WO2011046307A2

WO2011046307A2 - Oxidation reactor for manufacturing aromatic carboxylic acid and method of manufacturing aromatic carboxylic acid using the same

Info

Publication number: WO2011046307A2
Application number: PCT/KR2010/006619
Authority: WO
Inventors: Hyungjin Kim; Han San Kim; Sung Wo Chai
Original assignee: Sam Nam Petrochemical Co., Ltd.
Priority date: 2009-10-16
Filing date: 2010-09-29
Publication date: 2011-04-21
Also published as: WO2011046307A3; TWI410402B; KR101159409B1; TW201119993A; KR20110041803A

Abstract

Disclosed are an oxidation reactor for manufacturing an aromatic carboxylic acid and a method of manufacturing the aromatic carboxylic acid using the oxidation reactor. The oxidation reactor includes a reaction chamber, a stirring shaft disposed along a geometric vertical axis of the reaction chamber, and at least two stirrers, each including stirring blades, each stirring blade having either a curved portion or a bent portion formed on an end of the stirring blade to enable fluid to flow in the reaction chamber while preventing the fluid from remaining in the reaction chamber, and each stirring blade being extended radially along a direction perpendicular to the vertical axis to be rotated.

Description

OXIDATION REACTOR FOR MANUFACTURING AROMATIC CARBOXYLIC ACID AND METHOD OF MANUFACTURING AROMATIC CARBOXYLIC ACID USING THE SAME

The present invention relates to a chemical reactor and a reaction method, and more particularly, to an oxidation reactor for manufacturing an aromatic carboxylic acid, which may maximize reaction efficiency and reaction purity, and to a method of manufacturing the aromatic carboxylic acid by using the oxidation reactor, which may produce the aromatic carboxylic acid with high efficiency and high yield.

Aromatic carboxylic acid may be a compound being useful as a variety of basic chemical compounds. For example, terephthalic acid (TA), that is, a representative aromatic carboxylic acid may be used as polyester raw materials for items such as fibers, films, plastic bottles, resins for a container, and the like, and a demand for TA has been recently increasing. As a general method of manufacturing the aromatic carboxylic acid, a method of oxidation at liquid-phase has been well-known. The liquid-phase oxidation may be performed such that a heavy metal compound such as cobalt, manganese, etc., and a bromine compound, may be used as a catalyst as necessary, and an aromatic alkyl compound within a reactor from among a low-level aliphatic carboxylic acid-containing solvent such as an actic acid, and the like is brought into contact with an oxygen-containing gas in a pressurized state.

In the above described method of manufacturing the aromatic carboxylic acid, the aromatic alkyl compound of a raw material and a mixture of the acetc acid and the catalyst are put in the reactor including a stirrer formed therein, and are consecutively subjected to an oxidation reaction by introducing an oxygen-containing gas into the reactor, thereby obtaining the aromatic carboxylic acid having a relatively low solubility. Next, the aromatic carboxylic acid having the relatively low solubility is continuously generated to obtain a crude aromatic carboxylic acid. Next, the crude aromatic carboxylic acid is consecutively separated and subjected to a refining process to thereby generate a high-purity aromatic carboxylic acid.

With respect to a method of manufacturing the aromatic carboxylic acid using a difference between a reaction method and reaction scheme for the liquid-phase oxidation reaction of the alkyl aromatic carboxylic acid using oxygen, there are many proposed improved techniques. Of these, as for TA as a representative aromatic carboxylic acid, there has been a well-known method for manufacturing the TA, including a separation/refining process followed by the oxidation reaction and a recycling process.

However, the above described method may still have many technical problems to be required to be overcome, as follows:

First, a significant amount of a residual non-reactive alkyl aromatic compound is generated at the time of the oxidationreaction, and the significant amount of the generated non-reactive alkyl aromatic compound is included in a discharged gas, and thereby costs for recovering the non-reactive alkyl aromatic compound may be needed.

Second, the aromatic carboxylic acid used as the polyester raw material adversely affects its quality, and thereby a significant amount of impurities, such as 4-carboxyl benzaldehyde (4-CBA) and the like generated at the time of manufacturing the aromatic carboxylic acid, may still remain.

Third, a significant loss of an aliphatic carboxylic acid used as the solvent may occur due to oxidation decomposition at the time of oxidation reaction, and thereby an economical problem may occur.

An aspect of the present invention provides an oxidation reactor for manufacturing aromatic carboxylic acid that may reduce a reaction loss, and improve reaction efficiency.

An aspect of the present invention provides a method of manufacturing a high-purity and high-efficiency aromatic carboxylic acid using the oxidation reactor.

According to an aspect of the present invention, there is provided an oxidation reactor for manufacturing aromatic carboxylic acid, the oxidation reactor including: a reaction chamber; a stirring shaft disposed along a geometric vertical axis of the reaction chamber; and at least two stirrers, each including stirring blades, each stirring blade having either a curved portion or a bent portion formed on an end of the stirring blade to enable fluid to flow in the reaction chamber while preventing the fluid from remaining in the reaction chamber, and each stirring blade being extended radially along a direction perpendicular to the vertical axis to be rotated.

In this instance, the oxidation reactor may include a first stirrer and a second stirrer being spaced apart from each other, and each being disposed on the stirring shaft of the reaction chamber, the first stirrer being disposed in an upper portion of the reaction chamber and the second stirrer being disposed in a lower portion of the reaction chamber, and a spaced distance between the first stirrer and the second stirrer may be 1 to 1.5 times a length (diameter) of either the first stirrer or the second stirrer. Also, the length (diameter) of the stirrer may be 0.4 to 0.5 times an inner diameter of the reaction chamber. Also, a distance between the second stirrer and a bottom surface of the reaction chamber may be 0.5 to 1 times the length (diameter) of the second stirrer. In this instance, location relation of the stirrers in the reaction chamber may have a great influence on reaction efficiency or reaction purity.

In addition, the stirring blade may include at least two of either the curved portion or the bent portion. Also, the stirring blade may include a first stirring blade having a first bent portion being bent at an angle of 45 to 75 degrees, and a second stirring blade having a second bent portion being additionally bent, from the first stirring blade, at an angle of 120 to 160 degrees.

Also, each of the at least two stirrers may include a support member to enable the stirring blades to be connected with each other, and to enable the stirring blades and the stirring shaft to be connected with each other. In this instance, the support member may be a circular plate including an upper surface perpendicular to the stirring shaft and a lower surface having an inclined surface with respect to the upper surface. Also, an end of the support member may be formed into a saw-toothed shape instead of a gentle curved line-shape.

In addition, the oxidation reactor may further include a gas transportation pipe to inject a gas into the reaction chamber from the outside; a reactant transportation pipe to feed a liquid reactant including a reaction raw material, a solvent, and a catalyst into the reaction chamber; a reflux transportation pipe to feed a reflux into the reaction chamber; a product discharge pipe to discharge a product after a reaction, to the outside; and a gas discharge pipe to discharge a gas generated after the reaction, to the outside.

In this instance, the gas transportation pipe, the reactant transportation pipe, and the reflux transportation pipe may be respectively located within a half of the length of the second stirrer, in a direction of the vertical axis from an imaginary horizontal surface on which the second stirrer is disposed. Also, the gas transportation pipe, the reactant transportation pipe, and the reflux transportation pipe may be respectively bent along a rotation direction of the stirrer to feed the gas, the reactant, and the reflux into the reaction chamber.

Also, the product discharge pipe may be disposed such that an end of the product discharge pipe is located above the first stirrer with respect to the vertical axis. That is, the product discharge pipe may be formed in the upper portion of the reaction chamber.

Also, the oxidation reactor may further include a baffle disposed on a side wall of the reaction chamber to baffle a flow of a liquid, thereby controlling the flow of the fluid.

Also, the oxidation reactor may include at least two gas transportation pipes disposed to be adjacent to each other, when viewed from above the oxidation reactor.

Also, at least one gas transportation pipe, at least one reactant transportation pipe, and at least one reflux transportation pipe may be regularly disposed at identical intervals, when viewed from above the oxidation reactor.

According to an aspect of the present invention, there is provided a method of manufacturing aromatic carboxylic acid using an oxidation reactor, the oxidation reactor being divided into an upper portion and a lower portion with respect to an imaginary plane perpendicular to a middle portion of a vertical axis, and including a first stirrer and a second stirrer radially disposed in the upper portion and the lower portion, respectively, to be perpendicular to the vertical axis, wherein a liquid reactant including an oxygen-containing reaction gas, an alkyl aromatic compound, a solvent, and a catalyst, and a reflux are fed into the lower portion of the oxidation reactor, and a product after a reaction and a gas after the reaction are discharged above the upper portion of the oxidation reactor. In this instance, a temperature of the reflux may be lower than an internal temperature of the oxidation reactor.

Additional aspects, features, and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

As described above according to exemplary embodiments, there is provided a method of manufacturing an aromatic carboxylic acid using an oxidation reactor, which may exhibit excellent reaction characteristics, and thereby a loss of a non-reacted raw material and an amount of generated impurities may be reduced, a loss occurring due to an oxidation decomposition of a solvent used at the time of an oxidation reaction may be suppressed, and entire reaction efficiency as well as a quality of the aromatic carboxylic acid of a resulting product may be significantly improved, resulting in a significant reduction in a cost of production.

That is, according to exemplary embodiments, a concentration of a non-reacted alkyl aromatic compound and a reaction rate of an aliphatic carboxylic acid around the second stirrer, mounted on a lower portion of the stirring shaft of the oxidation reactor, may be maximized. In addition, the concentration of the non-reacted alkyl aromatic compound in the oxidation reactor and a loss of an acetic acid due to an oxidation reaction of the acetic acid may be significantly reduced along a direction of a surface of a liquid of the oxidation reactor.

Thus, the concentration of the non-reacted alkyl aromatic compound may be significantly reduced in a gas-phase area of the reactor, and a discharged amount of a non-reacted raw material discharged to a heat exchanger, a distillation column, and the like, which are installed for processing discharged gases, may be significantly reduced, and thereby a supplementary recovery process may be omitted. Also, a reaction between an oxygen-containing gas and the alkyl aromatic compound of the raw material is performed prior to a reaction with the acetic acid, which may cause a reduction in the loss of the acetic acid acting as the solvent.

Also, according to exemplary embodiments, a product discharge pipe by which a product is discharged to the outside is disposed in an upper portion of the oxidation reactor, and thereby may prevent a product of the aromatic carboxylic acid generated by the oxidation reaction from being precipitated and adhered on a wall or bottom of the oxidation reactor while being circulated to a lower portion of the oxidation reactor. As a result, the product may be stably discharged while not increasing a stirring power, thereby obtaining significant effects on economical efficiency and quality.

These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic cross-sectional diagram illustrating an oxidation reactor for manufacturing aromatic carboxylic acid according to exemplary embodiments of the present invention;

FIG. 2(a) and 2(b) are a development diagram and a cross-sectional diagram, respectively, illustrating a blade of a stirrer according to exemplary embodiments of the present invention.

FIG. 3 is a plane diagram illustrating a state where respective transportation pipes are disposed in a reaction chamber according to exemplary embodiments;

FIG. 4 is a graph illustrating a concentration of a non-reacted paraxylene depending on a height based on results obtained in Example 1 and Comparative Example 1;

FIG. 5 is a graph illustrating a concentration of impurities (4-carboxyl benzaldehyde (CBA)) generated depending on a height based on results obtained in Example 1 and Comparative Example 1;

FIG. 6 is a graph illustrating a reaction rate of an acetic acid depending on a height based on results obtained in Example 1 and Comparative Example 1; and

FIG. 7 is a schematic cross-sectional diagram illustrating an oxidation reactor for manufacturing an aromatic carboxylic acid of Comparative Example 1.

Hereinafter, the present invention will be described in detail by examples. It is to be understood, however, that these examples are for illustrative purpose only, and are not construed to limit the scope of the present invention.

FIG. 1 is a schematic cross-sectional diagram illustrating an oxidation reactor 100 for manufacturing aromatic carboxylic acid according to exemplary embodiments of the present invention.

Referring to FIG. 1, the oxidation reactor 100 for manufacturing aromatic carboxylic acid (hereinafter, referred to as 'oxidation reactor') includes a reaction chamber 110, a stirring shaft 105, a first stirrer 120, a second stirrer 130, a gas transportation pipe 140, a reactant transportation pipe 150, a reflux transportation pipe 160, a product discharge pipe 170, a gas discharge pipe 180, and a baffle 190.

The reaction chamber 110 according to the present exemplary embodiment may be formed into a cylindrical shape, however, the present invention is not limited thereto, and thus may be formed into various shapes. The stirring shaft 105 may be formed along a geometric vertical axis of the reaction chamber 110. The vertical axis may be an area corresponding to a rotation axis of the cylindrical reaction chamber 110. The stirring shaft 105 may transmit a rotation power to the first and

second stirrers

120 and 130 using power transmission.

The first and

second stirrers

120 and 130 may be radially disposed to be spaced apart from each other, along a direction perpendicular to the stirring shaft 105. The first stirrer 120 may be disposed in an upper portion of the reaction chamber 110, and the second stirrer 130 may be disposed in a lower portion of the reaction chamber 110. Also, at least three stirrers may be provided in the reaction chamber 110 even though, according to the present exemplary embodiment, the two

stirrers

120 and 130 are provided. However, taking a stirring power and efficiency of a system into account, it may be preferable the oxidation reactor 100 has two

stirrers

120 and 130. The first and

second stirrers

120 and 130 may have a radial structure of being extended in a single direction or a plurality of directions along the direction perpendicular to the stirring shaft 105. The first and

second stirrers

120 and 130 may perform a stirring operation on the reactant by being rotated with respect to the stirring shaft 105.

The first and

second stirrers

120 and 130 may be a sort of a radial impeller, having a structure in which a horizontal rotating flow is created at an end of the stirrer due to a radial scheme, and at the same time a gas-staying region is not created in the reaction chamber 110, and any stirrer may be used as long as fluid is enabled to softly flow along the end of the impeller. That is, the first and

second stirrers

120 and 130 may have a structure in which a gas-staying region is not created in the reaction chamber 110, and the stirrer includes stirring

blades

122 and 132 having a curved portion or a bent portion formed on an end of the stirring blade to enable the fluid to softly flow along the end of the stirrer.

According to the present exemplary embodiment, the first and

second stirrers

120 and 130 may have a first stirring blade 122 and a second stirring blade 132, respectively. Also, the first and

second stirrers

120 and 130 may be respectively connected with the stirring shaft 105 by means of a first support member 124 and a second support member 134. The

respective stirrers

120 and 130 may create an imaginary rotation surface by means of the

support members

124 and 134 in a direction perpendicular to the stirring shaft 105, and have at least two

stirring blades

122 and 132 formed on an end of the

support members

124 and 134. In addition, the

support members

124 and 134 may be formed into a circular plate having an inclined surface formed on either an upper surface or a lower surface of the circular plate, to be inclined with respect to an imaginary surface perpendicular to the stirring shaft 105. In addition, the circular plate may have a lower inclined surface formed into an arc-shape. The

support members

124 and 134 may be formed into any shape as long as the

support members

124 and 134 are radially extended from the stirring shaft 105. However, it may be preferably the

support members

124 and 134 are formed into the circular plate having the lower inclined surface. This is because an upward circulation flow from among vertical circulation flows may be enhanced. In a case of the inclined surface, an angle of the inclined surface may be about 15 to 20 degrees with respect to a horizontal surface. Also, an end of the

support member

124 and 134 may be formed into a gentle curved line-shape, however, may be formed into a saw-toothed shape.

FIG. 2(a) and 2(b) are a development diagram and a cross-sectional diagram, respectively, illustrating a blade 200 of a stirrer according to exemplary embodiments of the present invention.

Referring to FIG. 2(a), the blade 200 of the stirrer may have a trapezoid shape as a development figure. Obviously, the blade 200 may be formed into various shapes having at least one curved portion or at least one bent portion, leading to various development figures.

The blade 200 may be bent at a first bent portion 212, that is, a center line of the trapezoid shape, at a predetermined angle to thereby be formed into a wedge-shape. Also, the blade 200 may be further bent at a second bent portion 222, that is, a segment BC of a triangle ABC. In this instance, the blade 200 may be bent at the second bent portion 222 in an opposite direction to that in the first bend portion 212. Consequently, the blade 200 may include a first stirrer 210 formed by the first bent portion 212, and a second stirrer 220 formed by the second bent portion 222. In addition, the blade 200 may have a wedge-shaped open portion bent by the first bent portion 212. The wedge-shaped open portion may be oriented toward a rotation direction of the

stirrers

120 and 130.

Referring again to FIG. 2(a), according to the present exemplary embodiment, the segment BC of the blade 200 may be bent to have a length corresponding to 65% to 75% of a length of a corresponding segment of the trapezoid, and a segment AC of the blade 200 may be bent to have a length corresponding to 20% to 30% of a length of a corresponding segment of the trapezoid. In this instance, points B and C of the segments AB and AC may be adjusted based on characteristics of a fluid in the reaction chamber 110.

Referring to FIG. 2(b), the first bent portion 212 may have an angle (α) of 45 to 75 degrees, and the second bent portion 222 may have an angle (β) of 120 to 160 degrees in an opposite direction to that in the first bent portion 212. Unlike this, the angles (α) and (β) may be adjusted to have various angles based on the characteristics of the fluid in the reaction chamber.

As described above, the

stirrers

120 and 130 may prevent a gas containing a molecular form of oxygen introduced into the reaction chamber 110 from remaining in the reaction chamber 110, so that a bubble may become easily minute and may be easily and uniformly dispersed to increase a contact area between a gas and a liquid, thereby improving mass transport characteristics between the gas and the liquid.

The above described

stirrers

120 and 130 may include at least two

stirring blades

122 and 134, and for example, two to eight

stirring blades

122 and 134. Particularly, the

stirrers

120 and 130 may preferably include four to six

stirring blades

122 and 134.

Referring again FIG. 1, an installation location of the

stirrers

120 and 130 has a great influence on stirring of a mixture in the reaction chamber 110, and thereby may be an important factor in achieving aspects of the present invention together with a structure of the

stirrers

120 and 130.

According to the present exemplary embodiment, a ratio (F/D) of a distance (F) between the first stirrer 120 and the second stirrer 130 to a length (or diameter) (D) of the

stirrers

120 and 130 may be 1.0 to 1.5, and the length (D) of the stirrer may be 0.4 to 0.5 times an inside diameter (T) of the reaction chamber 110, that is, D/T=0.4 to 0.5. Also, a distance (C) between the second stirrer 130 and a bottom surface of the reaction chamber 110 may be at least a half of the length (D) of the

stirrers

120 and 130, that is, C/D=0.5 to 1.0.

When F/D<1.0, an upper stirring region and a lower stirring region may be overlapped, and thereby insufficiently mixed region, where a mixing is not sufficiently carried out, may be created in an upper portion and a lower portion of the reaction chamber 110, respectively. Also, when F/D>1.5, the deficient mixing region may be created in a middle portion between the first stirrer 120 and the second stirrer 130.

In addition, when D/T<0.4, a contact efficiency between a raw material and the oxygen-containing gas may be deficient, and thereby a mass transport coefficient may be reduced. Alternatively, when D/T>0.5, the insufficiently mixed region may be created below the second stirrer 130. Similarly, when C/D<0.5, the deficient mixing region may be created below the second stirrer 130. A process of the oxidation reaction in the deficient mixing region may be poorly developed, and thereby an intermediate of the oxidation reaction may be increasingly created.

According to the present exemplary embodiment, a rotation speed of the

stirrers

120 and 130 may be 10 to 100 rpm, and preferably 70 to 90 rpm. Also, a stirring force of the

stirrers

120 and 130 may be 2.08kW/M³ to 4.42kW/M³.

Aspects of the present invention may be achieved such that a transport location and transport method of liquid substances transported in the oxidation reactor 100, a transport location and transport method of a gas, and a transport location and transport method of a reflux, and a discharge location and discharge method of a product may be mutually associated to perform their own functions, as well as the structure and installation location of the

stirrers

120 and 130. Particularly, the aforementioned transport location and transport method and discharge location and discharge method may be designed based on movements of a fluid in the reaction chamber 110, and this may entail a maximization of a reaction efficiency and purity of the product.

Referring again FIG. 1, the oxygen-containing gas may be transported into the reaction chamber 110 through the gas transportation pipe 140. The oxygen-containing gas may be transported around the second stirrer 130, or around the bottom surface of the reaction chamber 110. In addition, the raw material, a catalyst, and a solvent, which are in a liquid state, may be transported into the reaction chamber 110 using the reactant transportation pipe 150. Also, the reflux may be transported into the reaction chamber 110 through the reflux transportation pipe 160. The reflux may designate a liquid in which gas elements obtained after the oxidation reaction are circulated after being subjected to a condensation process, and introduced into the reaction chamber 110.

According to the present exemplary embodiment, the gas transportation pipe 140, the reactant transportation pipe 150, and the reflux transportation pipe 160 may be disposed relatively close to the second stirrer 130 based on an imaginary horizontal surface on which the second stirrer 130 is disposed. That is, the

transportation pipes

140, 150, and 160 may be respectively disposed within a half of a length (D) of the second stirrer 130, in a direction of the stirring shaft 105 from the imaginary surface.

In addition, as described above, in a case where the support member 134 of the second stirrer 130 is the circular plate having the lower inclined surface with respect to the upper surface of the circular plate, the gas transportation pipe 140 may be downwardly disposed below the second stirrer 130.

FIG. 3 is a plane diagram illustrating a state where a gas transportation pipe 340, a reactant transportation pipe 350, and a reflux transportation pipe 360 are respectively disposed in the reaction chamber 110 according to exemplary embodiments.

Referring to FIG. 3, the gas transportation pipe 340, the reactant transportation pipe 350, and the reflux transportation pipe 360 may be regularly disposed at certain intervals therebetween. A total of six gas transportation pipes 340 grouped into twos may be disposed to be adjacent to one other, and a total of three reactant transportation pipes 350 may be regularly disposed to have an angle of 120 degrees with an adjacent pipe, and two reflux transportation pipes 360 may be disposed to face to each other. Each interval between the

transportation pipes

340, 350, and 360 may be practically the same. Through these dispositions of the

transportation pipes

340, 350, and 360, a mutual contact area may increase at the time of mixing gases, substances in a liquid state, and the reflux, and a uniform dispersion of the mixture may be obtained.

Also, an end portion of each of the

transportation pipes

340, 350, and 360 inserted in the reaction chamber 110 may be bent toward a rotation direction of the

stirrers

120 and 130, and preferably toward a tangential direction of the rotation direction, so that the gas, the reactant, and the reflux may be fed into the reaction chamber 110 in the rotation direction, and preferably in the tangential direction. This is because the gas, the reactant, and the reflux may be fed into the reaction chamber 110 based on a flowing direction of the mixture.

Referring again to FIG. 1, the reflux may be a mixture composed of a solvent evaporated by reaction heat generated in the oxidation reactor 110, moisture, and the like, may be a liquid element condensed by a heat exchanger (not illustrated) installed outside the oxidation reactor, and may be a liquid element where a non-condensable gas is separated. The reflux may be fed into the reaction chamber 110 through the reflux transportation pipe 160 to be recycled. In this instance, a temperature of the reflux may be lower than an internal temperature of the reaction chamber 110, and more specifically, may be lower by about 20°C to 60°C than the internal temperature of the reaction chamber 110.

The aromatic carboxylic acid according to an exemplary embodiment may be manufactured such that an alkyl aromatic compound such as paraxylene, that is, a reaction raw material, and a solvent such as an acetic acid may be in contact with the oxygen-containing gas to be reacted. In general, the internal temperature of the reaction chamber 110 may become higher by means of an oxidation reaction heat generated due to the contact with the oxygen-containing gas, and accordingly, an oxidation reaction speed may be gradually accelerated, and thereby an oxidation decomposition speed of the solvent such as the acetic acid may be accelerated. However, according to the present exemplary embodiment, since the reflux with a low temperature is fed into the reaction chamber 110 through the reflux transportation pipe 160, the reflux may function to reduce an ambient temperature heated by the oxidation reaction. Accordingly, an oxidation decomposition of the solvent such as the acetic acid may be suppressed. That is, this suppression effect may be obtained by enabling the reflux with the low temperature to coexist around reactants (including gases) of the oxidation reaction.

Also, the

stirrers

120 and 130 of the present invention may be respectively disposed in the upper and lower portions of the reaction chamber 110. When the reflux is not fed into the reaction chamber 110, an oxidation reaction of the raw material (alkyl aromatic compound) transported around the second stirrer 130 may generally occur within a horizontal rotating flow generated by the second stirrer 130 and at the same time an oxidation reaction of the acetic acid may occur. However, since the reflux with the low temperature is horizontally fed into the horizontal rotating flow to be mixed, causing a liquidus temperature to reduce, the oxidation reaction of the alkyl aromatic compound may occur prior to the oxidation reaction of the acetic acid. Consequently, a loss due to the oxidation reaction of the solvent such as the acetic acid may be significantly reduced.

In addition, since a majority of oxygen transported to the horizontal rotating flow of the lower portion of the reaction chamber 110 is consumed in the horizontal rotating flow around the second stirrer 130, a concentration of an non-reacted alkyl aromatic compound, a concentration of generated impurities, and a reaction rate of the acetic acid may be maximized around the second stirrer 130. However, an oxidation reaction of the non-reacted alkyl aromatic compound and the generated impurities may progress by means of an appropriate upward circulation flow and horizontal rotating flow each generated by a rising residual gas and the stirrer, prior to the oxidation of the acetic acid. In this instance, the oxidation reaction of the non-reacted alkyl aromatic compound and the generated impurities may advance as the alkyl aromatic compound and the impurities are closer to the upper portion of the reaction chamber 110, and thus the non-reacted alkyl aromatic compound and the generated impurities do not practically remain at a surface of a liquid in the oxidation reactor.

Accordingly, the concentration of the non-reacted alkyl aromatic compound transported by the upward circulation flow, the generated impurities, and the oxidation rate of the acetic acid may show their specific dispersions depending on their heights in the reaction chamber 110, and more specifically, may be reduced as the alkyl aromatic compound, the impurities, and the acetic acid are closer to the upper portion (the surface of the liquid) of the oxidation reactor 100.

According to the present exemplary embodiment, a concentration of the non-reacted alkyl aromatic compound relatively close to the surface of the liquid in the oxidation reactor 100 excluding the non-condensable gas element may have about 0.01 wt% or less, preferably about 0.007 wt% or less, and more preferably about 0.005 wt%. In this instance, a concentration of the non-reacted alkyl aromatic compound of a gas-phase portion of the oxidation reaction excluding the non-condensable gas element may be about 0.02 wt% or less, preferably about 0.015 wt% or less, and more preferably about 0.01 wt% or less, which is a significantly small amount not requiring a separation and recovery process by treatment of discharged gases.

Referring again to FIG. 1, an end of the product discharge pipe 170 is disposed above the first stirrer 120, so that a product after the oxidation reaction may be discharged from the upper portion of the reaction chamber 110 or around the surface of the liquid, through the product discharge pipe 170. Accordingly, a location of a portion of the product discharge pipe 170 which is protruded outside the reaction chamber 110 may not be significantly limited. In addition, a gas element generated after the oxidation reaction may be discharged outside the reaction chamber 110 through the gas discharge pipe 180 connected to a cover of the reaction chamber 110.

As described above, the oxidation reactor 100 for manufacturing the aromatic carboxylic acid according to the present exemplary embodiment may include the

stirrers

120 and 130 that generate the horizontal rotating flow and the upward circulation flow, and may adopt a method of transporting, to around the second stirrer 130, the oxygen-containing gas, substances in a liquid state such as the raw materials, and the reflux, and thereby an oxidation reaction may progress by means of the appropriate upward circulation flow and the horizontal rotating flow which are generated by a rising gas and the

stirrers

120 and 130 in the oxidation reactor 100. In this instance, the oxidation reaction may more remarkably advance as being closer to the upper portion of the oxidation reactor 100, and non-reacted raw materials may not exist around the surface of the liquid.

That is, a concentration of non-reacted alkyl aromatic compound around a surface of a reaction solution of the oxidation reactor 100 may be about 0.01 wt% or less, and a reaction rate of conversion to the aromatic carboxylic acid may be about 99.99 wt%. More specifically, the concentration of non-reacted alkyl aromatic compound around the surface of the reaction solution of the oxidation reactor excluding a non-condensable gas element 100 may be about 0.01 wt%, preferably 0.007 wt%, and more preferably about 0.005 wt% or less.

In general, when a residual amount of the alkyl aromatic compound around a surface of a liquid is large, a residual alkyl aromatic compound may be recovered by a heat exchanger, a high-pressure absorption column, or a distillation column, together with a gas discharged from the upper portion of the oxidation reactor 100, however, the present invention does not require this recovery process.

In addition, when a discharge of the product is carried out around the bottom surface of a conventional oxidation reactor, the product discharge pipe may be blocked due to adhesion of solid substances on a wall of the oxidation reactor and sedimentation, however, the present exemplary embodiment may free from this problem. That is, the oxidation reactor 100 of the present exemplary embodiment may consecutively and for a long-term perform a discharge function of the product to improve a process efficiency.

Using the aromatic carboxylic acid according to the present exemplary embodiment, a reaction rate of the acetic acid acting as the solvent may be reduced, and a loss due to the oxidation reaction may be about 2.7 wt% or less based on an amount of the aromatic carboxylic acid generated in the oxidation reaction, and preferably may be about 2.5 wt%.

Referring again to FIG.1, the oxidation reactor 100 may include a baffle 190 disposed on a side wall of the reaction chamber 110 to control a flow of a fluid. Two to eight baffles may be mounted at identical intervals. A width of the baffle 190 may be about 5% to 20% of an inner diameter (T) of the reaction chamber 110. In addition, the baffle 190 may be required to be mounted to be located equal to or lower than the surface of the reaction solution in the reaction chamber 110. When the baffle 190 is mounted to be located higher than the surface of the reaction solution, a slurry element may be slashed up to and adhered on a wall of the baffle 190 above the surface of the reaction solution, and thereby a crystal may be grown. This crystal may fall down in the reaction chamber 110 to interrupt a stable operation of the oxidation reactor 100.

Hereinafter, a method of manufacturing the aromatic carboxylic acid will be described in detail.

Oxidation process

(1) Alkyl aromatic compound (raw material)

As the alkyl aromatic compound, that is, a raw material used in the present exemplary embodiment, an alkyl group-containing aromatic compound may be used. An aromatic ring compound consisting of the aromatic compound may be a single ring (monocyclic) compound or a multi ring (polycyclic) compound.

As the alkyl group, a methyl group, an ethyl group, an n-propyl group, and an isopropyl group may be used. Also, the alkyl group may have a functional group. For example, as the functional group, an aldehyde group, an acyl group, a carboxylic group, and a hydroxyl group, and the like may be used.

As examples of an alkyl-substituted aromatic compound, alkylbenzenes, alkylnaphthalenes, and alkylbiphenyls, which have two to four alkyl groups, each alkyl group with one to four carbon atoms, such as m-diisopropylbenzene, p-diisopropylbenzene, m-cymene, p-cymene, m-xylene, o-xylene, p-xylene, trimethylbenzene and the like, may be given.

Also, as the alkyl group-containing aromatic compound, substituents-containing compounds other than the alkyl group may be used. As examples of the alkyl group-containing aromatic compound, 3-methyl benzaldetyde, 4-methyl benzaldetyde, m-toluic acid, p-toluic acid, 3-fomyl benzoic acid, 4-fomyl benzoic acid, 2-methyl-6-fomylnaphthalenes, and the like may be given. The above-mentioned compounds may be used alone or in a combination of two or more.

(2) oxidation process for manufacturing of terephthalic acid

Paraxylene as the raw material of the oxidation reactor 100, a solvent, a catalyst, an oxygen-containing gas, and a recycling solution of some elements of a mother liquor generated in a separation process, which will be described in detail later, are put in the oxidation reactor 100, and consecutively reacted. As the solvent, an aliphatic carboxylic acid such as an acetic acid, a propionic acid, a formic acid, a lactic acid, and the like may be used, however, a solvent including the acetic acid as a main element may be preferably used. A used amount of the solvent may be one to ten times that of a general raw material when a terephthalic acid is used as the raw material, preferably two to eight times, and more preferably three to six times. When an amount of the acetic acid is significantly less, a concentration of a generated slurry may significantly increase, causing problems in that pipes are blocked, and when the amount of the acetic acid is significantly great, a lager facility may be required, causing economical problems.

As the solvent according to the present exemplary embodiment, a mixture of the acetic acid and water may be preferably used. In this instance, the water may be contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the acetic acid, and preferably 5 to 15 parts by weight based on 100 parts by weight of the acetic acid.

As examples of the oxygen-containing gas, air, oxygen diluted using an inert gas, and air containing oxygen in a large amount may be given, however, the air may be practically used. The oxygen-containing gas may be used to have 3 mol to 100 mol of oxygen based on 1 mol of the raw material. The air may have an oxygen content of about 21Vol% in an inlet of the oxidation reactor 100. Also, a concentration of oxygen from among gases discharged from the oxidation reactor 100 may be about 1 Vol% to 8 Vol%, and preferably about 1.5 Vol% to 3 Vol%.

A catalyst may not be particularly limited as long as the alkyl aromatic compound is oxidized in a liquid to be converted into the aromatic carboxylic acid using the catalyst. As the catalyst, heavy metal compounds may be used, and a bromine compound may be used as a catalyst auxiliary agent. As examples of the heavy metals contained in the heavy metal compound, cobalt (Co), manganese (Mn), nickel (Ni), chrome (Cr), zirconium (Zr), copper, plumbum (Pb), hafnium (Hf), cerium (Ce), and the like may be given. The heavy metals may be used alone or in a combination of two or more. Particularly, a combination of Co and Mn may be preferably used. As examples of the heavy metal compound, an acetic acid salt, a nitrate, an acetyl acetate salt, a naphthenate acid salt, a stearic acid salt, a bromine compound, and the like may be given, and particularly, the acetic acid salt and the bromine compound may be used.

As examples of the bromine compound, inorganic bromine compounds such as molecular bromine, hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, manganese bromide, and the like, and organic bromine compounds such as methyl bromide, methylene bromine, bromoform, benzyl bromide, bromomethyltoluene, dibromoethane, toribromoethane, tetrabromoethane, and the like may be given. The bromine compounds may be used alone or in a combination of two or more.

When a terephthalic acid may be manufactured using the aromatic carboxylic acid, as a catalyst of a bromine compound used when oxidizing paraxylene, a catalyst obtained by combining cobalt bromide, manganese bromide, and hydrogen bromide may be preferably used.

According to the present exemplary embodiment, as for a catalyst obtained by combining the heavy metal compound and the bromine compound, 0.05 mol to 10 mol of bromine atoms may be used based on 1 mol of the heavy meal, and preferably 0.1 mol to 5 mol of bromine atoms. This catalyst, acting as a heavy metal catalyst of a solvent, may be used in an amount of about 10 mass ppm to 10,000 mass ppm, and preferably about 100 mass ppm to 3,000 mass ppm.

A temperature of an oxidation reaction may be about 140°C to 250°C, and preferably 150°C to 230°C. When the temperature of the oxidation reaction is significantly low, a speed of the oxidation reaction may be reduced, and when the temperature of the oxidation reaction is significantly high, a loss due to ignition of the acetic acid acting as the solvent may be increased. A reaction heat generated at the time of the oxidation reaction may be an evaporation heat generated by evaporating the solvent, and may be removed to be outside the oxidation reactor 100 to control the temperature of the oxidation reaction. A generated steam may consist of a condensable element such as the solvent of the acetic acid, water, and the like, and a non-condensable element such as nitrogen, oxygen, and the like. In this instance, the steam may be condensed by a heat exchanger installed outside the oxidation reactor 100, and separated into a gas and a liquid. Next, a discharged gas from among the gas may be transported to a high-pressure absorption column, a distillation column, an expander, and the like, and thereby a recovery of effective elements and a recovery of energy may be carried out. The separated liquid may be recycled as the reflux in the oxidation reactor 100. In addition, the distillation column may be installed in the upper portion of the oxidation reactor 100 to replace the heat exchanger, and thereby may separate into water and the solvent. In this instance, the solvent may be recycled in the oxidation reactor 100, and a gas-phase element containing water may be classified into a condensable element and a non-condensable element in the heat exchanger, and processed for the purpose of recycle, energy recovery, and the like.

A pressure of the oxidation reaction may require at least a pressure capable of maintaining a mixture to be in a liquid state at least at a reaction temperature, and also require at least an atmospheric pressure. Specifically, the reaction pressure may require a pressure of about 0.2 MPa to 6 MPa, and preferably about 0.4 MPa to 3 MPa. To easily transport generated aromatic carboxylic acid slurry, a relatively high pressure may be preferable, and thus may help to suppress a side reaction. In addition, in terms of a pressure resistance of a reaction vessel, an installation cost, and the like, a relatively low pressure may be preferable.

The oxidation reaction may be consecutively performed, and a reaction time (average residence time) of the oxidation reaction may be about 30 to 300 minutes, and specifically, about 40 to 150 minutes. When the reaction time is significantly short, the oxidation reaction may be poorly performed, causing deterioration in a quality of the aromatic carboxylic acid, and when the reaction time is significantly long, a loss occurring due to ignition of the solvent of the acetic acid may increase, and a capacity of the oxidation reactor may become greater, causing economical problems.

According to the present exemplary embodiment, a supplementary process may be performed, as necessary. As the supplementary process, an oxidation process with respect to a product obtained by the oxidation reaction may be consecutively carried out under an oxygen presence at least once, without feeding the raw material at a lower or higher temperature than that of the oxidation reaction.

Separation process

A product obtained by the oxidation process may be crystallized to increase a precipitation amount of a crystal, and then the crystallized product may be washed using a solid-liquid separation process, or a prepared slurry may be directly washed using the solid-liquid separation process. An obtained solid may be a crude aromatic carboxylic acid, and may be subjected to a refining process, which will be described as below. In addition, some elements of a separated mother liquor may be recovered to be detoxified, and then discharged outside, and the remaining elements of the separated mother liquor may be kept by maintaining temperature and pressure, or may be cooled and circulated through the oxidation process to be recycled.

Refining process

The crude aromatic carboxylic acid separated by the separation process may need to refine contained impurities to improve a purity. In general, the impurities may be deoxidized by adding hydrogen to increase their solubility, and thereby may be separated due to a solubility difference with the aromatic carboxylic acid that is sparingly soluble. Next, the aromatic carboxylic acid may be washed and dried to obtain a refined aromatic carboxylic acid. Since the separated mother liquor contains the deoxidized impurities and an intermediate of the aromatic carboxylic acid, the separated mother liquor may be recovered to be used in the oxidation reaction.

Above, the method of manufacturing the aromatic carboxylic acid, especially a high-purity carboxylic acid was described, and the method may be applicable in a method of manufacturing an intermediate-purity carboxylic acid, which may perform an oxidation process of two stages at a high pressure and a high temperature while omitting the refining process. In the oxidation process of the two stages, a product of an oxidation reaction of a first stage may be transported to an oxidation reactor of a second stage, and an oxygen-containing gas may be transported to the oxidation reactor to thereby consecutively perform the oxidation reaction. Descriptions of the oxidation reaction of the first state may be the same as the above-described oxidation reaction. A reaction temperature of the oxidation reaction of the second stage may be about 230°C to 290°C, and preferably about 240°C to 280°C. A pressure of the oxidation reaction of the second stage may require a pressure capable of maintaining a reaction mixture to be in a liquid state. In this instance, the pressure of the oxidation reaction of the second stage may be 3 MPa to 10 MPa, and a residence time may be 5 to 120 minutes, and preferably 10 to 60 minutes.

The refining process may be omitted since both a part of aromatic carboxylic acid particles of the slurry is dissolved and an oxidation intermediate of the particles are oxidized by the oxidation reaction of the two stages. However, the intermediate-purity carboxylic acid having a relatively lower purity than that of the high-purity carboxylic acid obtained using the refining process may be obtained by the oxidation reaction of the two stages,. The oxidation reactor according to the present exemplary embodiment may be applicable in an oxidation reaction process performed for manufacturing the intermediate-purity aromatic carboxylic acid.

[Example 1]

1 part by weight of paraxylene, 5 parts by weight of an acetic acid, and 0.5 parts by weight of water were fed into the oxidation reactor, and a cobalt acetate, a maganeses acetate, and a hydrogen bromide acting as catalysts were also fed into the oxidation reactor. Under a condition of a temperature of about 185°C to 195°C and a pressure of about 1.0 MPa to 1.7 MPa, an oxidation reaction was performed for 90 minutes of a reaction time (average residence time). The catalysts had cobalt, maganeses, and bromine contents of 300 mass ppm, 300 mass ppm, and 700 mass ppm, respectively, in terms of the metal. As an oxygen-containing gas, air was used. In this instance, the air had an oxygen content of about 21Vol%, and a compressed air was transported into the oxidation reactor so that a concentration of oxygen of a gas discharged into the oxidation reactor had 3 Vol% to 7 Vol%.

As the oxidation reactor, the oxidation reactor 100 of FIG. 1 was used. Each length of the first and

second stirrers

120 and 130 was 2,550 mm, a vertical distance from a bottom of the oxidation reactor to the second stirrer 130 was 1,500 mm, and a distance from the second stirrer 130 to the first stirrer 120 was 3,200 mm. A product was discharged from an upper portion of the oxidation reactor, which is separated by 4,100 mm from the second stirrer 130. Reactants such as the compressed air, a reflux, a raw material, a solvent, a catalyst, and the like were transported to a nearly same height as that of the second stirrer 130, in a tangential direction of a rotation direction of the second stirrer 130. Disposition of transportation pipes was the same as that of the transportation pipes of FIG. 3. The compressed air was transported through the gas transportation pipe 140 (total six pipes), and an acetic acid solution consisting of the paraxylene, an acetic acid-water mixture, and the catalyst was previously mixed in a mixing chamber, together with the recycling solution circulated in the separation process, and then transported through the reactant transportation pipe 150. The reflux was transported through the reflux transportation pipe 160 (total two pipes). In addition, a distance between the

respective transportation pipes

140, 150, and 160 with a rotation circumference of the second stirrer 130 was about 100 mm. A temperature when the reflux was transported to the oxidation reactor 100 was 150°C to 160°C, and an internal temperature of the oxidation reactor 100 was lower by at least 5 degrees than that of Comparative Example 1. In addition, in a case of the oxidation reactor 100 of Example 1, a blockage-phenomenon of the product discharge pipe 170 did not occur for about a half year, and a stable operation of the oxidation reactor 100 was realized. A product discharged from the product discharge pipe 170 was consecutively transported to a supplementary oxidation reactor, and an oxidation reaction was performed for 35 minutes of the reaction time (average residence time), under a temperature of 180°C to 190°C and a pressure of 0.9 MPa to 1.5 MPa. The air (oxygen-concentration of 21 Vol%) was fed into the oxidation reactor, so that a concentration of the oxygen of the discharged gas was 3 Vol% to 7 Vol%, and then a low-temperature supplementary oxidation reaction was performed. The supplementary oxidation reaction was performed using a reactor where a conventional two-step disc turbine is installed.

A product obtained by the supplementary oxidation reaction was crystal- precipitated in a stepwise manner using a crystal precipitation tank connected to the reactor in three stage series, and thereby the resulting product was solid-liquid separated/washed by a rotary vacuum filter (RVF) to thereby obtain a crude terephthalic acid. 90% of a reaction mother liquor subjected to the solid-liquid separation process was recycled in the oxidation reactor. Also, significant substances such as the catalyst, the acetic acid, and the like were recovered from the remaining mother liquor, transported to a discharge treatment process, and then discharged.

Next, the crude terephthalic acid was transported to the refining process, and the above described hydrogen addition reaction of impurities was performed under a general refining condition. Next, the impurities, deoxidized by the above described crystal precipitation/separation process, and the terephthalic acid were separated to obtain a high-purity terephthalic acid. Obtained results are shown in Table 1, which will be described in detail later, together with results of Comparative Example 1 below.

[Comparative Example 1]

Using the oxidation reactor, an oxidation reaction was performed under the same reaction condition of the oxidation reaction as that of Example 1. An initial reaction temperature was the same as that of Example 1, however, an internal temperature of Comparative Example 1 after stable operation of the oxidation reactor was higher by at least 5 degrees than that of Example. An internal structure of the oxidation reactor was shown in FIG. 7. FIG. 7 is a schematic cross-sectional diagram illustrating an oxidation reactor 700 for manufacturing an aromatic carboxylic acid of Comparative Example 1. Referring to FIG. 7, the oxidation reactor 700 includes a stirring shaft 705, a reaction chamber 710, a first stirrer 720, a second stirrer 730, a gas transportation pipe 740, a reactant transportation pipe 750, a reflux transportation pipe 760, a product discharge pipe 770, and a gas discharge pipe 780. A capacity of the oxidation reactor 700 was the same as that of Example 1, the first and

second stirrers

720 and 730 includes six stirring blades, respectively, and an end of the stirring blade was a flat plate. In addition, locations of the first and

second stirrers

720 and 730 were the same as those of the first and

second stirrers

120 and 130 of Example 1.

Each length of the first and

second stirrers

720 and 730 was 2,300 mm, a vertical distance from a bottom of the oxidation reactor 700 to the second stirrer 730 was 1,500 mm, and a distance from the second stirrer 730 to the first stirrer 720 was 3,200 mm.

Transportation of the air was carried out around the second stirrer 730, an acetic acid solution consisting of paraxylene, an acetic acid-water mixture, and a catalyst was mixed with the recycling solution circulated in the separation process, and transported to around the first stirrer 720. A product was discharged from around the bottom of the oxidation reactor 700.

A supplementary oxidation reaction was performed after the oxidation reaction, and the separation process and the refining process were performed in the same condition as that of Example to thereby obtain a high-purity terephthalic acid. Results obtained by Example 1 and Comparative Example 1 are shown in Table 1.

In Table 1, a residual concentration of paraxylene (PX) is a concentration (wt%) of PX around a surface of a liquid of the oxidation reactor, a yield is a yield (Kg) of a product of PTA (high-purity terephthalic acid) obtained from 100 tons of the raw material of PX, and a loss of the acetic acid is an amount (Kg) of the acetic acid consumed by the oxidation reaction of the oxidation reactor, per one ton of the PTA product. Also, a concentration of PX in a reaction gas-phase area is a concentration (wt%) of PX of elements excluding a non-condensable gas of the reaction gas-phase area, and a PTA transmittance is a transmittance (%) in a wavelength of 340 μm and an optical path of 10 mm of a caustic alkali-aqueous solution of the PTA product.

As shown in Table 1, in comparison between results of Example 1 and Comparative Example 1, it could be found that the reaction yield was improved, the loss of acetic acid was reduced, and a duration of the stable operation of the reactor increased. Also, it could be found that a non-reacted raw material of the paraxylene in the gas-phase area of the oxidation reactor was significantly reduced, and a paraxylene-recovery device was not be used. Also, as shown in the PTA transmittance, the transmittance of the alkali-aqueous solution of the PTA product was improved, and an amount of impurities, as being representative as 4-carboxyl benzaldehyde (CBA) of the PTA, was significantly reduced.

FIG. 4 is a graph illustrating a concentration of a non-reacted paraxylene depending on a height based on results obtained in Example 1 and Comparative Example 1. FIG. 5 is a graph illustrating a concentration of impurities (4-CBA) generated depending on a height based on results obtained in Example 1 and Comparative Example 1. FIG. 6 is a graph illustrating a reaction rate of an acetic acid depending on a height based on results obtained in Example 1 and Comparative Example 1. To obtain the results of the graphs of FIGS. 4 to 6, a fluid simulation was performed with respect to concentration dispersion in a direction of the surface of the liquid of the oxidation reactor, using a computational fluid dynamics (CFD).

Referring to FIGS. 4 to 6, it can be found that each concentration of the non-reacted paraxylene, the residual 4-CBA, and the acetic acid in the oxidation reactor is significantly reduced. Also, respective concentration dispersions show a remarkably insignificant change, and the concentration dispersion around the surface of the liquid of the oxidation reactor is significantly reduced.

Although a few exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described exemplary embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

An oxidation reactor for manufacturing aromatic carboxylic acid, the oxidation reactor comprising:

a reaction chamber;

a stirring shaft disposed along a geometric vertical axis of the reaction chamber; and

at least two stirrers, each including stirring blades, each stirring blade having either a curved portion or a bent portion formed on an end of the stirring blade to enable fluid to flow in the reaction chamber while preventing the fluid from remaining in the reaction chamber, and each stirring blade being extended radially along a direction perpendicular to the vertical axis to be rotated.
The oxidation reactor of claim 1, wherein:

the oxidation reactor includes a first stirrer and a second stirrer being spaced apart from each other, and each being disposed on the stirring shaft of the reaction chamber, the first stirrer being disposed in an upper portion of the reaction chamber and the second stirrer being disposed in a lower portion of the reaction chamber, and

a spaced distance between the first stirrer and the second stirrer is 1 to 1.5 times a length (diameter) of either the first stirrer or the second stirrer.
The oxidation reactor of claim 1, wherein the length (diameter) of the stirrer is 0.4 to 0.5 times an inner diameter of the reaction chamber.
The oxidation reactor of claim 2, wherein a distance between the second stirrer and a bottom surface of the reaction chamber is 0.5 to 1 times the length (diameter) of the second stirrer.
The oxidation reactor of claim 1, wherein the stirring blade includes at least two of either the curved portion or the bent portion.
The oxidation reactor of claim 5, wherein the stirring blade includes a first stirring blade having a first bent portion being bent at an angle of 45 to 75 degrees, and a second stirring blade having a second bent portion being additionally bent, from the first stirring blade, at an angle of 120 to 160 degrees.
The oxidation reactor of claim 1, wherein each of the at least two stirrers includes a support member to enable the stirring blades to be connected with each other, and to enable the stirring blades and the stirring shaft to be connected with each other.
The oxidation reactor of claim 7, wherein the support member is a circular plate including an upper surface perpendicular to the stirring shaft and a lower surface having an inclined surface with respect to the upper surface.
The oxidation reactor of claim 8, wherein an end of the support member is formed into a saw-toothed shape.
The oxidation reactor of claim 2, further comprising:

a gas transportation pipe to inject a gas into the reaction chamber from the outside;

a reactant transportation pipe to feed a liquid reactant including a reaction raw material, a solvent, and a catalyst into the reaction chamber;

a reflux transportation pipe to feed a reflux into the reaction chamber;

a product discharge pipe to discharge a product after a reaction, to the outside; and

a gas discharge pipe to discharge a gas generated after the reaction, to the outside.
The oxidation reactor of claim 10, wherein the gas transportation pipe, the reactant transportation pipe, and the reflux transportation pipe are respectively located within a half of the length of the second stirrer, in a direction of the vertical axis from an imaginary horizontal surface on which the second stirrer is disposed.
The oxidation reactor of claim 10, wherein the gas transportation pipe, the reactant transportation pipe, and the reflux transportation pipe are respectively bent along a rotation direction of the stirrer to feed the gas, the reactant, and the reflux into the reaction chamber.
The oxidation reactor of claim 10, wherein the product discharge pipe is disposed such that an end of the product discharge pipe is located above the first stirrer with respect to the vertical axis.
The oxidation reactor of claim 10, wherein, at least one gas transportation pipe, at least one reactant transportation pipe, and at least one reflux transportation pipe are regularly disposed at identical intervals, when viewed from above the oxidation reactor.
The oxidation reactor of claim 1, further comprising:

a baffle disposed on a side wall of the reaction chamber to baffle a flow of a liquid.
A method of manufacturing aromatic carboxylic acid by injecting an oxygen-containing gas, an alkyl aromatic compound, a solvent, a catalyst, and a reflux into an oxidation reactor to be subjected to an oxidation reaction, wherein

the oxygen-containing gas, the alkyl aromatic compound, the solvent, the catalyst, and the reflux are fed into a lower portion of the oxidation reactor, and a reaction product is discharged from an upper portion of the oxidation reactor.
A method of manufacturing aromatic carboxylic acid using an oxidation reactor, the oxidation reactor being divided into an upper portion and a lower portion with respect to an imaginary plane perpendicular to a middle portion of a vertical axis, and including a first stirrer and a second stirrer radially disposed in the upper portion and the lower portion, respectively, to be perpendicular to the vertical axis, wherein

a liquid reactant including an oxygen-containing reaction gas, an alkyl aromatic compound, a solvent, and a catalyst, and a reflux are fed into the lower portion of the oxidation reactor, and a product after a reaction and a gas after the reaction are discharged above the upper portion of the oxidation reactor.
The method of claim 17, wherein a temperature of the reflux is lower than an internal temperature of the oxidation reactor.
The method of claim 17, wherein an oxidation reaction of the alkyl aromatic compound is carried out prior to an oxidation reaction of the solvent.
The method of claim 17, wherein the discharge of the product of the reaction is carried out at a surface of a liquid in the oxidation reactor.
The method of claim 17, wherein, relatively close to the surface of the liquid in the oxidation reactor, a concentration of a non-reactive alkyl aromatic compound excluding a non-condensable gas element is 0.01 wt% or less.
The method of claim 17, wherein, within a gas phase area of the oxidation reactor, a concentration of a non-reactive alkyl aromatic compound excluding a non-condensable gas element is 0.02 wt% or less.
The method of claim 17, wherein the reaction gas, the liquid reactant, and the reflux are transported to the second stirrer.
The method of claim 17, wherein, a concentration of the alkyl aromatic compound and a concentration of impurities decrease as the alkyl aromatic compound and the impurities are closer to the upper portion of the oxidation reactor.
The method of claim 17, wherein, an oxidation rate of the solvent decreases as the solvent is closer to the upper portion of the oxidation reactor.