KR101778617B1 - Method for Producing Methyl-4-hydroxyiminomethylbenzoate - Google Patents

Abstract

The present invention relates to a process for preparing MHB from a by-product generated in a DMT production process, comprising the steps of: (a) adding alcohol to a reaction by-product produced during the production of DMT and containing methylformyl benzoate, b) The filtrate after the filtration is subjected to an oximation reaction by adding (i) an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkali component, and methylformylbenzoate in the filtrate is reacted with methyl 4-hydroxyiminomethylbenzoate And (c) purifying from the converted methyl 4-hydroxyiminomethylbenzoate. ≪ Desc / Clms Page number 5 >

Description

METHOD FOR PRODUCING Methyl-4-hydroxyiminomethylbenzoate < RTI ID = 0.0 >

The present invention relates to a process for preparing methyl-4-hydroxyiminomethylbenzoate (MHB) from a by-product resulting 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 ) And the like. The present invention relates to a process for preparing and separating MHB 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-hydroxyiminomethylbenzoate is a major raw material for the production of 4- (aminomethyl) benzoic acid and 4- (aminomethyl) cyclohexanecarboxylic acid, which are used as fiber modifiers, And recently, there is an increasing demand as an intermediate of various new medicines.

In Japanese Patent Laid-Open Nos. 50-71614, 1268563 and 1244140, methyl 4-formylbenzoate contained in reaction by-products generated in the production process of dimethyl terephthalate is converted into a sulfite adduct and separated , Refining it, and then recovering methyl 4-formylbenzoate through hydrolysis under acid or alkaline conditions. However, since the purity of the sulfite 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 the acid hydrolysis, a large amount of sulfur dioxide , A large amount of inorganic sulfurous acid waste water may be generated at the time of alkali hydrolysis, thereby causing environmental pollution problems. 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, , There are problems in industrialization due to generation of high concentration organic acid wastewater and a large amount of sulfur dioxide which is a toxic gas.

As described above, the recycling method of the reaction by-products in the DMT manufacturing process has a problem in that it is inexpensive in terms of environment and cost.

Accordingly, there is a demand for a method for producing high purity MHB from the by-products at low cost and in a simpler manner than the conventional methods.

A specific example of the present invention is to provide a method for preparing, purifying or separating MHB of high purity from reaction by-products generated in a DMT production process.

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; And

(b) adding to the filtrate after filtration (i) an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkaline component and adding oxylating reaction to convert the methyl formylbenzoate in the filtrate into methyl 4-hydroxyiminomethylbenzo Lt; / RTI > And

and (c) purifying the resulting methyl 4-hydroxyiminomethylbenzoate mixture. The present invention also provides a process for preparing and separating methyl 4-hydroxyiminomethylbenzoate.

In the above-mentioned specific examples, the methylformyl benzoate-containing by-product is at least one selected from the group consisting of methyl formyl benzoate (MFB), dimethyl terephthalate (DMT), methyl benzoate (MBZ), and methyl-para- .

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 producing MHB according to the embodiment of the present invention, the alcohol is added to the crude MFB among the reaction by-products generated in the DMT production process, and the solubility of the reaction by-products in the DMT and other by-product components (for example, MFB) The DMT contained in the reaction by-product can be recovered at a high purity of at least 90% by a simple process such as filtration after the addition of alcohol. Further, the filtrate is added with an inorganic acid salt of hydroxyamine or hydroxyamine And the MHB is produced by oxidizing the MFB in the filtrate, thereby providing a merit that a high-purity MHB can be produced through a simple and economical work-up process. Furthermore, DMT and MHB of higher purity can be provided by a simple purification process as needed.

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 aliphatic alcohols of C ₁ to C ₁₀ , and specific examples thereof include methanol, ethanol, propanol, isopropanol, butanol, And more specifically, methanol can 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 of 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 alcohol-added by-product can be adjusted to, for example, about -5 to 120 ° C, specifically about 3 to 50 ° C, so that the DMT can be recovered in high purity and high yield in the subsequent filtration step. 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 may be exemplified. At this time, the efficient filtering method may be pressurized filtration, 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 to 70 ° C to dissolve a part of the remaining solid in the filtrate. After the solid content is completely dissolved, the heating may be terminated.

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 can be carried out at a temperature of about 15 to 50 ° C, specifically about 25 to 35 ° C, taking into consideration the reaction rate, the purity of the desired MHB, and the economical efficiency.

 According to an exemplary embodiment, when the oxepitization reaction is terminated, the reaction product may be filtered, washed with water and dried to recover the solid MHB to obtain the desired MHB as a solid. Further, by distilling and concentrating the added alcohol and water, the MHB mixture can be separated into solid components.

Here, the amount of water used is preferably in the range of about 2 to about 20 times, more specifically about 3 to 5 times, by weight based on the MFB. If too little water is used, it will affect stirring. If too much water is used, many wastewater will be generated and it will be uneconomical. In addition, the above process may be repeated at least twice as necessary.

According to another embodiment of the present invention, it is possible to further include a purification step of washing with an organic solvent to further increase the purity of the target MHB. More specifically, the organic solvent and the solid MHB are added, refluxed, heat-off, and then washed with the organic solvent. As the usable cleaning component, it may be preferable to use a kind of solvent capable of dissolving and removing the other components while maintaining the maximum MHB content in the solid content. For example, there may be toluene, xylene, Can be exemplified as the toluene component.

The added organic solvent may be, for example, about 1.5 L per kg of MHB for MHB, and specifically about 3.0 to 5.0 L, and more specifically about 1.0 to 2.0 L.

According to exemplary embodiments of the present invention, the washing process may be performed once or twice with an organic solvent to further increase the purity of the obtained MHB. However, since the recovery rate may be lowered as the washing process is repeated, it may be preferable to appropriately adjust the purity according to the purity of the MHB in the required solid content.

In the above embodiment, when the washing step is completed in each of the above-mentioned cases, the organic solvent used for the washing may be further recovered. The recovery method may include distillation, for example, May be used. In addition, methods known in the art may be adopted for solvent recovery.

According to embodiments of the present invention, purified MHB as described above can be dried at about 80 to about 100 < 0 > C to yield in the form of a solid. Conventional drying methods or apparatuses known in the art can be used for this purpose.

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 facilitate understanding of the present invention and are not intended to limit the present invention.

In an embodiment of the present invention, a reaction by-product (crude MFB) originating from the DMT production process and containing about 75-79% MFB, about 8.0-12.0% DMT and about 5.0-7.0% MPT was used .

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 DMT recovery rate was 92%. The DMT, MFB and MPT contents of the filtrate were 10.6%, 85.5% and 3.9%, respectively.

The components and contents used in Examples 2 and 3 and Comparative Example 1 are shown in Table 1 below.

input
(crude MFB) Addition amount / washing amount
(Methanol) reaction
Temperature The recovered -DMT (w / c) Filtrate DMT MFB MPT MFB DMT MPT Example 2 50g 100ml / 30ml
(2 ml / g) Room temperature 3g (recovery rate 50%) 40g 95.4% 4.3% 0.3% 87.3% 10.0% 2.7% Example 3 50g 75ml / 30ml
(1.5 ml / g) Ice
Water
Bath 5.9 g (recovery rate 98%) 42g 91.9% 8.1% - 87.0% 7.9% 5.1% Comparative Example 1 50g 75ml / 30ml
(1.5 ml / g) Low temperature 4g (recovery rate 67%) 40g 95.6% 4.2% 0.2% 84.4% 10.1% 5.5%

c-MFB Composition: MFB 79.3%, DMT 12.0%, MPT 6.2%

Examples 2 and 3 were the same as those of Example 1 except that only the feed amount of crude MFB, the amount of methanol added, the amount of washing, and the reaction temperature were different. Comparative Example 1 was the same as that of Example 1, and the solvent used in the purification was toluene instead of methanol.

As can be seen from the above table, the purity of DMT in Example 2 is higher than that of Example 3, but the yield is lower. In Example 3 where the temperature is relatively lower, the purity of DMT is 91.0% And recovery rate of 95.0% or more is most preferable, but it can be used in consideration of energy efficiency according to lowering of reaction temperature and efficiency of working volume. However, in Comparative Example 1, toluene, which is an expensive solvent, is used as a solvent for recovering DMT, which is not suitable as a solvent because of the problem that distillation time and distillation energy cost are large in solvent recovery. 3, the purity and the recovery rate are not remarkably excellent.

MHB  Manufacture process

Example 4

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. Then, 72.0 kg of a hydroxylamine-HCl aqueous solution 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. 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%.

The components and contents used in Examples 5 to 7 and Comparative Example 2 are shown in Table 2 below.

Crude-
MFB
(kg) Added
Methanol
(L)
Filtrate MFB (kg) Additional used methanol
(L) Methanol
distillation
The presence or absence Filtered
MHB (kg) The obtained MHB (kg) yield
(%) water
(%) Example 5 5 5.0 4.15 2.0 U 4.57 3.34 86.6 99.5 Example 6 3 3.0 2.50 4.5 U 2.75 1.69 73.0 99.4 Example 7 5 5.0 4.15 2.0 U 4.34 3.00 77.9 99.3 Comparative Example 2 4 4.0 3.32 4.0 radish 2.60 1.99 64.6 99.4

Examples 5 to 7 and Comparative Example 2 were carried out in the same manner as in Example 4, except that the amount of c-MFB, the amount of methanol (L) at the purification and the amount of methanol (L) But the addition of 2.0 L, which was additionally used in Example 7, was carried out using water rather than methanol.

The above experiment was conducted to confirm the effect of the MHB reaction because the recovery of MHB is lowered unless the methanol is distilled and concentrated after the MHB reaction process. As can be seen from the above results, it was found that the yield was the lowest when methanol was not distilled as in Comparative Example 2.

The yield of Example 5 was lower than that of Example 4, which is because the volume yield was reduced, and Example 4 is more economical than Example 5.

In Comparative Example 2, although the stirring was relatively good, the color of the MHB gradually increased in the distillation process, and the color of the MHB was not removed even after the purification process, and the yield was also lower than that of Example 4.

In Example 7, water, which is not methanol, was added. The yield was lower than that of Example 4 because stirring was not performed smoothly as compared with the case of using methanol.

The components, content, and yields used in Example 8 and Comparative Example 3 are shown in Table 3 below.

Crude MHB Toluene (g) MHB (G) Purity (%) Yield (g) Yield (%) Purity (%) Example 8 45.7 85 100 33.4 87 99.5 Comparative Example 3 45.7 85 130 25.7 67.0 91.0

In Example 8, toluene was used as a solvent for purifying c-MHB. In Comparative Example 3, MeOH / H ₂ O = 1/1 solution, which is not toluene, was used.

The yield and purity of Example 8 was higher than that of Comparative Example 3, and toluene was excellent as a refining solvent.

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 (7)

(a) adding an alcohol to a reaction by-product produced in the process of producing dimethyl terephthalate (DMT) and filtering the alcohol;
(b) adding a solution of (i) an inorganic acid salt of hydroxyamine or hydroxyamine and (ii) an alkali component to the filtrate after the filtration, and allowing the methyl formylbenzoate in the filtrate to react with methyl 4-hydroxyiminomethylbenzo And recovering dimethyl terephthalate as a solid after filtration; And
(c) purifying the resulting methyl 4-hydroxyiminomethylbenzoate mixture, and a process for producing methyl 4-hydroxyiminomethylbenzoate. delete The method according to claim 1,
Further comprising washing the recovered dimethyl terephthalate once or more with alcohol to further purify the recovered dimethyl terephthalate. The method according to claim 1 or 3,
Wherein the alcohol is an alcohol having a carbon number of C ₁ to C ₁₀ . The method according to claim 1,
Further comprising separating the methyl 4-hydroxyiminomethylbenzoate mixture into a solid fraction by distillation and concentration of the added alcohol and water. The method according to claim 1,
Wherein said purifying step further comprises purifying using an organic solvent. The method according to claim 1,
Further comprising separating the purified methyl 4-hydroxyiminomethylbenzoate mixture into a solid.