Refining method of terephthalaldehyde

Abstract

The invention provides a refining method of terephthalaldehyde, and belongs to the technical field of chemical preparation purification. The refining method of terephthalaldehyde comprises the following steps: adding to-be-refined terephthalaldehyde and a solid decolorizing agent into an organic solvent, and carrying out adsorption decolorization to obtain a decolorized solution; filtering the decolorized solution to obtain filtrate; and dropwise adding water into the filtrate to separate out terephthalaldehyde. According to the method, the organic solvent and the solid decolorizing agent jointly act on the terephthalaldehyde to be refined, and the solution is filtered and crystallized, so that the quality of the terephthalaldehyde is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical raw material purification, in particular to a method for refining terephthalaldehyde. Background Art

[0002] Terephthalaldehyde is widely used in medicine, pesticide, material synthesis field, and is an important chemical raw material. In the synthesis of products such as Ecamsule, high-quality terephthalaldehyde needs to be used. Commercially available terephthalaldehyde has poor color and low purity due to synthesis process, active characteristics, etc., and contains impurities such as terephthalic acid, benzaldehyde, and p-hydroxymethylbenzaldehyde. Commercially available terephthalaldehyde cannot meet the use of downstream products, and terephthalaldehyde needs to be refined and purified before use. Summary of the invention

[0003] The present invention aims to provide a method for refining terephthalaldehyde, aiming to improve the quality of terephthalaldehyde.

[0004] To achieve the above object, the present invention provides a method for refining terephthalaldehyde, which comprises the following steps:

[0005] Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent for adsorption decolorization to obtain a decolorized solution;

[0006] filtering the decolorized solution to obtain a filtrate;

[0007] Water was added dropwise to the filtrate to precipitate terephthalaldehyde.

[0008] Preferably, after the step of adding water dropwise to the filtrate to precipitate terephthalaldehyde, the following steps are included:

[0009] The precipitated terephthalaldehyde is filtered, and the filtered terephthalaldehyde is dried under reduced pressure at 50 to 85° C. to a constant weight to obtain dry terephthalaldehyde.

[0010] Preferably, the step of adding the terephthalaldehyde to be purified and a solid decolorizing agent to an organic solvent for adsorption decolorization to obtain a decolorized solution comprises:

[0011] Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent;

[0012] Under nitrogen protection, the solution is heated to 50-65°C and maintained for 1-2 hours for adsorption decolorization to obtain a decolorized solution.

[0013] Preferably, the step of adding water to the filtrate to precipitate terephthalaldehyde comprises:

[0014] Add water dropwise to the filtrate, and gradually cool the filtrate to 0-10°C and maintain for 3-6 hours to precipitate terephthalaldehyde.

[0015] Preferably, the step of filtering the decolorized solution to obtain a filtrate comprises:

[0016] The decolorized solution is filtered at a temperature of 45-60° C. to obtain a filtrate.

[0017] Preferably, after the step of filtering the solution to obtain a filtrate, the following steps are included:

[0018] The filtrate is distilled at atmospheric pressure to distill off part of the organic solvent.

[0019] Preferably, the organic solvent is selected from tetrahydrofuran, 1,4-dioxane, and mixtures thereof.

[0020] Preferably, the solid decolorizing agent is selected from at least one of activated carbon, silica gel and diatomaceous earth.

[0021] Preferably, the weight ratio of the terephthalaldehyde to be purified to the organic solvent is 1:4-7.

[0022] Preferably, the weight ratio of the terephthalaldehyde to be purified to the solid decolorizing agent and the water is 1:0.01-0.05:6-10.

[0023] The present invention provides a method for refining terephthalaldehyde, comprising the following steps: adding terephthalaldehyde to be refined and a solid decolorant into an organic solvent, performing adsorption decolorization, and obtaining a decolorized solution; filtering the decolorized solution to obtain a filtrate; and dripping water into the filtrate to precipitate terephthalaldehyde. The present invention allows the organic solvent and the solid decolorant to act on the terephthalaldehyde to be refined, and filters and crystallizes the solution, so that the color of the terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals, and terephthalaldehyde with a purity greater than 98.5% is obtained, thereby improving the quality of the terephthalaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the GC spectrum of terephthalaldehyde of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0026] The present invention provides a method for refining terephthalaldehyde, comprising the following steps:

[0027] Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent for adsorption decolorization to obtain a decolorized solution;

[0028] filtering the decolorized solution to obtain a filtrate;

[0029] Water was added dropwise to the filtrate to precipitate terephthalaldehyde.

[0030] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used in the preparation, and commercially available products known to those skilled in the art can be used.

[0031] The poor quality terephthalaldehyde used in the present invention is not particularly limited and can be terephthalaldehyde prepared by a known method or available on the market.

[0032] In the present invention, the organic solvent may be selected from tetrahydrofuran, 1,4-dioxane, and a mixture thereof.

[0033] In the present invention, the solid decolorizing agent is selected from at least one of activated carbon, silica gel and diatomaceous earth.

[0034] In the present invention, the weight ratio of the terephthalaldehyde to be purified (terephthalaldehyde with poor purity and quality) to the organic solvent is 1:4-7.

[0035] In the present invention, the weight ratio of the terephthalaldehyde to be purified to the solid decolorizing agent and the water is 1:0.01-0.05:6-10.

[0036] Wherein: crude terephthalaldehyde: tetrahydrofuran (or 1,4-dioxane): activated carbon (silica gel or diatomaceous earth): water = 1: 4-7: 0.01-0.05: 6-10 (w / w);

[0037] The dosage of tetrahydrofuran is 4 to 7 times that of terephthalaldehyde, preferably 5 to 6 times. The dosage of activated carbon (diatomaceous earth or silica gel) can be 1% to 5%. According to the color of the crude terephthalaldehyde and the foreign matter situation, select the appropriate dosage.

[0038] In the present invention, after the step of adding water dropwise to the filtrate to precipitate terephthalaldehyde, the following steps are included:

[0039] The precipitated terephthalaldehyde is filtered, and the filtered terephthalaldehyde is dried at 50-80° C. under normal pressure to a constant weight; or is dried in a vacuum oven at 50-70° C. under reduced pressure to a constant weight.

[0040] In the present invention, the step of adding the terephthalaldehyde to be purified and the solid decolorizing agent to the organic solvent for adsorption decolorization to obtain the decolorized solution comprises:

[0041] Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent;

[0042] Under nitrogen protection, the solution is heated to 50-65°C and maintained for 1-2 hours for adsorption decolorization to obtain a decolorized solution. During adsorption decolorization, the optimal solution heating target temperature and heating maintenance temperature are 60-65°C.

[0043] In the present invention, the step of adding water dropwise to the filtrate to precipitate purified terephthalaldehyde comprises:

[0044] Water is added dropwise to the filtrate, and the filtrate is gradually cooled to 0-10°C and maintained for 3-6 hours to precipitate terephthalaldehyde. When terephthalaldehyde crystals are precipitated, the optimal cooling target temperature and cooling maintenance temperature of the filtrate are 0-5°C.

[0045] In the present invention, the step of filtering the decolorized solution to obtain a filtrate comprises:

[0046] The decolorized solution is filtered at a temperature of 45 to 60° C. to obtain a filtrate. When the decolorized solution is filtered at a temperature lower than 45° C., terephthalaldehyde will precipitate and be lost, thus affecting the yield of terephthalaldehyde.

[0047] In the present invention, after the step of filtering the solution to obtain a filtrate, the following steps are included:

[0048] The filtrate is subjected to atmospheric distillation to distill off part of the organic solvent. By subjecting the filtrate to atmospheric distillation, part of the organic solvent can be recovered, which helps to improve the refining yield of terephthalaldehyde and facilitates use in refining terephthalaldehyde.

[0049] In the present invention, firstly, crude terephthalaldehyde is dissolved in tetrahydrofuran or 1,4-dioxane, one or more of activated carbon, silica gel and diatomaceous earth are added, decolorization and adsorption are carried out at high temperature, hot filtration is carried out, the filtrate is distilled at normal pressure, water is added dropwise and then the temperature is lowered to crystallize terephthalaldehyde.

[0050] When the solution is decolorized, the temperature is raised to 50-65°C under nitrogen protection and stirred for 1-2 hours to dissolve and decolorize.

[0051] When filtering the decolorized solution, filter it while it is hot and the filtering temperature should be greater than 45°C.

[0052] The filtrate is distilled at normal pressure until the residual tetrahydrofuran is 1 to 1.5 times, and 6 to 10 times water is slowly added dropwise at 50 to 60°C to disperse the crystals.

[0053] When crystal precipitation is carried out, the temperature is gradually lowered to 0-10°C and kept warm for 3-6 hours. The optimal temperature is 0-5°C. The cooling can be carried out using ordinary refrigerants.

[0054] When the precipitated terephthalaldehyde is dried, the wet product can be dried at 50-80°C under normal pressure to a constant weight, or dried in a vacuum oven at 50-70°C under reduced pressure to a constant weight.

[0055] The technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention.

[0056] Example 1

[0057] Add 20g crude terephthalaldehyde (purity 85.4%), 100g tetrahydrofuran, and 0.6g activated carbon to a 250ml three-necked flask, heat to 60-65℃, decolorize for 2h; filter the activated carbon while hot, distill at atmospheric pressure until 45g remains in the bottle, add 140g water dropwise at 50-55℃, slowly cool to 0-5℃, and keep warm for 4h. Filter, dry the wet product at 70℃ for 24h, purity 99.46% (see Figure 1 ), the yield is 93.2%, and the terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals after purification.

[0058] Experimental Case 2

[0059] Add 20g crude terephthalaldehyde (purity 85.4%), 100g 1,4-dioxane, and 0.6g silica gel to a 250ml three-necked flask, heat to 60-65℃, decolorize for 2h, filter while hot, distill at atmospheric pressure until 49g remains in the flask, add 150g water dropwise at 50-55℃, slowly cool to 5-10℃, keep warm for 2h. Filter, dry the wet product at 50℃ for 30h, purity 99.56%, yield 89.8%, terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals after refining.

[0060] Experimental Case 3

[0061] Add 20g crude terephthalaldehyde (purity 85.4%), 100g tetrahydrofuran, 0.5g activated carbon, 0.5g diatomaceous earth into a 250ml three-necked flask, heat to 60-65°C, decolorize for 2h, filter while hot, distill at atmospheric pressure until 43g remains in the flask, add 150g water dropwise at 50-55°C, slowly cool to 5-10°C, keep warm for 2h. Filter, dry the wet product at 70°C for 24h, purity 98.94%, yield 90.7%, terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals after refining.

[0062] Experimental Case 4

[0063] Add 20g crude terephthalaldehyde (purity 85.4%), 140g tetrahydrofuran, and 1.0g activated carbon to a 250ml three-necked flask, heat to 60-65°C, decolorize for 2h, filter while hot, distill at atmospheric pressure until 48g remains in the flask, add 200g water dropwise at 50-55°C, slowly cool to 5-10°C, and keep warm for 2h. Filter, dry the wet product at 60°C under reduced pressure for 24h, purity 99.14%, yield 93.6%, terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals after refining.

[0064] Experimental Case 5

[0065] Add 20g crude terephthalaldehyde (purity 85.4%), 120g 1,4-dioxane, and 0.1g activated carbon to a 250ml three-necked flask, heat to 50-55°C, decolorize for 2h, filter while hot, and distill at atmospheric pressure until 43g remains in the flask, add 200g water dropwise at 50-55°C, slowly cool to 0-5°C, and keep warm for 2h. Filter, dry the wet product at 70°C for 24h, with a purity of 98.84% and a yield of 90.6%. After refining, terephthalaldehyde changes from dark yellow powder to off-white needle-shaped crystals.

[0066] Thus, the terephthalaldehyde to be purified and a solid decolorizer are added to an organic solvent for adsorption decolorization to obtain a decolorized solution; the decolorized solution is filtered to obtain a filtrate; water is dripped into the filtrate to precipitate the terephthalaldehyde, and the obtained terephthalaldehyde changes from dark yellow powder to white needle-shaped crystals after purification, and the purity is greater than 98.5%, and the quality is significantly improved.

[0067] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for refining terephthalaldehyde, comprising the following steps: Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent for adsorption decolorization to obtain a decolorized solution; filtering the decolorized solution to obtain a filtrate; Water was added dropwise to the filtrate to precipitate terephthalaldehyde.

2. The method for purifying terephthalaldehyde according to claim 1, characterized in that: After the step of adding water dropwise to the filtrate to precipitate terephthalaldehyde, the method further comprises: The precipitated terephthalaldehyde is filtered, and the filtered terephthalaldehyde is dried under reduced pressure at 50-85° C. to a constant weight to obtain dry terephthalaldehyde.

3. The method for purifying terephthalaldehyde according to claim 2, characterized in that: The step of adding the terephthalaldehyde to be purified and the solid decolorizing agent to the organic solvent for adsorption decolorization to obtain the decolorized solution comprises: Adding terephthalaldehyde to be purified and a solid decolorizing agent into an organic solvent; Under nitrogen protection, the solution is heated to 50-65°C and maintained for 1-2 hours for adsorption decolorization to obtain a decolorized solution.

4. The method for purifying terephthalaldehyde according to claim 2, characterized in that: The step of adding water dropwise to the filtrate to precipitate terephthalaldehyde comprises: Add water dropwise to the filtrate, and gradually cool the filtrate to 0-10°C and maintain for 3-6 hours to precipitate terephthalaldehyde.

5. The method for purifying terephthalaldehyde according to claim 2, characterized in that: The step of filtering the decolorized solution to obtain a filtrate comprises: The decolorized solution is filtered at a temperature of 45-60° C. to obtain a filtrate.

6. The method for purifying terephthalaldehyde according to claim 2, characterized in that: After the step of filtering the solution to obtain a filtrate, the method further comprises: The filtrate is distilled at atmospheric pressure to distill off part of the organic solvent.

7. The method for purifying terephthalaldehyde according to any one of claims 1 to 6, characterized in that: The organic solvent is selected from tetrahydrofuran, 1,4-dioxane, and a mixture thereof.

8. The method for purifying terephthalaldehyde according to any one of claims 1 to 6, characterized in that: The solid decolorizing agent is selected from at least one of activated carbon, silica gel and diatomaceous earth.

9. The method for purifying terephthalaldehyde according to any one of claims 1 to 6, characterized in that: The weight ratio of the terephthalaldehyde to be purified to the organic solvent is 1:4-7.

10. The method for purifying terephthalaldehyde according to any one of claims 1 to 6, characterized in that: The weight ratio of the terephthalaldehyde to be purified to the solid decolorizing agent and the water is 1:0.01-0.05:6-10.

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