JPH0699344B2 - Purification method of 1,6-hexanediol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a “mixture of esterified products” obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane.
To produce 1,6-hexanediol, and the hydrogenated reaction solution was distilled to obtain "crude 1,6-hexanediol with a high ester value (EV value)" in an alkaline aqueous solution. After saponification, the saponification solution was stripped and stripped to remove low-boiling substances and high-boiling substances, and finally purified by distillation to give a low EV value and high purity 1,6-hexane. It relates to the method of refining to "diol".

[Description of Prior Art]

Conventionally, as a method for producing 1,6-hexanediol,
For example, as described in JP-B-53-33567, cyclohexane is oxidized to produce a carboxylic acid compound such as adipic acid and oxycaproic acid, and the carboxylic acid compound is methanol, ethanol, butanol,
Esterification with alcohols such as 1,6-hexanediol, and separation and purification of the reaction product to produce an esterified product, and finally, the obtained esterified product is hydrolyzed with hydrogen in the presence of a hydrogenation catalyst. A method is known in which 1,6-hexanediol is added to produce 1,6-hexanediol, and the hydrogenation reaction product is purified by distillation to obtain 1,6-hexanediol.

In the known method for producing 1,6-hexanediol,
The hydrogenation reaction solution of the esterified product contains the esterified compound that is extremely difficult to separate by distillation by ordinary distillation purification, and only 1,6-hexanediol with a significantly high ester value (EV value) can be obtained. There was a problem.

[Problems to be Solved by the Present Invention]

The object of the present invention is to produce an esterified product which is difficult to separate by a distillation operation in a hydrogenation reaction product (eg, crude 1,6-hexanediol) of a mixed liquid of esterified products in the above-mentioned 1,6-hexanediol production method. Thus, it is an object of the invention to provide a purification method capable of industrially producing highly pure 1,6-hexanediol having a low EV value as a result.

[Means for solving problems]

This invention is to hydrogenate a mixed solution of esterified products obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane with alcohols to produce 1,6-hexanediol, and distill it from the hydrogenated reaction solution by a distillation operation. Removes low-boiling substances and high-boiling substances, and has an ester value (EV value) of 10 to 100 mgKOH / g
To obtain crude 1,6-hexanediol, and then saponify the crude 1,6-hexanediol with an alkaline aqueous solution in a saponification tower, and supply the solution after the saponification to a stripper tower. Evaporate and remove the boiling point, supply the stripper tower can to the evaporation tower and remove the high boiling point from the bottom while removing 1,6-hexanediol with an ester value (EV value) of 5 mgKOH / g or less. The present invention relates to a method for purifying 1,6-hexanediol obtained by evaporating from the top and finally purifying the 1,6-hexanediol by distillation in a rectification column.

[Detailed description of each requirement of the present invention]

Hereinafter, regarding the purification method of the present invention, with reference to the drawings,
explain in detail.

FIG. 1 is a flow chart showing an example of a purification flow for carrying out the purification method of 1,6-hexanediol of the present invention.

The crude 1,6-hexanediol used in this invention is
A mixed solution of esterified products obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane with alcohols is hydrogenated to produce 1,6-hexanediol, and the hydrogenated reaction solution is purified and produced. Of.

The liquid mixture of the above-mentioned esterified compounds is, for example, Japanese Patent Publication No.
As described in JP-A-33567, cyclohexane is oxidized with molecular oxygen or the like in the presence of a catalyst, at a temperature of about 100 to 200 ° C., and at a pressure of about ^{2 to 20} kg / cm ² G. Various carboxylic acids by-produced with cyclohexanone, cyclohexanol, etc. (monocarboxylic acids such as caproic acid, valeric acid, butyric acid, divalent carboxylic acids such as adipic acid, glutaric acid and succinic acid Carboxylic acid compounds (mixtures) containing oxyacids such as herbic acid and oxycaproic acid,
Obtained by separating from the oxidation reaction solution by a suitable means, and then obtaining the carboxylic acid compound (mixture) thereof with methanol, ethanol, n-propanol, n-butanol, amyl alcohol, n-hexanol, n-heptanol, etc. C1-C8 monohydric lower alcohols, ethylene glycol, propylene glycol, 1,4
-In the presence of an esterifying agent consisting of an alcohol such as a dihydric alcohol having 2 to 8 carbon atoms such as butanediol, 1,5-pentanediol, and 1,6-hexanediol, the catalyst is used in the absence of a catalyst to about The esterification is carried out at a high temperature of 150 to 300 ° C. and normal pressure or pressure, or in the presence of an esterification catalyst at a temperature of 50 to 150 ° C. and normal pressure or pressure, and finally, It may be a liquid mixture of esterification products containing adipic acid ester, oxycaproic acid ester and the like as the main components, which are obtained by separating and purifying the product of the esterification reaction by an appropriate means.

In this invention, the liquid mixture of the esterified product is
About adipic acid ester and oxycaproic acid ester,
It contains 10 to 80% by weight, especially about 50 to 70% by weight, and has an acid value (AV value) of about 1.0 to 50 mgKOH / g, especially 1.5 to 20 mgKOH.
/ g is preferable, and if necessary, the esterified product is a suitable organic solvent at a concentration of about 30 to 70% by weight (especially, an organic solvent used for extracting the carboxylic acid compound described below, ).

As a method for separating carboxylic acids from the cyclohexane oxidation reaction solution, for example, the cyclohexane oxidation reaction solution is saponified with an alkaline aqueous solution such as caustic soda, and the aqueous layer is separated to obtain various carboxylic acid salts. To obtain an alkaline solution containing sulfuric acid, and neutralizing the alkaline solution with sulfuric acid to a pH of 3 or less to produce Glauber's salt and carboxylic acids, and the Glauber's salt aqueous solution of the aqueous layer separated from the neutralized solution. From the various carboxylic acids mentioned above, methyl ethyl ketone,
Extraction with ketones such as methyl isobutyl ketone and cyclohexane, esters such as ethyl acetate, butyl acetate and methyl caproate, and lower alcohols such as butyl alcohol and isopropyl alcohol to obtain carboxylic acid compounds (mixture) be able to.

The method of hydrogenating the liquid mixture of the above-mentioned esterification product in the presence of a hydrogenation catalyst can be carried out by a known method, in particular, in the presence of a catalyst, a temperature of 200 to 400 ° C., particularly 250 to 300 ° C. It is preferable to carry out at a hydrogen partial pressure of 150 to 500 kg / cm ² G, especially 200 to 350 kg / cm ² G.

Examples of the hydrogenation catalyst include iron, nickel, cobalt, copper, and a hydrogenation catalyst containing copper-chromite as a main component, and the form thereof is in the form of powder or tablet. It may be present, and the amount used is about several wt% with respect to the liquid mixture of the esterified product obtained by esterifying the carboxylic acid compound.

In the present invention, the hydrogenation reaction solution obtained as described above is supplied to the first distillation column 1 and the second distillation column 2 as shown in FIG. The low boiling point of the hydrogenation reaction is removed from the top of the distillation column 1, the high boiling point of the hydrogenation reaction liquid is removed from the bottom of the second distillation column 2, and the high boiling point of the second distillation column 2 is removed. "Ester value (EV value)" is 10 to 10
0 mgKOH / g, preferably 10 to 50 mgKOH / g of crude 1,6-hexanediol ”is taken out, cooled and recovered in the crude 1,6-hexanediol tank 3 to remove the crude 1,6-hexanediol. It is manufactured.

The crude 1,6-hexanediol preferably contains 1,6-hexanediol in an amount of about 60% by weight or more, particularly about 70 to 90% by weight.

In the refining method of the present invention, for example, as shown in FIG. 1, the crude 1,6-hexanediol obtained as described above is supplied from the tank 3 to the bottom of the saponification column 4 and at the same time. , Preferably about 2 to 20% by weight, especially 5 to 5%
An alkaline aqueous solution such as caustic soda of 15% by weight is supplied to the lower part of the saponification tower 4, and the trace amount of the ester compound in the crude 1,6-hexanediol is heated to 50 to 200 ° C. inside the saponification tower 4, preferably Is saponified at a temperature of 80 to 150 ° C. and a pressure of 1 to 15 kg / cm ² G, the saponified liquid after the saponification is supplied to the stripper column 5, and the saponification liquid in the saponified liquid is supplied from the top of the column. The low boiling substances such as water are removed by evaporation, and the bottom liquid of the stripper tower 5 is supplied to the evaporation tower 6 such as a thin film evaporator, and the high boiling substances such as alkali salts of organic carboxylic acid in the saponification liquid are supplied. While removing the substance from the bottom, "Ester value (EV value) is 5 mgKOH / g or less, preferably 1 mgKOH / g
"1,6-hexanediol" below is evaporated from the top of the column, the evaporate is cooled and recovered, and "evaporant mainly containing 1,6-hexanediol" is received in the evaporating liquid tank 7, In addition, the evaporation liquid mainly containing 1,6-hexanediol is supplied to a rectification column 8 in which a multi-stage perforated plate or packing is installed or packed, and middle boiling substances are removed from the top of the column. The 1,6-hexanediol purified by distillation is recovered from the middle stage of the rectification column 8 while removing high-boiling substances from the column bottom, and is received in the 1,6-hexanediol product tank 9.

In the saponification step of the crude 1,6-hexanediol,
The amount of alkaline aqueous solution supplied to the saponification tower depends on the alkali concentration.
In terms of 100% by weight, the amount of crude 1,6-hexanediol supplied is preferably 0.001 to 1 times by weight, and particularly preferably 0.05 to 0.2 times by weight.

Further, the saponification tower, if it is a tubular tower having a hollow interior, in particular, such as size and shape may not be specified, in particular, a plurality of hollow inside (especially 2-10
Individual) baffle plates are arranged alternately and are hollow tower-type saponification towers, or hollow tower-type saponification towers having a built-in stirrer, or, for example, static It is preferable to use a static in-tube mixer such as a mixer or a high mixer to improve the mixing and dispersion, and then supply the mixture to the hollow saponification tower because the saponification liquid is preferably stirred.

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

〔Example〕

Hereinafter, the production method of the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 [Production of Esterification Mixture] An alkaline liquid obtained by saponifying a liquid phase oxidation reaction liquid obtained by aerial oxidation of cyclohexane with caustic soda is neutralized with sulfuric acid. Water balance is made so that the specific gravity of the aqueous Glauber's salt solution in the water layer is 1.25, and the neutralized solution is separated into an aqueous layer and an oil layer, and then adipic acid, oxycaproic acid, etc. contained in the aqueous Glauber's salt solution in the aqueous layer Is extracted with methyl isobutyl ketone (MIBK), and MIBK is removed from the extract by evaporation to obtain a mixture of carboxylic acid compounds.

An aqueous solution of the mixture of carboxylic acid compounds (concentration: 63.5% by weight) was added with an aqueous solution of 1,6-hexanediol under normal pressure to
An esterification reaction was carried out at a temperature of 0 to 260 ° C. to obtain “an esterified product mixture having an adipate content of 34.7% by weight and an oxycaproic acid ester content of 40.5% by weight”. .

[Hydrogenation process]

Copper-chromite catalyst 0.6 wt% was added to the esterified product mixture obtained as described above, and the hydrogen pressure was 290 kg / c.
A hydrogenation reaction was carried out at m ² G and a temperature of 260 to 275 ° C. to produce 1,6-hexanediol, and a hydrogenation reaction liquid containing 1,6-hexanediol was obtained.

The hydrogenated reaction solution obtained as described above has an EV value of 25.6 mg.
KOH / g, the concentration of 1,6-hexanediol is 61.1% by weight, and 8.8% by weight of 1,5-pentanediol,
Hexanol 2.3% by weight, amyl alcohol 3.2% by weight,
It contained 0.8% by weight of water and 23.8% by weight of other low boiling compounds.

[Production of Crude 1,6-Hexanediol] According to the production flow shown in FIG. 1, first, the hydrogenation reaction solution obtained as described above is fed into the first distillation column 1 at a feed rate of 541 kg / hour. It is fed to the middle stage, and low boiling substances such as hexanol, amyl alcohol, and water are evaporated and distilled off at 71 kg / hour from the top of the column, and then the bottom liquid of the first distillation column 1 is distilled into the second distillation column. 2 is supplied to the middle stage, and high-boiling substances of 15 kg / hour are discharged from the bottom of the second distillation column 2 and the crude distillation is performed from the top of the second distillation column 2.
Take out 6-hexanediol at a rate of 455 kg / hr and
Received in 1,6-hexanediol tank 3.

The crude 1,6-hexanediol has a concentration of 1,6-hexanediol of 75.0% by weight and an ester value (EV value) of 1
2.1 mg KOH / g and 1,5-pentanediol 12.4
% By weight, 1.7% by weight of hexanol, 0.7 of amyl alcohol
%, And 10.2% by weight of other components.

[Saponification step and purification step]

Then, crude 1,6-hexanediol is supplied from the crude 1,6-hexanediol tank 3 at a rate of 455 kg / hour to the bottom of a hollow tower type saponification tower 4 internally provided with a large number of baffle plates alternately arranged. At the same time, a 10 wt% caustic soda aqueous solution was fed to the lower part of the saponification tower 4 at 86 kg / hour, and the crude 1,6-hexane was retained at the saponification tower for 30 minutes at a saponification temperature of 80 ° C. The diol is saponified, and the saponification liquid is supplied to the middle stage of the stripper tower 5, and water and low-boiling substances are supplied from the top of the stripper tower 5.
At the same time as evaporating 5 kg / hour and distilling off, the can liquid of the stripper tower 5 (content of 1,6-hexanediol in the can liquid; 75.0% by weight, EV value of the can liquid; 2 mgKOH / g) was extracted, Further, the bottom liquid is supplied to the upper part of the thin film evaporation tower 6, and the high boiling substance containing carboxylic acid alkali salt or the like is supplied at 35 kg / hour.
EV value is 1.0mgKOH / g while removing from the bottom of 1,6-
Hexanediol was obtained by evaporating from the top of the thin-film evaporation column 6, and finally, the 1,6-hexanediol was distilled and purified in the rectification column 7, and the EV value was 0.4 mgKOH / g. -Hexanediol was continuously produced at 287 kg / hr and received as product in 1,6-hexanediol product tank 9.

Example 2 As a saponification tower, a stirring tank containing a stirrer was used, and
1,6-Hexanediol was produced in the same manner as in Example 1 except that the saponification reaction of 1,6-hexanediol was carried out at 130 ° C. for 30 minutes.

In the above-mentioned production method, the evaporate obtained from the top of the thin film evaporator had a 1,6-hexanediol content of 76.8% by weight, an EV value of 0.5 mgKOH / g, and a product tank
The 1,6-hexanediol had a 1,6-hexanediol content of 99.5% by weight and an EV value of 0.15 mgKOH / g.

Comparative Example 1 1,6-hexanediol was produced in the same manner as in Example 1 except that the saponification tower was not used at all.

In the above-mentioned production method, 1,6-hexanediol in the product tank had a 1,6-hexanediol content of 98.6% by weight and an EV value of 10 mgKOH / g.

[Operation and effect of the present invention]

This invention is a "mixture of esterified products" obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane.
The crude saponification 1,6-hexanediol with a high ester value (EV value) obtained by distilling the hydrogenation reaction liquid to produce 1,6-hexanediol Is saponified by contacting it with an alkaline aqueous solution with a stripper column and an evaporation column to remove low-boiling substances and high-boiling substances, and finally, by distillation purification, the EV value is low and high. It has the effect of producing pure 1,6-hexanediol.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a purification flow for carrying out the purification method of 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: Stripper column, 6: Evaporation column,
7: Evaporator tank, 8: Fractionation tower, 9: 1,6-hexanediol product tank.

Claims (1)

[Claims] 1. A 1,6-hexanediol is produced by hydrogenating a mixed solution of esterified products obtained by esterifying a carboxylic acid compound by oxidation of cyclohexane with alcohols, and a distillation operation from the hydrogenated reaction solution. Removes low-boiling substances and high-boiling substances with an ester value (EV value) of 10 to 100 mgKOH / g
To obtain crude 1,6-hexanediol, and then saponify the crude 1,6-hexanediol with an alkaline aqueous solution in a saponification tower, and supply the solution after saponification to a stripper tower. Evaporate and remove the boiling point, supply the stripper tower can to the evaporation tower and remove the high boiling point from the bottom while removing 1,6-hexanediol with an ester value (EV value) of 5 mgKOH / g or less. A method for purifying 1,6-hexanediol obtained by evaporating from the top and finally purifying the 1,6-hexanediol by distillation in a rectification column.