JP3033882B2 - Method for producing diol compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1,6-hexanediol obtained by esterifying a carboxylic acid mixture separated from a liquid-phase air oxidation reaction solution of cyclohexane and hydrogenating the resulting ester with hydrogen. And a method for producing a diol compound such as 1,5-pentanediol and 1,4-butanediol. Such diol compounds are useful compounds used for polyurethane elastomers, synthetic resin additives, pharmaceutical and agricultural chemical intermediates, and the like.

[0002]

2. Description of the Related Art Liquid-phase air oxidation of cyclohexane provides
Cyclohexanol and cyclohexanone, which are useful as raw materials for the synthesis of ε-caprolactam, are industrially produced. After that, the produced esterified product is hydrocracked with hydrogen to produce the esterified product.

In the oxidation reaction of cyclohexane, various carboxylic acids are produced as by-products, for example, caproic acid, valeric acid, butyric acid, propionic acid and acetic acid as monobasic acids, and adipic acid and glutaric acid as dibasic acids. , Succinic acid, etc., and ε-oxycaproic acid or a cyclized product thereof, ie, ε-caprolactone, is generated as the oxyacid. It is known that a mixture of these carboxylic acids is separated and recovered by extracting the above-mentioned oxidation reaction solution with water or washing with an aqueous solution of sodium hydroxide or sodium carbonate (for example, catalyst, 33 ,
5, 341 (1991)).

As a method for producing a diol compound such as 1,6-hexanediol, a water-extracted carboxylic acid mixture is esterified with an alcohol, particularly a diol compound such as 1,6-hexanediol, and then hydrogenated. A method of separating a diol compound from a reaction solution obtained by hydrogenolyzing the esterified product with hydrogen at a reaction temperature of 200 to 350 ° C. under a pressure of at least atmospheric pressure using a copper-chromium-based catalyst as a catalyst. Known (Japanese Patent Publication No. 49-
27164).

As another method, a sodium salt of a carboxylic acid obtained by the above alkali washing is neutralized, and a mixture of a carboxylic acid containing adipic acid or oxycaproic acid as a main component is mixed with an organic compound such as methyl isobutyl ketone. After extraction with a solvent and esterification with a diol compound such as 1,6-hexanediol, 24 hours under a pressure of 200 to 300 kg / cm ² using a copper-chromium catalyst.
A method is also known in which the esterified product is hydrogenolyzed with hydrogen at a reaction temperature of 0 to 290 ° C to obtain a diol compound (see JP-B-53-33567).

[0006] After esterifying the carboxylic acid mixture separated from the liquid-phase air oxidation reaction solution of cyclohexane, the resulting ester is hydrogenolyzed with hydrogen to form a diol compound such as 1,6-hexanediol. In the production method, an alcohol containing a diol compound, which is a reaction product, as a main component is used as an esterifying agent.

This is because the esterification of the carboxylic acid mixture without a catalyst requires a high temperature of 200 ° C. or higher, and the use of a monohydric alcohol such as methanol or ethanol causes the reaction to proceed under a high pressure. This is unfavorably industrially because the equipment cost is high and the risk is high. It is also conceivable to use a catalyst such as sulfuric acid to carry out esterification at a lower temperature. However, in this case, problems such as separation of the catalyst and treatment of the waste liquid occur, so that an industrial production method is still required. Is not preferred. Therefore, as described above, as the esterifying agent,
Diol compounds such as 1,6-hexanediol, which have a significantly higher boiling point than lower monohydric alcohols and can be esterified under conditions of normal pressure and no catalyst, are suitably used. In particular, since a hydrogenolysis reaction solution containing 50% or more of a diol compound such as 1,6-hexanediol is itself a target product, a separation operation necessary when another alcohol is used for esterification is omitted. And more preferably used.

After the carboxylic acid mixture separated from the liquid-phase air oxidation reaction solution of cyclohexane is esterified, the resulting ester is hydrogenolyzed with hydrogen to give 1,6-
In the method for producing diols such as hexanediol, a copper-chromium-based catalyst is widely used as a hydrogenation catalyst as described above. This is because when a diol compound such as 1,6-hexanediol is used as an esterifying agent, the diol compound forms a polyester having a high molecular weight with a dibasic acid such as adipic acid, and a high reaction temperature of 250 ° C. or more for hydrogenolysis. Because of the need for temperature, a catalyst having high activity in the reaction at high temperature was required. Furthermore, the reaction solution obtained by the hydrogenolysis of such an esterified product has a high viscosity, and it is not easy to separate the catalyst from the reaction solution by filtration. It depends.

However, since this copper-chromium-based catalyst contains harmful chromium, special dust-proofing measures are required for handling the catalyst when using it, and special treatment is required for treating wastewater and wastewater discharged in the process. It has drawbacks such as the necessity of simple equipment. In particular, when the reaction is carried out under the condition of liquid phase suspension, since the catalyst component partially dissolves in the reaction solution, the product diol compound such as 1,6-hexanediol is separated from the reaction solution by distillation. The treatment of the distillation still remains is a problem.

Therefore, various chromium-free catalysts have been proposed in a method for producing an alcohol by hydrogenolyzing a carboxylic acid ester with hydrogen.
None of them have industrially satisfactory performance for application to the production of diol compounds such as hexanediol. For example, JP-A-63-141937
Japanese Patent Laid-Open Publication No. H11-15083 proposes a method for producing lauryl alcohol from methyl laurate using a catalyst comprising copper oxide and zinc oxide. However, when this catalyst is applied to the production of 1,6-hexanediol, there is a problem that the activity of the catalyst is higher than that of the copper-chromium-based catalyst, but its filtration and separation properties are extremely poor.

Japanese Patent Publication No. 58-50775 proposes a method for producing a corresponding alcohol from coconut oil fatty acid methyl ester using a catalyst in which copper oxide and iron oxide are supported on aluminum oxide. However, when this catalyst is applied to the production of 1,6-hexanediol, there is a problem in that the filtration and separation properties of the catalyst are equivalent to those of the copper-chromium catalyst, but the activity thereof is considerably low.

[0012]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a diol compound by esterifying a carboxylic acid mixture separated from a liquid-phase air oxidation reaction solution of cyclohexane and then hydrocracking the resulting ester with hydrogen. It is an object of the present invention to provide a method for industrially and efficiently producing a diol compound by using a hydrogenation catalyst which is excellent in both activity and filtration separation property and does not contain harmful chromium. .

[0013]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on known chromium-free copper-based catalysts. As a result, two types of chromium-free known copper-based catalysts were obtained. When the hydrocracking reaction is carried out using
Surprisingly, they have found that the activity of the catalyst is extremely high, and that the separation of the catalyst from the reaction solution by filtration is extremely easy, thereby completing the present invention.

That is, the present invention relates to a method for producing a diol compound by esterifying a carboxylic acid mixture separated from a liquid-phase air oxidation reaction solution of cyclohexane with an alcohol, and then hydrocracking the resulting ester with hydrogen. To
In the presence of a combined catalyst comprising a catalyst containing copper oxide and zinc oxide as main components and a catalyst in which copper oxide and iron oxide are supported on aluminum oxide, the esterified product is hydrocracked with hydrogen, and The present invention relates to a method for producing a diol compound, wherein the combined catalyst is separated by filtration from a hydrocracking reaction solution.

Hereinafter, the method of the present invention will be described in detail. The carboxylic acid mixture used in the present invention is separated and recovered from the oxidation reaction solution in producing cyclohexanol and cyclohexanone by subjecting cyclohexane to liquid phase air oxidation by a method such as water extraction or alkali washing. For example, as disclosed in JP-B-49-27164, the above-mentioned oxidation reaction solution is subjected to aqueous extraction to obtain dibasic acids such as monobasic acids such as caproic acid, valeric acid and butyric acid, adipic acid, glutaric acid and succinic acid. After separating an aqueous phase containing a basic acid and an oxyacid such as oxycaproic acid as a main component, a carboxylic acid mixture containing almost no cyclohexanol, cyclohexanone and monobasic acid is recovered by concentrating the aqueous phase. be able to.

Further, as disclosed in JP-B-53-33567, the cyclohexane oxidation reaction solution is washed with an aqueous sodium hydroxide solution, the washed solution is neutralized with dilute sulfuric acid, and then extracted with methyl isobutyl ketone. By concentrating the mixture, a carboxylic acid mixture containing dibasic acids such as adipic acid, glutaric acid and succinic acid, and oxyacids such as oxycaproic acid as main components can be recovered.

The esterified product used in the present invention is a carboxylic acid containing a dibasic acid such as adipic acid, glutaric acid and succinic acid, and an oxyacid such as oxycaproic acid, which are separated and recovered by the above method. By esterifying the mixture with an alcohol, an esterified product corresponding to the alcohol can be easily obtained. At this time, as the alcohol, for example, a monohydric alcohol such as methanol, ethanol, propanol and butanol, or a diol compound such as 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol is used. be able to. In this case, in order to carry out the esterification under normal pressure and no catalyst conditions, it is necessary to use an alcohol having a remarkably high boiling point without using a lower alcohol, and for this purpose, 1,6-hexanediol is used. It is preferable to use a hydrogenolysis reaction solution of the above esterified product containing 50% or more of 1,6-hexanediol.

The amount of alcohol used in the esterification reaction is usually determined by the acid value (AV: m
(g-KOH / g) is set such that the hydroxyl group of the alcohol is 1.2 to 1.5 times the equivalent. When this ratio is smaller than 1.2 times, the esterification reaction rate becomes extremely slow and the esterification reaction is not completed, so that the obtained esterified product has a high AV value and is a raw material for hydrocracking. This is undesirable. That is, when the AV value of the esterified product is 5 mg-KOH / g or more, the action of the acidic substance significantly dissolves the components of the hydrogenation catalyst during the hydrogenolysis reaction, and the activity thereof is reduced. Further, when the ratio is larger than 1.5 times, there is no problem in the esterification reaction, but since the throughput of the reaction solution in the esterification reaction and the hydrogenolysis reaction increases, the apparatus becomes large, and eventually the apparatus becomes large. In addition, a large amount of energy is required to recover the target diol compound.

The conditions other than those described above for the esterification reaction are not particularly limited, but usually the reaction temperature is 200 to 250 ° C.
The reaction is preferably carried out until the AV value of the reaction solution becomes 5 mg-KOH / g or less, preferably 2 mg-KOH / g or less. In addition, since the esterification reaction is an equilibrium reaction, the reaction can be completed quickly if the produced water is removed by vaporization with an inert gas such as nitrogen gas.

The hydrocracking reaction of the present invention is carried out by hydrocracking the esterified product obtained as described above with hydrogen. This hydrocracking reaction is usually
Reaction temperature of 250-300 ° C, preferably 270-30
At 0 ° C., the hydrogen pressure is 200-300 at this reaction temperature.
kg / cm ² , preferably 250-300 kg / cm ²
Is performed under the following conditions. When the reaction temperature is higher than 300 ° C., the amount of by-produced water increases, and when the hydrogen pressure is higher than 300 kg / cm ² , safety of the apparatus must be considered, which is not preferable.

In the present invention, a catalyst containing copper oxide and zinc oxide as main components (hereinafter referred to as A catalyst) and a catalyst in which copper oxide and iron oxide are supported on aluminum oxide (hereinafter referred to as B catalyst). ) (Hereinafter referred to as A
The hydrogenation reaction of the esterified product with hydrogen is carried out in the presence of a combination of a catalyst and a B catalyst as a combined catalyst). The A catalyst used in the hydrocracking reaction of the present invention is generally commercially available, for example, as a methanol synthesis catalyst, a cyclohexanol dehydrogenation catalyst, a CO low-temperature conversion catalyst, and a gas purification catalyst for removing hydrogen sulfide or CO. Copper-zinc based catalysts can be used. Each of these catalysts contains copper oxide and zinc oxide as main components, but may contain a carrier such as alumina or clay, or a binder.

The A catalyst can be used after pulverized when supplied as a molded article, or can be used as it is when supplied as a powder. In any case, it is preferable that the powder size of the catalyst A is usually under a 200-mesh sieve, and the average particle size is 1 to 50 µm, particularly 2 to 20 µm. A catalyst preferably used is, for example, BAS
Gas purification catalyst R3-12 (pellet molded product, composition: 40% CuO-40% ZnO-Al
₂ O ₃ 20%) and a CO low-temperature conversion catalyst G-66G commercially available from Nissan Gardler (pellet molded product, composition:
CuO 30% -ZnO 60% -viscosity material 10%).

The B catalyst used in the present invention is disclosed in JP-B-45-7287 and JP-B-58-507.
Known catalysts prepared according to the methods disclosed in JP-A-75-175 and JP-A-52-156192, for example, in which copper oxide and iron oxide are supported on aluminum oxide can be used. At this time, it is preferable that the average particle size of the catalyst is usually 5 to 15 μm. The above-mentioned catalyst is particularly suitable for the present invention because it contains copper as an active ingredient and has good filtration separation properties by itself.

When the A catalyst and the B catalyst used in the present invention are mixed, if the ratio of the A catalyst is too large, the activity of the combined catalyst increases, but the filtration and separation properties deteriorate, and conversely, the ratio of the B catalyst decreases. If it is too large, the filterability of the combined catalyst will be good, but the activity will be low. Therefore, the mixing ratio of the A catalyst and the B catalyst is usually A catalyst: B catalyst (weight ratio) = 1: 0.
The ratio is preferably from 5 to 1:10, more preferably from 1: 0.5 to 1: 8, and still more preferably from 1: 1 to 1: 5.

The reason why the combined catalyst is superior in the activity and the filtration separation property as compared with the case where the A catalyst or the B catalyst is used alone is not clear, but can be estimated as follows, for example. In the A-catalyst, since the dispersion of copper oxide is extremely good due to the action of zinc oxide, a part of the copper component is easily dissolved in the reaction solution, and when the dissolved copper component is reduced with hydrogen during the reaction. In addition, the particle size of copper metal as an active ingredient becomes extremely small. As a result, it is considered that the activity of the catalyst is increased, but the filter separation property is deteriorated. On the other hand, it is considered that the activity of the B catalyst is reduced due to the presence of iron oxide and aluminum oxide, but the dispersibility of copper oxide is inferior to that of the A catalyst.

However, when both are used in combination, the copper component of the catalyst A once dissolves during the reaction and deposits on the co-existing copper component of the catalyst B having good filtration and separability, thereby increasing the activity of the combined catalyst. It is considered that the filtration separation property is improved at the same time. This means that when measuring the particle size distribution of the catalyst,
It is inferred from the fact that the particle size of the combined catalyst is larger after use than before use as shown in FIGS. Therefore, it is clear that the combined catalyst acts as a catalyst having novel properties different from those of both the A catalyst and the B catalyst.

[0027] The hydrocracking reaction of the present invention can be carried out in a general liquid phase suspension bed apparatus. That is, the reaction can be carried out by a batch-type reaction in which the esterified material as the raw material and the combined catalyst are charged into a pressure-resistant reactor, and the reaction is carried out by raising the temperature to the reaction temperature while stirring under hydrogen pressure. In addition, a continuous reaction in which a combined catalyst is suspended in advance in an esterified material as a raw material, heated under hydrogen pressure, and then continuously introduced into a lower portion of the reactor to carry out the reaction, can be carried out. In addition,
The amount of the combined catalyst to be used is generally 0.1 to 3.0% by weight, preferably 0.3 to 1.5% by weight, based on the esterified product as the raw material.

After the hydrocracking reaction, the catalyst (combined catalyst) is separated by filtration from the obtained reaction liquid (hydrogenation decomposition liquid). In the present invention, by using the above-mentioned combined catalyst, this filtration can be easily performed using a usual filtration device, for example, a filter type filtration device. And 1,
A diol compound such as 6-hexiondiol can be easily separated by distillation from a reaction solution obtained by filtration, for example, by using a normal vacuum distillation apparatus.
6-hexanediol, 1,5-pentanediol,
1,4-butanediol and the like are obtained as the target product.

[0029]

Next, the method of the present invention will be described in detail with reference to examples. The carboxylic acid mixture used in each of the Examples and Comparative Examples was prepared from a liquid-phase air oxidation reaction solution of cyclohexane described in JP-B-49-27164 by a water extraction method. The extracted carboxylic acid mixture contained 26.8% by weight of adipic acid, 31.9% by weight of oxycaproic acid, 6.1% by weight of glutaric acid, and 1.2% by weight of succinic acid.

The esterified product of the carboxylic acid mixture is prepared by mixing 1000 kg of the carboxylic acid mixture with 850 k of a hydrogenolysis reaction solution containing 50% or more of 1,6-hexanediol.
prepared by esterification with g. The obtained esterified product was composed of 3.1% by weight of 1,6-hexanediol and 1.5% by weight.
-1.1% by weight of pentanediol and 0.06% by weight of 1,4-butanediol, having an acid value (AV) of 0.8 mg-KOH / g and a saponification value (S
V) was 343 mg-KOH / g. This hydrocracking reaction solution was prepared by the method described in Example 1 of JP-A-3-115237.
61.1% by weight of 1,6-hexanediol and 1,5-hexanediol
It contained 8.5% by weight of pentanediol and 0.8% by weight of 1,4-butanediol.

Example 1 As a catalyst A, a gas purification catalyst R3-12 (pellet molded product, composition: 40% CuO, commercially available from BASF)
_{-ZnO40% -Al 2 O 3 20%} ) was pulverized to 200
Fine powder that has passed through a mesh sieve (average particle size of 8.3 before reaction)
μm) was prepared. Further, as a B catalyst,
No. 50775, prepared by the method described in Example 1 of CuO 30% -Fe ₂ O ₃ 30% -Al ₂ O ₃ 4
0% powder catalyst (average particle size 9.7μ before reaction)
m) was prepared. A catalyst mixed with 350 g of the esterified product of the above carboxylic acid mixture in the ratio shown in Table 1 and B
3.5 g of the combined catalyst comprising the catalyst was charged into a stainless steel autoclave having a capacity of 500 ml, and hydrogen gas was injected into the autoclave.
The hydrogenolysis reaction was performed at 80 kg / cm ² for 5 hours.

After completion of the reaction, the mixture was placed in a 500-ml 90-φ pressure filter equipped with a 10-μm membrane filter.
350 ml of the hydrocracking reaction solution kept at 55 ° C. was added, and filtration was performed while applying a pressure of 1.0 kg / cm ² with nitrogen gas. The filtration time was determined by measuring, with a stopwatch, the time required to filter the next 50 ml after the first 50 ml of the reaction solution had passed.

The diol compound such as 1,6-hexanediol produced by the hydrogenolysis reaction was identified by analyzing the reaction solution (filtrate) obtained by the filtration by gas chromatography. The saponification value (SV: mg-KOH / g) of the esterified product of the carboxylic acid mixture used as the raw material and the reaction solution (filtrate) was determined by titration, and the SV reaction rate was calculated by the following equation.

[0034]

(Equation 1)

The particle size of the combined catalyst is determined by washing the combined catalyst separated by the above-mentioned filtration operation with a small amount of methanol, drying the dispersion, dispersing it in ethanol, and using a centrifugal sedimentation type particle size distribution analyzer (SA-CA3: (Manufactured by Shimadzu Corporation). Table 1 shows the obtained analysis results.

Comparative Examples 1 and 2 In each of Comparative Examples 1 and 2, the same reaction and the same procedures as in Example 1 were carried out except that the combined catalyst used in Example 1 was changed to A catalyst and B catalyst respectively. Analysis was carried out. Table 1 shows the analysis results.

Examples 2 to 6 In each of Examples 2 to 6, the catalyst A was a CO low-temperature conversion catalyst G-66 commercially available from Nissan Gardler Co.
G (Pellet molded product, composition: CuO30% -ZnO60
% -Viscosity material 10%) and a fine powder (average particle size before reaction 6.7 μm) passed through a 200 mesh sieve was used, and the mixing ratio of A catalyst and B catalyst in the combined catalyst ( The same reaction and analysis as in Example 1 were performed except that the weight ratio was changed as shown in Table 1. Table 1 shows the analysis results.

Comparative Example 3 A reaction and analysis were carried out in the same manner as in Example 2 except that the catalyst used in Example 2 was changed to the catalyst A alone. Table 1 shows the analysis results.

[0039]

[Table 1]

[0040]

According to the present invention, it is possible to surprisingly overcome at the same time the problems of the activity and the filter separation property of the conventional catalyst. That is, according to the method of the present invention, the catalytic activity is excellent, the separation property by filtration is easy, and the carboxylic acid mixture separated from the oxidation reaction solution of cyclohexane in the presence of the specific combined catalyst containing no chromium. A diol compound such as 1,6-hexanediol can be easily obtained by filtering and separating the combined catalyst from a hydrogenolysis reaction solution obtained by hydrogenolyzing an esterified product with hydrogen.

[Brief description of the drawings]

FIG. 1 shows a combined catalyst (A catalyst: B
The particle size distributions before and after the reaction (catalyst = 1: 1) are shown.

FIG. 2 shows the particle size distribution of a catalyst (A catalyst) in Comparative Example 3 before and after the reaction.

FIG. 3 shows the particle size distribution of a catalyst (B catalyst) in Comparative Example 2 before and after the reaction.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI C07B 61/00 300 B01J 23/74 301X (56) References JP-A-1-180842 (JP, A) JP-A-3-186349 (JP, A) JP-A-55-8820 (JP, A) JP-B-49-27164 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 31/20 B01J 23 / 80 C07C 29/149 B01J 23/745 C07B 61/00 300

Claims (2)

(57) [Claims] 1. A carboxylic acid mixture separated from a liquid-phase air oxidation reaction solution of cyclohexane is esterified with an alcohol, and the produced esterified product is hydrogenolyzed with hydrogen to produce a diol compound. And a catalyst containing zinc oxide as a main component and a catalyst in which copper oxide and iron oxide are supported on aluminum oxide, in the presence of a combined catalyst comprising hydrogenolysis of the esterified product with hydrogen. A method for producing a diol compound. 2. The method for producing a diol compound according to claim 1, wherein the combined catalyst is separated by filtration from the hydrocracking reaction solution.