KR101341449B1 - Preparation of p-Chloromethylbenzoic acid and Benzoic acid from by-products in method for processing dimethyl terephthalate - Google Patents

Abstract

The present invention relates to a process for producing high value-added p-chloromethylbenzoic acid and benzoic acid from methyl-p-toluate and methyl benzoate, which are by-products generated in the process of preparing dimethyl terephthalate.

Description

Preparation of p-Chloromethylbenzoic acid and Benzoic acid from by-products in method for processing dimethyl terephthalate}

The present invention provides added value from methyl p-toluate (MPT) and methyl benzoate (MBZ), which are by-products generated in the manufacturing process of dimethyl terephthalate (DMT). It relates to a process for producing high p-Chloromethylbenzoic acid (CMBA) and benzoic acid (BA).

BA is a white crystal and dissolves in organic solvents such as methanol and acetone and hot water.It is itself used as a food additive such as preservatives and as a basic raw material for high value added substances such as aspirin and pharmaceutical intermediates. It is used.

Conventional methods for preparing such BA are shown in Scheme 1 below.

[Reaction Scheme 1]

As shown in Scheme 1, benzoic acid is synthesized by air oxidation in the presence of a catalyst in the presence of a catalyst in order to produce BA by conventional conventional methods.

In addition, CMBA is a white crystal that is dissolved in ether, ethanol and hot water, and is used as a raw material for pharmaceutical intermediates such as optical brighteners and p-amino methylbenzoic acid.

Thus, a conventional method of preparing CMBA is shown in Scheme 2 below.

[Reaction Scheme 2]

As shown in Scheme 2, in order to prepare the CMBA by the conventional conventional method, CMBA is first synthesized through a chlorination reaction under p-toluic acid catalyst.

Dimethyl terephthalate (DMT) esterifies terephthalic acid ("TPA") obtained by oxidation of p-xylene (hereinafter referred to as "PX") with methanol. Produced. By-products such as MPT, MBZ, and OX (o-Xylene, OX) are generated in the DMT manufacturing process.

At present, these by-products are practically disposed of because they have no special use.

Therefore, in the present invention, organic matter except mixed acid is removed from the by-products of the DMT manufacturing process through hydrolysis reaction, and BA is purely separated using a suitable solvent, and CMBA is purified purely through chlorination from the mixture from which BA is removed. Could be separated.

Accordingly, it is an object of the present invention to provide a method for producing high-purity BA and CMBA having high utility value at low cost through a simple reaction and purification process from waste by-products generated in the DMT manufacturing process.

The method for preparing p-chloromethylbenzoic acid and benzoic acid from the by-product of the dimethyl terephthalate manufacturing process according to the present invention for achieving the above object comprises the following steps:

(a) Aqueous NaOH solution was added to the reaction by-product of the DMT manufacturing process including methyl-p-toluate (MPT), methyl benzoate (MBZ), dimethyl terephthalate (DMT) and o-xylene (OX), followed by reaction. Producing sodium mixed acid comprising benzoic acid (BA), p-toluic acid (p-TA) and terephthalic acid (TPA);

(b) separating or extracting an organic material including OX from the reaction solution of step (a);

(c) adding acid to the aqueous solution of step (b) to separate mixed acids of BA, p-TA and TPA in solid phase, and then recovering;

(d) adding an organic solvent to the mixed acid obtained in step (c) to separate TPA and impurities into a solid phase;

(e) crystallizing the filtrate obtained in step (d) to separate the mixture of p-TA and BA, and then recovering it;

(f) adding a solvent to the p-TA and BA mixture of step (e) and crystallizing to separate a filtrate containing a mixture containing at least 85% by weight of p-TA and a mixture containing at least 85% by weight of BA. Then recovering each;

(g) producing a mixture including CMBA through a chlorination reaction from the mixture containing at least 85% by weight of the p-TA obtained in step (f), and then purifying and recovering CMBA with high purity therefrom; And

(h) recovering the high purity BA by concentrating the filtrate from a mixture containing at least 85% by weight of the BA obtained in step (f).

In the method of the present invention, the reaction by-products of the DMT manufacturing process include 40 to 45% by weight of MPT, 43 to 48% by weight of MBZ, 5 to 8% by weight of DMT, and 2 to 5% by weight of OX.

In the method of the present invention, the reaction temperature of step (a) is characterized in that 80 ~ 90 ℃.

In the method of the present invention, in the step (b), the organic material is characterized in that extracted directly or using an aromatic solvent.

In the method of the present invention, the acid of step (c) is characterized in that hydrochloric acid.

In the method of the present invention, the chlorination reaction of step (g) is carried out in the presence of a catalyst, the chlorinating agent is Cl ₂ , POCl ₃ , SOCl ₂ , or SO ₂ Cl ₂ , the amount of p-TA 1 equivalent It is characterized by 1.0 to 1.8 equivalents.

In the method of the present invention, the catalyst is 1,1-azobis (cyclohexanecarbonitrile), and the amount thereof is 1 to 5 parts by weight based on 100 parts by weight of p-TA.

As described above, the BA and CMBA manufacturing method according to the present invention is a new process that is not known in the prior art, which is a high value-added material from the by-products generated in the DMT manufacturing process, which are mostly discarded and used only for some limited purposes. BA and CMBA can be obtained through simple separation and preparation methods. By utilizing such wastes, there is an advantage that high-value separation and purification of BA and CMBA, which can be utilized, is possible.

Hereinafter, the present invention will be described in more detail.

As described above, in the present invention, using P-xylene as a starting material, DMT tablets including MPT, MBZ, DMT, and OX generated during the preparation of DMT through oxidation and esterification reactions. Hydrolysis from the byproducts of the process produces p-toluic acid (hereinafter referred to as "p-TA"), mixed acids such as BA and TPA, and separates and removes organic substances such as OX, which are impurities therefrom. The BA is purely separated using a suitable solvent, and a CMBA is prepared from the remaining BA, p-TA, TPA and the like by chlorination reaction, and then the CMBA is separated purely from the mixture.

The by-product of the DMT manufacturing process according to the present invention is a mixture of by-products produced in the manufacturing process as shown in Scheme 3 below.

Scheme 3

Oxidation reactants produced through the liquid phase oxidation of p-xylene contain various impurities such as BA, p-TA, and OX in addition to TPA. These TPA and impurities are converted into DMT, MBZ, MPT, OX by esterification with excess methanol, and the DMT is separated by fractional vacuum distillation under high temperature, and 80-90% by weight of intermediate products MBZ and MPT are contained in the remaining by-products. It is contained in large quantities.

As such, the by-products generated during the DMT manufacturing process may vary depending on the DMT manufacturing process. However, when the mixture of the by-products obtained when the reaction rate of the DMT is sufficiently increased, MPT 40-45 wt%, MBZ 43-48 wt% , 5 to 8% by weight of DMT and 2 to 5% by weight of OX. Worldwide, Eastman Kodak, DuPont, and SK Emulsion have adopted this DMT manufacturing process, and the by-products generated are generally discarded or only partially used.

Therefore, in the present invention, p-xylene is used as a starting material to separate and prepare high-value BA and CMBA, respectively, from by-products generated during the production of DMT through oxidation and esterification.

First, according to a preferred embodiment of the present invention, as shown in Scheme 4, NaOH aqueous solution is added to the reaction by-product of the DMT manufacturing process, preferably heated to a temperature of 80 ~ 90 ℃ hydrolysis reaction BA, p- A mixed acid sodium salt of TA and TPA is produced. In this case, before the NaOH aqueous solution is added to the reaction byproduct, an organic solvent such as alcohol or a mixed solvent of organic solvent and water may be added to the reaction byproduct, and then NaOH aqueous solution may be added. The amount of the sodium hydroxide is preferably 1.5 to 2.5 equivalents based on 1 equivalent of the mixed acid, and when excessively used, it is uneconomical as malignant wastewater is generated during neutralization.

The mixed sodium salt thus produced is present in the aqueous phase. Organic substances such as OX, which are unreacted, can be separated from the aqueous layer by the organic layer, and can be directly separated or by an organic solvent such as toluene. Extractable separation. After removing the organics, an acid such as hydrochloric acid is added to an aqueous mixed acid solution present in the aqueous solution layer to acidify the pH to 1-2, and the mixed acid produced as a solid is collected by filtration at room temperature, and the filtrate is treated with wastewater.

[Reaction Scheme 4]

Then, using a solvent suitable for a mixed acid such as BA, p-TA and TPA obtained, TPA and impurities are separated and removed as solids, as shown in Scheme 5 below, and the composition of the filtrate is p-TA and BA ( About 1: 1) present in mixture. At this time, the organic solvent used is preferably a solvent such as acetonitrile, aqueous methanol solution or chlorobenzene, more preferably aqueous methanol solution.

[Reaction Scheme 5]

From the p-TA and BA (about 1: 1) mixture of the filtrate thus obtained, a mixture containing at least 85% by weight of p-TA as a solid content through a crystallization method through concentration as in Scheme 6, typically p-TA And a mixture of BA (about 9: 1) and a mixture containing at least 85% by weight of BA, typically a mixture of p-TA and BA (about 1: 9), respectively. At this time, as a solvent, a mixed solvent of methanol and water is preferable, but an organic solvent such as acetonitrile may be used.

[Reaction Scheme 6]

According to the present invention, a CMBA is prepared through chlorination in the presence of a catalyst by adding an organic solvent, preferably chlorobenzene, to a mixture containing at least 85 wt% of p-TA, a solid obtained through filtration. . The produced CMBA in the reaction solution is filtered through the crystallization of the solid CMBA and repurchase to obtain a high purity CMBA.

[Reaction Scheme 7]

In Scheme 7, the chlorination reaction is preferably maintained at a reaction temperature of 80 ~ 90 ℃ to minimize the by-products. ABC (1,1-azobis (cyclohexanecarbonitrile)) and the like may be used as the catalyst, the amount of the catalyst is used 1 to 5 parts by weight based on 100 parts by weight of p-TA, most preferably 4 parts by weight. When the amount of catalyst used is small, the chlorination reaction does not proceed completely and the reaction time is delayed, resulting in low CMBA recovery.

The chlorinating agent used for the chlorination reaction includes Cl ₂ , POCl ₃ , SOCl ₂ , or SO ₂ Cl ₂ , and the amount of the chlorinating agent used is 1.0-1.8 equivalents, preferably 1.0-1.3 equivalents to 1 equivalent of p-TA. It is good to be. When the amount of the chlorinating agent is low, the conversion rate of CMBA is low, and when the amount of the chlorinating agent is high, by-products such as Di-CMBA and Tri-CMBA increase.

After the chlorination reaction is completed, it is cooled to 5 ~ 10 ℃ to filter the solid CMBA, repurified with an organic solvent, for example, chlorobenzene to separate high purity CMBA. Meanwhile, the solvent is distilled from the filtrate to recover the organic solvent and discard the residue.

Meanwhile, p-TA and a small amount of BA mixture produced by concentrating the solvent from the mixture containing BA by weight of the filtrate layer of Scheme 6 above 85 wt% as shown in Scheme 8 were filtered through a solid, and concentrated from the remaining filtrate. High purity BA is filtered and dried.

[Reaction Scheme 8]

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, but the present invention is not limited to the following Examples.

[Example 1]

1. Preparation of Mixed Acid from DMT By-Products [Scheme 4]

Mount a reflux condenser, thermometer, and stirrer in a 3L four-necked flask. 450 g of a raw material mixed with 45.0 wt% of MBZ, 42.6 wt% of MPT, 4.2 wt% of OX, and 6.8 wt% of DMT was added and stirred, and 1238 g of 20% NaOH aqueous solution was gradually added thereto, followed by heating to maintain 80 to 90 ° C. for 8 hours. To complete the hydrolysis. After cooling to room temperature (25 ° C.), it is allowed to stand for about 2 hours to separate the organic layer on oil and discard 20 g of the separated organic matter.

The separated water layer was cooled with cooling water to maintain room temperature, and while stirring vigorously, 625 g of 35% HCl aqueous solution was slowly added to adjust the pH to 2 to precipitate a mixed acid. After adjusting the pH, the mixed acid is completely precipitated with stirring for about 30 minutes, washed with filtration and dried at about 60 ° C for about 3 hours. 348 g of mixed acid were obtained. At this time, the composition ratio of each component was measured by chromatography, and it was 45.1 weight% of BA, 43.2 weight% of p-TA, and 9.8 weight% of TPA.

2. Separation of TPA from Mixed Acid (p-TA: BA = 1: 1) [Scheme 5]

Into 100 g of the mixed acid thus obtained (45.1 wt% BA, 43.2 wt% p-TA, 9.8 wt% TPA) was added 800 mL of MeOH. It heats up stirring and dissolves for about 30 minutes, maintaining about 60 degreeC. While cooling with cooling water, 400 ml of water is slowly added thereto while maintaining room temperature (about 25 ° C) to precipitate insoluble matters. The precipitated insolubles were filtered off and washed with 20 ml of a MeOH: water = 2: 1 solution. 10 g of insoluble TPA (purity 95.5%) was recovered.

Thereafter, the filtrate was concentrated under reduced pressure while maintaining the filtrate at about 50 ° C to completely recover MeOH, and cooled, and the precipitated mixed acid was filtered and dried at about 60 ° C for 3 hours. 85 g of mixed acid was obtained. At this time, the composition ratio was p.TA 48.8% by weight, BA 51.2% by weight.

3. Separation of mixed acid (p-TA: BA = 9: 1) and mixed acid (p-TA: BA = 1: 9) [Scheme 6]

Into 90 g of the mixed acid (48.8 wt% p-TA, 51.2 wt% BA) was added 800 mL of MeOH. After stirring and complete dissolution, 600 ml of water was slowly added to precipitate crystals. The precipitate is sufficiently precipitated with stirring for about 30 minutes, then filtered and dried at about 60 ° C. for about 3 hours. 37.4 g of isolated mixed acid were obtained. At this time, the composition ratio was 90.4% by weight of p-TA, 9.6% by weight BA. The composition ratio of the filtrate remaining after separating the mixed acid is BA 77.3% by weight, p-TA 21.4% by weight.

4. Preparation of CMBA from Mixed Acids (p-TA: BA = 9: 1) [Scheme 7]

A separate 500 ml four-necked flask is equipped with a reflux condenser, thermometer, stirrer and dropping funnel. 30 g of the mixed acid (90.4% by weight of p-TA and 9.6% by weight of BA) were added thereto. 60 mL of chlorobenzene was added thereto, and the temperature was raised while stirring to maintain the temperature of the contents at about 90 ° C. 1.1 g of ABC (1,1-azobis (cyclohexanecarbonitrile) (about 4 parts by weight / 100 parts by weight of p-TA) was dissolved in 60 ml of chlorobenzene, and added to a first dropping funnel, and sulfuryl chloride (SO ₂₎ 32.3 g (19.4 mL, 1.2 equiv / p-TA) of Cl ₂ were added to the second dropping funnel, and the reaction proceeded by simultaneously doping while maintaining about 90 ° C. over about 30 minutes. The reaction is aged for about 2 hours while maintaining isothermal, when the reaction is complete, it is slowly cooled down to about 5 ° C. to precipitate CMBA crystals, the crystals are filtered and washed with 20 ml of chlorobenzene cooled to about 0 ° C. It dried at about 60 degreeC for about 3 hours, and obtained 24.2 g of CMBA (composition ratio: 3.1 weight% of BA, 2.9 weight% of p-TA, 91.5 weight% of CMBA, 2.5 weight% of Di-CMBA).

24.0 g of crude CMBA thus obtained was added to 100 ml of chlorobenzene, and the mixture was warmed to about 80 ° C while completely dissolved while stirring, and then slowly cooled to about 0 ° C to precipitate crystals, filtered, and then cooled to about 0 ° C. Washed with 20 ml of chlorobenzene and dried to obtain 20.0 g of CMBA (purity 98.5%, yield 60.0%).

[Example 2]

Separation of BA from mixed acid (p-TA: BA = 1: 9) [Scheme 8]

The filtrate (composition ratio: 77.3 wt% of BA, 21.4 wt% of p-TA) was recovered under reduced pressure to recover the entire amount of MeOH, precipitated crystals, and then cooled to room temperature. The crystals were filtered to give a solid 51.1. g (composition ratio: 90.5 wt% BA, 9.5 wt% p-TA) was obtained. This solid content was added to 300 mL of MeOH to dissolve it, and 150 mL of water was gradually added thereto, and 9 g of the precipitated solid content (composition ratio: 78.3 wt% of p-TA and 21.7 wt% of BA) was collected by filtration. The remaining filtrate was concentrated under reduced pressure, MeOH was completely recovered and cooled to room temperature to obtain 40 g of precipitated BA (purity 98.5%, yield 87.1%).

[Example 3]

1. Preparation of Mixed Acids from DMT By-Products

A reflux condenser, thermometer, and stirrer were mounted on a 3 L four-necked flask, and then 200 g of a raw material mixed with 45.0 wt% of MBZ, 42.6 wt% of MPT, 4.2 wt% of OX, and 6.8 wt% of DMT was added thereto. Add and mix. 500 g of 20% NaOH aqueous solution was slowly added while stirring, and the mixture was heated to react for about 8 hours while maintaining 80 to 90 ° C to complete hydrolysis. The temperature of the reaction was lowered to 40-50 占 폚, concentrated under reduced pressure at this temperature to completely recover MeOH, cooled to room temperature (about 25 占 폚), and then 100 mL of toluene was added thereto. The organics were extracted with the toluene layer with stirring for about 1 hour, then left to stand for about 2 hours, and the toluene layer in the upper layer was discarded.

The water layer is cooled with cooling water to maintain room temperature and while slowly stirring, 260 g of 35% HCl aqueous solution is slowly added to adjust the pH to 2 to precipitate a mixed acid. After adjusting the pH, the mixed acid is completely precipitated with stirring for about 30 minutes, washed with filtration and dried at about 60 ° C for about 3 hours. 152.8 g of mixed acid were obtained. At this time, the composition ratio was 46.6 wt% BA, 41.8 wt% p-TA, 11.6 wt% TPA.

2. Separation of TPA from Mixed Acids (p-TA: BA = 1: 1)

105 g of the mixed acid thus obtained (46.6 wt% BA, 41.8 wt% p-TA, 11.6 wt% TPA) was added thereto, followed by 840 ml chlorobenzene. The mixture was heated for stirring for 1 hour while maintaining at about 60 ° C., then hot filtration to remove insolubles, followed by washing with 20 ml of chlorobenzene at room temperature and drying. 14 g of insoluble TPA (purity 93.3%) was recovered. The filtrate was concentrated under reduced pressure at about 80 ° C. to completely recover chlorobenzene, and 91 g of a residue mixed acid was obtained. At this time, the composition ratio was 46.3% by weight p-TA, 52.5% by weight BA.

3. Separation of mixed acid (p-TA: BA = 9: 1) and mixed acid (p-TA: BA = 1: 9)

90 g of the mixed acid (46.3 wt% of p-TA and 52.5 wt% of BA) was added thereto, and 700 mL of MeOH was used. After dissolution, 525 ml of water was slowly added to precipitate crystals. The precipitate is sufficiently precipitated with stirring for about 30 minutes, filtered and dried at about 60 ° C. for 3 hours. 40 g of separated mixed acid was obtained. The composition ratio was 85.1 wt% of p-TA and 14.9 wt% of BA. The composition ratio of the filtrate remaining after separating the mixed acid is 82.5% by weight BA, 15.2% by weight p-TA.

4. Preparation of CMBA from Mixed Acids (p-TA: BA = 8.5: 1.5)

A separate 500 ml four neck flask is equipped with a reflux condenser, thermometer, stirrer and dropping funnel. 50 g of the mixed acid (composition ratio: 85.1 wt% of p-TA, 14.9 wt% of BA) was added thereto, 100 ml of chlorobenzene was added, and the temperature was maintained at about 90 ° C. 1.8 g (2.4 parts by weight / 100 parts by weight of p-TA) of ABC (1,1-azobis (cyclohexanecarbonitrile)) was dissolved in 100 ml of chlorobenzene, and charged into a first dropping funnel, and 44.9 g (27 ml, of sulfuryl chloride) was added. 1.0 equivalent / p-TA) is added to the second dropping funnel After the completion of the dropping, the reaction is aged for about 2 hours while maintaining isothermal After completion of the reaction, the mixture is cooled to about 5 ° C. and the precipitated crystals are filtered out. After washing with 20 ml of chlorobenzene cooled to about 0 ° C. and drying, 20.2 g of CMBA (composition ratio: 2.3 wt% BA, 3.2 wt% p-TA, 88.9 wt% CMBA) was obtained.

20.2 g of the crude CMBA thus obtained was added to 100 ml of chlorobenzene, and the mixture was warmed to about 80 ° C while completely dissolved while stirring, and then cooled slowly to about 0 ° C to precipitate crystals, filtered, and then cooled to about 0 ° C. Washed with 20ml, and dried to give 16.5g (98.6% purity, 31% yield) CMBA.

[Example 4]

Separation of BA from Mixed Acids (p-TA: BA = 1: 1)

The filtrate (composition ratio: 82.5 wt% BA, 15.2 wt% p-TA) obtained in Example 3 3 was concentrated under reduced pressure to recover the whole amount of MeOH, precipitated crystals, cooled to room temperature, and filtered to obtain 45 g of solids. (Composition ratio: 85.5 weight% BA, 14.5 weight% p-TA) were obtained. This solid content was added to 300 mL of MeOH to dissolve it, and 150 mL of water was slowly added thereto, and 9 g (composition ratio: 72 wt% of p-TA and 28 wt% of BA) of the precipitated solid was collected by filtration. The remaining filtrate was concentrated under reduced pressure, MeOH was completely recovered and cooled to room temperature to obtain 33 g of precipitated BA (purity 98.5%, yield 69.8%).

Claims (7)

(a) NaOH aqueous solution was added to the reaction by-product of the DMT manufacturing process including methyl-p-toluate (MPT), methyl benzoate (MBZ), dimethyl terephthalate (DMT) and o-xylene (OX). Producing a sodium salt of a mixed acid comprising benzoic acid (BA), p-toluic acid (p-TA) and terephthalic acid (TPA);
(b) directly separating the organic material including OX from the reaction product obtained in step (a) by phase separation or by extracting with an aromatic solvent;
(c) separating the mixed acid of BA, p-TA, and TPA in solid phase by recovering the organic material containing OX in step (b) after adding an acid to the remaining aqueous solution, followed by recovery;
(d) adding an organic solvent selected from acetonitrile, an aqueous methanol solution and chlorobenzene to the mixed acid recovered in step (c) and separating TPA and impurities into a solid phase by filtration;
(e) separating the mixture of p-TA and BA by crystallizing the remaining filtrate after TPA and impurities are separated into the solid phase in step (d) and recovering;
(f) To the p-TA and BA mixture recovered in step (e), a solvent selected from a mixed solvent of methanol and water and acetonitrile was added and crystallized, followed by filtration to contain at least 85% by weight of p-TA. Separating the filtrates containing the mixture of the solid phase and the mixture containing at least 85% by weight of BA, and then recovering each;
(g) chlorination of the solid phase mixture containing at least 85% by weight of the p-TA obtained in step (f) to produce a mixture comprising p-chloromethylbenzoic acid (CMBA), from which the CMBA is purified and Recovering; And
(h) recovering BA by concentrating a filtrate containing a mixture containing at least 85% by weight of the BA obtained in step (f);
Method for producing p-chloromethylbenzoic acid and benzoic acid from the by-product of the dimethyl terephthalate production process comprising a. The method according to claim 1,
The reaction by-product of the DMT manufacturing process comprises 40 to 45% by weight of MPT, 43 to 48% by weight of MBZ, 5 to 8% by weight of DMT and 2 to 5% by weight of OX. The method according to claim 1,
The reaction temperature of step (a) is characterized in that the 80 ~ 90 ℃. delete The method according to claim 1,
The acid of step (c) is characterized in that the hydrochloric acid. The method according to claim 1,
The chlorination reaction in step (g) is carried out using a chlorinating agent selected from the group consisting of Cl ₂ , POCl ₃ , SOCl ₂ and SO ₂ Cl ₂ in the presence of a catalyst, the amount of the chlorinating agent being 1 equivalent to p-TA It is 1.0-1.8 equivalent with respect to the method. The method of claim 6,
The catalyst is 1,1-azobis (cyclohexanecarbonitrile), and the amount thereof is 1 to 5 parts by weight based on 100 parts by weight of p-TA.