bromide system, or may be a cobalt acetate tetrahydrate-manganese acetate tetrahydrate-potassium bromide system. The mass ratio of the cobalt acetate to the manganese acetate to the potassium bromide can be 1: (1-2): (0.2-0.6), for example 1.9:1.9:0.5, 2:2:0.5, 3:3:0.8 or 2.5:2.5: 0.6.
In one embodiment, in step (2), the oxidant may be an oxidant conventional in the art, and may be air, such as compressed air. The pressure of the compressed air may be 0.5-3.5MPa, for example 1MPa, 2MPa, 2.5MPa or 3 MPa.
In one embodiment, in step (2), the mass ratio of the catalyst to the crude 2-methyl-6-acylnaphthalene may be a mass ratio conventional in the art, and may be 0.1:1 to 0.7:1, such as 0.26:1, 0.28:1, 0.29:1, 0.39:1, or 0.46: 1.
In one embodiment, in step (2), the mass ratio of the solvent to the crude 2-methyl-6-acylnaphthalene may be a mass ratio conventional in the art, and may be 5:1 to 30:1, or may be 9:1 to 20:1, such as 9.7:1, 10:1, or 20: 1.
In a certain embodiment, in the step (2), the temperature of the oxidation reaction may be a temperature conventional in the art, and may also be 150 to 240 ℃, for example, 170 ℃, 180 ℃, 190 ℃ or 220 ℃.
In one embodiment, in step (2), the progress of the oxidation reaction can be monitored by methods conventional in the art (e.g., TLC, HPLC, etc.) such that the concentration of the 2, 6-naphthalenedicarboxylic acid does not change. The oxidation reaction time may be any time conventional in the art, and may be from 1 to 10 hours, for example, 3 hours, 5 hours, or 7 hours.
In a certain scheme, in the step (2), after the oxidation reaction is finished, the crude 2, 6-naphthalenedicarboxylic acid is obtained without further purification.
In one embodiment, in step (2), the crude 2, 6-naphthalenedicarboxylic acid may contain by-products. The by-products may be those conventional in the art for such reactions and may include other isomers resulting from the oxidation reaction.
In one embodiment, in step (2), the post-treatment of the oxidation reaction may include the following steps: filtering the reaction solution to obtain the crude product of the 2, 6-naphthalenedicarboxylic acid.
In one embodiment, in the step (3), the purity of the dimethyl 2, 6-naphthalenedicarboxylate may be 99% or more.
In one embodiment, in step (3), the catalyst may be an inorganic acid and/or an organic acid, and may further be one or more of sulfuric acid, trifluoromethanesulfonic acid and phosphotungstic acid, such as sulfuric acid, and further such as 98% sulfuric acid by mass.
In one embodiment, in step (3), the mass ratio of the methanol to the crude 2, 6-naphthalenedicarboxylic acid may be 3:1 to 20:1, for example, 3:1, 4:1, 6:1, 10:1 or 20: 1.
In a certain embodiment, in the step (3), the pressure under the pressurization condition may be a pressure conventional in the art, and may be 0.1 to 3MPa (e.g., 1MPa, 1.5MPa or 3MPa), preferably 0.5 to 3MPa, and more preferably 1 to 3 MPa.
In a certain embodiment, in step (3), the temperature of the esterification reaction may be 100 ℃ to 150 ℃, for example, 100 ℃, 120 ℃, 140 ℃ or 150 ℃.
In one embodiment, in step (3), the progress of the esterification reaction can be monitored by means conventional in the art (e.g., TLC, HPLC, etc.) such that the concentration of the 2, 6-naphthalenedicarboxylic acid does not change. The esterification reaction time may be 3 to 7 hours, for example 3 hours, 5 hours, 6 hours or 7 hours.
In a certain embodiment, in the step (3), before the filtering, an operation of cooling the reaction solution may be further included.
The invention discovers that the by-products generated in the Friedel-crafts acylation reaction in the step (1) can participate in the oxidation reaction in the step (2), part of impurities can be dissolved in a solvent (such as acetic acid) to be removed, and in the process of the oxidation reaction, the recrystallization (reaction crystallization process) of the oxidation product is performed once by using the solvent, so that the impurities in the oxidation product can be reduced. In the subsequent esterification reaction step, while the oxidation product and methanol are subjected to esterification reaction, the generated esterification product is subjected to primary recrystallization (reaction crystallization process) by using a reaction solvent methanol, so that the purity of the finally obtained dimethyl 2, 6-naphthalenedicarboxylate can reach 99%.
It has also been found, that, although not described in the literature, the product of the friedel-crafts acylation reaction can be used in the subsequent oxidation without purification, without affecting the oxidation. Moreover, the oxidation reaction does not carry out purification and does not influence the subsequent esterification reaction. The first two steps of the invention are directly used for esterification without purification, and impurities contained in the esterification are removed by utilizing a reaction recrystallization process, so that the purity of the finally prepared 2, 6-naphthalene dicarboxylic acid dimethyl ester can reach 99%.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows: the preparation method of the invention simplifies the operation, improves the yield of the dimethyl 2, 6-naphthalene dicarboxylate and simultaneously maintains the purity of the dimethyl 2, 6-naphthalene dicarboxylate.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the following examples 1-5, the purity of the compounds was determined by HPLC, the parameters being conventional in the art.
Example 1
Weighing raw material 2-methylnaphthalene (12.0g, 0.0845mol) and dissolving in nitrobenzene (48.0g, 0.39mol), controlling the temperature at 0 ℃ to prepare nitrobenzene solution of the raw material, in another reaction flask, the temperature is controlled at 5 ℃, catalyst anhydrous aluminum trichloride (13.5g, 0.1mol) is dissolved in nitrobenzene (96.0g, 0.78mol), after the raw materials are dissolved and clarified, acetyl chloride (7.3g, 0.093mol) is added and stirred for 0.5h at the temperature of 5 ℃ to prepare an acylation reagent, then the acylation reagent is dripped into the solution of the raw materials by a peristaltic pump at a certain flow rate, the temperature is controlled to be 0 ℃ in the dropping process, the reaction is carried out for 1h, the reaction liquid is added into ethanol water solution for quenching, the obtained nitrobenzene phase is subjected to reduced pressure distillation for recycling the solvent nitrobenzene by layering, 14.9g of crude product 2-methyl-6-acetylnaphthalene (containing isomer by-products) is obtained, and the purity of the 2-methyl-6-acetylnaphthalene is 79.0%.
The crude 2-methyl-6-acetylnaphthalene (14.9g) was directly added to acetic acid (300.0g, 5mol) to dissolve and clarify, and the catalysts cobalt acetate tetrahydrate, manganese acetate tetrahydrate, and potassium bromide were added in an amount of 1.9 g: 1.9 g: 0.5g (7.6mmol:7.7mmol:4.2mmol), air initial pressure 2MPa, heating to 180 ℃ for reaction for 5h, stopping reaction, cooling to room temperature, and filtering to obtain crude 2, 6-naphthalenedicarboxylic acid (2,6-NDA) product 15.8g with purity 91%.
15.8g (about 0.073mol) of the crude product 2, 6-naphthalenedicarboxylic acid was added with methanol (158.0g, 4.9mol), 98% concentrated sulfuric acid (1.4g, 0.014mol) as a catalyst was added, nitrogen gas was kept at an initial pressure of 1MPa, the temperature was raised to 120 ℃ to react for 5 hours, and after completion of the reaction, the temperature was lowered and the reaction was filtered to obtain 13.5g of pure dimethyl 2, 6-naphthalenedicarboxylate (2,6-NDC) with a purity of 99.1%.1H NMR(400MHz,CDCl3)δ8.70(d,2H),8.17(m,2H),7.99(m,2H),4.02(s,6H)。
The yield of the 2-methylnaphthalene used as a raw material after three steps of Friedel-crafts acylation reaction, oxidation reaction and esterification reaction is 64.8 percent.
Comparative example 1
Weighing raw material 2-methylnaphthalene (12.0g, 0.0845mol), dissolving in nitrobenzene (48.0g, 0.39mol), controlling the temperature at 0 ℃ to prepare a nitrobenzene solution of the raw material, controlling the temperature at 5 ℃ in another reaction bottle, dissolving catalyst anhydrous aluminum trichloride (13.5g, 0.1mol) in nitrobenzene (96.0g, 0.78mol), adding acetyl chloride (7.3g, 0.093mol) after the catalyst is dissolved and clarified, stirring for 0.5h at 5 ℃ to prepare an acylation reagent, dripping the acylation reagent into the solution of the raw material by a peristaltic pump at a certain flow rate, controlling the temperature at 0 ℃ in the dripping process, reacting for 1h, adding the reaction solution into an ethanol water solution, quenching, layering, carrying out reduced pressure distillation on the obtained nitrobenzene phase to recover solvent nitrobenzene, and obtaining 14.9g of 2-methyl-6-acetylnaphthalene with the purity of 79.0%.
14.9g of the crude 2-methyl-6-acetylnaphthalene was subjected to reduced pressure distillation to give 12.4g of 2-methyl-6-acetylnaphthalene having a purity of 84.0%, with a loss of 1.36g of 2-methyl-6-acetylnaphthalene, and a loss of 11.5% of the target product due to distillation.
12.4g of the 2-methyl-6-acetylnaphthalene having a purity of 84% was recrystallized from 64.0g of n-hexane to obtain 7.70g of 2-methyl-6-acetylnaphthalene having a purity of 99.0% and a loss product of recrystallization of 2.79 g.
The pure product of 2-methyl-6-acetyl naphthalene (7.70g, 0.042mol) is directly added into acetic acid (154.0g, 2.5mol) to be dissolved and clarified, and catalysts of cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide are added: 0.9 g: 0.2g (3.6mmol:3.7mmol:1.7mmol), air initial pressure 2MPa, heating to 180 ℃ for reaction for 5h, stopping reaction, cooling to room temperature, and filtering to obtain 8.5g of crude 2, 6-naphthalenedicarboxylic acid.
This crude 2, 6-naphthalenedicarboxylic acid (8.5g, ca. 0.04mol) was dissolved in 40.0mL of a solution of sodium hydroxide 2mol/L, and after the solution was clarified, it was back-extracted with 20.0mL of ethyl acetate, followed by filtration, and the aqueous phase after filtration was made strongly acidic in 40.0mL of 2mol/L dilute hydrochloric acid, and then filtered to obtain 8.0g of 2, 6-naphthalenedicarboxylic acid having a purity of 99.0%, and 1.0g of the product was lost in the purification step by oxidation reaction.
Adding 8.0g of the pure 2, 6-naphthalenedicarboxylic acid into methanol (80.0g, 2.5mol), adding catalyst concentrated sulfuric acid (0.7g, 0.007mol), maintaining the initial pressure of nitrogen at 1MPa, heating to 120 ℃ for reaction for 5h, cooling after the reaction is finished, and filtering to obtain 8.6g of solid 2, 6-naphthalenedicarboxylic acid dimethyl ester with the purity of 99.0%;
the yield of the 2-methylnaphthalene used as a raw material after three steps of Friedel-crafts acylation reaction, oxidation reaction and esterification reaction is 41.3 percent.
Example 1 and comparative example 1 yield comparison
Example 2
Weighing raw material 2-methylnaphthalene (12.0g, 0.0845mol), dissolving in nitrobenzene (60.0g, 0.49mol), controlling the temperature at 20 ℃ to prepare nitrobenzene solution of the raw material, controlling the temperature at 20 ℃ in another reaction bottle, dissolving catalyst anhydrous aluminum trichloride (18g, 0.135mol) in nitrobenzene (120g, 0.97mol), adding propionyl chloride (12.4g, 0.135mol) after the solution is clarified, stirring for 0.5h at 20 ℃ to prepare acylating reagent, then dropping the acylating reagent into the solution of the raw material by a peristaltic pump at a certain flow rate, controlling the temperature at 20 ℃ in the dropping process, reacting for 0.5h, adding the reaction solution into ethanol water solution for quenching, layering, distilling the obtained nitrobenzene phase under reduced pressure to recover nitrobenzene solvent, obtaining crude product 2-methyl-6-propionylnaphthalene 15.8g, the purity of 88.0%.
The crude 2-methyl-6-propionylnaphthalene (15.8g, about 0.08mol) was dissolved and clarified by adding it directly to acetic acid (316.0g, 5.3mol), and the catalysts cobalt acetate tetrahydrate, manganese acetate tetrahydrate, potassium bromide 2 g: 2 g: 0.5g (8 mmol: 8.2 mmol:4.2mmol), air initial pressure 2.5MPa, heating to 190 ℃ for reaction for 3h, stopping reaction, cooling to room temperature, and filtering to obtain 16.7g of crude product 2, 6-naphthalene dicarboxylic acid.
Adding methanol (334g, 10.4mol) into the crude product 2, 6-naphthalenedicarboxylic acid (16.7g, about 0.077mol), adding concentrated sulfuric acid (0.1g, 0.001mol) with 98% of catalyst, maintaining the initial pressure of 1.5MPa by nitrogen, heating to 140 ℃ for reaction for 3h, cooling after the reaction is finished, and filtering to obtain solid 2, 6-naphthalenedicarboxylic acid dimethyl ester 15.2g with the purity of 99.0%. The nuclear magnetic properties of dimethyl 2, 6-naphthalenedicarboxylate were substantially the same as those in example 1.
The yield of the product is 73.0% by taking 2-methylnaphthalene as a raw material and carrying out three steps of Friedel-crafts acylation reaction, oxidation reaction and esterification reaction.
Comparative example 2
The comparative example takes 2-methylnaphthalene (12.0g, 0.0845mol) as a raw material, nitrobenzene (180g, 1.46mol) as a reaction solvent, an acylation reagent is propionyl chloride (12.4g, 0.135mol), aluminum trichloride (18g, 0.135mol) is adopted as a catalyst, the reaction temperature is 20 ℃, the reaction is carried out according to the method of the comparative example 1, the reaction time is 0.5h, the reaction is finished, the solvent is recovered by distillation, 15.8g of crude product 2-methyl-6-propionyl naphthalene with the purity of 88 percent and the yield of 85.5 percent is obtained, the crude product is subjected to two purification operations of reduced pressure distillation and recrystallization to obtain 10.5g of 2-methyl-6-propionyl naphthalene with the purity of 99 percent, and the yield of the purified 2-methyl-6-propionyl naphthalene is 62.8 percent;
pure 2-methyl-6-propionyl naphthalene (10.5g, 0.054mol) is used as a raw material, acetic acid (316.0g, 5.3mol) is used as an oxidation reaction solvent, and cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide serving as catalysts are 1 g: 1 g: 0.5g (4 mmol: 4.1 mmol:4.2mmol), 2.5MPa, 190 ℃ for 3h to obtain 11.2g of crude 2, 6-naphthalenedicarboxylic acid;
taking a crude product 2, 6-naphthalenedicarboxylic acid (11.2g, 0.052mol) as a raw material, adding methanol (224g, 7.17mol), catalyzing with concentrated sulfuric acid (0.5g, 0.005mol), reacting at 140 ℃ and under the pressure of 1.5MPa for 3h, and filtering after the reaction is finished to obtain a pure product 2, 6-naphthalenedicarboxylic acid dimethyl ester with the purity of 99%, wherein the total yield of the three steps is 58.7%.
Example 3
In the embodiment, 2-methylnaphthalene (12.0g, 0.0845mol) is used as a raw material, nitrobenzene (260g, 2.1mol) is used as a reaction solvent, an acylation reagent is acetic anhydride (21.5g, 0.21mol), aluminum trichloride (33.8g, 0.25mol) is used as a catalyst, the reaction temperature is-5 ℃, the reaction time is 3 hours, Friedel-crafts acylation reaction is carried out according to the method in the embodiment 1, 14.7g of crude product 2-methyl-6-acetylnaphthalene is obtained after the solvent is distilled and recovered after the reaction, the purity is 75.5%, and the yield is 71.6%;
the acylation crude product 2-methyl-6-acetylnaphthalene (14.7g, about 0.08mol) is used as a raw material for oxidation reaction, propionic acid (147g, 2mol) is used as a solvent, and cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide as catalysts are 3 g: 3 g: 0.8g (12 mmol: 12.2 mmol: 6.7mmol), the reaction temperature is 220 ℃, air is taken as an oxidation source, the pressure is 1MPa, the reaction is complete after 7 hours of reaction time, and 16g of crude product 2, 6-naphthalene dicarboxylic acid is obtained by filtration.
The crude product 2, 6-naphthalene dicarboxylic acid (16g, about 0.074mol) is used as raw material for esterification, methanol (64g, 2.0mol) is used as solvent, 98% concentrated sulfuric acid (0.6g, 0.006mol) is used as catalyst, the reaction time is 6h at the pressure of 3MPa and the temperature of 150 ℃, after the reaction is finished, the pure product 2, 6-naphthalene dicarboxylic acid dimethyl ester with the purity of 99% can be obtained by filtering, and the total yield of the three steps is 58.1%. The nuclear magnetic properties of dimethyl 2, 6-naphthalenedicarboxylate were substantially the same as those in example 1.
Comparative example 3
The comparative example uses 2-methylnaphthalene (12.0g, 0.0845mol) as raw material, nitrobenzene (260g, 2.1mol) as reaction solvent, acetic anhydride (21.5g, 0.21mol) as acylation reagent, aluminum trichloride (33.8g, 0.25mol) as catalyst, the reaction temperature is-5 ℃, the reaction is carried out according to the method of comparative example 1, the reaction time is 3h, the reaction is finished, the solvent is recovered by distillation, 14.7g of crude product 2-methyl-6-acetylnaphthalene is obtained, the purity is 75.5%, and the yield is 71.6%;
the crude product is subjected to two purification operations of reduced pressure rectification and recrystallization to obtain 7.1g of 2-methyl-6-acetylnaphthalene with the purity of 99 percent, and the yield of the purified 2-methyl-6-acetylnaphthalene is 45 percent;
pure 2-methyl-6-acetyl naphthalene (7.1g, 0.039mol) is used as a raw material, propionic acid (147g, 2mol) is used as an oxidation reaction solvent, and cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide serving as catalysts are 1 g: 1 g: 0.2g (4 mmol: 4.1 mmol:1.7mmol), reacting for 7h at 220 ℃ and 1MPa to obtain a crude product of 2, 6-naphthalenedicarboxylic acid, and purifying by alkali dissolution-acid precipitation to obtain 7.3g of pure 2, 6-naphthalenedicarboxylic acid;
the pure product 2, 6-naphthalene dicarboxylic acid (7.3g, 0.034mol) is used as a raw material, methanol (29.4g, 0.92mol) is used as a solvent, a catalyst concentrated sulfuric acid (0.6g, 0.006mol) is used at the temperature of 150 ℃ under the pressure of 3MPa for 6h, after the reaction is finished, the pure product 2, 6-naphthalene dicarboxylic acid dimethyl ester with the purity of 99% can be obtained by filtering, and the total yield of the three steps is 36.8%.
Example 4
In the embodiment, 2-methylnaphthalene (12.0g, 0.0845mol) is used as a raw material, nitrobenzene (80g, 0.65mol) is used as a reaction solvent, an acylation reagent is acetic acid (10.6,0.18mol), ferric chloride (34g, 0.21mol) is used as a catalyst, the reaction temperature is 50 ℃, the reaction time is 4 hours, Friedel-crafts acylation reaction is carried out according to the method in the embodiment 1, 14.4g of crude product 2-methyl-6-acetylnaphthalene is obtained after the solvent is distilled and recovered after the reaction, the purity is 68%, and the yield is 63%;
the acylation crude product 2-methyl-6-acetylnaphthalene (14.4g, about 0.078mol) is used as a raw material for oxidation reaction, acetic acid (140g, 2.3mol) is used as a solvent, and cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide are used as catalysts, wherein the weight ratio of the cobalt acetate tetrahydrate, the manganese acetate tetrahydrate and the potassium bromide is 2.5 g: 2.5 g: 0.6g (10 mmol: 10.2 mmol: 5mmol), the reaction temperature is 170 ℃, air is taken as an oxidation source, the pressure is 3MPa, the reaction is completed after 7 hours of reaction time, and the crude product, namely 15.4g of 2, 6-naphthalenedicarboxylic acid with the purity of 81 percent is obtained by filtration.
The crude product 2, 6-naphthalene dicarboxylic acid (15.4g, about 0.07mol) is used as raw material for esterification, methanol (96g, 3mol) is used as solvent, concentrated sulfuric acid (1g, 0.01mol) is used as catalyst, the reaction time is 7h under the pressure of 1MPa and the temperature of 100 ℃, after the reaction is finished, 10.6g of pure product 2, 6-naphthalene dicarboxylic acid dimethyl ester with the purity of 99 percent can be obtained by filtering, and the total yield of the three steps is 51 percent. The nuclear magnetic properties of dimethyl 2, 6-naphthalenedicarboxylate were substantially the same as those in example 1.
Comparative example 4
The comparative example uses 2-methylnaphthalene (12.0g, 0.0845mol) as a raw material, nitrobenzene (80g, 0.65mol) as a reaction solvent, an acylation reagent is acetic acid (10.6,0.18mol), ferric chloride (34g, 0.21mol) is adopted as a catalyst, the reaction temperature is 50 ℃, the reaction is carried out according to the method of the comparative example 1, the reaction time is 4h, the reaction is finished, the solvent is recovered by distillation, 14.4g of crude product 2-methyl-6-acetylnaphthalene is obtained, the purity is 68 percent, the yield is 63 percent, the crude product is purified by decompression rectification and recrystallization to obtain 5.6g of 2-methyl-6-acetylnaphthalene with the purity of 99 percent, and the yield of the purified 2-methyl-6-acetylnaphthalene is 35.7 percent;
pure 2-methyl-6-acetyl naphthalene is used as a raw material, acetic acid (140g, 2.3mol) is used as an oxidation reaction solvent, and cobalt acetate tetrahydrate, manganese acetate tetrahydrate and potassium bromide serving as catalysts are 0.5 g: 0.5 g: 0.1g (2 mmol: 2 mmol: 0.084mmol), reacting for 7h at 170 ℃ and 3MPa to obtain a crude product of 2, 6-naphthalenedicarboxylic acid, and purifying by alkali dissolution-acid precipitation to obtain 6.2g of pure 2, 6-naphthalenedicarboxylic acid;
the pure product 2, 6-naphthalene dicarboxylic acid (6.2g, 0.03mol) is used as a raw material, methanol (38.6g, 1.21mol) is used as a solvent, concentrated sulfuric acid (1g, 0.01mol) is used as a catalyst, the reaction time is 7h at the pressure of 1MPa and the temperature of 100 ℃, after the reaction is finished, the pure product 2, 6-naphthalene dicarboxylic acid dimethyl ester with the purity of 99 percent can be obtained by filtering, and the total yield of the three steps is 28.8 percent.
Example 5
Acylation oxidation was carried out as in example 1, with varying amounts of methanol used in the esterification reaction;
15.8g (about 0.073mol) of the crude product 2, 6-naphthalenedicarboxylic acid is added with methanol (47.4g, 1.48mol), 98 percent of concentrated sulfuric acid (1.4g, 0.014mol) as a catalyst is added, nitrogen maintains the initial pressure of 1MPa, the temperature is raised to 120 ℃ for reaction for 5 hours, and after the reaction is finished, the temperature is lowered, and the filtration is carried out, thus obtaining 13.2g of pure product 2, 6-naphthalenedicarboxylic acid dimethyl ester (2,6-NDC), the purity of which is 99.1 percent, and the total yield of which is 63.5 percent. The nuclear magnetic properties of dimethyl 2, 6-naphthalenedicarboxylate were substantially the same as those in example 1.
Comparative example 5
Acylation oxidation was carried out as in example 1, with varying amounts of methanol used in the esterification reaction;
15.8g (about 0.073mol) of the crude product 2, 6-naphthalenedicarboxylic acid is added with methanol (31.6g, 0.99mol), 98 percent of concentrated sulfuric acid (1.4g, 0.014mol) as a catalyst is added, nitrogen maintains the initial pressure of 1MPa, the temperature is raised to 120 ℃ for reaction for 5 hours, and after the reaction is finished, the temperature is lowered, and the filtration is carried out, thus obtaining 12.3g of pure product 2, 6-naphthalenedicarboxylic acid dimethyl ester (2,6-NDC), the purity of which is 92.5 percent, and the total yield of which is 55.2 percent. The purity is significantly reduced, resulting in further purification for subsequent industrial use.
Claims (11)
1. A preparation method of dimethyl 2, 6-naphthalene dicarboxylate is characterized by comprising the following steps:
under the condition of pressurization, carrying out esterification reaction on 2, 6-naphthalenedicarboxylic acid and methanol in the presence of a catalyst, filtering, and obtaining the 2, 6-naphthalenedicarboxylic acid dimethyl ester without further purification;
the mass ratio of the methanol to the 2, 6-naphthalene dicarboxylic acid is 3:1-25: 1;
the reaction temperature is 100-150 ℃.
2. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 1,
the purity of the 2, 6-naphthalene dicarboxylic acid dimethyl ester is 99% or more;
and/or the catalyst is inorganic acid and/or organic acid, and can be one or more of sulfuric acid, trifluoromethanesulfonic acid and phosphotungstic acid;
and/or the mass ratio of the methanol to the 2, 6-naphthalene dicarboxylic acid is 3:1-20: 1;
and/or the pressure under the pressurizing condition is 0.1 to 3MPa, preferably 0.5 to 3MPa, and further preferably 1 to 3 MPa;
and/or the temperature of the esterification reaction is 100 ℃, 120 ℃, 140 ℃ or 150 ℃;
and/or the esterification reaction time is 3-7 h;
and/or before the filtration, the operation of reducing the temperature of the reaction liquid is also included;
and/or the 2, 6-naphthalenedicarboxylic acid is a crude product of the 2, 6-naphthalenedicarboxylic acid which is not purified; the purity of the 2, 6-naphthalenedicarboxylic acid crude product can be 60% or more, preferably 80% or more.
3. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 2, wherein said 2, 6-naphthalenedicarboxylic acid is a crude product of 2, 6-naphthalenedicarboxylic acid without purification, and said crude product of 2, 6-naphthalenedicarboxylic acid is produced by the process comprising the steps of: 2-methyl-6-acyl naphthalene is used as a raw material, and a crude product of 2, 6-naphthalene dicarboxylic acid containing a byproduct is obtained through oxidation reaction.
4. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 3, wherein said crude 2, 6-naphthalenedicarboxylic acid is produced by the steps of: in the presence of catalyst and oxidant, 2-methyl-6-acyl naphthalene is oxidized in solvent to obtain the crude 2, 6-naphthalene dicarboxylic acid product.
5. The process for the production of dimethyl-2, 6-naphthalenedicarboxylate as described in claim 4, wherein said solvent is an acidic solvent;
and/or the catalyst is a Co-Mn-Br system;
and/or, the oxidant is air;
and/or the mass ratio of the catalyst to the 2-methyl-6-acyl naphthalene is 0.1:1-0.7: 1;
and/or the mass ratio of the solvent to the crude product of the 2-methyl-6-acyl naphthalene is 10:1-30: 1;
and/or the temperature of the oxidation reaction is 150-240 ℃;
and/or the time of the oxidation reaction is 1-10 h;
and/or after the oxidation reaction is finished, the crude 2, 6-naphthalenedicarboxylic acid is obtained without further purification;
and/or the post-treatment of the oxidation reaction comprises the following steps: filtering the reaction solution to obtain the crude product of the 2, 6-naphthalenedicarboxylic acid;
and/or the 2-methyl-6-acyl naphthalene is a crude product of the unpurified 2-methyl-6-acyl naphthalene; the purity of the 2-methyl-6-acyl naphthalene crude product can be more than 60%.
6. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 5,
the solvent is organic acid, such as acetic acid, propionic acid or a mixed solvent of the two;
and/or the catalyst is a cobalt acetate-manganese acetate-potassium bromide system, and can also be a cobalt acetate tetrahydrate-manganese acetate tetrahydrate-potassium bromide system; the mass ratio of the cobalt acetate to the manganese acetate to the potassium bromide can be 1: (1-2): (0.2-0.6);
and/or the oxidant is compressed air, and the pressure of the compressed air can be 0.5-3.5 MPa;
and/or the 2-methyl-6-acyl naphthalene is an unpurified crude product of 2-methyl-6-acyl naphthalene, and the preparation method of the crude product of methyl-6-acyl naphthalene comprises the following steps: taking 2-methylnaphthalene as a raw material, and obtaining a 2-methyl-6-acylnaphthalene crude product containing a byproduct through Friedel-crafts acylation reaction.
7. The method of claim 4, wherein the 2-methyl-6-acylnaphthalene is a crude 2-methyl-6-acylnaphthalene which has not been purified, and the process for preparing the crude methyl-6-acylnaphthalene comprises the steps of: in an organic solvent, under the existence of a catalyst, carrying out Friedel-crafts acylation reaction on 2-methylnaphthalene and an acylating agent to obtain the crude product of the 2-methyl-6-acylnaphthalene.
8. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as described in claim 7, wherein said organic solvent is an aromatic solvent and/or a sulfur-containing solvent; the aromatic solvent can be nitrobenzene; the sulfur-containing solvent can be carbon disulfide;
and/or the catalyst is Lewis acid and can be one or more of aluminum trichloride, ferric trichloride and zinc chloride;
and/or, the acylating agent is acetyl chloride, acetic anhydride, acetic acid, propionyl chloride, propionic anhydride or propionic acid;
and/or, the 2-methyl-6-acyl naphthalene is 2-methyl-6-acetyl naphthalene and/or 2-methyl-6-propionyl naphthalene;
and/or, the mol ratio of the acylating reagent to the 2-methylnaphthalene is 1:1-3: 1;
and/or the molar ratio of the catalyst to the 2-methylnaphthalene is 1:1-4: 1;
and/or the mass ratio of the organic solvent to the 2-methylnaphthalene is 3:1-30: 1;
and/or the temperature of the Friedel-crafts acylation reaction is-10 to 60 ℃;
and/or the time of the Friedel-crafts acylation reaction is 0.5-5 h;
and/or after the Friedel-crafts acylation reaction is finished, the 2-methyl-6-acyl naphthalene crude product is obtained without further purification;
and/or the post-treatment of the Friedel-crafts acylation reaction comprises the following steps: adding solvent for quenching, separating to obtain an organic phase, and removing the organic solvent to obtain the crude product of the 2-methyl-6-acyl naphthalene.
9. A preparation method of dimethyl 2, 6-naphthalene dicarboxylate is characterized by comprising the following steps:
(1) carrying out Friedel-crafts acylation reaction on 2-methylnaphthalene and an acylating agent in an organic solvent in the presence of a catalyst to obtain a crude product of the 2-methyl-6-acylnaphthalene;
(2) in a solvent, under the existence of a catalyst and an oxidant, carrying out oxidation reaction on the 2-methyl-6-acyl naphthalene crude product prepared in the step (1) to obtain a 2, 6-naphthalene dicarboxylic acid crude product;
(3) carrying out esterification reaction on the 2, 6-naphthalenedicarboxylic acid crude product prepared in the step (2) and methanol in the presence of a catalyst under a pressurized condition, filtering, and obtaining the dimethyl 2, 6-naphthalenedicarboxylate without further purification;
the mass ratio of the methanol to the crude 2, 6-naphthalenedicarboxylic acid is 3:1-25: 1;
the reaction temperature is 100-150 ℃.
10. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 9,
in the step (1), the organic solvent is an aromatic solvent and/or a sulfur-containing solvent;
and/or, in the step (1), the catalyst is Lewis acid and can be one or more of aluminum trichloride, ferric trichloride and zinc chloride;
and/or, in the step (1), the acylating agent is acetyl chloride, acetic anhydride, acetic acid, propionyl chloride, propionic anhydride or propionic acid;
and/or, in the step (1), the 2-methyl-6-acyl naphthalene is 2-methyl-6-acetyl naphthalene and/or 2-methyl-6-propionyl naphthalene;
and/or, in the step (1), the mol ratio of the acylating agent to the 2-methylnaphthalene is 1:1-3: 1;
and/or, in the step (1), the molar ratio of the catalyst to the 2-methylnaphthalene is 1:1-4: 1;
and/or in the step (1), the mass ratio of the organic solvent to the 2-methylnaphthalene is 3:1-30: 1;
and/or in the step (1), the temperature of the Friedel-crafts acylation reaction is-10 to 60 ℃;
and/or, in the step (1), the time of the Friedel-crafts acylation reaction is 0.5-5 h;
and/or, in the step (1), after the Friedel-crafts acylation reaction is finished, further purification is not needed, and the crude product of the 2-methyl-6-acyl naphthalene is obtained;
and/or, in the step (1), the post-treatment of the Friedel-crafts acylation reaction comprises the following steps: adding solvent for quenching, separating to obtain an organic phase, and removing the organic solvent to obtain the crude 2, 6-naphthalenedicarboxylic acid;
and/or, in the step (2), the solvent is an acidic solvent;
and/or, in the step (2), the catalyst is a Co-Mn-Br system;
and/or, in the step (2), the oxidant is air;
and/or, in the step (2), the mass ratio of the catalyst to the crude 2-methyl-6-acyl naphthalene is 0.1:1-0.7: 1;
and/or in the step (2), the mass ratio of the solvent to the crude product of the 2-methyl-6-acyl naphthalene is 5:1-30: 1;
and/or in the step (2), the temperature of the oxidation reaction is 150-240 ℃;
and/or, in the step (2), the time of the oxidation reaction is 1-10 h;
and/or, in the step (2), after the oxidation reaction is finished, further purification is not needed, and the crude 2, 6-naphthalene dicarboxylic acid is obtained;
and/or, in the step (2), the post-treatment of the oxidation reaction comprises the following steps: filtering the reaction solution to obtain the crude product of the 2, 6-naphthalenedicarboxylic acid;
and/or, in the step (3), the purity of the 2, 6-naphthalene dicarboxylic acid dimethyl ester is 99 percent or more;
and/or, in the step (3), the catalyst is inorganic acid and/or organic acid;
and/or, in the step (3), the mass ratio of the methanol to the crude 2, 6-naphthalenedicarboxylic acid is 3:1-20: 1;
and/or, in the step (3), the pressure under the pressurizing condition is 0.1 to 3MPa, preferably 0.5 to 3MPa, and more preferably 1 to 3 MPa;
and/or, in the step (3), the temperature of the esterification reaction is 100 ℃, 120 ℃, 140 ℃ or 150 ℃;
and/or, in the step (3), the esterification reaction time is 3-7 h;
and/or, in the step (3), before the filtration, the operation of reducing the temperature of the reaction liquid is further included.
11. The process for producing dimethyl-2, 6-naphthalenedicarboxylate as claimed in claim 10, wherein,
in the step (1), when the organic solvent contains an aromatic solvent, the aromatic solvent is nitrobenzene;
and/or, in step (1), when the organic solvent comprises a sulfur-containing solvent, the sulfur-containing solvent is carbon disulfide;
and/or, in the step (2), the solvent is an organic acid, such as acetic acid, propionic acid or a mixed solvent of the two;
and/or, in the step (2), the catalyst is a cobalt acetate-manganese acetate-potassium bromide system, and can also be a cobalt acetate tetrahydrate-manganese acetate tetrahydrate-potassium bromide system; the mass ratio of the cobalt acetate to the manganese acetate to the potassium bromide can be 1: (1-2): (0.2-0.6);
and/or, in the step (2), the oxidant is compressed air, and the pressure of the compressed air can be 0.5-3.5 MPa;
and/or in the step (3), the catalyst is one or more of sulfuric acid, trifluoromethanesulfonic acid and phosphotungstic acid.
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