JPH04202149A - Method for producing 1,6-hexanediol - Google Patents

Abstract

PURPOSE:To obtain the title compound for a long period of time and in high reaction ratio by heating a mixed solution containing a hydrogenating catalyst, an esterified substance and a hydrogen gas to a specific temperature by a preheater, feeding to a hydrogenating column (porous plate type) and hydrogenating. CONSTITUTION:Cyclohexane is oxidized into a carboxylic acid compound in a blender 1, esterified with an alcohol to give a liquid mixture, which is mixed with a hydrogenating catalyst at <=100 deg.C. Then the mixed solution is pressurized (2) to >=50kg/cm<2> and a hydrogen gas is fed to the pressurized mixed solution. Further, this solution is heated to >=220 deg.C in a preheater 5, fed to a hydrogenating column 6 of porous plate type to hydrogenate the esterified substance. The hydrogenating reaction is carried out stably for a long period of time, precipitation of reduced metal, adhesion to column wall, clogging of porous plate, etc., in the hydrogenating column 6 are prevented and decomposition reaction caused by reversed blending in the hydrogenating column 6 of the mixed solution is suppressed to give the title compound in high conversion ratio, in high selectivity and in excellent productivity.

Description

[Detailed Description of the Invention] [Industrial Application Field] This 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. of,
The present invention relates to a method for industrially producing 1,6-hexanediol by hydrogenating it at high temperature and pressure in the presence of a copper-based hydrogenation catalyst.

[Description of Prior Art] Conventionally, as a method for producing 1,6-hexanediol, for example, as described in Japanese Patent Publication No. 53-33567, cyclohexane is oxidized to produce adipic acid and oxycaproic acid. produces carboxylic acid compounds such as
The carboxylic acid compound is esterified with alcohols such as methanol, ethanol, butanol, 1.6-hexanediol, etc., and the reaction product is separated and purified to produce an esterified product.Finally, the obtained ester A method is known in which 1°6-hexanediol is produced by hydrogenating a compound with hydrogen in the presence of a hydrogenation catalyst.

In the above-mentioned known method for producing 1.6-hexanediol, the esterified product is heated under high temperature and pressure in a hydrogenation tower,
When hydrogenation is performed in the presence of a copper-based hydrogenation catalyst, etc., the hydrogenation catalyst is reduced with hydrogen, and the reduced copper adheres to the inner wall of the hydrogenation tower, causing the hydrogenation tower to There were problems in that the space between the tubes was considerably clogged, and proper flow of the reaction solution for the hydrogenation reaction was impossible.

Therefore, the inventors previously filed patent application No. 1-251979.
In the application of No. 1, a hydrogenation catalyst is added to and mixed with the esterified product, the mixture is pressurized, and then hydrogen gas is supplied to the pressurized mixture. We proposed a method in which Liquid J is heated from a low temperature to a temperature of 220° C. or higher in a preheater and then supplied to a hydrogenation tower.

According to this method, before the mixed liquid is supplied to the hydrogenation tower and subjected to the hydrogenation reaction, the mixed liquid is heated in a preheater from a low temperature to a temperature of 220° C. or higher. Precipitation of metallic copper occurs in the preheater while being heated to 220°C, which can prevent the precipitation of metallic copper in the hydrogenation tower, and therefore the hydrogenation reaction in the hydrogenation tower can be carried out for a long period of time. However, since a hollow hydrogenation tower is used, back mixing of the liquid mixture occurs within the hydrogenation tower, resulting in a decomposition reaction of the generated 1,6-hexanediol to monoalcohol, etc. Therefore, there were still problems such as low reaction rate of hydrogenation reaction.

[Problems to be solved by the present invention]

The purpose of this invention is to reduce copper-based catalysts and the like with hydrogen to metal copper, etc. in a hydrogenation tower in which the hydrogenation reaction of the esterified product is carried out at high temperature and high pressure. To provide a method that can prevent the hydrogenation reaction of an esterified product from being carried out properly due to adhesion, and can continue the hydrogenation reaction for a long period of time at a high reaction rate. It is to be.

[Means for solving problems]

In this invention, 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.
Add and mix at a temperature of 100°C or less, and heat the mixture at 50°C.
While pressurizing to a pressure of kg/cTf1 or more, hydrogen gas is supplied to the pressurized mixed liquid, and then the pressurized mixed liquid is heated to a temperature of 220°C or more in a preheater, and the above-mentioned 1, characterized in that the heated and pressurized mixed solution is supplied to a perforated plate-type hydrogenation tower to carry out a hydrogenation reaction of the esterified product to produce 1,6-hexanediol; The present invention relates to a method for producing 6-hexanediol.

[Detailed explanation 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 diagram showing an example of the manufacturing flow when implementing the manufacturing method of the present invention.

In the manufacturing method of this invention, as shown in FIG.
For example, first, inside the mixing tank 1 equipped with a stirrer,
A copper-based hydrogenation catalyst or the like is added to a liquid mixture of an esterified product obtained by esterifying a carboxylic acid compound obtained by oxidizing cyclohexane with molecular oxygen at high temperature and pressure with an alcohol. The mixture is added under pressure at a temperature of 100°C or less, preferably 10 to 90°C, and thoroughly mixed using a stirrer or the like.

Examples of the above-mentioned hydrogenation catalyst include hydrogenation catalysts containing iron, nickel, cobalt, copper, and copper-chromite as main components, and are in the form of powder or tablets. There may be some, and the amount used is
carboxylic acid compounds.

It is sufficient to use several percent by weight based on the liquid mixture of the esterified product obtained by esterification.

The liquid mixture of the above-mentioned esterified products is, for example,
As described in Japanese Patent No. 3-33567, cyclohexane is heated in the presence of an oxidation catalyst to about 100 to 20
By oxidizing with molecular oxygen at a temperature of 0°C and a pressure of about 2 to 20 kg/ciG, various carboxylic acids (such as cabroic acid, valeric acid, butyric acid, etc. Carboxylic acid compounds (including monovalent carboxylic acids, divalent carboxylic acids such as adipic acid, glutaric acid, and succinic acid, and oxyacids such as oxyvaleric acid and oxycaproic acid)
The carboxylic acid compound (mixture) is obtained by separating it from the oxidation reaction solution by an appropriate means, and then the carboxylic acid compound (mixture) is mixed with methanol, ethanol, n-propanol, n-butanol, amyl alcohol, n-hexanol. , monohydric lower alcohols having 1 to 8 carbon atoms such as n-heptatool, ethylene glycol, propylene glycol, 1.4
-butanediol, 1,5-bentanediol, 1,6
- In the presence of an excess of an esterifying agent consisting of an alcohol such as a dihydric alcohol having 2 to 8 carbon atoms such as hexanediol, without a catalyst at a high temperature of about 150 to 300°C and under normal pressure or pressure. esterification, or esterification in the presence of an esterification catalyst at a temperature of 50 to 150°C and under normal pressure or pressure, and finally, the product of the esterification reaction is separated and purified by appropriate means. Any liquid mixture of esterified products containing 1,6-hexanediol diester, oxycaproic acid ester, etc. obtained as a main component may be used.

In this invention, the liquid mixture of the esterified product is
It contains about 10 to 80% by weight, especially about 50 to 70% by weight, of adipate ester and oxycaproic acid ester, and has an acid value (AV) of about 1,0 to 50.mgKOH/
g, especially 1.0 to 20 mgKO1l/g, and if necessary, the esterified product may be dissolved in a suitable organic solvent (especially,
It may be a solution dissolved in an organic solvent used for extracting a carboxylic acid compound (described later).

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 alkaline aqueous solution such as caustic soda, the aqueous layer is separated, and various carboxylic acid salts are separated. Obtain an alkaline solution containing sulfate, neutralize the alkaline solution with sulfuric acid or the like to a pH of 3 or less to produce mirabilite and carboxylic acids, and then obtain an aqueous solution of mirabilite as an aqueous layer separated from the neutralized solution. From the various carboxylic acids mentioned above, methyl ethyl ketone,
Carboxylic acid compounds ( mixture) can be obtained.

In this invention, as shown in FIG.
at a pressure of more than 50 kg/c+flG, preferably 10
While pressurizing to a pressure of 0 to 400 kg/c+flG, the pressurized mixed liquid is heated to a pressure of 100 to 400 kg/c+flG using a hydrogen gas compressor 3.
Hydrogen gas pressurized to a pressure of 0 kg/c+ffG and heated to a temperature of about 50 to 150°C by a hydrogen gas heater 4 is supplied, and then the pressurized and heated hydrogen gas-containing mixed liquid is
The heated and pressurized hydrogen gas-containing mixture is heated to a temperature of 220° C. or higher, particularly 250 to 300° C., inside the preheater 5 consisting of the first-stage preheater Ta or Ib and the second-stage preheater ■. The liquid is supplied to a hydrogenation tower 6 (a perforated plate tower in which perforated plates are installed in multiple stages), and the temperature is preferably 240 to 400°C, particularly 250 to 30°C.
0”C temperature and 150-500 kg/cr
The hydrogenation reaction of the esterified product was carried out at a hydrogen partial pressure of ftG, particularly 200 to 350 kg/crlG, and the hydrogenated reaction solution of the esterified product was taken out from the top of the hydrogenation tower 6 and cooled in a cooler 7. After that, gas components such as unreacted hydrogen gas and the hydrogenated reaction liquid are separated in a gas-liquid separator 8, and the pressure of the hydrogenated reaction liquid is further reduced in a pressure reducing valve 9 to 1.6
A hydrogenation reaction solution containing mainly -hexanediol is collected, and this hydrogenation reaction solution is purified to produce 1,6-hexanediol.

In addition, in the manufacturing flow shown in FIG. 1, the preheater 5 is composed of preheaters 1a and rb at the front stage and preheater ■ at the rear stage, and the front preheaters are used by switching between them. The above-mentioned hydrogenation reaction can be operated continuously for a long period of time in order to remove adhering metals such as copper by cleaning any of the pre-heaters that are not used to heat the mixed liquid. It is suitable because it can be done.

In the above-mentioned first-stage preheater, the mixed liquid is heated to about 150%
Preferably heating to a temperature of ~220°C, and
In the latter stage preheater, the mixed liquid is further heated to 220
It is preferable to heat to a temperature of .degree. C. or higher, particularly 250 to 300.degree. C. (the temperature of the hydrogenation reaction at the bottom of the hydrogenation column).

In this invention, as mentioned above, "a mixed liquid J containing a hydrogenation catalyst, an esterified product, and hydrogen gas" is added to the hydrogenation tower.
Since the mixed liquid is heated from a low temperature to a temperature of 220° C. or higher in the aforementioned preheater before being supplied and subjected to a hydrogenation reaction, the precipitation of reduced metallic copper is
This occurs in the preheater during heating to ℃, and virtually no precipitation of metallic copper, adhesion to the tower wall, or blockage of perforated plates occurs in the hydrogenation tower. The addition reaction can be carried out for a long period of time.

Furthermore, in this invention, by using the hydrogenation tower as a "perforated plate tower in which perforated plates are installed in multiple stages", it is possible to eliminate the "produced 1, 6 -The decomposition reaction of hexanediol to monoalcohol can be suppressed, and the reaction rate of the hydrogenation reaction in the hydrogenation tower can be greatly improved.

Furthermore, if the hydrogenation reaction temperature in the hydrogenation tower is set too high, the aforementioned "decomposition reaction of the generated 1,6-hexanediol to monoalcohol" will proceed, and the selectivity of 1,6-hexanediol will decrease. Therefore, in the production method of the present invention, for example, the hydrogenation tower is made into a "perforated plate tower with an external jacket", and the temperature inside the hydrogenation tower is controlled by passing a heat medium through this jacket. It is preferable to appropriately control the temperature within the reaction temperature range. Thereby, 1,6-hexanediol can be produced from the mixed liquid at a high conversion rate and high selectivity.

〔Example〕

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

Example 1 A liquid-phase oxidation reaction solution obtained by air oxidation of cyclohexane was saponified with caustic soda, and an alkaline solution obtained was neutralized with sulfuric acid. .25, and the neutralized solution is separated into an aqueous layer and an oil layer, and then the carboxylic acid compounds such as adipic acid and oxycaproic acid contained in the aqueous solution of sodium sulfate in the aqueous layer are extracted with methyl isobutyl Extraction was performed with ketone (MIBK), and MIBK was removed from the extract by evaporation to obtain a mixture of carboxylic acid compounds.

An aqueous solution of the mixture of carboxylic acid compounds (concentration 63.5
% by weight) to the esterification step at a feed rate of 740 E/h, and an aqueous solution of 1,6-hexanediol (concentration 61.1% by weight) at 740 E/h. The carboxylic acid compound and 1.6-
Hexanediol is subjected to an esterification reaction at a temperature of 200 to 260°C under normal pressure, and the esterification reaction rate is approximately 99%.
．． 7%, the content of a-form pinic acid ester is 34.7% by weight, and the content of oxycaproic acid ester is 40% by weight.
゜5% by weight, and furthermore, the acid value is 3.1 mgKOH
/ g of esterified product was obtained.

In the production flow shown in FIG. 1, according to the production flow in which the front-stage preheaters 1a and Ib are not operated, a copper-chromite catalyst is added to the liquid mixture of the esterified product obtained as described above in the mixing tank 1. and mix it, and pump the mixed liquid with plunger pump 2 at 300kg/c.
Pressurized to +fl G pressure and heated to about 80°C to 12501. At the same time, the pressurized mixed liquid is supplied with a hydrogen gas compressor 3 at a rate of 300 kg/hour.
Hydrogen gas pressurized to a pressure of c+flG and heated to a temperature of 80°C by a hydrogen gas heater 4 is supplied, and then the pressurized and heated hydrogen gas-containing mixed liquid is
It is heated to a temperature of 270°C using only the second-stage preheater ■, and the heated and pressurized hydrogen gas-containing mixture is transferred to hydrogenation tower 6 (column inner diameter: 530 mm, height: 9860 mm).
) to carry out the hydrogenation reaction of the esterified product in the mixture at a hydrogen partial pressure of 300 kg/cIIIG, and then take out the hydrogenated reaction solution of the esterified product from the top of the hydrogenation column 6. After being cooled to 70°C in a cooler 7, the hydrogenated reaction liquid is separated from gaseous components such as unreacted hydrogen gas in a gas-liquid separator 8, and further, the hydrogenated reaction liquid is constantly cooled in a pressure reducing valve 9. Reduce the pressure to
(2) Collect the hydrogenation reaction solution mainly containing 6-hexanediol, and finally purify the hydrogenation reaction solution by removing low-boiling substances and high-boiling substances by distillation purification. was produced for three months at a rate of 299 kg/hour.

The hydrogenation tower 6 is a hydrogenation tower in which eight perforated plates each having a large number of holes of 8.5 mm in diameter and an aperture ratio of 10% are installed inside the tower to divide the inside of the tower into nine parts. 6 was used.

The hydrogenation reaction solution containing 1,6-hexanediol obtained as described above had an EV value of 19.7 mgKOH/g after continuous operation for three months, and
The concentration of 1,6-hexanediol was 63.2% by weight (freezing point: 41.20°C), and the conversion rate was 94.8%. Furthermore, the temperature of the hydrogenation tower 6 was 285°C at the top and 270°C at the bottom.

According to the manufacturing flow shown in FIG. 1, as described above,
After producing 1,6-hexanediol continuously for three months, we stopped the hydrogenation reaction, disassembled the preheater, hydrogenation tower, etc., and examined the inner walls of each device. No precipitation of metallic copper etc. was observed in the preheater 5.
In the preheater ■, the mixed liquid is heated to 80 to 200℃.
However, only a considerable amount of metallic copper derived from copper-chromite was attached to the areas that were heated.

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

After three months of continuous operation, the hydrogenation reaction solution containing 1,6-hexanediol thus obtained was
EV value is 24.3 mgKOH/g and 1.6
- Concentration of hexanediol is 61.8% by weight (freezing point 4
0.99°C), and the conversion rate was 93°6%.

As in Example 1, after the hydrogenation reaction had stopped, each device was disassembled and the inner walls of each device were examined. As a result, no precipitation of metallic copper or the like was observed in the hydrogenation tower. In (2), only a considerable amount of metallic copper derived from copper-chromite adhered to the portion where the mixed liquid was heated to 80 to 200°C.

Example 3 The outside of the hydrogenation tower 6 is a jacket, and the temperatures at the bottom and top of the hydrogenation tower 6 are controlled at 275°C by passing a heat medium through this jacket. In the same manner as in Example 1, ■,6=hexanediol was produced at a ratio of 3:28 kg/hour for 3 months.

The hydrogenation reaction solution containing 1,6-hexanediol obtained as described above has an EV value of 21.5 mgKOH/
g, and the concentration of 1,6-hexanediol is 64
．． 0% by weight (freezing point: 41.22°C), and the conversion rate was 94.3%.

As in Example 1, after the hydrogenation reaction had stopped, each device was disassembled and the inner walls of each device were examined. As a result, no metal copper or the like was deposited in the hydrogenation tower. In (2), only a considerable amount of metallic copper derived from copper-chromite adhered to the portion where the mixed liquid was heated to 80 to 200°C.

Example 4 Inside the hydrogenation tower 6, 6. The hydrogenation tower 6 is divided into 11 parts by using 10 perforated plates each having a large number of pore diameters of Onrm and an aperture ratio of 10%, and the hydrogenation tower 6 is divided into 11 parts. 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 speed was 1350 j2/hour.

The hydrogenation reaction solution containing 1,6-hexanediol obtained as described above has an EV value of 28.3 mgKOH/
g, and the concentration of 1,6-hexanediol is 62
．． 5% by weight (freezing point: 41.10°C), and the conversion rate was 92.6%.

As in Example 1, after the hydrogenation reaction had stopped, each device was disassembled and their inner walls were examined. As a result, no metal copper was deposited in the hydrogenation tower, and no metal copper was mixed in the preheater ■ of the preheater 5. Only a considerable amount of metallic copper adhered to the portions where the liquid was heated to 80 to 200°C.

Comparative Example 1 Hydrogenation tower 6 was a hollow hydrogenation tower (column inner diameter: 53Qmm
, height: 9860 mm) in the same manner as in Example 1, 1,6-hexanediol was added to 289 mm.
It was produced for three months at a rate of kg/hour. In addition, when a hollow hydrogenation tower was used, it was found that this production amount was the limit of its capacity.

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

[Actions and effects of the present invention]

In this invention, as mentioned above, "before the mixed liquid J containing the hydrogenation catalyst, esterified product, and hydrogen gas is supplied to the hydrogenation tower and subjected to the hydrogenation reaction, the mixed liquid J is heated in a preheater at a low temperature. Since the mixture is heated to a temperature of 220°C or higher, it is supplied to the hydrogenation tower, so the catalyst is reduced by hydrogen gas and metals such as copper are precipitated.The mixed liquid is heated to 220°C in the preheater. However, precipitation of reduced metals, adhesion to the tower walls, and blockage of perforated plates do not occur in the hydrogenation tower. Therefore, the hydrogenation reaction in the hydrogenation tower can be carried out for a long period of time. It can be done stably, and
By using the hydrogenation tower as a perforated plate tower j in which multiple perforated plates are installed inside the hydrogenation tower, it is possible to convert the generated 1°6-hexanediol into monoalcohol due to the back mixing of the liquid mixture in the hydrogenation tower. decomposition reaction j can be suppressed, and a high conversion rate and high selectivity in the hydrogenation reaction can be achieved.
- The productivity of hexanediol is improved.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing an example of the manufacturing flow when implementing the manufacturing method of the present invention. 1: Mixing tank, 2 Nib run gear pump, 3: Hydrogen gas compressor, 4: Hydrogen gas heater, 5: Preheater (Ia and ■b: Front stage preheater, ■: Rear i preheater)
, 6: Hydrogenation tower, 7: Cooler, 8: Gas-liquid separator, 9::
$i pressure tank. Patent applicant: Ube Industries, Ltd.

Claims (1)

[Claims] 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 at a temperature of 100°C or less. , are added and mixed, and the mixed liquid is 50kg/cm^
While pressurizing to a pressure of 2 or more, hydrogen gas is supplied to the pressurized mixed liquid, and then the pressurized mixed liquid is heated to a temperature of 220 ° C. or more in a preheater, and the heating described above is performed.・1,6-hexanediol is produced by supplying the pressurized mixed liquid to a perforated plate-type hydrogenation tower to carry out a hydrogenation reaction of the esterified product. A method for producing hexanediol.