Bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite

Abstract

The utility model discloses a bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite. The bipolar membrane electrodialysis device comprises a pure water deoxidation device, a sodium hypophosphite preparation tank, an acid liquid tank, an alkali liquid tank, a salt liquid tank, an electrode liquid tank and an electrodialysis membrane stack, the pure water deoxidizing device is respectively communicated with the sodium hypophosphite preparation tank, the acid liquor tank and the alkali liquor tank through deoxidized water liquid inlet pipes, the sodium hypophosphite preparation tank is communicated with the salt liquor tank, and liquid outlets of the acid liquor tank, the alkali liquor tank, the salt liquor tank and the electrode liquor tank are respectively communicated with corresponding liquid inlets of the electrodialysis membrane stack; a liquid outlet of the electrodialysis membrane stack is respectively communicated with the corresponding acid liquid tank, alkali liquid tank, salt liquid tank and polar liquid tank; the device has the characteristic of improving the preparation purity of hypophosphorous acid.

Description

Technical Field

[0001] The invention relates to the field of fine chemical production, and in particular to a bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite. Background Art

[0002] Hypophosphorous acid is an important fine chemical product, mainly used as a reducing agent for chemical plating, to prevent phosphoric acid resin from changing color, and as a catalyst and refrigerant for esterification reactions. Hypophosphorous acid is a colorless oily liquid or a deliquescent crystal, easily soluble in water, ethanol and ether. When heated to 130°C, it undergoes disproportionation to form phosphorous acid and phosphine (phosphine). Hypophosphorous acid has strong reducing properties and is easily oxidized to phosphorous acid when in contact with air.

[0003] The preparation methods of hypophosphorous acid mainly include ion exchange method and electrodialysis method. The ion exchange method uses sodium hypophosphite as raw material and adopts cation exchange resin to remove sodium. However, the resin consumption of this method is large and frequent resin regeneration produces a large amount of high-salt wastewater. The hydrochloric acid introduced during the resin regeneration process may cause residual chloride ions, affecting the purity of the produced hypophosphorous acid. The electrodialysis method has problems such as high energy consumption and low yield, and the cost of industrial application is high. Bipolar membrane electrodialysis technology is a new type of membrane separation technology, which is developed by combining ordinary electrodialysis technology with bipolar membrane. Its device is mainly composed of bipolar membrane stack, DC power supply, feed liquid pump, and feed liquid tank. When an electric field is applied to the plates at both ends of the membrane stack, the anions and cations in the salt chamber migrate to the acid chamber and the alkali chamber respectively under the action of the electric field through the anion and cation exchange membrane, and combine with the H+ and OH- generated by the bipolar membrane to produce the corresponding acid and base. However, when this process produces hypophosphorous acid, hypophosphorous acid is easily oxidized by oxygen in the air and dissolved oxygen in the solution to generate phosphorous acid, resulting in a decrease in the purity and yield of hypophosphorous acid.

[0004] Therefore, there is an urgent need to provide a bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite to solve the above problems. Summary of the invention

[0005] To achieve the above object, the inventor provides a bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite, comprising: a pure water deoxygenation device, a sodium hypophosphite preparation tank, an acid tank, an alkali tank, a salt tank, an extreme liquid tank and an electrodialysis membrane stack;

[0006] The pure water deoxygenation device is connected to the sodium hypophosphite preparation tank, the acid tank and the alkali tank through the deoxygenated water inlet pipe respectively, the sodium hypophosphite preparation tank is connected to the salt tank, the liquid outlets of the acid tank, the alkali tank, the salt tank and the extreme liquid tank are respectively connected to the corresponding liquid inlets of the electrodialysis membrane stack, and the liquid outlets of the electrodialysis membrane stack are respectively connected to the corresponding acid tank, alkali tank, salt tank and extreme liquid tank.

[0007] As a preferred structure of the utility model, circulating pumps are respectively provided on the connecting pipelines between the liquid outlets of the acid tank, alkali tank, salt tank and / or polar liquid tank and the liquid inlets corresponding to the electrodialysis membrane stack.

[0008] As a preferred structure of the utility model, diaphragm pumps are respectively provided on the connecting pipes respectively connecting the pure water deoxygenation device with the sodium hypophosphite preparation tank, the acid tank and / or the alkali tank.

[0009] As a preferred structure of the utility model, it also includes an inert gas storage tank, which is connected to the bottom of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank respectively.

[0010] As a preferred structure of the utility model, the bottoms of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank are respectively provided with aeration devices, and the inert gas storage tanks are respectively connected to the aeration devices.

[0011] As a preferred structure of the utility model, the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank are respectively provided with an oxygen content detector.

[0012] As a preferred structure of the utility model, a respirator is respectively provided on the top of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank.

[0013] As a preferred structure of the utility model, the pure water deoxygenation device is a membrane contactor deoxygenation device.

[0014] As a preferred structure of the utility model, a stirrer is provided on the upper part of the sodium hypophosphite preparation tank.

[0015] As a preferred structure of the utility model, the electrodialysis membrane stack includes at least one group of matching units, and the matching units include anion exchange membrane, cation exchange membrane, bipolar membrane, anode plate and cathode plate, which are arranged in sequence to form a three-compartment bipolar membrane electrodialysis membrane stack; the anode plate is connected to the positive electrode of the regulated DC power supply, and the cathode plate is connected to the negative electrode of the regulated DC power supply.

[0016] Different from the prior art, the above technical solution has the following beneficial effects:

[0017] The device comprises a liquid tank body, a bipolar membrane electrodialysis device with inert gas aeration protection, a deionized water deoxygenation device, a sodium hypophosphite solution preparation tank isolating oxygen in the air, and an inert gas storage and transportation mechanism; the deionized water after deoxygenation is transported into the hypophosphorous acid solution preparation tank, the sodium hypophosphite solution is prepared under the protection of the inert gas, and then the sodium hypophosphite solution is transported into the salt liquid tank from which oxygen has been eliminated, and in the process of acid production by bipolar membrane electrodialysis, the acid liquid tank and the salt liquid tank are continuously aerated with inert gas to reduce the oxidation of hypophosphorous acid to phosphorous acid, thereby preparing high-quality hypophosphorous acid. The device has a reasonable structural design, is easy to install, and is easy to realize industrialized scale-up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The device structure of the specific implementation method is shown in FIG. Figure 1 ;

[0019] Figure 2 The device structure of the specific implementation method is shown in FIG. Figure 2 ;

[0020] Figure 3 The device structure of the specific implementation method is shown in FIG. Figure 3 ;

[0021] Figure 4 The electrodialysis membrane stack structure of the specific implementation method is shown in FIG. Figure 1 ;

[0022] Figure 5 The electrodialysis membrane stack structure of the specific implementation method is shown in FIG. Figure 2 .

[0023] 1. Pure water deoxygenation device; 101. Deoxygenated water inlet pipe; 201. Sodium hypophosphite preparation tank; 202. Acid tank; 203. Alkali tank; 204. Salt tank; 205. Extreme liquid tank; 206. Inert gas storage tank; 207. Oxygen content detector; 208. Respirator; 209. Agitator; 210. Diaphragm pump; 211. Circulation pump; 301. Acid inlet pipeline ; 302, alkali solution inlet pipeline; 303, salt solution inlet pipeline; 304, pole liquid inlet pipeline; 4, electrodialysis membrane stack; 401, acid solution inlet; 402, acid solution outlet; 403, alkali solution inlet; 404, alkali solution outlet; 405, salt solution inlet; 406, salt solution outlet; 407, pole liquid inlet; 408, pole liquid outlet; 409, exchange port. DETAILED DESCRIPTION

[0024] In order to explain the technical content, structural features, achieved objectives and effects of the technical solution in detail, the following is a detailed description in conjunction with specific embodiments and accompanying drawings.

[0025] like Figures 1 to 3As shown, this embodiment provides a bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite, the device comprising a pure water deoxygenation device 1, a sodium hypophosphite preparation tank 201, an acid tank 202, an alkali tank 203, a salt tank 204, a polar liquid tank 205 and an electrodialysis membrane stack 4;

[0026] The pure water deoxygenation device 1 is connected to the sodium hypophosphite preparation tank 201, the acid liquid tank 202 and the alkali liquid tank 203 through the deoxygenated water inlet pipe 101 respectively, the sodium hypophosphite preparation tank 201 is connected to the salt liquid tank 204, the liquid outlets of the acid liquid tank 202, the alkali liquid tank 203, the salt liquid tank 204 and the extreme liquid tank 205 are respectively connected to the corresponding liquid inlets of the electrodialysis membrane stack 4, and the liquid outlets of the electrodialysis membrane stack 4 are respectively connected to the corresponding acid liquid tank 202, the alkali liquid tank 203, the salt liquid tank 204 and the extreme liquid tank 205.

[0027] The device is provided with circulating pumps on the connecting pipelines between the liquid outlets of the acid tank 202, the alkali tank 203, the salt tank 204 and / or the extreme liquid tank 205 and the liquid inlet corresponding to the electrodialysis membrane stack 4. The connecting pipes connected to the pure water deoxygenation device 1 and the sodium hypophosphite preparation tank 201, the acid tank 202 and / or the alkali tank 203 are provided with diaphragm pumps 210. The diaphragm pump 210 is used to transport the feed liquid. It has good sealing performance. The diaphragm pump uses a diaphragm as a pump body, which is isolated from the outside world to avoid leakage problems. In this device, the transmission liquid can be prevented from contacting with the air. In addition, the device also includes an inert gas storage tank 206, which is connected to the bottom of the sodium hypophosphite preparation tank 201, the acid tank 202, the alkali tank 203 and / or the salt tank 204. In this embodiment, the inert gas includes nitrogen, argon or carbon dioxide, preferably nitrogen. Aeration devices (not shown) are respectively provided at the bottom of the sodium hypophosphite preparation tank 201, the acid tank 202, the alkali tank 203 and / or the salt tank 204, and the inert gas storage tank 206 is communicated with the aeration devices respectively to achieve the purpose of nitrogen sealing each tank body. In addition, an oxygen content detector 207 is respectively provided on the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank to measure the oxygen content in the tank body. A respirator 208 is respectively provided on the top of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank, and the respirator 208 is used to discharge the gas in the original tank body, that is, after nitrogen is injected, other air in the tank body is discharged through the respirator. A stirrer 209 is provided on the top of the sodium hypophosphite preparation tank, and the stirrer can accelerate the mixing reaction.

[0028] like Figure 4 and Figure 5As shown, the pure water deoxygenation device 1 in the present device can adopt a membrane contactor deoxygenation device, or a vacuum deoxygenation tower, or a thermal deoxygenation device, preferably a membrane contactor deoxygenation device, and the outlet of the membrane contactor deoxygenation device is provided with an online oxygen content monitor. The electrodialysis membrane stack 4 includes at least one group of matching units, and the matching units include an anion exchange membrane, a cation exchange membrane, a bipolar membrane, an anode plate, and a cathode plate, which are arranged in sequence to form a three-compartment bipolar membrane electrodialysis membrane stack; the anode plate is connected to the positive electrode of a regulated DC power supply, and the cathode plate is connected to the negative electrode of the regulated DC power supply.

[0029] In the above embodiment, when high-purity hypophosphorous acid needs to be prepared, the specific implementation process is as follows: the tank of the preparation device is connected through pipelines, circulation pumps and other components, specifically:

[0030] like Figure 3 , Figure 4 and Figure 5 As shown, the pure water deoxygenation device 1 is connected to the acid tank 202, the alkali tank 203, and the sodium hypophosphite preparation tank 201 through the deoxygenated water inlet pipe 101 and the circulating pump 211; the sodium hypophosphite preparation tank 201 is connected to the salt tank through the sodium hypophosphite inlet pipeline, and the sodium hypophosphite solution is transported into the salt tank through the liquid level difference; Figure 1 and Figure 3As shown, the bottom of the acid tank 202 is connected to the acid inlet 401 of the electrodialysis membrane stack through the acid inlet pipeline 301 and the circulation pump 211; the bottom of the alkali tank 203 is connected to the alkali inlet 403 of the electrodialysis membrane stack through the alkali inlet pipeline 302 and the circulation pump; the bottom of the salt tank is connected to the salt inlet 405 of the electrodialysis membrane stack through the salt inlet pipeline 303 and the circulation pump; the bottom of the pole liquid tank is connected to the pole liquid inlet 407 of the electrodialysis membrane stack through the pole liquid inlet pipeline 304 and the circulation pump. The exchange port 409 in the electrodialysis membrane stack is connected to the exchange port 409; the acid outlet 402 in the electrodialysis membrane stack is connected to the top of the acid tank 202 through the acid outlet pipeline; the alkali outlet 404 in the electrodialysis membrane stack is connected to the top of the alkali tank 203 through the alkali outlet pipeline; the salt outlet 406 of the electrodialysis membrane stack is connected to the top of the salt tank 204 through the salt outlet pipeline; the polar liquid outlet 408 of the electrodialysis membrane stack is connected to the top of the polar liquid tank 205 through the polar liquid outlet pipeline. The inert gas storage tank uses a nitrogen bottle, which is connected to the aeration plate at the bottom of the acid tank, the alkali tank, the salt tank, and the sodium hypophosphite preparation tank through an aeration pipe. Close the outlet valves at the bottom of the preparation tank, acid tank, alkali tank, and salt tank, deoxygenate the ionized water through the pure water deoxygenation device, add sodium hypophosphite to the sodium hypophosphite preparation tank, input deoxygenated water into the sodium hypophosphite preparation tank, start the top agitator 209 to prepare the sodium hypophosphite solution, and during the preparation process, it is necessary to open the nitrogen bottle to continuously aerate the sodium hypophosphite preparation tank to isolate the air. Open the aeration device in the salt tank, acid tank, and alkali tank, and continuously flush nitrogen into the acid tank and alkali tank to replace the air in the tank body, and observe the oxygen content in the tank body through the oxygen content detector 207 until the oxygen content in the tank body is reduced to 0.5%. Add the sodium hypophosphite solution to the salt tank, the hypophosphorous acid solution to the acid tank, the sodium hydroxide solution to the alkali tank, and the sodium sulfate solution or sodium hydroxide solution to the extreme liquid tank. During the addition process, the aeration device in each tank is continuously opened for aeration to isolate the air (oxygen).

[0031] Then, the circulation pump 211 is started to pump the liquid in the salt tank 202, the alkali tank 203 and the acid tank 204 into the electrodialysis membrane stack. The voltage-stabilized DC power supply is turned on to perform bipolar membrane electrodialysis: the hypophosphite in the salt chamber passes through the anion exchange membrane into the acid chamber and combines with the hydrogen ions generated by the bipolar membrane to generate hypophosphorous acid, while the sodium ions pass through the cation exchange membrane into the alkali chamber and combine with the hydroxide generated by the bipolar membrane to generate sodium hydroxide.

[0032] When the voltage of the bipolar membrane electrodialysis stack is higher than the limit voltage, the sodium hypophosphite in the salt solution tank tends to be exhausted and the preparation is completed; the liquid in the acid solution tank is taken out, the acid concentration is titrated with sodium hydroxide solution, and the content of phosphorous acid is determined by ion chromatography.

[0033] The example is as follows: add 158.985g / L sodium hypophosphite solution to the salt tank, add 9.8985g / L hypophosphorous acid solution to the acid tank, and add 6g / L sodium hydroxide solution to the alkali tank. Turn on each circulation pump and conduct electrolysis after power is turned on. During the electrolysis process, the current density is controlled at 18mA / cm 2 Under constant current conditions, as the electrodialysis proceeds, the concentration of hypophosphorous acid in the acid chamber and the concentration of sodium hydroxide in the alkali chamber continue to increase, and the concentration of sodium hypophosphite in the salt solution tank continues to decrease, until the voltage of the electrodialysis membrane stack increases sharply due to the exhaustion of salt solution in the salt chamber, and the experiment is stopped. The sodium hydroxide obtained in the alkali chamber is 44.8g / L, and the hypophosphorous acid obtained in the acid chamber is 71.27g / L, of which the phosphorous acid content is 0.5g / L.

[0034] This device can be used to prepare high-purity hypophosphorous acid, and use deoxygenated deionized water to prepare sodium hypophosphite solution, isolate oxygen in the air during solution storage and transportation, and continuously aerate the acid tank and salt tank with inert gas during the acid production process of bipolar membrane electrodialysis, reduce the oxidation of hypophosphorous acid to phosphorous acid, greatly reduce the content of impurity phosphorous acid, and improve the purity of the prepared hypophosphorous acid. This device has a reasonable design, simple structure, convenient installation, and is easy to realize industrialized scale-up production.

[0035] It should be noted that although the above embodiments have been described in this article, this does not limit the scope of patent protection of the utility model. Therefore, based on the innovative concept of the utility model, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the utility model specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included in the scope of patent protection of the utility model.

Claims

1. A bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite, characterized in that: include: Pure water deoxygenation device, sodium hypophosphite preparation tank, acid tank, alkali tank, brine tank, polar liquid tank and electrodialysis membrane stack; The pure water deoxygenation device is connected to the sodium hypophosphite preparation tank, the acid tank and the alkali tank through the deoxygenated water inlet pipe respectively, the sodium hypophosphite preparation tank is connected to the salt tank, the liquid outlets of the acid tank, the alkali tank, the salt tank and the extreme liquid tank are respectively connected to the corresponding liquid inlets of the electrodialysis membrane stack, and the liquid outlets of the electrodialysis membrane stack are respectively connected to the corresponding acid tank, alkali tank, salt tank and extreme liquid tank.

2. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to claim 1, characterized in that: Circulation pumps are respectively arranged on the connecting pipelines between the liquid outlets of the acid tank, the alkali tank, the salt tank and / or the extreme liquid tank and the liquid inlets corresponding to the electrodialysis membrane stack.

3. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to claim 1, characterized in that: Diaphragm pumps are respectively arranged on the connecting pipes respectively connecting the pure water deoxygenation device with the sodium hypophosphite preparation tank, the acid tank and / or the alkali tank.

4. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to claim 1, characterized in that: The invention also comprises an inert gas storage tank, which is respectively connected with the bottom of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank.

5. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to claim 4, characterized in that: The bottoms of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank are respectively provided with aeration devices, and the inert gas storage tanks are respectively connected to the aeration devices.

6. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to any one of claims 1 to 5, characterized in that: The sodium hypophosphite preparation tank, the acid solution tank, the alkali solution tank and / or the salt solution tank are respectively provided with an oxygen content detector.

7. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to any one of claims 1 to 5, characterized in that: Respirators are respectively arranged on the tops of the sodium hypophosphite preparation tank, the acid tank, the alkali tank and / or the salt tank.

8. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to any one of claims 1 to 5, characterized in that: The pure water deoxygenation device is a membrane contactor deoxygenation device.

9. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to any one of claims 1 to 5, characterized in that: A stirrer is arranged on the upper part of the sodium hypophosphite preparation tank.

10. The bipolar membrane electrodialysis device for preparing high-purity hypophosphorous acid from sodium hypophosphite according to any one of claims 1 to 5, characterized in that: The electrodialysis membrane stack includes at least one group of matching units, which include an anion exchange membrane, a cation exchange membrane, a bipolar membrane, an anode plate and a cathode plate, which are arranged in sequence to form a three-compartment bipolar membrane electrodialysis membrane stack; the anode plate is connected to the positive electrode of a regulated DC power supply, and the cathode plate is connected to the negative electrode of the regulated DC power supply.

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