Method for synthesizing benzyl arsonic acid through acidification of arsenic acid

Abstract

The invention discloses a method for synthesizing benzyl arsonic acid by acidizing arsenic acid. The method comprises the following steps: preparing arsenic acid, preparing sodium arsenite, adding benzyl chloride into the sodium arsenite to react to generate benzyl arsonic acid sodium, and standing for layering; acidizing arsenic acid until the pH value is 1-3 to generate benzyl arsonic acid and sodium arsenate; and adding a transforming agent into the sodium arsenate, and reacting for 2 hours to obtain a sodium arsenite solution which is recycled as a raw material. According to the method, the arsenic acid is used for replacing sulfuric acid to acidify the sodium benzyl arsonic acid to generate the benzyl arsonic acid, sulfate radicals are not introduced, and no sodium sulfate waste salt is generated; sodium arsenate is converted into sodium arsenite to be recycled as a raw material, so that cyclic utilization of sodium and arsenic is realized, and the method has remarkable environmental protection and resource utilization values.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resource utilization of arsenic trioxide, and particularly relates to a method for synthesizing benzyl arsine acid by using arsenic acid acidification. BACKGROUND

[0002] The existing production process of benzyl arsine acid is as follows: arsenic trioxide is reacted with sodium hydroxide to generate sodium arsenite, and then the sodium arsenite is reacted with benzyl chloride to generate sodium benzyl arsine, and then the sodium benzyl arsine is reacted with sulfuric acid or hydrochloric acid to generate benzyl arsine acid. In the process, the sulfuric acid acidification introduces sulfate, generates waste sodium sulfate salt which is difficult to handle, increases the amount of waste residue, and causes waste of arsenic resources. SUMMARY

[0003] In view of the deficiencies of the prior art method, the application provides a method for synthesizing benzyl arsine acid by using arsenic acid acidification, which uses arsenic trioxide as a raw material, replaces sulfuric acid with arsenic acid for acidification, and reduces and converts sodium arsenate into sodium arsenite for recycling, so as to realize efficient production of benzyl arsine acid.

[0004] The application adopts the following technical scheme: A method for synthesizing benzyl arsine acid by using arsenic acid acidification, comprising the following steps: (1) preparing arsenic acid: mixing arsenic trioxide with an oxidizing agent at a mass ratio of 1:1-1.5, and reacting at 40-100 DEG C for 2 h to generate arsenic acid; (2) preparing sodium arsenite: mixing arsenic trioxide with water at a ratio of 1:2.2, gradually adding sodium hydroxide, and keeping the temperature at 80-90 DEG C to obtain sodium arsenite; (3) adding benzyl chloride to the sodium arsenite in step (2) to react to generate sodium benzyl arsine, and then standing and separating; (4) adding the arsenic acid in step (1) to the middle layer in step (3) to acidify to pH=1-3 to generate benzyl arsine acid and sodium arsenate; (5) adding a conversion agent to the sodium arsenate in step (4) to react for 2 h to obtain a sodium arsenite solution which is recycled to step (2); (6) repeating steps (1), (3), (4) and (5) to realize continuous production of benzyl arsine acid.

[0005] Further, the oxidizing agent is 20-35% hydrogen peroxide.

[0006] Further, the mass ratio of the benzyl chloride to the sodium arsenite in the application is 0.8-0.85:1, and the reaction is carried out at 80-105 DEG C for 6-10 h.

[0007] Further, the conversion agent is potassium iodide and hydrogen.

[0008] The main chemical reactions of the application are as follows: Preparation of arsenic acid: Na3AsO4 + H2 = Na3AsO3 + H2O (1) (2) Na3AsO3 + C7H7Cl = C7H7AsO3 Na2 + NaCl (3) The formation of benzylarsonic acid: 3C7H7AsO3 Na2 + 2H3AsO4 = 3C7H7AsO3H2 + 2Na3AsO4 (4) Reduction of sodium arsenate: Na3AsO4 + H2 → Na3AsO3 + H2O (5) The present invention has the following advantages: This invention generates benzylarsine by replacing sulfuric acid with arsenic acid to acidify sodium benzylarsine, without introducing sulfate ions or generating sodium sulfate waste salt; and converts sodium arsenate into sodium arsenite for recycling, realizing the recycling of sodium and arsenic, which has significant environmental protection and resource utilization value. Attached Figure Description

[0009] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0010] The invention will now be further described in conjunction with the accompanying drawings and embodiments. Example 1

[0011] like Figure 1 As shown, a method for synthesizing benzylarsonic acid by arsenic acid acidification includes the following steps: (1) Preparation of arsenic acid: Arsenic trioxide and oxidant are mixed at a mass ratio of 1:1 and reacted at 40°C for 2 hours to generate arsenic acid; (2) Preparation of sodium arsenite: Arsenic trioxide and water are mixed at a mass ratio of 1:2.2, sodium hydroxide is gradually added, and the temperature is kept at 80℃ to obtain sodium arsenite; (3) Add benzyl chloride to the sodium arsenite in step (2) at a mass ratio of 0.8:1 to generate sodium benzylarsinate. React at 80°C for 6 hours and allow to stand to separate into layers. (4) Add the arsenic acid from step (1) to the middle layer of the layering in step (3) to acidify to pH=1 to generate benzylarsine and sodium arsenate, then centrifuge and filter. (5) Return the sodium arsenate solution from step (4) to the reactor, add potassium iodide under acidic conditions, and pass hydrogen gas through to react for 2 hours to obtain sodium arsenite solution to be recycled to step (2). (6) Repeat steps (1), (3), (4) and (5) to achieve continuous production of benzylarsine.

[0012] The purity of the obtained benzylarsonic acid was found to be 60%. Example 2

[0013] like Figure 1 As shown, a method for synthesizing benzylarsonic acid by arsenic acid acidification includes the following steps: (1) Preparation of arsenic acid: Arsenic trioxide and oxidant are mixed at a mass ratio of 1:1.2 and reacted at 100℃ for 2h to generate arsenic acid; (2) Preparation of sodium arsenite: Arsenic trioxide and water were mixed at a ratio of 1:2.2, and sodium hydroxide was gradually added while maintaining the temperature at 90℃ to obtain sodium arsenite; (3) Add benzyl chloride to the sodium arsenite in step (2) at a mass ratio of 0.85:1 to generate sodium benzylarsine. React at 105°C for 10 h and allow to stand to separate into layers. (4) Add the arsenic acid from step (1) to the middle layer of the layering in step (3) to acidify to pH=3 to generate benzylarsine and sodium arsenate, then centrifuge and filter. (5) Return the sodium arsenate solution from step (4) to the reactor, add potassium iodide under acidic conditions and pass hydrogen gas through to react for 2 hours to obtain sodium arsenite solution and recycle it to step (2). (6) Repeat steps (1), (3), (4) and (5) to achieve continuous production of benzylarsine.

[0014] The purity of the obtained benzylarsonic acid was tested to be 59%.

[0015] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for synthesizing benzylarsine by arsenic acid acidification, characterized in that: Includes the following steps: Preparation of arsenic acid: Arsenic trioxide and oxidant are mixed at a mass ratio of 1:1~1.5 and reacted at 40~100℃ for 2 hours to produce arsenic acid; Preparation of sodium arsenite: Arsenic trioxide and water are mixed at a ratio of 1:2.2, and sodium hydroxide is gradually added while maintaining the temperature at 80~90℃ to obtain sodium arsenite; Add benzyl chloride to the sodium arsenite from step (2) to react and generate sodium benzylarsine, then let it stand to separate into layers; In step (3), arsenic acid from step (1) is added to the middle layer of the layered structure and acidified to pH 1-3 to generate benzylarsine and sodium arsenate; In step (4), a conversion agent is added to the sodium arsenate and the reaction is carried out for 2 hours to obtain a sodium arsenite solution which is then recycled to step (2). (6) Repeat steps (1), (3), (4) and (5) to achieve continuous production of benzylarsine.

2. The method according to claim 1, characterized in that: The oxidant is 20-35% hydrogen peroxide.

3. The method according to claim 1, characterized in that: In step (3), the mass ratio of benzyl chloride to sodium arsenite is 0.8~0.85:1, and the reaction is carried out at 80~105℃ for 6~10h.

4. The method according to any one of claims 1 to 3, characterized in that: The conversion agent mentioned in step (5) is potassium iodide added and hydrogen gas passed through.

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