Synthesis Process of 2,4-Dihydroxybenzoic Acid

Abstract

The present invention relates to the technical field of 2,4-dihydroxybenzoic acid synthesis, and provides a 2,4-dihydroxybenzoic acid synthesis process, which includes the following steps: After mixing water, a catalyst, sodium bicarbonate and resorcinol for reaction, 2,4-dihydroxybenzoic acid is obtained, and the catalyst is a supported catalyst; the supported catalyst is obtained by treating a carrier with a mixed solution of ammonium hexafluorophosphate and diethylamine, and then impregnating it with an active component solution. Through the above technical solution, the problems of low product yield and low purity in the existing 2,4-dihydroxybenzoic acid synthesis process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of 2,4-dihydroxybenzoic acid, and specifically, to the synthesis process of 2,4-dihydroxybenzoic acid. Background Art

[0002] As an important organic intermediate, 2,4-dihydroxybenzoic acid is mainly used in the synthesis in the fields of dyes, pharmaceuticals, etc. and the fine chemical industry, etc., for producing products such as the ultraviolet absorber UV, the dye acid mordant pink 3BM, etc. 2,4-Dihydroxybenzoic acid also has the chemical properties of resorcinol and salicylic acid, can prepare the pharmaceutical intermediate 4-methoxysalicylic acid, and can develop a series of pharmaceutical varieties. It can also be used as a chemical reagent for colorimetric determination of iron, titanium and other elements, and can also be used as a bactericide. With the increasingly wide application of 2,4-dihydroxybenzoic acid in the fields of dyes, pharmaceuticals, etc., the demand for 2,4-dihydroxybenzoic acid in the relevant industries at home and abroad shows an increasing trend.

[0003] However, at present, the output and purity of 2,4-dihydroxybenzoic acid products cannot meet the market demand, and there are problems of low product yield and low purity. Summary of the Invention

[0004] The present invention provides a synthesis process of 2,4-dihydroxybenzoic acid, which solves the problems of low product yield and low purity in the synthesis process of 2,4-dihydroxybenzoic acid in the related art.

[0005] The technical solution of the present invention is as follows:

[0006] A synthesis process of 2,4-dihydroxybenzoic acid, comprising the following steps: reacting water, a catalyst, sodium bicarbonate and resorcinol to obtain 2,4-dihydroxybenzoic acid, wherein the catalyst is a supported catalyst; the supported catalyst is obtained by treating a carrier with a mixed solution of ammonium hexafluorophosphate and diethylamine, and then impregnating with an active component solution.

[0007] As a further technical solution, the addition amount of the catalyst is 2-6% of the mass of resorcinol.

[0008] As a further technical solution, in the mixed solution, the sum of the masses of ammonium hexafluorophosphate and diethylamine is 8-10% of the mass of the mixed solution.

[0009] As a further technical solution, the mass ratio of ammonium hexafluorophosphate to diethylamine is 1:1-3.

[0010] As a further technical solution, the mass ratio of ammonium hexafluorophosphate to diethylamine is 1:2.

[0011] As a further technical solution, the carrier is a molecular sieve; the molecular sieve includes one of ZMS-5, TS-1, USY-3, and NaY.

[0012] As a further technical solution, the molecular sieve is ZMS-5.

[0013] As a further technical solution, the metal element in the active component of the supported catalyst includes one or more of zinc, chromium, manganese, and cerium.

[0014] As a further technical solution, the metal element in the active component of the supported catalyst is chromium.

[0015] As a further technical solution, the addition amount of the supported catalyst is 2-6% of the mass of resorcinol.

[0016] As a further technical solution, the loading amount of the active component on the carrier is 4-8 wt%.

[0017] As a further technical solution, the preparation method of the supported catalyst is characterized by including the following steps:

[0018] S1. After treating the carrier with a mixed solution containing ammonium hexafluorophosphate and diethylamine, drying it to obtain a pretreated carrier;

[0019] S2. Immersing the pretreated carrier in the active component solution and drying it to obtain the supported catalyst.

[0020] As a further technical solution, the active component is configured into an active solution according to the principle of the equal-volume impregnation method.

[0021] As a further technical solution, the treatment temperature in S1 is 65-75 °C, and the treatment time is 8-10 h.

[0022] As a further technical solution, the impregnation temperature in S2 is 25-30 °C, and the impregnation time is 35-38 h.

[0023] As a further technical solution, the reaction temperature is 90-100 °C, the reaction pressure is 0.2-0.3 MPa, and the reaction time is 5-6 h.

[0024] The working principle and beneficial effects of the present invention are as follows:

[0025] In the process of the present invention, a supported catalyst is added. A molecular sieve is used as the carrier of the supported catalyst, and zinc, cadmium, etc. containing metal elements are used as active components. After the carrier is pretreated, the active components can be fully impregnated, improving the catalytic effect of the supported catalyst, increasing the yield and purity of 2,4-dihydroxybenzoic acid. When pretreating, a mixed solution containing ammonium hexafluorophosphate and diethylamine is used to treat the carrier, and the prepared catalyst can further increase the yield and purity of 2,4-dihydroxybenzoic acid. Specific Embodiments

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0027] Example 1

[0028] 70 mL of water, 0.4 g of supported catalyst, 22 g of sodium bicarbonate, and 10 g of resorcinol are successively added to a reaction kettle. Carbon dioxide is introduced, and the temperature is raised to 90 °C. Under a carbon dioxide stream, the pressure is controlled at 0.2 - 0.3 MPa, and the reflux reaction is carried out for 6 h. After the reaction is completed, it is cooled, the introduction of carbon dioxide is stopped, and it is cooled to room temperature. After filtration, the filtrate is added to a reactor, and concentrated hydrochloric acid is dropped until the pH of the reaction solution is 1. After suction filtration and washing with distilled water, it is recrystallized with distilled water and dried at 115 °C to obtain 13.39 g of 2,4-dihydroxybenzoic acid. The yield of 2,4-dihydroxybenzoic acid is 96.36%, and the purity is 99.4%.

[0029] The preparation method of the supported catalyst is as follows:

[0030] S1. 5 g of ZMS-5 molecular sieve is added to 100 g of a mixed solution (a mixed solution obtained by mixing 2.7 g of ammonium hexafluorophosphate, 5.3 g of diethylamine, and 92 g of water). After stirring at 65 °C for 10 h, suction filtration is carried out. After washing with distilled water, it is dried at 100 °C for 10 h to obtain a pretreated carrier.

[0031] S2. The above pretreated carrier is impregnated in 10 mL of an active component solution (1.54 g of chromium(III) nitrate nonahydrate is configured into 10 mL of an active component solution). It is impregnated at 30 °C for 35 h, dried at 100 °C for 12 h, then placed in a muffle furnace and calcined at 450 °C for 5 h, and taken out and cooled to room temperature. The loading amount of metal chromium in the supported catalyst is 4 wt%.

[0032] Example 2

[0033] 70 mL of water, 0.4 g of supported catalyst, 22 g of sodium bicarbonate and 10 g of resorcinol were added to a reaction kettle in sequence. Carbon dioxide was introduced, and the temperature was raised to 95 °C. Under a carbon dioxide stream, the pressure was controlled at 0.2 - 0.3 MPa, and the reflux reaction was carried out for 5.5 h. After the reaction was completed, it was cooled, the introduction of carbon dioxide was stopped, and it was cooled to room temperature. Then it was filtered, and the filtrate was added to a reactor. Concentrated hydrochloric acid was added dropwise until the pH of the reaction solution was 1. After suction filtration and washing with distilled water, it was recrystallized with distilled water and dried at 115 °C to obtain 13.45 g of 2,4-dihydroxybenzoic acid. The yield of 2,4-dihydroxybenzoic acid was 96.74%, and the purity was 99.5%.

[0034] The preparation method of the supported catalyst is as follows:

[0035] S1. 5 g of ZMS-5 molecular sieve was added to 100 g of a mixed solution (a mixed solution obtained by mixing 3 g of ammonium hexafluorophosphate, 6 g of diethylamine and 91 g of water). After stirring at 70 °C for 9 h, suction filtration was carried out. After washing with distilled water, it was dried at 100 °C for 10 h to obtain a pretreated carrier;

[0036] S2. The above pretreated carrier was impregnated in 100 g of an active component solution (2.31 g of chromium(III) nitrate nonahydrate was formulated into 11 mL of an active component solution). It was impregnated at 28 °C for 36 h, dried at 100 °C for 12 h, then put into a muffle furnace and calcined at 450 °C for 5 h, and taken out and cooled to room temperature. The metal loading amount of the supported catalyst was 6 wt%.

[0037] Example 3

[0038] 70 mL of water, 0.4 g of supported catalyst, 22 g of sodium bicarbonate and 10 g of resorcinol were added to a reaction kettle in sequence. Carbon dioxide was introduced, and the temperature was raised to 100 °C. Under a carbon dioxide stream, the pressure was controlled at 0.2 - 0.3 MPa, and the reflux reaction was carried out for 5 h. After the reaction was completed, it was cooled, the introduction of carbon dioxide was stopped, and it was cooled to room temperature. Then it was filtered, and the filtrate was added to a reactor. Concentrated hydrochloric acid was added dropwise until the pH of the reaction solution was 1. After suction filtration and washing with distilled water, it was recrystallized with distilled water and dried at 115 °C to obtain 13.47 g of 2,4-dihydroxybenzoic acid. The yield of 2,4-dihydroxybenzoic acid was 96.92%, and the purity was 99.7%.

[0039] The preparation method of the supported catalyst is as follows:

[0040] S1. 5 g of ZMS-5 molecular sieve was added to 100 g of a mixed solution (a mixed solution obtained by mixing 3.3 g of ammonium hexafluorophosphate, 6.7 g of diethylamine and 90 g of water). After stirring at 75 °C for 8 h, suction filtration was carried out. After washing with distilled water, it was dried at 100 °C for 10 h to obtain a pretreated carrier;

[0041] S2. Immerse the above-pretreated carrier in 100 g of the active component solution (prepare 12 mL of the active component solution by dissolving 3.08 g of chromium nitrate nonahydrate), immerse at 25 °C for 38 h, dry at 100 °C for 12 h, then put it into a muffle furnace and calcine at 450 °C for 5 h, take it out and cool to room temperature. The loading amount of the supported catalyst metal is 8 wt%.

[0042] Example 4

[0043] Compared with Example 2, the difference in Example 4 is that the addition amount of the supported catalyst is 0.2 g, and as a result, 12.96 g of 2,4-dihydroxybenzoic acid is obtained. The yield of 2,4-dihydroxybenzoic acid is 93.23%, and the purity is 99.2%.

[0044] Example 5

[0045] Compared with Example 2, the difference in Example 5 is that the addition amount of the supported catalyst is 0.6 g, and as a result, 13.49 g of 2,4-dihydroxybenzoic acid is obtained. The yield of 2,4-dihydroxybenzoic acid is 97.06%, and the purity is 99.8%.

[0046] Example 6

[0047] Compared with Example 2, the difference in Example 6 is that in the mixed solution, there are 4.5 g of ammonium hexafluorophosphate, 4.5 g of diethylamine, and 91 g of water. As a result, 13.31 g of 2,4-dihydroxybenzoic acid is obtained. The yield of 2,4-dihydroxybenzoic acid is 95.78%, and the purity is 99.3%.

[0048] Example 7

[0049] Compared with Example 2, the difference in Example 6 is that in the mixed solution, there are 2.25 g of ammonium hexafluorophosphate, 6.75 g of diethylamine, and 91 g of water. As a result, 13.34 g of 2,4-dihydroxybenzoic acid is obtained. The yield of 2,4-dihydroxybenzoic acid is 95.95%, and the purity is 99.4%.

[0050] Comparative Example 1

[0051] Compared with Example 2, the difference in Comparative Example 1 is that diethylamine is not added, and the addition amount of ammonium hexafluorophosphate is 9 g. As a result, 12.98 g of 2,4-dihydroxybenzoic acid is obtained. The yield of 2,4-dihydroxybenzoic acid is 93.37%, and the purity is 99.1%.

[0052] Comparative Example 2

[0053] Compared with Example 2, the difference in Comparative Example 2 is that ammonium hexafluorophosphate is not added, and the addition amount of diethylamine is 9 g. As a result, 13.19 g of 2,4-dihydroxybenzoic acid is obtained, and the yield of 2,4-dihydroxybenzoic acid is 94.86%, and the purity is 99.2%.

[0054] Comparative Example 3

[0055] Compared with Example 2, the difference in Comparative Example 3 is that the supported catalyst is not added. As a result, 12.46 g of 2,4-dihydroxybenzoic acid is obtained, and the yield of 2,4-dihydroxybenzoic acid is 89.66%, and the purity is 99.0%.

[0056] Comparative Example 4

[0057] Compared with Example 2, the difference in Comparative Example 4 is that in the mixed solution, there are 1.5 g of ammonium hexafluorophosphate, 7.5 g of diethylamine, and 91 g of water. As a result, 13.23 g of 2,4-dihydroxybenzoic acid is obtained, and the yield of 2,4-dihydroxybenzoic acid is 95.36%, and the purity is 99.4%.

[0058] Comparative Example 5

[0059] Compared with Example 2, the difference in Comparative Example 5 is that in the mixed solution, there are 6 g of ammonium hexafluorophosphate, 3 g of diethylamine, and 91 g of water. As a result, 13.23 g of 2,4-dihydroxybenzoic acid is obtained, and the yield of 2,4-dihydroxybenzoic acid is 95.15%, and the purity is 99.3%.

[0060] It can be seen from the above Examples 1-7 and Comparative Examples 1-5 that compared with Example 2, in Examples 6-7, the mass ratio of ammonium hexafluorophosphate and diethylamine was changed. As a result, the yield and purity of 2,4-dihydroxybenzoic acid in Examples 6-7 are both lower than those in Example 2, indicating that when the mass ratio of ammonium hexafluorophosphate and diethylamine is 1:2, the yield and purity of 2,4-dihydroxybenzoic acid can be better improved.

[0061] Compared with Example 2, in Comparative Example 1, only ammonium hexafluorophosphate was added, in Comparative Example 2, only diethylamine was added, and in Comparative Example 3, the supported catalyst was not added. As a result, the yield and purity of 2,4-dihydroxybenzoic acid in Comparative Examples 1-3 are both lower than those in Example 2, indicating that the simultaneous use of ammonium hexafluorophosphate and diethylamine to treat the carrier can improve the yield and purity of 2,4-dihydroxybenzoic acid.

[0062] Compared with Example 2, in Comparative Examples 4-5, the mass ratio of ammonium hexafluorophosphate to diethylamine was changed. As a result, the yields and purities of 2,4-dihydroxybenzoic acid in Comparative Examples 4-5 were lower than those in Example 2, and the yields and purities of 2,4-dihydroxybenzoic acid in Comparative Examples 4-5 were also lower than those in Example 6 and Example 7. This shows that limiting the mass ratio of ammonium hexafluorophosphate to diethylamine to 1:1-3 can better improve the yield and purity of 2,4-dihydroxybenzoic acid.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A synthesis process of 2,4-dihydroxybenzoic acid, characterized in that, It includes the following steps: reacting water, a catalyst, sodium bicarbonate and resorcinol under a carbon dioxide atmosphere to obtain 2,4-dihydroxybenzoic acid, wherein the catalyst is a supported catalyst; the supported catalyst is obtained by treating a support with a mixed solution of ammonium hexafluorophosphate and diethylamine and then impregnating it with an active component solution; the support is ZMS-5 molecular sieve, and the metal element in the active component is chromium.

2. The synthesis process of 2,4-dihydroxybenzoic acid according to claim 1, characterized in that, In the mixed solution, the sum of the masses of ammonium hexafluorophosphate and diethylamine is 8-10% of the mass of the mixed solution.

3. The synthesis process of 2,4-dihydroxybenzoic acid according to claim 1, characterized in that, The mass ratio of ammonium hexafluorophosphate to diethylamine is 1:1-3.

4. A process for synthesizing 2,4-dihydroxybenzoic acid according to claim 1, characterized in that, The addition amount of the supported catalyst is 2-6% of the mass of resorcinol.

5. A process for synthesizing 2,4-dihydroxybenzoic acid according to claim 1, characterized in that, The preparation method of the supported catalyst is characterized by including the following steps: S1. Treat the support with a mixed solution containing ammonium hexafluorophosphate and diethylamine, and then dry it to obtain a pretreated support; S2. Immerse the pretreated support in the active component solution and dry it to obtain the supported catalyst.

6. The synthesis process of 2,4-dihydroxybenzoic acid according to claim 5, characterized in that, In S1, the treatment temperature is 65-75 °C and the treatment time is 3-3.5 h.

7. A process for synthesizing 2,4-dihydroxybenzoic acid according to claim 5, characterized in that, In S2, the impregnation temperature is 25-30 °C and the impregnation time is 9-10 h.

8. A synthesis process of 2,4-dihydroxybenzoic acid according to claim 1, characterized in that, The reaction temperature is 90-100 °C, the reaction pressure is 0.2-0.3 MPa, and the reaction time is 5-6 h.