JP6375811B2 - Method for producing 1,6-hexanediol precursor composition - Google Patents

Description

  The present invention relates to a method for producing a 1,6-hexanediol precursor composition. The 1,6-hexanediol precursor composition can be converted to 1,6-hexanediol by hydrogen reduction.

  Conventionally, it is known that a 1,6-hexanediol precursor composition is produced by, for example, the following method.

  In Patent Document 1, a liquid phase oxidation reaction liquid (containing adipic acid, hydroxycaproic acid, etc.) obtained by air oxidation of cyclohexane is brought into contact with an aqueous sodium hydroxide solution, and the organic acid is converted into a sodium salt as an aqueous phase. After extraction, the resulting aqueous solution was neutralized by adding sulfuric acid, and extracted by adding methyl isobutyl ketone to the reaction solution after neutralization to obtain an organic solvent solution containing a carboxylic acid mixture, After concentrating the solution, it was mixed with an aqueous solution of 1,6-hexanediol and esterified at 200 to 260 ° C. under normal pressure, whereby the content of adipic acid ester was 34.7% by mass and hydroxycaproic acid. It is disclosed that a liquid mixture of esterified products having an ester content of 40.5% by mass and an acid value of 3.1 mgKOH / g was obtained. (Example 1).

  In Patent Documents 2 and 3, a carboxylic acid mixture (aqueous solution) produced by a conventional method is esterified with a reaction solution for hydrocracking prepared by the method described in Example 1 of Patent Document 1, It is disclosed that an esterified product having an acid value of 0.8 mg KOH / g was obtained (both in the former part of the examples).

In Patent Document 4, by esterifying a solution containing adipic acid, hydroxycaproic acid and water and crude 1,6-hexanediol at 220 ° C. and 1 to 1.4 bar (absolute pressure), Oligomer mixture mainly containing ester consisting of carboxylic acid derivative and diol by distilling off low boiling point components after esterification until acid value is less than SZ (meaning SZ is unknown) less than 10 mg KOH / g (Example).
In this document, the preferred range of the acid value is described in paragraph No. 0088, but since it is described as “particularly advantageously 5 to 10 mg KOH / g”, it is considered to be 5 mg KOH / g. Is considerable.

  Patent Document 5 contains adipic acid, hydroxycaproic acid and water, and a partially oligomeric dicarboxylic acid solution (DCL) and 1,6-hexanediol are mixed together at 220 ° C., 1-1. Contains ester consisting mainly of carboxylic acid derivative and diol by distilling off low-boiling components after esterification by esterification at .4 bar (absolute pressure) until acid value is 6 mgKOH / g It was disclosed that an oligomer mixture was obtained (Example).

JP-A-3-115237 JP-A-7-165543 JP 7-233108 A Special table 2012-523386 gazette Special table 2013-537882 gazette

  However, the methods of Patent Documents 1 to 3 have a problem that a large amount of organic solvent must be used in order to efficiently extract the carboxylic acid mixture.

  In any case, the acid value was 5 mgKOH / g or more. Therefore, in the production of 1,6-hexanediol by hydrogen reduction using the ester composition, there are still problems such as rapid deterioration of the catalyst and corrosion of the inner wall of the production apparatus. It was.

On the other hand, the present inventors newly found the following problems regarding industrial production of 1,6-hexanediol.
That is, in the subsequent hydrogen reduction step (diol production step), since it is necessary to transfer the 1,6-hexanediol precursor composition (esterified product), the composition at the temperature (200 to 210 ° C.) at the time of transfer. The problem was found that the viscosity of the resin must be kept as low as possible.
In addition, in the hydrogen reduction process, in order to perform sufficient hydrogen flow (bubbling) and smooth stirring, the viscosity of the composition must be kept as low as possible at the temperature (240 to 250 ° C.) during hydrogen reduction. I found a problem.

Furthermore, although most of the 1,6-hexanediol precursor composition (esterified product) is an oligomer, there is a need to lower the average molecular weight to obtain a precursor composition that does not affect hydrogen reduction. I found it.
All of the above problems are newly recognized as problems to be achieved while maintaining a low acid value.

  The object of the present invention is to solve the above problems and to have a low acid number, low viscosity at the time of transfer and hydrogen reduction, and low average molecular weight, suitable for industrial production of 1,6-hexanediol. It is in providing the manufacturing method of a 6-hexanediol precursor composition.

The subject of the present invention is an organic acid mixture based on adipic acid and hydroxycaproic acid (mostly present as oligomers),
A hydrogen reduction product mainly composed of 1,6-hexanediol,
[OH] / [COOH] is 1.1 to 2.0.
([COOH] represents the number of moles of the carboxyl group of the monocarboxylic acid or dicarboxylic acid contained in the organic acid mixture, and [OH] represents the number of moles of the hydroxyl group of the monoalcohol or diol contained in the hydrogen reduction product. )
Mixed so that
Solved by a method for producing a 1,6-hexanediol precursor composition, characterized by reacting while maintaining this range after the water content in the mixture is 0.01-0.2 mass%. The

  According to the present invention, it is possible to provide a method for producing a 1,6-hexanediol precursor composition that is optimal for industrial production of 1,6-hexanediol.

It is a flowchart at the time of recycling utilization of the hydrogen reduction product of this invention. 6 is a schematic diagram of a manufacturing apparatus used in Example 3. FIG.

  The 1,6-hexanediol precursor composition of the present invention comprises an organic acid mixture mainly composed of adipic acid and hydroxycaproic acid (mostly present as an oligomer), and hydrogen reduction mainly composed of 1,6-hexanediol. This is produced by mixing the product with water and making the water content in the mixed solution 0.01-0.2% by mass, and then reacting while maintaining this range (hereinafter also referred to as esterification reaction). Is done.

  In the esterification reaction, the reaction between a carboxyl group and a hydroxyl group is an equilibrium reaction in which water is generated as a by-product. The reaction of 1 molecule of adipic acid and 2 molecules of 1,6-hexanediol is shown below.

  Therefore, unless water is removed from the reaction solution, a reverse reaction occurs, and the target ester cannot be obtained sufficiently. In the case of this invention, when a reverse reaction occurred, there existed a problem that the acid value of a 1, 6- hexanediol precursor composition (ester mixture) will become high.

  On the other hand, when water is completely removed or the reaction is carried out with a high concentration substrate, the esterification proceeds very quickly, and the reaction proceeds to the oligomer (ester multimer) without staying with the ester monomer. There was also a problem of progress.

(In the formula, n represents a repeating unit.)
If a large amount of oligomers are produced, the average molecular weight of the 1,6-hexanediol precursor composition (ester mixture) is improved, which may affect the production of 1,6-hexanediol by subsequent hydrogen reduction. .
Further, when the viscosity of the composition is increased, as described above, there is a possibility of adversely affecting the agitation during transfer and hydrogen reduction.

  As described above, the acid value increases as the water content in the liquid increases, and the oligomerization is promoted as the water content decreases. Therefore, it is necessary to finely control the content of water in the liquid.

  Therefore, as in the present invention, by increasing the water content in the mixed solution to 0.01 to 0.2% by mass and reacting while maintaining this range, the acid value is increased and the average molecular weight is increased. Increase and increase in viscosity can be suppressed.

(Organic acid mixture)
The organic acid mixture of the present invention is mainly composed of adipic acid and hydroxycaproic acid and contains 28 to 34% by mass of adipic acid and 30 to 43% by mass of hydroxycaproic acid, most of which is present as an oligomer. doing.

  The oligomer is mostly composed of, for example, an oligomer composed of a unit originating from adipic acid (the following left formula) or a unit originating from hydroxycaproic acid (the following right formula).

  The organic acid mixture may be prepared by mixing the respective components. For example, the organic acid mixture may be prepared by extracting water from a liquid phase oxidation reaction solution obtained by air oxidation of cyclohexane by the method described in Patent Document 1. It is desirable to use it from an economical viewpoint.

In this case, in addition to adipic acid, hydroxycaproic acid and oligomers thereof, for example, dicarboxylic acids such as glutaric acid and succinic acid; monocarboxylic acids such as caproic acid, pentanoic acid, isopentanoic acid and butanoic acid; hydroxypentane Hydroxy monocarboxylic acids such as acid and hydroxybutanoic acid; carboxylic acid components such as formylmonocarboxylic acid such as formylpentanoic acid and formylbutanoic acid.
Moreover, cyclohexanol, cyclohexanone, etc. may be included as a neutral component, The said dicarboxylic acid and hydroxymonocarboxylic acid may exist as an oligomer.

  The water content of the organic acid mixture of the present invention is preferably 0.01 to 4.0% by mass, more preferably 0.05 to 3% by mass. By setting it as this range, the moisture content in the liquid mixture obtained by mixing the organic acid mixture and 1,6-hexanediol can be controlled within an appropriate range.

  The acid value of the organic acid mixture of the present invention is preferably 300 to 500 mgKOH / g, more preferably 370 to 430 mgKOH / g.

  The melting point of the organic acid mixture is preferably 70 to 85 ° C, more preferably 75 to 80 ° C.

(Hydrogen reduction product)
The hydrogen reduction product of the present invention is a hydrogen reduction product containing 1,6-hexanediol as a main component (hereinafter sometimes referred to as a hydrogen reduction product), and is adipic acid ester, hydroxycaproic acid ester, or an acid thereof. The carboxylic acid ester mixture containing the oligomer ester is hydrogen-reduced.

  As the hydrogen reduction product, a hydrogen reduction product mainly composed of 1,6-hexanediol obtained by a hydrogen reduction reaction of the 1,6-hexanediol precursor composition of the present invention is preferably used from an industrial viewpoint. The Since most of the hydrogen reduction product is subjected to purification of 1,6-hexanediol, the hydrogen reduction product is used by circulating a part of the total hydrogen reduction product.

  Moreover, after the hydrogen reduction, the low-boiling components may be removed as necessary, so that the composition of the mixture does not change greatly. Pure 1,6-hexanediol can be used as it is.

  The hydrogen reduction product used in the present invention includes not only 1,6-hexanediol obtained by the hydrogen reduction reaction, but also 1,5-pentanediol derived from glutaric acid ester or hydroxypentanoic acid ester, or succinic acid ester. 1,4-butanediol derived from hydroxybutanoic acid ester may be included.

  The content of 1,6-hexanediol in the hydrogen reduction product is preferably 50% by mass or more, and more preferably 55% by mass or more. By setting it as this range, the productivity of 1,6-hexanediol is maintained high.

  The water content in the hydrogen reduction product is preferably 0.01 to 3% by mass, more preferably 0.5 to 2% by mass. By setting it as this range, the moisture content in the liquid mixture obtained by mixing the organic acid mixture and 1,6-hexanediol can be controlled within an appropriate range.

(Mixed solution consisting of organic acid mixture and hydrogen reduction product)
The liquid mixture composed of the organic acid mixture and the hydrogen reduction product is generated by mixing the organic acid mixture and the hydrogen reduction product. For example, the organic acid mixture and the hydrogen reduction product are supplied to the same reactor. Is done by.
In the mixture, the mixing ratio of the organic acid mixture and the hydrogen reduction product is as follows:
The number of moles of the carboxyl group of the monocarboxylic acid or dicarboxylic acid contained in the organic acid mixture is [COOH],
When the number of moles of the hydroxyl group of the monoalcohol or diol contained in the hydrogen reduction product is [OH],
[OH] / [COOH] is supplied and mixed so as to be preferably 1.1 to 2.0, more preferably 1.2 to 1.8.
The number of moles of the carboxyl group and hydroxyl group at this time can be measured by a neutralization titration method or potentiometric titration method using potassium hydroxide.

The supply rate of the organic acid mixture and the hydrogen reduction product depends on the size of the mixing container, but satisfies the range of [OH] / [COOH], and the water content in the mixed solution is 0. Although it will not be restrict | limited especially if it can maintain this range after setting to 0.01-0.2 mass%,
The supply amount of the organic acid mixture is preferably 1100 to 1500 L / h, more preferably 1200 to 1400 L / h,
The supply amount of the hydrogen reduction product is preferably 1000 to 1400 L / h, more preferably 1100 to 1300 L / h.

(Synthesis of precursor mixture (ester mixture))
In the 1,6-hexanediol precursor composition (ester mixture) of the present invention, for example, the above mixed solution is preferably heated to 200 to 300 ° C., more preferably 220 to 280 ° C. After the content is adjusted to 0.01 to 0.2% by mass, the reaction is performed while maintaining this range. The pressure at that time is not particularly limited, but when a self-pressure is applied, it is desirable to use a pressure vessel.

  Although a large amount of water is generated in the reaction, it is also possible to maintain the water content while removing water while entraining water as an inert gas (for example, nitrogen). In addition, it is desirable to carry out the reaction while removing low-boiling components and by-product low-boiling components contained in the organic acid mixture or hydrogen reduction product.

  The obtained ester mixture is the 1,6-hexanediol precursor composition of the present invention, and has the following physical property values.

  The acid value of the precursor composition in the present invention is 2 mgKOH / g or less, more preferably 1 mgKOH / g or less. By setting it as this range, rapid deterioration of the catalyst used in the subsequent hydrogen reduction (diol production process) and corrosion in the production apparatus can be controlled.

The viscosity at 200 ° C. and 250 ° C. of the precursor composition in the present invention was estimated using a rotary viscometer.
For example, the viscosity at 200 ° C. and 250 ° C. can be estimated by measuring a plurality of viscosities at 50 to 150 ° C. and calculating an approximate expression in consideration of temperature dependence therefrom.
The estimated value of the viscosity at 200 ° C. is 20 cp or less, more preferably 15 cP or less. By setting it as this range, transfer of a precursor composition becomes easy.
The estimated value of the viscosity at 250 ° C. is 15 cP or less, more preferably 10 cP or less. By setting it as this range, in a hydrogen reduction process, sufficient hydrogen circulation (bubbling) and smooth stirring can be performed.
In addition, if the viscosity of kerosene at 20 ° C. is 10, and if it is equal to or less than this viscosity, stirring during transfer and hydrogen reduction can be performed smoothly.

  The molecular weight of the precursor composition in the present invention is a value measured using gel permeation chromatography (GPC), and is 2000 or less, more preferably 1800 or less. By setting this range, the hydrogen reduction reaction proceeds smoothly.

  In the present invention, in order to "react while maintaining this range after the water content in the mixed solution is 0.01 to 0.2% by mass", the water content of the precursor composition is also usually 0.01 to 0.2% by mass.

(Hydrogen reduction reaction)
The hydrogen reduction reaction of the present invention can be performed by a general method such as bringing the precursor composition into contact with a catalyst in a hydrogen atmosphere.

  The catalyst used in the hydrogen reduction reaction is not particularly limited as long as it is a catalyst capable of converting an ester group into a hydroxyl group, but is preferably a solid catalyst containing copper, specifically, for example, a copper oxide-zinc oxide catalyst. , Copper oxide-chromium oxide catalyst, copper oxide-zinc oxide-aluminum oxide catalyst, copper oxide-zinc oxide-titanium oxide catalyst, copper oxide-iron oxide-aluminum oxide catalyst, copper oxide-silicon oxide catalyst, etc. A copper oxide-zinc oxide catalyst and a copper oxide-chromium oxide catalyst are preferably used. These catalysts may be used alone or in admixture of two or more, and the form thereof is not particularly limited and can be appropriately selected from forms such as powder, condyle, and tablet.

  The amount of the catalyst used is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, based on the precursor composition.

  The hydrogen reduction reaction of the present invention is performed by, for example, a method of mixing a precursor composition and a solid catalyst and heating and stirring in a hydrogen atmosphere. The reaction temperature in that case becomes like this. Preferably it is 100-350 degreeC, More preferably, it is 200-300 degreeC, Reaction pressure is 1-35 MPa, More preferably, it is 5-30 MPa.

As a preferred embodiment of the present invention, there is a method in which a hydrogen reduction product containing 1,6-hexanediol is recycled (FIG. 1).
(1) An organic acid mixture and a hydrogen reduction product (containing 1,6-hexanediol) are mixed.
(2) An esterification reaction is performed using the above mixed solution to produce a precursor composition.
(3) The precursor composition is subjected to a hydrogen reduction reaction to obtain a hydrogen reduction product containing 1,6-hexanediol as a main component.
(4) A part of the hydrogen reduction product is circulated and used in the mixed solution (1) with the organic acid mixture.
The other 1,6-hexanediol is purified to obtain a product with reduced impurities.
This method can provide a method for producing 1,6-hexanediol suitable for an industrial production scale.

Next, the present invention will be specifically described with reference to examples, but the scope of the present invention is not limited thereto. In addition, the following apparatus was used for the measurement of a viscosity and molecular weight.
Viscosity: Brookfield digital viscometer (model DV-II + Pro)
Molecular weight: HLC-8020 manufactured by Tosoh Corporation

Example 1A (Production of 1,6-hexanediol precursor composition)
In a glass container having an internal volume of 1 L, 369 g of an organic acid mixture having the following composition and 283 g of hydride having the following composition were mixed ([OH] / [COOH] = 1.7).
(Organic acid mixture)
Adipic acid; 28% by mass
Hydroxycaproic acid; 35% by mass
Water; 0.1% by mass
(Hydrogen reduction product)
1,6-hexanediol; 64% by mass
1,5-pentanediol; 11% by mass
Water; 1.0 mass%

Next, while raising the temperature to 240 ° C. while circulating nitrogen, the low boiling point component is removed and the mixture is reacted for 4.5 hours until the water content in the mixed solution is in the range of 0.01 to 0.2% by mass. It was.
After completion of the reaction, the obtained reaction solution (1,6-hexanediol precursor composition) was a novel composition having the following physical properties.

Acid value: 0.5 mg KOH / g
Viscosity at 200 ° C; 4.1 cP
Viscosity at 250 ° C .; 2.7 cP
Average molecular weight; 920

Example 1B (Production of 1,6-hexanediol)
120 g of the composition obtained in Example 1A and 1% by mass of a copper oxide-zinc oxide catalyst (based on the composition) were added to an autoclave having an internal volume of 200 mL, and the mixture was stirred at 245 ° C. and 27 MPa in a hydrogen atmosphere. For 5 hours.
The composition was transferred and supplied from the esterification reactor to the hydrogen reduction reactor, and stirring and convection during the hydrogen reduction were performed smoothly.
When the obtained reaction liquid was analyzed after completion of the reaction, the reaction yield of 1,6-hexanediol was 97% (based on adipic acid and hydroxycaproic acid in the organic acid).

Example 2A (Preparation of 1,6-hexanediol precursor composition)
In a glass container having an internal volume of 1 L, 391 g of an organic acid mixture having the following composition and 310 g of hydride having the following composition were mixed ([OH] / [COOH] = 1.7).
(Organic acid mixture)
Adipic acid: 26% by mass
Hydroxycaproic acid; 32% by mass
Water; 0.1% by mass
(Hydrogen reduction product)
1,6-hexanediol; 57% by mass
1,5-pentanediol; 9% by mass
Water; 1.0 mass%

Next, nitrogen was circulated to remove low-boiling components, and the water content in the mixed solution was adjusted to 0.01 to 0.2% by mass. Then, while maintaining this range, the temperature was raised to 250 ° C. The reaction was allowed for 5 hours.
After completion of the reaction, the obtained reaction solution (1,6-hexanediol precursor composition) was a novel composition having the following physical properties.

Acid value: 0.5 mg KOH / g
Viscosity at 200 ° C .; 9.2 cP
Viscosity at 250 ° C; 5.7 cP
Average molecular weight; 1290

Example 2B (Production of 1,6-hexanediol)
To an autoclave having an internal volume of 200 mL, 120 g of the composition obtained in Example 2A and 1% by mass of a copper oxide-zinc oxide catalyst (based on the composition) were added and stirred at 245 ° C. and 27 MPa in a hydrogen atmosphere. For 5 hours.
The composition was transferred and supplied from the esterification reactor to the hydrogen reduction reactor, and stirring and convection during the hydrogen reduction were performed smoothly.
When the obtained reaction solution was analyzed after completion of the reaction, the reaction yield of 1,6-hexanediol was 94% (based on adipic acid and hydroxycaproic acid in the organic acid).

Example 3A (Production of 1,6-hexanediol precursor composition)
For the reaction, the apparatus shown in FIG. 2 was used.
An organic acid mixture having the following composition was supplied to an esterification reactor at 1300 L / h and a hydride having the following composition was supplied at 1220 L / h and mixed ([OH] / [COOH] = 1.4).
(Organic acid mixture)
Adipic acid: 32% by mass
Hydroxycaproic acid; 32% by mass
Water; 0.08% by mass
(Hydrogen reduction product)
1,6-hexanediol; 55% by mass
1,5-pentanediol; 10% by mass
Water; 1.2% by mass

Next, nitrogen was circulated to remove low boiling point components, and the water content in the mixed solution was adjusted to 0.01 to 0.2% by mass. Then, while maintaining this range, the temperature was raised to 245 ° C. The reaction was carried out for 14 hours.
After completion of the reaction, the obtained reaction solution (1,6-hexanediol precursor composition) was a novel composition having the following physical properties.

Acid value: 0.7 mgKOH / g
Viscosity at 200 ° C .; 10.5 cP
Viscosity at 250 ° C; 6.5 cP
Average molecular weight; 1750

Example 3B (Production of 1,6-hexanediol)
While supplying the composition obtained in Example 3A to the hydrogen reduction reactor at 2200 L / h, the copper oxide-zinc oxide catalyst is 0.1 to 0.3% by mass (based on the composition). In addition to the hydrogen reduction reactor, the reaction was carried out at 270 to 280 ° C. and 27 to 28 MPa for 2 hours.
The composition was transferred and supplied from the esterification reactor to the hydrogen reduction reactor, and stirring and convection during the hydrogen reduction were performed smoothly.
When the obtained reaction solution was analyzed after completion of the reaction, the reaction yield of 1,6-hexanediol was 91% (based on adipic acid and hydroxycaproic acid in the organic acid).

  The above results are summarized in Table 1.

  From the above results, it can be seen that the 1,6-hexanediol precursor composition of the present invention is extremely effective in the industrial production of 1,6-hexanediol.

  The present invention relates to a method for producing a 1,6-hexanediol precursor composition. The 1,6-hexanediol precursor composition can be converted to 1,6-hexanediol by hydrogen reduction.

Claims (9)

(A) A step of obtaining an organic acid mixture mainly composed of adipic acid and hydroxycaproic acid (mostly present as an oligomer) without performing extraction with an organic solvent from cyclohexane,
(B) The organic acid mixture and a hydrogen reduction product mainly composed of 1,6-hexanediol,
[OH] / [COOH] is 1.1 to 2.0.
([COOH] represents the number of moles of the carboxyl group of the monocarboxylic acid or dicarboxylic acid contained in the organic acid mixture, and [OH] represents the number of moles of the hydroxyl group of the monoalcohol or diol contained in the hydrogen reduction product. )
And after making the water content in the mixed solution 0.01-0.2% by mass by heating, react while maintaining this range,
An acid value of 2 mgKOH / g or less,
The viscosity at 200 ° C. is 15 cP or less,
The viscosity at 250 ° C. is 10 cP or less,
Obtaining a 1,6-hexanediol precursor composition having a number average molecular weight of 2000 or less,
(C) The 1,6-hexanediol precursor composition was subjected to a hydrogen reduction reaction to obtain a hydrogen reduction product containing 1,6-hexanediol as a main component, and (D) obtained in step (C). A part of the hydrogen reduction product mainly composed of 1,6-hexanediol is recycled and used as the hydrogen reduction product mainly composed of 1,6-hexanediol in the step (B), and obtained in the step (C). Production of 1,6-hexanediol, comprising the step of obtaining 1,6-hexanediol by purifying another part of the hydrogen reduction product mainly comprising 1,6-hexanediol Method.   The manufacturing method of Claim 1 whose organic acid mixture contains 28-34 mass% adipic acid and 30-43 mass% hydroxycaproic acid.   The manufacturing method of any one of Claims 1-2 whose water content rate of an organic acid mixture is 0.01-4.0 mass%.   The manufacturing method of any one of Claims 1-3 whose acid value of an organic acid mixture is 300-500 mgKOH / g.   The manufacturing method of any one of Claims 1-4 whose melting | fusing point of an organic acid mixture is 70-85 degreeC.   The manufacturing method of any one of Claims 1-5 whose content rate of 1, 6- hexanediol in a hydrogen reduced product is 50 mass% or more.   The manufacturing method of any one of Claims 1-6 whose water content rate in a hydrogen reduced product is 0.01-3 mass%.   The manufacturing method of Claim 1 which performs process (A), (B), (C) and (D) continuously.   The manufacturing method according to claim 1, wherein the water content of the 1,6-hexanediol precursor composition is 0.01 to 0.2% by mass.

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