JP3021967B2 - Purification method of alcohol - 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 purifying alcohol. More specifically, the present invention relates to a method for purifying an alcohol by separating and recovering an alcohol from an alcohol solution containing an aldehyde.

[0002]

2. Description of the Related Art When separating and recovering high-purity alcohol from a mixed solution of aldehyde and alcohol whose boiling points are relatively close to each other, there is a problem that expensive distillation equipment having high resolution is required. In contrast, Japanese Patent Application Laid-Open No. 2-18854
No. 0 discloses a method in which the specific volatility of aldehyde and alcohol is changed by adjusting the pH of the alcohol solution to a range of 7 to 12, followed by distillation. However, this method has a problem that separation of the aldehyde from the alcohol is not sufficient, and a high-resolution distillation facility is required to remove a small amount of the aldehyde remaining in the alcohol. There is a problem that some aldehydes become heavy under alkaline conditions and block pipes and the like.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, the problem to be solved by the present invention is to solve the problems of the prior art and to convert high-purity alcohol from an alcohol solution containing aldehyde. It is an object of the present invention to provide an excellent alcohol purification method capable of efficiently separating and recovering, and not accumulating insolubles in a distillation apparatus, thereby enabling continuous stable operation for a long period of time.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention relates to a method for purifying alcohol which separates and recovers alcohol from an alcohol solution containing aldehyde, and relates to a method for purifying alcohol comprising the following steps. Alkali treatment step: A step of converting aldehyde to aldol by adding and mixing 0.2 to 5.0 parts by weight of alkali per 100 parts by weight of alcohol solution containing aldehyde. Neutralization step: Alkaline Step of neutralizing the mixture obtained in the treatment step Distillation step: The neutralized liquid obtained in the neutralization step is converted to an alcohol, aldehyde, or the like having a boiling point higher than that of the alcohol to be separated and recovered.
A step of distilling the alcohol to be separated and recovered in the presence of at least one solvent selected from the group consisting of ketones and esters

The details will be described below. The starting material to be separated and recovered in the present invention is an alcohol solution containing an aldehyde. Here, as the aldehyde,
There is no particular limitation, and examples thereof include acetaldehyde, propionaldehyde, butyraldehyde, and valeraldehyde. The alcohol is not particularly limited, and examples thereof include methanol, ethanol, propanol, butanol, amyl alcohol, hexyl alcohol, and cyclohexyl alcohol.

[0006] The alkali treatment step of the present invention is to add and mix 0.2 to 5.0 parts by weight of alkali per 100 parts by weight of an alcohol solution containing aldehyde to convert the aldehyde into aldol. This is the step of conversion. Examples of the alkali include sodium hydroxide,
Potassium hydroxide and the like. The amount of the alkali used is 0.2 to 5.0 parts by weight, preferably 0.2 to 3.0 parts by weight, per 100 parts by weight of the aldehyde-containing alcohol solution.
0 parts by weight. If the amount is too small, the reaction of the aldehyde to the aldol will not proceed sufficiently, and the separation of the aldehyde from the alcohol will be insufficient. On the other hand, if the amount is too large, insolubles are generated due to the heavy aldehyde, and the amount of acid used in the subsequent neutralization step increases, which is uneconomical. Note that the alkali may be added as a solid, but it is preferable to add the alkali as an aqueous solution or an alcohol solution from the viewpoint of operability. The concentration of the alkali at this time is not particularly limited.

The processing temperature in this step is usually 20 to 100
° C, preferably 30 to 80 ° C. If the temperature is too low, the reaction of the aldehyde to the aldol will not proceed sufficiently, while if the temperature is too high, the generation of insolubles due to the heavier aldehyde may increase. Processing time of 0.5 to 10 hours is usually sufficient.

In this step, the aldehyde is converted into an aldole, but a part of the aldol further reacts with the aldehyde to become a heavy substance. Then, the heavy matter is removed by a subsequent step characteristic of the present invention.

The neutralization step of the present invention is a step of neutralizing the mixture obtained in the alkali treatment step. Examples of the acid used for neutralization include organic acids such as formic acid, acetic acid, propionic acid and oxalic acid, and inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid. When an inorganic acid is used as the acid, an inorganic salt generated by the neutralization may precipitate. In this case, it is necessary to remove the inorganic salt by filtration after the neutralization. From this viewpoint, it is preferable to use an organic acid that does not require a filtration operation.

The pH after neutralization is preferably adjusted to the pH of the salt to be formed, that is, it is preferable to completely neutralize the alkali used in the previous step.
% Or more is not particularly problematic, and the pH is usually in the range of 5 to 12. If the neutralization step is omitted without using the present invention, heavy substances will be generated in the subsequent distillation step.

[0011] The distillation step of the present invention means that the neutralized solution obtained in the neutralization step is formed from a group consisting of alcohols, aldehydes, ketones and esters having a boiling point higher than the alcohol to be separated and recovered. This is a step of distilling the alcohol to be separated and recovered in the presence of at least one selected solvent (hereinafter, referred to as "high boiling point solvent"). The boiling point difference between the high boiling point solvent and the alcohol to be separated and recovered depends on the equipment used for distillation, but is preferably 20 ° C. or higher. For example, when the alcohol to be separated and recovered is methanol, the high boiling solvent is preferably butanol, amyl alcohol, or the like. In particular, one of the most suitable embodiments is to use n-butanol as a high boiling point solvent for a methanol solution containing acetaldehyde. The distillation method may be any of normal pressure and reduced pressure, and may be any of a batch type and a continuous type.

As a method for causing a high boiling point solvent to coexist,
A high boiling point solvent may be added before the alkali treatment step, before the neutralization step, or before the distillation step. If the alcohol solution containing aldehydes as the starting material already contains a high-boiling solvent, it is not necessary to add a high-boiling solvent thereafter. The high-boiling solvent may be reused repeatedly. The amount of the high boiling point solvent to be coexisted is usually 0.1 to 10.0 parts by weight, preferably 0.1 part by weight, per 100 parts by weight of the solution to which the high boiling point solvent is added.
It is 5 to 5.0 parts by weight. When the addition amount is too small, the effect of suppressing the accumulation of heavy substances in the distillation apparatus is insufficient, while when the addition amount is excessive, the cost of the high boiling point solvent and the heat amount required for distillation are reduced. It is uneconomical.

The alcohol to be separated and recovered is recovered as a distillate from or near the top of the distillation column, and the alcohol is of high purity containing substantially no aldehyde. On the other hand, aldols and heavy substances generated in the alkali treatment step are dissolved in a high boiling point solvent and removed as a bottom liquid. Incidentally, without distillation according to the present invention, when the distillation is performed in the absence of a high boiling point solvent,
Heavy matter generated in the alkali treatment step accumulates at various points in the distillation apparatus, and the distillation apparatus is blocked, so that stable continuous operation cannot be performed for a long period of time.

The aldehyde-containing alcohol to be subjected to the purification method of the present invention is not particularly limited, and a wide range can be used. For example, in the presence of hydrogen and a hydrogenation catalyst, the alcohol may be used. Is used as a solvent to react aminophenols and aldehydes to form alkylaminophenols. Then, the reaction solution after the reaction is subjected to distillation to obtain a fraction containing alcohol as a main component. The effluent is used optimally.

[0015]

Next, the present invention will be described by way of examples. Example 1 In a 3 L flask equipped with a stirrer, a reflux condenser and a thermometer,
Crude methanol 1 containing 1.0% by weight of acetaldehyde
500 g and a 30% by weight aqueous sodium hydroxide solution
0 g (6.0 g of sodium hydroxide, alcohol solution containing aldehydes / alkali weight ratio = 100/0.
4) was charged and heated and stirred at 60 ° C. for 4 hours. After cooling,
Analysis by gas chromatography revealed that 0.10% by weight of acetaldehyde remained. The obtained alkali-treated solution was neutralized to pH = 8.9 with a 65% by weight aqueous solution of acetic acid, and 22.8 g of 1.5 parts by weight of n-butanol was added to 100 parts by weight of the neutralized solution. Was added as a high boiling point solvent, and batch distillation was carried out at normal pressure using an Oldershaw distillation column having 10 theoretical plates. As a distillate from the top of the distillation column, 1302 g of methanol containing 0.12% by weight of acetaldehyde and containing no n-butanol was obtained. The methanol recovery at this time was 91.0% (however, methanol recovery = (weight of methanol in distillate))
/ (Weight of methanol in distillation raw material) × 100. )
Met. Further, in the bottom liquid of the distillation column, n-butanol and water were separated, but no insoluble content was observed.

Comparative Example 1 To the crude methanol used in Example 1, 22.9 g of n-butanol was added without performing alkali treatment, and the crude methanol was added using an Older-Short distillation column having 10 theoretical plates. The mixture was subjected to batch distillation. Distillation was performed so that the methanol recovery was 90.0%. As a result, 1.1% by weight of acetaldehyde was present in the distillate, and the aldehyde was not separated from the alcohol at all.

Comparative Example 2 The amount of a 30% by weight aqueous sodium hydroxide solution was adjusted to 5.0 g (weight ratio of sodium hydroxide 1.5 g, alcohol solution containing aldehydes / alkali = 100 / 0.1). Other than that, it carried out similarly to Example 1. The concentration of acetaldehyde after the alkali treatment was 0.40% by weight. Thereafter, neutralization and n-butanol addition were carried out, and batch distillation was carried out using an Oldershort distillation column having 10 theoretical plates. The acetaldehyde concentration in the distilled alcohol was 0.42% by weight. And it was high.

Comparative Example 3 The same operation as in Example 1 was performed except that the neutralization treatment was not performed. The acetaldehyde concentration in the distilled alcohol was 0.1
Although it was as low as 1% by weight, precipitation of a heavy substance-like solid which was not dissolved in the can solution was observed in the still.

Comparative Example 4 A treatment was carried out in the same manner as in Example 1 except that n-butanol, a high boiling point solvent, was not added. Although the concentration of acetaldehyde in the distilled alcohol was as low as 0.12% by weight, precipitation of a solid which was not dissolved in the bottom liquid in the still was observed.

Example 2 Example 1 was repeated except that the amount of a 30% by weight aqueous sodium hydroxide solution was changed to 250 g (sodium hydroxide 75 g, alcohol solution containing aldehydes / alkali weight ratio = 100 / 5.0). Was performed in the same manner as described above. Although the concentration of acetaldehyde after the alkali treatment was as low as 0.04% by weight, solids which did not dissolve in the treatment liquid were observed around 3 hours after the treatment. Thereafter, the precipitated solid was neutralized without filtration, n-butanol as a high-boiling solvent was added, and batch distillation was performed using an Older-Short distillation column having 10 theoretical plates. However, the concentration of acetaldehyde in the distilled alcohol was as low as 0.05% by weight, and no precipitation of insoluble components was found in the still.

Example 3 n was placed in a 3 L flask equipped with a stirrer, a reflux condenser and a thermometer.
1500 g of crude methanol containing 0.5% by weight of butyraldehyde and 10% by weight of a 30% by weight aqueous sodium hydroxide solution.
0 g (30.0 g of sodium hydroxide, alcohol solution containing aldehydes / alkali weight ratio = 100/2.
0) was added and the mixture was heated and stirred at 60 ° C. for 4 hours. After cooling, analysis by gas chromatography revealed that 0.08% by weight of n-butyraldehyde remained. The obtained alkali-treated solution was neutralized to pH = 8.9 with a 65% by weight aqueous acetic acid solution, and n-butanol as a high boiling point solvent was 1.0 part by weight with respect to 100 parts by weight of the neutralized solution. 0 g,
Batch distillation was carried out under normal pressure using an Oldershort distillation column having 10 theoretical plates. As a distillate from the top of the distillation column, 1354 g of methanol containing 0.11% by weight of n-butyraldehyde and containing no n-butanol was obtained. The methanol recovery at this time was 95.0%. Further, in the bottom liquid of the distillation column, n-butanol and water were separated, but no insolubles were observed.

Example 4 n was placed in a 5 L flask equipped with a stirrer, a reflux condenser and a thermometer.
-470 ml of crude methanol containing 0.4% by weight of butyraldehyde and 2.0% by weight of n-butanol
At a rate of 30% by weight aqueous sodium hydroxide solution 28
g / Hr (8.4 g / Hr sodium hydroxide, alcohol solution containing aldehydes / alkali weight ratio = 10)
0 / 2.3), and the mixture was stirred at 60 ° C. At this time, the liquid volume in the flask was set to 4.5 L, and the residence time was set to 9 hours. After the treatment liquid was cooled, it was analyzed by gas chromatography. As a result, 0.11% by weight of n-butyraldehyde remained. The obtained alkali-treated solution was treated with 65% by weight acetic acid aqueous solution to pH =
The mixture was neutralized to 8.9, and continuous distillation was performed for 30 hours under normal pressure at a reflux ratio of 0.5 by using an Oldershaw distillation column having 30 theoretical plates. When the distillate was analyzed from the top of the distillation column, n-butyraldehyde was 0.11 to 0.1 on average.
14% by weight and n-butanol were not detected during the whole period. The average recovery of methanol at this time was 9
1.5%. Further, n-butanol and water were separated in the distillation still throughout the period, but no insolubles were observed.

The following can be understood from the above results. In all the examples according to the invention, the separation of the aldehyde from the alcohol is sufficient and there is no accumulation of insolubles (heavy matter) on the distillation apparatus. On the other hand, in Comparative Example 1 in which the alkali treatment step of the present invention was omitted, no aldehyde was separated from alcohol at all. In Comparative Example 2 where the amount of alkali added was too small, the separation of aldehyde from alcohol was insufficient. In Comparative Example 3 in which the neutralization step of the present invention was omitted, insolubles were precipitated in the liquid in the still. In Comparative Example 4 in which the high boiling point solvent was not added, an insoluble component was precipitated in the kettle liquid in the distillation kettle.

[0024]

As described above, according to the present invention, high-purity alcohol can be efficiently separated and recovered from an alcohol solution containing aldehyde, and no insoluble matter is accumulated in the distillation apparatus. An excellent alcohol purification method capable of continuous stable operation for a long period of time could be provided.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C07C 29/80-29/84 C07C 29/88 WPI / L (QUESTEL)

Claims (1)

(57) [Claims] An alcohol purification method for separating and recovering an alcohol from an alcohol solution containing an aldehyde, the method comprising the following steps: Alkali treatment step: A step of converting aldehyde to aldol by adding and mixing 0.2 to 5.0 parts by weight of alkali per 100 parts by weight of alcohol solution containing aldehyde. Neutralization step: Alkaline Step of neutralizing the mixture obtained in the treatment step Distillation step: The neutralized liquid obtained in the neutralization step is converted to an alcohol, aldehyde, or the like having a boiling point higher than that of the alcohol to be separated and recovered.
A step of distilling the alcohol to be separated and recovered in the presence of at least one solvent selected from the group consisting of ketones and esters