A method for preparing 5-hydroxyisophthalic acid

Abstract

This invention discloses a method for preparing 5-hydroxyisophthalic acid. The method uses sodium isophthalate-5-sulfonate or potassium isophthalate-5-sulfonate as raw materials, reacting them in an aqueous solution of NaOH or KOH, followed by acidification with dilute hydrochloric acid and post-treatment to obtain the target product, 5-hydroxyisophthalic acid. The reaction of sodium isophthalate-5-sulfonate or potassium isophthalate-5-sulfonate in the aqueous solution of NaOH or KOH is carried out in a tubular reactor. Compared with existing methods, the process route of this invention has advantages such as ease of operation, high yield, low cost, and less wastewater.

Description

Technical Field

[0001] This invention relates to a method for preparing 5-hydroxyisophthalic acid, belonging to the field of compound preparation technology. Background Technology

[0002] 5-Hydroxyisophthalic acid has the following structural formula:

[0003]

[0004] This compound is a commonly used chemical intermediate, and its preparation methods are as follows:

[0005] The synthetic route of Chinese patent CN106831397A is as follows:

[0006]

[0007] This process uses 5-bromoisophthalic acid as raw material, and hydrolyzes it in a liquid alkaline aqueous solution with cuprous oxide as a catalyst for 20 hours. The product is then acidified with dilute hydrochloric acid, yielding 86%. However, due to the high price of the starting material 5-bromoisophthalic acid and the long hydrolysis time, the manufacturing cost is relatively high.

[0008] The synthetic route of US Patent US2756149 is as follows:

[0009]

[0010] The procedure involves adding a mixture of sodium hydroxide and potassium hydroxide to a stainless steel cup, heating it to 220°C to melt it, then adding potassium isophthalic acid-5-sulfonate, controlling the temperature at 215–235°C, stirring vigorously for 30 minutes, cooling at the reaction endpoint, adding water, acidifying with hydrochloric acid to obtain a crude product, and then recrystallizing with water to obtain the final product with a yield of 81.5%.

[0011] The raw materials used in this route, potassium 5-sulfonate isophthalic acid, are readily available and inexpensive. However, the amount of mixed alkali used in this process is very large, 41 times the amount of the starting material (molar ratio). The reaction mixture is highly viscous, making stirring difficult, resulting in uneven temperature and low yield. At the same time, it generates a large amount of high-salt wastewater, making it difficult to scale up production. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a new method for preparing 5-hydroxyisophthalic acid.

[0013] To address the above technical problems, this invention discloses a method for preparing 5-hydroxyisophthalic acid. This method uses sodium isophthalate-5-sulfonate or potassium isophthalate-5-sulfonate as raw materials, reacting them in an aqueous solution of NaOH or KOH, followed by acidification with dilute hydrochloric acid and post-treatment to obtain the target product, 5-hydroxyisophthalic acid. The reaction of sodium isophthalate-5-sulfonate or potassium isophthalate-5-sulfonate in the aqueous solution of NaOH or KOH is carried out in a tubular reactor. The post-treatment involves sequential filtration and recrystallization. The reaction equation is as follows:

[0014]

[0015] Furthermore, the reaction temperature is 200–300°C, preferably 220–250°C.

[0016] Furthermore, the molar ratio of NaOH or KOH to sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate is 4 to 40:1, preferably 7 to 11:1.

[0017] Furthermore, in the aqueous solution of NaOH or KOH, the mass amount of water is 10% to 200% of the mass amount of NaOH or KOH, preferably 50%.

[0018] Furthermore, the residence time of the reactants in the tubular reactor is 0.25–20 hours, preferably 40–60 minutes. This residence time is controlled by adjusting the feed rate according to the volume of the tubular reactor.

[0019] Furthermore, the tubular reactor is a dynamic tubular reactor, in which the reaction raw materials are continuously fed using a slurry pump, and the reaction products are continuously discharged.

[0020] Using the preparation method of this invention, the content of the target product in the product is >99.0%, and the molar yield can reach up to 96.6%. Compared with US Patent US2756149, it has the following advantages:

[0021] 1. In US2756149, a mixed alkali of KOH / NaOH is used as the reaction medium, and the amount used is very large. If the amount is reduced, stirring becomes impossible. This invention uses an aqueous solution of NaOH (KOH) as the reaction medium, which greatly reduces the amount of alkali used. Due to the addition of water, the solubility of the materials is increased, stirring is easier, and temperature is easier to control.

[0022] 2. US2756149 is an atmospheric pressure batch reaction, which has low yield and is difficult to operate. This invention uses a dynamic tubular reactor to achieve continuous production, with less equipment investment, high output and low production cost.

[0023] Overall, the process route of the present invention has advantages over the routes in the prior art, such as ease of operation, high yield, low cost, and less wastewater. Detailed Implementation

[0024] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1: Synthesis of 5-hydroxyisophthalic acid

[0026] In a stainless steel container, add NaOH and water and stir to dissolve. Then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. NaOH:water:sodium isophthalic acid-5-sulfonate = 8:8.8:1 (molar ratio).

[0027] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified with 7 wt% hydrochloric acid to pH < 3.0, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 176.27 g of 5-hydroxyisophthalic acid with a content of 99.5 wt% and a product molar yield of 96.3%.

[0028] Example 2: Synthesis of 5-hydroxyisophthalic acid

[0029] In a stainless steel container, add NaOH and water and stir to dissolve. Then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. The molar ratio of NaOH to water to sodium isophthalic acid-5-sulfonate is 5:5.6:1.

[0030] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified to pH < 3.0 using 7 wt% dilute hydrochloric acid, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 163.9 g of 5-hydroxyisophthalic acid with a content of 95 wt% and a product molar yield of 85.5%.

[0031] Example 3: Synthesis of 5-hydroxyisophthalic acid

[0032] In a stainless steel container, add NaOH and water and stir to dissolve. Then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. NaOH:water:sodium isophthalic acid-5-sulfonate = 11:12.2:1 (molar ratio).

[0033] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified with 7 wt% hydrochloric acid to pH < 3.0, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 175.24 g of 5-hydroxyisophthalic acid with a content of 99.3 wt% and a product molar yield of 95.6%.

[0034] Example 4: Synthesis of 5-hydroxyisophthalic acid

[0035] In a stainless steel container, add KOH and water and stir to dissolve. Then add potassium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. KOH:water:sodium isophthalic acid-5-sulfonate = 8:12.5:1 (molar ratio).

[0036] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor, acidified with 7 wt% hydrochloric acid to pH < 3.0, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 176.46% 5-hydroxyisophthalic acid with a content of 99.6 wt% and a product molar yield of 96.5%.

[0037] Example 5: Synthesis of 5-hydroxyisophthalic acid

[0038] In a stainless steel container, add NaOH and water, stir to dissolve, then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. The molar ratio of NaOH to water to sodium isophthalic acid-5-sulfonate is 8:8.8:1.

[0039] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 80 mL / min using a slurry pump. After 25 minutes, the reaction liquid was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified with 7 wt% hydrochloric acid to pH < 3.0, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 160.2 g of 5-hydroxyisophthalic acid with a content of 93.0 wt% and a product molar yield of 81.1%.

[0040] Example 6: Synthesis of 5-hydroxyisophthalic acid

[0041] In a stainless steel container, add NaOH and water, stir to dissolve, then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. The molar ratio of NaOH to water to sodium isophthalic acid-5-sulfonate is 8:8.8:1.

[0042] In a 2000 mL dynamic tubular reactor, the temperature was set to 230 °C. The prepared slurry was fed at a rate of 20 mL / min using a slurry pump. After 100 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified with 7 wt% hydrochloric acid to pH < 3.0, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with water to obtain 176.4 g of 5-hydroxyisophthalic acid with a content of 99.2 wt% and a product molar yield of 96.1%.

[0043] Example 7: Synthesis of 5-hydroxyisophthalic acid

[0044] In a stainless steel container, add NaOH and water, stir to dissolve, then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. The molar ratio of NaOH to water to sodium isophthalic acid-5-sulfonate is 8:8.8:1.

[0045] In a 2000 mL dynamic tubular reactor, the temperature was set to 200 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified to pH < 3.0 using 7 wt% hydrochloric acid, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with process water to obtain 128.5 g of 5-hydroxyisophthalic acid with a content of 71.1 wt% and a product molar yield of 50.1%.

[0046] Example 8: Synthesis of 5-hydroxyisophthalic acid

[0047] In a stainless steel container, add NaOH and water, stir to dissolve, then add sodium isophthalic acid-5-sulfonate and continue stirring until the material becomes a slurry. The molar ratio of NaOH to water to sodium isophthalic acid-5-sulfonate is 8:8.8:1.

[0048] In a 2000 mL dynamic tubular reactor, the temperature was set to 250 °C. The prepared slurry was fed at a rate of 40 mL / min using a slurry pump. After 50 minutes, the reaction solution was collected from the back pressure valve of the dynamic tubular reactor. The solution was acidified to pH < 3.0 using 7 wt% hydrochloric acid, cooled to temperature < 20 °C, and the crude product was filtered out. The crude product was recrystallized with process water to obtain 177 g of 5-hydroxyisophthalic acid with a content of 99.4 wt% and a product molar yield of 96.6%.

[0049] In Examples 1-8, the feed amount of sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate is 1 mol, and the molar yield of the product is calculated based on the molar amount of sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate used. The mass concentration of the dilute hydrochloric acid used is not high, 20 wt% is sufficient.

Claims

1. A process for the preparation of 5-hydroxyisophthalic acid, characterized in that: The preparation method uses sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate as raw material, reacts in a NaOH or KOH aqueous solution, and then acidifies through dilute hydrochloric acid, post-treatment to obtain the target product 5-hydroxy isophthalic acid, the reaction of sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate in the NaOH or KOH aqueous solution is carried out in a dynamic tubular reactor, The reaction raw material is continuously fed using a slurry pump, and the reaction product is continuously discharged, The reaction temperature is 220-250 DEG C, The molar dosage ratio of NaOH or KOH to sodium isophthalic acid-5-sulfonate or potassium isophthalic acid-5-sulfonate is 7-11:1, In the NaOH or KOH aqueous solution, the mass dosage of water is 10%-200% of the mass dosage of NaOH or KOH, The residence time of the reaction raw material in the pipeline of the tubular reactor is 40-60 minutes.

2. The method of preparing 5-hydroxyisophthalic acid according to claim 1, characterized in that: In the NaOH or KOH aqueous solution, the mass dosage of water is 50% of the mass dosage of NaOH or KOH.

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