JP2008150313A - Method for producing high-purity terephthalic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing high-purity terephthalic acid by which the frequency of catalyst exchange is reduced by suppressing the reduction of the activities of the catalyst for hydrogenation by long-term use, and the catalyst cost can be reduced. <P>SOLUTION: The method for producing the high-purity terephthalic acid includes (I) a step for forming a crude terephthalic acid slurry by mixing the crude terephthalic acid obtained by the liquid-phase oxidation of para-xylene with water, (II) a step for forming an aqueous crude terephthalic acid solution by heating and dissolving the crude terephthalic acid slurry, (III) a step for subjecting the aqueous solution of the crude terephthalic acid to hydrogenation process, (IV) a step for crystallizing the terephthalic acid from the aqueous terephthalic acid solution after hydrogenation, and (V) a step for subjecting the obtained terephthalic acid slurry to solid-liquid separation. The method is characterized by the content of microorganisms contained in the water to be mixed with the crude terephthalic acid in the step (I) and regulated so as to be ≤4,000/g based on the measurement value (1-10 μm) by RION. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing high-purity terephthalic acid, and more specifically, the inclusion of impurities contained in water mixed with crude terephthalic acid when preparing a slurry of crude terephthalic acid obtained by liquid phase oxidation of para-xylene. The present invention relates to a method for producing high-purity terephthalic acid by reducing the amount.

  Oxidation of para-xylene in a liquid phase with a molecular oxygen-containing gas results in crude terephthalate containing 4-carboxybenzaldehyde (hereinafter also referred to as “4-CBA”) in addition to terephthalic acid (hereinafter also referred to as “TA”). An acid (hereinafter also referred to as “CTA”) is generated. In the production of polyester and the like, CTA containing a large amount of 4-CBA causes a deterioration in quality. Therefore, high-purity terephthalic acid (hereinafter also referred to as “PTA”) is required as a raw material, and the CTA needs to be purified.

  As a method for purifying CTA, hydrogenation treatment is known (see, for example, JP-A-4-66553). In this method, CTA is completely dissolved in water at high temperature and high pressure to prepare a CTA aqueous solution. This aqueous solution is subjected to hydrogenation treatment in the presence of a noble metal catalyst such as palladium and 4-CBA which is easy to eutect with TA. Is converted to p-toluic acid (hereinafter also referred to as “p-TA”) which is difficult to eutectic. Thereafter, the temperature is lowered stepwise to prepare TA slurry, solid-liquid separation is performed, and the filtrate is dried to obtain PTA containing a very small amount of 4-CBA.

  The hydrogenation treatment is performed by preparing a fixed bed of a solid catalyst carrying a noble metal such as palladium in a reactor and supplying hydrogen while passing an aqueous CTA solution through the fixed bed. At this time, the temperature of the reactor is kept almost constant, and the space velocity and linear velocity of the aqueous solution are also kept constant. Therefore, theoretically, the 4-CBA content in the PTA is kept almost constant.

  However, in practice, the activity of noble metals such as palladium gradually decreases as the hydrogenation treatment amount, that is, the catalyst life becomes longer, and the 4-CBA content in the PTA gradually increases. Therefore, in order to keep the 4-CBA content in the PTA constant, it is necessary to take measures such as gradually increasing the hydrogen partial pressure as the catalyst life increases, but the hydrogen partial pressure is determined from the pressure resistance of the reactor. When the upper limit is reached, there is a problem in that the catalyst must be partially replaced, and a great amount of cost is required. For this reason, it is necessary to suppress the fall of catalyst activity as much as possible.

  For example, Japanese Patent Laid-Open No. 9-263666 discloses a specific activated carbon in order to prevent a decrease in activity due to masking of metals such as Co and Mn contained as impurities in CTA and heavy metals such as Cu and Cr caused by corrosion of equipment. A catalyst that is used as a carrier and carries a noble metal such as palladium has been proposed.

  Japanese Patent Laid-Open No. 2000-37633 discloses a granulated activated carbon having a specific physical shape and a low sulfur content in order to further suppress the activity reduction of the catalyst described in Japanese Patent Laid-Open No. 9-263666. There has been proposed a catalyst in which a noble metal such as palladium is supported.

However, in an actual plant, even if such a catalyst is used, the catalytic activity still decreases, so further improvement is required.
JP-A-4-66553 JP-A-9-263666 JP 2000-37633 A

  The present invention is intended to solve the problems associated with the prior art as described above, and can reduce the catalyst replacement frequency by suppressing the decrease in the activity of the hydrogenation catalyst due to long-term use, thereby reducing the catalyst cost. It aims at providing the manufacturing method of high purity terephthalic acid.

  As a result of diligent research to solve the above problems, the present inventors have found that the quality of industrial pure water used as water mixed with crude terephthalic acid when preparing a crude terephthalic acid slurry in an actual plant is high. The inventors have found that this is one of the causes of a decrease in catalyst activity.

  Industrial pure water is usually produced by taking river water and applying various treatments, and is stored and circulated. For example, insoluble inorganic substances such as gravel and metal oxides are removed by agglomeration, precipitation, sand filtration, activated carbon filtration, microfiltration capable of removing foreign matters on the micrometer order, ultrafiltration, etc., and cations such as metal ions and sulfuric acid. Anions such as ions are removed by ion exchange treatment or the like. However, very small particulate matter such as microorganisms may not be completely removed in the filtration step after sterilization and may remain in the treated water. Among such granular materials, the proliferative granular materials such as microorganisms grow during storage and circulation, and the concentration thereof increases. The present inventors have found that the proliferative particulate matter such as microorganisms grown during the storage and circulation is one of the causes of the decrease in the activity of the hydrogenation catalyst such as palladium, and completed the present invention. It came to do.

That is, the method for producing high-purity terephthalic acid according to the present invention includes:
(I) A step of forming a crude terephthalic acid slurry by mixing crude terephthalic acid obtained by liquid phase oxidation of para-xylene and water, and (II) forming a crude terephthalic acid aqueous solution by heating and dissolving the crude terephthalic acid slurry. (III) Step of hydrogenating the crude terephthalic acid aqueous solution, (IV) Step of crystallizing terephthalic acid from the terephthalic acid aqueous solution after hydrogenation, (V) Solid-liquid separation of the obtained terephthalic acid slurry In the method for producing high-purity terephthalic acid including the step of:
The content of microorganisms contained in the water mixed with the crude terephthalic acid in the step (I) is adjusted to 4000 / g or less based on the RION measurement value (1 to 10 μm).

In the present invention, at least one element selected from the group consisting of S, Cr, Ni, Ca, Cu, Zn, Mg and Pb contained in the slurry obtained by mixing the crude terephthalic acid and water in the step (I). The content of is preferably adjusted to the following conditions (a) to (h).
(A) S: 1 ppm or less (b) Cr: 5 ppm or less (c) Ni: 5 ppm or less (d) Ca: 5 ppm or less (e) Cu: 5 ppm or less (f) Zn: 5 ppm or less (g) Mg: 5 ppm or less ( h) Pb: 3 ppm or less In the present invention, it is preferable to adjust the content of the microorganisms by microfiltration of water mixed with crude terephthalic acid using a microfilter immediately before mixing.

According to the present invention, by reducing the concentration of impurities contained in the water mixed with the crude terephthalic acid, particularly the concentration of proliferative particulate matter such as microorganisms, it is possible to suppress the decrease in the activity of noble metal-based catalysts such as palladium. The life of the catalyst is prolonged, the frequency of catalyst replacement is reduced, and the catalyst cost can be reduced.

The method for producing high-purity terephthalic acid according to the present invention comprises (I) a step of mixing crude terephthalic acid obtained by liquid phase oxidation of paraxylene and water to form a crude terephthalic acid slurry, and (II) the crude terephthalic acid. A step of heating and dissolving the acid slurry to form a crude terephthalic acid aqueous solution; (III) a step of hydrogenating the crude terephthalic acid aqueous solution using a noble metal catalyst such as palladium; and (IV) a terephthalic acid aqueous solution after hydrogenation. And (V) a step of solid-liquid separation of the obtained terephthalic acid slurry.

(I) Slurry forming step:
In this step, a crude terephthalic acid slurry is formed by mixing crude terephthalic acid obtained by liquid phase oxidation of para-xylene and water. The liquid phase oxidation of paraxylene can be carried out in an oxidation reactor generally used for the production of terephthalic acid. The oxidation reactor preferably contains a raw material such as para-xylene, a catalyst, and a solvent, and can perform continuous liquid phase oxidation by blowing air while replenishing these raw materials.

  The liquid phase oxidation of paraxylene is usually performed using a solvent and a catalyst. Examples of the solvent include fatty acids such as acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caproic acid, and mixtures of these with water. Of these, a mixed solvent of acetic acid and water is preferable. Examples of the catalyst include heavy metals, bromine, and compounds thereof. Examples of heavy metals include nickel, cobalt, iron, chromium, manganese, and the like. These catalysts are preferably used in the form of being dissolved in the reaction system. As said catalyst, it is preferable to use a cobalt compound, a manganese compound, and a bromine compound together, and the usage-amount of a cobalt compound is 10-10,000 ppm normally in conversion of cobalt with respect to a solvent, Preferably it is 100-3000 ppm. Further, the manganese compound preferably has an atomic ratio of manganese to cobalt of 0.001 to 2, and the bromine compound preferably has an atomic ratio of bromine to cobalt of 0.1 to 5.

  The liquid phase oxidation of para-xylene is usually performed using a molecular oxygen-containing gas. As such an oxygen-containing gas, a diluted oxygen gas obtained by diluting oxygen with an inert gas is usually used. For example, air or air enriched with oxygen is used. The temperature of the oxidation reaction is usually 150 to 270 ° C., preferably 170 to 220 ° C., and the pressure is at least the pressure at which the mixture can maintain a liquid phase at the reaction temperature, and usually 0.5 to 4 MPa (gauge pressure). . Further, although the reaction time depends on the size of the apparatus, etc., the residence time is usually about 20 minutes to 180 minutes. The water concentration in the reaction system is usually 3 to 30% by weight, preferably 5 to 15% by weight.

  CTA obtained by the liquid phase oxidation reaction is separated and recovered from the mother liquor in the liquid phase oxidation reaction by solid-liquid separation. The recovered CTA usually contains about 4-0.4% by weight of 4-CBA as an impurity.

  CTA containing such 4-CBA and water are mixed in a mixing tank to form a CTA slurry. The said mixing tank can use what is generally used for manufacture of a terephthalic acid. The CTA concentration of the CTA slurry is usually 10 to 40% by weight, preferably 24 to 30% by weight.

As water to be mixed with CTA, industrial pure water is usually used in an actual plant. In the present invention, the content of microorganisms in this industrial pure water is adjusted to 4000 cells / g or less based on the RION measurement value (1 to 10 μm). Here, the RION measurement value is a value measured using a particle counter (model number: KL-01, pressure injection method, CH1 to CH4; 1 to 10 μm) manufactured by Rion Co., Ltd.

  By adjusting the content of microorganisms in the industrial pure water to the above range, it is possible to suppress the activity reduction of the hydrogenation catalyst described later. On the other hand, microorganisms do not grow under high temperature and high pressure, but if the content of microorganisms exceeds the above range, some of them remain as insoluble impurities in the pores of the catalyst support even under high temperature and high pressure, and TA inside the pores. There is a risk of inhibiting the diffusion of.

  In general, the content of microorganisms in industrial pure water can be reduced by sand filtration or activated carbon treatment after sterilizing raw water with chlorine. However, in order to reduce the content of microorganisms to the above range by chlorine sterilization, excessive chlorine is introduced into the raw water, which requires a sufficient anion exchange treatment, which is economically undesirable. Moreover, if the chlorine concentration in pure water increases due to the introduction of chlorine, there is a risk of causing halogen corrosion in the hydrogenation process or the subsequent product drying process. On the other hand, if the input amount of chlorine is limited, microorganisms that cannot be sterilized may remain in the treated water.

  For example, it is known that aggregating bacteria represented by Zoogloea grow in a shaded oligotrophic field such as in the piping of a pure water production process. Some algae such as Scenedesmus and Euglena also grow and proliferate even in dark places such as in pipes. If such microorganisms remain in the treated water, the water treatment apparatus (especially in the anion exchange tower and the exchange tower outlet) is treated between the treatment of the industrial pure water and the mixing with the crude terephthalic acid. The catalyst activity is reduced by growing in the pipe in the side drum) or in a pipe having a relatively long residence time and entering the packed bed of the hydrogenation catalyst.

  Therefore, in order to prevent the above problems, in the present invention, the industrial pure water is microfiltered with a microfilter immediately before mixing with crude terephthalic acid, and the number of microorganisms measured (RION measurement value) is 4000 pieces / g or less. To do.

  In addition, noble metal catalysts such as palladium are easily poisoned by anions such as sulfate ions and halogen ions. In particular, when the catalyst metal is changed to sulfide by sulfate ions or hydrogen sulfide, the catalytic activity is remarkably lowered. In an actual plant, the anions are often contained in industrial pure water. In the present invention, it is preferable to reduce the concentration of these anions, and in particular, it is obtained by mixing CTA and the industrial pure water. It is preferable to adjust the sulfur concentration in the resulting slurry to 1 ppm or less. Sulfate ions in industrial pure water can be reduced by controlling the space velocity and linear velocity of an anion exchange apparatus used when processing industrial pure water to an appropriate level.

  Other poisoning substances of noble metal catalysts such as palladium include Cr, Ni, Ca, Cu, Zn, Mg, Pb, and these compounds. Since these poisonous substances may clog the pores of the carrier, particularly when a noble metal is supported on a porous carrier such as activated carbon, the concentration in the slurry obtained by mixing CTA and the above industrial pure water It is preferable that Cr, Ni, Ca, Cu, Zn, and Mg are reduced to 5 ppm or less and Pb to 3 ppm or less in terms of element concentration. The concentration of these poisoning substances in industrial pure water can be reduced by strengthening sand filtration treatment (insoluble matter filtration) and cation exchange treatment (metal ion removal) in water treatment. The poisoning substance may be corroded and eluted from the process material in the liquid phase oxidation process of para-xylene, and may be contained not only in industrial pure water but also in crude terephthalic acid. In this case, the above-mentioned poisoning contained in the crude terephthalic acid may be strengthened by solid-liquid separation after the oxidation step or by strengthening rinse when a rinse-washing type separator is used for solid-liquid separation. Substances can be reduced.

(II) Aqueous solution formation process:
In this step, the CTA slurry is heated with a heat exchanger to dissolve CTA and form a CTA aqueous solution. As a heat exchanger, what is generally used for manufacture of terephthalic acid can be used. Moreover, you may heat in steps using a some heat exchanger.

  The heating conditions are not particularly limited as long as the CTA is completely dissolved and the aqueous solution can be maintained in a substantially liquid phase. For example, the heating temperature is usually 230 ° C. or higher, preferably 240 to 300 ° C., and the pressure in the system is Usually, it is 1-11 MPa (gauge pressure), preferably 3-9 MPa (gauge pressure).

(III) Hydrogenation process:
In this step, the CTA aqueous solution is introduced into a hydrogenation reactor and subjected to hydrogenation treatment, and 4-CBA contained in the CTA aqueous solution is reduced to p-toluic acid (p-TA).

  If the said hydrogenation reaction tank has a catalyst layer filled with the hydrogenation catalyst and can supply hydrogen in the state which the catalyst and CTA aqueous solution contacted, the shape, structure, etc. will not be restrict | limited in particular. A preferable hydrogenation reaction tank has a fixed catalyst layer filled with a solid catalyst inside, an aqueous solution introduction path and an aqueous solution outlet path so that a CTA aqueous solution can be passed through the catalyst layer, and hydrogen is further supplied. The thing which has a hydrogen supply path so that it can supply is mentioned. The flow direction of the CTA aqueous solution is not limited and may be an upward flow or a downward flow. However, it is preferable that the CTA aqueous solution flow in the downward flow. For this purpose, the aqueous solution introduction path is formed above the hydrogenation reaction tank. It is preferable that the path is provided in the lower part. Moreover, it is preferable that hydrogen is supplied from the upper part, and for this purpose, it is preferable that a hydrogen supply path is provided in the upper part of the hydrogenation reaction tank.

  As the hydrogenation catalyst, those conventionally used can be used, such as palladium, ruthenium, rhodium, osmium, iridium, platinum, platinum black, palladium black, iron, cobalt-nickel, etc. A solid catalyst in which these are supported on an adsorbent carrier such as activated carbon, titania or zirconia, preferably an adsorbent carrier such as activated carbon, is preferable. Among these, a catalyst in which palladium is supported on activated carbon (hereinafter referred to as “Pd / C”) is preferable in terms of high activity and low cost.

  As a specific hydrogenation treatment method, for example, a CTA aqueous solution is introduced into a hydrogenation reaction tank, and while passing through the catalyst layer, hydrogen gas is usually 1.5 times mol or more of 4-CBA in the CTA aqueous solution, preferably It is desirable to perform hydrogenation by supplying at a flow rate of 2 times mole or more. The hydrogen partial pressure at the time of hydrogenation is usually 0.05 MPa or more, preferably 0.05 to 2 MPa. Hydrogen gas may be accompanied by hydrogen sulfide derived from petroleum refining, but the concentration of hydrogen sulfide in hydrogen gas can be reduced by enhancing gas separation and refining such as pressure swing adsorption.

The hydrogenation reaction temperature is usually 230 ° C. or higher, preferably 235 to 300 ° C., and the pressure in the system is usually 1 to 11 MPa (gauge pressure), preferably 3 to 9 MPa (gauge pressure).
By this hydrogenation treatment, 4-CBA in CTA is reduced to water-soluble p-TA. On the other hand, since TA is poorly soluble in water, high purity terephthalate is obtained by separating 4-CBA from CTA aqueous solution by crystallization and solid-liquid separation at a temperature of usually 300 ° C. or lower, preferably 100 to 280 ° C. An acid can be obtained.

(IV) Crystallization process:
In this step, TA is crystallized by cooling the CTA aqueous solution after hydrogenation (hereinafter referred to as “CTA hydrogenation treatment liquid”) in a crystallization tank with a reduced pressure. As the crystallization tank, those generally used for the production of terephthalic acid can be used. Alternatively, TA may be crystallized by stepwise cooling using a plurality of crystallization tanks.

  Specifically, the CTA hydrogenation treatment liquid is introduced into a crystallization tank set to a pressure condition lower than the pressure of the CTA hydrogenation treatment liquid, and the pressure of the CTA hydrogenation treatment liquid is reduced. The additive treatment liquid is cooled (step-down cooling). Thereby, terephthalic acid is crystallized and TA slurry is formed.

(V) Solid-liquid separation process:
In this step, the TA slurry is solid-liquid separated to separate and recover PTA from the mother liquor. Solid-liquid separation can be carried out using a solid-liquid separation apparatus such as a filter or a centrifuge, which is generally used for producing terephthalic acid.

Furthermore, the PTA may be suspended again in water, and the foreign matter adhering to the PTA crystal may be transferred to the aqueous phase, followed by solid-liquid separation and drying.
FIG. 1 is an example of a flow diagram of a method for producing high-purity terephthalic acid according to the present invention. In the method for producing high-purity terephthalic acid according to the present invention, first, CTA slurry is supplied to a CTA slurrying tank 1 by supplying water (industrial pure water) and CTA that have been microfiltered with a microfilter 2 just before supply and stirring. Form. At this time, the water recovered by the solid-liquid separation device 8 after TA reslurry may also be supplied to the CTA slurry tank 1. The recovered water may be supplied to the CTA slurrying tank 1 after being microfiltered with a microfilter as required.

  This CTA slurry is heated and pressurized by the heat exchanger 3 to dissolve the CTA and prepare a CTA aqueous solution. Next, this CTA aqueous solution and hydrogen gas are supplied to the hydrogenation reactor 4 to perform a hydrogenation treatment. The obtained CTA hydrogenation treatment liquid is introduced into the crystallization tank 5 and subjected to crystallization by reducing the pressure and cooling to form a TA slurry.

  The obtained TA slurry is introduced into the solid-liquid separator 6 for solid-liquid separation, and the aqueous phase is separated and removed. As a result, most of the water-soluble component such as p-toluic acid is removed. On the other hand, water is added to the obtained TA crystal and introduced into the TA reslurry tank 7 to make a slurry. This TA slurry is introduced into the solid-liquid separator 8 through the valve V1, and is separated into solid and liquid. The obtained TA crystal is dried with a TA drier 9 to obtain PTA. On the other hand, the aqueous phase may be supplied to the CTA slurrying tank 1 as recovered water.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by this Example.

[Comparative Example 1]
Sodium hypochlorite was added to the river water stored in the water storage pit to sterilize microorganisms in the water to prepare primary treated water. The primary treated water was agglomerated, sand filtered, pressurized flotation separated and precipitated separated, then subjected to cation and anion exchange treatment, and filtered through a polypropylene microfilter having a pore size of 3 μm. The microparticulate matter captured by the microfilter was confirmed to be a group of microorganisms having a diameter of 10 μm or less composed of bacteria or algae by microscopic observation. The microorganism group recovered here is mixed with ultrapure water obtained by subjecting industrial pure water to activated carbon treatment and then reverse osmosis membrane treatment, and the RION measurement value (1 to 10 μm) is 50,000 / g. An aqueous solution containing fine particles was prepared.

1 g of 0.5% Pd / C catalyst was placed in a titanium catalyst cage and mounted in a titanium-lined autoclave reactor having an internal volume of 500 ml and a pressure resistance of 300 kg / cm ² . In this reactor, 0.
CTA slurry containing 19% by weight of 4-CBA and 200 g of the above aqueous solution containing microorganisms were charged to prepare a CTA slurry containing 40000 microorganisms / g.

  Hydrogen gas was introduced into the reactor, the internal pressure was increased to 0.7 MPa (gauge pressure), and the mixture was heated until the liquid temperature reached 278 ° C. while stirring at 300 rpm. Next, the catalyst cage containing the Pd / C catalyst was dropped into the liquid to start the hydrogenation reaction. Two hours after the start of the reaction, the catalyst basket was pulled up and immediately cooled with air. After the liquid temperature was lowered to 90 ° C., the pressure was released and the reaction product was collected on a glass filter and suction filtered to collect PTA. The PTA was dried at 80 ° C. overnight and cooled.

When 4-CBA contained in the obtained PTA was analyzed by a polarographic method, it was 55 ppm.
[Comparative Example 2]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 13000 / g is prepared, and 10400 microorganisms / g are contained from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. PT in the same manner as in Comparative Example 1 except that a CTA slurry was prepared
A was produced.

4-CBA contained in obtained PTA was 5 ppm.
[Example 1]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g was prepared, and 3200 cells / g of microorganisms were prepared from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. PTA was produced in the same manner as in Comparative Example 1 and Comparative Example 2 except that a CTA slurry was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (detection limit).
[Comparative Example 3]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and sulfuric acid (3 ppm as a sulfur concentration) was prepared, and 3200 from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. Pcs / g microorganisms and sulfuric acid (2 ppm as sulfur concentration)
PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry was prepared.

4-CBA contained in obtained PTA was 12 ppm.
[Example 2]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and sulfuric acid (1 ppm as a sulfur concentration) was prepared, and 3200 from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. Pcs / g microorganisms and sulfuric acid ( 1 ppm as sulfur concentration)
PTA was produced in the same manner as in Comparative Example 3 except that a CTA slurry containing

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 4]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and hydrogen sulfide (8 ppm as a sulfur concentration) was prepared, and from 200 g of this aqueous solution and 50 g of CTA containing 0.19 wt% 4-CBA. PTA was produced in the same manner as in Comparative Example 1, except that a CTA slurry containing 3200 microorganisms / g of microorganisms and hydrogen sulfide (6 ppm as the sulfur concentration) was prepared.

4-CBA contained in obtained PTA was 33 ppm.
[Comparative Example 5]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and hydrogen sulfide (4 ppm as the sulfur concentration) was prepared, and 200 g of this aqueous solution and 0.19% by weight of 4-
A PTA was produced in the same manner as in Comparative Example 4 except that a CTA slurry containing 3200 cells / g of microorganisms and hydrogen sulfide (sulfur concentration: 3 ppm) was prepared from 50 g of CTA containing CBA.

4-CBA contained in obtained PTA was 6 ppm.
[Example 3]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and hydrogen sulfide (sulfur concentration: 0.4 ppm) was prepared, and 50 g of CTA containing 200 g of this aqueous solution and 0.19% by weight of 4-CBA. PTA was produced in the same manner as Comparative Example 4 and Comparative Example 5 except that a CTA slurry containing 3200 microorganisms / g and hydrogen sulfide (sulfur concentration: 0.3 ppm) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 6]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and chromium (III) acetylacetonate (chromium concentration of 13 ppm) was prepared, and 200 g of this aqueous solution and 0.19% by weight of 4-CBA were prepared. CT containing 50 g of CTA and 3200 / g microorganisms and chromium (III) acetylacetonate (10 ppm as chromium concentration)
PTA was produced in the same manner as in Comparative Example 1 except that A slurry was prepared.

4-CBA contained in obtained PTA was 17 ppm.
[Example 4]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and chromium (III) acetylacetonate (chromium concentration of 6 ppm) was prepared, and 200 g of this aqueous solution and 0.19% by weight of 4-CBA were prepared. A PTA was produced in the same manner as in Comparative Example 6 except that a CTA slurry containing 3200 microorganisms / g of microorganisms and chromium (III) acetylacetonate (chromium concentration: 5 ppm) was prepared from 50 g of CTA.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 7]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and nickel (II) acetylacetonate dihydrate (nickel concentration: 13 ppm) was prepared. 3200 / g microorganisms and nickel (II) acetylacetonate dihydrate (nickel concentration is 1)
PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing 0 ppm was prepared.

4-CBA contained in obtained PTA was 8 ppm.
[Example 5]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and nickel (II) acetylacetonate dihydrate (nickel concentration: 6 ppm) was prepared. Of CTA containing 4-CBA of 3200 / g of microorganisms and nickel (II) acetylacetonate dihydrate (5p as nickel concentration)
PTA was produced in the same manner as in Comparative Example 7 except that a CTA slurry containing pm) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 8]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and calcium acetylacetonate (calcium concentration of 13 ppm) was prepared, and 50 g of CTA containing 200 g of this aqueous solution and 0.19% by weight of 4-CBA. PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing 3200 microorganisms / g and calcium acetylacetonate (calcium concentration of 10 ppm) was prepared.

4-CBA contained in obtained PTA was 8 ppm.
[Example 6]
An aqueous solution containing microorganisms having RION measurement values (1 to 10 μm) of 4000 cells / g and calcium acetylacetonate (calcium concentration of 6 ppm) was prepared, and CTA 50 g containing 200 g of this aqueous solution and 0.19% by weight of 4-CBA. A PTA was produced in the same manner as in Comparative Example 8 except that a CTA slurry containing 3200 microorganisms / g and calcium acetylacetonate (calcium concentration of 5 ppm) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 9]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and copper (II) acetylacetonate (a copper concentration of 13 ppm) was prepared, and 200 g of this aqueous solution and 0.19% by weight of 4-CBA were prepared. PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing 3200 microorganisms / g of microorganisms and copper (II) acetylacetonate (10 ppm in terms of copper concentration) was prepared from 50 g of CTA.

4-CBA contained in obtained PTA was 6 ppm.
[Example 7]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and copper (II) acetylacetonate (6 ppm as copper concentration) was prepared, and 200 g of this aqueous solution and 0.19% by weight of 4-CBA were prepared. 3200 cells / g microorganisms and copper (II)
) PTA was produced in the same manner as in Comparative Example 9 except that a CTA slurry containing acetylacetonate (5 ppm as copper concentration) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 10]
An aqueous solution containing microorganisms having RION measurement values (1 to 10 μm) of 4000 cells / g and zinc acetylacetonate (zinc concentration of 13 ppm) was prepared, and CTA containing 200 g of this aqueous solution and 0.19% by weight of 4-CBA was 50 g. A PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing 3200 microorganisms / g and zinc acetylacetonate (zinc concentration of 10 ppm) was prepared.

4-CBA contained in obtained PTA was 5 ppm.
[Example 8]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and zinc acetylacetonate (zinc concentration of 6 ppm) was prepared, and CTA 50 g containing 200 g of this aqueous solution and 0.19 wt% 4-CBA. A PTA was produced in the same manner as in Comparative Example 10 except that a CTA slurry containing 3200 microorganisms / g and zinc acetylacetonate (zinc concentration of 5 ppm) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 11]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and magnesium ethoxide (magnesium concentration of 13 ppm) was prepared, and 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA, PTA was produced in the same manner as Comparative Example 1 except that a CTA slurry containing 3200 microorganisms / g of microorganisms and magnesium ethoxide (magnesium concentration of 10 ppm) was prepared.

4-CBA contained in obtained PTA was 5 ppm.
[Example 9]
An aqueous solution containing microorganisms having RION measurement values (1 to 10 μm) of 4000 cells / g and magnesium ethoxide (magnesium concentration of 6 ppm) was prepared, and 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA, PTA was produced in the same manner as in Comparative Example 11 except that a CTA slurry containing 3200 microorganisms / g of microorganisms and magnesium ethoxide (magnesium concentration of 5 ppm) was prepared.

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 12]
An aqueous solution containing microorganisms having RION measurement values (1 to 10 μm) of 4000 cells / g and lead acetate (lead concentration of 13 ppm) was prepared from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. 3200 microorganisms / g and lead acetate (10p as lead concentration)
PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing pm) was prepared.

4-CBA contained in obtained PTA was 17 ppm.
[Comparative Example 13]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and lead acetate (6 ppm as the lead concentration) was prepared. From 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA 3200 microorganisms / g and lead acetate (lead concentration 5ppm
PTA was produced in the same manner as in Comparative Example 1 except that a CTA slurry containing

4-CBA contained in obtained PTA was 10 ppm.
[Example 10]
An aqueous solution containing microorganisms having a RION measurement value (1 to 10 μm) of 4000 cells / g and lead acetate (lead concentration of 4 ppm) was prepared from 200 g of this aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA. 3200 microorganisms / g and lead acetate (lead concentration 3ppm
PTA was produced in the same manner as Comparative Example 12 and Comparative Example 13 except that a CTA slurry containing

4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).
[Comparative Example 14]
Sodium hypochlorite was added to the river water stored in the water storage pit to sterilize microorganisms in the water to prepare primary treated water. The primary treated water was agglomerated, sand-filtered, pressurized flotation separated and precipitated, and then subjected to cation and anion exchange treatment to prepare secondary treated water. When the concentration of the fine particulate matter in the secondary treated water was immediately measured, the RION measurement value (1 to 10 μm) was 1583 / g. Microscopic observation of the morphology of the microparticulates confirmed that they were algae and bacteria.

  Next, the secondary treated water was retained at about 40 ° C. under light shielding in a residence time of 20 minutes on a drum and a pipe, collected as the tertiary treated water, and then measured for the concentration of fine particulate matter. It was 4406 pieces / g in (1-10 micrometers). In the same manner as described above, microscopic observation of the morphology of the fine particulate matter confirmed that it was algae and bacteria.

P was prepared in the same manner as in Comparative Example 1 except that a CTA slurry containing 3525 microorganisms / g was prepared from 200 g of this tertiary treated water and 50 g of CTA containing 0.19% by weight of 4-CBA.
TA was produced.

4-CBA contained in obtained PTA was 7 ppm.
[Example 11]
The tertiary treated water prepared by the same method as in Comparative Example 14 was filtered through a polypropylene microfilter having a pore diameter of 3 μm, and the concentration of fine particles was measured immediately. The measured RION value (1 to 10 μm) was 1141 / g. there were.

A PTA was produced in the same manner as in Comparative Example 14 except that a CTA slurry containing 913 microorganisms / g was prepared from 200 g of this filtered aqueous solution and 50 g of CTA containing 0.19% by weight of 4-CBA.

  4-CBA contained in the obtained PTA was less than 5 ppm (lower detection limit).

FIG. 1 is an example of a flow diagram of a method for producing high-purity terephthalic acid according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CTA slurrying tank 2 Microfilter 3 Heat exchanger 4 Hydrogenation reactor 5 Crystallization tank 6 Solid-liquid separator 7 TA reslurry tank 8 Solid-liquid separator 9 TA dryer

Claims (3)

(I) A step of forming a crude terephthalic acid slurry by mixing crude terephthalic acid obtained by liquid phase oxidation of para-xylene and water, and (II) forming a crude terephthalic acid aqueous solution by heating and dissolving the crude terephthalic acid slurry. (III) Step of hydrogenating the crude terephthalic acid aqueous solution, (IV) Step of crystallizing terephthalic acid from the terephthalic acid aqueous solution after hydrogenation, (V) Solid-liquid separation of the obtained terephthalic acid slurry In the method for producing high-purity terephthalic acid including the step of:
The high-purity terephthalic acid characterized in that the content of microorganisms contained in the water mixed with the crude terephthalic acid in the step (I) is adjusted to 4000 / g or less on the basis of the RION measurement value (1 to 10 μm). Manufacturing method. The content of at least one element selected from the group consisting of S, Cr, Ni, Ca, Cu, Zn, Mg and Pb contained in the slurry obtained by mixing the crude terephthalic acid and water in the step (I). The method for producing high-purity terephthalic acid according to claim 1, wherein the conditions are adjusted to the following conditions (a) to (h).
(A) S: 1 ppm or less (b) Cr: 5 ppm or less (c) Ni: 5 ppm or less (d) Ca: 5 ppm or less (e) Cu: 5 ppm or less (f) Zn: 5 ppm or less (g) Mg: 5 ppm or less ( h) Pb: 3 ppm or less   The method for producing high-purity terephthalic acid according to claim 1 or 2, wherein the content of the microorganisms is adjusted by microfiltration of water mixed with crude terephthalic acid with a microfilter immediately before mixing.

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