CN116606203A - A method for improving the purity of acetic acid - Google Patents

Abstract

The invention discloses a method for improving the purity of acetic acid, and relates to the technical field of acetic acid purification. The method comprises the following steps: mixing acetic acid to be treated with potassium permanganate, rectifying the mixed reaction liquid after oxidation-reduction reaction to obtain a purified acetic acid product; the feeding amount of the potassium permanganate is 1-2g of the potassium permanganate added per liter of the acetic acid solution to be treated. The invention can oxidize soluble impurities in acetic acid into inorganic salts with boiling point difference by virtue of oxidation-reduction reaction of potassium permanganate and acetic acid, and separate excessive potassium permanganate and inorganic salts with boiling point difference from acetic acid by rectification by utilizing the boiling point difference, thereby achieving the aim of purification. The method has the advantages of small environmental pollution, simple steps, low cost, lower potential safety hazard, easy popularization and application, capability of obtaining high-purity acetic acid and capability of effectively removing dichromate in the acetic acid.

Description

A method for improving the purity of acetic acid

technical field

The invention relates to the technical field of acetic acid purification, in particular to a method for improving the purity of acetic acid.

Background technique

Acetic acid, commonly known as acetic acid, gets its name because it is the main component of vinegar and is one of the most important fatty acids. Acetic acid is a monobasic weak carboxylic acid, which has the typical properties of carboxylic acids. It reacts with certain metals, metal oxides and hydroxides to form salts. Many acetates have important uses; acetic acid can also undergo esterification reactions to generate various A derivative with important uses, such as methyl acetate, ethyl ester, propyl ester, butyl ester, etc., is an excellent solvent for the paint and paint industry. Vinyl acetate acid produced by acetic acid and acetylene is an important raw material for the synthesis of drugs, dyes, and fragrances, as well as an important solvent for rubber processing. Acetic acid plays an important role in industrial production and organic synthesis.

At present, the commercially available high-purity acetic acid has a purity of about 99.5%. Although its content is high, its impurities are all soluble impurities, including dichromate. In an acidic environment, dichromate will undergo the following reaction: Cr ₂ O ₇ ^2- +8H ⁺ → 2Cr ³⁺ +4H ₂ O+3[O], the generated [O] is reductive, making the actual experimental data The reproducibility of the experiment decreased obviously, and even caused some experimental interference. Acetic acid needs to be further purified so that its concentration can meet the requirements of the experiment.

In view of this, the present invention is proposed.

Contents of the invention

The purpose of the present invention is to provide a method for improving the purity of acetic acid so as to improve the purity of acetic acid, which greatly reduces the interference of dichromate to the experiment.

The present invention is achieved like this:

The invention provides a method for improving the purity of acetic acid, which comprises the following steps: mixing acetic acid to be treated with potassium permanganate, rectifying the mixed reaction solution after redox reaction to obtain purified acetic acid product; high manganese The feeding amount of potassium permanganate is to drop 1-2g potassium permanganate per liter of acetic acid solution to be treated.

The inventors have found that, by virtue of the redox reaction between potassium permanganate and acetic acid, the soluble impurities (including dichromate) in acetic acid can be oxidized into inorganic salts with a difference in boiling point, and then the difference in boiling point can be used to distill the Excess potassium permanganate and inorganic salts with different boiling points are separated from acetic acid to achieve the purpose of purification. The method has the advantages of little environmental pollution, simple steps, low cost, low safety hazard, easy popularization and application, high-purity acetic acid can be obtained, and dichromate in acetic acid can be effectively removed.

The inventor has found through a large number of experiments: in the purification step, the feeding amount of potassium permanganate is particularly critical for the purity of product acetic acid, and controlling the input of 1-2g potassium permanganate per liter of acetic acid solution to be treated helps to greatly reduce the solubility The content of impurities, especially the content of dichromate-reducing substances (O) is substantially reduced. Addition too low or too high all can cause the soluble impurity content in the product acetic acid to increase, and the acetic acid purity descends. Potassium permanganate is selected to react with acetic acid, which has a better resolution than other strong oxidants, and helps to separate excess potassium permanganate and inorganic salts with boiling point differences from acetic acid through differences in boiling points.

In a preferred embodiment of the application of the present invention, after the acetic acid to be treated is mixed with potassium permanganate, they are stirred and heated at 75-80° C. for 1-2 hours.

For example, the reaction is heated with stirring at 75°C, 76°C, 77°C, 78°C, 79°C or 80°C. The stirring reaction time is 1h, 1.2h, 1.3h, 1.5h, 1.8h or 2h.

In a preferred embodiment of the application of the present invention, after the acetic acid to be treated is mixed with potassium permanganate, they are stirred and heated at 78±2° C. for 1-2 hours.

In a preferred embodiment of the application of the present invention, after the temperature rises to 75° C., the acetic acid to be treated is mixed with potassium permanganate. Such a mixing method helps to keep the soluble impurities in the acetic acid reacting with potassium permanganate quickly and efficiently at a temperature close to the reaction.

In a preferred embodiment of the application of the present invention, after the acetic acid to be treated is mixed with potassium permanganate, the mixture is first stirred and heated to dissolve the potassium permanganate, and then left to stand for 60-80 hours. In this embodiment, as long as the potassium permanganate is dissolved, the reaction can be left to stand and the same redox effect can be achieved. This embodiment will make the reaction time longer.

In a preferred embodiment of the application of the present invention, after mixing the acetic acid to be treated with potassium permanganate, stir and heat at 75-78°C to dissolve the potassium permanganate, and let it stand for 60-80 hours;

In an optional embodiment, after the acetic acid to be treated is mixed with potassium permanganate, it is stirred and heated at 78° C. to dissolve the potassium permanganate, and then left to stand for 72 hours.

In a preferred embodiment of the application of the present invention, the feeding amount of potassium permanganate is 1.2-2g of potassium permanganate per liter of acetic acid solution to be treated.

In an optional embodiment, the dosage of potassium permanganate is 1.2-1.5g of potassium permanganate per liter of acetic acid solution to be treated. Adding 1.2-1.5g of potassium permanganate per liter of acetic acid solution to be treated has a better effect of reducing the concentration of reduced dichromate than 1g or 2g of potassium permanganate, and the purity of acetic acid in the finished product is higher.

In a preferred embodiment of the application of the present invention, the rectification includes: first gradually raising the temperature of the mixed reaction solution (according to a heating rate of 3-3.5°C/min) to 117°C ± 0.5°C, maintaining 117°C ± 0.5°C, and waiting for distillation After the obtained fraction reaches 10-12% of the total volume of the mixed reaction solution, replace the fraction collection container to collect acetic acid until the remaining 8-10% volume of the mixed reaction solution in the distillation bottle, the acetic acid in the collection container is the purified acetic acid. If the temperature rises too fast, the proportion of the high-purity acetic acid fraction will decrease, and the proportion of the impurity fraction will increase, which may cause high-purity acetic acid until the distilled fraction reaches 20-30% of the total volume of the mixed reaction solution. Fractions appear, which brings unnecessary problems such as insufficient purity of acetic acid and repeated purification. Before the rectification ends, the remaining 8-10% volume of the mixed reaction liquid in the distillation bottle is mostly impurities.

In a preferred embodiment of the application of the present invention, rectification includes: adjusting the voltage of the heating mantle to 150V, replacing the fraction collection container after the head fraction to be received reaches 10-12% of the total volume of the mixed reaction solution, and adjusting the voltage to 220V until 8-10% of the volume of the mixed reaction solution remains in the distillation bottle.

In a preferred embodiment of the application of the present invention, redox reaction and rectification steps are repeated 1-3 times; the purity of the acetic acid product is greater than or equal to 99.7%. The method provided by the invention helps to significantly improve the purity of acetic acid.

The present invention has the following beneficial effects:

The present invention utilizes the redox reaction between potassium permanganate and acetic acid to oxidize the soluble impurities (including dichromate) in acetic acid into inorganic salts with different boiling points, and then use the difference in boiling points to distill the excess Potassium permanganate and inorganic salts with different boiling points are separated from acetic acid to achieve the purpose of purification. The method has the advantages of little environmental pollution, simple steps, low cost, low safety hazard, easy popularization and application, high-purity acetic acid can be obtained, and dichromate in acetic acid can be effectively removed.

The inventor has found through a large number of experiments: in the purification step, the feeding amount of potassium permanganate is particularly critical for the purity of product acetic acid, and controlling the input of 1-2g potassium permanganate per liter of acetic acid solution to be treated helps to greatly reduce the solubility The content of impurities, especially the content of dichromate-reducing substances (O) is substantially reduced. Addition too low or too high all can cause the soluble impurity content in the product acetic acid to increase, and the acetic acid purity descends.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

The characteristics and performance of the present invention will be described in further detail below in conjunction with the examples.

Example 1

The present embodiment provides a novel multi-step purification method for acetic acid, which mainly uses redox (chemical method) in combination with rectification (physical separation) to separate acetic acid from impurities, specifically as follows:

(1) Redox

Take 200mL of the original acetic acid sample with a purity of 99.5%, put it into a 500ml distillation flask, install a condenser on the top of the flask, seal the side ports with special glass stoppers, and insert a thermometer at the same time to control the actual reaction temperature. a certain temperature range.

After the reaction starts, turn on the water bath heater for heating, set the heating temperature in the range of 78±2°C, and at the same time turn on the condensate water for condensation. After the thermometer shows that the temperature reaches 75°C, add 0.3g KMnO ₄ in an amount of 1.5g/L to In acetic acid, and start stirring, make it react more fully. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h.

(2) Distillation

After heating, transfer the acetic acid to the one-necked bottle and add zeolite, place the one-necked bottle in the electric heating mantle, and build the thorn-type rectification column, distillation head, thermometer, condenser tube, receiving tube, and one-necked bottle in sequence. Fix the rectification device above, turn on the power supply of the electric heating mantle, adjust the voltage to 150V, and turn on the condensed water at the same time, after receiving 20ml (± 2ml) of the head fraction, replace the one-mouth bottle for feeding, at this time the one-mouth bottle starts to collect Purified acetic acid, and adjust the voltage to 220V. When the acetic acid in the single-necked bottle at the bottom of the tower is evaporated to 15-20mL, turn off the power supply of the electric heating mantle and let it stand still. When the one-necked bottle at the bottom of the tower no longer boils and no liquid is generated in the condenser tube, the device is disassembled.

Example 2

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.2g KMnO ₄ to the acetic acid in an amount of 1g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h. All the other processing steps are with embodiment 1.

Example 3

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.24g KMnO ₄ to the acetic acid in an amount of 1.2g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h. All the other processing steps are with embodiment 1.

Example 4

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.4g KMnO ₄ to the acetic acid in an amount of 2g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h. All the other processing steps are with embodiment 1.

Example 5

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.3g KMnO ₄ to the acetic acid in an amount of 1.5g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 76°C, keep stirring and heating at 76°C for 1h. All the other processing steps are with embodiment 1.

Example 6

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.3g KMnO ₄ to the acetic acid in an amount of 1.5g/L, and start stirring until the potassium permanganate is dissolved, and then let it stand 70h.

Example 7

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.3g KMnO ₄ to the acetic acid in an amount of 1.5g/L, and start stirring until the potassium permanganate is dissolved, and then let it stand 72h.

Comparative example 1

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, no KMnO ₄ is added to the acetic acid, and the stirring is started to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h. All the other processing steps are with embodiment 1.

Comparative example 2

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.1g KMnO ₄ to the acetic acid in an amount of 0.5g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 1.5h. All the other processing steps are with embodiment 1.

Comparative example 3

Compared with Example 1, the only difference is that after the thermometer shows that the temperature reaches 75°C, add 0.3g KMnO ₄ to the acetic acid in an amount of 1.5g/L, and start stirring to make the reaction more complete. After the temperature of the water bath rose to 78°C, keep stirring and heating at 78°C for 10 minutes. All the other processing steps are with embodiment 1.

Experimental example 1

The purified acetic acid of Examples 1-7 and Comparative Examples 1-3 were subjected to fraction quality inspection respectively, wherein Example 2 was repeated twice, using the same production batch of acetic acid, each taking 200mL, and dropping into different proportions of potassium permanganate reaction, distillation. The quality inspection results (marked as P(x), (x) representing the batch) of the potassium permanganate dosage (denoted as R(x), (x) represents the batch) and the cuts obtained in the single-necked bottle were made The following table. Finally, R4=1.5g/L and P4=14ppm are the best conditions.

Repeat the above redox-rectification 4 times to get all the data of R1-R6 and P1-P6 in total, the specific data are shown in the following table:

Example 1 has the lowest content of substance (O) for reducing dichromate, and Comparative Example 1 does not add potassium permanganate, and the content of substance (O) for reducing dichromate is 223ppm. When the amount of potassium permanganate added is in the range of 1g/L-2g/L, the content of the dichromate-reducing substance (O) is lower than 100ppm. It shows that the addition of potassium permanganate in the above range has a good effect of reducing impurities. However, shortening the heating time (comparative example 3) will lead to insufficient reaction, resulting in a decrease in the purification effect.

The finished product recovery rate of embodiment 1: 800/1000=80%, acetic acid purity and finished product recovery rate detection use GC, according to the area normalization method of GB/T 9722; The material (O) content determination of reducing dichromate is to use The method in GB/T 1628-2020 is used for testing. After analysis and detection, the purity of acetic acid in the finished product is about 99.8%. The acetic acid purity of embodiment 2, the repeated experiment of embodiment 2, embodiment 4 are respectively 99.7%, 99.7%, 99.7%.

The present invention combines the chemical method with the physical method, and first uses potassium permanganate to remove impurities. In the process of rectification, the excess potassium permanganate will be decomposed by heat, and then use the difference in boiling point to separate acetic acid and other inorganic salts. Separation, so as to achieve the purpose of purification. The method has the advantages of little environmental pollution, simple steps, low cost and low potential safety hazards.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for improving the purity of acetic acid, comprising the steps of: mixing acetic acid to be treated with potassium permanganate, rectifying the mixed reaction liquid after oxidation-reduction reaction to obtain a purified acetic acid product; the feeding amount of the potassium permanganate is 1-2g of potassium permanganate added per liter of acetic acid solution to be treated.

2. The method according to claim 1, wherein the acetic acid to be treated is mixed with potassium permanganate and then heated with stirring at 75-80 ℃ for 1-2 hours.

3. The method according to claim 2, wherein the acetic acid to be treated is mixed with potassium permanganate and then heated with stirring at 78+ -2deg.C for 1-2h.

4. A method according to claim 3, characterized in that after the temperature has been raised to 75 ℃, the acetic acid to be treated is mixed with potassium permanganate.

5. The method according to claim 1, wherein after the acetic acid to be treated is mixed with potassium permanganate, the mixture is stirred and heated to dissolve the potassium permanganate and then is left to stand for 60 to 80 hours.

6. The method according to claim 5, wherein after the acetic acid to be treated is mixed with potassium permanganate, stirring and heating are carried out at 75-78 ℃ to dissolve the potassium permanganate, and standing is carried out for 60-80 hours;

preferably, after the acetic acid to be treated is mixed with the potassium permanganate, stirring and heating are carried out at 78 ℃ to dissolve the potassium permanganate, and standing is carried out for 72 hours.

7. The method according to any one of claims 1 to 6, wherein the potassium permanganate is added in an amount of 1.2 to 2g of potassium permanganate per liter of acetic acid solution to be treated;

preferably, the potassium permanganate is added in an amount of 1.2-1.5g of potassium permanganate per liter of acetic acid solution to be treated.

8. The method of claim 1, wherein the rectifying comprises: gradually heating the mixed reaction liquid to 117+/-0.5 ℃, keeping the temperature of 117+/-0.5 ℃, changing a fraction collecting container to collect acetic acid after the distilled fraction reaches 10-12% of the total volume of the mixed reaction liquid until 8-10% of the mixed reaction liquid remains in a distillation flask, and collecting the acetic acid in the container to be purified acetic acid;

preferably, the mixed reaction solution is gradually warmed up at a warming rate of 3-3.5 ℃/min.

9. The method of claim 8, wherein the rectifying comprises: and (3) regulating the voltage of the heating sleeve to 150V, replacing the fraction collecting container after the received head fraction reaches 10-12% of the total volume of the mixed reaction liquid, and regulating the voltage to 220V until 8-10% of the mixed reaction liquid remains in the distillation flask.

10. The method of claim 1, wherein the steps of redox reaction and rectification are repeated 1-3 times;

preferably, the acetic acid product has a purity of greater than or equal to 99.7%.