JPS5822015B2 - Continuous production method of glycerin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a glycerin production process using a reactive distillation method in which glycidol is produced by the reaction of peracetic acid and allyl alcohol, and glycerin is continuously produced by a hydrolysis reaction. The present invention relates to a method for efficiently recovering and reusing a portion of allyl alcohol and water.

It is described in Japanese Patent Publication No. 44-28883 that glycerin is continuously produced by a reactive distillation method in which peracetic acid, allyl alcohol, and water are continuously charged into a distillation column.

In this method, glycerin is produced continuously using a reactive distillation column. Peracetic acid is charged as a lower fatty acid ester solution to the middle stage of the distillation column, allyl alcohol is fed from the lower stage, and water is fed to peracetic acid from the lower stage. It is placed in the upper layer than the one in which it is prepared.

The lower fatty acid ester, which is the solvent for peracetic acid charged in the tower, azeotropes with water, causing most of it to rise upward from the peracetic acid charging stage, and is distilled out from the top of the tower azeotropically with water. do.

On the other hand, peracetic acid descends inside the tower and reacts with allyl alcohol charged from below to form glycidol.The generated glycidol also reacts with the water present and a portion of it becomes glycerin within the tower.

The water charged into the tower is not only necessary for the glycidol hydrolysis reaction, but also to adjust the concentration of peracetic acid and allyl alcohol so that the reaction proceeds smoothly in the aqueous medium, and to remove unreacted peracetic acid and allyl alcohol. It is also necessary to take out the bottom liquid without distilling it off to the top of the column.

Therefore, it is desirable to use an upper limit of the amount of water that is greater than or equal to the amount required to participate in these effects, and that does not cause any economic disadvantage in the subsequent treatment. 10 to 100 moles, preferably 20
It is said that it is better to use ~50 times the amount by mole.

The amount of allyl alcohol to be used may theoretically be equimolar to peracetic acid, but it is desirable to use an excess of allyl alcohol in order to complete the reaction of peracetic acid.

If peracetic acid remains as an unreacted substance, it is difficult to recover peracetic acid from the aqueous glycerin solution in a safe and reusable state, and it is not possible to decompose it and recover it as acetic acid. However, it is economically disadvantageous.

Therefore, in order to complete the reaction of peracetic acid, it is preferable to use allyl alcohol in excess, and the amount is preferably 10 to 1.20 times the mole of peracetic acid.

On the other hand, if allyl alcohol remains as an unreacted substance, it can be recovered in a reusable state by distillation.

In the present invention, a lower fatty acid ester solution of peracetic acid and allyl alcohol are charged into a first distillation column, water is added above the column, and an azeotropic component of the lower fatty acid ester and water is distilled out from the top of the column. In a reactive distillation continuous glycerin production method in which allyl alcohol and peracetic acid are reacted under a catalyst, the reaction product liquid flowing out from the bottom of the distillation column is
The total amount of unreacted allyl alcohol in the product liquid and accompanying water and acetic acid are distilled off from the top of the column without refluxing, and this effluent is recycled to the reactive distillation column. This invention relates to a continuous production method for glycerin.

Next, specific embodiments of the present invention will be explained using a system diagram.

In the drawing, a solution of peracetic acid in ethyl acetate is charged to approximately the middle stage 3 of the first reactive distillation column 1, water is charged from the upper stage 2 of the same stage 3, and at the same time allyl alcohol is charged from the lower stage 4 of the stage 3. However, by heating with the heater 5, the reaction is carried out simultaneously with the distillation.

The ethyl acetate charged together with peracetic acid forms an azeotrope with a portion of the water flowing down the column and is distilled off from the top 6 of the column, and a portion is taken out to the outside of the system 7 while refluxing.

Peracetic acid comes into contact with allyl alcohol charged from part 4 in the presence of water flowing down from part 2, and reacts to produce glycidol, most of which is hydrolyzed and becomes glycerin, which is charged into the upper part of the column and flows down. The water flows down the column together with unreacted allyl alcohol and peracetic acid extracted by the water, and is taken out from the column bottom 9 as a bottoms.

Since this bottom liquor contains unreacted allyl alcohol and peracetic acid, the reactor 10 allows peracetic acid to completely react with allyl alcohol, and at the same time completes the water utilization reaction between glycidol and water.

Unreacted allyl alcohol added in excess remains in the reaction liquid flowing out from the reactor 10, and in order to recover this, the reaction liquid is charged to the top stage 12 of the second distillation column 11, It is heated by a heater 13, and most of the allyl alcohol is distilled out from the tower top 14 together with water and acetic acid.
After being condensed in the condenser 15, or uncondensed, it is circulated to the allyl alcohol charging section 4 of the first reactive distillation column 1 and reused in the reaction.

Therefore, the amounts of water and allyl alcohol charged into the aforementioned sites 2 and 4 are reduced by an amount commensurate with this circulating amount.

Glycerin and acetic acid after distilling off 71J alcohol,
A liquid mainly composed of water is extracted from the bottom of the tower 17, and in the subsequent purification process, acetic acid, water, and other by-products are separated from the aqueous solution by extraction, distillation, evaporation, etc., and high-purity glycerin is extracted. get.

□ In the continuous production method of glycerin described above, the amount of heat required for operations such as distillation and evaporation in the final glycerin separation step is proportional to the amount of water and acetic acid contained in the aqueous glycerin solution. The smaller the amount of water that the aqueous glycerin solution brings into the final separation step, the better.

However, as mentioned above, a sufficient amount of water is required at the reaction stage in order to carry out the reactive distillation smoothly.

However, the method of the present invention reduces the amount of water in the step of separating acetic acid, glycerin, and water while maintaining the required amount of water in the reaction system, thereby providing an advantageous method for producing glycerin that can save heat. This is what I did.

In the production of glycerin using a reactive distillation column, allyl alcohol is used in excess of peracetic acid in order to effectively utilize peracetic acid.

Therefore, in the purification process, distillation is first required to remove allyl alcohol.

Allyl alcohol is a reaction raw material and can be reused by being purified and recovered. Generally, the reaction product liquid is charged from the middle stage of the distillation column, allyl alcohol is recovered from the top of the column, and other components are collected from the column. Let it flow out from the bottom.

In this distillation, in order to completely recover allyl alcohol and prevent other components such as acetic acid from distilling out, reflux is taken at the top of the column, and the partially extracted allyl alcohol is recycled to the reactive distillation column. This is the usual method used.

In the present invention, in the recovery distillation of allyl alcohol, the charging stage is placed at the top of the column, and no reflux is performed at all.

For this reason, it is necessary to increase the amount of distillate at the top of the column under distillation conditions so that allyl alcohol in the charged reaction solution is not included in the bottoms, and as a result, the concentration of allyl alcohol decreases. The amount of acetic acid and water distilled increases, but glycerin is not distilled out.

The components distilled from the top of the column are recycled and reused into the reactive distillation column from the allyl alcohol charging section of the reactive distillation column after being condensed or uncondensed.

This increases the amount of water and acetic acid charged together with allyl alcohol compared to the case where only allyl alcohol is recovered and reused, but both of these are originally present in large quantities in the tower, and the increase in the amount of water and acetic acid increases the reaction rate. No influence was observed at all.

In this way, in the recovery distillation of allyl alcohol, by distilling water at the same time as allyl alcohol, the amount of heat required in the recovery column can be reduced compared to when allyl alcohol is purified and recovered by taking reflux. It is an industrially valuable method that increases the extraction efficiency when extracting and recovering acetic acid by increasing the acetic acid concentration by reducing the water in the liquid, and also reduces the amount of heat that should be used for evaporation of water in the separation of glycerin and water. That's an expensive way.

Examples and comparative examples are shown below to clarify the embodiments and effects of the present invention.

(All parts and % represent parts by weight and % by weight.) Example 2 23.8 parts of allyl alcohol was stored in the second stage from the bottom of the first distillation column 1 having 5 plates. A distillation column for recovering allyl alcohol. Allyl alcohol recovered in 2: 9.13%
, 48.1 parts of the recovered solution containing 8.96% acetic acid were combined at 71.9 parts per hour, and in the 10th stage, a solution of peracetic acid in ethyl acetate with a concentration of 36.1% containing 12.1% acetic acid was added at 84 parts per hour. .0
Reactive distillation was carried out at a reflux ratio of 1.0 under reduced pressure at a column top pressure of 150 iiHg while continuously charging 170.6 parts of water per hour into the same 20th stage.

A 94.5% aqueous solution of ethyl acetate flows from the top of the column at a rate of 46.0% per hour.
280.4 parts per hour was extracted from the bottom of the column as bottoms.

The bottoms were further continuously charged into a water addition reactor and kept at 70°C for 45 minutes.

The thus obtained glycerin 11.82% and acetic acid 13.
7% of allyl alcohol and 1.57% of allyl alcohol.
Charged to the top stage of the second distillation column 11 having several plates,
Tower top pressure is 150 Hg, tower top temperature is 60.0°C, tower bottom temperature is 80°C.
．． The aqueous solution containing 9.13% allyl alcohol and 8.96% acetic acid is distilled out from the top of the column at 0°C through a column condenser at the rate of 48.1 parts per hour, and is then recycled to the reactive distillation column for reuse as described above. 232.3 parts per hour of bottoms containing 14.27% glycerin and 14.63% acetic acid were extracted.

Comparative Example An aqueous solution containing 23.8 parts of allyl alcohol and 30.5% of allyl alcohol distilled from the top of the distillation column 11 was added to the second stage from the bottom of the first distillation column 1, which is the same as in the example, at 94%. 7
38.5 parts per hour in total, 12.1 parts per hour in the 10th stage.
84.0 parts per hour of a solution of peracetic acid in ethyl acetate with a concentration of 36.1%, and 200 parts of water per hour in the 20th stage.
Reactive distillation was carried out under reduced pressure and a reflux ratio of 1.0 at a tower top pressure of 150 Hg while continuously charging 0 parts of each.

A 94.5% aqueous solution of ethyl acetate flows from the top of the tower at a rate of 46.0% per hour.
276.5 parts per hour were extracted from the bottom of the distillation column as bottoms.

The bottom solution was further continuously kept at 70° C. for 45 minutes in a water reactor to obtain a reaction product solution containing 11.8% glycerin, 12.3% acetic acid, and 1.6% allyl alcohol.

This was charged into the 10th stage from the top of the second distillation column 11 having 50 plates, and the top pressure was reduced to 150 Hg.
With a reflux ratio of 4.0, the tower top temperature was 56°C and the tower bottom temperature was 80°C.
The aqueous solution containing 30.5% allyl alcohol was distilled out from the top of the column at 14.8 parts per hour through a condenser at the top of the column, and 12.7% glycerin, 13% acetic acid, and 13% acetic acid were distilled from the bottom of the column.
261.7 parts of bottom liquid containing 0% was extracted.

Therefore, the amount of distillation steam used in the second distillation column 11 in the example was 14.0% less than in the comparative example, and the The amount of water in the example is 15.0% less.

[Brief explanation of drawings]

The drawing is a system diagram for concretely carrying out the continuous production method of glycerin according to the present invention. 1... First reactive distillation column, 11... Second reactive distillation column.

Claims (1)

[Claims] 1. A lower fatty acid ester solution of peracetic acid and allyl alcohol are charged into the first distillation column, water is added above the column, and the azeotropic components of the lower fatty acid ester and water are distilled out from the top of the column without a catalyst. In a reactive distillation continuous glycerin production method in which allyl alcohol and peracetic acid are reacted, the reaction product liquid flowing out from the bottom of the reactive distillation column is
The total amount of unreacted allyl alcohol in the product liquid and accompanying water and acetic acid are distilled from the top of the column without refluxing, and this distillate is circulated to the reactive distillation column. A continuous production method for glycerin characterized by reuse.