JPH05186391A - Method for purifying ethyl acetate - Google Patents

Abstract

PURPOSE:To separate ethyl alcohol from a mixture composed of the ethyl alcohol, water and ethyl acetate and further convert the ethyl alcohol into ethyl acetate. CONSTITUTION:A mixture composed of ethyl alcohol, water and ethyl acetate is introduced into an extractive distillation column 1 and water as an extracting agent 13 is added to separate and remove the ethyl acetate. The ethyl alcohol is then concentrated with a distillation column 11, together with acetic acid 23, is introduced into a reactor 22 filled with an acidic catalyst 21 to convert the ethyl alcohol into ethyl acetate, which is recovered as a reactional product liquid 24. In the process for producing the ethyl acetate, the ethyl alcohol which is a reactional by-product is readily separated and further subjected to esterifying reaction. Thereby, the objective ethyl acetate can be recovered as the product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates ethyl alcohol from a mixture of reaction products, that is, ethyl acetate, ethyl alcohol and water, by the reaction of synthesizing ethylene and acetic acid in the presence of a catalyst. , A method for purifying ethyl acetate which is converted into ethyl acetate and recovered.

[0002]

2. Description of the Related Art A patent has been filed for producing ethyl acetate by reacting ethylene and acetic acid in a gas phase using a heteropoly acid as a main catalyst (Japanese Patent Application No. 2-258233, etc.). In addition to ethyl acetate, the product contains water added for maintaining the activity of the catalyst, and further contains ethyl alcohol as a by-product.For the method of treating ethyl alcohol produced by the reaction at the industrial level, It has not been resolved yet.

[0003]

When purifying ethyl acetate from the above reaction product mixture, it is necessary to separate and remove the by-product ethyl alcohol, and also to select the reaction for the by-product ethyl alcohol. When the property is high, the method for producing ethyl acetate via the above reaction does not hold at the industrial level. In order to solve the above problems, the present invention aims to efficiently separate the ethyl alcohol and then convert it into ethyl acetate.

[0004]

The present invention has been made to achieve the above object, and its gist is to separate and concentrate ethyl alcohol, which is a by-product, and then add acetic acid,
In this method, an esterification reaction is carried out by introducing it into a reactor filled with an acid catalyst to convert ethyl alcohol into ethyl acetate. Hereinafter, description will be given with reference to the drawings. FIG. 1 shows an example for carrying out the present invention.

First, the raw material 2, which is a ternary mixture of ethyl acetate, water, and ethyl alcohol, is introduced into the extractive distillation column 1, and water 13 as an extractant is supplied from the upper part of the column to convert ethyl alcohol into water. It was extracted and distilled. At this time, the greater the amount of water used for extraction,
Ethyl alcohol is easily extracted, but in practical use,
Roughly, the amount of ethyl alcohol and ethyl acetate supplied to the extractive distillation column is about 10 times the molar amount, and ethyl acetate distilled from the top of the extractive distillation column 1 and azeotropically distilled water are added. Is desirable. From the column bottom 4 of the extractive distillation column 1, water and ethyl alcohol as extractants are extracted and introduced into the next distillation column 11. By the above operation, in the extractive distillation column 1, ethyl alcohol is separated from ethyl acetate.

In the distillation column 11, concentrated ethyl alcohol having an azeotropic composition with water is obtained from the top 12 of the column. On the other hand, water with a high boiling point is extracted from the bottom 14 and can be reused as an extractant for the extractive distillation column 1. However, a part 15 of the bottom liquid 14 is The water in the top liquid 3 of the extractive distillation column 1 and the water in the top liquid 12 of the distillation column 11 are discharged in an amount corresponding to the subtracted amount.

Acetic acid 23 is newly added to the overhead liquid 12 which is ethyl alcohol concentrated in the distillation column 11 and is introduced into the reactor 22 filled with the acid catalyst 21.
In the reactor, ethyl acetate and water are obtained from ethyl alcohol and acetic acid by the following equilibrium reaction. The necessity of the extractive distillation column 1 and the distillation column 11 is to advance the reaction to the ethyl acetate producing side in the equilibrium reaction. The mixture of the overhead liquid 12 and the acetic acid 23 is passed through the reactor 22, and the ethyl alcohol in the overhead liquid 12 is converted into ethyl acetate as the reaction product liquid 24 and recovered according to the following equilibrium constant. As the acid catalyst, a mineral acid such as sulfuric acid, a strongly acidic ion exchange resin, a heteropoly acid such as phosphotungstic acid, or the like can be used in the reactor 22.

Reaction formula: C ₂ H ₅ OH + CH ₃ COOH = CH ₃ COOC ₂ H ₅
+ H ₂ O Equilibrium constant:

[Equation 1] The unreacted acetic acid in the reaction product liquid 24 is easily separated as a high boiling point from ethyl alcohol and ethyl acetate by distillation, and can be reused as the above-mentioned added acetic acid 23.

[0009]

【Example】

(Example 1) Inner diameter 50 mm, concentrating section 20 stages, collecting section 25
In order to carry out the extractive distillation by using the Aldershaw of the stage, 100 parts by weight of the raw material having the composition 2 was introduced, and water as the extractant was fed from the first stage from the top of the tower to obtain 150 parts by weight of the composition 4. A bottom liquid was obtained. The bottom liquid was purified using Oldershaw having an inner diameter of 50 mm, a concentrating section of 20 stages, and a collecting section of 25 stages. As a result, 10 parts by weight of ethyl alcohol having a composition of 12 was obtained from the top of the column. Further, 26 parts by weight of acetic acid having a composition of 23 was added to the ethyl alcohol, and the mixture was passed through a reactor filled with Mitsubishi PK-212H, a commercially available cationic ion exchange resin. 36 parts by weight of the recovered liquid were obtained. At this time, the addition ratio of ethyl alcohol in the raw material liquid to ethyl acetate was 74.0 at the reactor outlet.
%Met. Table 1 shows the composition of each part. The composition numbers represent the same parts as the numbers shown in FIG.

[0010]

[Table 1]

(Example 2) Using the same distillation apparatus and reaction apparatus as in Example 1, the composition of raw materials was changed, and the composition at each part was as shown in Table 2. At this time, the conversion rate of ethyl alcohol in the raw material liquid to ethyl acetate was 77.7% at the reactor outlet.

[0012]

[Table 2]

[0013]

EFFECT OF THE INVENTION By-product ethyl alcohol was easily separated and could be recovered as the product ethyl acetate.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

[Explanation of symbols]

 1 Extractive distillation tower 2 Raw material supply 3 Extraction tower Low boiling point 4 Extraction tower High boiling point 11 Distillation column 12 Low boiling point 13 Extractor 14 High boiling point 15 Part of bottom liquid 21 Catalyst 22 Reactor 23 Additive 24 Reaction production liquid

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Iizuka No.2 Nakasu, Oita City, Oita Prefecture Showa Denko Oita Factory

Claims (2)

[Claims] 1. A ternary system of ethyl acetate, ethyl alcohol and water in a reaction liquid obtained by reacting ethylene with acetic acid and water added to maintain the activity of the catalyst in the presence of a catalyst is placed in an extractive distillation column. A method for purifying ethyl acetate, in which water is introduced as an extractant and ethyl alcohol is extracted into water to obtain an azeotrope of ethyl acetate and water from the top of the tower and a mixture of ethyl alcohol and water from the bottom of the tower. 2. A mixture of ethyl alcohol and water, which is the bottom liquid of claim 1, is introduced into a distillation column to obtain concentrated ethyl alcohol from the top of the column, and then the concentrated ethyl alcohol is charged with an acid catalyst. It is introduced into the reactor described above, and acetic acid is added to convert the ethyl alcohol to ethyl acetate by an esterification reaction.