CN1341779A

CN1341779A - Method for preparing hypophosphorous acid by using electrolytic method

Info

Publication number: CN1341779A
Application number: CN 01142024
Authority: CN
Inventors: 张宝贵; 张英喆; 程建忠; 万忠发; 万忠生
Original assignee: Tianjin Asahi Group Co Ltd; Nankai University
Current assignee: Tianjin Asahi Group Co Ltd; Nankai University
Priority date: 2001-09-07
Filing date: 2001-09-07
Publication date: 2002-03-27
Anticipated expiration: 2021-09-07
Also published as: CN1172028C

Abstract

本发明涉及次磷酸的制备,它是一种电解法制备次磷酸的方法。它是以碱金属次磷酸盐为原料,石墨作为阳极,以不锈钢作为阴极,应用电渗析槽电解水的方法进行电解;其中,原料室浓度为300－500g/L的次磷酸钠水溶液,阳极室中的初始溶液是浓度为5－15g/L的硫酸溶液,阴极室和其相邻的缓冲室中的初始溶液是浓度为5－15g/L的碱溶液,产品室和其相邻的缓冲室中的初始溶液是浓度为5－15gL的次磷酸溶液。本发明无废渣、废液产生,属清洁生产。The invention relates to the preparation of hypophosphorous acid, which is a method for preparing hypophosphorous acid by electrolysis. It uses alkali metal hypophosphite as the raw material, graphite as the anode, and stainless steel as the cathode, and uses the method of electrolyzing water in the electrodialysis cell for electrolysis; among them, the sodium hypophosphite aqueous solution with a concentration of 300-500g/L in the raw material chamber, and the anode chamber The initial solution in the chamber is a sulfuric acid solution with a concentration of 5-15g/L, the initial solution in the cathode chamber and its adjacent buffer chamber is an alkali solution with a concentration of 5-15g/L, and the product chamber and its adjacent buffer chamber The initial solution is a hypophosphorous acid solution with a concentration of 5-15gL. The invention produces no waste residue and waste liquid, and belongs to clean production.

Description

Method for preparing hypophosphorous acid by electrolysis method

Technical Field

The invention relates to preparation of hypophosphorous acid, in particular to a method for preparing hypophosphorous acid by an electrolytic method.

Background

Hypophosphorous acid is one of the widely used phosphorus chemical products. The traditional preparation method is that yellow phosphorus reacts with barium hydroxide, and then sulfuric acid is added to remove barium. However, because the solubility of barium hypophosphite is low, the concentration of the prepared hypophosphorous acid is not high, and industrial products need to be recrystallized and purified for many times, so that the application of the process is limited. In addition, an ion exchange resin method is adopted to prepare hypophosphorous acid, namely sodium hypophosphite is taken as a raw material, and strong acid type cation exchange resin is adopted to remove sodium to prepare dilute acid solution [ Arzoumanidis et al, US Patent, 4265866, 1981]. The method is complex and has high production cost, and is only suitable for small-batch production. In recent years, patents have been reported for the production of hypophosphorous acid by electrodialysis. Hypophosphorous acid is prepared by direct current electrolysis using noble metals such as platinum, iridium and ruthenium as the anode and stainless steel, graphite and platinum as the anode in 3-, 4-or 5-compartment electrodialysis cells [ Nobel, Fred I et al, U.S. patent 5480517, 5578182].

The above patent considers that no oxidation reaction of hypophosphite ions occurs at the anode, which is not possible as proved by our experiments-the nascent oxygen produced by electrolysis of the anode necessarily oxidizes part of the hypophosphite ions to phosphite or phosphate ions. In addition, noble metal electrodes are expensive, which limits large-scale industrial production.

Disclosure of Invention

The invention relates to an improvement of an electrolytic method for preparing hypophosphorous acid, which takes alkali metal hypophosphite as a raw material, adopts graphite with sufficient and cheap raw material sources as an anode, takes stainless steel as a cathode, and applies a method of electrolyzing water by a six-chamber electrodialysis cell to prepare hypophosphorous acid. The anion-cation exchange membrane used was purchased from Shanghai chemical plant. The structure composition of the six-chamber electrodialysis cell is shown in the attached figure 1.

The raw material chamber before electrolysis is placed with 500g/L sodium hypophosphite aqueous solution with the concentration of 300-500g/L, the initial solution in the anode chamber is dilute sulphuric acid solution with the concentration of 5-15g/L, the initial solution in the cathode chamber and the adjacent buffer chamber is dilute alkali metal hydroxide solution with the concentration of 5-15g/L, sodium hydroxide or potassium hydroxide is best selected, and the initial solution in the product chamber and the adjacent buffer chamber is dilute hypophosphorous acid solution with the concentration of 5-15 g/L.

After the electrodialysis groove is electrified with 10-15V direct current, the anions and the cations in the raw material chamber respectively move to the two poles, the cations move to the cathode, and the anions move to the anode. However, the anion exchange membrane allows primarily anions to pass through, so the primary chamber hypophosphite ion (H) enters the product chamber₂PO₂ ^-) (ii) a Also the cation exchange membrane allows mainly cations to pass through, so that mainly sodium ions (Na) enter the cathode compartment⁺)。

The main reaction generated at the graphite anode in the electrolysis process is the electrolysis of water into oxygen and hydrogen ions, and the reaction formula is as follows:

E⁰hydrogen ions produced by electrolysis at +0.401V pass from the anode chamber through the anode membrane into the product chamber where they combine with hypophosphite anions entering the chamber to produce a hypophosphorous acid product. During electrolysis, the cathode chamber mainly generates the reaction of generating hydrogen and hydroxide anions by electrolyzing water, and the reaction formula is as follows:

2H⁺+2e＝H₂E⁰the hydroxide ions from 0.0004V electrolysis combine with sodium ions entering the chamber to form sodium hydroxide.

Because hypophosphite ions are a strong reducing agent in the aqueous solution, after the anode electrolyzes water to release oxygen, the nascent oxygen oxidizes the hypophosphite ions into phosphite ions. To prevent oxidation of the hypophosphite ions, an anode membrane is applied adjacent the anode, separating the anode chamber from the product chamber. This is the key point in the production of hypophosphorous acid using this process.

In order to avoid the loss of current efficiency and improve the purity of the product, two positive membranes are added between the raw material chamber and the cathode chamber to form a buffer chamber, and two negative membranes are added between the raw material chamber and the product chamber to form a buffer chamber. The first buffer chamber is extremely advantageous for preventing hydroxide ions from entering the raw material chamber; also, the second buffer chamber is advantageous for preventing hydrogen ions from entering the raw material chamber and sodium ions from entering the product chamber.

In order to protect and prolong the service life of the anion-cation exchange membrane, the concentration of the hypophosphorous acid prepared by the method is about 100 g/L. At this time, sodium hydroxide is generated in an equivalent amount on the anode. The solution in the feed chamber and the buffer chamber may remain substantially stationary. When the concentration of sodium ions in the solution in the buffer chamber near the product chamber rises, the solution can be returned to the raw material chamber, and the raw material chamber is continuously supplemented with sodium hypophosphite to maintain the continuous reaction.

The invention is an improvement of the preparation of hypophosphorous acid by an electrolytic method, has simple process and low price, and is easy for large-scale industrial production. The invention has no waste slag and waste liquid, and belongs to clean production.

Drawings

FIG. 1 is a schematic diagram of the working principle of a six-compartment electrodialysis cell, 1-anode compartment, 2-product compartment, 3-buffer compartment, 4-feed compartment, 5-buffer compartment, 6-cathode compartment.

Detailed Description

Example 1

The anode material is graphite, and the electrode area is 40cm²And the cathode is a stainless steel electrode. The anion-cation exchange membrane is purchased from Shanghai chemical plant, and the membrane area used in electrolysis is 48cm². The volume of the solution per compartment of the six-compartment electrodialysis cell was 500 ml. The initial solution in the anode chamber before electrolysis is 10g/L sulfuric acid, the raw material chamber is 500g/L sodium hypophosphite, the cathode chamber and the adjacent buffer chamber are both 10g/L sodium hydroxide, and the product chamber and the adjacent buffer chamber are both 10g/L hypophosphorous acid.

The working voltage is 10-15V, the concentration of hypophosphorous acid in the product chamber after continuous electrolysis for 6H is 69.3g/L under the condition of keeping the current at 3.0A, and the current efficiency at the moment is calculated to be 80.9%.

The concentrations of hypophosphorous acid solution in the product compartment after 6H electrolysis under different current conditions are shown in Table 1.

TABLE 1 product concentration and Current efficiency at different operating currents

Current (A) hypophosphorous acid concentration (g/L) Current efficiency (%)

1.0 20.2 70.7

2.0 42.7 73.8

3.0 69.3 80.9

4.0 84.1 73.5

5.0 103.1 71.4

Example 2

The initial operating conditions of the six-compartment electrodialysis cell were the same as in example 1.

The electrolysis time was 30H at an operating current of 3A, the concentration of hypophosphorous acid in the product compartment was 178.6g/L, and the current efficiency was 55.3%.

The concentrationof the hypophosphorous acid solution in the product compartment obtained at different electrolysis times is shown in Table 2.

TABLE 2 product concentration and Current efficiency at different electrolysis times

Electrolysis time (H) hypophosphorous acid concentration (g/L) Current efficiency (%)

6 69.3 80.9

12 101.9 77.4

18 136.1 68.3

24 169.1 60.5

30 178.6 55.3

Example 3

When the working current is 3A, the electrolysis time is 30H, and the content of sodium ions and sulfate ions in the product chamber is 50ug/L and 0.80g/L respectively.

The resulting sodium and sulphate ion contents of the product compartment at different electrolysis times are shown in table 3.

TABLE 3 sodium and sulfate ion content of hypophosphorous acid product as a function of time

Electrolysis time (H) sodium ion content (ug/L) sulfate content (g/L)

6 5 0.11

12 13 0.36

18 25 0.48

24 40 0.76

30 50 0.80

Claims

1. A method for preparing hypophosphorous acid by an electrolytic method is characterized in that alkali metal hypophosphites are used as raw materials, graphite is used as an anode, stainless steel is used as a cathode, and a method of electrolyzing water by an electrodialysis cell is used for electrolysis; wherein the raw material chamber is provided with 500g/L sodium hypophosphite aqueous solution with the concentration of 300-15 g/L, the initial solution in the anode chamber is 5-15g/L sulfuric acid solution, the initial solution in the cathode chamber and the adjacent buffer chamber is 5-15g/L alkali solution, and the initial solution in the product chamber and the adjacent buffer chamber is 5-15g/L hypophosphorous acid solution.

2. The electrolytic process for producing hypophosphorous acid according to claim 1, wherein said electrodialysis cell is a six-compartment electrodialysis cell.

3. The electrolytic process for producing hypophosphorous acid according to claim 1, wherein said electrolytic operation voltage is 10 to 15V, the operation current is 1 to 5A, and the electrolysis time is 6 to 30H.

4. The electrolytic process for producing hypophosphorous acid according to claim 1 or 3, characterized in that said electrolytic operation current is 3A.

5. The electrolytic process for producing hypophosphorous acid according to claim 1, wherein said alkaline solution is sodium hydroxide or potassium hydroxide.

6. The electrolytic process for producing hypophosphorous acid according to claim 1, characterized in that said hypophosphite is sodium hypophosphite.