JPH1045645A - Production of 1,4-cyclohexanedimethanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing 1,4-cyclohexanedimethanol(CHDM) by two-stage hydrogenation of a dialkyl terephthalate with the 2nd stage hydrogenation under conditions milder than the case with the 1st stage hydrogenation. SOLUTION: This method for producing CHDM by hydrogenating a dialkyl terephthalate is made up of the following two processes: (1) 1st process: the corresponding 1,4-cyclohexanedicarboxylic dialkyl ester is produced by hydrogenating a dialkyl terephthalate in the presence of a noble metal-based nuclear hydrogenation catalyst, and (2) 2nd process: the objective CHDM is obtained by hydrogenolysis of the resultant 1,4-cyclohexanedicarboxylic dialkyl ester in the presence of a copper-zinc-alumina-based catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing 1,4-cyclohexanedimethanol (hereinafter sometimes abbreviated as CHDM) by two-stage hydrogenation of terephthalic acid dialkyl ester. CHDM is useful as a raw material for polyester-based paints, polyester-based synthetic fibers, synthetic resins, and the like, and is particularly used as a raw material for resins having excellent heat resistance, weather resistance, physical strength, and the like.

[0002]

2. Description of the Related Art As a method for producing CHDM, a method of hydrogenating dialkyl terephthalate in a two-stage process using a fixed-bed reactor is generally used, and several methods have been proposed. For example, US Pat. No. 3,334,334
No. 149 discloses the use of dialkyl terephthalate as a raw material, hydrogenation of a benzene ring with a palladium / alumina supported catalyst, and subsequent hydrogenolysis of the ester portion of the first-stage reaction solution using a copper chromite catalyst. C
Methods for generating HDM have been proposed.

JP-A-6-192146 also discloses that a dialkyl terephthalate is used as a raw material, a benzene ring is hydrogenated with a ruthenium / alumina supported catalyst, and then the ester portion is hydrogenated with a copper chromite catalyst. Decomposition methods have been proposed.

[0004]

However, any of these methods has some problems in industrialization. For example, in the method of U.S. Pat.
It had to be carried out under considerably severe conditions of 0 ° C. and a pressure of 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. Although the reaction conditions disclosed in JP-A-6-192146 are rather mild, it is still necessary to use a substantial excess of hydrogen with respect to the theoretical amount. Among them, the second-stage ester hydrocracking compared to the first-stage nuclear hydrogenation reaction,
High temperatures, high pressures, and the use of excess hydrogen are required, which is a technology point. Further, when considering treatment of a spent catalyst, it is not preferable that the copper chromite catalyst contains toxic chromium. An object of the present invention is to produce CHDM by two-stage hydrogenation of terephthalic acid dialkyl ester, particularly under the milder condition of the second stage hydrogenation reaction.
Moreover, it is an object of the present invention to provide a method which can be carried out using an environmentally safe catalyst.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, obtained by hydrogenating the benzene nucleus of dialkyl terephthalate in the first stage using a noble metal catalyst. Hydrogenolysis of the resulting 1,4-cyclohexanedicarboxylic acid dialkyl ester in the second stage by using a copper-zinc-aluminum catalyst,
It has been found that the present invention can be carried out under milder conditions and that the excess amount of hydrogen can be reduced, and the present invention has been completed.

That is, the present invention relates to a method for producing 1,4-cyclohexanedimethanol by hydrogenating a dialkyl terephthalate, and 1) hydrogenating the dialkyl terephthalate using a noble metal-based nuclear hydrogenation catalyst. A first step of obtaining a 1,4-cyclohexanedicarboxylic acid dialkyl ester, and 2) hydrogenolysis of the 1,4-cyclohexanedicarboxylic acid dialkyl ester obtained in the first step using a copper-zinc-alumina-based catalyst And a second step of obtaining 1,4-cyclohexanedimethanol, which is a method for producing 1,4-cyclohexanedimethanol. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) First Step In the first step, the benzene nucleus of the dialkyl terephthalate is hydrogenated using a noble metal-based hydrogenation catalyst to obtain 1,4.
This is a so-called first-stage hydrogenation step for producing dialkyl cyclohexanedicarboxylate (hereinafter sometimes abbreviated as CHDC).

The dialkyl terephthalate used as a raw material of the present invention is selected from esters of lower alcohols having an alkyl group of up to 4 carbon atoms, since alcohol by-produced by hydrogenolysis is easily separated by distillation. Among them, dimethyl ester (hereinafter, may be abbreviated as DMT) can be used most advantageously. The quality of the raw material terephthalic acid dialkyl ester is sufficient to the extent that it is commercially available as an industrial raw material.

However, the first-stage reaction is an exothermic reaction, and the raw material dialkyl terephthalate is not affected by this reaction in order to appropriately suppress the temperature rise due to the heat of reaction and to increase the reaction rate. An active solvent is added as a diluent, and the concentration of dialkyl terephthalate in the feed to the first stage is 1 to 50% by weight, preferably 5 to 2% by weight.
It is preferable to dilute to 0% by weight. If the concentration of the dialkyl terephthalate in the feed solution is lower, the reaction rate decreases, which is disadvantageous. If the concentration is higher, the temperature rise in the reactor increases, which is disadvantageous.

As such a solvent, for example, CHD
M, tetrahydrofuran, 1,4-dioxane and the like can be mentioned, but it is advantageous to cool and recycle the first-stage reaction product as needed. This case is preferable because it can be recovered by a subsequent separation operation, and further, unnecessary components are not mixed into the reaction system.

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.
It is preferably at least mol%. The amount of hydrogen is 3 to 5 in molar ratio with respect to the starting dialkyl terephthalate.
About 0 times is preferable, but when it is less than 3 times, unreacted substances increase, which is not preferable. In addition, even if it exceeds 50 times this range, the reaction rate does not increase so much, which is economically disadvantageous.

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, with ruthenium being preferred. These are used as supported catalysts, and activated carbon, alumina, silica, diatomaceous earth and the like are used as carriers. Alumina is particularly preferably used. As a ruthenium-supported catalyst, for example, NE
0.5% ruthenium / alumina manufactured by Chemcat Corporation.

The supported amount of ruthenium is 0.1 to 10% by weight, preferably 0.5 to 3% by weight of the total amount of the catalyst (including the support).
% By weight. If the supported amount is too small, the activity per catalyst weight decreases, and a large amount of catalyst is required, which is not economical. In addition, when the amount is too large, the reaction rate cannot be improved corresponding to the supported metal, and the loss of the supported ruthenium metal is relatively large, which is not preferable.
As a form of the catalyst, it is common to use a catalyst supported on a granular or pellet carrier of about 1 to 6 mm. If it is too small, the resistance when the liquid and gas pass through the catalyst layer increases, and the pressure loss in the reactor increases. Further, it becomes difficult to fix the catalyst. Conversely, if it is too large, the diffusion resistance inside the catalyst increases the portion where the inside of the catalyst does not effectively contribute to the reaction, and causes a reduction in the reaction rate.

The reaction system may be either a liquid phase suspension reaction or a fixed bed reaction, but a fixed bed reaction is preferred. In this case, a method of removing the reaction heat through a heat medium by using a multi-tube reactor may be considered. However, since the type of the apparatus may be complicated and not economical, an adiabatic reactor is simply used. . The raw material liquid and hydrogen are introduced from the upper or lower end 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 where they are introduced.

It is preferable that the amount charged to the reactor can be as large as possible within a range where the conversion of the unreacted substance 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 it unambiguously, it is usually 0.5 to 0.5 LHSV (the space velocity per hour of the charged liquid when the catalyst filling volume is 1).
It is preferably set to 10. Reaction temperature is 70-200
C is preferable, and more preferably in the range of 100C to 160C. If the ratio is out of this range, unreacted substances remain when the amount is low, and the amount of by-products increases when the amount is high. In any case, the yield decreases, which is not preferable. The reaction pressure is 5
150 kgf / cm ² , preferably ^{20 to} 150 kgf
/ Cm ² . If the reaction pressure is too low, not only the reaction rate will be reduced, but also the production of by-products will increase. Also,
When the reaction pressure exceeds 150 kgf / cm ² , the reaction rate does not increase so much even if it is higher than that, which is economically disadvantageous. The conversion of the reactants is usually 95% or more,
Preferably it is 99% or more. When unreacted dialkyl terephthalate is hydrogenated in a second-stage reactor described below, the desired CHDM cannot be obtained, resulting in an increase in by-products and a decrease in yield. There is also an effect of reducing the reaction rate of the second stage.

(2) Second Step The second step is a so-called second step in which the ester portion of 1,4-cyclohexanedicarboxylic acid dialkyl ester is hydrogenolyzed using a copper-zinc-alumina catalyst to produce CHDM. This is the step of the hydrogenation reaction.

As a raw material used in the second-stage reaction, the first-stage reaction product can be used as it is, but the second-stage reaction is also an exothermic reaction, and the temperature rise due to the heat of reaction is moderately increased. In order to suppress the reaction and increase the reaction rate, a solvent inert to the reaction is added to the reaction product of the first stage, and the concentration of CHDC in the feed solution to the second stage is 5 to 50% by weight, preferably Is preferably diluted to 10 to 30% by weight. If the concentration of CHDC in the feed solution is lower, the reaction rate decreases, which is disadvantageous. If the concentration is higher, the temperature rise in the reactor increases, which is disadvantageous.

As such a solvent, for example, CHD
M, tetrahydrofuran, 1,4-dioxane and the like can be mentioned, but it is advantageous to cool the second stage reaction product if necessary and recycle it for use. Further, there is an advantage that the yield of CHDM is improved by diluting with a reaction solution. And in this case, as the supply liquid to the second stage,
1: 1 to 1: of the first-stage reaction product and the second-stage reaction product
It is convenient to use a mixture of 20 (weight ratio) with a CHDC concentration in the above range.

The quality of hydrogen is sufficient for industrially used hydrogen, and may contain an inert gas such as nitrogen or methane, but preferably contains 50 mol% or more of hydrogen. The amount of hydrogen is preferably about 5 to 50 times the molar ratio of 1,4-cyclohexanedicarboxylic acid dialkyl ester, but if the amount is less than 5 times, the reaction rate is undesirably slow. In addition, even if the ratio exceeds 50 times, the reaction speed does not increase so much, which is economically disadvantageous.

The catalyst used in the second-stage reaction is a copper-zinc-alumina catalyst, and its composition is in an oxidized state, containing 30 to 70% by weight of copper oxide and 20 to 70% by weight of zinc oxide.
Preferably, the content is 60% by weight and the aluminum oxide content is 3 to 20% by weight. Outside of this range, the amount of by-products increases and the yield of 1,4-cyclohexanedimethanol is significantly reduced, which is not preferable. As such a copper-zinc-alumina catalyst, for example, C18-HC manufactured by Toyo CCI Co., Ltd. can be mentioned.

The reaction system may be either a liquid phase suspension reaction or a fixed bed reaction, but a fixed bed reaction is preferred. In this case, a method of removing the reaction heat through a heat medium by using a multi-tube reactor may be considered. However, since the type of the apparatus may be complicated and not economical, an adiabatic reactor is simply used. . The raw material liquid and hydrogen are introduced from the upper or lower end 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 where they are introduced.

It is preferable that the amount charged to the reactor can be charged as much as possible within a range where the conversion of the reactants 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 usually preferable to set LHSV to 0.1 to 1. The reaction temperature is preferably from 160 to 300 ° C, more preferably from 200 to 280 ° C. If the ratio is out of this range, unreacted substances remain when the amount is low, and the amount of by-products increases when the amount is high. In any case, the yield decreases, which is not preferable. Reaction pressure is 50-300kgf / c
m ² , more preferably in the range of 100 to 200 kgf / cm ² . If the reaction pressure is too low, not only the reaction rate will be reduced, but also the production of by-products will increase. When the reaction pressure is 3
If it exceeds 00 kgf / cm ² , the reaction rate does not increase so much even if it is higher than that, which is economically disadvantageous. A higher conversion is economically advantageous, usually 97%.
% Or more, preferably 99% or more. Unreacted 1,4
-When the amount of dialkyl cyclohexanedicarboxylate is large, purification is difficult, resulting in quality deterioration.

[0023]

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) A catalyst (0.5% by NE Chemcat) was placed in a fixed-bed isothermal reactor having a tower diameter of 20 mm and a length of 400 mm.
(Ruthenium / alumina) was filled in an amount of 50 ml. Hydrogenation reaction was carried out by introducing 100 ml / hr of 10% DMT / CHDC and 30 NL / hr of hydrogen gas (purity of 99.9% or more) into the reactor from the lower part of the reactor. A heating medium was circulated outside the reactor so that the temperature of the catalyst layer became 120 ° C. The reactor pressure was maintained at 40 kgf / cm ² . Gas and liquid flowing out from the upper part of the reactor were separated, and the reaction liquid was analyzed by gas chromatography. The conversion of DMT was 99.3%, and the CHDC concentration in the reaction solution was 98.9%.

(Second-stage reaction) A fixed bed isothermal reactor having a tower diameter of 25 mm and a length of 1 m was charged with a catalyst (C, manufactured by Toyo CII Co., Ltd.).
400 ml of 18-HC copper / zinc / alumina catalyst)
Filled. In this reactor, 20 parts by weight of the reaction solution obtained in the first-stage reaction and CHDC (Kanto Chemical Co., Ltd., reagent first grade)
A hydrogenation reaction was carried out by introducing 80 parts by weight of the mixed solution at 200 ml / hr and hydrogen gas (purity of 99.9% or more) at 90 NL / hr from the top of the reactor. 240 ° C outside the reactor
And the average temperature of the reactor was 240 ° C. The reactor pressure was maintained at 140 kgf / cm ² .
Gas and liquid flowing out from the upper part of the reactor were separated, and the reaction liquid was analyzed by gas chromatography. CH in the reaction solution
No DC was detected. The yield of CHDM from CHDC was 69.4%.

Example 2 (First-stage reaction) The first-stage reaction was carried out in the same manner as in Example 1 to obtain a first-stage reaction solution. (Second Stage Reaction) As the liquids for the second stage reaction, 20 parts by weight of the first stage reaction solution and the second stage reaction solution 8 obtained in Example-1 were used.
Using a mixture of 0 parts, a hydrogenation reaction was carried out under the same conditions as in Example-1. The reaction solution was analyzed by gas chromatography. CHDC was not detected in the reaction solution. C
The yield from HDC to CHDM was 83.5%.

Example 3 (First-stage reaction) A hydrogenation reaction was carried out using the same catalyst packed in the same reactor as in Example 2. 6% in this reactor
65 ml / hr of DMT / CHDC, hydrogen gas (purity 9
(9.9% or more) was introduced at 1.6 NL / hr from the lower part of the reactor to carry out a hydrogenation reaction. A heating medium was circulated outside the reactor so that the temperature of the catalyst layer became 140 ° C. The reactor pressure was kept at 50 kgf / cm ² . Gas and liquid flowing out from the upper part of the reactor were separated into gas and liquid, and the reaction solution was analyzed by gas chromatography. 99.9% conversion of DMT
Met. The CHDC concentration in the reaction solution was 98.5%.

(Second Stage Reaction) A mixture of 10 parts by weight of the first stage reaction solution and 90 parts of the second stage reaction solution obtained in Example 1 was used as the liquid for the second stage reaction. A hydrogenation reaction was performed under the same conditions as in Example-1. The reaction solution was analyzed by gas chromatography. CHDC was not detected in the reaction solution. The yield from CHDC to CHDM is 79.8%.
Met.

Example 4 (First-stage reaction) The first-stage reaction was carried out in the same manner as in Example 3, to obtain a first-stage reaction solution. (Second Stage Reaction) As the liquids for the second stage reaction, 20 parts by weight of the first stage reaction solution and the second stage reaction solution 8 obtained in Example-1 were used.
A hydrogenation reaction was carried out under the same conditions as in Example 1 except that a mixture of 0 parts was used and the average reaction temperature was adjusted to 220 ° C. The reaction solution was analyzed by gas chromatography. CHDC was not detected in the reaction solution. CH
The yield from DC to CHDM was 85.4%.

Example-5 (First-stage reaction) The first-stage reaction was carried out in the same manner as in Example 1 to obtain a first-stage reaction solution. (Second-stage reaction) The reaction solution obtained in the first-stage reaction was 200 m
1 / hr and hydrogenation reaction was carried out, and the average reaction temperature was 3
The reaction was carried out in the same manner as in Example 1, except that the temperature of the heating medium was adjusted to 10 ° C. CHD in the reaction solution
C was not detected. The yield of CHDM from CHDC was 47.2%.

Comparative Example 1 (First-Step Reaction) The first-step reaction was carried out in the same manner as in Example 1 to obtain a first-step reaction solution. (Second Step Reaction) The reaction was carried out in the same manner as in Example 1 except that a copper / zinc-based catalyst (Nissan Gardler G-66B) was used as the catalyst. CHDC conversion is 98.2%, CHDM
The yield was 23.1%. Comparative Example 2 (First-Step Reaction) The first-step reaction was carried out in the same manner as in Example 1 to obtain a first-step reaction solution. (Second Step Reaction) The reaction was carried out in the same manner as in Example 1, except that a copper / chromium-based catalyst (Nissan Gardler G-13) was used as the catalyst. CHDC conversion is 81.3%, CHDM
The selectivity was 13.7%.

[0032]

According to the present invention, in the production of CHDM by two-stage hydrogenation of terephthalic acid dialkyl ester, the second stage hydrogenation reaction, which had conventionally required severe conditions, is carried out under milder conditions. It can be carried out using an environmentally safe catalyst, and its industrial significance is great.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C07C69 / 75 C07C69 / 75Z // C07B 61/00 300 C07B 61/00 300 (72) Invention Taken Ken Takeuchi 1 Toho-cho, Yokkaichi-shi, Mie Inside the Yokkaichi office of Mitsubishi Chemical Corporation

Claims (8)

[Claims] 1. A process for producing 1,4-cyclohexanedimethanol by hydrogenating a dialkyl terephthalate, comprising the steps of: 1) hydrogenating the dialkyl terephthalate using a noble metal-based nuclear hydrogenation catalyst to obtain 1,4-cyclohexanedimethanol; A first step of obtaining a dialkyl cyclohexanedicarboxylate; and 2) hydrogenolysis of the 1,4-cyclohexanedicarboxylic dialkylester obtained in the first step using a copper-zinc-alumina catalyst to obtain 1,4 A method for producing 1,4-cyclohexanedimethanol, which comprises two steps of a second step of obtaining cyclohexanedimethanol. 2. The method according to claim 1, wherein a ruthenium-alumina catalyst is used as the noble metal-based hydrogenation catalyst in the first step. 3. The dialkyl terephthalate fed to the first step is diluted with an inert solvent.
Or the method of 2. 4. The method according to claim 3, wherein the reaction product liquid of the first step is used as an inert solvent for diluting the dialkyl terephthalate supplied to the first step. 5. The method according to claim 1, wherein the dialkyl 1,4-cyclohexanedicarboxylate supplied to the second step is diluted with an inert solvent. 6. The method according to claim 5, wherein the reaction solution of the second step is used as an inert solvent for diluting the 1,4-cyclohexanedicarboxylic acid dialkyl ester supplied to the second step. 7. A 1: 1 to 1: 1 mixture of the reaction product liquid of the first step and the reaction product liquid of the second step as a supply liquid to be supplied to the second step.
7. The process according to claim 1, wherein a mixture of 20 (weight ratio) is used. 8. The method according to claim 1, wherein dimethyl terephthalate is used as the dialkyl terephthalate.