JPH04202151A - Purification of 1,6-hexanediol - Google Patents

Abstract

PURPOSE:To obtain the title high-purity compound by saponifying a crude product from cyclohexane after oxidation, esterification, hydrogenation and distillation process, then neutralizing and removing low-boiling substances and high- boiling substances using a stripping column and a distillation column, and further purifying by distillation. CONSTITUTION:In producing the objective compound by oxidizing cyclohexane into a carboxylic acid compound, esterifying the carboxylic acid compound with an alcohol and hydrogenating a mixed solution of the prepared esterified substance, then low-boiling substances and high-boiling substances are removed from the hydrogenated reaction solution by distillation operations 1-2 (ghown in i.g.) give a crude reaction product having 100-100mgKOH/g ester value(EV). Then the reaction product is saponified (4) with an alkali aqueous solution and neutralized with about 0.01-0.30mol, based on the objective compound in the saponified solution, of an acid. Further, low-boiling substances and high- boiling substances are removed from the neutralized solution by a stripping column 6 and a distillation column 7 and purified by distillation to give the objective high-purity compound having <=5mgKOH/g EV in high yield.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention is directed to the ``mixture of esterified products J'' obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane.
was hydrogenated to produce 1,6-hexanediol, and the hydrogenated reaction solution was distilled to obtain an ester value (EV) of 1,6-hexanediol.
Crude 1,6-hexanediol with a high value) is saponified with an alkaline aqueous solution, and the saponified liquid is neutralized with a mineral acid such as concentrated sulfuric acid. The present invention relates to a method for industrially producing 1,6-hexanediol with a low 1rEV value and high purity in a high yield by removing low-boiling substances and high-boiling substances and finally performing distillation purification.

[Description of prior art]

Conventionally, as a method for producing 1,6-hexanediol, for example, as described in Japanese Patent Publication No. 53-33567, cyclohexane is oxidized to produce carboxylic acid compounds such as adipic acid and oxycaproic acid. generate,
The carboxylic acid compound, ethanol, butanol, ■
, esterified with an alcohol such as 6-hexanediol, separated and purified to produce an esterified product, and finally, the obtained esterified product was hydrogenated with hydrogen in the presence of a hydrogenation catalyst. A known method is to produce 1,6-hexanediol, and then purify the hydrogenated product by distillation to obtain 1,6-hexanediol.

In the above-mentioned known method for producing 1,6-hexanediol, the hydrogenation reaction solution of the esterified product contains a small amount of the esterified product, which is extremely difficult to separate by distillation by ordinary distillation purification, and the ester value ( There was a problem in that only 1.6-hexanediol with a fairly high EV value could be obtained.

[Problems to be solved by the present invention]

The object of the present invention is to use the above-mentioned method for producing 1,6-hexanediol, in which an esterified product which is difficult to separate by a distillation operation from a hydrogenated reaction product of a mixture of esterified products (for example, crude 1,6-hexanediol) is used. can be easily removed,
As a result, it is an object of the present invention to provide a purification method capable of industrially producing highly pure 1,6-hexanediol with a low EV value.

[Means to solve problems]

This invention involves hydrogenating a mixture of esterified products obtained by esterifying a carboxylic acid compound by oxidizing cyclohexane with an alcohol to produce 1,6-hexanediol, and distilling the hydrogenated reaction solution. Remove low boiling point substances and high boiling point substances, and reduce the ester value (EV value) to 10 to 1'O
Omg KOH/g of crude 1,6-hexanediol was obtained, and then the crude 1,6-hexanediol was saponified with an alkaline aqueous solution in a saponification tower, and 1,6-hexanediol in the saponified liquid was
, 6-hexanediol in an amount of approximately 0.01 to 0.30 times the mole of acid is added to the saponification liquid to neutralize it, and the neutralized solution is supplied to a stripper tower to remove low-boiling substances. The ester value (
1,6- whose EV value) is 5 mgKOll/g or less
The present invention relates to a method for purifying 1,6-hexanediol, which comprises obtaining hexanediol by evaporating it from the top of the column, and finally distilling and purifying the 1,6-hexanediol in a rectification column.

[Detailed explanation of each requirement of the present invention] 'Hereinafter, the purification method of the present invention will be explained in detail with reference to the drawings. 1 is a flow diagram schematically showing an example of a purification flow for carrying out the method for purifying 1,6-hexanediol of the present invention.

The crude 1,6-hexanediol used in this invention is obtained by hydrogenating a mixture of esterified products obtained by esterifying a carboxylic acid compound obtained by oxidizing cyclohexane with an alcohol to produce 1,6-hexanediol. Then, the hydrogenation reaction solution is purified and produced.

The liquid mixture of the above-mentioned esterified products is, for example,
As described in Japanese Patent No. 3-33567, cyclohexane is heated at about 100 to 200° in the presence of a catalyst.
Various carboxylic acids (such as caproic acid, valeric acid, butyric acid, A carboxylic acid compound (mixture) containing divalent carboxylic acids such as divalent carboxylic acids such as adipic acid, glutaric acid, and succinic acid, and oxyacids such as oxyvaleric acid and oxycaproic acid is suitably added from the oxidation reaction solution. Then, these carboxylic acid compounds (mixtures) are prepared using carbon atoms such as methanol, ethanol, n-propanol, n-butanol, amyl alcohol, n-hexanol, n-heptatool, etc. ~8-valent lower alcohols, ethylene glycol, propylene glycol, 1,4
-butanediol, 1゜5-bentanediol, 1,6
- In the presence of an excess of an esterifying agent consisting of an alcohol such as a dihydric alcohol having 2 to 8 carbon atoms such as hexanediol, without a catalyst, at a high temperature of about 150 to 300°C and under normal pressure or increased pressure. or esterification in the presence of an esterification catalyst at a temperature of 50 to 150°C and under normal or elevated pressure, and finally, the product of the esterification reaction is separated by suitable means. - It may be a liquid mixture of esterified products whose main components are adipic acid ester, oxycaproic acid ester, etc. obtained by purification.

In this invention, the liquid mixture of the esterified product is
Contains about 10 to 80% by weight, especially about 50 to 70% by weight of adipate and oxycaproate, and has an acid value (AV value) of about 1.0 to 50 mgKO1l.
/g, particularly preferably 1.0 to 20 mgKOH/g, and if necessary, the esterified product may be dissolved in a suitable organic solvent (especially,
It may be a solution dissolved in an organic solvent used for extracting a carboxylic acid compound (described later).

As a method for separating carboxylic acids from the cyclohexane oxidation reaction solution described above, for example, the cyclohexane oxidation reaction solution is saponified with caustic soda, the aqueous layer is separated, and the aqueous layer containing various types of reponate salts is prepared. An alkaline solution is obtained, and the alkaline solution is neutralized with sulfuric acid or the like to a pH of 3 or less to produce mirabilite and carboxylic acids.Then, from the aqueous solution of mirabilite in the aqueous layer separated from the neutralized solution, the above-mentioned various carboxylic acids, methyl ethyl ketone,
A carboxylic acid compound (mixture) is obtained by extraction with organic solvents such as ketones such as methyl isobutyl ketone and cyclohexanone, esters such as ethyl acetate, butyl acetate, and methyl caproate, and lower alcohols such as butyl alcohol and isopropyl alcohol. be able to.

The method of hydrogenating the liquid mixture of the above-mentioned esterified products in the presence of a hydrogenation catalyst can be carried out by a known method, but in particular, in the presence of a catalyst, at 200 to 400°C, especially at 250 to
At a temperature of 350°C, 150-500 kg/c+fl
The hydrogen partial pressure is preferably 200 to 350 kg/c.

Examples of the above-mentioned hydrogenation catalyst include hydrogenation catalysts containing iron, nickel, cobalt, copper, and copper-chromite as main components, and are in the form of powder or tablets. There may be some, and the amount used is
It is sufficient to use it in an amount of about several percent by weight based on the liquid mixture of the esterified product obtained by esterifying the carboxylic acid compound.

In this invention, the hydrogenation reaction liquid obtained as described above is supplied to a first distillation column 1 and a second distillation column 2 as shown in FIG. The low-boiling substances of the hydrogenation reaction are removed from the top of the distillation column 1, the high-boiling substances of the hydrogenation reaction liquid are removed from the bottom of the second distillation column 2, and the high-boiling substances of the hydrogenation reaction liquid are removed from the top of the second distillation column 2. "Ester value (EV value) is 10~
100mgKOH/g, preferably 10-50mg
Crude 1,6-hexanediol j containing KOH/g is taken out, cooled, and collected into the crude 1,6-hexanediol tank 3 to produce crude 1,6-hexanediol.

The above-mentioned crude 1,6-hexanediol contains 1,6-hexanediol in an amount of about 60% by weight or more, particularly 70 to 90% by weight.
It is preferable that the content be contained to some extent.

In the purification method of the present invention, for example, the first
As shown in the figure, the crude 1,6-
Hexanediol is supplied from the tank 3 to the bottom of the saponification tower 4, preferably at a concentration of about 2 to 20% by weight,
In particular, a 5 to 15% by weight aqueous alkali solution such as caustic soda is supplied to the lower part of the saponification tower 4, and inside the saponification tower 4, a trace amount of the ester compound in the crude 1,6-hexanediol is preferably 50 to 200% °C temperature and 1-15kg
The saponified liquid is saponified at a pressure of /cfflG, and the saponified liquid is supplied to the neutralization tower 5. In the saponification tower 5, about 0% .01 to 0.30 times the amount of acid, preferably 0.02 to 0.25 times the amount of acid, is added to the saponification method to neutralize the saponified solution, and the neutralized solution after neutralization is The liquid is supplied to a stripper tower 6, and low-boiling substances such as water in the neutralized liquid are evaporated and removed from the top of the tower, and the bottom liquid of the stripper tower 6 is supplied to an evaporation tower 7 such as a thin film evaporator. While removing high-boiling substances such as alkali salts of organic carboxylic acids in the neutralized liquid from the bottom of the neutralized liquid, "1 having an ester value (EV value) of 5 mgKOH/g or less, preferably 1 mgKOH/g or less, 6-hexanediol" is evaporated from the top of the tower, the evaporated product is cooled and collected, and the evaporated liquid J containing mainly rl,6-hexanediol is received into the evaporated liquid tank 8. Finally, , 6-hexanediol is supplied to a rectification column 9 equipped with a multi-stage rectification plate, medium-boiling substances are removed from the top of the column, and high-boiling substances are removed from the bottom of the column. 1,6-hexanediol purified by distillation is recovered from the middle stage of the rectification column 9 while removing 1,6-hexanediol.
, 6-hexanediol product tank 10.

In the saponification step of crude 1,6-hexanediol, the amount of aqueous alkaline solution supplied to the saponification tower is
- It is preferably about 0.01 to 1 times by weight, particularly about 0.03 to 0.5 times by weight, relative to the amount of hexanediol supplied.

In addition, the saponification tower described above does not need to be specified in size and shape as long as it is a tubular tower having a hollow interior. ) A hollow basic saponification tower with alternating baffle plates or a hollow basic saponification tower with a built-in stirrer is required to determine the agitation state of the saponified liquid. is preferable because it is suitable.

The residence time of crude 1,6-hexanediol in the saponification tower is preferably about 5 to 200 minutes, particularly about 10 to 100 minutes.

In this invention, the acids used in the neutralization step of the saponified solution include mineral acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid;
Examples include acids such as organic sulfonic acids such as para-toluenesulfonic acid, and these acids are preferably supplied to the neutralization tower 5 in the form of an aqueous solution.

In the neutralization step, if the amount of acid used is more than 0.2 times the mole of 1,6-hexanediol in the saponification solution, the neutralized solution is then purified by a stripping and evaporation step. This is not appropriate because the ester value of the evaporated liquid (liquid mainly containing 1,6-hexanediol) obtained from the top of the evaporation tower 7 increases again, and if the amount of the acid used becomes too small, , 1,6-hexanediol is not suitable because the production amount thereof decreases.

〔Example〕

Hereinafter, the production method of the present invention will be explained in more detail by showing Examples and Comparative Examples.

Example 1 [Production of esterified product mixture] The alkaline solution obtained by saponifying the liquid phase oxidation reaction solution obtained by air oxidation of cyclohexane with caustic soda is neutralized with sulfuric acid, and at this time, the water in the neutralized solution is After balancing the water so that the specific gravity of the aqueous sodium sulfate solution in the layer is 1.25 and separating the neutralized solution into an aqueous layer and an oil layer, adipic acid, oxycaproic acid, etc. contained in the aqueous sodium sulfate solution in the aqueous layer are extracted. The carboxylic acid compounds were extracted with methyl isobutyl ketone (MIBK), and MIBK was removed from the extract by evaporation to obtain a mixture of carboxylic acid compounds.

Aqueous solution of the carboxylic acid mixture (concentration 63.5% by weight)
with an aqueous solution of 1,6-hexanediol under normal pressure.
The esterification reaction was carried out at a temperature of 00 to 260°C, and the content of adipate ester was 34.7% by weight, and the content of oxycaproate ester was 40.5% by weight.
% by weight of the esterified product mixture was obtained.

[Hydrogenation step] 0.6% by weight of a copper-chromite catalyst was added to the esterified mixture obtained as described above, and the hydrogen pressure was increased to 29% by weight.
A hydrogenation reaction was performed at 0 kg/aaG and a temperature of 260 to 290°C to produce L6-hexanediol, and 1,6
- A hydrogenation reaction solution containing mainly hexanediol was obtained.

The hydrogenation reaction solution obtained as described above has an EV value of 25.
．． 6 mgKOH/g, the concentration of 1,6-hexanediol was 57.7% by weight, and the content was 4.1% by weight of amyl alcohol, 0.8% by weight of water, and 32% of other low-boiling compounds. It contained 8% by weight.

[Production of crude 1,6-hexanediol] According to the production flow shown in Figure 1, first, the hydrogenated reaction solution obtained as described above was fed to the first distillation column 1 at a feeding rate of 1083 kg/hour. Hexanol is supplied to the middle stage, and from the top of the tower, hexanol,
Low-boiling substances such as amyl alcohol and water are evaporated and distilled off at a rate of 120 kg/hour, and then the bottom liquid of the first distillation column 1 is fed to the middle stage of the second distillation column 2, and high-boiling substances are evaporated at a rate of 15 kg/hour. is discharged from the bottom of the second distillation column 2, and crude 1,6-hexanediol is taken out from the top of the second distillation column 2 at a rate of 948 kg/hour and transferred to the crude 1,6-hexanediol tank 3. Uke accepted.

The crude 1,6-hexanediol has a concentration of 1,6-hexanediol of 75.0% by weight, an ester value of 12.1 mgKOH/g, and 0.7% by weight of amyl alcohol and It contained 10.2% by weight of other components.

[Saponification step, neutralization step and purification step] Next, crude 1
, 6-hexanediol From the tank 3, crude 1,6-hexanediol is supplied at a rate of 460 kg/hour to the bottom of the hollow base type saponification tower 4, which is equipped with a number of baffle plates arranged alternately. % caustic soda aqueous solution is fed to the lower part of the saponification tower 4 to saponify the crude 1,6-hexanediol at a residence time of 30 minutes in the saponification tower and a saponification temperature of 90°C, and , the saponified liquid is supplied to the neutralization tower 5, and in the neutralization tower 5, concentrated sulfuric acid is added in an amount of about 0.1 mole to 1,6-hexanediol in the saponified liquid. The saponified liquid is left at a temperature of 90°C for 30 minutes to neutralize it, and the neutralized liquid is then supplied to the middle stage of the stripper column 6 to remove the saponified liquid from the stripper column 6. Water and low-boiling substances are evaporated from the top, and the bottom liquid of the stripper tower 6 (content of 1,6-hexanediol in the bottom liquid: 82.5% by weight, EV value of the bottom liquid: 2mgKOH/g) was extracted, and the bottom liquid was further supplied to the upper part of the thin film evaporation tower 7,
While removing high-boiling substances containing alkali metal carboxylates from the bottom of the thin film evaporation tower 7, the EV value is 0.5 m.
gKOH/g of 116-hexanediol was obtained by evaporating from the top of the thin film evaporation column 7, and finally, the 1,6-hexanediol was purified by distillation in the rectification column 9 to obtain an EV value of 0. 1°6-hexanediol containing 2'mgKOH/g was continuously produced at 303kg/hour and received as a product in a 1,6-hexanediol tank 10.

The concentration of this 1,6-hexanediol was 99% by weight.

Comparative Example 1 In the same manner as in Example 1, except that the saponified liquid was not neutralized with concentrated sulfuric acid at all and the saponified liquid was directly supplied to the middle stage of the stripper column 6, - A hexanediol product was produced.

In the above-mentioned manufacturing method, the E of the evaporated liquid obtained from the evaporation tower 7 is
The V value was 0.5 mgKOH/g.

The amount of 1,6-hexanediol product obtained as described above was 287 kg/h, the concentration of 1,6-hexanediol was 99 kg/h, and 1,6-hexanediol product was
The ester value (EV value) of 6-hexanediol is 0.
It was 3 mgKOH/g.

Example 2 1,6-hexane was prepared in the same manner as in Example 1, except that the amount of concentrated sulfuric acid used was approximately 0.05 times the mole of 1,6-hexanediol in the saponification solution. Diol was produced.

In the above-mentioned manufacturing method, the E of the evaporated liquid obtained from the evaporation tower 7 is
The V value was 0.5 mg KOIl/g.

The amount of 1,6-hexanediol product obtained as described above was 301 kg/h, the concentration of 1,6-hexanediol was 99 kg/h, and 1,6-hexanediol was
The ester value (EV value) of 6-hexanediol is 0.
It was 2 mgKOH/g.

Example 3 1,6-hexanediol was produced in the same manner as in Example 1 except that para-toluenesulfonic acid was used instead of concentrated sulfuric acid.

In the above-mentioned manufacturing method, the E of the evaporated liquid obtained from the evaporation tower 7 is
The V value was 0.5 mgKOH/g.

The amount of 1,6-hexanediol product obtained as described above was 299 kg/h, the concentration of 1,6-hexanediol was 99% by weight, and
The ester value (EV value) of 6-hexanediol is 0.
It was 2 mgKOH/g.

[Actions and effects of the present invention]

According to this invention, 1,6-hexanediol is produced by hydrogenating the esterified mixture J obtained by esterifying a carboxylic acid compound by oxidizing cyclohexane, and distilling the hydrogenated reaction solution. The "crude 1,6-hexanediol with a high ester value (EV value)" obtained by Low boiling substances and high boiling substances are removed from the neutralized liquid using a stripper column and an evaporation column, and finally,
By distillation and purification, 1,6-hexanediol with a low FEV value and high purity can be produced in high yield.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram schematically showing an example of a purification flow for carrying out the method for purifying 1,6-hexanediol of the present invention. 1: First distillation column, 2: Second distillation column, 3: Crude 1.6-hexanediol tank, 4: Saponification column, 5: Neutralization column, 6:
Stripper tower, 7: Evaporation tower, 8: Evaporation, liquid tank, 9
: Rectification column, 10 : L6-hexanediol product tank. Patent applicant: Ube Industries, Ltd.

Claims (1)

[Claims] A mixture of esterified products obtained by esterifying a carboxylic acid compound obtained by oxidation of cyclohexane with an alcohol is hydrogenated to produce 1,6-hexanediol, and the hydrogenated reaction solution is distilled. By removing low boiling point substances and high boiling point substances, the ester value (EV value) is 10 to 100m.
gKOH/g of crude 1,6-hexanediol is obtained, and then the crude 1,6-hexanediol is saponified with an alkaline aqueous solution in a saponification tower, and 1,6-hexanediol in the saponified liquid is
, 6-hexanediol in an amount of approximately 0.01 to 0.30 times the mole of acid is added to the saponification liquid to neutralize it, and the neutralized solution is supplied to a stripper tower to remove low-boiling substances. The ester value (
1, characterized in that 1,6-hexanediol having an EV value of 5 mgKOH/g or less is obtained by evaporating from the top of the column, and finally, the 1,6-hexanediol is purified by distillation in a rectification column. , 6-hexanediol purification method.