JP3160983B2 - Purification method of ethyl acetate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and purifying ethyl acetate from a mixture of ethyl acetate, ethyl alcohol and water obtained by a synthesis reaction of ethylene and acetic acid in the presence of a catalyst.

[0002]

2. Description of the Related Art A patent application has been filed for producing ethyl acetate by reacting ethylene and acetic acid in the gas phase using a heteropolyacid as a main catalyst (Japanese Patent Application No. 2-258233, etc.). The method of purifying the product has not been solved yet. The reaction product contains, in addition to ethyl acetate, water added for maintaining the activity of the catalyst, and ethyl alcohol as a by-product. If the ternary mixture is to be purified by a normal distillation operation, the vapor composition at the top forms a ternary azeotropic composition, and water and ethyl alcohol are removed from the bottom of the column as the feed composition changes. Due to distillation, ethyl acetate cannot be separated and purified from the mixture.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a method for efficiently recovering high-purity ethyl acetate.

[0004]

The present inventor has conducted various studies on a distillation method capable of simultaneously dehydrating ethyl acetate and de-ethyl alcohol in one distillation column, and as a result, provided a specific reflux system. It has been found that high-purity ethyl acetate substantially free of water and ethyl acetate can be obtained from the bottom of the distillation column by adding and injecting water into the recovery section of the distillation column.

[0005] The gist of the invention is that ethyl alcohol has a concentration range of 45 wt% or less with respect to ethyl acetate,
In a method for separating and refining ethyl acetate from a mixture of ethyl alcohol and water, a single distillation column is used, and a distillate having an azeotropic composition or a composition close to the azeotropic composition is distilled from the top of the distillation column. The mixture is condensed by a condenser, and the two liquid phases generated by the condensation are separated.Then, only the poor water phase, which is mostly ethyl acetate, is refluxed to the distillation column. The method for purifying ethyl acetate is characterized by obtaining ethyl acetate containing almost no ethyl alcohol and water. Hereinafter, specific examples of the constitution of the present invention will be described with reference to FIGS.

In FIG. 1, a mixture of ethyl acetate, ethyl alcohol and water in which ethyl alcohol is in a concentration range of 45% by weight or less based on ethyl acetate is supplied from a raw material supply pipe 1 and the mixture is distilled by a distillation column. It is intended to recover high-purity ethyl acetate through the bottom extraction pipe 7. In this case, the ethyl alcohol in the top distillate in the top extraction pipe 8 has the above ternary azeotropic composition. In the vicinity of this composition, ethyl acetate behaves as a low-boiling component with respect to ethyl alcohol. Cannot be removed.

In the present invention, attention was paid to the fact that the top distillate separated into two phases after cooling, and that the ethyl alcohol concentration in the rich water phase was higher than the ethyl alcohol concentration in the poor water phase. The liquid is led to a decanter 20 through a top distillate discharge pipe 8 as in 1 and separated into two phases by a weir 21. During the two phases,
The decanter rich water phase 3 is discharged through the rich water extraction pipe 4, while the decanter poor water phase 2 is partially refluxed to the top of the tower through the poor water reflux pipe 6, and the remainder is poor. It is discharged through the phase extraction pipe 5. In the reflux of the poor water phase alone, the ratio of the water concentration to the ethyl alcohol concentration in the poor water phase is larger than that in the case of the concentration of the ternary azeotropic composition. At the top of the tower, there is no shortage of water required for the ternary azeotropic composition.

[0008] Accordingly, the reflux of only the poor-water phase reflux pipe 6 causes a change in the relative volatility of ethyl acetate and ethyl alcohol. Purified ethyl acetate is obtained.

[0009] As the water concentration in the ternary mixture from the raw material supply pipe 1 decreases, the tower top becomes insufficient in water in the ternary azeotropic composition. If a part of the rich water phase 3 is refluxed in the column, high-concentration ethyl alcohol in the separated rich water phase is returned to the column again, which is not an effective method.

Therefore, in order to compensate for the water shortage, a water injection pipe 9 is provided at the lower collecting section from the raw material supply stage. At this time, ethyl alcohol falls into the collecting section due to delicate behavior of the tower. In addition, the formation of a ternary azeotropic system by the addition of water also has the effect of raising ethyl alcohol to the concentration section, and the amount of water injected is detected by installing an ethyl alcohol detector in the recovery section. It can be controlled by feeding back the concentration to the amount of water injected.

With respect to the composition of the ternary mixture, when the ethyl alcohol concentration is 45 wt% with respect to ethyl acetate, that is, when the ethyl alcohol contains more than the binary azeotropic composition of ethyl alcohol and ethyl acetate, the above-mentioned distillation method: Even if water is added to and injected into the distillation column recovery section, ethyl acetate cannot be obtained from the bottom of the column, and therefore, ethyl acetate cannot be purified from the ternary mixture.

The composition and temperature of the azeotropic point of the above ternary and binary mixtures at normal pressure are as follows: ethyl acetate-ethyl alcohol-water (82.6 wt%, 8.4 wt%, 9.0 wt%): 70 .2
Ethyl acetate-ethyl alcohol (69.0 wt%, 31.0 wt%): 71.8 ° C Ethyl alcohol-water (96.0 wt%, 4.0 wt%): 78.2 ° C Water-ethyl acetate (91.5 wt%) %, 8.5 wt%): 70.4 ° C. The boiling point of the pure substance is ethyl acetate: 76.8 ° C. ethyl alcohol: 78.3 ° C. water: 100.0 ° C.

[0013]

【Example】

(Example 1) The ternary mixture was purified using an Oldershaw type rectifier having an inner diameter of 50 mm and having the structure shown in FIG. The mixed solution (94.6% by weight of ethyl acetate, ethyl alcohol 2.10) preheated from the raw material supply pipe 1 to the upper stage 10 for 20 stages, the middle stage 11 for 10 stages, and the lower stage 12 for 15 stages.
(0% by weight, 3.4% by weight of water). In the distillate from the top, the composition of the poor water phase 2 was ethyl acetate 87.
2 wt%, ethyl alcohol 6.1 wt%, water 6.7 wt%. When 117 parts by weight of this was refluxed to the column through the poor-water phase reflux pipe 6, substantially no water and ethyl alcohol were contained from the bottom of the column. Ethyl acetate was obtained.

(Embodiment 2) Using the same apparatus as in Embodiment 1, a mixed liquid (ethyl acetate 9
4.3wt%, ethyl alcohol 3.3wt%, water 2.1wt
%) Was supplied, and 4 parts by weight of preheated water was further supplied from the water injection pipe 9 in the tower recovery section. In the distillate from the top of the column, the composition of the poor phase 2 was 87.7 wt% of ethyl acetate.
%, Ethyl alcohol 5.7 wt%, and water 6.5 wt%. When 173 parts by weight of this was refluxed to the column through the poor-aqueous phase reflux pipe 6, substantially no water and ethyl alcohol were contained from the bottom of the column. Ethyl acetate was obtained.

[0015]

According to the present invention, it has become possible to efficiently separate and purify ethyl acetate from a mixture of ethyl alcohol, water and ethyl acetate obtained in the above-mentioned reaction route.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a specific embodiment of the present invention when an in-column condenser is used.

FIG. 2 is an explanatory view showing a specific embodiment of the present invention when an extra-column condenser is used.

[Explanation of symbols]

 Reference Signs List 1 raw material supply pipe 2 decanter poor water phase 3 decanter rich water phase 4 rich water phase extraction pipe 5 poor water phase extraction pipe 6 poor water phase reflux pipe 7 tower bottom extraction pipe 8 tower top extraction pipe 9 water injection pipe 10, 11, 12 tower 13 reboiler 14 overhead condenser 15 external condenser 20 decanter 21

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-140036 (JP, A) JP-A-54-52025 (JP, A) JP-A-4-139149 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C07C 69/12-69/14 C07C 67/54 C07C 67/04-67/055

Claims (2)

(57) [Claims] 1. A method for separating and purifying ethyl acetate from a mixture of ethyl acetate, ethyl alcohol, and water in which ethyl alcohol is in a concentration range of 45% by weight or less with respect to ethyl acetate, using one distillation column, A distillate having an azeotropic composition or a composition close thereto is distilled off from the top of the column, and the mixture is condensed by a condenser, and the two liquid phases generated by the condensation are separated. A method for purifying ethyl acetate, characterized in that ethyl alcohol containing almost no water and ethyl acetate containing almost no water are obtained from the bottom of the distillation column by refluxing only the poor aqueous phase, whose part is ethyl acetate, to the distillation column. 2. The distillation apparatus according to claim 1, wherein water is added and injected from a raw material supply stage of the distillation column to a lower distillation column recovery section to prevent ethyl alcohol from distilling from the bottom of the column. For the purification of ethyl acetate.