Refining method of sulfanilamide

Abstract

The invention provides a refining method of sulfanilamide, which comprises the following steps: (a) adding water into a container, heating, adding sulfanilamide and activated carbon, stirring and dissolving to obtain a mixed solution; (b) carrying out suction filtration on the mixed solution, and taking filtrate; and (c) adding an organic solvent and lower fatty acid into the filtrate, controlling the temperature of the filtrate to be reduced to 30-40 DEG C at the speed of 6-7 DEG C / h, carrying out suction filtration to obtain filter residues, washing and drying to obtain refined sulfanilamide. The precipitation purity of the sulfanilamide can be improved by strictly controlling the types and the dosage of the organic solvent and the lower fatty acid added into the filtrate and accurately controlling the cooling speed of the filtrate, so that the sulfanilamide with higher purity is obtained.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical product technology, specifically relating to a method for refining sulfonamides. Background Technology

[0002] Sulfonamides (molecular formula C6H8N2O2S, i.e., p-aminobenzenesulfonamide) are organic compounds with medicinal value and are the main raw materials for the synthesis of sulfonamide drugs. Due to their good antibacterial effects, mature technology, and readily available raw materials, sulfonamide drugs have maintained a certain market share after decades of clinical use. Therefore, the market demand for sulfonamides remains large, and the requirements for their purity are becoming increasingly stringent.

[0003] Chinese invention patent application number 201410083160.7 discloses a method for purifying sulfanilamide, which includes the following steps: (a) adding deionized water and calcium hydroxide to a reaction vessel, heating to 80-85°C, then adding crude sulfanilamide under stirring, and adjusting the pH to 9.5-10.5 to dissolve it completely; (b) adding activated carbon to the vessel, stirring at 80-85°C for 0.5-2 hours, and filtering to obtain a filtrate; (c) adding glacial acetic acid solution dropwise to the filtrate at 75-80°C, adjusting the pH to 5.1-5.4, allowing it to stand and precipitate, centrifuging to dehydrate and obtaining the filter residue; in step (c), after adding the glacial acetic acid solution, the filtrate is placed in an ice-water bath for cooling. The method for purifying sulfanilamide involves cooling the filtrate in an ice-water bath while adding glacial acetic acid solution and allowing it to settle. This allows the sulfanilamide to precipitate rapidly, eliminating interference from other components and improving the purity and yield of the sulfanilamide. However, this purification method requires an ice-water bath, making it difficult to implement industrially. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a method for purifying sulfonamides.

[0005] To address the aforementioned technical problems, the present invention provides a method for purifying sulfonamides, comprising the following steps: (a) Add water to the container, heat it up, add sulfonamide and activated carbon, stir to dissolve and obtain a mixed solution; (b) Filter the mixture and collect the filtrate; (c) Add organic solvent and lower fatty acid to the filtrate, control the filtrate to cool to 30-40°C at a rate of 6-7°C / h, filter the residue, wash and dry to obtain refined sulfonamide.

[0006] Ideally, in step (a), after adding water to the container, the temperature is raised to 60-75°C, and after adding sulfonamide and activated carbon, the temperature is further raised to 80-100°C and stirred for 0.5-2 hours.

[0007] Further, in step (a), the ratio of water, sulfonamide and activated carbon is 250~350ml: 600~800g: 3~8g.

[0008] Ideally, in step (b), the filtration is performed while the material is still hot.

[0009] Ideally, in step (c), the organic solvent is a mixture of one or more components selected from methanol, ethanol, and n-propanol.

[0010] Further, in step (c), the amount of organic solvent used is 3 to 5% of the mass of the filtrate.

[0011] Further, in step (c), the lower fatty acid is a mixture of one or more of formic acid, acetic acid, and propionic acid.

[0012] Furthermore, in step (c), the amount of the lower fatty acids used is 0.1 to 0.5% of the mass of the filtrate.

[0013] The present invention provides a method for refining sulfonamides. By strictly controlling the type and amount of organic solvents and lower fatty acids added to the filtrate, combined with precise control of the cooling rate of the filtrate, the purity of sulfonamide precipitation can be improved, thereby obtaining sulfonamides with higher purity. Attached Figure Description

[0014] Figure 1 This is a flowchart of the purification method of sulfonamides according to the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings. Example 1

[0016] This embodiment provides a method for purifying sulfonamides, such as... Figure 1 As shown, it includes the following steps: (a) Add 300ml of water to a container at room temperature, heat to 70°C, add 700g of sulfanilamide and 5g of activated carbon, continue to heat to 90°C, keep warm and stir for 1h to dissolve and obtain a mixed solution. (b) Filter the mixed solution while it is still hot and collect the filtrate (about 1000g). (c) The filtrate is pressed into the crystallization vessel, and 40g of methanol and 5g of acetic acid are added to the filtrate. The filtrate is cooled to 35°C at a rate of 6~7°C / h (in actual operation, the temperature fluctuates within this range, and this rate range has little impact on the quality of the product). The filter residue is collected by suction filtration, washed with water, centrifuged, and dried to obtain refined sulfonamide. The indicators of the product before and after purification are shown in Table 1. The yield is 92.6% and the purity is 99.5%.

[0017] Table 1. Data on sulfonamide before and after purification in Example 1

[0018] Example 2 This embodiment provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that in step (c), 40g of ethanol and 5g of formic acid are added; the yield is 92.8% and the purity is 99.7%. Example 2

[0019] This embodiment provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that in step (c), 40g of n-butanol and 5g of butyric acid are added; the yield is 93.5% and the purity is 99.8%. Example 3

[0020] This embodiment provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that in step (c), 30g of methanol and 3g of acetic acid are added; the yield is 92.7% and the purity is 99.6%. Example 4

[0021] This embodiment provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that in step (c), 50g of methanol and 1g of acetic acid are added; the yield is 92.4% and the purity is 99.5%.

[0022] Comparative Example 1 This example provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that methanol is not added in step (c); the yield is 90.4% and the purity is 98.0%.

[0023] Comparative Example 2 This example provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that acetic acid is not added in step (c); the yield is 90.7% and the purity is 98.2%.

[0024] Comparative Example 3 This example provides a method for purifying sulfonamides, which is basically the same as that in Example 1, except that in step (c), the filtrate is cooled at a rate of 8~10℃ / h; the yield is 92.0% and the purity is 98.8%.

[0025] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for purifying sulfonamides, characterized in that, Includes the following steps: (a) Add water to the container, heat it up, add sulfonamide and activated carbon, stir to dissolve and obtain a mixed solution; (b) Filter the mixture and collect the filtrate; (c) Add organic solvent and lower fatty acid to the filtrate, control the filtrate to cool to 30-40°C at a rate of 6-7°C / h, filter the residue, wash and dry to obtain refined sulfonamide.

2. The method for purifying sulfonamides according to claim 1, characterized in that: In step (a), water is added to the container and the temperature is raised to 60-75°C. After adding sulfonamide and activated carbon, the temperature is raised to 80-100°C and stirred for 0.5-2 hours.

3. The method for purifying sulfonamides according to claim 1 or 2, characterized in that: In step (a), the ratio of water, sulfonamide and activated carbon is 250~350ml: 600~800g: 3~8g.

4. The method for purifying sulfonamides according to claim 1, characterized in that: In step (b), the filter is carried out while the water is still hot.

5. The method for purifying sulfonamides according to claim 1, characterized in that: In step (c), the organic solvent is a mixture of one or more of methanol, ethanol and n-propanol.

6. The method for purifying sulfonamides according to claim 5, characterized in that: In step (c), the amount of organic solvent used is 3 to 5% of the mass of the filtrate.

7. The method for purifying sulfonamides according to claim 1 or 5, characterized in that: In step (c), the lower fatty acid is a mixture of one or more of formic acid, acetic acid and propionic acid.

8. The method for purifying sulfonamides according to claim 7, characterized in that: In step (c), the amount of the lower fatty acids used is 0.1 to 0.5% of the mass of the filtrate.

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