A method for purifying and refining 2,7-naphthalenedisulfonic acid

Abstract

This invention relates to a method for purifying and refining 2,7-naphthalenedisulfonic acid, belonging to the field of compound purification and refining technology. The invention provides a method for purifying and refining 2,7-naphthalenedisulfonic acid, comprising the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 50%-60%, heating to dissolve, cooling to crystallize, and obtaining purified 2,7-naphthalenedisulfonic acid. This invention uses sulfuric acid solution as a solvent for recrystallization, thereby purifying and refining the crude 2,7-naphthalenedisulfonic acid product. Through research, this invention has found that purifying and refining crude 2,7-naphthalenedisulfonic acid with a sulfuric acid solution of 50%-60% yields excellent yield and purity.

Description

Technical Field

[0001] This invention belongs to the field of compound purification technology, specifically relating to a method for purifying and refining 2,7-naphthalenedisulfonic acid. Background Technology

[0002] 2,7-Naphthalenedisulfonic acid is an important intermediate in the preparation of dyes, organic pigments, pharmaceuticals and agrochemicals. With the continuous development of research, the applications of 2,7-naphthalenedisulfonic acid are becoming more and more widespread.

[0003] The preparation of 2,7-naphthalenedisulfonic acid mainly involves sulfonation of refined naphthalene with concentrated sulfuric acid. However, the crude 2,7-naphthalenedisulfonic acid product obtained from the sulfonation reaction often contains byproducts such as 2,6-naphthalenedisulfonic acid, 2-naphthalenedisulfonic acid, and 1,6-naphthalenedisulfonic acid. Therefore, purification and refining of the crude 2,7-naphthalenedisulfonic acid product are necessary. Currently, there are two commonly used purification methods. One method involves adding p-phenylenediamine to the crude 2,7-naphthalenedisulfonic acid product to separate the ammonium salt of 2,6-naphthalenedisulfonic acid, achieving the purpose of purification. The drawback of this method is that the addition of a new substance increases costs and makes the separation process more complex. The other method involves adding sodium chloride to the crude 2,7-naphthalenedisulfonic acid solution to form sodium 2,7-naphthalenedisulfonic acid. This method increases wastewater and can only produce sodium 2,7-naphthalenedisulfonic acid, not 2,7-naphthalenedisulfonic acid.

[0004] Therefore, it is of great significance to provide a simple and efficient method for purifying and refining 2,7-naphthalenedisulfonic acid. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for purifying and refining 2,7-naphthalenedisulfonic acid.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a method for purifying and refining 2,7-naphthalenedisulfonic acid, comprising the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 50%-60%, heating to dissolve, cooling to crystallize, and obtaining purified 2,7-naphthalenedisulfonic acid.

[0008] The present invention provides a purification and refining method using sulfuric acid solution as a solvent for recrystallization, thereby purifying and refining crude 2,7-naphthalenedisulfonic acid. The present invention has found that using a sulfuric acid solution with an acidity of 50%-60% to purify and refine crude 2,7-naphthalenedisulfonic acid results in excellent yield and purity of the 2,7-naphthalenedisulfonic acid.

[0009] In a preferred embodiment of the purification method for 2,7-naphthalenedisulfonic acid described in this invention, the acidity of the sulfuric acid solution is 57.5%-60%.

[0010] In a preferred embodiment of the purification method for 2,7-naphthalenedisulfonic acid described in this invention, the mass ratio of the crude 2,7-naphthalenedisulfonic acid product to the sulfuric acid solution is 1:(1-3).

[0011] In a preferred embodiment of the purification method for 2,7-naphthalenedisulfonic acid described in this invention, the mass ratio of the crude 2,7-naphthalenedisulfonic acid product to the sulfuric acid solution is 1:2.

[0012] In a preferred embodiment of the purification and refining method for 2,7-naphthalenedisulfonic acid described in this invention, the temperature for cooling crystallization is 0°C-35°C.

[0013] In a preferred embodiment of the purification and refining method for 2,7-naphthalenedisulfonic acid described in this invention, the temperature for cooling crystallization is 10°C-30°C.

[0014] In a preferred embodiment of the purification and refining method for 2,7-naphthalenedisulfonic acid described in this invention, the cooling crystallization temperature is 20°C.

[0015] The temperature of cooling crystallization also affects the yield and purity of 2,7-naphthalenedisulfonic acid. The preferred cooling crystallization temperature is 0°C-35°C, more preferably 10°C-30°C, and even more preferably 20°C.

[0016] In a preferred embodiment of the purification and refining method for 2,7-naphthalenedisulfonic acid described in this invention, the cooling crystallization time is 10-14 hours.

[0017] In a preferred embodiment of the purification and refining method for 2,7-naphthalenedisulfonic acid described in this invention, the cooling crystallization time is 12 hours.

[0018] As a preferred embodiment of the purification and refining method of 2,7-naphthalenedisulfonic acid described in this invention, the preparation method of the crude 2,7-naphthalenedisulfonic acid product includes the following steps: mixing naphthalene and concentrated sulfuric acid to react and obtain a reaction solution; then adjusting the acidity of the obtained reaction solution to 41%-43.5% and controlling the temperature at 10℃-35℃ to crystallize, thereby obtaining the crude 2,7-naphthalenedisulfonic acid product.

[0019] The crude 2,7-naphthalenedisulfonic acid product of this invention can be obtained by sulfonation reaction of naphthalene and concentrated sulfuric acid. Further research in this invention has found that adjusting the acidity of the reaction solution to 41%-43.5% and crystallizing at 10℃-35℃ results in a crude 2,7-naphthalenedisulfonic acid product with high purity and yield. At the same temperature, as the acidity decreases, the crystallization purity of 2,7-naphthalenedisulfonic acid shows a trend of first increasing and then decreasing, with the optimal acidity range being 41%-43.5%. Furthermore, at the same acidity, when the crystallization temperature is too low, such as 0℃, the crystallization purity of 2,7-naphthalenedisulfonic acid is lower than that at 10℃-35℃. More preferably, the acidity of the reaction solution is adjusted to 43.5%, and the crystallization temperature is controlled at 25℃. Specifically, the method for adjusting the acidity of the reaction solution according to this invention can be dilution with water.

[0020] Specifically, the acidity mentioned in this invention refers to the 0.10 mol·L⁻¹ consumed when titrating 10 mL of the test solution to the endpoint of the phenolphthalein indicator. -1 The volume of sodium hydroxide solution in milliliters is called its acidity. The formula for calculating acidity is as follows:

[0021]

[0022] Where C is the concentration of the standard sodium hydroxide solution, in mol·L⁻¹ -1 V is the volume of standard sodium hydroxide solution consumed in the titration, mL; V0 is the total volume of the sample dilution, mL; K is the conversion factor, the mass of acid required to consume 1 mmol of sodium hydroxide, for example, if sulfuric acid is the main component, K = 49; m is the sample mass, g; V1 is the volume of the test solution, mL.

[0023] The present invention has the following beneficial effects: The purification and refining method of the present invention uses sulfuric acid solution as a solvent for recrystallization, thereby purifying and refining the crude 2,7-naphthalenedisulfonic acid product. By controlling the acidity of the sulfuric acid solution to 50%-60% and optimizing the crystallization temperature, the present invention purifies and refines the crude 2,7-naphthalenedisulfonic acid product, resulting in excellent yield and purity of 2,7-naphthalenedisulfonic acid. Detailed Implementation

[0024] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0026] In the following examples and comparative examples, the preparation method of the crude 2,7-naphthalenedisulfonic acid product includes the following steps: naphthalene and concentrated sulfuric acid are mixed and reacted at 160°C for 6 hours to obtain a reaction solution; then, the acidity of the obtained reaction solution is adjusted to 42% by adding water, and the temperature is controlled at 20°C for crystallization for 12 hours to obtain the crude 2,7-naphthalenedisulfonic acid product.

[0027] Example 1

[0028] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 60% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0029] Example 2

[0030] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 57.5% in a mass ratio of 1:2 between the crude 2,7-naphthalenedisulfonic acid and the sulfuric acid solution; heating until completely dissolved; cooling to 20°C for crystallization; and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0031] Example 3

[0032] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 55% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0033] Example 4

[0034] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 50% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0035] Example 5

[0036] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 60% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 10°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0037] Example 6

[0038] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 60% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 30°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0039] Example 7

[0040] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 60% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 0°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0041] Example 8

[0042] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 60% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 35°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0043] Comparative Example 1

[0044] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 47.5% in a mass ratio of 1:2, heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0045] Comparative Example 2

[0046] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 45% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0047] Comparative Example 3

[0048] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 40% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0049] Comparative Example 4

[0050] A method for purifying and refining 2,7-naphthalenedisulfonic acid includes the following steps: adding crude 2,7-naphthalenedisulfonic acid to a sulfuric acid solution with an acidity of 65% (the mass ratio of the crude 2,7-naphthalenedisulfonic acid to the sulfuric acid solution is 1:2), heating until completely dissolved, cooling to 20°C for crystallization, and crystallizing for 14 hours to obtain purified 2,7-naphthalenedisulfonic acid.

[0051] The yield and purity of 2,7-naphthalenedisulfonic acid after crystallization in the examples and comparative examples were determined by external standard HPLC. The HPLC conditions were as follows: 4.60 × 150 mm Extend-C18 column; detection wavelength set at 230 nm; column temperature set at 30 °C; mobile phase was a mixture of methanol and a liquid (volume ratio 40:60, with the liquid consisting of 1 g·L⁻¹) -1 Ammonium acetate and 5.80 g·L -1 (Composition of tetrabutylammonium bromide); Flow rate set at 0.80 mL / min -1 The detector is a UV detector; the injection volume is 10 μL.

[0052] The test results are shown in Table 1.

[0053] Table 1. Yield and purity test results of 2,7-naphthalenedisulfonic acid obtained from the examples and comparative examples.

[0054]

[0055] As can be seen from Table 1, the purification method of this invention has higher yield and purity than the comparative example.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for purifying and refining 2,7-naphthalenedisulfonic acid, characterized in that, Includes the following steps: The crude 2,7-naphthalenedisulfonic acid product is added to a sulfuric acid solution, heated to dissolve, and then cooled to crystallize, yielding purified 2,7-naphthalenedisulfonic acid. The acidity of the sulfuric acid solution is 57.5%-60%. The cooling crystallization temperature is 20°C. The preparation method of the crude 2,7-naphthalenedisulfonic acid product includes the following steps: naphthalene and concentrated sulfuric acid are mixed and reacted at 160°C for 6 hours to obtain a reaction solution; the acidity of the obtained reaction solution is then adjusted to 42%, and the temperature is controlled at 20°C to crystallize for 12 hours, thus obtaining the crude 2,7-naphthalenedisulfonic acid product.

2. The method for purifying and refining 2,7-naphthalenedisulfonic acid according to claim 1, characterized in that, The mass ratio of the crude 2,7-naphthalenedisulfonic acid product to the sulfuric acid solution is 1:(1-3).

3. The method for purifying and refining 2,7-naphthalenedisulfonic acid according to claim 1 or 2, characterized in that, The mass ratio of the crude 2,7-naphthalenedisulfonic acid product to the sulfuric acid solution is 1:

2.

4. The method for purifying and refining 2,7-naphthalenedisulfonic acid according to claim 1, characterized in that, The cooling and crystallization time is 10-14 hours.

5. The method for purifying and refining 2,7-naphthalenedisulfonic acid according to claim 1 or 4, characterized in that, The cooling and crystallization time is 12 hours.

Images