A method for preparing methanesulfonic acid with low sulfate residue

Abstract

This invention discloses a method for preparing methanesulfonic acid with low sulfate residue. The method includes the following steps: in a batch reactor, using dimethyl disulfide with a dimethyl polysulfide content of less than 350 ppm, preferably less than 220 ppm, as raw material, the reaction is carried out in the presence of a catalyst and an oxidant; after the reaction is terminated, the reaction solution is post-treated to obtain methanesulfonic acid. This invention solves the problem of high sulfate content in the product methanesulfonic acid by controlling the dimethyl polysulfide content in the raw material, resulting in a higher quality product and a significant reduction in the content of heavy component impurities. This not only improves the product yield but also simplifies the deweighting process or reduces energy consumption.

Description

Technical Field

[0001] This invention relates to a preparation method, and more particularly to a method for preparing methanesulfonic acid with low sulfate residue. Background Technology

[0002] Methanesulfonic acid, as a strong organic acid, has a broad market demand in industrial cleaning, electronic plating, and organic synthesis. The current mainstream production process for methanesulfonic acid uses dimethyl disulfide as a starting material, oxidized by strong oxidizing agents such as nitric acid. Research has found that this oxidation process generates a certain amount of sulfate and heavy component impurities. After removing nitric acid and other components from the oxidation product, further purification is required to remove sulfate and heavy component impurities. This process is not only energy-intensive, but also inevitably results in some sulfate being distilled off with the product, leading to a residual sulfate content in the product that is generally greater than 50 ppm, and even reaches several thousand ppm, significantly affecting product quality. Especially in the electronic plating field, the presence of a large amount of sulfate makes it easier to generate plating slag during the plating process; and in higher-end silicon wafer plating solutions, repeated purification is necessary to meet usage requirements, posing significant challenges to industrial applications.

[0003] Therefore, it is necessary to develop new process conditions to minimize the content of sulfate and heavy component impurities in methanesulfonic acid. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for preparing methanesulfonic acid with low sulfate residue. By controlling the content of dimethyl polysulfides in the raw materials, this invention solves the problem of high sulfate content in the methanesulfonic acid product, resulting in a higher quality product. Furthermore, the content of heavy component impurities is significantly reduced, not only improving product yield but also simplifying the deweighting process or reducing energy consumption.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing methanesulfonic acid with low sulfate residue, characterized by comprising the following steps:

[0007] In a batch reactor, dimethyl disulfide with a content of less than 350 ppm, preferably less than 220 ppm, is used as raw material and reacted in the presence of a catalyst and an oxidant. After the reaction is terminated, the reaction solution is post-treated to obtain methanesulfonic acid.

[0008] Through continuous research, the inventors discovered that dimethyl disulfide typically contains a certain amount of dimethyl polysulfide due to limitations in raw material preparation processes. Surprisingly, by controlling the content of dimethyl polysulfide, the present invention unexpectedly found that the sulfate content in the product tends to decrease. In particular, when the dimethyl polysulfide content is below 350 ppm, it has a significant advantage in reducing the sulfate content in the product. It is speculated that the presence of dimethyl polysulfide in the reaction system is a key factor in promoting the free radical reaction to generate sulfate. Furthermore, the research found that when the dimethyl polysulfide content is controlled below 220 ppm, the amount of heavy components generated in the system is also significantly reduced, and the product yield is improved, thus completing the present invention.

[0009] The method for controlling the content of dimethyl polysulfides in the raw material dimethyl disulfide can be conventional distillation separation or other raw material deep purification methods, and is not intended to limit the present invention in any way.

[0010] As a preferred embodiment of the present invention, the catalyst is one or more of nitric acid, nitric oxide, and nitrogen dioxide.

[0011] As a preferred embodiment of the present invention, the catalyst content is 0.01-0.50% of the weight of dimethyl disulfide.

[0012] In a preferred embodiment of the present invention, the oxidant is oxygen or air.

[0013] As a preferred embodiment of the present invention, the content of the oxidant is 3-15 times based on the molar amount of dimethyl disulfide.

[0014] As a preferred embodiment of the present invention, the dimethyl polysulfide includes at least one of dimethyl trisulfide and dimethyl tetrasulfide.

[0015] As a preferred embodiment of the present invention, the reaction temperature is 50-180℃ and the reaction gauge pressure is 0.1-1.0MPa.

[0016] As a preferred embodiment of the present invention, the reaction is carried out in the presence of an optional solvent; the amount of solvent used is, for example, 3-10 times the mass of dimethyl disulfide.

[0017] Preferably, the solvent is one or more of water, ethylene glycol, propylene glycol, N,N-dimethylformamide, and acetonitrile.

[0018] As a preferred embodiment of the present invention, the post-treatment of the reaction solution includes purification to remove light components and optionally purification to remove heavy components; wherein, the purification to remove light components adopts the following conditions: 20-120℃, 10KPa-0.1MPa;

[0019] The refining and deweighting process is carried out under the following conditions: 120-230℃, 10Pa-0.1MPa.

[0020] The preparation method of this invention can produce high-quality methanesulfonic acid with significantly reduced sulfate content, preferably below 1 ppm, which is more suitable for applications in high-precision industries such as electronic electroplating. In addition, the low content of heavy components in the product makes it possible to simplify the subsequent deweighting process, and has application advantages in saving production costs and reducing energy consumption. At the same time, the stability of the product is greatly improved. After being stored at 60°C for 1 month, the color number of the product increases by less than 20%. Detailed Implementation

[0021] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0022] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention can be purchased commercially.

[0023] The main testing methods used in this invention are:

[0024] The content of dimethyl polysulfide was detected by gas chromatography using a polyethylene glycol column. Dimethyl disulfide was directly injected and vaporized, flowing through the column for component separation. The components were then detected by a detector, and the peak values ​​were quantified using the calibration area normalization method. Specific chromatographic analysis conditions are as follows:

[0025] Table 1. Gas Chromatography Analysis Conditions

[0026]

[0027] The methanesulfonic acid content was determined by acid-base neutralization titration: using phenolphthalein as an indicator, the solution was neutralized and titrated to neutral with a standard sodium hydroxide solution (1 mol / L), and the methanesulfonic acid content was calculated based on the amount of standard sodium hydroxide solution used.

[0028] Sulfate ions were determined using high-performance ion chromatography: the methanesulfonic acid sample was diluted 5-10 times with deionized water and then tested using ion chromatography.

[0029] Color codes are tested in accordance with the specifications in GB / T 1664.

[0030]

Example 1

[0031] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 35 ppm), 68% nitric acid, and water were sequentially added to a reactor, ensuring that the purity of the added nitric acid was 0.2% of the dimethyl disulfide and the amount of water was 5 times the mass of the dimethyl disulfide. Then, oxygen was introduced in quantities 5 times the molar amount of dimethyl disulfide. The reactor was sealed and the reaction was carried out at 120°C and 0.3 MPa for 1 hour. After the reaction was complete, a sample was taken to test the conversion rate of dimethyl disulfide, which was greater than 99%. The reaction solution was sent to a light component removal tower to remove light components such as nitric acid and water at 100°C and 0.05 MPa. A 99.9% pure methanesulfonic acid product was collected from the bottom of the tower, with sulfate content less than 1 ppm and a product yield of 99.2%. The product was stored at 60°C for 1 month, and the APHA color value increased by 9.

[0032]

Example 2

[0033] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 107 ppm), 68% nitric acid, and water were sequentially added to a reactor, ensuring that the purity of the added nitric acid was 0.3% of the dimethyl disulfide and the amount of water was 3 times the mass of the dimethyl disulfide. Then, oxygen was introduced in quantities 9 times the molar amount of dimethyl disulfide. The reactor was sealed and the reaction was carried out at 140°C and 0.8 MPa for 5 hours. After the reaction was completed, a sample was taken, and the conversion rate of dimethyl disulfide was found to be greater than 99%. The reaction solution was sent to a light component removal tower, where nitric acid, water, and other light components were removed at 80°C and 0.03 MPa. A 99.5% pure methanesulfonic acid product was collected from the bottom of the tower, containing 4 ppm of sulfate, with a product yield of 98.9%. The product was stored at 60°C for one month, and the APHA color value increased by 15.

[0034]

Example 3

[0035] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 219 ppm) and water were sequentially added to a reactor, ensuring the water addition was 5 times the mass of dimethyl disulfide. Then, oxygen (7 times the molar amount of dimethyl disulfide) and nitrogen dioxide (0.45% of the mass of dimethyl disulfide) were introduced. The reactor was sealed and the reaction was carried out at 100°C and 0.7 MPa for 6 hours. After the reaction was complete, a sample was taken, and the conversion rate of dimethyl disulfide was found to be greater than 99%. The reaction solution was sent to a light component removal tower to remove nitric acid, water, and other light components at 120°C and atmospheric pressure. The residue collected at the bottom of the tower yielded a methanesulfonic acid product with a purity of 99.3%, containing 5 ppm sulfate, and a product yield of 98.7%. The product was stored at 60°C for one month, and the APHA color value increased by 13.

[0036]

Example 4

[0037] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 235 ppm), 68% nitric acid, and water were sequentially added to a reactor, ensuring that the purity of the added nitric acid was 0.1% of the mass of dimethyl disulfide, and the amount of water added was 7 times the mass of dimethyl disulfide. Then, air with a molar volume 15 times that of dimethyl disulfide was introduced. The reactor was sealed and the reaction was carried out at 120°C and 0.8 MPa for 10 hours. After the reaction was completed, a sample was taken, and the conversion rate of dimethyl disulfide was greater than 99%. The reaction solution was sent to a light component removal tower, where nitric acid, water, and other light components were removed at 80°C and 0.2 MPa. A methanesulfonic acid product with a purity of 98.3% was collected from the bottom of the tower, containing 7 ppm of sulfate, with a product yield of 97.5%. The product was stored at 60°C for one month, and the APHA color value increased by 19.

[0038]

Example 5

[0039] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 345 ppm), 68% nitric acid, and water were sequentially added to a reactor, ensuring that the purity of the added nitric acid was 0.1% of the mass of dimethyl disulfide, and the amount of water added was 7 times the mass of dimethyl disulfide. Then, air with a molar volume 15 times that of dimethyl disulfide was introduced. The reactor was sealed and the reaction was carried out at 120°C and 0.8 MPa for 10 hours. After the reaction was completed, a sample was taken, and the conversion rate of dimethyl disulfide was greater than 99%. The reaction solution was sent to a light component removal tower, where nitric acid, water, and other light components were removed at 80°C and 0.2 MPa. A methanesulfonic acid product with a purity of 97.9% was collected from the bottom of the tower, containing 9 ppm of sulfate, with a product yield of 96.5%. The product was stored at 60°C for one month, and the APHA color value increased by 26.

[0040] Comparative Example 1

[0041] Dimethyl disulfide (total of dimethyl trisulfide and dimethyl tetrasulfide 430 ppm), 68% nitric acid, and water were sequentially added to a reactor, ensuring that the purity of the added nitric acid was 0.2% of the dimethyl disulfide and the amount of water was 5 times the mass of the dimethyl disulfide. Then, oxygen was introduced in quantities 5 times the molar amount of dimethyl disulfide. The reactor was sealed and the reaction was carried out at 120°C and 0.3 MPa for 1 hour. After the reaction was complete, a sample was taken to test the conversion rate of dimethyl disulfide, which was greater than 99%. The reaction solution was sent to a light component removal tower to remove light components such as nitric acid and water at 100°C and 0.05 MPa. The bottom liquid was then sent to a heavy component removal tower for purification by distillation at 170°C and 300 Pa, yielding a methanesulfonic acid product with a purity of 97.2% and a sulfate content of 4300 ppm, with a product yield of 86.7%. The product was stored at 60°C for 1 month, and the APHA color value increased by 589.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing methanesulfonic acid, characterized in that, Includes the following steps: In a batch reactor, dimethyl disulfide with a dimethyl polysulfide content of less than 350 ppm was used as raw material and reacted in the presence of a catalyst and an oxidant. After the reaction was terminated, the reaction solution was post-treated to obtain methanesulfonic acid. The catalyst is one or more of nitric acid, nitric oxide, and nitrogen dioxide; the oxidant is oxygen or air.

2. The method for preparing methanesulfonic acid according to claim 1, characterized in that, The reaction was carried out using dimethyl disulfide with a dimethyl polysulfide content of less than 220 ppm as a raw material.

3. The method for preparing methanesulfonic acid according to claim 1, characterized in that, The catalyst content is 0.01-0.50% of the weight of dimethyl disulfide.

4. The method for preparing methanesulfonic acid according to claim 1, characterized in that, The oxidant content is 3-15 times the molar amount of dimethyl disulfide.

5. The method for preparing methanesulfonic acid according to any one of claims 1-4, characterized in that, The dimethyl polysulfide includes at least one of dimethyl trisulfide and dimethyl tetrasulfide.

6. The method for preparing methanesulfonic acid according to any one of claims 1-4, characterized in that, The reaction temperature is 50-180℃, and the reaction gauge pressure is 0.1-1.0MPa.

7. The method for preparing methanesulfonic acid according to any one of claims 1-4, characterized in that, The reaction is carried out in the presence of an optional solvent.

8. The method for preparing methanesulfonic acid according to claim 7, characterized in that, The solvent is one or more of water, ethylene glycol, propylene glycol, N,N-dimethylformamide, and acetonitrile.

9. The method for preparing methanesulfonic acid according to any one of claims 1-4, characterized in that, The post-treatment of the reaction solution includes purification to remove light components and, optionally, purification to remove heavy components; wherein, the purification to remove light components is carried out under the following conditions: 20-120℃, 10KPa-0.1MPa; The refining and deweighting process is carried out under the following conditions: 120-230℃, 10Pa-0.1MPa.

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