KR20120082236A - Method for purifying high purified methyl-4-formylbenzoate from byproduct of dimethyl terephthalate preparation process - Google Patents

Abstract

PURPOSE: A method for purifying methyl-4-formylbenzoate is provided to separately manufacture methyl-4-formylbenzoate with high yield and high purity from crude methyl-4-formylbenzoate, and to able to transform to methyl-4-formylbenzoate of high purity by only simple and cheap acid treatment. CONSTITUTION: A method for purifying methyl-4-formylbenzoate comprises: a step of adding alcohol to reaction side products containing methyl formylbenzoate, manufactured from a production process of dimethyl terephthalate, and filtering the outcome; a step of transforming methyl formylbenzoate to methyl-4-formylbenzoate in a filtrate through an oximation by adding hydroxylamine or inorganic acid salt, and alkali components to the filtrate, and filtering the outcome; a step of dissolving the methyl-4-formylbezoate mixture into an organic solvent; and a step of adding acid to the mixture.

Description

[0001] The present invention relates to a process for purifying methyl 4-formyl benzoate from a by-product resulting from dimethyl terephthalate production process,

The present invention relates to a process for purifying high purity methyl-4-foemylbenzoate (MFB) from by-products generated from dimethyl terephthalate production process. More specifically, the present invention relates to a process for the preparation of methyl-4-formylbenzoate ("MFB"), dimethyl terephthalate (DMT), methyl-p-toluate The present invention relates to a method for purifying and separating pure MFB from a by-product of a DMT production process,

Dimethyl terephthalate (DMT) is a compound represented by the following formula (1) and is widely used as a raw material for polyester polymers for the production of polyester fibers, molded products and the like.

[Chemical Formula 1]

Various methods are known for the production of DMT. Typically, the Witten-Hercules process or the four-stage air oxidation process can be exemplified. This process is a method of esterifying terephthalic acid obtained by oxidizing p-xylene with methanol. Another process is known for the DMT production process of Eastman Chemical Int., Which is a process in which p-xylene is subjected to liquid air oxidation using a bromine-based catalyst in an acetic acid solvent, which is a reaction medium, Terephthalic acid, which is esterified with methanol to produce DMT.

In a typical DMT production process, by-products are produced, such as unreacted products or reaction intermediates, since the reaction of each step is not 100% completed. At this time, since the reaction by-products generated act as a polymerization terminator in the production of polyester, a purification step for increasing the purity of DMT in the DMT production process is essential.

Examples of reaction by-products generated in the production of DMT include methyl benzoate, methylbenzoate, methyl-p-toluate (MPT), methyl-4-methylbenzoate -formylbenzoate, MFB), and it is also referred to as a crude MFB since it typically contains a large amount of MFB components. However, these reaction byproducts are mainly used for disposal because the utilization method is not sufficient.

(2)

(3)

[Chemical Formula 4]

On the other hand, methyl 4-hydroxyiminobenzoate is a major raw material for the production of 4- (aminomethyl) benzoic acid and 4- (aminomethyl) cyclohexanecarboxylic acid which are used as fiber modifiers, starting materials for polymers and medicinal intermediates In recent years, there has been an increasing demand as an intermediate of various new drugs.

Japanese Patent Application Laid-open No. 50-71614, Russian Patent No. 1268563 and Russian Patent No. 1244140 disclose the conversion of methyl 4-formylbenzoate contained in the reaction by-product generated in the production process of dimethyl terephthalate to a sulfite adduct And then recovering methyl 4-formylbenzoate through hydrolysis under acidic or alkaline conditions. However, since the purity of the sulfurous acid adduct of methyl 4-formylbenzoate, which is a production intermediate, is low, the above-mentioned method causes an increase in cost due to purification of the intermediate material in order to obtain methyl 4-formylbenzoate of high purity.

Furthermore, in order to recover methyl 4-formylbenzoate, the sulfite adduct of methyl 4-formylbenzoate, which is a reaction intermediate, must be hydrolyzed under acidic or alkaline conditions. In acid hydrolysis, a large amount of sulfur dioxide, And a large amount of inorganic sulfurous acid salt wastewater is generated at the time of alkali hydrolysis, thereby causing environmental pollution problem. In addition, since the yield of hydrolysis is low, a large amount of the separation filtrate is discharged into waste water having a high organic matter content, which is problematic in its effectiveness.

Korean Patent Publication Nos. 1995-0005193 and Korean Patent No. 0124964 disclose a process for producing 4-formylbenzoic acid from reaction by-products generated in a DMT production process. All of these processes are carried out at high temperature in a strong acid aqueous solution, It is difficult to industrialize due to the generation of high concentration organic acid wastewater and a large amount of sulfur dioxide which is a toxic gas. Also, since sulfurous acid gas is generated frequently and the solvent is used excessively, economical efficiency is also insufficient.

The above methods are suitable for recovering DMT and MFB contained in DMT by-products, but there are problems such as reprocessing of used catalyst and solvent, The cost is not economical. It is not easy to separate and purify only MFB in ordinary DMT by-products. This is because impurities such as DMT, MBZ, and MPT are similar in physical properties to MFB.

Accordingly, there is a need for a method for producing a MFB of higher purity from the by-product efficiently, inexpensively, and in comparison with a conventionally known method.

According to the embodiment of the present invention, it is intended to provide a method for converting MFB to MHB in the by-products from the reaction by-products generated in the DMT production process and purifying and separating the by-products into MFB of higher purity. Specifically, the aldehyde group of the MFB is converted into an adduct form through chemical reaction such as an alkoxy or sulfur adduct to separate it from impurities such as DMT, MBZ and MPT. More specifically, the MFB To an oxime form of MHB using an aldehyde group, and purifying the MFB by converting it into an MFB, thereby providing a high-purity MFB.

According to one embodiment of the present invention,

(a) adding an alcohol to a reaction by-product produced in the course of the production of DMT and containing methyl formyl benzoate and filtering the alcohol;

(b) adding an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkali component to the filtrate after (i) adding the filtrate to the filtrate to precipitate the methyl formylbenzoate in the filtrate through oxydation to methyl 4-hydroxyiminobenzoate And filtering it;

(c) dissolving the resulting methyl 4-hydroxyiminobenzoate mixture in toluene or methylene chloride; And

(d) adding an acid to the mixture to purify and separate the methyl formyl benzoate at higher purity.

The features and advantages of the present invention will become more apparent from the following detailed description.

Prior to that, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may properly define the concept of the term in order to best explain its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

In the method for purifying MFB according to an embodiment of the present invention, MHB is produced by oxidizing the MFB in the filtrate by adding an inorganic acid salt of hydroxyamine or hydroxyamine to the crude MFB among reaction by-products generated in the DMT production process From this, it is possible to provide MFB with high purity through simple and economical work-up process using toluene or methylene chloride and acid. More specifically, crude MFB can be separated and produced in high yield and high purity, and it is advantageous that high-purity MFB conversion can be performed simply by cheap acid treatment. Also, if necessary, the advantage of reusing hydroxyamine or its salt in the manufacturing process can be provided.

The embodiments provided in accordance with the present invention can be all achieved by the following description. It is to be understood that the following description is of a preferred embodiment of the present invention and that the present invention is not necessarily limited thereto.

Prior to that, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may properly define the concept of the term in order to best explain its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Typical DMT production processes involve oxidation and ester reactions sequentially with p-xylene as a starting material. For example, p-xylene is oxidized in liquid phase with terephthalic acid (or its intermediate p-formylbenzoic acid) (DMT, MBZ, MPT, etc.) in the presence of a large amount of MFB and a small amount of other components (for example, DMT, MBZ, MPT, etc.) And is referred to as crude MFB.

The composition of such reaction byproducts may vary depending on the DMT preparation process, but typically ranges from about 60 to 90 wt% MFB, from about 5 to about 30 wt% DMT, from about 1 to about 8 wt% MPT, and from about 0.1 to about 3 MBZ % ≪ / RTI > by weight. The above composition is provided for illustrative purposes, and the present invention is not necessarily limited thereto.

According to one embodiment of the present invention, the alcohol is added to the reaction by-product of the DMT production process. Due to the difference in solubility of the components in the reaction by-product to the alcohol, DMT is converted into a solid (solid) Is still in a dissolved state. Therefore, when the solid component and the filtrate are separated by using a filtration process, a filtrate containing solid components rich in DMT component and MFB and the like can be obtained, respectively.

Meanwhile, according to a preferred embodiment, it may be preferable to perform stirring after addition of an alcohol component in order to increase the separation efficiency. Alternatively, an alcohol component may be added under stirring of the byproduct.

Examples of the alcohols to be added to the reaction by-products in the embodiment of the present invention include C ₁ to C ₁₀ aliphatic alcohols. Specific examples thereof include methanol, ethanol, propanol, isopropanol, butanol, More specifically, methanol may be used. The above-listed alcohols are exemplarily described, and the present invention is not necessarily limited thereto.

In an exemplary embodiment, the amount of alcohol added may range from about 0.2 to 5.0 ml / g, more specifically from about 0.5 to 2.0 ml / g, per gram, based on the reaction by-product (or crude MFB). In this regard, when the alcohol is not added in a sufficient amount or the alcohol is used in an excessively large amount, the DMT content in the filtrate increases with the increase of DMT which is not solidified, It can cause problems. However, the above numerical ranges are illustrative, and the present invention is not necessarily limited thereto.

On the other hand, the temperature of the byproduct to which the alcohol is added can be adjusted to, for example, from about -5 ° C to 120 ° C, specifically about 3 ° C to 50 ° C, so that DMT can be recovered in high purity and high yield in the subsequent filtration step have. This suggests that as the temperature increases, the amount of DMT dissolved in the alcohol increases, which may lower the recovery rate of DMT.

In order to increase the purity or recovery rate of recovered DMT or increase the content of MFB among the by-product components present in the filtrate, an efficient filtration method is important. Vacuum filtration, pressure filtration, centrifugal separation, Press method and the like. The most effective filtration method may be a pressurization filtration method wherein the pressure is, for example, about 0.5 to about 3 kg / cm ² , specifically about 0.5 to about 1.5 kg / cm ² Lt; / RTI >

According to an exemplary embodiment of the present invention, the step of washing the solids obtained through the filtration step, for example, one or two or more washing steps, may be additionally performed in order to further increase the purity of the recovered DMT. As a usable washing component, it may be preferable to use a kind of solvent capable of dissolving and removing other components (for example, MFB, etc.) while maintaining the amount of DMT in the solid content to the maximum. Representative examples of the alcohol component have. This is because, when a soluble component for DMT is used, the recovery rate of DMT may be lowered. Accordingly, it may be desirable to select the alcohols (e.g., C ₁ to C ₁₀ aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, butanol, mixtures thereof, etc.) that can be used in the alcohol addition step described above.

When the alcohol is used as the cleaning solvent, the amount of the alcohol to be used may be about 0.1 to about 5 times, more specifically about 0.5 to about 1.0 times the amount of the alcohol added in the previous step (based on the volume). This considers that when a large amount of alcohol is used as the washing component, the purity of DMT in the solid content may increase but the recovery rate may be lowered due to the small amount of DMT dissolved in the alcohol.

However, since the recovery rate may be lowered as the washing step is repeated, it may be preferable to suitably adjust the DMT purity in the required solid content.

According to the embodiment of the present invention, the filtrate obtained through the filtration process can be utilized in the production of MHB. Since the majority of the DMT components in the reaction by-products are separated through the above-mentioned filtration process, Is relatively increased, so that MHB having a higher purity can be produced in a subsequent process.

According to an exemplary embodiment of the present invention, an alcohol may be further added to the filtrate in order to improve efficient stirring and reactivity with the oxime. As the alcohol to be added, for example, the C ₁ to C ₁₀ aliphatic alcohol, Specifically, methanol, ethanol, propanol, isopropanol, butanol, a mixture thereof or water can be used. At this time, alcohol may be added and the temperature may be raised to a temperature of about 40 ° C to 70 ° C to dissolve a part of the remaining solid in the filtrate, and the heating may be terminated after the solid content is completely dissolved.

According to the embodiment of the present invention, the MFB in the filtrate is subjected to oxydation reaction by adding (i) an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkali component to the filtrate (or the filtrate to which the alcohol is added) MHB < / RTI >

The inorganic acid salt of hydroxyamine or hydroxyamine used in the oximation reaction may be a hydrochloride, sulfate, nitrate or phosphate of hydroxyamine. More specifically, a 50% aqueous solution of hydroxyamine or a solution of hydroxyamine Hydrochloride or sulfate can be used. It is preferable that the inorganic acid salt of the hydroxyamine or hydroxyamine is used in an amount of at least about 0.5 equivalent, specifically about 1.0 to 2.0 equivalent, based on the MFB in the filtrate. Although the present invention is not limited to the specific amount of the inorganic acid salt of the hydroxyamine or hydroxyamine, when the amount is too small, it may be inefficient due to the low degree of oxigenization reaction. On the other hand, , Although the reaction rate is fast, the yield of the target MHB may be lowered due to generation of a side reaction or the like, and therefore, it may be preferable to use it within the above-mentioned range.

According to a preferred embodiment, the oxalization reaction can be carried out under stirring, specifically, an inorganic acid salt of hydroxyamine or hydroxyamine may be added with stirring or simultaneously with stirring. At this time, it is more preferable that the inorganic acid salt of hydroxyamine or hydroxyamine is added in a dropwise addition manner.

According to an exemplary embodiment, an oxalization reaction can be performed by adding an alkali component after the addition of the aforementioned inorganic acid salt of hydroxyamine or hydroxyamine. Such an alkali component may be preferably added in the form of an aqueous solution. As examples of the _{alkali, NaOH, Ca (OH) 2} , KOH, Na 2 CO 3, K 2 CO 3, NaHCO 3, CH 3 COONa, KNO 3 , And more specifically, sodium hydroxide may be used. The alkali aqueous solutions listed above are exemplarily described, and the present invention is not necessarily limited thereto.

 According to a preferred embodiment, an oxalization reaction can be carried out by adding an alkali component to adjust the pH of the reactant (or reaction liquid) to a range from about 7.0 to about 9.0, specifically from about 7.8 to about 8.2, When the pH is too low, there is a problem that the yield is lowered due to the loss of the MHB. On the other hand, when the pH is too high, the side reaction is increased, and the present invention is not necessarily limited to the above numerical range.

Also, the oxeping reaction may be carried out at a temperature in the range of about 15 ° C to 50 ° C, specifically about 25 ° C to 35 ° C, taking into consideration the reaction rate, the purity of the desired MHB, and the economy.

When the oxocation reaction is complete, it can be filtered to obtain MHB. In order to obtain a high yield of MHB, an efficient filtration method is important. Examples of usable filtration methods include vacuum filtration, pressure filtration, centrifugal separation, non-filtration, and filter pressing. , Where the pressure may range, for example, from about 0.5 to about 3 kg / cm ² , specifically from about 0.5 to about 1.5 kg / cm ² .

 According to an exemplary embodiment of the present invention, when the oxepi fi cation reaction is terminated, the oxycodone form of the MHB mixture is dissolved in an organic solvent. The amount of the solvent to be added is preferably 3 ml to 4 ml based on 1.0 g of MHB. When the added amount is too large, there is a problem in economical efficiency. When the added amount is too small, stirring is difficult.

However, the MHB mixture did not react with most of the solvents such as acetone, tetrahydrofuran (THF), acetonitrile, methanol, ethanol and the like.

The organic solvent may be at least one of toluene series such as benzene, xylene and toluene, and methylene chloride series such as methylene chloride, chloroform and carbon tetrachloride. More specifically, toluene or methylene chloride may be used Lt; / RTI >

According to an exemplary embodiment of the present invention, an acid is added after being dissolved in the organic solvent, wherein the acid is preferably sulfuric acid or hydrochloric acid, wherein the amount of acid added is preferably 2 equivalents to 3 equivalents based on the number of moles of MHB can do.

Further, the reaction time after the addition of the acid is preferably 1 hour to 2 hours. When the reaction time exceeds 2 hours, there is a problem that the reaction progresses to a side reaction. When the reaction time is less than 1 hour, the progress of the reaction is not completed.

According to one exemplary embodiment of the present invention, after the reaction is terminated by adding an acid as described above and heating and refluxing, the terminated reactant is filtered through one of the above-mentioned methods, Can be cleaned. Further, after separating the filtered liquid layer, the organic solvent layer can be washed with water at least once, and after the distillation under reduced pressure, it is dried by a usual drying method to obtain a solid MFB. Here, since the water layer contains an inorganic acid salt of hydroxyamine or hydroxyamine, it can be recycled to the MHB manufacturing process.

According to an exemplary embodiment, the recycle may be recycled by itself, and in some cases, when excess water is used, the reaction rate is slowed down. Therefore, have.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following embodiments are provided to further understand the present invention, and the present invention is not intended to be limited thereto.

In an embodiment of the present invention, a crude MFB from the DMT manufacturing process was used that contained about 75-79% MFB, about 8.0-12.0% DMT, and about 5.0-7.0% MPT .

DMT  Recovery process

Example 1

198 kg of crude MFB was added to a 1,000 L G / L reactor, and 100 L of methanol (0.5 ml per gram of crude MFB) was added, followed by stirring at 500 rpm for about 1 hour. After the stirring was completed, the mixture was filtered using a Nutsche filter at room temperature, and washed with 100 L of methanol to obtain a solid content of 24 kg.

The obtained solid content and filtrate were analyzed by HPLC. The DMT, MFB and MPT contents were 92.0%, 7.2% and 0.8%, respectively, and the recovery rate of DMT was 92%. The DMT, MFB and MPT contents of the filtrate were 10.6%, 85.5% and 3.9%, respectively.

MHB  Manufacture process

Example 2

MFB of 302.1 kg was obtained from the filtrate obtained by recovering DMT in Example 1 above. 80 L of methanol was further added to the filtrate. After the temperature of the filtrate was raised to about 40 ° C., the solid was completely dissolved in the filtrate, followed by heat off. Thereafter, 72.0 kg of hydroxylamine-HCl dissolved in 11 L of water was added dropwise with stirring at 500 rpm for about 6 hours. At this time, half of the amount of the hydroxylamine-hydrochloric acid aqueous solution was added dropwise for about 3 hours, and when the solid started to be formed, the rest was then added dropwise for about one and a half hours. It was then stirred for 1 hour. To this was added 80.4 L of 50% aqueous sodium hydroxide solution, resulting in a pH of about 7.8. The methanol was distilled under reduced pressure to recover methanol. Recovery of alcohol in the above process is necessary to increase the yield of MHB, but when the product is distilled at a too high temperature during recovery, the solid color becomes darker. It was then filtered and washed with 40 L of water. The precipitated solid was dried at 60 DEG C for 8 hours to obtain a solid portion of MHB. The purity of the obtained MHB was 87%.

370 L of toluene was added to the obtained MHB, and the mixture was refluxed. When the solid was completely dissolved, it was gradually cooled after heat off. After filtration at about 40 DEG C, it was washed with 190 L of toluene. The added toluene was recovered by vacuum distillation at 480 L, and the solid was dried to obtain 90% of purified MHB having a purity of 99.9%.

remind MHB Higher purity To MFB  refine

Example 3

The mixture of oxydation type MHB (296.8 g, 1.66 mol) obtained above was dissolved in toluene (890 mL), sulfuric acid (176.6 mL, 3.3 mol) was added and the mixture was refluxed for 2 hours. The reaction was terminated, then the reaction was filtered and washed twice with 594 mL of toluene. After separating the filtrated liquid layer, the toluene layer was washed twice with 594 mL of water, and then the toluene layer was distilled off under reduced pressure, followed by drying to obtain 218.7 g of MFB, the yield being 80% and the purity being 95% .

Example 4

The mixture of oxydation type MHB (296.8 g, 1.66 mol) obtained above was dissolved in 890 mL of methylene chloride, then sulfuric acid (176.6 mL, 3.3 mol) was added and the mixture was refluxed for 2 hours. Wait until the reaction is complete, then filter the reaction and wash twice with 594 mL of methylene chloride. The filtrated liquid layer was separated, and the methylene chloride layer was washed twice with 594 mL of water. The methylene chloride layer was distilled under reduced pressure and then dried to obtain 218.7 g of MFB, the yield of which was 80%, the purity was 94 %.

Example 5

MHB (296.8 g, 1.66 mol) in the form of the oxydation obtained above was dissolved in 890 mL of toluene, and then hydrochloric acid (219.4 mL, 4.97 mol) was added thereto, followed by heating under reflux for 2 hours. The reaction was terminated, then the reaction was filtered and washed twice with 594 mL of toluene. The filtrated liquid layer was separated, and the toluene layer was washed twice with 594 mL of water. The toluene layer was distilled under reduced pressure, and then dried to obtain 244.7 g of MFB. The yield was 90% and the purity was 99% . Here, since the water layer contains hydroxylamine · HCl, it can be used again in the MHB manufacturing process.

Example 6

A mixture of 296.8 g (1.66 mol) of the oxydation type oxime obtained above was dissolved in 890 mL of methylene chloride, and then hydrochloric acid (219.4 mL, 4.97 mol) was added thereto, followed by heating under reflux for 2 hours. Wait until the reaction is complete, then filter the reaction and wash twice with 594 mL of methylene chloride. The filtrated liquid layer was separated, and the methylene chloride layer was washed twice with 594 mL of water. The methylene chloride layer was distilled off under reduced pressure and then dried to obtain 244.7 g of MFB, the yield of which was 90%, the purity was 99 %.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. It is therefore intended that such variations and modifications fall within the scope of the appended claims.

Claims (5)

(a) adding an alcohol to a reaction by-product produced in the course of the production of DMT and containing methyl formyl benzoate and filtering the alcohol;
(b) adding an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkali component to the filtrate after (i) adding the filtrate to the filtrate to precipitate the methyl formylbenzoate in the filtrate through oxydation to methyl 4-hydroxyiminobenzoate And filtering it;
(c) dissolving the resulting methyl 4-hydroxyiminobenzoate mixture in an organic solvent; And
(d) adding an acid to said mixture. The method according to claim 1,
Wherein the acid is sulfuric acid or hydrochloric acid. The method according to claim 1,
Wherein the organic solvent is one or more selected from the group consisting of benzene, xylene, toluene, methylene chloride, chloroform, and carbon tetrachloride. The method according to claim 1,
Further comprising the step of filtering the reaction product in the step (d), and recycling the inorganic acid salt of hydroxylamine or hydroxyamine contained in the water layer after removing water or water itself. The method according to claim 1,
Wherein the reaction time after adding the acid is from 1 hour to 2 hours.