JPH06122638A - Method for purifying alcohol - Google Patents

Abstract

PURPOSE:To provide a novel method for distillation-purifying an alcohol produced by the hydrogenation of an aldehyde, capable of producing the alcohol having a purity, especially giving a sulfuric acid coloring test result, and enabling to sufficiently satisfy demands on industry. CONSTITUTION:The method for distilling-purifying an alcohol produced by the hydrogenation of an aldehyde comprises distilling away low boiling components and the alcohol from high boiling points in the first distillation tower, distilling away the low boiling components from the alcohol in the second distillation tower, and allowing the alcohol component to flow out as a side flow. The obtained alcohol component has a good purity and a good carbonyl value and gives a good sulfuric acid coloration test, and the purification method gives an industrially large profit, because the distillation can sufficiently be performed with the two tower distillation system, thereby greatly curtailing the installation and energy costs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for distilling and purifying alcohol obtained by hydrogenation reaction of aldehyde.

[0002]

2. Description of the Related Art Conventionally, for hydrogenation of higher aldehydes,
Usually, nickel-based catalysts or copper-based catalysts are used.However, when any of the catalysts is used, various side reactions occur to generate a large amount of side reaction products, which lowers the selectivity of the reaction. ing. For this reason, the yield of alcohol is lowered, and it is very laborious to purify alcohol and treat by-products.

When hydrogenating higher aldehydes using a nickel-based catalyst, problems as side reactions are the production of various hydrocarbons by the hydrogenolysis of aldehyde groups, and the production of acetals and ethers. The production of hydrocarbons other than acetals and ethers can be suppressed to some extent by lowering the reaction temperature, but the production of acetals and ethers can hardly be suppressed, and the yield of higher alcohols is greatly affected.

It is considered that these acetals and ethers are produced by the reactions of the following formulas (1) and (2).

[0005]

[Chemical 1]

(However, R is an alkyl group having 3 or more carbon atoms.) That is, one molecule of unreacted aldehyde in formula (1) reacts with two molecules of alcohol produced by hydrogenation to produce an acetal, In the formula (2), this acetal is hydrolyzed to produce ether and alcohol. Crude alcohol containing these by-products is distilled and purified to obtain an alcohol product. Since the alcohol is mainly used as a plasticizer for resins such as polyvinyl chloride, an extremely high purity is obtained for the alcohol. It is required that the degree of coloring is small, especially in the sulfuric acid coloring test. The sulfuric acid coloring test is carried out by heat treating the sample with sulfuric acid and subsequently measuring the degree of coloring.

As a method for distilling and purifying the above crude alcohol,
The following methods have been proposed. First, after separating low-boiling substances in the first column, the pressure at the top is then operated in the second column to distill and separate alcohol from high-boiling substances to distill and obtain alcohol products from the top of the column. There is a method (3 tower system) of operating the pressure at the top of the 3 towers to recover useful products in the high boiling point components.

According to Japanese Examined Patent Publication No. 49-11365, in the above-mentioned three-column system, the second column has a top pressure of 200 to 800 mmH.
g, operating under the condition that the alcohol content in the bottom of the tower is 50 wt% or more, and the top pressure of the third tower is 70 to 300 mm.
Purified 2-ethylhexanol is obtained by operating under Hg conditions. In addition, in the above three tower system, the first
A method of performing the tower in two stages (four tower system; see FIG. 2) is also known.

[0009]

However, in the above-mentioned method, even if the second column is precisely distilled and purified, the high-boiling components in the bottom liquid, especially the acetal component and the ether component, are slightly decomposed by heat. Inevitably, the low boiling point product generated is contained in the alcohol product distilled from the top of the column, which not only lowers the purity of the product, but also especially in the sulfuric acid coloring test and the carbonyl number, It's hard to say that we can be satisfied with the requirements. The present invention provides a novel method for purifying alcohol which can solve the problems of the conventional methods as described above.

[0010]

That is, the gist of the present invention is to supply an alcohol product to a first distillation column by distilling and purifying an alcohol product obtained by hydrogenating an aldehyde. The high-boiling component is separated by distillation, and the fraction containing the low-boiling component and the alcohol, which does not substantially contain the high-boiling component, is distilled off from the top of the column, and this is fed to the second distillation column to feed the low-boiling component to the alcohol. From the top of the column to distill off the fraction containing the low boiling point component as the main component, while the alcohol component is discharged as a side stream from below the raw material supply stage to obtain a purified alcohol. It depends on the purification method.

The present invention will be described in more detail below. As the aldehyde that is a raw material of the alcohol used in the present invention, a saturated or unsaturated aldehyde having at least 4 carbon atoms and usually having 4 to 17 carbon atoms and a mixture thereof are used. Saturated aldehydes include linear and side chain aldehydes, specifically butyraldehyde, heptyl aldehyde, nonyl aldehyde, undecyl aldehyde, tridecyl decyl aldehyde, hexadecyl aldehyde, heptadecyl aldehyde, and the like. Examples of unsaturated aldehydes include 2-ethylhexenal, 2-propylheptenal, and decenal.

As the hydrogenation catalyst, any conventionally known one can be used. For example, a carrier such as diatomaceous earth or celite carrying an active component such as nickel, chromium or copper is used. Usually, the one supporting nickel and chromium is used. In the hydrogenation reaction of the aldehyde, the corresponding alcohol is produced by using the hydrogenation catalyst and usually under reaction conditions of normal pressure to 150 atm and 40 to 200 ° C. It is desirable that the conversion rate of the aldehyde is usually in the range of 80 to 99.99%.

As a result of the hydrogenation reaction, the raw material is butyl alcohol.
C in case of dehydrat₈Ether, C ₁₂Such as acetals
When the by-product is also 2-ethylhexanal,
C₁₆Ether, C_{twenty four}By-products such as acetals are more
C in the case of 2-propylheptenal₂₀ether,
C₃₀By-products such as acetals are produced as by-products.

The distillation apparatus and distillation conditions of the present invention will be described below with reference to the flow chart shown in FIG. The first column (10) of the present invention is a distillation column for separating high boiling substances in a crude alcohol product, and the concentration of high boiling by-products in the bottom liquid of the distillation column is preferably 50 wt% or more. Is 70 wt%
As described above, it is important to distill the low boiling point component and the alcohol component while more preferably maintaining the range of 70 to 90 wt%. Usually, the number of stages is 10 to 40, and the reflux ratio is 1 to 1.
0, pressure several mm mercury column-normal pressure, tower bottom temperature 80-180 ° C
It is performed under the conditions within the range.

The crude alcohol (2) distilled from the top of the first tower is then supplied to the second tower (11).
The second column is a distillation column for separating low-boiling substances such as aldehydes and the target alcohol and refining the alcohol, distilling low-boiling components from the top of the column and lower stage below the raw material supply stage. Purified alcohol is discharged from the nearby sidestream (5) to obtain an alcohol product. The second column is usually operated under the conditions of 30 to 60 plates, a reflux ratio of 3 to 50, and a pressure of several mm of mercury column to normal pressure.

The bottom liquid (6) flowing out from the bottom of the second tower (11) is circulated to the feed liquid (1) supplied to the first tower (10), and the second tower (11) is circulated. It prevents the accumulation of high-boiling substances. This high-boiling substance is mainly a high-boiling substance produced by the reaction between the low-boiling substance and the alcohol in the second column (11). Also, this canned liquid (6)
May be circulated to the hydrogenation reactor which is a pre-stage of distillation.

In the method of the present invention, since the high-boiling substance is first separated in the first column, even if a part of the high-boiling substance undergoes a thermal decomposition reaction to form a low-boiling substance such as aldehyde, In the column, the produced low-boiling substance can be separated by distillation from alcohol, so that the obtained alcohol product has a good product purity and a sulfuric acid coloring test, and further, a good carbonyl value. In addition, the present invention has a merit that the facility cost and the energy cost can be significantly reduced because the distillation column requires only the two-column system as compared with the conventional three-column system or four-column system, and can be said to be an industrially advantageous method.

The sulfuric acid coloring test method includes Monsanto method, Eastman method, Sekisui method, etc., but all of them differ only in fine conditions and the main operations are the same, and Monsanto method is widely used. . The Monsanto method was also adopted in the examples described later, and the measuring method is shown below. Sample 1 into a washed and dried 300 ml flat bottom flask with stopper
Add 00 ml. While stirring the sample, 8 ml of 98 wt% concentrated sulfuric acid is added with a 25 ml buret at a rate of 2 ml / min at room temperature of 30 ° C. or lower. Stop the flask and plug 9
Immerse in a water bath at 8 ± 2 ° C for 2 hours. Then, after cooling to room temperature with water, the sample is set to have an inner diameter of 25 mm and a height of 270 m.
100 ml is transferred to a flat-bottomed glass colorimetric tube of m and visually compared with the same amount of APHA color standard solution using the same colorimetric tube, and the APHA value of the same color is used as a measured value. The composition of the APHA color stock solution is as follows.

[0019]

[Table 1] Potassium chloroplatinate (K ₂ PtCl ₆ ) 1.245 g Cobalt chloride (CoCl ₂ .6H ₂ O) 1.000 g 98% concentrated sulfuric acid 100 ml

Put the above into a 1000 ml volumetric flask and add distilled water to dissolve it.
Set to ml. This solution is APHA500, and is proportionally diluted with distilled water to obtain a low APHA color standard solution. A
The smaller the PHA value, the more preferable, but the APHA value is usually 2
When it is about 0 or less, it is industrially preferable as a plasticizer alcohol. However, the standard of this sulfuric acid coloring test value differs depending on the type of alcohol.

The carbonyl value was determined by measuring the consumption amount of potassium hydroxide (mgKOH / 1 g of sample) in accordance with the aldehyde content measuring method described in JIS K1525. The smaller this value is, the more preferable it is. However, if the carbonyl value is 0.08 (mgKOH / g of sample) or less, it is industrially preferable as a plasticizer alcohol. For purity, gas chromatography analysis (column:
It was decided by performing salmon 3000).

[0022]

EXAMPLE A pentspent BB fraction having the following composition after continuously removing butadiene and isobutene from a BB fraction obtained by cracking naphtha was continuously hydroformylated.

[0023]

[Table 2] [Composition] 1-butene 43 wt% 2-butene 22 isobutene 4 butadiene 1.3 C _{3 group} 0.3 other 29.4 The reaction conditions are as follows: total pressure 7 kg / cm ² G, oxo gas partial pressure 4 kg / cm.
² G (H ₂ / CO = 1), reaction temperature 100 ° C

[Table 3] Raw material / catalyst liquid = 10 (weight ratio) Reactor residence time was 2.0 hours.

After depressurizing the reaction solution, almost all the produced valeraldehyde was recovered by distillation.

## EQU1 ## 2-methylbutyraldehyde / n-valeraldehyde = 0.1 3-methylbutyraldehyde / n-valeraldehyde =
0.02: pivalaldehyde / n-valeraldehyde = 0.01.

Next, this aldehyde was used as it was at a reaction temperature of 9
A condensation reaction was performed for 1.5 hours in an autoclave of 10 liters at 5 ° C., atmospheric pressure, and aldehyde / 3% aqueous sodium hydroxide solution = 1 (weight ratio).

The conversion rate of each aldehyde is

Table 4 n-valeraldehyde 99.9% 2-methylbutyraldehyde 99.8 3-methylbutyraldehyde 99.8 pivalaldehyde 98.2.

Next, the decenal mixture was hydrogenated with a nickel-based solid catalyst. Hydrogenation conditions are pressure 100k
g / cm ² G, temperature 100 ° C., catalyst / decenal = 0.
The reaction was carried out by a batch reaction at 1 (weight ratio) for 3.0 hours. The conversion rate of decenal was 99.9%. The high boiling point component in the produced alcohol was 0.5 wt% and the low boiling point component was 4.5 wt%.

The crude alcohol obtained by the above hydrogenation was continuously distilled using the flow shown in FIG. The distillation column (1
0) was used as an Oldershaw distillation column having an inner diameter of 100 mm × 30 stages, and as the distillation column (11) was an Oldershaw distillation column having an inner diameter of 35 mm × 70 stages. The distillation conditions of each distillation column are as shown in Table 1. Sidestream (5) of distillation column (11)
Table 2 shows the results of the sulfuric acid coloring test, the carbonyl value and the C ₁₀ alcohol purity of the purified alcohol thus obtained.

Comparative Example 1 and Comparative Example 2 Continuous distillation of the crude alcohol obtained by the same method as in Example was carried out using the flow shown in FIG. As the distillation column (12), an Oldershaw distillation column having an inner diameter of 100 mm × 30 stages, and as the distillation column (13), an inner diameter of 50 mm × 40
An Oldershaw distillation column having a tray, an Oldershaw distillation column having an inner diameter of 35 mm × 20 trays was used as the distillation column (14), and an Oldershow distillation column having an inner diameter of 35 mm × 30 trays was used as a distillation column (15). The distillation conditions of each distillation column are as shown in Table 1.

Table 2 shows the results of sulfuric acid coloring test, carbonyl number and C ₁₀ alcohol purity of the rectified alcohol obtained from the distillate (4) of the distillation column (13).

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

EFFECTS OF THE INVENTION According to the method of the present invention, the obtained alcohol product has a good product purity and a sulfuric acid coloration test, and a good carbonyl value. Further, since the distillation column can be a two-column system, the facility cost and It can greatly reduce the energy cost, thus providing a great industrial advantage.

[Brief description of drawings]

FIG. 1 is a diagram showing a two-column distillation apparatus according to the present invention.

FIG. 2 is a diagram showing a distillation apparatus by a four-column system shown in a comparative example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C07C 31/12 8930-4H 31/125 8930-4H

Claims (1)

[Claims] 1. When distilling and refining an alcohol product obtained by hydrogenating an aldehyde, the alcohol product is fed to a first distillation column to separate alcohol from a high boiling point component by distillation to lower the temperature from the top of the column. A distillate containing a boiling point component and an alcohol and substantially not a high boiling point component is distilled off, and this is fed to a second distillation column to separate the low boiling point component from the alcohol by distillation, and the low boiling point component is removed from the top of the column. A method for purifying alcohol, which comprises distilling a fraction containing a main component, and flowing out an alcohol component as a side stream from below a raw material supply stage to obtain a purified alcohol.