阅读说明：本技术 一种双极膜电渗析辅助制备四乙基四氟硼酸铵的方法 (Method for preparing tetraethyl ammonium tetrafluoroborate by bipolar membrane electrodialysis assistance ) 是由 沈江南 唐聪 苗孟杰 阮慧敏 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种双极膜电渗析辅助制备四乙基四氟硼酸铵的方法,其包括以下步骤：1)双极膜电渗析制备四乙基氢氧化铵：所述双极膜电渗析设备和原理参见附图,电渗析处理结束后,取出碱室中的料液；2)中和法合成四乙基四氟硼酸铵：将步骤1)中碱室中的料液取出后倒入混合搅拌装置中,搅拌条件下加入等摩尔量的氟硼酸,在室温下充分反应；将反应完全的液体加入到减压旋转蒸发仪中,蒸发至出现白色晶体停止蒸发,将蒸发浓缩液至于烘箱中干燥得到白色晶体,即为四乙基四氟硼酸铵成品。本发明提供的双极膜电渗析辅助制备四乙基四氟硼酸铵的方法能有效提高产品收率和纯度。(The invention discloses a method for preparing tetraethyl ammonium tetrafluoroborate by bipolar membrane electrodialysis assistance, which comprises the following steps: 1) preparing tetraethyl ammonium hydroxide by bipolar membrane electrodialysis: referring to the attached drawings for the bipolar membrane electrodialysis equipment and principle, after the electrodialysis treatment is finished, taking out feed liquid in an alkali chamber; 2) synthesizing tetraethyl ammonium tetrafluoroborate by a neutralization method: taking out the feed liquid in the alkali chamber in the step 1), pouring the feed liquid into a mixing and stirring device, adding equal molar weight of fluoboric acid under stirring, and fully reacting at room temperature; and adding the liquid which is completely reacted into a reduced pressure rotary evaporator, evaporating until white crystals appear, stopping evaporating, and drying the evaporated concentrated solution in an oven to obtain white crystals, namely the tetraethylammonium tetrafluoroborate finished product. The method for preparing tetraethyl ammonium tetrafluoroborate by using bipolar membrane electrodialysis assistance provided by the invention can effectively improve the product yield and purity.)

1. A method for preparing tetraethyl ammonium tetrafluoroborate by assistance of bipolar membrane electrodialysis comprises the following steps:

1) preparation of tetraethyl ammonium hydroxide by bipolar membrane electrodialysis

The bipolar membrane electrodialysis device comprises a power supply, an anode plate, a cathode plate and an electrodialysis membrane stack stacked between the anode plate and the cathode plate, wherein an outermost membrane of the electrodialysis membrane stack and an adjacent electrode plate form a polar liquid chamber; the electrodialysis membrane stack is formed by sequentially arranging bipolar membranes, a cation exchange membrane, an anion exchange membrane, a cation exchange membrane and bipolar membranes at intervals, and the outermost membranes are the bipolar membranes; the electrodialysis membrane stack consists of at least one electrodialysis unit, and each electrodialysis unit is a four-compartment structure formed by sequentially arranging bipolar membranes, cation exchange membranes, anion exchange membranes, cation exchange membranes and bipolar membranes at intervals to form a protection chamber, an acid chamber, a feed liquid chamber and an alkali chamber;

adding a sulfuric acid solution into the polar liquid chamber and the protection chamber, adding deionized water into the acid chamber and the alkali chamber, adding a tetraethylammonium chloride solution with the concentration of 0.2-0.6 mol/L into the material liquid chamber, electrifying the anode plate and the cathode plate to carry out electrodialysis treatment, and taking out the material liquid in the alkali chamber after the reaction is finished;

2) Synthesis of tetraethyl ammonium tetrafluoroborate by neutralization method

Taking out the feed liquid in the alkali chamber in the step 1), pouring the feed liquid into a mixing and stirring device, adding equal molar weight of fluoboric acid under stirring, and fully reacting at room temperature; and adding the liquid which is completely reacted into a reduced pressure rotary evaporator, evaporating until white crystals appear, stopping evaporating, and drying the evaporated concentrated solution in an oven to obtain white crystals, namely the tetraethylammonium tetrafluoroborate finished product.

2. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 1, characterized in that: the concentration of the tetraethylammonium chloride solution is 0.3-0.4 mol/L.

3. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 1, characterized in that: the concentration of the tetraethylammonium chloride solution was 0.4 mol/L.

4. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to one of claims 1 to 3, characterized in that: the concentration of the sulfuric acid solution is between 0.1 and 5 percent.

5. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to one of claims 1 to 3, characterized in that: the bipolar membrane isBP-1E bipolar membrane, the anion exchange membrane is

6. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 5, characterized in that: the conditions of the electrodialysis treatment are as follows: the electrodialysis membrane stack consists of 5 electrodialysis units, and the effective area of each membrane is 189cm²The feed liquid in each compartment respectively circularly flows under the action of a circulating pump, the flow rate of the feed liquid in each compartment is kept consistent and controlled at 20-30L/h, a power supply is started, and the current density is controlled at 6-14 mA/cm²Controlling the temperature of the feed liquid in each compartment not to be higher than 40 ℃, and when the temperature is processed to the conductivity of the feed liquid compartment to be lower than 300 mu S-cm^-1When the reaction reaches the end point.

7. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 6, characterized in that: the flow rate of each compartment is controlled to be 20L/h, and the current density is controlled to be 12mA/cm²The concentration of the tetraethylammonium chloride solution was 0.4 mol/L.

8. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 1, characterized in that: and (3) in the mixing and stirring device in the step 2), adding fluoboric acid, and reacting for more than half an hour.

9. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 1, characterized in that: in the step 2), the liquid which is completely reacted is added into a reduced pressure rotary evaporator, the evaporation is stopped until white crystals appear, and the temperature is not higher than 60 ℃ in the evaporation process.

10. The bipolar membrane electrodialysis-assisted preparation of tetraethylammonium tetrafluoroborate according to claim 1, characterized in that: in step 2), the temperature during evaporation was controlled at 50 ℃.

Technical Field

The invention relates to a preparation method of tetraethyl ammonium tetrafluoroborate.

Technical Field

Tetraethylammonium tetrafluoroborate (Et) ₄NBF₄) Is a white to off-white crystal with the properties of small density, high melting point, low viscosity, stability and good electrical conductivity. Et (Et)₄NBF₄The organic electrolyte is widely applied to organic electrolytes of super capacitors as electrolyte salts, and has applications and reports in lithium ion batteries, electrochemical experimental analysis, drug intermediates and other aspects.

Currently, the methods for preparing ammonium tetrafluoroborate are mainly the neutralization method, the quaternary halogen ammonium method and the triethylamine method.

Neutralization method: the quaternary ammonium base and the fluoboric acid are adopted for direct neutralization, the yield is high, and the product purity is high.

Quaternary ammonium halide process: tetraethylammonium chloride is used as a raw material, butanol/isobutanol/octanol is used as a solvent, the tetraethylammonium chloride reacts with fluoboric acid, the reaction product is subjected to reduced pressure concentration and crystallization, ethanol is washed and is recrystallized for multiple times, and then the product is dried to obtain the product, wherein the yield is 64-70%.

The triethylamine method: dimethyl carbonate and triethylamine are used as raw materials and react with tetrafluoroboric acid in an alcohol solvent to obtain triethyl methyl ammonium tetrafluoroborate, methyl iodide and triethylamine are used as reactants, acetone is used as a solvent, and then the triethyl methyl ammonium tetrafluoroborate is generated with silver tetrafluoroborate in ethanol.

Of the above methods, the neutralization method is currently the most widely used method. Although ammonium tetrafluoroborate can be prepared by the quaternary ammonium halide method and the triethylamine method, a large amount of organic solvents, complex process and high cost are generated in the synthesis process, and the development of ammonium tetrafluoroborate is severely restricted. Most of quaternary ammonium hydroxide in the traditional neutralization method is obtained by exchanging quaternary ammonium halide salt ions, so that the impurities such as sodium, potassium, iron and the like cannot enter products, the purification difficulty is increased, and the production cost is increased.

CN 110922333A discloses a method for preparing tetraethyl ammonium tetrafluoroborate by electrodialysis technology, which is carried out in an electrodialysis device with a four-compartment structure formed by sequentially arranging a cation exchange membrane, an anion exchange membrane, a cation exchange membrane, an anion exchange membrane and a cation exchange membrane at intervals, wherein the compartments are close to each otherThe anode is 1 chamber, and then 2, 3 and 4 chambers are arranged in sequence; the method comprises the following steps: respectively introducing tetraethylammonium halide salt aqueous solution and tetrafluoroboric acid aqueous solution into a chamber 2 and a chamber 4, respectively introducing pure water into a chamber 1 and a chamber 3, respectively, adding sulfuric acid solution with the mass concentration of 0.1% into an electrode solution chamber, performing electrodialysis treatment until the current is lower than 0.2A or the conductivity of the liquid in the chamber 2 or the chamber 4 is lower than 300 mu S-cm^-1And (3) taking out the liquid in the chamber (3), evaporating, concentrating, filtering, and drying a filter cake to obtain the tetraethylammonium tetrafluoroborate. However, the method still has disadvantages in terms of current efficiency, product yield, purity, and the like.

Disclosure of Invention

The invention aims to provide a method for preparing tetraethylammonium tetrafluoroborate by bipolar membrane electrodialysis assistance, so as to improve the product yield and purity.

In order to solve the technical problems, the invention adopts the following technical scheme:

A method for preparing tetraethyl ammonium tetrafluoroborate by assistance of bipolar membrane electrodialysis comprises the following steps:

1) preparation of tetraethyl ammonium hydroxide by bipolar membrane electrodialysis

The bipolar membrane electrodialysis device comprises a power supply, an anode plate, a cathode plate and an electrodialysis membrane stack stacked between the anode plate and the cathode plate, wherein an outermost membrane of the electrodialysis membrane stack and an adjacent electrode plate form a polar liquid chamber; the electrodialysis membrane stack is formed by sequentially arranging bipolar membranes, a cation exchange membrane, an anion exchange membrane, a cation exchange membrane and bipolar membranes at intervals, and the outermost membranes are the bipolar membranes; the electrodialysis membrane stack consists of at least one electrodialysis unit, and each electrodialysis unit is a four-compartment structure formed by sequentially arranging bipolar membranes, cation exchange membranes, anion exchange membranes, cation exchange membranes and bipolar membranes at intervals to form a protection chamber, an acid chamber, a feed chamber and an alkali chamber (product chamber);

adding a sulfuric acid solution into the polar liquid chamber and the protection chamber, adding deionized water into the acid chamber and the alkali chamber, adding a tetraethylammonium chloride solution with the concentration of 0.2-0.6 mol/L into the material liquid chamber, electrifying the anode plate and the cathode plate to carry out electrodialysis treatment, and taking out the material liquid in the alkali chamber after the reaction is finished;

2) Synthesis of tetraethyl ammonium tetrafluoroborate by neutralization method

Taking out the feed liquid in the alkali chamber in the step 1), pouring the feed liquid into a mixing and stirring device, adding equal molar weight of fluoboric acid under stirring, and fully reacting at room temperature; and adding the liquid which is completely reacted into a reduced pressure rotary evaporator, evaporating until white crystals appear, stopping evaporating, and drying the evaporated concentrated solution in an oven to obtain white crystals, namely the tetraethylammonium tetrafluoroborate finished product.

The preparation principle of the step 1) of the invention is as follows: under the action of a direct current electric field, cations and anions pass through a cation exchange membrane and an anion exchange membrane respectively in a membrane stack to perform directional migration, namely tetraethylammonium cations enter an alkali chamber through the cation exchange membrane in a directional migration manner and are combined with OH & lt- & gt generated by a bipolar membrane to form tetraethylammonium hydroxide. At the same time, H⁺And chloride ions respectively penetrate through the ion exchange membrane under the action of an electric field and enter the acid chamber to form by-product hydrochloric acid. In the design of bipolar membrane electrodialysis, the concentration of a tetraethylammonium chloride solution is set to be 0.2-0.6 mol/L, a protection chamber is arranged, and a sulfuric acid solution instead of a conventional sodium sulfate solution is used as an electrode solution and a protection solution, so that a high-purity tetraethylammonium hydroxide product can be obtained. Through the design, the ion exchange reaction in the bipolar membrane electrodialysis device can be fully reacted, and the content of the heteroatom in the tetraethylammonium hydroxide product is effectively reduced, so that the yield and the purity of the final tetraethylammonium tetrafluoroborate finished product are improved.

The bipolar membrane electrodialysis device generally comprises a protective liquid tank, an acid tank, a material liquid tank, an alkali tank and an electrode liquid tank, wherein the electrode liquid tank, the protective liquid tank, the acid tank, the material liquid tank and the alkali tank form a circulating loop with a protective chamber, an acid chamber, a material liquid chamber, an alkali chamber and an electrode liquid chamber through circulating pumps 1, 2, 3, 4 and 5 respectively, and initial material liquids of the protective liquid tank, the acid tank, the material liquid tank, the alkali tank and the electrode liquid tank are respectively sulfuric acid solution, pure water, tetraethylammonium chloride aqueous solution, pure water and sulfuric acid solution.

In the invention, the sulfuric acid solution plays a role in electric conduction, and the concentration of the sulfuric acid solution can be between 0.1 and 5 percent.

In the bipolar membrane electrodialysis, the concentration of the tetraethylammonium chloride solution is set to be 0.2-0.6 mol/L, and if the concentration of the tetraethylammonium chloride solution is further increased, the purity of a tetraethylammonium hydroxide product is correspondingly reduced. Preferably, the concentration of the tetraethylammonium chloride solution is 0.3-0.4 mol/L, and most preferably 0.4 mol/L.

In the bipolar membrane electrodialysis of the invention, a person skilled in the art can set a device and set appropriate electrodialysis parameters according to actual conditions.

Preferably, the bipolar membrane is made by ASTOM of JapanBP-1E bipolar membrane, the anion exchange membrane is made by ASTOM of Japan AHA anion exchange membrane, the cation exchange membrane is made by ASTOM company of Japan

CMX cation exchange membranes.

Preferably, the conditions of the electrodialysis treatment are as follows: the electrodialysis membrane stack consists of 5 electrodialysis units, and the effective area of each membrane is 189cm²The feed liquid in each compartment respectively circularly flows under the action of a circulating pump, the flow rate of the feed liquid in each compartment is kept consistent and controlled at 20-30L/h, a power supply is started, and the current density is controlled at 6-14 mA/cm²Controlling the temperature of the feed liquid in each compartment not to be higher than 40 ℃, and when the temperature is processed to the conductivity of the feed liquid compartment to be lower than 300 mu S-cm^-1When the reaction reaches the end point.

As a further preference, the flow rate of each compartment is controlled to be 20L/h.

Further preferably, the current density is controlled to 12mA/cm²。

Preferably, the concentration of the tetraethylammonium chloride solution is 0.4 mol/L.

Particularly preferred conditions for the electrodialysis treatment according to the invention are: the electrodialysis membrane stack consists of 5 electrodialysis units,the effective area of each membrane is 189cm²The feed liquid in each compartment respectively circularly flows under the action of a circulating pump, the flow rate of the feed liquid in each compartment is kept consistent and controlled at 20L/h, a power supply is started, and the current density is controlled at 12mA/cm²And controlling the feed liquid temperature of each compartment not to be higher than 40 ℃.

Preferably, the reaction time after the fluoroboric acid is added to the mixing and stirring apparatus is more than half an hour.

Preferably, the liquid completely reacted is added into a reduced pressure rotary evaporator, the evaporation is stopped until white crystals appear, and the temperature in the evaporation process is not higher than 60 ℃, and more preferably, the temperature is controlled at 50 ℃.

Preferably, the evaporation concentrated solution is placed in an oven for drying, the temperature is adjusted to 60 ℃, and the drying time is 24 h.

Due to the adoption of the technical scheme, the invention has the advantages that:

(1) the method adopts the bipolar membrane electrodialysis for assisting in preparing the tetraethyl ammonium tetrafluoroborate, the byproduct hydrochloric acid of the bipolar membrane electrodialysis can be recovered, no redundant impurities are generated, and the target product has high yield and high purity.

(2) The invention adopts bipolar membrane electrodialysis to prepare tetraethyl ammonium hydroxide, and has high current efficiency.

Drawings

FIG. 1 is a schematic diagram of the bipolar membrane electrodialysis assisted tetraethylammonium tetrafluoroborate preparation method;

FIG. 2 is a process flow diagram for the preparation of tetraethylammonium tetrafluoroborate according to the present invention.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples, but the scope of the present invention is not limited thereto:

as shown in fig. 1, the bipolar membrane electrodialysis apparatus comprises: a steady-flow and voltage-stabilizing direct-current power supply (not shown), an anode plate 1, a cathode plate 2, an electrodialysis membrane stack, a protective liquid tank, an acid tank, a feed liquid tank, an alkali tank and a polar liquid tank (not shown);

The electrodialysis membrane stack is arranged between the anode plate 1 and the cathode plate 2, and an outermost membrane of the electrodialysis membrane stack and an adjacent electrode plate form a polar liquid chamber I; the electrodialysis membrane stack is formed by sequentially arranging a bipolar membrane B, a cation exchange membrane C, an anion exchange membrane A, a cation exchange membrane C and the bipolar membrane B at intervals, and the outermost membrane is the bipolar membrane B; the electrodialysis membrane stack is composed of at least one electrodialysis unit, each electrodialysis unit is of a four-compartment structure formed by sequentially arranging a bipolar membrane B, a cation exchange membrane C, an anion exchange membrane A, a cation exchange membrane C and the bipolar membrane B at intervals, and the four compartments are sequentially a protection chamber II, an acid chamber III, a material liquid chamber IV and an alkali chamber IV; the compartment is provided with an external condensing coil to control the temperature of the feed liquid, wherein the external condensing coil is immersed in ice water to achieve the purpose of cooling;

the polar liquid tank, the protective liquid tank, the acid tank, the material liquid tank and the alkali tank form a circulating loop with a polar chamber I, a protective chamber II, an acid chamber III, a material liquid chamber IV and an alkali chamber IV through circulating pumps 1, 2, 3, 4 and 5 respectively, and starting material liquids of the protective liquid tank, the acid tank, the material liquid tank, the alkali tank and the polar liquid tank are 0.1% sulfuric acid solution, pure water, tetraethylammonium chloride aqueous solution, pure water and 0.1% sulfuric acid solution respectively.