JP2001181223A - Method for producing 1, 4-cyclohexanedimethanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing 1, 4-cyclohexanedimethanol by a two stage hydrogenation of terephthalic acid, capable of being carried out with a little amount of hydrogen and under a mild pressure by passing through an oligomerization process in the second stage hydrogenation which usually required a large amount of hydrogen or a high pressure. SOLUTION: This method for producing 1, 4-cyclohexanedimethanol consists of a first process for producing 1,4-cyclohexanedicarboxylic acid by reducing terephthalic acid with hydrogen, a second process for mixing the 1, 4- cyclohexanedicarboxylic acid obtained in the aforesaid first process with 1, 4-cyclohexanedimethanol and carrying out an esterification reaction by, if needed, heating the mixture and a third process for producing 1, 4- cyclohexanedimethanol by hydrogenating the aforesaid mixture or the generated product through the esterification reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a two-stage hydrogenation of terephthalic acid, whereby 1,4-cyclohexanedimethanol (C
HDM).

[0002]

2. Description of the Related Art CHDM is useful as a raw material for polyester-based synthetic fibers and synthetic resins, and is particularly used as a raw material for resins having excellent heat resistance, weather resistance, physical strength and the like.

As a method for producing CHDM, a method of hydrogenating dialkyl terephthalate by a two-stage reaction using a fixed-bed reactor is generally used, and several methods have been proposed. For example, US Pat.
No. 49 discloses the use of dialkyl terephthalate as a raw material, hydrogenation of a benzene ring with a catalyst supported on palladium / alumina, and hydrogenation of the ester portion of the first-stage reaction solution using a copper chromite catalyst to obtain CHD.
A method for generating M has been proposed.

Further, a method has been proposed in which terephthalic acid is hydrogenated in a two-stage reaction using a solution reactor. For example, Japanese Patent Application Laid-Open No. 52-242 discloses that a benzene ring is hydrogenated with a rhodium / carbon carrier catalyst using methanol as a solvent as a terephthalic acid raw material, and then the acid portion of the first-stage reaction solution is purified using a copper chromite catalyst. In the method of producing CHDM by hydrogenolysis, and in the second stage of hydrogenation using 1,4-cyclohexanedicarboxylic acid produced in the first stage as a raw material, dimethoxyethane (JP-A-9-132541) and dioxane ( A method using JP-A-9-59188) has been proposed.

However, each of these methods has some problems in industrialization. For example, in the method of the above-mentioned U.S. Pat. No. 3,334,149, it was necessary to carry out the reaction under considerably severe conditions of 100 to 350 ° C. and 50 to 500 atm. In addition, it was necessary to use a considerable excess of hydrogen with respect to the theoretical amount, and it was necessary to purify the gas discharged from the reactor and recycle it to the reactor. Japanese Patent Application Laid-Open No. 52-242 discloses that methanol is used as a terephthalic acid raw material, and
Strict conditions of 15 to 150 atmospheres are required. In JP-A-9-132541, dimethoxyethane is used as the second-stage reaction solvent, which also requires 100 atm. Similarly, in JP-A-9-59188, the reaction conditions are mild, but the yield is as low as 41%.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors hydrogenated the benzene ring of terephthalic acid in the first stage using a noble metal-based catalyst with an aqueous solvent to obtain a terephthalic acid. The present inventors have found that the hydrogenation of the obtained 1,4-cyclohexanedicarboxylic acid can be performed under mild conditions using the second-stage product CHDM as a solvent, and that the excess amount of hydrogen can be reduced. Was.

That is, according to the present invention, an esterification reaction is carried out by mixing 1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol and, if desired, heating the mixture to carry out an esterification reaction. A method for producing 1,4-cyclohexanedimethanol, which comprises hydrogenating a product. The method for producing 1,4-cyclohexane dimethanol includes the first step of producing 1,4-cyclohexane dicarboxylic acid by hydrogenating terephthalic acid, and the 1,4-cyclohexane dicarboxylic acid obtained in the first step. , 1,4-cyclohexane dimethanol and, if desired, heating the mixture to carry out an esterification reaction. The mixture or the esterification reaction product is hydrogenated to give 1,4-cyclohexane dimethanol. It preferably comprises a third step of production.
In the present invention, 1,4-cyclohexanedimethanol obtained in the third step can be used as 1,4-cyclohexanedimethanol in the second step. Further, in the present invention, a step of separating 1,4-cyclohexanedicarboxylic acid can be provided between the first step and the second step.

[0008]

[Detailed Description of the Means] The first, second and third steps will be described in the following order. (1) First Step The first step is the so-called first hydrogen in which the benzene ring of terephthalic acid is hydrogenated with a commonly used noble metal catalyst to produce 1,4-cyclohexanedicarboxylic acid (hereinafter sometimes referred to as CHDA). This is the step of the chemical reaction.

The terephthalic acid used as a raw material of the present invention is of sufficient quality to be commercially available for industrial use, and contains undried water that has undergone a hydrorefining step generally performed in a terephthalic acid producing step. Can be used.

The first-stage reaction is an exothermic reaction. In order to appropriately suppress the temperature rise due to the heat of the reaction and to increase the reaction rate, a solvent inert to this reaction is diluted with terephthalic acid as a raw material. It is preferable to dilute so that the concentration of terephthalic acid in the first stage feed solution is 1 to 50% by weight, preferably 2 to 20% by weight. When the concentration of terephthalic acid in the feed solution is in this range, the reaction rate is not reduced, and the temperature rise in the reactor is advantageously small.

Examples of such a solvent include water, methanol, 1,4-dioxane and the like. The reaction product of the first stage can be cooled and recycled if necessary. Is advantageous. In this case, water is preferred because it can be recovered by the subsequent separation operation, furthermore, no harmful components are mixed in the reaction system, and undried terephthalic acid which has undergone a terephthalic acid purification step can be used.

The quality of hydrogen used in the first-stage reaction is sufficient for hydrogen used industrially, and may contain an inert gas such as nitrogen or methane, but the hydrogen concentration is 50%.
It is preferable that there is the above. The amount of hydrogen is preferably about 3 to 50 times the molar ratio of the raw material terephthalic acid. Within this range, the amount of unreacted substances is small, the reaction rate is sufficient, and it is economically advantageous.

The catalyst used in the first-stage reaction is a noble metal-based nuclear hydrogenation catalyst, and specific examples thereof include palladium, platinum, ruthenium, and rhodium.
Among them, palladium and ruthenium are preferable. These are preferably used as supported catalysts, and activated carbon, alumina, silica, diatomaceous earth and the like are used as carriers. In particular, activated carbon and silica can be preferably used. Examples of the palladium-supported catalyst include 10% palladium / carbon manufactured by NE Chemcat. The supported amount of palladium and ruthenium is from 0.1 to 1 of the total amount of the catalyst (including the carrier).
0% by weight, preferably 5 to 10% by weight. A loading of 0.1% by weight or more is preferred because the activity per catalyst weight is high.

As the form of the catalyst, a catalyst supported on a powder, granular or pellet carrier can be used. Preferably, powder is good. When the catalyst has an appropriate size, the inside of the catalyst has many portions that effectively contribute to the reaction, so that the reaction speed is not easily reduced. The amount of the catalyst is preferably 1 to 50% by weight, particularly preferably 5 to 20% by weight, based on terephthalic acid.

Since terephthalic acid has a very low solubility in general-purpose solvents, the reaction method is preferably a liquid phase suspension reaction.
The reactor is preferably a pressure vessel. Feed slurry and hydrogen are introduced from the top or bottom of the reactor and come into contact with the catalyst in suspension. Since 1,4-cyclohexanedicarboxylic acid is dissolved in water at a high temperature, it can be separated from the catalyst by filtration. Thereafter, water as a solvent is dried, or recrystallized by concentrating and lowering the temperature of water to obtain cyclohexanedicarboxylic acid.

The reaction temperature is preferably from 80 ° C. to 200 ° C.
More preferably, it is in the range of 100 ° C to 160 ° C. Within this range, unreacted substances and by-products are small, and hydrogenolysis is unlikely to occur, and as a result, the yield is high. The reaction pressure is preferably 0.5 MPa to 15
MPa, particularly preferably in the range of 2 MPa to 15 MPa. When the reaction pressure is in this range, the reaction rate does not decrease, and the generation of by-products is small. It is also economically advantageous. The conversion of the reactants is usually at least 95%, preferably 9%.
9% or more. When the amount of unreacted terephthalic acid is small as described above, when hydrogenating in the third step described below, the desired CHDM can be produced without lowering the reaction rate.
And it can be obtained with good yield.

(2) Second step In the second step, 1,4-cyclohexanedicarboxylic acid and C
This is a step of mixing with HDM and, if desired, heating the mixture to esterify it. As the 1,4-cyclohexanedicarboxylic acid, a product obtained by crystallizing and drying the first-stage reaction product is preferable. The CHDM may be of a quality that is commercially available for industrial use, or the reaction product obtained in the third step described below may be used as it is or after purification. The mixing ratio of both is CHD in weight ratio.
A: CHDM is 1: 1.5 to 1: 20.0, especially 1: 1.7 to 1:
6.0 is preferred.

In this step, 1,4-cyclohexanedicarboxylic acid and CHDM can be mixed and dissolved, and supplied to the next step as it is. In this case, the mixture is brought to 50 ° C.
It is preferable to dissolve while maintaining the temperature at 250 ° C., particularly 130 ° C.-250 ° C. Further, the mixture is once heated to form an esterification reaction product represented by the following general formula 1 (hereinafter sometimes referred to as an oligomer), and a liquid from which water generated by the reaction is removed is supplied to the next step. May be. Also,
The esterification reaction product may be isolated by crystallization or the like and supplied to the next step. When carrying out the esterification reaction, the reaction temperature is preferably from 50 to 280C, particularly preferably from 200 to 250C.

[0019]

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(3) Third Step Hydrogenation The quality of the hydrogen used in the third step is sufficient for industrially used hydrogen, and may contain an inert gas such as nitrogen or methane. Is preferably 50% or more. The amount of hydrogen is 3 to 50 times the molar ratio of 1,4-cyclohexanedicarboxylic acid (in the case where an oligomer is formed in the second step, also includes 1,4-cyclohexanedicarboxylic acid units in the oligomer). The degree is preferred. Within this range, reduction of unreacted substances, reaction rate,
It is advantageous in terms of economy.

Examples of the catalyst used in the reaction include copper-chromium-manganese, copper-chromium-zinc, ruthenium-tin / alumina and the like, but copper-chromium-manganese catalyst is preferred. Preferably, the composition is in the range of 30 to 60% by weight of copper oxide, 30 to 60% by weight of chromium oxide, and 0.1 to 10% by weight of manganese in an oxidized state. Within this range, the generation of by-products is small,
It is preferable because the yield of 1,4-cyclohexanedimethanol is high. An example of such a copper-chromium-manganese catalyst is N203SD manufactured by JGC Corporation.

The reaction system may be either a liquid phase suspension system reaction or a fixed bed reaction, but a fixed bed is preferred. In this case, the reactor may be a multi-tube type in which heat of reaction is removed through a heat medium, or an adiabatic reactor may be simply used.
The raw material liquid and hydrogen are introduced from the upper or lower part of the reactor, pass through the catalyst layer filling section in a downflow or ascending flow in a gas-liquid co-current state, and are discharged from the opposite end.

The amount charged to the reactor is preferably as large as possible within a range in which the conversion of the unreacted substances in the reaction solution becomes an allowable value or more, according to the reaction rate determined by the reaction conditions. Although it is difficult to express uniquely, it is preferable to set LHSV to 0.01 to 1. The reaction temperature is preferably in the range from 200 to 280C. Within this range, unreacted products and by-products are reduced, and the yield can be kept high, which is preferable. The reaction pressure is in the range of 5 to 30 MPa, more preferably 6 to 20 MPa. This range is preferable from the viewpoints of reaction rate, reduction of by-products, and economy. A higher conversion is economically advantageous.

According to the present invention, in the production of CHDM by two-stage hydrogenation of terephthalic acid, the second-stage hydrogenation reaction, which conventionally required a large amount of hydrogen or a high pressure, is subjected to an oligomerization step. , It can be carried out with a small amount of hydrogen and at a moderate pressure, and its industrial significance is great.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples unless it exceeds the gist of the present invention. Example 1 (First-stage reaction) 0.5 g of terephthalic acid was added to a 50 ml SUS autoclave, and a catalyst (10% manufactured by NE Chemcat) was used.
0.1 g of Pd / C) and 10 g of water were charged, a rotor was put in, and the lid was put. Hydrogen was introduced from the autoclave nozzle port and replaced three times, and the hydrogen pressure was increased to 4 MPa for the fourth time, and the valve was closed. It was immersed in an oil bath maintained at 140 ° C., the stirrer was turned, and the inside was stirred. The reaction was continued for 3 hours. After allowing to cool and depressurizing, the contents were taken out, washed with hot water and filtered (filtered with a filter having a pore size of 1 μm), and the filtrate was subjected to water evaporation with an evaporator to obtain 0.5 g of a white powder. Analysis of terephthalic acid by liquid chromatography of the catalyst part and part of the white powder part,
Further, 1,4-cyclohexanedicarboxylic acid was esterified with methanol and analyzed by gas chromatography as dimethyl 1,4-cyclohexanedicarboxylate. The conversion of terephthalic acid is 99.6 mol%, and the CHDA yield is 9
It was 6.9 mol%.

(Second Stage Reaction) A fixed bed isothermal reactor having a tower diameter of 8 mm and a length of 25 mm was charged with 7 ml of a catalyst (N203SD copper / chromium / manganese catalyst manufactured by JGC Chemicals Co., Ltd.). In this reactor, a mixture of 15 parts by weight of dry powder CHDA obtained in the first-stage reaction and 85 parts by weight of CHDM (manufactured by Tokyo Chemical Industry Co., Ltd., reagent grade 1) was heated to 140 ° C., and 5 ml / hr, hydrogen gas (purity) 1.0 l / hr was introduced from the top of the reactor, and the temperature of the reactor reached 240 ° C. The reactor pressure was kept at 8 MPa. Gas and liquid flowing out from the lower part of the reactor were separated, and the reaction liquid was analyzed. Generated CHD
M and excess CHDM were directly measured by gas chromatography. In addition, esterification treatment was performed with methanol and analyzed by gas chromatography. The 1,4-cyclohexanedicarboxylic acid portion at the center of the oligomer was detected as dimethyl 1,4-cyclohexanedicarboxylate and measured as 1,4-cyclohexanedicarboxylic acid (including unreacted CHDA). The intermediate was detected as 1-hydroxymethyl-4-carboxymethylcyclohexane by esterification with methanol and measured as 1-hydroxymethyl-4-carboxycyclohexane. 0.1N-Na
Unreacted CHDA was measured by titration analysis with OH. C
The HDA conversion is 89.7%, and the CHDM yield is 33.5.
%, The intermediate yield is 19.9%, and the oligomer yield is 36.%.
3%. This effluent was heated again to 140 ° C.
0.4 ml / hr, hydrogen gas (purity: 99.9% or more), 0.5 l / hr, was introduced from the top of the reactor, and the temperature of the reactor was 240 ° C. The reactor pressure was kept at 8 MPa. Gas and liquid flowing out from the lower part of the reactor were separated, and the reaction liquid was analyzed. The reaction solution was analyzed in the same manner as before, or after subjecting to esterification with methanol, by gas chromatography or the like. The CHDA conversion was 99.7 mol%, the oligomer yield was 0.5 mol%, and the intermediate yield was 26.0 mol.
%, And the CHDM yield was 69.6 mol%.

Example 2 (Oligomerization Reaction) CHDA 17.2 g, CHDM
33.0 g was taken and reacted at 230 ° C. for 4 hours while extracting generated water. After cooling, washing and filtration with methanol were repeated three times, followed by drying to isolate an oligomer. Melting point was 85 ° C. A part thereof was dissolved in methanol and the soluble matter was analyzed by gas chromatography. CHDM was not detected. In addition, esterification treatment was performed with methanol and analyzed by gas chromatography. The 1,4-cyclohexanedicarboxylic acid portion at the center of the oligomer was detected as dimethyl 1,4-cyclohexanedicarboxylate, and was 40.7% by weight as 1,4-cyclohexanedicarboxylic acid. Also, 0.1N-Na
Titration analysis was performed with OH. 0.1% by weight as acid (CHDA)
Measured.

(Second stage reaction) 0.6 g of the oligomer obtained in the oligomer step was added to 50 ml of autoclave.
Was charged with 0.1 g of a catalyst (N203SD, manufactured by JGC Chemicals Co., Ltd.), and a rotor was put therein and capped. Hydrogen was introduced from the autoclave nozzle port and replaced three times.
And closed the valve. It was immersed in an oil bath maintained at 230 ° C., the stirrer was turned, and the inside was stirred. The reaction was continued for 6 hours. After allowing to cool and depressurize, the contents were taken out, washed and filtered with methanol (filter having a pore size of 1 μm), and the filtrate was analyzed by gas chromatography. The CHDM yield is 83.0 mol.
l%.

Example 3 (Oligomerization reaction) 7.9 g of CHDA, CHDM
46.8 g of water was taken in a flask equipped with a device for separating and extracting water, and reacted at 230 ° C. for 4 hours. The reaction solution was left untreated or subjected to esterification with methanol and analyzed by gas chromatography. The 1,4-cyclohexanedicarboxylic acid portion at the center of the oligomer was detected as dimethyl 1,4-cyclohexanedicarboxylate, and 14.9% by weight as 1,4-cyclohexanedicarboxylic acid (measured including unreacted CHDA). Was). Moreover, it titrated and analyzed with 0.1N-NaOH. It was measured as 0.5% by weight as acid (CHDA). CH
The DA conversion was 96.6 mol%.

(Second-stage reaction) Next, the tower diameter is 8 mm and the length is 25.
mm fixed bed isothermal reactor, catalyst (Nikki Chemical N203S
D copper / chromium / manganese catalyst). The oligomer solution obtained in the previous reaction was placed in this reactor at 140 ° C.
To 0.4 g / hr, hydrogen gas (purity 99.9%
Was introduced from the top of the reactor at 1500 ml / hr, and the temperature of the reactor became 240 ° C. The reactor pressure was kept at 8 MPa. Gas flowing out of the lower part of the reactor,
Separate the solution and leave the reaction solution untreated or methanol-free.
And then analyzed by gas chromatography and the like. CHDA conversion is 99.7 mol%, oligomer yield is 1.3 mol%, intermediate yield is 19.6 mol%,
The CHDM yield was 73.8 mol%.

Example 4 The same procedure as in Example 3 was carried out except that the pressure of the reactor was maintained at 12 MPa using the same oligomer solution. C
The HDA conversion was 99.9% and the oligomer yield was 0.2.
%, Intermediate yield 6.8%, CHDM yield 92.6%
Met.

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Claims (4)

[Claims] A mixture of 1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol is heated, if desired, to carry out an esterification reaction, and then the mixture or the esterification reaction product is hydrogenated. A process for producing 1,4-cyclohexanedimethanol. 2. A first step of producing 1,4-cyclohexanedicarboxylic acid by hydrogen reduction of terephthalic acid, 1,4-cyclohexanedicarboxylic acid obtained in the first step, and 1,4-cyclohexanedimethanol Mixed with
A second step of heating the mixture to perform an esterification reaction, if desired, and a third step of hydrogenating the mixture or the esterification reaction product to produce 1,4-cyclohexanedimethanol. Item 7. The method according to Item 1. 3. The method according to claim 2, wherein the 1,4-cyclohexanedimethanol obtained in the third step is used as 1,4-cyclohexanedimethanol in the second step. 4. The method according to claim 2, wherein a step of separating 1,4-cyclohexanedicarboxylic acid is provided between the first step and the second step.