JPH09286748A - Dehydropurification of aqueous alcohol solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for the subject dehydropurification having a good dehydration effect with a minimal thermal energy without deposition of any salt.

SOLUTION: First, at least one kind of potassium salt 2 selected from at least dipotassium hydrogenphosphate, potassium phosphate, potassium pyrophosphate, potassium (poly)triphosphate and potassium carbonate is added to an aqueous 2-4C saturated or unsaturated alcohol solution 1. Subsequently, the resultant aqueous alcohol solution is separated into an aqueous phase 5 and organic phase 6, the aqueous phase 5 is removed, and the potassium ions in the organic phase is removed by using a cationic ion exchange resin.

COPYRIGHT: (C)1997,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for dehydrating and purifying an aqueous alcohol solution, and more specifically,
The present invention relates to a dehydration purification method for a saturated alcohol or unsaturated alcohol aqueous solution having 2 to 4 carbon atoms.

[0002]

2. Description of the Related Art Most of the methods used for dehydration and purification of aqueous alcohol solutions have long been distillation. Distillation requires a lot of heat energy,
Further, since alcohol forms an azeotropic mixture with water, no good effect can be obtained by separating and purifying only by fractional distillation.

As a method for dehydrating alcohol from an azeotropic aqueous solution, an extractive distillation method or an azeotropic distillation method is used. A method has been considered in which the equilibrium of the gas-liquid phase or the composition of the azeotrope is changed by adding another solvent to break the composition of the azeotrope during distillation to enhance the effect of separation and purification. However, both extractive distillation and azeotropic distillation consume a great deal of heat energy during heating and boiling, and the third solvent must be separated.

As a method of dehydrating from an aqueous alcohol solution, there is a method of adjusting the pressure to change the composition of the azeotropic mixture to enhance the separation effect. However, when allyl alcohol is used, even if the pressure is changed, the composition of the azeotrope does not change much and its effect is not recognized.

It is also known that when salts are added to an aqueous alcohol solution, the aqueous alcohol solution separates into two phases, an aqueous phase and an organic phase, and some do not separate, depending on the type of the salt. If the salts are easily soluble in water and alcohol, the aqueous alcohol solution is unlikely to form two phases. When the salt is easily soluble in water and insoluble in alcohol, the aqueous alcohol solution is separated into two phases. It is recognized that salts that are difficult to separate into two phases even when added to an aqueous alcohol solution, such as potassium acetate, can change the equilibrium of the gas-liquid phase, break the azeotropic phenomenon, and enhance the effect of separation and purification. It has the drawback of requiring heat energy. On the other hand, in the case of salts that can separate an aqueous alcohol solution into two phases, and when the water content in the organic phase can be reduced, it is also possible to separate into an aqueous phase and an organic phase to obtain an organic phase with a low water content. .

[0006] Taiwan Patent Publication No. 84211 reports a method for dehydrating allyl alcohol using potassium salts such as dipotassium hydrogen phosphate, potassium phosphate, potassium pyrophosphate, potassium triphosphate and potassium carbonate. However, the organic phase obtained by dehydration by this method is a low-water content allyl alcohol aqueous solution containing a small amount of potassium salt, further distillation, to obtain an azeotropic composition at the top of the rectification column, the bottom of the column There is a trace amount of water-containing allyl alcohol and potassium salt, and precipitation of potassium salt is observed. In order to separate this allyl alcohol salt and potassium salt, a highly efficient rectification column is added and rectified to obtain highly purified allyl alcohol purified from the top of the column, but at the bottom of the column. Since allyl alcohol and potassium salt are present, the problem of potassium salt precipitation remains, and a large amount of heat energy is required, and industrial production is difficult and there is a problem in practical use.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for dehydrating and refining an aqueous alcohol solution which does not cause salts to precipitate and which can obtain a good dehydrating effect with a minimum of heat energy.

[0008]

In view of the above problems, the inventors of the present invention have conducted diligent research to find a method for dehydration purification of a useful aqueous alcohol solution. By removing the potassium ions in the organic phase, it was found that the potassium ion concentration was suppressed to a very small amount, and that a highly concentrated aqueous alcohol solution did not affect the efficiency of ion exchange and could be reused continuously. It is possible to improve the problem and save a great deal of heat energy of the rectification column for separating the alcohol and the potassium salt. The present invention has been completed based on this finding.

That is, the present invention is intended to provide a method for dehydrating and purifying an aqueous alcohol solution, and more specifically, at least hydrogen phosphate in an aqueous solution of a saturated or unsaturated alcohol having 2 to 4 carbon atoms. Dipotassium,
After separating the aqueous alcohol solution into two phases, an aqueous phase and an organic phase, by adding one kind of potassium salt selected from potassium salts such as potassium phosphate, potassium pyrophosphate, potassium triphosphate and potassium carbonate, the aqueous phase is separated. A high-purity alcohol by removing potassium ions in the organic phase using a cation-based ion-exchange resin, and further distilling the organic phase, if necessary. To do.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for dehydrating and purifying an aqueous alcohol solution, and more specifically, to an aqueous solution containing a saturated or unsaturated alcohol having 2 to 4 carbon atoms, at least dipotassium hydrogen phosphate, By adding one type of potassium salt selected from potassium salts such as potassium phosphate, potassium pyrophosphate, potassium triphosphate and potassium carbonate, the alcohol aqueous solution is separated into two phases, an aqueous phase and an organic phase, and the aqueous phase is separated. The method includes a method of obtaining a high-purity alcohol by removing the potassium ion in the organic phase by using a cation-based ion exchange resin, and further distilling the organic phase, if necessary.

According to the dehydration purification method of the present invention, not only does the problem of precipitation of salts occur during distillation, but also the dehydration effect of the aqueous alcohol solution is improved by using the minimum heat energy, and further the method of the present invention. Thus, the azeotropic point of the aqueous alcohol solution is broken, and the alcohol is purified based on this.

Examples of the potassium salts used in the method of the present invention include potassium carbonate, dipotassium hydrogen phosphate, potassium phosphate, potassium pyrophosphate, potassium triphosphate, etc. These salts are solid or aqueous solutions. Then, the mixture is added to the aqueous alcohol solution, mixed and stirred, and then allowed to stand to separate into an aqueous phase and an organic phase. Further, examples of the potassium salts include anhydrous ones and those containing crystal water.

With respect to the amount of the potassium salt used in the method of the present invention, the concentration of the potassium salt present in the lower aqueous phase after separating the alcohol aqueous solution is preferably 20 to 70% by weight. When the concentration of the potassium salt used reaches a supersaturated concentration, precipitation of salts is likely to occur, which causes an obstacle to the purification operation.

As the cation-based ion exchange resin used in the method of the present invention, an H-type cation-based ion exchange resin is used. For example, a cation-based ion exchange resin having a styrene / diethylenebenzene resin as a skeleton and an acidic active functional group such as a sulfonic acid group bonded thereto can be cited. Examples thereof include Dow Chemical Company.
l Co. ) The product Dowex HCR-S type cation exchange resin may be mentioned. Further, for example, a cation exchange resin having a sulfonic acid group active functional group such as styrene / diethylenebenzene / pore type, for example, Dowe manufactured by Dow Chemical Company.
A xMSC-1 type cation exchange resin is also used.

By treatment with the above cation exchange resin, the concentration of potassium ions in the organic phase is lowered to 20 ppm or less, and precipitation of potassium salts is not observed even if distilled to further enhance the purity. Compared with the direct distillation method for precipitating a potassium salt used in the method, it is advantageous in industrial production.

Further, according to the method of the present invention, if the water content of an alcohol aqueous solution having a very high water content as an azeotropic composition mixture is reduced to the azeotropic composition or less and potassium ions in the organic phase are removed, distillation is carried out. As a result, an alcohol having a very high purity can be obtained from the bottom portion of the rectification column, the distillation portion having an azeotropic composition close to the top portion is separated, and the latter is further subjected to reflux treatment. Further, the water phase can be recovered and used by evaporating and removing water to increase the concentration of salts.

After separation into two phases, the water content in the alcohol obtained is very low, potassium ions are removed with an ion exchange resin and the alcohol is purified by distillation. In this case, the required heat energy is much smaller than that in the conventional distillation, and there is no risk of potassium salt being deposited. Since the potassium salt used for dehydration has a very low corrosive effect on the facility, general inexpensive materials are used, which leads to cost reduction and is ideal.

FIG. 1 shows an industrial production process of the method of the present invention. The aqueous alcohol solution (1) (azeotrope composition mixture agent) and the aqueous potassium salt solution are mixed in the mixing container (A), then transferred to the separation container (B), and allowed to stand to allow the aqueous phase (5) and the organic phase (6). ) Is separated. In the organic phase (6), potassium ions are removed by an ion exchange device (D) to obtain a highly pure organic phase. If a higher-purity alcohol is required, a higher-purity alcohol (8) can be obtained by distillation in a rectification column (E), but the distillate from the top of the column is azeotropic. Since the composition is close to the composition of the mixture, it is refluxed for reprocessing. The water phase (5) is evaporated by a distillation apparatus (C) to recover the concentrated potassium salt (2), returned to the mixing container (A) and reused.

[0019]

EXAMPLES The method of the present invention will be described in more detail based on the following examples, but the invention is in no way limited by these examples.

Example 1 50 g of an aqueous alcohol solution containing 30% of water and 70% of allyl alcohol was added to 53.5% of potassium carbonate and 46.5% of water.
50 g of an aqueous solution containing the above was added, the mixed solution was heated at 40 ° C., and after stirring for 30 minutes, the mixture was allowed to stand and separated into two phases. As a result of analyzing the water content of the upper organic phase by the Karl Fischer method, the water content was 11.30%. Calculated content of allyl alcohol is 88.58%
It became. Potassium carbonate is 0.12 by atomic absorption spectrometry
It was revealed that it is%. The lower aqueous phase was found by gas chromatography to have an allyl alcohol content of 0.41%. Flow the upper organic phase at a flow rate of 2.2 ml / m
in cation exchange resin (Dowex HCR-S, 1
As a result, the potassium ion concentration became 20 ppm or less. The composition of the organic phase after the cation exchange resin treatment was 88.68% allyl alcohol, 1 part water.
It showed 1.31% and 20 ppm of potassium carbonate. When 500 g of the above mixed solution was distilled, 251 g of an aqueous solution having an allyl alcohol content of 77.9% was obtained from the top of the column, 247 g of a solution having an allyl alcohol content of 99.6% was obtained from the bottom of the column, and No precipitation was observed.

Example 2 To 50 g of an azeotropic composition aqueous solution containing 28.2% of water and 71.8% of n-propyl alcohol, 50 g of an aqueous solution containing 53.5% of potassium carbonate and 46.5% of water was added and mixed. The solution was heated at 40 ° C., stirred for 30 minutes, and then allowed to stand to separate into two phases. As a result of analyzing the upper organic phase by the Karl Fischer method, the water content was 9.6%.
Atomic absorption spectrometry revealed that the potassium carbonate content was 0.14% and the n-propyl alcohol content was 9%.
It showed 0%. The lower aqueous phase was analyzed by gas chromatography,
The n-propyl alcohol content was found to be 0.01%. As a result of treating the upper organic phase with a cation exchange resin (Dowex HCR-S, filled with 100 ml) at a flow rate of 2.2 ml / min, the potassium ion concentration was 20 ppm or less.

Example 3 To 50 g of an aqueous alcohol solution containing 30% water and 70% allyl alcohol, 60% dipotassium hydrogen phosphate and 40% water were added.
Was added to the mixture, and the mixture was heated to 40 ° C., stirred for 30 minutes, and allowed to stand to separate into two phases. The upper organic phase was analyzed by the Karl Fischer method, and as a result, it was found that the water content was 11.5%, and the atomic absorption analysis showed that the dipotassium hydrogen phosphate content was 0.01%. Admitted. Gas chromatographic analysis of the lower aqueous phase revealed that the allyl alcohol content was 0.13%. Flow rate of the upper organic phase is 2.0
Cation exchange resin (Dowex MSC) at ml / min
As a result, the potassium ion concentration became 20 ppm or less.

Example 4 50 g of an aqueous solution containing 30% water and 70% allyl alcohol
50 g of an aqueous solution containing 66.7% potassium phosphate and 33.3% water was added to the mixture, and the mixture was heated to 40 ° C.
After stirring for a minute, the aqueous solution was allowed to stand and the two phases were separated.
The upper organic phase showed a water content of 10.67% by Karl Fischer's method, and further it was found by atomic absorption spectrometry that potassium phosphate was 0.64%. Gas chromatographic analysis of the lower aqueous phase showed that allyl alcohol was 1.2%. The upper organic phase has a flow rate of 2.0 m
Cation exchange resin (Dowex MSC-
As a result, the potassium ion concentration became 20 ppm or less.

Example 5 To 50 g of an aqueous solution containing 15% water and 85% isopropyl alcohol was added 50 g of an aqueous solution containing 53.5% potassium carbonate and 46.5% water, and the mixture was heated to 40 ° C.
After stirring for 30 minutes, the aqueous solution was allowed to stand and the two phases were separated. The upper organic phase had a water content of 5.60% as determined by the Karl Fischer method. Further, atomic absorption analysis revealed that potassium carbonate contained 0.15%. Gas chromatographic analysis of the lower aqueous phase revealed an isopropyl alcohol content of 0.28%. The cation exchange resin (Dowex) was added to the upper organic phase at a flow rate of 2.0 ml / min.
As a result of the treatment with 100 ml of MSC-1), the potassium ion concentration became 20 ppm or less.

Example 6 An aqueous solution of potassium carbonate was added with 51.22% of potassium carbonate and 4 parts of water.
When treated according to the method of Example 1 except that the content was changed to 8.8%, the water content of the upper organic phase increased to 13.2%.

Example 7 The procedure of Example 1 was repeated except that the aqueous potassium carbonate solution was changed to 50% potassium carbonate and 50% water, and as a result, the water content of the upper organic phase was increased to 16.9%. did.

Example 8 An aqueous potassium carbonate solution was added to potassium carbonate 54.5% and water 4
The same procedure as in Example 1 was carried out except that the amount of water was changed to 5.5%. As a result, the water content of the upper organic phase was 10.6%.

Example 9 An aqueous potassium carbonate solution was added to potassium pyrophosphate 60% and water 4
All were treated according to the method of Example 1 except that 60 g of an aqueous solution containing 0% was used, and as a result, the water content of the upper organic phase was 13.9%.

Example 10 An aqueous solution of potassium carbonate was added to 50% potassium triphosphate and 50% water.
% Except that the amount of the aqueous solution containing 50% was changed to 50 g.
As a result of carrying out according to the method shown in, the water content of the upper organic phase was 12%.

Example 11 To 50 g of an aqueous solution containing 32% of water and 68% of sec-butyl alcohol was added 50 g of an aqueous solution containing 53.5% of potassium carbonate and 46.5% of water, and the mixture was heated to 40 ° C. After stirring for 30 minutes, the mixture was left standing and separated into two phases.
The water content of the upper organic phase was 8.0% as analyzed by the Karl Fischer method, and the potassium carbonate content was 0.23% by atomic absorption spectrometry.

Example 12 10 g of potassium carbonate was added to 50 g of an aqueous alcohol solution consisting of 24% water and 76% ethyl alcohol, and the mixture was stirred at 40 ° C. for 30 minutes and then allowed to stand to separate into two phases. The water content of the upper organic phase was 11.5% as analyzed by Karl Fischer's method, and the potassium carbonate content was 0.4% by atomic absorption spectrometry.

Comparative Example 1 All of the treatments were carried out according to the method of Example 1 except that the salt used was an aqueous potassium acetate solution containing 85.7% potassium acetate and 14.3% water, and as a result, the mixture was separated. I was not able to admit.

Comparative Example 2 Organic phase 5 containing 88.58% of allyl alcohol, 11.30% of water and 0.12% of potassium carbonate obtained in Example 1.
Directly distilling 00g without treating with cation exchange resin, an aqueous solution containing 78% of allyl alcohol was obtained from the top of the column.
52 g were obtained, and the allyl alcohol content was 99.6% from the bottom of the tower.
Although 247 g of an aqueous solution of was obtained, precipitation of potassium carbonate was observed at the bottom of the tower.

[0034]

As described above, according to the present invention,
It is possible to dehydrate and purify an aqueous alcohol solution with minimal heat energy without salt precipitation.

[Brief description of drawings]

FIG. 1 is a schematic view showing an industrial production process of the method of the present invention.

[Explanation of symbols]

1: Alcohol aqueous solution, 2: Potassium salt, 3: 4, Mixed solution of alcohol aqueous solution and potassium salt, 5: Aqueous phase, 6: Organic phase, 7: Highly pure organic phase, 8: Highly pure alcohol, 9: Distillate, A: mixing container, B: separation container,
C: Evaporator, D: Ion exchanger, E: Fractionation tower.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C07C 31/10 9155-4H C07C 31/10 31/12 9155-4H 31/12 33/02 9155- 4H 33/02

Claims (5)

[Claims] 1. An aqueous solution of saturated or unsaturated alcohol having 2 to 4 carbon atoms, which is selected from at least dipotassium hydrogen phosphate, potassium phosphate, potassium pyrophosphate, potassium (poly) triphosphate and potassium carbonate. An alcohol characterized by adding one kind of potassium salt, separating the aqueous alcohol solution into an aqueous phase and an organic phase, removing the aqueous phase, and further removing the potassium ion in the organic phase using a cation-based ion exchange resin. Method for dehydration purification of aqueous solution. 2. The method for dehydrating and purifying an alcohol aqueous solution according to claim 1, wherein after the potassium ions are removed, the alcohol is further distilled to obtain a highly pure alcohol. 3. The method for dehydrating and purifying an aqueous alcohol solution according to claim 1, wherein the potassium salt is anhydrous or contains crystal water. 4. The method for dehydrating and purifying an aqueous alcohol solution according to claim 1, wherein the potassium salt is added in the form of an aqueous solution or a solid. 5. The method for dehydration purification of an aqueous alcohol solution according to claim 1, wherein the cation-based ion exchange resin is an H-type cation exchange resin.