JPH0635418B2 - Purification method of acetic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for purifying acetic acid using peracetic acid, that is, by adding peracetic acid to acetic acid having a short potassium permanganate test retention time at a temperature in the range of 50 ° C. to 120 ° C. The present invention relates to a method for purifying acetic acid, which comprises performing a heat treatment for 1 to 20 hours and then distilling it. As an industrial production method of acetic acid, a method by oxidation of acetaldehyde, a method by direct oxidation of petroleum naphtha or butane, propane, etc., olefins and peracetic acid or unsaturated alcohols and peracetic acid (peracetic acid in these cases is Acts as an oxygen introducing agent)
There is a method of purifying by-product acetic acid when epoxide is synthesized from, a method of directly synthesizing from methanol and carbon monoxide, etc. However, since various impurities are generally mixed in these synthetic acetic acid, Purifying this acetic acid is rather cumbersome.

In particular, the value of the acetic acid product is lost even if a reducing substance is contained in the acetic acid product in an extremely small amount. Conventionally, as a measure of the content of reducing substances in acetic acid, the acetic acid product analysis standard includes the potassium permanganate test method, and the discoloration retention time in this case is 5 minutes or more as a general acetic acid product standard. Depending on the application, a holding time of potassium permanganate of 60 minutes or more is required.

Previously, the applicant of the present invention was found to have an excellent purification method for acetic acid (Japanese Patent Publication No.
-30615) was proposed, which was a method of obtaining acetic acid having a long retention time in the potassium permanganate test by distilling while adding peracetic acid. However, even this method was not effective at all with respect to some by-product acetic acid.

Therefore, as a result of intensive studies by the present inventors, the fact that the above-mentioned method makes contact between purified acetic acid and peracetic acid only in the distillation column (short contact time) has been clarified. The present invention has been completed.

According to the method of the present invention, a small amount of peracetic acid was added to acetic acid as a raw material before charging to a distillation column as a pretreatment, and the mixture was maintained at a constant temperature for a predetermined time and then purified by distillation. First of all, it has become possible to obtain pure good acetic acid that can sufficiently pass this test even with acetic acid having a short retention time of potassium permanganate.

The peracetic acid used in the present invention is diluted with a solvent such as acetic acid or ethyl acetate and used as a 20 to 40% solution. The addition amount of peracetic acid is selected from the range of 0.1% to 5% by weight with respect to the acetic acid to be purified, but the addition amount of peracetic acid should be an appropriate amount according to the quality of each acetic acid to be purified. Is advantageous.

In the heat treatment of the present invention, the temperature is in the range of 50 to 120 ° C, and the time is selected as a function of the temperature. For example, 50 ℃
If so, it takes about 20 hours, and at 120 ° C, it takes about 1 hour. Therefore, these processing conditions (amount of peracetic acid added and heating temperature,
Since the time) is influenced by the content of the reducing substance in the acetic acid to be purified, it should be appropriately determined from experiments.

In distillation, a usual distillation purification method is adopted. First, the first purification distillation is performed, and a trace amount of a low boiling point component in acetic acid and a peracetic acid solvent are distilled from the top of the column. Further, this kettle liquor is subjected to the second purification distillation to obtain pure good acetic acid having a long potassium manganate test retention time as a product from the top of the column.

Since the added peracetic acid is thermally decomposed during the heat treatment and distillation and converted into the same acetic acid as the product, no extra separation and purification is required.

Examples and comparative examples that clarify the effects of the present invention will be shown below.

Example 1. 3000 g of acetic acid by-produced in the synthesis of ε-caprolactone was charged into a heatable container 5 equipped with a stirrer and a condenser, and 9% of peracetic acid diluted to 30% with ethyl acetate and acetic acid was charged.
g (net amount of peracetic acid) is added. The internal temperature is raised to 120 ° C., and the mixture is further stirred for 1 hour at the same temperature.

Next, the above liquid is continuously distilled at atmospheric pressure. First, in the first purification tower (inner diameter 50φ, 60 tray tray tower), the above-mentioned peracetic acid treatment liquid was continuously charged at a rate of 100 g / H at the 50th tray from the bottom of the tower, and the reflux ratio was set to 30 at the top of the tower. From ethyl acetate 6.3%
The acetic acid containing is distilled off at 10 g / H.

Furthermore, acetic acid was continuously withdrawn from the bottom of the column at 90 g / H and supplied to the second purification column. In the second purification tower (inner diameter 50φ, 40 tray tray tower), the can extractor from the first purification tower was charged at the 20th tray from the bottom of the tower at a rate of 90 g / H, and the reflux ratio was 2, and 85 g from the top of the tower. The product acetic acid was distilled off at / H. The product acetic acid thus obtained was tested for potassium permanganate in a result of 150 minutes.

Comparative Example 1. The continuous distillation was performed in the same manner as in Example 1 except that the by-product acetic acid of Example 1 was not heat-treated by adding peracetic acid. The result of the potassium permanganate test of the resulting product acetic acid was zero minutes.

Example 2. The same procedure as in Example 1 was carried out except that the heating after the addition of peracetic acid in Example 1 was carried out at 50 ° C. for 20 hours. The result of potassium permanganate test on the resulting product acetic acid was 65 minutes.

Example 3. The same procedure as in Example 1 was carried out except that the by-product acetic acid in the synthesis of C ₁₂ · C ₁₄ α-olefin oxide was used in place of the by-product acetic acid in the synthesis of ε-caprolactone of Example 1.
The resulting product, acetic acid, had a potassium permanganate test result of 70 minutes.

Comparative example 2. The continuous distillation was performed in the same manner as in Example 3 except that the by-product acetic acid of Example 3 was not heat-treated by adding peracetic acid. The result of the potassium permanganate test of the resulting product acetic acid was zero minutes.

Example 4. The same procedure as in Example 1 was carried out except that the byproduct acetic acid in the synthesis of glycerin was used in place of the byproduct acetic acid in the synthesis of ε-caprolactone in Example 1. The result of the potassium permanganate test on the resulting product acetic acid was 200 minutes.

Comparative Example 3. The continuous distillation was performed in the same manner as in Example 4 except that the byproduct acetic acid of Example 4 was not heat-treated by adding peracetic acid. The result of potassium permanganate test on the resulting product acetic acid was 95 minutes.

Claims (1)

[Claims] 1. An acetic acid characterized in that peracetic acid is added to acetic acid having a short holding time for potassium permanganate test, the mixture is heated at a temperature in the range of 50 ° C. to 120 ° C. for 1 to 20 hours, and then distilled. Purification method