Preparation process of methanesulfonic acid

Abstract

The invention discloses a preparation process of methanesulfonic acid. The method comprises the following steps: mixing methyl mercaptan and sodium hypochlorite, and reacting to obtain a reaction solution; cooling the reaction liquid, and adding acid for acidification; and separating the methanesulfonic acid crude product to obtain a purified methanesulfonic acid product. The process provided by the invention starts from methyl mercaptan, selects sodium hypochlorite under an acidic condition as an oxidant, crosses dimethyl disulfide, improves the reaction conversion rate, reduces the preparation cost, shortens the reaction path, and is greener and more environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to a preparation process of methanesulfonic acid. Background Art

[0002] Methanesulfonic acid (MSA) is an organic acid with the chemical formula CH3SO3H. It is a colorless, transparent liquid with strong acidity and good water solubility. The acidity of methanesulfonic acid is stronger than acetic acid, but weaker than sulfuric acid. Due to its excellent chemical properties, methanesulfonic acid has been widely used in industry and laboratories. Methanesulfonic acid is widely used in many fields, including: 1) Methanesulfonic acid can be used as an acid catalyst to promote reactions in various chemical reactions; 2) Due to its excellent decontamination ability, methanesulfonic acid is often used in the formulation of detergents and descaling agents. 3) Methanesulfonates are used as electroplating solutions with good conductivity and stability. 4) In the pharmaceutical field, methanesulfonic acid is used to synthesize drugs and intermediates with excellent reaction selectivity. At present, the industrial synthesis methods all start with dimethyl disulfide, which is oxidized by oxidants such as chlorine or nitric acid to produce methanesulfonic acid. The use of chlorine and nitric acid is relatively dangerous, and the two processes produce more three wastes. The cost of dimethyl disulfide accounts for a high proportion of the production cost.

[0003] Therefore, it is necessary to develop a preparation method with a short reaction path, high atom economy, and more environmentally friendly. Summary of the invention

[0004] In view of the above-mentioned prior art, one of the purposes of the present invention is to provide a preparation process of methanesulfonic acid, which starts from methyl mercaptan, selects sodium hypochlorite under acidic conditions as an oxidant, skips dimethyl disulfide, improves the reaction conversion rate, reduces the preparation cost, shortens the reaction path, and is more environmentally friendly.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing methanesulfonic acid, the method comprising the following steps:

[0007] S1: methyl mercaptan and sodium hypochlorite are mixed and reacted to obtain a reaction solution;

[0008] S2: Cool the reaction solution and add acid to acidify;

[0009] S3: Separate the crude methanesulfonic acid to obtain a purified methanesulfonic acid product.

[0010] The inventors of the present invention have found in their research that the oxidizing power of +1-valent chlorine atoms is stronger than that of 0-valent chlorine atoms, and the oxidizing power under acidic conditions is stronger than that under alkaline conditions. In view of the above-mentioned prior art, the present invention provides a preparation process of methanesulfonic acid, which starts from methyl mercaptan, selects sodium hypochlorite under acidic conditions as an oxidant, skips dimethyl disulfide, improves the reaction conversion rate, reduces the preparation cost, shortens the reaction path, and is more environmentally friendly.

[0011] The scheme of the present invention relates to the following reaction:

[0012] Alkaline conditions:

[0013] CH3SH+3CIO - +OH - →CH3SO3 - +·3Cl - +H2O

[0014] Acidic conditions:

[0015] CH3SH+3CIO - →CH3SO3 - +3Cl - +H +

[0016] acidification

[0017] CH3SO3 - +H + →CH3SO3H

[0018] In one embodiment of the present invention, the molar ratio of methyl mercaptan to sodium hypochlorite in S1 is 1:3-1:7; preferably, the concentration of sodium hypochlorite is 10wt%-35wt%.

[0019] In one embodiment of the present invention, the reaction temperature in S1 is 30-100°C, preferably 50-80°C; and the reaction time is 2-5h.

[0020] In one embodiment of the present invention, the system 1 is maintained at ≤ pH ≤ 3 in S1; preferably, the pH value of the system is maintained by supplementing hydrochloric acid; preferably, the supplemented acid is a strong inorganic acid, preferably one or more of hydrochloric acid, sulfuric acid, and phosphoric acid.

[0021] In one embodiment of the present invention, an inert gas is passed into S1.

[0022] In one embodiment of the present invention, the acidification in S2 is performed with a strong inorganic acid, preferably one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; preferably, the molar ratio of methyl mercaptan to acid is 1:2-1:5.

[0023] In one embodiment of the present invention, S2 can be cooled to room temperature or other lower temperatures without affecting the effect.

[0024] In one embodiment of the present invention, the acidification temperature in S2 is 5-65°C, preferably 15-45°C.

[0025] In one embodiment of the present invention, the crude methanesulfonic acid is separated by distillation in S3.

[0026] In one embodiment of the present invention, methanesulfonic acid having a purity greater than 95 wt % is obtained in S3.

[0027] Another object of the present invention is to provide a methanesulfonic acid.

[0028] A methanesulfonic acid, wherein the methanesulfonic acid is prepared by the above-mentioned preparation method, and the purity of the methanesulfonic acid is greater than 95wt%.

[0029] Compared with the prior art, the positive effects of this application are:

[0030] The preparation method of methanesulfonic acid of the present invention has the advantages of short reaction path, simple operation, green environmental protection, yield>89%, methanesulfonic acid content in the product>98%, low production cost and the like. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the related listed items. The top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structure shown. They are relative concepts and may therefore be changed accordingly according to their different locations and different usage states.

[0033] Main raw material sources

[0034]

[0035] Main test methods

[0036] The test method used for the reaction solution in this scheme is liquid chromatography (HPLC), the detector is an ACQUITY UPLC differential refractometer (manufacturer: Waters), ethanol: ammonium oxalate aqueous solution (v:v) = 1:1 is used as the mobile phase, the mobile phase flow rate is 1.0 ml / min, the analysis is carried out at 40°C, and the methanesulfonic acid liquid phase residence time is 12.4 min.

[0037] In this scheme, the purity of the methanesulfonic acid product is determined by conventional acid value titration method, referring to the industry standard HG / T 5024-2016.

[0038] Example 1

[0039] S1: 1164 g (10 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added, and the temperature was raised to 30° C. and kept warm for 2 h. During this period, the pH in the autoclave was controlled to be 2 by adding hydrochloric acid.

[0040] S2: After the temperature in the reactor reaches room temperature, 115.2 g (33 wt%) of hydrochloric acid aqueous solution is added into the reactor through a horizontal flow pump. During this period, the reaction temperature is controlled at 35°C. After reacting for 2 hours, the reactor material is discharged into the distillation device;

[0041] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 35.72 g of methanesulfonic acid product (content 96.1 wt%) with a yield of 71.44%.

[0042] Example 2

[0043] S1: 873 g (20 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added, and the temperature was raised to 75° C. and kept for 3 h. During this period, the pH in the autoclave was controlled to be 2 by adding hydrochloric acid.

[0044] S2: After the temperature in the reactor reaches room temperature, 201.6 g (33 wt%) of hydrochloric acid aqueous solution is added into the reactor through a horizontal flow pump. During this period, the reaction temperature is controlled at 35°C. After reacting for 2 hours, the reactor material is discharged into the distillation device;

[0045] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 44.71 g of methanesulfonic acid product (content 98.3 wt%) with a yield of 89.43%.

[0046] Example 3

[0047] S1: 776.04 g (35 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added, and the temperature was raised to 100° C. and kept warm for 5 h. During this period, the pH in the autoclave was controlled to be 2 by adding hydrochloric acid.

[0048] S2: After the temperature in the reactor reaches room temperature, 288.04 g (33 wt%) of hydrochloric acid aqueous solution is added into the reactor through a horizontal flow pump. During this period, the reaction temperature is controlled at 35°C. After reacting for 2 hours, the reactor material is discharged into the distillation device;

[0049] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 44.27 g of methanesulfonic acid product (content 97.9 wt%) with a yield of 88.55%.

[0050] Example 4

[0051] S1: 873.05 g (20 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added, and the temperature was raised to 80° C. and kept for 3 h. During this period, the pH in the autoclave was controlled to be 2 by adding hydrochloric acid.

[0052] S2: After the temperature in the reactor reaches room temperature, 541.35 g (98 wt%) of sulfuric acid aqueous solution is added into the reactor through a horizontal flow pump. During this period, the reaction temperature is controlled at 35°C. After reacting for 2 hours, the reactor material is discharged into the distillation device;

[0053] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 41.55 g of methanesulfonic acid product (content 96.0 wt%) with a yield of 83.11%.

[0054] Example 5

[0055] S1: 873.05 g (20 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added, and the temperature was raised to 80° C. and kept for 3 h. During this period, the pH in the autoclave was controlled to be 3 by adding sulfuric acid.

[0056] S2: After the temperature in the reactor reaches room temperature, 541.35 g (99 wt%) of phosphoric acid aqueous solution is added into the reactor through a horizontal flow pump. During this period, the reaction temperature is controlled at 25°C. After reacting for 2 hours, the reactor material is discharged into the distillation device;

[0057] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 36.75 g of methanesulfonic acid product (content 95.5 wt%) with a yield of 73.49%.

[0058] Comparative Example 1

[0059] Compared with Example 2, the only difference is that no additional inorganic strong acid is added in the S1 process to control the pH of the system.

[0060] S1: 873.05 g (20 wt%) of sodium hypochlorite aqueous solution was added to a 5 L autoclave. After nitrogen was completely replaced in the system, 25 g of methyl mercaptan was added. The temperature was then raised to 80° C. and the reaction was kept at this temperature for 3 h. During this period, no additional hydrochloric acid was added to control the pH.

[0061] S2: 115.2 g (33 wt%) of hydrochloric acid aqueous solution was added into the reactor through a horizontal flow pump, during which the reaction temperature was controlled at 35°C. After reacting for 2 h, the reactor material was discharged into the distillation device;

[0062] S3: After the methanesulfonic acid content was determined by liquid chromatography, the components were removed in sequence by reduced pressure distillation at 0.5 kPa to obtain 29.56 g of methanesulfonic acid product (content 84 wt%) with a yield of 59.11%.

[0063] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing methanesulfonic acid, characterized in that, The method comprises the following steps: S1: methyl mercaptan and sodium hypochlorite are mixed and reacted to obtain a reaction solution; S2: Cool the reaction solution and add acid to acidify; S3: Separate the crude methanesulfonic acid to obtain a purified methanesulfonic acid product.

2. The preparation method according to claim 1, characterized in that: The molar ratio of methyl mercaptan to sodium hypochlorite in S1 is 1:3-1:7; Preferably, the sodium hypochlorite concentration is 10wt%-35wt%; And / or, the reaction temperature in S1 is 30-100°C, preferably 50-80°C; the reaction time is 2-5h; and / or, in S1, maintaining system 1≤pH≤3; Preferably, the pH of the system is maintained by supplementing acid; Preferably, the supplemented acid is a strong inorganic acid, preferably one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; And / or, an inert gas is introduced into S1.

3. The preparation method according to claim 1 or 2, characterized in that: Acidification in S2 uses a strong inorganic acid, preferably one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; Preferably, the molar ratio of methyl mercaptan to acid is 1:2-1:5; And / or, the acidification temperature in S2 is 5-65°C, preferably 15-45°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that In S3, the crude methanesulfonic acid is separated by distillation; And / or, methanesulfonic acid with a purity greater than 95 wt % is obtained in S3.

5. Methanesulfonic acid, which is prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The purity of the methanesulfonic acid is greater than 95 wt%.

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