JPH082809B2 - Method for producing 1,6-hexanediol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an esterified product obtained by esterifying a carboxylic acid compound (adipic acid, oxycaproic acid, etc.) obtained by oxidizing cyclohexane with an alcohol. Is hydrogenated at high temperature and high pressure in the presence of a copper-based hydrogenation catalyst or the like to industrially produce 1,6-hexanediol.

[Description of Prior Art]

Conventionally, as a method of producing 1,6-hexanediol, for example, as described in JP-B-53-33567, cyclohexane is oxidized to give a carboxylic acid compound such as adipic acid or oxycaproic acid. The produced carboxylic acid compound is esterified with alcohols such as methanol, ethanol, butanol, and 1,6-hexanediol, and the reaction product is separated and purified to produce an esterified product. A method is known in which the obtained esterified product is hydrogenated with hydrogen in the presence of a hydrogenation catalyst to produce 1,6-hexanediol.

In the known method for producing 1,6-hexanediol, the esterified product is subjected to high temperature and high pressure in a hydrogenation tower,
When hydrogenated in the presence of a copper-based hydrogenation catalyst, etc., the hydrogenation catalyst is reduced by hydrogen, the reduced copper adheres to the inner wall of the hydrogenation tower, and the hydrogenation tower is relatively short-term. There are problems that the space is considerably clogged and that the proper distribution of the reaction liquid for the hydrogenation reaction becomes impossible.

Therefore, in the application of Japanese Patent Application No. 1-251979, the present inventors previously added and mixed a hydrogenation catalyst to the esterified product and pressurized it, and then supplied hydrogen gas to the pressurized mixed liquid. A method was proposed in which the obtained "mixed solution containing a hydrogenation catalyst, an esterified product and hydrogen gas" was heated from a low temperature to a temperature of 220 ° C or higher in a preheater and then fed to a hydrogenation tower.

According to this method, since the mixed solution is heated from a low temperature to a temperature of 220 ° C. or higher and supplied in the pre-heater before the mixed solution is supplied to the hydrogenation tower to carry out the hydrogenation reaction, it is reduced. Precipitation of metallic copper occurs in the pre-heater while being heated to 220 ° C., and it is possible to prevent the precipitation of metallic copper in the hydrogenation tower, so that the hydrogenation reaction in the hydrogenation tower is performed for a long time. However, since a hollow hydrogenation tower is used, back mixing of the mixed solution occurs in the hydrogenation tower, and the decomposition reaction of the produced 1,6-hexanediol into a monoalcohol, etc. Therefore, there were still problems such as a low reaction rate of the hydrogenation reaction.

[Problems to be Solved by the Present Invention]

The object of the present invention is, in a hydrogenation tower for carrying out the hydrogenation reaction of the esterified product under high temperature and high pressure, a copper-based catalyst or the like is reduced with hydrogen to metallic copper or the like, and the metal is on the inner wall of the hydrogenation tower. Provided is a method capable of preventing the hydrogenation reaction of an esterified product from becoming unfavorable by adhering, and further allowing the hydrogenation reaction to be continued with a high reaction rate for a long period of time. It is to be.

[Means for solving problems]

This invention, in a mixing tank, to a liquid mixture of an esterified product obtained by esterifying a carboxylic acid compound obtained by oxidizing cyclohexane with alcohols, a hydrogenation catalyst is added at a temperature of 100 ° C. or lower. Mix and mix 50k
While pressurizing to a pressure of g / cm ² or more, hydrogen gas is supplied to the pressurized mixed liquid, and then the pressurized mixed liquid is
Heat to a temperature above 220 ° C in the preheater, and
The heated and pressurized mixed liquid is supplied to a porous plate type hydrogenation tower to cause a hydrogenation reaction of the esterified product,
1,6-, characterized by producing 6-hexanediol
It relates to a method for producing hexanediol.

[Detailed description of each requirement of the present invention]

Hereinafter, the method for producing 1,6-hexanediol of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a flow chart showing an example of a manufacturing flow when the manufacturing method of the present invention is carried out.

In the manufacturing method of the present invention, as shown in FIG. 1, for example, first, in a mixing tank 1 provided with a stirrer, cyclohexane was obtained by oxidizing cyclohexane with molecular oxygen under high temperature and pressure. A liquid mixture of the esterified product obtained by esterifying the carboxylic acid compound with alcohols, a copper-based hydrogenation catalyst, etc., under normal pressure or pressure, a temperature of 100 ℃ or less,
Preferably, the mixture is added at a temperature of 10 to 90 ° C. and thoroughly mixed with a stirrer or the like.

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.

The liquid mixture of the above-mentioned esterified product is, for example,
As described in JP-A-53-33567, cyclohexane was added in the presence of an oxidation catalyst at about 100 to 200 ° C.
Cyclohexanone, by oxidation with molecular oxygen or the like at a temperature of about ^{2 to 20} kg / cm ² G
Various carboxylic acids by-produced together with cyclohexanol (monocarboxylic acids such as caproic acid, valeric acid, butyric acid, divalent carboxylic acids such as adipic acid, glutaric acid, succinic acid, oxyvaleric acid, oxycaproic acid) Compounds (mixtures) containing oxyacids such as
Of the carboxylic acid compound (mixture) is separated from the above-mentioned oxidation reaction solution by a suitable means, and then the carboxylic acid compound (mixture) thereof is mixed with methanol, ethanol, n-propanol, n-butanol, amyl alcohol, n-hexanol, n- C1-C8 monovalent lower alcohols such as heptanol, ethylene glycol, propylene glycol, 1,4
-In the presence of an esterifying agent consisting of alcohols such as dihydric alcohols having 2 to 8 carbon atoms such as butanediol, 1,5-pentanediol, and 1,6-hexanediol, in the presence of no catalyst, 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, Any liquid mixture of esterification products containing 1,6-hexanediol ester, oxycaproic acid ester or the like as a main component, obtained by separating and purifying the product of the esterification reaction by an appropriate means may be used.

In the present invention, the liquid mixture of the esterified product contains adipic acid ester and oxycaproic acid ester in an amount of about 10 to 80% by weight, particularly about 50 to 70% by weight, and has an acid value (AV value) of about 1.0. ~ 5.0 mgKOH / g, especially 1.0 ~
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 (particularly the organic solvent used for extracting the carboxylic acid compound described below). Etc.).

As a method for separating the carboxylic acids from the cyclohexane oxidation reaction solution, for example, the cyclohexane oxidation reaction solution is saponified with an aqueous alkaline 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 above various carboxylic acids, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, ethyl acetate, butyl acetate, esters such as methyl caproate, organic solvents such as lower alcohols such as butyl alcohol, isopropyl alcohol, etc. It is possible to obtain a carboxylic acid compound (mixture) by extraction with (extraction solvent). That.

In the present invention, as shown in FIG. 1, the “mixed liquid containing the esterification product and the hydrogenation catalyst” prepared in the mixing tank 1 as described above is supplied to the plunger pump 2
In 50 kg / cm ² G or more pressure, preferably with pressurized to a pressure of 100~400kg / cm ² G, in the pressurized mixture, to a pressure of 100~400kg / cm ² G with hydrogen gas compressor 3 Hydrogen gas that has been pressurized and heated to a temperature of about 50 to 150 ° C. by the hydrogen gas heater 4 is supplied, and then the pressurized and heated hydrogen gas-containing mixed liquid is supplied to the pre-heater Ia or Ib and the post-heater. Preheater
Inside the preheater 5 consisting of II, a temperature of 220 ° C or higher,
In particular, it is heated to a temperature of 250 to 300 ° C., and the heated and pressurized hydrogen gas-containing mixed liquid is supplied to a hydrogenation tower 6 (a perforated plate tower in which perforated plates are provided in multiple stages), Preferably, the hydrogenation reaction of the esterified product is carried out at a temperature of 240 to 400 ° C., particularly 250 to 300 ° C., and a hydrogen partial pressure of 150 to 500 kg / cm ² G, particularly 200 to 350 kg / cm ² G, The esterification product hydrogenation reaction liquid is taken out from the top of the hydrogenation tower 6 and cooled in a cooler 7, and then a gas-liquid separator 8 separates unreacted gas components such as hydrogen gas from the hydrogenation reaction liquid. Then, the hydrogenation reaction solution was decompressed by the decompression valve 9,
-The hydrogenation reaction liquid mainly containing hexanediol is recovered, and the hydrogenation reaction liquid is purified to produce 1,6-hexanediol.

In the manufacturing flow shown in FIG. 1, the pre-heater 5 is composed of pre-heaters Ia and Ib in the front stage and pre-heater II in the rear stage. Since any metal such as copper that has adhered can be removed by washing, etc., any one of the pre-stage heaters that are not used for heating the mixed solution, the hydrogenation reaction described above is continuously operated for a long period of time. Therefore, it is preferable.

In the above pre-heater, the mixed solution was mixed with about 150 to 2
It is preferable to heat to a temperature of 20 ° C., and in the latter-stage preheater, the mixed liquid is further heated to a temperature of 220 ° C. or higher, particularly a temperature of 250 to 300 ° C. (hydrogenation reaction of the bottom of the hydrogenation tower). It is preferable to heat to the above temperature).

In the present invention, as described above, before the hydrogenation reaction is performed by supplying the "mixed liquid containing the hydrogenation catalyst, the esterification product and the hydrogen gas" to the hydrogenation tower, the above-mentioned mixing is performed in the preheater. Since the liquid is heated from a low temperature to a temperature of 220 ° C or higher and supplied, the precipitation of reduced metallic copper is 220
It occurs in the preheater while being heated to ℃, in the hydrogenation tower, precipitation of metallic copper, adhesion to the tower wall, and clogging of the perforated plate do not substantially occur, and the water in the hydrogenation tower The addition reaction can be carried out for a long period of time.

Further, in the present invention, the hydrogenation tower is "a perforated plate tower in which a perforated plate is provided in multiple stages", so that "generated 1,6 resulting from back mixing of the mixed liquid in the hydrogenation tower is generated. -Hexanediol decomposition reaction into monoalcohol "can be suppressed, and the reaction rate of the hydrogenation reaction in the hydrogenation tower can be significantly improved.

If the hydrogenation reaction temperature in the hydrogenation tower is set too high, the above-mentioned “decomposition reaction of 1,6-hexanediol formed into monoalcohol” proceeds, and the selectivity of 1,6-hexanediol increases. In the production method of the present invention, for example, the hydrogenation tower is set to “a perforated plate column with an outer jacket”, and a heating medium is passed through the jacket to control the temperature in the hydrogenation tower as described above. It is preferable to appropriately control the temperature within the temperature range. As a result, 1,6-hexanediol can be produced from the mixed solution with high conversion and high selectivity.

〔Example〕

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

Example 1 An alkaline solution obtained by saponifying a liquid-phase oxidation reaction solution obtained by aerial oxidation of cyclohexane with caustic soda was neutralized with sulfuric acid, and at that time, the specific gravity of the aqueous solution of Glauber's salt in the aqueous layer of the neutralization solution was 1.25. After the water is balanced so that the neutralization solution is separated into an aqueous layer and an oil layer, carboxylic acid compounds such as adipic acid and oxycaproic acid contained in the aqueous sodium sulfate solution of the aqueous layer are treated with methyl isobutyl ketone ( MIBK), and MIBK was removed from the extract by evaporation to give a mixture of carboxylic acid compounds.

An aqueous solution of the mixture of carboxylic acid compounds (concentration 63.5% by weight) was supplied to the esterification step at a supply rate of 740 / hour, and an aqueous solution of 1,6-hexanediol (concentration 61.
1% by weight) at a feed rate of 740 / hour to the esterification step to cause the carboxylic acid compound and 1,6-hexanediol to undergo an esterification reaction at a temperature of 200 to 260 ° C. under normal pressure to give an ester. With a reaction rate of about 99.7%, the content of adipic acid ester is 34.7% by weight, the content of oxycaproic acid ester is 40.5% by weight, and the acid value is 3.
1 mgKOH / G of a liquid mixture of esterified product "was obtained.

In the production flow shown in FIG. 1, according to the production flow in which the pre-heaters Ia and Ib are not operated, the liquid mixture of the esterified product obtained as described above is added to the copper-chromite catalyst in the mixing tank 1. Was added and mixed, the mixture was pressurized to a pressure of 300 kg / cm ² G with a plunger pump 2, heated to about 80 ° C. and supplied at a supply rate of 1250 / hour, and The pressurized liquid mixture is supplied with hydrogen gas which is pressurized by the hydrogen gas compressor 3 to a pressure of 300 kg / cm ² G and heated by the hydrogen gas heater 4 to a temperature of 80 ° C. The pressurized / heated hydrogen gas-containing mixed liquid is heated to a temperature of 270 ° C. only by the second-stage preheater II, and the heated / pressurized hydrogen gas-containing mixed liquid is heated to a hydrogenation tower 6 (tower). Inner diameter: 530 mm, height: 9860 mm) is continuously supplied to 300 kg / cm ² G The hydrogenation reaction of the esterified product in the mixed liquid is carried out under the hydrogen partial pressure of 1, the hydrogenation reaction liquid of the esterified product is taken out from the top of the hydrogenation tower 6, cooled to 70 ° C. by the cooler 7, and then vaporized. A gas-liquid component such as unreacted hydrogen gas is separated from the hydrogenation reaction liquid in a separator 8, and the hydrogenation reaction liquid is depressurized to a normal pressure by a pressure reducing valve 9 to obtain 1,6-hexanediol. The hydrogenation reaction solution mainly containing the above is recovered, and finally, the low-boiling matter and the high-boiling matter are removed from the hydrogenation reaction solution by distillation purification to be purified, and 1,6-hexanediol is added at a rate of 299 kg / hour. Manufactured for 3 months.

In addition, as the hydrogenation tower 6, a porous plate 8 having a large number of pores of 8.5 mm and having an aperture ratio of 10% was provided inside the hydrogenation tower 6.
After searching for one sheet, a hydrogenation tower 6 in which the inside of the tower was divided into 9 was used.

The hydrogenation reaction liquid containing 1,6-hexanediol obtained as described above had an EV value of 19.7 mgKOH / g after 1,3-hexanediol, Was 63.2% by weight (freezing point 41.20 ° C), and its conversion rate was 94.8%. The temperature of the hydrogenation tower 6 is
The top was 285 ° C and the bottom was 270 ° C.

According to the production flow shown in FIG. 1, 1,6-hexanediol was continuously produced for 3 months as described above, then the hydrogenation reaction was stopped, and the preheater, hydrogenation tower, etc. were decomposed. Then, as a result of examining the inner wall of each device, no precipitation of metallic copper or the like was observed in the hydrogenation tower, while in the preheater II of the preheater 5, the mixed liquid was heated to 80 to 200 ° C. However, only a considerable amount of metallic copper derived from copper-chromite was attached to the spots.

Example 2 After producing 1,6-hexanediol for 2 months in the same manner as in Example 1, the supply amount of the heated and pressurized hydrogen gas-containing mixed liquid to the hydrogenation tower 6 was increased to 6-Hexanediol was produced at a rate of 317 kg / hour, and the bottom temperature of the hydrogenation tower 6 after the supply of the heated and pressurized hydrogen gas-containing mixed solution was increased was 255 ° C., and the tower top 1,6-Hexanediol was produced in the same manner as in Example 1 except that the temperature was 290 ° C.

The hydrogenation reaction liquid containing 1,6-hexanediol obtained in this manner was used after three months of continuous operation.
The EV value was 24.3 mgKOH / g, the concentration of 1,6-hexanediol was 61.8 wt% (freezing point 40.99 ° C), and the conversion rate was 93.6%.

After stopping the hydrogenation reaction in the same manner as in Example 1, each device was disassembled and the inner wall of each device was examined. As a result, no precipitation of metallic copper or the like was observed in the hydrogenation tower, while the preheater of the preheater 5 was used. In II, the place where the mixed solution was heated to 80 to 200 ° C. was only a considerable amount of metallic copper derived from copper-chromite attached.

Example 3 A jacket was formed on the outside of the hydrogenation tower 6, and the temperature at the bottom and the top of the hydrogenation tower 6 was controlled to 275 ° C. by passing a heat medium through this jacket. In the same manner as in Example 1, 1,6-hexanediol was produced at a rate of 328 kg / hour for 3 months.

The hydrogenation reaction liquid containing 1,6-hexanediol obtained as described above had an EV value of 21.5 mgKOH / g,
Concentration of 1,6-hexanediol is 64.0% by weight (freezing point 41.
22 ° C) and the conversion rate was 94.3%.

After stopping the hydrogenation reaction in the same manner as in Example 1, each device was disassembled and the inner wall of each device was examined. As a result, no precipitation of metallic copper or the like was observed in the hydrogenation tower, while the preheater of the preheater 5 was used. In II, the place where the mixed solution was heated to 80 to 200 ° C. was only a considerable amount of metallic copper derived from copper-chromite attached.

Example 4 A hydrogenation tower in which the hydrogenation tower 6 was divided into 11 parts by searching for 10 perforated plates each having a large hole diameter of 6.0 mm and an opening ratio of 10% into the hydrogenation tower 6. 6 was used, and 1,6-hexanediol was produced at a rate of 338 kg / hour for 3 months in the same manner as in Example 1 except that the feed rate of the mixed solution of the esterified product was 1350 / hour. .

The hydrogenation reaction liquid containing 1,6-hexanediol obtained as described above had an EV value of 28.3 mgKOH / g,
The concentration of 1,6-hexanediol is 62.5% by weight (freezing point 41.
10 ° C), and the conversion rate was 92.6%.

After the hydrogenation reaction was stopped in the same manner as in Example 1, the respective devices were disassembled and their inner walls were examined. As a result, no precipitation of metallic copper or the like was observed in the hydrogenation tower, and mixing was performed in the preheater II of the preheater 5. Only a large amount of metallic copper adhered to the place where the liquid was heated to 80 to 200 ° C.

Comparative Example 1 289 kg of 1,6-hexanediol was prepared in the same manner as in Example 1 except that a hollow hydrogenation tower (inner diameter: 530 mm, height: 9860 mm) was used as the hydrogenation tower 6. 3 per hour
Made for a month. In addition, when a hollow hydrogenation tower was used, it was found that this production amount was the limit of capacity.

The hydrogenation reaction liquid containing 1,6-hexanediol obtained as described above had an EV value of 35 mgKOH / g after continuous operation for 3 months and had 1,6-hexanediol content of 1,6-hexanediol. The concentration was 61.1% by weight (freezing point 40.97 ° C), and the conversion rate was 90.8%.

[Operation and effect of the present invention]

In the present invention, as described above, in the preheater, before supplying the "mixed liquid containing the hydrogenation catalyst, the esterified product and the hydrogen gas" to the hydrogenation tower,
After heating the mixed solution from a low temperature to a temperature of 220 ° C. or higher, since it is supplied to the hydrogenation tower, the catalyst is reduced by hydrogen gas to deposit a metal such as copper, because the mixed solution is 220 It occurs during heating up to ℃, precipitation of reduced metal in the hydrogenation tower, adhesion to the tower wall, clogging of the perforated plate, etc. do not substantially occur, therefore the hydrogenation reaction in the hydrogenation tower Can be stably performed for a long period of time,
By setting the hydrogenation tower to be a "perforated plate tower in which multiple perforated plates are provided in multiple stages", "the produced 1,6-hexanediol is converted into a monoalcohol resulting from the back mixing of the mixed solution in the hydrogenation tower. Since the "decomposition reaction" can be suppressed and a high conversion and a high selectivity in the hydrogenation reaction can be achieved, the productivity of 1,6-hexanediol is improved.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a manufacturing flow when the manufacturing method of the present invention is carried out. 1: Mixing tank, 2: Plunger pump, 3: Hydrogen gas compressor,
4: Hydrogen gas heater, 5: Preheater (Ia and Ib: Front stage preheater, II: Rear stage preheater), 6: Hydrogenation tower, 7:
Cooler, 8: gas-liquid separator, 9: vacuum tank.

Claims (1)

[Claims] 1. A hydrogenation catalyst is added to a liquid mixture of an esterified product obtained by esterifying a carboxylic acid compound obtained by oxidizing cyclohexane with an alcohol in a mixing tank.
The mixture is added and mixed at a temperature of 100 ° C. or lower, the mixture is pressurized to a pressure of 50 kg / cm ² or more, and hydrogen gas is supplied to the pressurized mixture, and then the pressurized mixture is 22 in the preheater
The mixture is heated to a temperature of 0 ° C. or higher, and the heated and pressurized mixed liquid is supplied to a perforated plate type hydrogenation tower to cause the esterification product to undergo a hydrogenation reaction. A method for producing 1,6-hexanediol, which comprises producing hexanediol.