JPH02188540A - Methanol purification method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is particularly directed to efficiently extracting methanol from a methanol solution (hereinafter referred to as a crude methanol solution) containing methanol as the main component and containing aldehydes and other impurities, which is generated in an organic synthesis reaction. Concerning methods of recovery and purification.

<Prior Art> As a methanol purification method for recovering highly pure methanol from a crude methanol solution, a rectification method is generally considered.

However, methanol solutions containing aldehydes and other impurities, that is, aldehyde-methanol solutions, have a special vapor-liquid equilibrium relationship that is difficult to imagine from the boiling point difference and vapor-liquid equilibrium data in data books such as Dechema. It has been found that in general rectification operations, it is not possible to separate easily even with total reflux operation or reduced pressure operation, and on the contrary, it becomes worse.

Therefore, it has been difficult to efficiently separate the two using conventional general rectification methods.

<Problems to be Solved by the Invention> The present inventors have conducted extensive studies on a method for separating methanol from aldehydes and other impurities from a crude methanol solution, and in particular for recovering and purifying high-purity methanol from which aldehyde has been substantially removed. As a result, they discovered that the objective could be better achieved by performing specific treatment and rectification, and completed the present invention.

Means for Solving the Problems> The present invention provides a method for recovering methanol by rectification from a crude methanol solution containing methanol as a main component and containing aldehyde and other impurities. This is a methanol purification method characterized by rectifying the crude methanol solution in the presence of % by weight of water or adjusting the pH of the crude methanol solution to 7 to 12.

The method of the present invention will be explained in detail below.

The crude methanol solution applied to the present invention contains methanol as a main component and contains aldehyde and other impurities. Here, examples of the aldehyde include formaldehyde, acetaldehyde, propionaldehyde, or isobutyraldehyde, and the concentration of aldehyde in the crude methanol solution is 0.1 to 50% by weight, preferably 0.1 to 20% by weight. . Other impurities other than aldehyde include ethanol, propyl alcohol, isobutyl alcohol, and water.

One implementation of the method of the invention! ! The method is to add water to the crude methanol solution, adjust the water content to 10 to 60% by weight, and then rectify it. Here, the method of adding water is not particularly limited, but it is possible to add a predetermined amount of water to the crude methanol solution and supply it to the rectification column for rectification, or to add water to the distillation column separately from the feed liquid. The same effect can be obtained by supplying water from a stage above the supply stage and subjecting it to rectification, or by supplying water from the upper stage of a batch type rectification tower. The obtained methanol contains impurities such as water other than aldehyde,
By further rectifying if necessary, a methanol solution with even higher purity can be easily obtained.

As a particularly desirable embodiment for efficiently carrying out the method of the present invention on an industrial scale, it is preferable that the water addition and rectification operations be carried out continuously, and by adopting such a mode, the complexity of the operation can be reduced. This makes it possible to stabilize operations and save labor.

Moreover, when adding water, an alkali can be used in combination, for example, it can be added as an aqueous alkaline solution. Examples of the alkali used here include caustic soda, caustic potash, and alkali carbonate, and caustic soda is preferably used.

Another embodiment of the invention is to reduce the pH of the crude methanol solution to 7.
-12 and then rectification. Here, p
As the alkali used for adjusting H, the alkali mentioned above is used.

Alkali flakes can be used as the alkali for pH adjustment, but when the crude methanol solution does not contain water, it is desirable to add it in the form of an aqueous solution.

<Effects of the Invention> According to the method of the present invention, methanol with extremely low aldehyde content can be efficiently obtained.

<Examples> The method of the present invention will be explained in more detail below using Examples and Reference Examples, but the present invention is not limited to these Examples.

The distillation column used in Examples 1 and 2 was a packed column with a diameter of 800 mm, a concentration section of 6 stages, and a recovery section of 17 stages.

Further, in Reference Example 1 and Example 3, a distillation apparatus having approximately three stages was used.

Example 1 Water was added to a crude methanol solution to form the following composition: acetaldehyde concentration: 0.2% by weight, water: 4
Prepare a solution consisting of 0% by weight and the remainder methanol, and apply this solution to 1200kg/la.
was fed to the rectification column at a rate of r. The feed temperature was 28°C. Continuous distillation was performed at a reflux ratio of 20 under normal pressure, and the tower top temperature was 64°C and the tower bottom temperature was 75°C.

As a result, the acetaldehyde concentration was 80 ppm.

Bottle liquid with 45% water content and methanol remaining at 110% by weight
Obtained at a rate of 0 kg/hr. Further, a distillate having an acetaldehyde concentration of 2.8% by weight, water of 0.01% by weight, and the remainder being methanol was obtained at a rate of 100 kg/hr.

For comparison, a crude methanol solution with an acetaldehyde concentration of 0.4% by weight, water of 7.7% by weight, and the remainder being methanol was supplied to the rectification column at a rate of 1060 kg/hr without adding water. Except for this, the procedure was carried out in exactly the same manner as in Example 1.The acetaldehyde concentration was 0.4% by weight, and the water content was 9.9% by weight.
900 kg of can liquid with 2% by weight and the rest being methanol
/hr.

In addition, the acetaldehyde concentration was 0.34% by weight, and the water content was 0.34% by weight.
160% by weight of distillate with the remainder being methanol
kg/hr.

Example 2 Add 1 kg of 5% by weight caustic soda aqueous solution to crude methanol solution
/hr and the following composition acetaldehyde concentration:
1.5% by weight Water 3.4% by weight
A solution having a pH of 9 to 10 was prepared, the remainder being methanol, and this solution was fed to the rectification column at a rate of 1080 kg/hr. The feed temperature was 32°C. Continuous distillation was performed at a reflux ratio of 10 under normal pressure, and the tower top temperature was 64°C and the tower bottom temperature was 68°C. As a result, the acetaldehyde concentration was 40
ppm, a water content of 4.1% by weight, and the remainder being methanol, a bottom liquid was obtained at a rate of 910 kg/hr. Further, a distillate having an acetaldehyde degree of 9.3 wt%, a water content Q of 1 wt%, and the remainder methanol was obtained at a rate of 170 kg/hr.

Reference Example 1 A crude methanol solution containing 8.9% by weight of acetaldehyde, 0.13% by weight of isobutyraldehyde, and 0.2% by weight of water, the remainder being methanol, was subjected to total reflux distillation under normal pressure. The tower top temperature was 27°C and the tower bottom temperature was 65°C. As a result, the acetaldehyde concentration was 6.5% by weight, the isobutyraldehyde was 0.10% by weight, and the water was 0.5% by weight.
A bottom liquid composition was obtained in which the remainder was methanol. Also, the acetaldehyde concentration was 79% by weight, and the isobutyraldehyde concentration was 0.
A distillate composition was obtained in which 15% by weight of water and 0.1% by weight of water and the remainder was methanol.

Example 3 An equal amount of water was added to the crude methanol solution of Reference Example 1, and total reflux distillation was performed under normal pressure. The tower top temperature was 27°C and the tower bottom temperature was 65°C. As a result, the acetaldehyde concentration was 1.7% by weight, the isobutyraldehyde concentration was 0.03% by weight,
A bottom liquid composition was obtained in which water was 47% by weight and the remainder was methanol. In addition, a distillate composition was obtained in which the acetaldehyde concentration was 78% by weight, the inbutyraldehyde was 0.30% by weight, and the water was 0.2% by weight, the balance being methanol.

(Left below) Hand $J? I official document (spontaneous) 1. Indication of the case Patent Application No. 7390 of 1999 2. Name of the invention Methanol fil manufacturing method 3. Person making the amendment Relationship to the case Patent applicant (209) Representative of Sumitomo Chemical Industries, Ltd. Person Hideo Mori 4, Agent 5-33 Kitahama 4-chome, Chuo-ku, Osaka City The scope of claims is amended as shown in the attached sheet.

(2) On page 3, line 13 of the specification, the phrase "10 to 60% by weight of the crude methanol solution" has been replaced with "so that the water content of the crude methanol solution is 10 to 60% by weight." to correct.

Attached Patent Claims (1) A method for recovering methanol by rectification from a crude methanol solution containing methanol as a main component and containing aldehydes and other impurities, wherein the crude methanol solution has a water content of 10 to 60% by weight. A method for purifying methanol, which comprises rectifying the crude methanol solution in the presence of water or adjusting the pH of the crude methanol solution to 7 to 12.

(2) The aldehyde concentration in the crude methanol solution is 0.
．． The method according to claim 1, wherein the amount is 1% to 50% by weight.

(3) The method according to any one of claims (1) and (2), wherein when water is present, the rectification is carried out continuously while continuously adding water.

(4) The method according to claim (3), wherein water is added to the upper stage of the rectification column and the rectification is carried out while mixing inside the column.

(Margin below)

Claims (4)

[Claims] (1) In a method of recovering methanol by rectification from a crude methanol solution containing methanol as a main component and containing aldehydes and other impurities, 10 to 60% by weight of water is allowed to coexist with respect to the crude methanol solution, or A method for purifying methanol, which comprises adjusting the pH of a crude methanol solution to 7 to 12 and then rectifying it. (2) The aldehyde concentration in the crude methanol solution is 0.1
% to 50% by weight. (3) The method according to any one of claims (1) and (2), wherein when water is present, the rectification is carried out continuously while continuously adding water. (4) The method according to claim (3), wherein water is added to the upper stage of the rectification column and the rectification is carried out while mixing inside the column.