Industrial salicylic acid refining and purifying method
By mixing industrial salicylic acid with pure water and adding reducing agent, performing reduction reaction and filtration, the problems of low purity, deep chromaticity and high ash content in the prior art are solved, and efficient purification effect is achieved , suitable for industrial production.
Patent Information
- Application Number
- CN202411443387.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2025-01-03
AI Technical Summary
In the existing industrial salicylic acid preparation process, the product has low purity, deep chromaticity and high ash content, making it difficult to effectively remove impurities.
The colored substance is removed by mixing industrial salicylic acid with pure water and heating, and the water-soluble inorganic salt is removed by heating, so as to achieve purification.
It significantly improves the purity of salicylic acid and reduces the color and ash content, and is simple in process and suitable for industrial production.
Smart Images
Figure CN119241352A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of salicylic acid preparation, and in particular to a method for refining and purifying industrial salicylic acid. Background Art
[0002] Salicylic acid, also known as o-hydroxybenzoic acid and 2-hydroxybenzoic acid, is a raw material widely used in the pharmaceutical and chemical industries. Salicylic acid can be divided into industrial-grade salicylic acid, sublimation-grade salicylic acid and pharmaceutical-grade salicylic acid according to different grades. Industrial-grade salicylic acid is also called industrial salicylic acid. The more common preparation method is to use phenol and liquid alkali as raw materials to react to generate sodium phenol, which is then dried and reacted with carbon dioxide to generate sodium salicylate, which is then dissolved in water to obtain a sodium salicylate solution, which is then acidified, centrifuged and dried to obtain. At present, the industrial salicylic acid prepared by the above process generally has low purity, dark appearance color and high ash content. Summary of the invention
[0003] In order to solve the above technical problems, the present invention provides a method for refining and purifying industrial salicylic acid, which specifically comprises the following steps: S1: Add industrial salicylic acid into pure water, stir and heat to 55-85℃; S2: Add reducing agent and keep stirring for 20-40 minutes; S3: After cooling to 35-45°C, filter, centrifuge and dry to obtain refined salicylic acid.
[0004] Preferably, in S1, the mass ratio of industrial salicylic acid to pure water is 1:1-5.
[0005] Preferably, in S2, the adding ratio of the reducing agent is 0.05-0.2% of the industrial salicylic acid.
[0006] Preferably, in S2, the reducing agent is sodium dithionite.
[0007] The industrial salicylic acid refining and purification method of the present invention achieves the purpose of reducing chromaticity by adding a reducing agent to react with colored substances (mainly benzoquinone produced by oxidizing phenol) in the industrial salicylic acid, and removes water-soluble inorganic salts (mainly sodium sulfate produced in the acid precipitation stage) in the industrial salicylic acid by mixing with pure water and filtering, thereby achieving the purpose of reducing ash content. The method refines and purifies the product by removing impurities such as colored substances and water-soluble inorganic salts in the industrial salicylic acid.
[0008] The industrial salicylic acid refining and purification method of the present invention can significantly improve the purity of the product and significantly reduce the chromaticity and ash content of the product. The method has the characteristics of significant effect, simple process, strong practicability, etc., and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 The process flow chart of the method for refining and purifying industrial salicylic acid described in the present invention. Example
[0010] The present invention is further described below in conjunction with embodiments, comparative examples and accompanying drawings, but the implementation of the present invention is not limited thereto. Example 1
[0011] Light pink salicylic acid with a purity of 99.1% and an ash content of 0.25% was mixed with pure water in a mass ratio of 1:2, stirred and heated to 55°C, sodium dithionite with a mass content of 0.2% of salicylic acid was added and stirred for 40 minutes, and then filtered, centrifuged and dried after cooling to 35°C to obtain off-white salicylic acid with a purity of 99.6% and an ash content of 0.04%. Example 2
[0012] Light pink salicylic acid with a purity of 99.1% and an ash content of 0.25% was mixed with pure water in a mass ratio of 1:5, stirred and heated to 85°C, sodium dithionite with a mass ratio of 0.1% of salicylic acid was added and stirred for 30 minutes, and then filtered, centrifuged and dried after cooling to 40°C to obtain off-white salicylic acid with a purity of 99.7% and an ash content of 0.02%. Example 3
[0013] Light pink salicylic acid with a purity of 99.1% and an ash content of 0.25% was mixed with pure water in a mass ratio of 1:1, stirred and heated to 70°C, sodium dithionite with a mass ratio of 0.05% of salicylic acid was added and stirred for 20 minutes, and then filtered, centrifuged and dried after cooling to 45°C to obtain off-white salicylic acid with a purity of 99.5% and an ash content of 0.05%.
[0014] Comparative Example Light pink salicylic acid with a purity of 99.1% and an ash content of 0.25% was mixed with pure water in a mass ratio of 2:1, stirred and heated to 45°C, sodium dithionite with a mass content of 0.02% of salicylic acid was added and stirred for 10 minutes, and then filtered, centrifuged and dried after cooling to 35°C to obtain light pink salicylic acid with a purity of 99.2% and an ash content of 0.18%.
Claims
1. A method for refining and purifying industrial salicylic acid, characterized in that The method steps are as follows: S1: Add industrial salicylic acid into pure water, stir and heat to 55-85℃; S2: Add reducing agent and keep stirring for 20-40 minutes; S3: After cooling to 35-45°C, filter, centrifuge and dry to obtain refined salicylic acid.
2. The method for refining and purifying industrial salicylic acid according to claim 1, characterized in that: The mass ratio of industrial salicylic acid to pure water is 1:1~5.
3. The method for refining and purifying industrial salicylic acid according to claim 1, characterized in that: The adding ratio of the reducing agent is 0.05-0.2% of the industrial salicylic acid.
4. The method for refining and purifying industrial salicylic acid according to claim 1 or 3, characterized in that: The reducing agent is sodium dithionite.