JPH0637412B2 - Crystallization production method of 1,6-hexanediol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to liquid phase oxidation of cyclohexane with a molecular oxygen-containing gas to produce a carboxylic acid compound, which is esterified with an alcohol, and further, From the mixture containing mainly 1,6-hexanediol obtained by hydrogenating the esterified product, polyurethane,
The present invention relates to a method for producing highly pure 1,6-hexanediol, which has applications in unsaturated polyesters, plasticizers, pharmaceuticals, agricultural chemicals and the like.

[Description of Prior Art]

Conventionally, various proposals have been made on a method for producing 1,6-hexanediol starting from liquid phase oxidation of cyclohexane with a gas containing molecular oxygen.

For example, in German Patent No. 1206417, a liquid phase oxidation reaction liquid of cyclohexane was extracted with water, and a mother liquor after removing most of adipic acid from an aqueous layer was esterified with alcohol, and then, A method for producing 1,6-hexanediol by hydrogenating an esterified product in the presence of a catalyst is described.

In U.S. Pat.No. 3,528,892, a liquid phase oxidation reaction liquid of cyclohexane is extracted with water, a water layer is subjected to steam distillation, and non-reacted substances such as unreacted cyclohexane, cyclohexanol and cyclohexanone are distilled off, A method for producing 1,6-hexanediol by esterifying a liquid with alcohol and then hydrogenating the esterified product in the presence of a catalyst is described.

In addition, Japanese Patent Publication No. 58-18482 discloses that (1) a liquid-phase oxidation reaction liquid of cyclohexane with a molecular oxygen-containing gas is 1
A step of adding 5 wt% to a saturated concentration of Glauber's salt aqueous solution in an amount of 0.01 to 0.3 part by weight to 1 part by weight of the reaction solution to separate into an aqueous layer and an oil layer; (2) separated in the above step Adipic acid, oxycaproic acid and their oligomers mainly contained in the aqueous layer are extracted with an organic solvent; (3) The extract obtained in the above step is a monohydric alcohol having 1 to 8 carbon atoms and A step of esterifying with one or more alcohols selected from the group consisting of polyhydric alcohols having 2 to 8 carbon atoms; (4) 150-300 in the presence of a catalyst, the carboxylic acid ester obtained in the above step ℃
At a temperature of 150 kg / cm ² G or more and under a hydrogen partial pressure of 150 kg / cm ² G or more.
A method for producing hexanediol is described.

Further, in Japanese Patent Publication No. 53-33567, (1) an alkaline liquid obtained when saponifying a liquid-phase oxidation reaction liquid of cyclohexane with a molecular oxygen-containing gas with caustic soda is added to pH 3 with sulfuric acid.
The step of neutralizing to below and separating the water layer and the oil layer by adjusting the concentration of Glauber's salt in the water layer to 15% by weight or more; (2) The oil layer separated in the above step contains almost all organic compounds. Extraction with a sodium sulfate aqueous solution having a sodium sulfate concentration of 15% by weight or more; (3) adipic acid and oxy, which are mainly contained in the aqueous layer separated in the above step (1) and the extract obtained in the above step (2). A step of extracting caproic acid and its oligomer with an organic solvent; (4) extracting the extract obtained in the above step from a monohydric alcohol having 1 to 8 carbon atoms and a polyhydric alcohol having 2 to 8 carbon atoms A step of esterifying with one or more alcohols selected from the group consisting of: (5) the carboxylic acid ester obtained in the above step in the presence of a catalyst, 150 to 300 ° C.
At a temperature of 150 kg / cm ² G or more and under a hydrogen partial pressure of 150 kg / cm ² G or more.
A method for producing hexanediol is described.

However, non-reacted substances such as unreacted cyclohexane, cyclohexanol, cyclohexanone and cyclohexyl hydroperoxide, dibasic substances such as adipic acid, glutaric acid, succinic acid, etc. Contains monobasic acids such as acids, caproic acid, valeric acid, butyric acid, oxycaproic acid, oxyvaleric acid, oxyacids such as oligomers thereof, esters of the acids, aldehydes, alcohols and various other unknown substances. Has been done.

Therefore, when the liquid phase oxidation reaction liquid of the molecular oxygen-containing gas of cyclohexane containing various compositions is used to perform the saponification / esterification / hydrogenation reaction for 1,6-hexanediol synthesis. , Adipic acid, oxycaproic acid and their oligomers, and other active ingredients for synthesizing 1,6-hexanediol, and a reaction solution containing homologues and isomers are produced from the coexisting acid.

By the way, in any of the methods described in the above patent specifications, a distillation operation is used to separate and purify 1,6-hexanediol from the reaction solution.

However, 1,6-obtained by distilling this reaction solution
The hexanediol fraction contains monoalcohols having similar boiling points, diol homologues and isomers, and high-boiling substances formed during the reaction. From such fractions, 1,6-hexanediol can be obtained. Selective separation by distillation is difficult for economical separation and purification.

Therefore, according to a conventionally known method of purifying a reaction liquid obtained by subjecting cyclohexane to a liquid-phase oxidation reaction liquid containing a molecular oxygen-containing gas through an esterification step and a hydrogenation step by a distillation operation, water (weight% ), AV value (acid value, which means mg of potassium hydroxide necessary to neutralize acidic substances contained in 1 g of the product), EV value (ester value, contained in 1 g of the product) The amount of potassium hydroxide required to completely saponify the resulting ester is said to be satisfactory), but the purity is low.

[Problems to be Solved by the Invention]

A method for purifying a reaction solution obtained by subjecting cyclohexane to a liquid-phase oxidation reaction solution using a molecular oxygen-containing gas through an esterification step, and then a hydrogenation step by a distillation operation, as described above, The 1,6-hexanediol fraction obtained by distillation contains monoalcohols, diol homologues and isomers having similar boiling points, and high boiling substances produced during the reaction. It is economically difficult to selectively separate 1,6-hexanediol by distillation, and there is a problem that the purity is low.

The object of the present invention is to esterify a liquid phase oxidation reaction solution of cyclohexane with a molecular oxygen-containing gas and then hydrogenate it, or 1,6-hexane obtained by further distilling this reaction solution. In the step of purifying the diol fraction, by-products that cannot be separated and purified by only the distillation operation are removed, and water and A
High purity 1,6 without sacrificing quality such as V value and EV value
-To provide a method for producing hexanediol.

[Means for Solving the Problems]

That is, the present invention provides: (A) a step of oxidizing cyclohexane to produce a carboxylic acid compound; (B) a step of esterifying the carboxylic acid compound produced in the step (A) with an alcohol; (C) the above The step of hydrogenating the esterified product obtained in the step (B) to generate a mixture mainly containing 1,6-hexanediol (hydrogenation treatment liquid); (D) the step (C) Hydrogenated solution, or 0.1 to 5 obtained by once distilling this hydrogenated solution
At least one solvent selected from the group consisting of 1,6-hexanediol distillate (crude diol solution) containing 0% by weight of by-product, and water or an organic ketone having 3 to 20 carbon atoms. And a step of heating the mixed solution to dissolve it uniformly; (E) the solution obtained in the step (D) is at 42 ° C. or lower, and in the step (D), A step of cooling to a temperature equal to or lower than the melting temperature to precipitate crystals of 1,6-hexanediol, separating the crystals and washing the crystals; and a method for producing 1,6-hexanediol.

[Detailed description of each requirement of the present invention]

Next, the method of the present invention will be specifically described for each step.

Steps (A) to (C) These steps use cyclohexane as a starting material,
This is a step of obtaining a product mixture mainly containing 6-hexanediol, and a conventionally known method, for example, the method described in the above-mentioned German Patent No. 1206417 or Japanese Patent Publication No. 53-33567 is adopted.

Step (D) In this step, a mixture mainly containing 1,6-hexanediol produced in the above step (C) (hydrogenation treatment liquid) or obtained from the hydrogenation treatment liquid by a method described later A crude diol solution is supplied.

The purpose of this step and the next step (E) is to heat the hydrogenated solution obtained in the step (C) or the crude diol solution obtained in this step with water or an organic ketone as a solvent. Utilizing the difference between the solubility of 1,6-hexanediol in water or organic ketones at the dissolution temperature and the solubility of 1,6-hexanediol in water or organic ketones at the temperature after cooling the heated solution. Then 1,
The purpose is to precipitate crystals of 6-hexanediol.

The solubility of 1,6-hexanediol in water or organic ketones tends to increase as the temperature rises. Particularly, the melting point of 1,6-hexanediol is 4
In the range close to 2 ° C, the solubility approaches infinity.

Therefore, in this step, the hydrogenation treatment liquid obtained in the step (C) or the crude diol liquid obtained in this step is first treated from the group consisting of the water or the organic ketone having 3 to 20 carbon atoms. At least one selected solvent is mixed with 0.01 to 2 parts by weight, preferably 0.1 to 1 part by weight of the solvent, relative to 1 part by weight of the hydrogenation treatment liquid or the crude diol liquid, and preferably 42 ° C or higher. It is heated to the point where it dissolves uniformly.

Therefore, for the purpose of this step and the following step (E), it is important to select the solvent to be used in the present invention.

Industrially applicable solvents are low-temperature, low-solubility 1,6-hexanediol, and by-products (monoalcohols, diol homologs and isomers having a boiling point close to that of 1,6-hexanediol). Etc., a solvent having a large solubility is suitable, and as described above, saturated aliphatic ketones or alicyclic ketones having 3 to 20 carbon atoms, preferably 4 to 15 carbon atoms may be used. is there.

Specific examples of the organic ketones satisfying these conditions include methyl isobutyl ketone, methyl ethyl ketone,
Saturated aliphatic ketones such as methyl propyl ketone, diethyl ketone, and methyl butyl ketone, cyclohexanone,
Examples thereof include alicyclic ketones such as methylcyclohexanone, and mixtures thereof.

Further, among the polar solvents, water has a relatively high solubility of 1,6-hexanediol at low temperature, but it is effective because it does not require a recovery and circulation device as compared with the case of the above ketone solvent. It can be a solvent.

By the way, as described above, the solubility of 1,6-hexanediol in the solvent is close to infinity in the range close to 42 ° C. which is the melting point of 1,6-hexanediol. The solvent may be added to the hydrogenation treatment liquid or the crude diol liquid and heated to at least 42 ° C. or more, but it is preferable to perform this operation while stirring with a stirrer in order to obtain a more uniform solution. Is good.

Next, the method for producing the crude diol liquid supplied to this step will be described.

The mixture (hydrogenation treatment liquid) mainly containing 1,6-hexanediol produced by the hydrogenation reaction of the esterified product in the step (C) is distilled to contain 0.1 to 50% by weight of a by-product. A 6-hexanediol distillate (crude diol solution) is obtained.

Distillation of the hydrogenated solution is performed in two stages.

That is, the mixture (hydrogenation treatment liquid) mainly containing the 1,6-hexanediol is treated with, for example, a preheater 21
It is preheated to 0 ° C. or higher and supplied to the first distillation column at a reflux ratio of 1:
1, under atmospheric pressure, distilled under the temperature condition of 120 ~ 230 ℃,
Water and monohydric alcohols (medium oil) are distilled from the top, and the bottom liquid is led to the second distillation column.

In the bottom liquid of the first distillation column from which water and medium oil have been cut,
Unreacted ester remains. Among these esters, there are high-boiling esters and low-boiling esters which become diols when hydrogenated. In the second distillation column, for example, vacuum distillation is performed under a reduced pressure of 40 mmHg and a temperature condition of 170 to 230 ° C.,
1,6-hexanediol distillate (crude diol) containing 0.1 to 50% by weight of by-products (monoalcohols, diol homologs and isomers having a boiling point close to that of 1,6-hexanediol) from the top. The liquid) is distilled off, and the ester of the can liquid is recovered in the hydrogenation treatment step [(C) step].

As the model of the distillation column, a packed column or a bubble column is used.

Step (E) A heated solution of the hydrogenation treatment solution obtained in the step (C) or the crude diol solution obtained in the step (D) and a solvent which is water or an organic ketone is heated to 42 ° C or lower. In addition, by cooling to a temperature that is not higher than the dissolution temperature and using the difference in the solubility of 1,6-hexanediol with respect to the water or the solvent that is an organic ketone depending on the temperature, 1,6-hexane is used. After precipitating a crystal of diol and separating the crystal, the same solvent as that used for the heating dissolution was added to 1,
Washing is performed using 5 to 30% by weight, preferably 10 to 20% by weight, based on the weight of crystals of 6-hexanediol.

In this case, the heated solution is directly cooled by an internal cooling device such as an internal spiral tube provided in the crystallizer or an external jacket or other external cooling device, and the solvent is evaporated under reduced pressure to evaporate latent heat of evaporation. Cooling method (when the solvent is water, this method is particularly advantageous because it eliminates the need for a recovery and circulation device, etc.), or other cooling methods that are commonly used industrially. Is done.

In addition, for the separation after crystallization of 1,6-hexanediol, a centrifuge may be used, filtration separation by a filter may be performed, or any other method capable of easily separating crystals may be used. Any method may be used.

After the crystal separation, the by-product contained in the hydrogenation treatment liquid or the crude diol liquid migrates to the mother liquor side, so that the same solvent as that used for the warming dissolution is used to form the produced crystal. After washing the attached mother liquor, the solvent attached to the crystals is further removed by, for example, heating under reduced pressure.

In the washing of the 1,6-hexanediol crystal with the solvent, 1,6-hexanediol itself also migrates to the mother liquor side by an amount corresponding to its solubility.
It is also necessary to recover 1,6-hexanediol contained in the mother liquor.

Therefore, the present invention was made possible by inventing a solvent having such a great effect, so that 1,6 such as oxycaproic acid, adipic acid and their oligomers can be obtained from a liquid phase oxidation reaction liquid of cyclohexane with a molecular oxygen-containing gas. -To extract the active ingredient for hexanediol synthesis, these acids are extracted and separated under economical extraction conditions, and after stopping the stage of obtaining the low-purity active ingredient, the crystals are passed through the diol synthesis process. High purity of 1,6
-A method for producing hexanediol has been established.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Cyclohexane was subjected to liquid-phase oxidation with a gas containing molecular oxygen, and then an alkali waste liquid obtained by saponification treatment with a caustic soda aqueous solution was subjected to a neutralization / solvent extraction step to esterify a carboxylic acid compound with an alcohol. After that, the esterified product is subjected to hydrogenation treatment to obtain 60% by weight of 1,6-hexanediol (melting point: 42 ° C), 9% by weight of 1,5-pentanediol (melting point: -18 ° C) as a main component, and n. A hydrogenation treatment liquid containing 1% by weight of butyl alcohol (melting point: -90.2 ° C) and 1% by weight of n-amyl alcohol (melting point: -79 ° C) was obtained.

An equal weight of methyl isobutyl ketone was added to this hydrogenated solution, heated at 60 ° C. to dissolve the solution, and then the solution was gradually cooled to 3
Since crystals start to precipitate at 0 ° C., after further slow cooling and holding at 15 ° C., in order to perform crystal separation, filtration with filter paper is carried out, and in order to remove the mother liquor adhering to the separated crystal surface, After washing with an amount of the solvent corresponding to 10% of the weight of the crystal, the solvent attached to the crystal is removed at a vacuum degree of 40%.
It was removed under conditions of mmHg and 120 ° C. to obtain purified 1,6-hexanediol.

The recovery rate of 1,6-hexanediol was 85%. The effect of purity is that the value of 60% before purification is 9% after purification.
9% was obtained, and the effect of removing impurities and purification was obtained.

Example 2 1,6-hexanediol was produced in the same manner as in Example 1 except that an equal weight of methyl ethyl ketone was added in place of methyl isobutyl ketone to the hydrogenation treatment liquid obtained in Example 1.

The recovery rate of 1,6-hexanediol is 60%,
A purity of 99% was obtained.

Example 3 1,6-Hexanediol was produced in the same manner as in Example 1 except that the crystal separation was performed with a centrifuge instead of the filter paper.

The recovery rate of 1,6-hexanediol is 90%,
A purity of 99% was obtained. In addition, the KZ value (1, 1, which indicates potassium permanganate consumption as an index of impurities,
The reducing substance in 6-hexanediol is reacted with potassium permanganate in an acidic aqueous sulfuric acid solution, and is calculated from the consumption amount. The number of meters of N / 10KMnO ₄ solution consumed per 1 kg of 1,6-hexanediol is m. It is represented by. ), A value of 350 m / kg before purification and a value of 10 m / kg after purification were obtained.

Example 4 1,6-hexanediol was added in the same manner as in Example 1 except that 0.2 times the amount (weight ratio) of water was added to the hydrogenation treatment liquid obtained in Example 1 instead of methisoisobutyl ketone. Manufactured.

The recovery rate of 1,6-hexanediol is 70%,
A purity of 94% was obtained.

Example 5 Cyclohexane was subjected to liquid phase oxidation with a gas containing molecular oxygen, and then saponified with an aqueous solution of caustic soda to obtain an alkali waste solution, which was then subjected to a neutralization / solvent extraction step to esterify a carboxylic acid compound with an alcohol. After that, from the mixed solution containing mainly 1,6-hexanediol (hydrogenation solution) obtained by hydrogenating the esterified product, 1,6-hexanediol (melting point: melting point: 42%), 72% by weight, 1,5-pentanediol (melting point: -18 ° C) 12% by weight, n-amyl alcohol (melting point: -79 ° C) 1.2% by weight, etc.
A hexanediol distillate (crude diol solution) was obtained.

An equal weight of methyl isobutyl ketone was added to this crude diol solution, and the solution was heated to 60 ° C. and dissolved, and then the solution was gradually cooled.
Since crystals start to precipitate at 30 ° C., after further slow cooling and holding at 15 ° C., in order to perform crystal separation, filtration with filter paper is carried out to further remove the mother liquor adhering to the separated crystal surface, After washing with an amount of the solvent corresponding to 10% of the weight of the crystals, the solvent still attached to the crystals is washed with a vacuum degree of 4
It was removed under the conditions of 0 mmHg and 170 ° C. to obtain purified 1,6-hexanediol.

The recovery rate of 1,6-hexanediol was 85%. The effect of purity is that the value of 72% before purification is 9% after purification.
8.5% was obtained, and the effect of removing and purifying impurities was obtained.

Example 6 The same procedure as in Example 5 was repeated except that an equal weight of methyl ethyl ketone was added to the 1,6-hexanediol distillate obtained in Example 5 in place of methyl isobutyl ketone.
Hexanediol was produced.

The recovery rate of 1,6-hexanediol is 85%,
A purity of 98% was obtained.

Example 7 1,6-Hexanediol was produced in the same manner as in Example 5, except that the crystal separation was performed using a centrifuge instead of the filter paper.

The recovery rate of 1,6-hexanediol is 90%,
A purity of 98.5% was obtained. The KZ value indicating the consumption of potassium permanganate, which is an index of impurities, was 350 m / kg before purification and 10 m / kg after purification.

Example 8 1,6-hexanediol was produced in the same manner as in Example 5, except that 0.2 times the amount (weight ratio) of water was added to the crude diol solution obtained in Example 5 in place of methyl isobutyl ketone. did.

The recovery rate of 1,6-hexanediol is 70%,
A purity of 96% was obtained.

[Explanation of effects]

As described above, the production method of the present invention is a reaction liquid obtained by separating a carboxylic acid compound from a liquid-phase oxidation reaction liquid with a molecular oxygen-containing gas of cyclohexane, esterifying it, and then hydrogenating it, or The 1,6-hexanediol distillate obtained by distilling the above-mentioned distillate contains monoalcohols, diol homologs and isomers having similar boiling points, and high-boiling substances produced during the reaction. It is difficult to selectively and economically separate and purify 1,6-hexanediol from such a reaction solution or distillate, and therefore, there is a problem that the purity is low. Water or a solvent which is an organic ketone is added to the reaction solution obtained by hydrogenation or the 1,6-hexanediol distillate obtained by distillation of the reaction solution, and dissolved by heating. , Cooled, by performing crystallization and crystal washing, with only distillation can remove the by-products which can not be separated and purified, as compared to the conventional distillation operation, water, AV
High purity 1 without degrading quality such as value, EV value, etc.
It is effective in providing a method for producing 6-hexanediol.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number for FI Technical location C07C 53/126 9356-4H (72) Inventor Tosui Takiguchi 10 10 1978, Kogushi, Ube City, Yamaguchi Prefecture Ube Kosan Co., Ltd.Ube Chemical Co., Ltd.Chemical Business Headquarters Development Department (72) Inventor Kosaku Ohata 10 1978, Kogushi, Ube, Yamaguchi Prefecture Ube Chemical Co., Ltd. Ube Chemical Co., Ltd.Chemical Business Headquarters Development Department Examiner Yoshihiko Funaoka

Claims (2)

[Claims] 1. (A) a step of oxidizing cyclohexane to form a carboxylic acid compound; (B) a step of esterifying the carboxylic acid compound produced in the step (A) with an alcohol; (C) the above ( The step of hydrogenating the esterified product obtained in the step B) to produce a mixture mainly containing 1,6-hexanediol (hydrogenation treatment liquid); (D) The step of producing the mixture in the step (C). A step of mixing the hydrogenation treatment liquid with water or at least one solvent selected from the group consisting of organic ketones having 3 to 20 carbon atoms, and heating the mixed liquid to uniformly dissolve it; E) The solution obtained in the step (D) is cooled to a temperature not higher than 42 ° C. and not higher than the dissolution temperature in the step (D) to precipitate crystals of 1,6-hexanediol. And a step of separating the crystals and washing the crystals. The process of hexane diol. 2. In the step (D), the hydrogenation treatment liquid obtained in the step (C) is distilled to obtain a 1,6-hexanediol distillate containing 0.1 to 50% by weight of a by-product ( A crude diol solution) is obtained, and the crude diol solution and water or a carbon number of 3 to
The mixture according to claim 1, wherein at least one solvent selected from the group consisting of 20 organic ketones is mixed, and the mixed solution is heated to be uniformly dissolved. The way you did.