KR102394356B1 - Preparation method of dimethylterephthalate - Google Patents

Abstract

The present invention relates to an efficient method for producing dimethyl terephthalate, and the method for producing dimethyl terephthalate (DMT) including an aromatization reaction using a metal catalyst and oxygen gas according to the present invention has a higher yield and recovery rate compared to the conventional method There is an advantage of being able to manufacture DMT with

Description

Method for producing dimethyl terephthalate {Preparation method of dimethylterephthalate}

The present invention relates to an efficient method for preparing dimethyl terephthalate.

As an example of replacing petroleum-derived substances by using biologically-derived substances, biodiesel produced from oil extracted from plants, such as rapeseed oil, soybean oil, and palm oil, through an esterification reaction, as a fuel usable in a diesel engine. In addition, bio-derived materials are being actively studied in the traditional polymer industry as well as replacing the energy materials. Among them, polylactic acid, a biodegradable polymer produced from lactic acid as a raw material, is an example that has reached the commercialization stage. PLA) and polytrimethylterephthalate (PTT) using 1,3-propandiol are representative examples.

On the other hand, dimethyl terephthalate (DMT), which is a representative raw material of polyester, is a compound having a structure of the following formula (Formula C ₁₀ H ₁₀ O ₄ , molecular weight 194):

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DMT is used as a major component of plastics, coatings, adhesives, and paints, and is used in various fields, such as synthesizing various types of dialcohols by reducing them.

In DMT, paraxylene (PX) is oxidized with oxygen using a metal catalyst such as cobalt (Co) and manganese (Mn) and a strong acid as a catalyst in an acetic acid solution to produce terephtalic acid (TPA), It is known to be obtained by esterification reaction of TPA and methanol prepared above, distillation under reduced pressure, and purification. DMT synthesized and purified in this way has a high purity of 99.9% or more, and can be used as a main raw material for polyester synthesis such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), etc. .

According to International Patent Publication No. WO2012/082725, DMT can be manufactured from dimethyl muconate and ethylene as raw materials, the manufacturing process has the following fundamental weaknesses.

First, in the case of the reaction using a solvent, the reaction time is too long, the conversion rate is 70% or less, and the generation of impurities is large. In addition, the reaction concentration is low, and there is a disadvantage that the commercial viability is lowered.

Second, in the case of a reaction that does not use a solvent, there are also disadvantages in that the reaction time is long, the yield is low, the generation of impurities is high, and the recovery rate is low. In addition, the reaction temperature is too high, and economical efficiency is deteriorated. In addition, since a catalyst that is difficult to regenerate or has a large decrease in activity is used, operability and economic efficiency are low during product production.

Therefore, while the present inventors were studying an efficient method for preparing DMT using ethylene, in dimethylcyclohex-2-ene-1,4-carboxylate obtained by addition cyclization of trans,trans-dimethylmuconate and ethylene The present invention was completed by confirming that DMT can be prepared with high yield and recovery rate by performing an aromatization reaction using a metal catalyst and oxygen gas.

International Patent Publication No. WO2012/082725

It is an object of the present invention to provide a method for economically and efficiently producing dimethyl terephthalate.

In order to achieve the above object, the present invention comprises the steps of dissolving dimethylcyclohex-2-ene-1,4-carboxylate of Formula 1 according to the present invention in a solvent; And it provides a method for producing dimethyl terephthalate comprising the step of performing an aromatization reaction by adding a metal catalyst and oxygen gas to the solution obtained in the above step.

The method for producing dimethyl terephthalate (DMT) including an aromatization reaction using a metal catalyst and oxygen gas according to the present invention has the advantage of being able to manufacture DMT with high yield and recovery rate compared to the conventional method.

Hereinafter, the present invention will be described in detail.

The present invention comprises the steps of dissolving dimethylcyclohex-2-ene-1,4-carboxylate of Formula 1 in a solvent; And it provides a method for producing dimethyl terephthalate comprising the step of performing an aromatization reaction by adding a metal catalyst and oxygen gas to the solution obtained in the above step:

As used herein, the term “aromatization reaction” refers to a reaction in which a derivative having an aliphatic ring shape is changed into a compound having an aromatic ring composed of the same number of atoms.

In the aromatization reaction according to the present invention, by removing 4 hydrogens from dimethylcyclohex-2-ene-1,4-carboxylate, DMT as a reaction product can be obtained. However, it is well known in the art that aromatization of the addition cyclized product obtained with ethylene gas is difficult in that four hydrogens must be removed. In the present invention, DMT can be obtained in high yield by easily removing four hydrogens by proceeding an aromatization reaction using a metal catalyst and oxygen gas in dimethylcyclohex-2-ene-1,4-carboxylate.

The solvents that can be used in step 1) of the preparation method according to the present invention are 2-methoxyethyl ether, ethylene glycol dimethyl ether, 2-ethoxyethyl ether, 2-dimethylaminoethyl ether, acetic acid, cyclohexane, and mixed solvents thereof. It may be selected from the group consisting of. According to one embodiment of the present invention, the solvent may be 2-methoxyethyl ether.

The concentration of dimethylcyclohex-2-ene-1,4-carboxylate dissolved in the solvent is 0.1 to 3 M, specifically 0.1 to 2.0 M, more specifically 0.1 to 1.5 M, most specifically 0.1 to It may be 1.0 M. When the concentration of dimethylcyclohex-2-ene-1,4-carboxylate exceeds 3 M, a side reaction may proceed, thereby reducing the DMT production yield.

The metal catalyst used in step 2) of the preparation method according to the present invention is palladium (Pd), platinum (Pt), nickel (Ni), cobalt (Co), copper (Cu), ruthenium (Ru), complexes thereof, and complexes thereof It may be any one selected from the group consisting of combinations. According to one embodiment of the present invention, the metal catalyst may be a palladium catalyst, more specifically Pd/C.

The aromatization reaction proceeds while injecting oxygen gas into the reactor, wherein the injected oxygen gas is 1 bar or more, specifically 1 to 20 bar, more specifically 1 to 15 bar, most specifically 1 to 10 bar can be injected at a pressure of According to an embodiment of the present invention, it may be injected at a pressure of 1 to 9 bar.

In addition, the aromatization reaction may be carried out at 100 °C or higher, specifically 100 to 300 °C, more specifically 110 to 250 °C, most specifically 130 to 200 °C. The reaction time may be from 1 to 48 hours, specifically from 2 to 24 hours, more specifically from 3 to 12 hours, most specifically from 4 to 10 hours. According to one embodiment of the present invention, the reaction may be carried out for 4 to 8 hours at the reflux temperature of the reaction mixture containing dimethylcyclohex-2-ene-1,4-carboxylate.

The aromatization reaction according to the present invention does not require any other treatment on the addition cyclization reactant, and it can be directly used for the aromatization reaction. can

In one embodiment of the present invention, Pd / C is added as a catalyst to 0.5 M dimethylcyclohex-2-ene-1,4-carboxylate solution dissolved in a solvent, and oxygen gas is injected to 1 to 9 bar of The aromatization reaction was carried out under pressure. As a result of analyzing the obtained product through gas chromatography-mass spectrometry, it was confirmed that DMT was prepared in high yield (Table 1).

Dimethylcyclohex-2-ene-1,4-carboxylate used as a starting material in the preparation method of the present invention can be obtained commercially or obtained through a cyclization reaction from dimethyl muconate. The dimethyl muconate may be trans, trans-dimethyl muconate. The trans, trans-dimethyl muconate may be prepared from muconic acid by adding a catalyst in a solvent.

The solvent used for the preparation of dimethyl muconate is alcohols such as methanol and ethanol; Polar solvents, such as methyl iodide (MeI), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO); alkyl ethers such as tetrahydrofuran (THF), diethyl ether, and dimethyl ethylene glycol; alkyl acetates such as ethyl acetate and methyl acetate; ketones such as methyl ethyl ketone (MEK) and acetone; aromatic solvents such as benzene, toluene, xylene, chlorobenzene, cresol, and methyl phenyl ester; organic solvents such as methylene chloride and chloroform; and mixtures thereof. According to one embodiment of the present invention, the solvent may be methanol.

In addition, the catalyst added for the production of dimethyl muconate is acids such as methanesulfonic acid, p-paratoluenesulfonic acid, phosphoric acid, hydrochloric acid, sulfuric acid; bases such as potassium carbonate and sodium hydroxide; and a mixed catalyst thereof. According to one embodiment of the present invention, the catalyst may be sulfuric acid.

In one embodiment of the present invention, trans, trans - Concentrated sulfuric acid was added to muconic acid as a catalyst, and then reacted under reflux conditions to obtain trans, trans-dimethyl muconate.

Next, trans, trans- dimethyl cyclohex-2-ene-1,4-carboxylate can be synthesized by an addition cyclization reaction from dimethyl muconate.

As used herein, the term “addition cyclization reaction” refers to a reaction in which two or more compounds of the same or heterogeneous nature are directly combined to form a different type of molecule.

The addition cyclization reaction may be carried out in a solvent, and the solvent may include an aromatic solvent such as benzene, toluene, chlorobenzene, cresol, methyl phenylester and xylene; alkyl ether solvents such as tetrahydrofuran, dimethyl ethylene glycol, ethylene glycol dimethyl ether and diglyme; alkyl acetate solvents such as methyl acetate, ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone; N-methylpyrrolidone (NMP); methylformamide; dimethyl sulfoxide; And it may be any one selected from the group consisting of mixtures thereof. According to one embodiment of the present invention, the solvent may be ethylene glycol dimethyl ether.

The solvent may be used in an amount of 1 to 200 equivalents, 10 to 100 equivalents based on dimethyl muconate.

For the addition cyclization reaction, the concentration of dimethyl muconate diluted in the solvent is 0.1 to 1 M, specifically 0.2 to 0.9 M, more specifically 0.3 to 0.8 M, more specifically 0.4 to 0.7 M, most specifically 0.5 to 0.6 M. According to an embodiment of the present invention, the concentration of dimethyl muconate may be 0.5 M.

The addition cyclization reaction according to the present invention can be carried out by adding ethylene gas. The ethylene gas may be added at a pressure of 1 bar or more, specifically 1 to 20 bar, more specifically 10 to 19 bar, and most specifically 15 to 18 bar. According to one embodiment of the present invention, ethylene gas may be added at a pressure of 17 bar.

In addition, the reaction may be carried out at 100 °C or higher, specifically 100 to 400 °C, more specifically 130 to 300 °C, most specifically 150 to 250 °C. The reaction time may be carried out for 1 to 48 hours, specifically 2 to 36 hours, more specifically 3 to 24 hours, more specifically 4 to 12 hours, and most specifically 5 to 10 hours. According to an embodiment of the present invention, the reaction may be performed at 200° C. for 8 hours.

In one embodiment of the present invention, trans, trans-dimethyl muconate is dissolved in ethylene glycol dimethyl ether solution to prepare a 0.5 M trans, trans-dimethyl muconate solution, and then ethylene gas is added to the solution at a pressure of 17 bar. was added, and an addition cyclization reaction was performed at 200° C. for 8 hours in a high pressure reactor to obtain dimethylcyclohex-2-ene-1,4-carboxylate.

Hereinafter, the present invention will be described in detail by the following Preparation Examples, Examples and Experimental Examples. However, the following Preparation Examples, Examples and Experimental Examples are only for illustrating the present invention, and the present invention is not limited thereto.

production example 1. Trans, trans- of dimethyl muconate synthesis

Trans, trans-Dimethyl muconate was synthesized from muconic acid by the following method.

First, 100 g of trans, trans-muconic acid is dissolved in 1,000 ml of methanol, 5 g of concentrated sulfuric acid is added as a catalyst, and reacted under reflux conditions to obtain 110 g of trans, trans-dimethyl muconate did.

production example 2. Trans, trans- dimethyl muconate Synthesis of addition cyclides

The trans, trans obtained in Preparation Example 1 was subjected to an addition cyclization reaction with dimethyl muconate to synthesize dimethylcyclohex-2-ene-1,4-carboxylate as an addition cyclate.

First, 110 g of trans, trans-dimethyl muconate was dissolved in 1,300 ml of ethylene glycol dimethyl ether to prepare a 0.5 M trans, trans-dimethyl muconate solution. Then, ethylene gas was injected into the solution, pressurized to a pressure of 17 bar, and an addition cyclization reaction was performed in a high pressure reactor (Parr reactor, 4533HP) at 200° C. for 8 hours.

As a result, 125 g of dimethylcyclohex-2-ene-1,4-carboxylate was obtained.

Example 1. Aromatic reaction of addition cyclization reactant-(1)

DMT was synthesized by performing an aromatization reaction with the addition cyclization reactant obtained in Preparation Example 2 above.

First, 20 g of dimethylcyclohex-2-ene-1,4-carboxylate was dissolved in 250 ml of 2-methoxyethyl ether, followed by a 0.5 M solution of dimethylcyclohex-2-ene-1,4-carboxylate. was prepared. 0.11 g of Pd/C as a catalyst was added to the prepared solution, oxygen (O ₂ ) as an oxidizing agent was continuously injected, and an aromatization reaction was performed under reflux conditions and atmospheric pressure for 4 hours.

Example 2. Aromatic reaction of addition cyclization reactant-(2)

The aromatization reaction was performed in the same manner as in Example 1, except that the aromatization reaction was performed for 8 hours.

Example 3. Aromatic reaction of addition cyclization reactant-(3)

An aromatization reaction was carried out in the same manner as in Example 1, except that a 1.0 M dimethylcyclohex-2-ene-1,4-carboxylate solution and 0.22 g of Pd/C were reacted for 8 hours. did.

Example 4. Aromatic reaction of addition cyclization reactant-(4)

The aromatization reaction was performed in the same manner as in Example 1, except that the pressure of the reactor was continuously pressurized with O ₂ to maintain 9 bar.

comparative example 1. Aromatic reaction of addition cyclization reactant-(5)

In the same manner as in Example 2, except that 0.2 M of a dimethylcyclohex-2-ene-1,4-carboxylate solution and 0.06 g of Pd/C were used, and air was injected instead of O ₂ An aromatization reaction was carried out.

comparative example 2. Aromatic reaction of addition cyclization reactant-(6)

An aromatization reaction was performed in the same manner as in Example 2, except that air was injected instead of O ₂ .

Experimental example 1. Manufactured DMT analysis of

In order to analyze the yield of DMT obtained in Examples 1 to 4 and Comparative Examples 1 and 2, gas chromatography-mass spectrometry (GC-MS) was performed under the following conditions.

- Instrument: Claus 680 GC and SQ 8 MS from Perkin Elmer

- Column: DB-5 (15 m×0.25 mm×0.10 μm, Agilent Technologies, USA)

The reaction conditions of each Example and Comparative Example, and the results of the GC-MS are shown in Table 1 below.

reactive gas Catalyst amount (g) reactant
Concentration (M) reaction time
(h) Dimethylcyclohex-2-ene-1,4-carboxylate (%) DMT Conversion Rate (%) Example 1 Oxygen (atmospheric pressure) 0.11 0.5 4 49.6 49.2 Example 2 Oxygen (atmospheric pressure) 0.11 0.5 8 1.5 90.8 Example 3 Oxygen (atmospheric pressure) 0.22 1.0 8 2.9 87.5 Example 4 Oxygen (pressurized) 0.11 0.5 4 0.8 93.3 Comparative Example 1 Air (atmospheric pressure) 0.06 0.2 8 5.4 83.4 Comparative Example 2 Air (atmospheric pressure) 0.11 0.5 8 28.8 53.6

* The ratio (%) and DMT conversion (%) of the remaining dimethylcyclohex-2-ene-1,4-carboxylate in the above is the GC of dimethylcyclohex-2-ene-1,4-carboxylate as the starting material of the reaction. When the -MS area value is 100, the ratio of the GC area values shown in GC-MS of dimethylcyclohex-2-ene-1,4-carboxylate and DMT is respectively shown.

As shown in Table 1, the Examples in which the reaction was carried out using only pure oxygen gas during the aromatization reaction showed a higher DMT conversion rate than the Comparative Examples using air. In particular, in the case of Example 2, the DMT conversion rate was significantly higher than that of Comparative Example 2 in which air was injected instead of oxygen. In the case of Example 1, the absolute value of the DMT conversion rate is low compared to Comparative Example 2, but the reaction time is very short by half, and when the reaction time is increased to 8 hours as in Comparative Example 2 under the same conditions, DMT as in Example 2 The conversion rate will increase significantly.

On the other hand, when oxygen gas is used, a high DMT conversion rate can be obtained even with a high concentration of reactants. Example 2 and Comparative Example 1 have similar DMT conversion rates, but since Example 2 uses a high reactant concentration, as a result, DMT production is remarkably high.

Claims (13)

1) dissolving dimethylcyclohex-2-ene-1,4-carboxylate of Formula 1 in a solvent; and
2) A method for producing dimethyl terephthalate, comprising adding a metal catalyst to the solution obtained in step 1) and performing an aromatization reaction by injecting pure oxygen gas at a pressure of 1 to 9 bar:
[Formula 1]

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The group of claim 1, wherein the solvent in step 1) is 2-methoxyethyl ether, ethylene glycol dimethyl ether, 2-ethoxyethyl ether, 2-dimethylaminoethyl ether, acetic acid, cyclohexane, and mixtures thereof. selected from, a manufacturing method.
The method according to claim 1, wherein dimethylcyclohex-2-ene-1,4-carboxylate is dissolved in a concentration of 0.1 to 3 M in step 1).
According to claim 1, wherein the metal catalyst of step 2) is palladium (Pd), platinum (Pt), nickel (Ni), cobalt (Co), copper (Cu), ruthenium (Ru), complexes thereof, and combinations thereof Any one selected from the group consisting of, the manufacturing method.
The method according to claim 4, wherein the metal catalyst is a palladium catalyst.
The method according to claim 4, wherein the metal catalyst is added in an amount of 0.01 to 0.1 g per 0.1 M of dimethylcyclohex-2-ene-1,4-carboxylate of formula (1).
delete The method according to claim 1, wherein the aromatization reaction of step 2) is performed for 4 to 10 hours.
The method according to claim 1, wherein the aromatization reaction of step 2) is performed under reflux conditions of a solvent.
The method according to any one of claims 1 to 6, 8, and 9, wherein the dimethylcyclohex-2-ene-1,4-carboxylate of Formula 1 is dimethyl muconate and ethylene gas as a solvent. A production method obtained by reacting in
The method according to claim 10, wherein the dimethyl muconate is trans,trans-dimethylmuconate.
The method according to claim 10, wherein the concentration of dimethyl muconate is 0.1 to 1 M.
The method of claim 10, wherein the solvent is ethylene glycol dimethyl ether.