WO2004063136A1 - Method for producing high purity terephthalic acid - Google Patents
Method for producing high purity terephthalic acid Download PDFInfo
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- WO2004063136A1 WO2004063136A1 PCT/JP2003/016786 JP0316786W WO2004063136A1 WO 2004063136 A1 WO2004063136 A1 WO 2004063136A1 JP 0316786 W JP0316786 W JP 0316786W WO 2004063136 A1 WO2004063136 A1 WO 2004063136A1
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- terephthalic acid
- slurry
- steam
- condensate
- mother liquor
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
Definitions
- the present invention relates to a method for producing high-purity terephthalic acid. ⁇ Background technology>
- the crude terephthalic acid obtained by the oxidation of para-xylene usually contains relatively large amounts of various impurities including 4-carboxybenzaldehyde. Used as a raw material.
- the crude terephthalic acid is dissolved in water, and the above-mentioned lipoxybenzaldehyde is reduced to paratoluic acid, and the difference in solubility between terephthalic acid and paratoluic acid in water is determined.
- a method is employed in which the pressure and temperature are reduced by depressurizing and cooling a crude terephthalic acid aqueous solution in a high-temperature and high-pressure state, and mainly terephthalic acid alone is crystallized.
- Patent Literature 1 describes a method of utilizing the steam, in which a condensate obtained by condensing the steam is recycled as the water.
- Patent Document 2 describes that the above-mentioned steam is used as a part of a heat source for obtaining the above-mentioned crude terephthalic acid aqueous solution.
- Patent Document 3 discloses a method for recovering the separated mother liquor, in which terephthalic acid containing a large amount of paratoluic acid is precipitated by cooling the separated mother liquor, and recovering terephthalic acid containing a large amount of paratoluic acid by solid-liquid separation.
- Patent Literature 4 describes that the separated mother liquor is used as water or a washing solution in a dissolving step in a process.
- Patent Document 1 US Pat. No. 3,584,039
- Patent Document 2 Japanese Patent Application Laid-Open No. 08-2252589
- Patent Document 3 Japanese Patent Application Laid-Open No. Sho 52-1-2283424
- Patent Literature 4 Japanese Patent Application Laid-Open No. 05-0-058 948
- an object of the present invention is to make effective use of the steam generated in the crystallization step. It is another object of the present invention to make effective use of the vapor generated in the crystallization process and the condensate of this vapor.
- the crude terephthalic acid obtained by oxidizing para-xylene is suspended in an aqueous medium to form a slurry, and then heated to completely dissolve the slurry of the crude terephthalic acid.
- a method for producing high-purity terephthalic acid by subjecting terephthalic acid to crystallization in a crystallization tank and subjecting the obtained terephthalic acid slurry to a first solid-liquid separation step, in the crystallization step in the above-described crystallization tank, the pressure is released and cooled. And / or condensate thereof, so that the concentration of paratoluic acid in the primary separation mother liquor obtained in the first solid-liquid separation becomes 800 to 200 ppm by weight.
- the steam generated in the crystallization step is heat-exchanged with the crude terephthalic acid slurry to heat the steam generated in the crystallization step to the crude terephthalic acid slurry.
- the vapor generated in the crystallization step by the heat exchange is condensed into a condensate, and the condensate is used as a part of the aqueous medium.
- the steam generated in the crystallization step is subjected to heat exchange with water by heat exchange with water, thereby converting the water into steam and condensing the steam generated in the crystallization step into a condensate.
- the above-mentioned problem is also solved by using the steam as a utility of an apparatus or an apparatus for producing the crude terephthalic acid or the high-purity terephthalic acid, and using the condensate as a part of the aqueous medium. can do.
- the above problem can be solved by using the steam as a part of a heat source for heating the slurry of the crude terephthalic acid.
- FIG. 1 is a flowchart showing an example of a process for producing high-purity terephthalic acid according to the present invention.
- FIG. 2 is a schematic diagram showing another example of the process for producing high-purity terephthalic acid according to the present invention.
- 11 is a mixing tank
- 12 is a first heat exchanger
- 13 is a hydrogenation reactor
- 14 is a crystallization tank
- 15 is a first solid-liquid separator
- 16 is 2nd heat exchanger
- 17 is 3rd heat exchanger
- 18 is storage tank
- 19 is cooling tank
- 20 is 2nd solid-liquid separator
- A is crude terephthalic acid
- C crude terephthalic acid slurry
- D crude terephthalic acid solution
- E reduction treatment liquid
- F terephthalic acid slurry
- G high-purity terephthalic acid crystals
- H steam
- I condensate
- J primary Separated mother liquor
- K is paratoluic acid-containing terephthalic acid slurry
- L is secondary crystal
- M is secondary separated mother liquor
- N condensate purge liquid
- P is secondary separated mother liquid purge liquid.
- the high-purity terephthalic acid according to the present invention is produced through the steps shown in FIG. First, para-xylene is oxidized in an oxidation step to obtain crude terephthalic acid A, and this crude terephthalic acid A is suspended in an aqueous medium B in a mixing tank 11 to obtain a crude terephthalic acid slurry C. I do. Next, the crude terephthalic acid slurry c is pressurized to a predetermined pressure, and heated in the first heat exchanger 12 to completely dissolve the crude terephthalic acid A in the aqueous medium B to obtain a crude terephthalic acid solution. Get D.
- the reduction treatment liquid E is introduced into a crystallization tank 14 to crystallize terephthalic acid, and the obtained terephthalic acid slurry F is converted into a first solid-liquid separator. Introduced in 15 and subjected to the first solid-liquid separation process. By recovering the solid content, high-purity terephthalic acid crystals G can be obtained. This high-purity terephthalic acid crystal G is dried and shipped as a product.
- the crude terephthalic acid A contains 100 to 500 ppm as by-products in the oxidation step as impurities.
- the above-mentioned lipoxybenzaldehyde is reduced to paratoluic acid by a reduction treatment using hydrogen gas. Since this paratoluic acid has a higher solubility in water than terephthalic acid, when the above-mentioned reduction treatment solution E is crystallized, first, terephthalic acid is preferentially precipitated. Therefore, high-purity terephthalic acid is produced by precipitating and recovering terephthalic acid under conditions in which paratoluic acid is difficult to precipitate.
- the aqueous medium refers to a medium used in producing high-purity terephthalic acid using the above crude terephthalic acid, and specifically refers to water.
- the reduction treatment liquid E was introduced into the crystallization tank 14 set at a pressure lower than the pressure of the reduction treatment liquid E, and the pressure was released. This is followed by cooling (hereinafter the operation of pressure relief / cooling is abbreviated as “pressure relief cooling”). Thereby, terephthalic acid is crystallized.
- the crystallization step when depressurized cooling is performed, a part of the aqueous medium in the reduction treatment liquid E is vaporized, and steam H of the aqueous medium is generated.
- This steam H is sent as a heat source to the second heat exchanger 16 provided in the pipe through which the crude terephthalic acid slurry C flows.
- the crude terephthalic acid slurry C and the steam H undergo heat exchange, and the steam H generated in the crystallization step is used as a part of a heat source for heating the crude terephthalic acid slurry. .
- the heat energy of the steam H can be used effectively.
- the heating load on the first heat exchanger 12 can be reduced.
- the steam H is condensed by the above heat exchange to generate a condensate I.
- steam H generated by depressurizing and cooling in the crystallization step in the crystallization tank 14 is heat-exchanged with water W 1 in the third heat exchanger 17.
- the water W1 is used as the steam W2
- the steam W2 is used as a heat exchange medium in the second heat exchanger 16 for heating the crude terephthalic acid slurry C.
- the steam W 2 can be used as a part of a heat source for heating the crude terephthalic acid slurry C.
- the heat energy of the steam H can be effectively used, and the heating load in the first heat exchanger 12 can be reduced.
- the vapor H is condensed by the above heat exchange to generate a condensate I.
- the above-mentioned water vapor W2 is used not only as a heat exchange medium for the second heat exchanger 16 but also for other equipment or apparatus for producing the above crude terephthalic acid or high-purity terephthalic acid. Can be used as a role. Examples of such equipment or devices include heat exchangers, dryers, ejectors, steam turbines, and the like.
- the equipment uses a titanium material with excellent corrosion resistance because of severe conditions of high temperature and high pressure.
- a feature of preventing the titanium material from being embrittled by hydrogen contained in the gas generated from the crystallization tank 14 can be exhibited.
- the vapor H of the aqueous medium generated by the depressurized cooling in the crystallization process is used as a raw material for the terephthalate of the mixing tank 11 and the piping to reach it or the hydrogenation reaction tank 13 and the piping to reach it without condensing it. It may be introduced into any site until the acid is dissolved. This makes it possible to use the energy of the steam H for dissolving terephthalic acid and to reuse the steam itself as an aqueous medium.
- the number of the crystallization tanks 14 is one in FIGS. 1 and 2, it is preferable to connect two or more crystallization tanks 14 in series.
- By connecting a plurality of crystallization tanks 14 in series it is possible to not only perform one-step depressurized cooling from the pressure of the reducing solution E to the set pressure of the first solid-liquid separator 15 but also reduce the pressure. Minutes Thus, the pressure release can be reduced.
- the crystallization can be performed more mildly in each crystallization tank, the incorporation of the impurity paratoluic acid into the terephthalic acid crystals can be suppressed, and the particle size of the terephthalic acid crystals can be reduced.
- the distribution can be controlled.
- a heat exchanger is installed in each crystallization tank, and the crude terephthalic acid slurry C is heated in order from the heat exchanger at the subsequent stage to improve efficiency. Can be heated well.
- the temperature difference between the reduction treatment and the first crystallization was reduced to 50 ° C or less. Is preferred.
- the condensate I may be sent to the mixing tank 11 via the storage tank 18. Further, the aqueous medium may be recovered by performing a distillation treatment or a membrane treatment, and the recovered aqueous medium may be used. As a result, the amount of the new aqueous medium B used can be reduced, the condensate I can be reused, and the utility equipment and the wastewater treatment load can be reduced.
- the primary separated mother liquor obtained in the first solid-liquid separation step: 1, that is, the remaining mother liquor obtained by fractionating high-purity terephthalic acid crystals G in the first solid-liquid separator 15 is provided in a cooling tank 19 To be subjected to a cooling process.
- the temperature of the terephthalic acid slurry sent to the first solid-liquid separation step is 120 to 170 ° C, and the primary separation mother liquor J discharged from the first solid-liquid separation step is the same.
- the primary separated mother liquor J is depressurized and cooled to be concentrated and cooled to about 40 to 60 ° C., and low-purity terephthalic acid crystals containing a large amount of paratoluic acid are precipitated.
- the pressure at this time is preferably adjusted to a so-called negative pressure of less than 1 atm using a pressure reducing device.
- the primary separation mother liquor J may be concentrated by applying heat or cooled by heat exchange using a refrigerant.
- the paratoluic acid-containing terephthalic acid slurry K obtained in the concentration and cooling step is sent to a second solid-liquid separator 20 to perform a second solid-liquid separation step of separating a secondary crystal L and a secondary separation mother liquor M. .
- the secondary crystal L is a solid content containing a large amount of paratoluic acid, it can be used as a raw material for terephthalic acid by donating it to the above oxidation reaction.
- at least a portion of the second separated mother liquor M contains paratoluic acid, but a larger amount of paratoluic acid has been removed compared to the first separated mother liquor J.
- it may be sent to the mixing tank 11 and used as a part of the aqueous medium B.
- the amount of the new aqueous medium B can be further reduced, and the secondary separated mother liquor M can be reused. Can be reduced.
- the vapor H and / or its condensate I and the secondary mother liquor M generated in the crystallization process contain paratoluic acid. For this reason, if the direct re-use amount of the condensate I or the secondary separation mother liquor M is too large, the amount of paratoluic acid contained in the crude terephthalic acid slurry C increases, and as a result, This means that the concentration of paratoluic acid in the pure terephthalic acid crystal G will increase.
- the usage ratio of the condensate I and the secondary separation mother liquor M in the aqueous medium is such that the concentration of paratoluic acid contained in the high-purity terephthalic acid crystal G is 50 to 200 ppm, Preferably, to maintain the concentration at 100 to 150 ppm, the concentration of paratoluic acid in the primary separated mother liquor J obtained by the first solid-liquid separation is 800 to 2000% by weight! ) It is preferable to use p so as to be p m. If the concentration of paratoluic acid contained in terephthalic acid crystal G exceeds 200 p, impurities will be too large for high-purity terephthalic acid as a product. In addition, if it is less than 50 ppm, the quality is excessive.
- the condensate I and the secondary separation mother liquor M are directly reused, the condensate I is preferentially used, and the secondary separation mother liquor M has a paratoluic acid concentration in the primary separation mother liquor J. Determine the amount of use in proportion.
- one of the condensate I and the secondary separation mother liquor M is treated by distillation, membrane separation, use of a synthetic adsorbent, etc.
- the recovery side should be used preferentially, and the side directly reused should determine the amount to be used based on the paratoluic acid concentration in the primary separation mother liquor J.
- the amount of new aqueous medium B used can be reduced and utility equipment can be reduced. It is possible to achieve reduction in size and load on wastewater treatment.
- the concentration may be too low, it may not be preferable in terms of production efficiency. If the concentration is too high, the operation itself may be hindered due to blockage or the like.
- the high-purity terephthalic acid crystal G obtained in the first solid-liquid separation step is a wet cake having a mother liquor attached thereto, and the high-purity terephthalic acid-containing cake is washed and then subjected to a drying step.
- a high-purity terephthalic acid crystal G of the product is obtained, but the amount of the washing liquid used for washing at this time is 0.2 to 3.0 times by weight of the entire amount of the high-purity terephthalic acid-containing cake. .
- the washing includes suspending wet cake-like terephthalic acid crystals and recovering high-purity terephthalic acid again using a solid-liquid separator.
- the average particle size of the high-purity terephthalic acid obtained by washing the high-purity terephthalic acid-containing cake using the washing liquid having the above-mentioned usage amount is 50 to 150 zm.
- This crude terephthalic acid is dissolved in water, and the 4-carboxybenzaldehyde in the dissolved product is reduced at 285 ° C in the presence of a Group 8 metal catalyst, and the reduced product is flash-evaporated.
- Step crystallization was performed.
- the temperature of the first-stage crystallization tank was 220 ° C
- the temperature of the second-stage crystallization tank was 207 ° C
- the final crystallization conditions were 156 ° C and 0.54 MPa.
- the resulting slurry containing terephthalic acid crystals was subjected to a first solid-liquid separation using a centrifuge at an operating pressure of 0.6 MPa to separate a terephthalic acid cake and a primary separated mother liquor.
- the steam generated from the first and second crystallization tanks was used as a heat source when dissolving the crude terephthalic acid in water (first crystallization).
- the weight ratio of the condensate drained from the tank to the condensate drained from the second crystallization tank was 8: 3).
- a condensate was obtained from the vapor by heat exchange (the concentration of paratoluic acid in the condensate is slightly different for each measurement, but is in the range of 500 to 600 ppm). No.
- the terephthalic acid cake obtained by the solid-liquid separation in 1 was suspended and washed with water as a 49% slurry. Next, the slurry was flash-cooled to normal pressure, and a terephthalic acid cake was obtained using a centrifugal separator under normal pressure. The terephthalic acid cake was dried to obtain high-purity terephthalic acid.
- terephthalic acid was continuously performed for 100 hours using demineralized water as water for dissolving the above crude terephthalic acid.
- terephthalic acid was continuously produced for 500 hours in the same manner as in the Reference Example, except that a mixture of 100 parts by weight of the condensate and 300 parts by weight of demineralized water was used.
- the weight was 135 pm.
- the concentration of paratoluic acid in the primary separated mother liquor was 110 ⁇ ⁇ m.
- Example 1 continuous operation was performed for 2000 hours under the same conditions as in Example 1 except that the temperature of the first crystallization tank was changed to 240 ° C and the temperature of the second crystallization tank was changed to 200 ° C. Was. (The concentration of paratoluic acid in the condensate obtained from the first and second crystallization tanks varies from measurement to measurement, but is in the range of 600 to 1000 ppm.)
- the concentration of paratoluic acid in the high-purity terephthalic acid obtained after lapse of 2000 hours was 180 weight ppm.
- the concentration of paratoluic acid in the primary: ⁇ mother liquor was 1720 ⁇ ⁇ m.
- Example 2 Example 2 was repeated except that a mixture of 100 parts by weight of condensate obtained from the first crystallization tank and the second crystallization tank and 500 parts by weight of demineralized water was used. Under the same conditions as described above, continuous operation was performed for 500 hours.
- the concentration of paratoluic acid in the primary separated mother liquor was 1,250 ppm.
- Example 3 the primary separated mother liquor obtained in the first solid-liquid separation was heated to 60 ° C. After cooling, the precipitated solid was separated and subjected to a second solid-liquid separation to obtain a second separated mother liquor.
- the paratoluic acid concentration of the secondary separated mother liquor obtained after 500 hours in Example 3 was 115 ppm.
- 100 parts by weight of the condensate obtained from the first and second crystallization tanks was paratolylized with a synthetic adsorbent (SEPABEDASSP 825, manufactured by Mitsubishi Chemical Corporation). The continuous operation was performed for 500 hours under the same conditions as in Example 3 except that 500 parts by weight of the secondary separated mother liquor in which the acid concentration was reduced to less than 100 ppm was used.
- the weight was 125 ppin. Also, the concentration of paratoluic acid in the primary separated mother liquor is
- the steam generated in the crystallization step is used as it is, or water is given heat to form steam, which is used for heat exchange with the crude terephthalic acid slurry to heat the crude terephthalic acid slurry Since it is used as a part of the heat source for the crystallization process, the heat energy of the steam generated in the crystallization process can be fully and effectively used.
- the vapor generated in the crystallization process is condensed by heat exchange to form a condensate. Since the condensate is used as a part of the aqueous medium, the condensate can be effectively used.
- the secondary mother liquor When the secondary mother liquor is used as a part of the aqueous medium, the secondary mother liquor can be effectively used.
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Abstract
A method for producing high purity terephthalic acid, characterized in that it comprises conducting pressure-release and cooling in a crystallizing step in a crystallizing vessel (14) to generate steam (H), subjecting the steam to the heat exchange with a crude terephthalic acid slurry (C) to thereby use the steam (H) as a part of the heat source for heating the crude terephthalic acid slurry (C), and condensing the steam generated in the crystallization step by the above heat exchange into a condensate (I) to use the condensate (I) as a part of an aqueous medium (B). The method allows the effective use of an aqueous medium and the steam generated in a crystallization step in combination with the production of the high purity terephthalic acid having a concentration of p-toluic acid limited to a specific range, and also allows the effective use of a condensate from the steam.
Description
明 細 書 高純度テレフタル酸の製造方法 <技術分野 > Description Manufacturing method of high-purity terephthalic acid <Technical field>
この発明は、 高純度テレフタル酸の製造方法に関する。 <背景技術 > The present invention relates to a method for producing high-purity terephthalic acid. <Background technology>
パラキシレンの酸化によって得られる粗テレフタル酸中には、 通常、 4—カル ポキシべンズアルデヒドをはじめとする各種の不純物が比較的多量に含まれてお り、 従来、 これを精製してポリエステルの原料として用いている。 このような粗 テレフタル酸の精製方法としては、 粗テレフタル酸を水に溶解させ、 上記 4一力 ルポキシベンズアルデヒドを還元してパラトルィル酸とし、 テレフタル酸とパラ トルィル酸との水に対する溶解性の差を利用して、 晶析によって分取 ·精製する 方法が行われている。 この晶析の方法としては、 高温高圧状態にある粗テレフタ ル酸水溶液を放圧 ·冷却することによって圧力及び温度を低下させ、 主にテレフ タル酸のみを晶析させる方法が採用される。 The crude terephthalic acid obtained by the oxidation of para-xylene usually contains relatively large amounts of various impurities including 4-carboxybenzaldehyde. Used as a raw material. As a method for purifying such crude terephthalic acid, the crude terephthalic acid is dissolved in water, and the above-mentioned lipoxybenzaldehyde is reduced to paratoluic acid, and the difference in solubility between terephthalic acid and paratoluic acid in water is determined. There is a method that uses crystallization to separate and purify by crystallization. As the crystallization method, a method is employed in which the pressure and temperature are reduced by depressurizing and cooling a crude terephthalic acid aqueous solution in a high-temperature and high-pressure state, and mainly terephthalic acid alone is crystallized.
この晶析法において放圧 ·冷却を行うと、 上記水が蒸発して蒸気が発生する。 この蒸気の利用法としては、 この蒸気を凝縮させて得られる凝縮液を上記水とし てリサイクルすることが特許文献 1に記載されている。 When the pressure is released and cooled in this crystallization method, the water evaporates to generate steam. Patent Literature 1 describes a method of utilizing the steam, in which a condensate obtained by condensing the steam is recycled as the water.
また、 上記の蒸気を上記粗テレフタル酸水溶液を得るための熱源の一部として 用いることが特許文献 2に記載されている。 Patent Document 2 describes that the above-mentioned steam is used as a part of a heat source for obtaining the above-mentioned crude terephthalic acid aqueous solution.
ところで、 テレフタル酸を晶析させたスラリーは、 固液分離され、 高純度テレ フタル酸が得られる。 そして、 このとき得られる分離母液中には、 パラトルィル 酸が多量に含まれている。 このパラトルィル酸は、 酸化反応に供与するとテレフ タル酸となるので、 回収されている。 この回収方法としては上記分離母液を冷却 してパラトルィル酸を多く含有するテレフタル酸を析出させ、 固液分離によって パラトルィル酸を多く含有するテレフタル酸を回収する方法が特許文献 3に記載
されている。 また、 上記分離母液は、 プロセス内の溶解工程の水又は懸洗液とし て用いることが特許文献 4に記載されている。 By the way, the slurry in which terephthalic acid is crystallized is subjected to solid-liquid separation to obtain high-purity terephthalic acid. The separated mother liquor obtained at this time contains a large amount of paratoluic acid. This paratoluic acid is recovered because it is converted to terephthalic acid when it is donated to the oxidation reaction. Patent Document 3 discloses a method for recovering the separated mother liquor, in which terephthalic acid containing a large amount of paratoluic acid is precipitated by cooling the separated mother liquor, and recovering terephthalic acid containing a large amount of paratoluic acid by solid-liquid separation. Have been. Patent Literature 4 describes that the separated mother liquor is used as water or a washing solution in a dissolving step in a process.
[特許文献 1 ] U S 3 5 8 4 0 3 9号公報 [Patent Document 1] US Pat. No. 3,584,039
[特許文献 2 ] 特開平 0 8— 2 2 5 4 8 9号公報 [Patent Document 2] Japanese Patent Application Laid-Open No. 08-2252589
[特許文献 3 ] 特開昭 5 2— 1 2 8 3 4 4号公報 [Patent Document 3] Japanese Patent Application Laid-Open No. Sho 52-1-2283424
[特許文献 4 ] 特開平 0 5— 0 5 8 9 4 8号公報 [Patent Literature 4] Japanese Patent Application Laid-Open No. 05-0-058 948
<発明の開示 > <Disclosure of Invention>
しかしながら、 特許文献 1に記載の方法では、 上記の蒸気を凝縮する必要があ り、 また、 特許文献 2に記載の方法では、 上記の蒸気の凝縮液は最終的に廃棄さ れており、 いずれの場合も、 上記の蒸気を十分に有効利用しているとはいい難い そこで、 この発明は、 晶析工程で発生する蒸気の有効利用を図ることを目的と する。 さらに、 晶析工程で発生する蒸気、 及びこの蒸気の凝縮液の有効利用を図 ることを目的とする。 However, in the method described in Patent Document 1, it is necessary to condense the vapor, and in the method described in Patent Document 2, the condensate of the vapor is finally discarded. In this case, too, it is difficult to say that the above-mentioned steam is sufficiently used effectively. Therefore, an object of the present invention is to make effective use of the steam generated in the crystallization step. It is another object of the present invention to make effective use of the vapor generated in the crystallization process and the condensate of this vapor.
この発明は、 パラキシレンを酸化して得られる粗テレフタル酸を水系媒体に懸 濁してスラリーとし、 次いで加温することにより、 この粗テレフタル酸のスラリ 一を完全溶解させ、 次いで還元処理した後、 晶析槽でテレフタル酸を晶析させ、 得られたテレフタル酸スラリーを第 1固液分離工程にかけて、 高純度テレフタル 酸を製造する方法において、 上記晶析槽での晶析工程において放圧冷却すること により発生する蒸気及び/又はその凝縮液を、 上記第 1固液分離で得られる 1次 分離母液中のパラトルィル酸濃度が 8 0 0〜2 0 0 0重量 p p mとなるように、 上記水系媒体の一部として用いることにより、 上記の課題を解決したのである。 また、 上記晶析工程において放圧冷却により発生する蒸気を、 上記粗テレフタ ル酸のスラリ一と熱交換することにより、 上記晶析工程で発生する蒸気を上記粗 テレフタル酸のスラリーを加温する熱源の一部に用いると共に、 上記熱交換によ つて上記晶析工程で発生する蒸気を凝縮させて凝縮液とし、 上記凝縮液を上記水 系媒体の一部として用いることによつても、 上記の課題を解決することができる
さらに、 上記晶析工程において放圧冷却により癸生する蒸気を、 水と熱交換す ることにより、 上記水を水蒸気にすると共に、 上記晶析工程で発生する蒸気を凝 縮させて凝縮液とし、 上記水蒸気を上記粗テレフタル酸又は高純度テレフタル酸 を製造するための機器又は装置の用役として用い、 上記凝縮液を上記水系媒体の 一部として用いることによつても、 上記の課題を解決することができる。 In the present invention, the crude terephthalic acid obtained by oxidizing para-xylene is suspended in an aqueous medium to form a slurry, and then heated to completely dissolve the slurry of the crude terephthalic acid. In a method for producing high-purity terephthalic acid by subjecting terephthalic acid to crystallization in a crystallization tank and subjecting the obtained terephthalic acid slurry to a first solid-liquid separation step, in the crystallization step in the above-described crystallization tank, the pressure is released and cooled. And / or condensate thereof, so that the concentration of paratoluic acid in the primary separation mother liquor obtained in the first solid-liquid separation becomes 800 to 200 ppm by weight. By using it as a part of the above, the above problem was solved. Further, the steam generated in the crystallization step is heat-exchanged with the crude terephthalic acid slurry to heat the steam generated in the crystallization step to the crude terephthalic acid slurry. In addition to being used as a part of the heat source, the vapor generated in the crystallization step by the heat exchange is condensed into a condensate, and the condensate is used as a part of the aqueous medium. Problem can be solved Further, the steam generated in the crystallization step is subjected to heat exchange with water by heat exchange with water, thereby converting the water into steam and condensing the steam generated in the crystallization step into a condensate. The above-mentioned problem is also solved by using the steam as a utility of an apparatus or an apparatus for producing the crude terephthalic acid or the high-purity terephthalic acid, and using the condensate as a part of the aqueous medium. can do.
さらにまた、 上記水蒸気を上記粗テレフタル酸のスラリ一を加温する熱源の一 部に用いることによつても、 上記の課題を解決することができる。 Furthermore, the above problem can be solved by using the steam as a part of a heat source for heating the slurry of the crude terephthalic acid.
<図面の簡単な説明〉 <Brief description of drawings>
図 1は、 この発明にかかる高純度テレフタル酸の製造工程の例を示すフロー図 であり、 FIG. 1 is a flowchart showing an example of a process for producing high-purity terephthalic acid according to the present invention.
図 2は、 この発明にかかる高純度テレフタル酸の製造工程の他の例を示すフ口 一図である。 FIG. 2 is a schematic diagram showing another example of the process for producing high-purity terephthalic acid according to the present invention.
なお、 図中の符号、 1 1は混合槽、 1 2は第 1熱交換器、 1 3は水添反応器、 1 4は晶析槽、 1 5は第 1固液分離機、 1 6は第 2熱交換器、 1 7は第 3熱交換 器、 1 8は貯蔵タンク、 1 9は冷却槽、 2 0は第 2固液分離機、 Aは粗テレフタ ル酸、 B , B ' は水系媒体、 Cは粗テレフタル酸のスラリー、 Dは粗テレフタル 酸溶液、 Eは還元処理液、 Fはテレフタル酸スラリー、 Gは高純度テレフタル酸 結晶、 Hは蒸気、 Iは凝縮液、 Jは 1次分離母液、 Kはパラトルィル酸含有テレ フタル酸スラリー、 Lは 2次結晶、 Mは 2次分離母液、 Nは凝縮液パージ液、 P は 2次分離母液パージ液を表す。 ぐ発明を実施するための最良の形態 > In the figures, 11 is a mixing tank, 12 is a first heat exchanger, 13 is a hydrogenation reactor, 14 is a crystallization tank, 15 is a first solid-liquid separator, and 16 is 2nd heat exchanger, 17 is 3rd heat exchanger, 18 is storage tank, 19 is cooling tank, 20 is 2nd solid-liquid separator, A is crude terephthalic acid, B and B 'are aqueous Medium, C: crude terephthalic acid slurry, D: crude terephthalic acid solution, E: reduction treatment liquid, F: terephthalic acid slurry, G: high-purity terephthalic acid crystals, H: steam, I: condensate, J: primary Separated mother liquor, K is paratoluic acid-containing terephthalic acid slurry, L is secondary crystal, M is secondary separated mother liquor, N is condensate purge liquid, and P is secondary separated mother liquid purge liquid. BEST MODE FOR CARRYING OUT THE INVENTION>
以下において、 この発明について詳細に説明する。 Hereinafter, the present invention will be described in detail.
この発明にかかる、 高純度テレフタル酸は、 図 1に示す工程を経て製造される 。 まず、 パラキシレンを酸化工程で酸化して粗テレフタル酸 Aを得、 この粗テレ フタル酸 Aを混合槽 1 1で水系媒体 Bに懸濁して粗テレフタル酸のスラリー Cと
する。 次いで、 この粗テレフタル酸スラリー cを所定圧力まで加圧し、 第 1熱交 換器 1 2で加温することにより、 上記粗テレフタル酸 Aを完全に上記水系媒体 B に溶解させて粗テレフタル酸溶液 Dを得る。 次いで、 水添反応器 1 3で還元処理 した後、 この還元処理液 Eを晶析槽 1 4に導入してテレフタル酸を晶析させ、 得 られたテレフタル酸スラリー Fを第 1固液分離機 1 5に導入して第 1固液分離ェ 程にかける。 固形分を回収することにより、 高純度テレフタル酸結晶 Gが得られ る。 この高純度テレフタル酸結晶 Gは、 乾燥して製品として出荷される。 The high-purity terephthalic acid according to the present invention is produced through the steps shown in FIG. First, para-xylene is oxidized in an oxidation step to obtain crude terephthalic acid A, and this crude terephthalic acid A is suspended in an aqueous medium B in a mixing tank 11 to obtain a crude terephthalic acid slurry C. I do. Next, the crude terephthalic acid slurry c is pressurized to a predetermined pressure, and heated in the first heat exchanger 12 to completely dissolve the crude terephthalic acid A in the aqueous medium B to obtain a crude terephthalic acid solution. Get D. Next, after a reduction treatment in a hydrogenation reactor 13, the reduction treatment liquid E is introduced into a crystallization tank 14 to crystallize terephthalic acid, and the obtained terephthalic acid slurry F is converted into a first solid-liquid separator. Introduced in 15 and subjected to the first solid-liquid separation process. By recovering the solid content, high-purity terephthalic acid crystals G can be obtained. This high-purity terephthalic acid crystal G is dried and shipped as a product.
上記粗テレフタル酸 A中には、 不純物として酸化工程での副生成物である 4一 カノレポキシベンズァノレデヒ ドが 1 0 0 0〜5 0 0 0 p p m含まれる。 この 4一力 ルポキシベンズアルデヒ ドは、 上記の水添反応器 1 3において、 水素ガスを用い て還元処理することによって、 パラトルィル酸となる。 このパラトルィル酸は、 テレフタル酸より水に対する溶解度が大きいため、 上記還元処理液 Eを晶析させ ると、 まず、 テレフタル酸が優先的に析出する。 このため、 パラトルィル酸が析 出しにくい条件でテレフタル酸を析出させて回収することにより、 高純度テレフ タル酸が製造される。 The crude terephthalic acid A contains 100 to 500 ppm as by-products in the oxidation step as impurities. In the hydrogenation reactor 13, the above-mentioned lipoxybenzaldehyde is reduced to paratoluic acid by a reduction treatment using hydrogen gas. Since this paratoluic acid has a higher solubility in water than terephthalic acid, when the above-mentioned reduction treatment solution E is crystallized, first, terephthalic acid is preferentially precipitated. Therefore, high-purity terephthalic acid is produced by precipitating and recovering terephthalic acid under conditions in which paratoluic acid is difficult to precipitate.
上記水系媒体とは、 上記の粗テレフタル酸を用いて高純度テレフタル酸を製造 する際に使用される媒体をいい、 具体的には、 水を意味す.る。 The aqueous medium refers to a medium used in producing high-purity terephthalic acid using the above crude terephthalic acid, and specifically refers to water.
上記の晶析槽 1 4での晶析は、 上記還元処理液 Eの圧力より低い圧力条件に設 定した晶析槽 1 4に上記還元処理液 Eを導入し、 ここで放圧させると共に、 これ に伴って冷却させる (以下、 放圧 ·冷却の操作を 「放圧冷却」 と略称する。 ) 方 法である。 これにより、 テレフタル酸が晶析される。 In the crystallization in the crystallization tank 14, the reduction treatment liquid E was introduced into the crystallization tank 14 set at a pressure lower than the pressure of the reduction treatment liquid E, and the pressure was released. This is followed by cooling (hereinafter the operation of pressure relief / cooling is abbreviated as “pressure relief cooling”). Thereby, terephthalic acid is crystallized.
この晶析工程において、 放圧冷却を行うと、 還元処理液 E中の水系媒体の一部 が気化し、 水系媒体の蒸気 Hが発生する。 この蒸気 Hは、 上記粗テレフタル酸の スラリー Cを流す配管に設けられた第 2熱交換器 1 6に熱源として送られる。 こ れにより、 上記粗テレフタル酸のスラリー Cと蒸気 Hとが熱交換され、 上記晶析 工程で発生する蒸気 Hを、 上記粗テレフタル酸のスラリーを加温する熱源の一部 に用いることとなる。 上記の蒸気 Hを上記粗テレフタル酸のスラリー Cの熱源の —部に用いることにより、 蒸気 Hの熱エネルギーを有効に利用することができる
と共に、 上記第 1熱交換器 1 2での加熱負荷を低減できる。 また、 このとき、 蒸 気 Hは、 上記の熱交換によって凝縮されて凝縮液 Iが発生する。 In the crystallization step, when depressurized cooling is performed, a part of the aqueous medium in the reduction treatment liquid E is vaporized, and steam H of the aqueous medium is generated. This steam H is sent as a heat source to the second heat exchanger 16 provided in the pipe through which the crude terephthalic acid slurry C flows. As a result, the crude terephthalic acid slurry C and the steam H undergo heat exchange, and the steam H generated in the crystallization step is used as a part of a heat source for heating the crude terephthalic acid slurry. . By using the above-mentioned steam H for the negative part of the heat source of the above crude terephthalic acid slurry C, the heat energy of the steam H can be used effectively. At the same time, the heating load on the first heat exchanger 12 can be reduced. At this time, the steam H is condensed by the above heat exchange to generate a condensate I.
また、 図 2に示すように、 上記晶析槽 1 4での晶析工程において放圧冷却する ことにより発生する蒸気 Hを、 第 3熱交換器 1 7で水 W 1と熱交換することによ り、 上記水 W 1を水蒸気 W 2とし、 次いで、 この水蒸気 W 2を、 上記粗テレフタ ル酸のスラリー Cを加熱するための第 2熱交換器 1 6に熱交換用媒体として使用 する。 これにより、 上記水蒸気 W 2を、 上記粗テレフタル酸のスラリー Cを加温 する熱源の一部に用いることができる。 このため、 結果として、 蒸気 Hの熱エネ ルギーを有効に利用することができると共に、 上記第 1熱交換器 1 2での加熱負 荷を低減することができる。 また、 このとき、 蒸気 Hは、 上記の熱交換によって 凝縮されて凝縮液 Iが発生する。 Further, as shown in FIG. 2, steam H generated by depressurizing and cooling in the crystallization step in the crystallization tank 14 is heat-exchanged with water W 1 in the third heat exchanger 17. Thus, the water W1 is used as the steam W2, and the steam W2 is used as a heat exchange medium in the second heat exchanger 16 for heating the crude terephthalic acid slurry C. Thus, the steam W 2 can be used as a part of a heat source for heating the crude terephthalic acid slurry C. As a result, as a result, the heat energy of the steam H can be effectively used, and the heating load in the first heat exchanger 12 can be reduced. Further, at this time, the vapor H is condensed by the above heat exchange to generate a condensate I.
なお、 上記の水蒸気 W 2は、 第 2熱交換器 1 6の熱交換用媒体として使用する だけでなく、 その他、 上記粗テレフタル酸又は高純度テレフタル酸を製造するた めの機器又は装置の用役として用いることができる。 このような機器又は装置と しては、 熱交換器、 乾燥機、 ェジェクタ一、 スチームタービン等があげられる。 上記の水蒸気 W 2を経由して、 蒸気 Hの熱を粗テレフタル酸のスラリー Cに伝 達させることにより、 高温高圧の苛酷な条件であるために、 耐食性に優れたチタ ン材を採用した機器に対して、 晶析槽 1 4から発生するガスに含まれる水素によ るチタン材の脆化を防ぐという特徴を発揮することができる。 The above-mentioned water vapor W2 is used not only as a heat exchange medium for the second heat exchanger 16 but also for other equipment or apparatus for producing the above crude terephthalic acid or high-purity terephthalic acid. Can be used as a role. Examples of such equipment or devices include heat exchangers, dryers, ejectors, steam turbines, and the like. By using the above-mentioned steam W2 to transfer the heat of steam H to the crude terephthalic acid slurry C, the equipment uses a titanium material with excellent corrosion resistance because of severe conditions of high temperature and high pressure. On the other hand, a feature of preventing the titanium material from being embrittled by hydrogen contained in the gas generated from the crystallization tank 14 can be exhibited.
また、 晶析工程の放圧冷却により発生した水系媒体の蒸気 Hは、 これを凝縮さ せることなく混合槽 1 1やそれに至る配管あるいは水添反応槽 1 3やそれに至る 配管等の原料のテレフタル酸が溶解するまでのいずれかの部位に導入しても良い 。 これにより蒸気 Hの持つエネルギーをテレフタル酸の溶解のために利用できる と共に、 蒸気そのものを水系媒体として再利用することができる。 In addition, the vapor H of the aqueous medium generated by the depressurized cooling in the crystallization process is used as a raw material for the terephthalate of the mixing tank 11 and the piping to reach it or the hydrogenation reaction tank 13 and the piping to reach it without condensing it. It may be introduced into any site until the acid is dissolved. This makes it possible to use the energy of the steam H for dissolving terephthalic acid and to reuse the steam itself as an aqueous medium.
上記晶析槽 1 4の数については、 図 1及び図 2においては、 1つの場合を表示 したが、 2つ以上の複数の晶析槽 1 4を直列に連結することが好ましい。 複数の 晶析槽 1 4を直列に連結することにより、 還元処理液 Eの圧力から第 1固液分離 機 1 5の設定圧力へ、 1段階の放圧冷却を行うだけでなく、 圧力低減を複数に分
けて放圧低減を行うことが可能となる。 このようにすると、 各晶析槽で晶析がよ り温和に行うことができ、 不純物であるパラトルィル酸のテレフタル酸結晶中へ の取り込みを抑制することができ、 また、 テレフタル酸結晶の粒径分布をコント ロールすることができる。 Although the number of the crystallization tanks 14 is one in FIGS. 1 and 2, it is preferable to connect two or more crystallization tanks 14 in series. By connecting a plurality of crystallization tanks 14 in series, it is possible to not only perform one-step depressurized cooling from the pressure of the reducing solution E to the set pressure of the first solid-liquid separator 15 but also reduce the pressure. Minutes Thus, the pressure release can be reduced. In this way, the crystallization can be performed more mildly in each crystallization tank, the incorporation of the impurity paratoluic acid into the terephthalic acid crystals can be suppressed, and the particle size of the terephthalic acid crystals can be reduced. The distribution can be controlled.
複数の晶析槽を直列に連結して晶析するにあたり、 それぞれの晶析槽に熱交換 器を設け、 後段の熱交換器から順次、 粗テレフタル酸のスラリー Cを加熱するこ とで、 効率よく加熱できる。 ここで、 効率よく熱エネルギーを回収して粗テレフ タル酸のスラリー Cを還元処理操作温度に近い高温域まで加熱するために、 還元 処理と第 1晶析の温度差を 5 0 °C以下にすることが好ましい。 In order to conduct crystallization by connecting multiple crystallization tanks in series, a heat exchanger is installed in each crystallization tank, and the crude terephthalic acid slurry C is heated in order from the heat exchanger at the subsequent stage to improve efficiency. Can be heated well. Here, in order to efficiently recover thermal energy and heat the crude terephthalic acid slurry C to a high temperature region close to the reduction operation temperature, the temperature difference between the reduction treatment and the first crystallization was reduced to 50 ° C or less. Is preferred.
上記晶析工程において放圧冷却するに伴い、 蒸気 Hにはパラトルィル酸の一部 も同伴しており、 上記の熱交換で生じる凝縮液 Iの成分にも、 パラトルィル酸を 含有しているが、 直接又は何らかの処理を行って間接的に、 上記水系媒体 Bの一 部として用いることができる。 このため、 上記凝縮液 Iを貯蔵タンク 1 8を経由 して、 混合槽 1 1に送ってもよい。 また、 蒸留処理や膜処理をして水系媒体を回 収し、 この回収水系媒体を用いてもよい。 これにより、 新しい水系媒体 Bの使用 量を削減することができると共に、 凝縮液 Iの再利用が可能となり、 ユーティリ ティ設備の縮小及び排水処理負荷の低減を図ることができる。 Along with the depressurized cooling in the crystallization step, a part of paratoluic acid is also entrained in the steam H, and the component of the condensate I generated by the above heat exchange also contains paratoluic acid. It can be used as a part of the aqueous medium B directly or indirectly by performing some processing. Therefore, the condensate I may be sent to the mixing tank 11 via the storage tank 18. Further, the aqueous medium may be recovered by performing a distillation treatment or a membrane treatment, and the recovered aqueous medium may be used. As a result, the amount of the new aqueous medium B used can be reduced, the condensate I can be reused, and the utility equipment and the wastewater treatment load can be reduced.
ところで、 上記第 1固液分離工程によって得られる 1次分離母液: 1、 すなわち 、 第 1固液分離機 1 5で高純度テレフタル酸結晶 Gを分取した残りの母液は、 冷 却槽 1 9に送られて冷却工程にかけられる。 上記第 1固液分離工程に送られたテ レフタル酸スラリーの温度は 1 2 0〜 1 7 0 °Cであり、 この上記第 1固液分離ェ 程から排出される 1次分離母液 Jも同様の温度を有する。 上記冷却工程において は、 この 1次分離母液 Jを放圧冷却することにより、 4 0〜 6 0 °C付近まで濃縮 及び冷却され、 パラトルィル酸を多く含有する低純度なテレフタル酸結晶が析出 する。 このときの圧力は、 減圧装置を用いて、 1気圧未満のいわゆる負圧にする ことが好ましい。 また、 上記低純度なテレフタル酸結晶を析出するためには、 1 次分離母液 Jに熱を加えて濃縮したり冷媒を用いて熱交換して冷却したりしても よい。
この濃縮冷却工程で得られるパラトルイル酸含有テレフタル酸スラリー Kは、 第 2固液分離機 2 0に送られ、 2次結晶 Lと 2次分離母液 Mを分離する第 2固液 分離工程が行われる。 By the way, the primary separated mother liquor obtained in the first solid-liquid separation step: 1, that is, the remaining mother liquor obtained by fractionating high-purity terephthalic acid crystals G in the first solid-liquid separator 15 is provided in a cooling tank 19 To be subjected to a cooling process. The temperature of the terephthalic acid slurry sent to the first solid-liquid separation step is 120 to 170 ° C, and the primary separation mother liquor J discharged from the first solid-liquid separation step is the same. Having a temperature of In the cooling step, the primary separated mother liquor J is depressurized and cooled to be concentrated and cooled to about 40 to 60 ° C., and low-purity terephthalic acid crystals containing a large amount of paratoluic acid are precipitated. The pressure at this time is preferably adjusted to a so-called negative pressure of less than 1 atm using a pressure reducing device. In order to precipitate the low-purity terephthalic acid crystals, the primary separation mother liquor J may be concentrated by applying heat or cooled by heat exchange using a refrigerant. The paratoluic acid-containing terephthalic acid slurry K obtained in the concentration and cooling step is sent to a second solid-liquid separator 20 to perform a second solid-liquid separation step of separating a secondary crystal L and a secondary separation mother liquor M. .
この 2次結晶 Lは、 パラトルィル酸を多量に含有する固形分であるので、 これ を上記酸化反応に供与することにより、 テレフタル酸の原料とすることができる 。 また、 上記 2次分離母液 Mの少なくとも一部は、 パラトルィル酸を含有してい るが、 上記 1次分離母液 Jに比べると多量のパラトルィル酸が除去されており、 直接又は何らかの処理を行って間接的に、 混合槽 1 1に送って、 上記水系媒体 B の一部として使用してもよい。 これにより、 新しい水系媒体 Bの使用量をさらに 削減することができると共に、 2次分離母液 Mの再利用が可能となり、 新しい水 系媒体に関わるユーティリティ設備の縮小及び排水量低減に伴ない排水処理負荷 の低減を図ることができる。 Since the secondary crystal L is a solid content containing a large amount of paratoluic acid, it can be used as a raw material for terephthalic acid by donating it to the above oxidation reaction. In addition, at least a portion of the second separated mother liquor M contains paratoluic acid, but a larger amount of paratoluic acid has been removed compared to the first separated mother liquor J. Alternatively, it may be sent to the mixing tank 11 and used as a part of the aqueous medium B. As a result, the amount of the new aqueous medium B can be further reduced, and the secondary separated mother liquor M can be reused. Can be reduced.
晶析工程で発生する蒸気 H及び 又はその凝縮液 Iや 2次分離母液 Mには、 パ ラトルィル酸が含まれる。 このため、 凝縮液 Iや 2次分離母液 Mの直接的な再利 用量を多くしすぎると、 粗テレフタル酸のスラリー C中に含有されるパラトルイ ル酸量が増大してしまい、 結果として、 高純度テレフタル酸結晶 G中のパラトル ィル酸含有濃度が増大してしまうこととなる。 このため、 上記水系媒体中の上記 凝縮液 I及びノ又は上記 2次分離母液 Mの使用割合は、 上記高純度テレフタル酸 結晶 G中に含まれるパラトルィル酸の濃度を 5 0〜 2 0 0 p p m、 好ましくは 1 0 0〜 1 5 0 p p mに維持するために、 上記第 1固液分離で得られる 1次分離母 液 J中のパラトルィル酸濃度を、 8 0 0〜 2 0 0 0重量!) p mとなるように用い ることが好ましい。 テレフタル酸結晶 G中に含まれるパラトルィル酸の濃度が 2 0 0 p を超えると、 製品としての高純度テレフタル酸にとっては不純物が多 くなりすぎる。 また、 5 0 p p m未満は品質過剰である。 The vapor H and / or its condensate I and the secondary mother liquor M generated in the crystallization process contain paratoluic acid. For this reason, if the direct re-use amount of the condensate I or the secondary separation mother liquor M is too large, the amount of paratoluic acid contained in the crude terephthalic acid slurry C increases, and as a result, This means that the concentration of paratoluic acid in the pure terephthalic acid crystal G will increase. For this reason, the usage ratio of the condensate I and the secondary separation mother liquor M in the aqueous medium is such that the concentration of paratoluic acid contained in the high-purity terephthalic acid crystal G is 50 to 200 ppm, Preferably, to maintain the concentration at 100 to 150 ppm, the concentration of paratoluic acid in the primary separated mother liquor J obtained by the first solid-liquid separation is 800 to 2000% by weight! ) It is preferable to use p so as to be p m. If the concentration of paratoluic acid contained in terephthalic acid crystal G exceeds 200 p, impurities will be too large for high-purity terephthalic acid as a product. In addition, if it is less than 50 ppm, the quality is excessive.
上記凝縮液 I及び上記 2次分離母液 Mのいずれも共に直接、 再利用をする場合 、 凝縮液 Iを優先的に用い、 2次分離母液 Mは、 1次分離母液 J中のパラトルィ ル酸濃度見合いで使用量を決定する。 また、 上記凝縮液 Iと上記 2次分離母液 M とのいずれか一方が蒸留や膜分離、 合成吸着剤の使用等の処理により、 パラトル
ィル酸の濃度を低減させる場合、 回収処理側を優先的に用い、 直接再使用する側 は、 1次分離母液 J中のパラトルィル酸濃度見合いで使用量を決定する。 いずれ にしても、 高純度テレフタル酸製品品質が許容できる範囲内でできるだけ、 凝縮 液 Iや 2次分離母液 Mの再利用を実施することにより、 新しい水系媒体 Bの使用 量の削減、 ユーティリティ設備の縮小、 排水処理負荷の低減を達成することがで きる。 When both the condensate I and the secondary separation mother liquor M are directly reused, the condensate I is preferentially used, and the secondary separation mother liquor M has a paratoluic acid concentration in the primary separation mother liquor J. Determine the amount of use in proportion. In addition, one of the condensate I and the secondary separation mother liquor M is treated by distillation, membrane separation, use of a synthetic adsorbent, etc. When reducing the concentration of silicic acid, the recovery side should be used preferentially, and the side directly reused should determine the amount to be used based on the paratoluic acid concentration in the primary separation mother liquor J. In any case, by reusing the condensate I and the secondary mother liquor M as much as possible within the acceptable range of high-purity terephthalic acid product quality, the amount of new aqueous medium B used can be reduced and utility equipment can be reduced. It is possible to achieve reduction in size and load on wastewater treatment.
上記の 1次分離母液 J中に含まれるパラトルイル酸の濃度を上記範囲に調整す るためには、 上記凝縮液 I及び上記 2次分離母液 Mの混合割合の条件以外に、 下 記に示すような具体的な条件が必要となる。 In order to adjust the concentration of paratoluic acid contained in the primary separated mother liquor J to the above range, besides the conditions of the mixing ratio of the condensate I and the secondary separated mother liquor M, as shown below: Specific conditions are required.
まず、 上記粗テレフタル酸のスラリー Cのスラリー濃度を 1 0〜5 0重量0 /0と する必要がある。 濃度が低すぎてもよいが製造効率の面から好ましくない場合が ある。 また、 濃度が高すぎると、 閉塞等、 運転そのものに支障をきたす場合があ る。 First, it is necessary to obtain a slurry concentration of 1 0-5 0 weight 0/0 of the slurry C in the crude terephthalic acid. Although the concentration may be too low, it may not be preferable in terms of production efficiency. If the concentration is too high, the operation itself may be hindered due to blockage or the like.
また、 上記第 1固液分離工程によって得られる高純度テレフタル酸結晶 Gは、 母液が付着した、 湿ったケーキ状であり、 この高純度テレフタル酸含有ケーキを 洗浄し、 その後、 乾燥工程を経ることにより、 製品の高純度テレフタル酸結晶 G が得られるが、 このときの洗浄に使用される洗浄液の使用量は、 上記高純度テレ フタル酸含有ケーキ全量の 0 . 2〜3 . 0重量倍である。 これは、 上記洗浄液の 使用量によって、 製品としての高純度テレフタル酸結晶 Gに含まれるパラトルイ ル酸の含有量が異なるからである。 なお、 上記洗浄には、 湿ったケーキ状のテレ フタル酸結晶を懸濁処理し、 再度、 固液分離機を用いて高純度テレフタル酸を回 収することも含まれる。 Further, the high-purity terephthalic acid crystal G obtained in the first solid-liquid separation step is a wet cake having a mother liquor attached thereto, and the high-purity terephthalic acid-containing cake is washed and then subjected to a drying step. As a result, a high-purity terephthalic acid crystal G of the product is obtained, but the amount of the washing liquid used for washing at this time is 0.2 to 3.0 times by weight of the entire amount of the high-purity terephthalic acid-containing cake. . This is because the content of paratoluic acid contained in the high-purity terephthalic acid crystal G as a product varies depending on the amount of the above-mentioned cleaning solution used. The washing includes suspending wet cake-like terephthalic acid crystals and recovering high-purity terephthalic acid again using a solid-liquid separator.
上記の範囲の使用量の洗浄液を用いて、 上記高純度テレフタル酸含有ケーキを 洗浄することによって、 得られる上記高純度テレフタル酸の平均粒径は、 5 0〜 1 5 0 z mとなる。 ぐ実施例 > The average particle size of the high-purity terephthalic acid obtained by washing the high-purity terephthalic acid-containing cake using the washing liquid having the above-mentioned usage amount is 50 to 150 zm. Examples>
[参考例]
酢酸を溶媒とし、 C o/Mn/B rを含む触媒存在下で圧力 1. 5 MP aでパ ラキシレンを液相酸化してテレフタル酸含有のスラリーを生成した。 このスラリ 一はェジェクタ一を用いて大気圧以下 (0. 05MP a) に減圧して 90°Cにフ ラッシュ冷却し、 得られたテレフタル酸スラリ一をロータリ一バキュームフィル ターを用いて、 固液分離及び酢酸による洗浄を行い、 次いで得られたウエットケ ーキを乾燥させて、 4一力ルポキシベンズアルデヒドの濃度が 2300重量 mである粗テレフタル酸結晶を得た。 [Reference example] Paraxylene was subjected to liquid phase oxidation at a pressure of 1.5 MPa using acetic acid as a solvent in the presence of a catalyst containing Co / Mn / Br to produce a terephthalic acid-containing slurry. This slurry was depressurized to below atmospheric pressure (0.05MPa) using an ejector, flash-cooled to 90 ° C, and the resulting terephthalic acid slurry was solid-liquid separated using a rotary vacuum filter. Separation and washing with acetic acid were carried out, and the obtained wet cake was dried to obtain crude terephthalic acid crystals having a concentration of 4% lipoxybenzaldehyde of 2300 wt.m.
この粗テレフタル酸を水に溶解し、 この溶解物中の 4—カルボキシベンズアル デヒドを第 8族金属触媒の存在下、 285°Cの温度条件で還元し、 この還元処理 物をフラッシュ蒸発で 5段晶析した。 第 1段の晶析槽温度は、 220°C、 第 2段 の晶析槽温度は 207°C、 最終晶析条件は、 156°C、 0. 54MP aであった 。 これにより得られたテレフタル酸結晶を含有するスラリーを、 遠心分離機を用 いて操作圧力 0. 6MP aで第 1の固液分離を行って、 テレフタル酸ケーキと 1 次分離母液とに分離した。 This crude terephthalic acid is dissolved in water, and the 4-carboxybenzaldehyde in the dissolved product is reduced at 285 ° C in the presence of a Group 8 metal catalyst, and the reduced product is flash-evaporated. Step crystallization was performed. The temperature of the first-stage crystallization tank was 220 ° C, the temperature of the second-stage crystallization tank was 207 ° C, and the final crystallization conditions were 156 ° C and 0.54 MPa. The resulting slurry containing terephthalic acid crystals was subjected to a first solid-liquid separation using a centrifuge at an operating pressure of 0.6 MPa to separate a terephthalic acid cake and a primary separated mother liquor.
5段晶析の際に発生する蒸気のうち、 第 1晶析槽と第 2晶析槽から発生した蒸 気は、 粗テレフタル酸を水に溶解する際の熱源として用いた (第 1晶析槽から抜 き出した凝縮液と、 第 2晶析槽から抜き題した凝縮液の重量比は 8 : 3であった ) 。 また、 このとき蒸気は熱交換により凝縮液が得られた (凝縮液のパラトルィ ル酸濃度は、 測定毎に若干異なるが、 500〜600 p pmの範囲である) 。 第 Of the steam generated during the five-stage crystallization, the steam generated from the first and second crystallization tanks was used as a heat source when dissolving the crude terephthalic acid in water (first crystallization). The weight ratio of the condensate drained from the tank to the condensate drained from the second crystallization tank was 8: 3). At this time, a condensate was obtained from the vapor by heat exchange (the concentration of paratoluic acid in the condensate is slightly different for each measurement, but is in the range of 500 to 600 ppm). No.
1の固液分離により得られたテレフタル酸ケーキは、 水を用いて 49%のスラリ 一として懸濁洗浄を行った。 次いでスラリーを常圧までフラッシュ冷却した後、 常圧下で遠心分離器を用いてテレフタル酸ケーキを得た。 このテレフタル酸ケー キを乾燥して、 高純度テレフタル酸を得た。 The terephthalic acid cake obtained by the solid-liquid separation in 1 was suspended and washed with water as a 49% slurry. Next, the slurry was flash-cooled to normal pressure, and a terephthalic acid cake was obtained using a centrifugal separator under normal pressure. The terephthalic acid cake was dried to obtain high-purity terephthalic acid.
上記の粗テレフタル酸を溶解する水として、 脱塩水を用いテレフタル酸の製造 を 100時間連続して行った。 The production of terephthalic acid was continuously performed for 100 hours using demineralized water as water for dissolving the above crude terephthalic acid.
100時間経過後に得られた高純度テレフタル酸中のパラトルィル酸の濃度は The concentration of paratoluic acid in high-purity terephthalic acid obtained after 100 hours has passed
95重量 p であった。 また、 1次分離母液中のパラトルィル酸の濃度は、 9It was 95 weight p. The concentration of paratoluic acid in the primary separated mother liquor was 9%.
26 p p mであった。
[実施例 1 ] 26 ppm. [Example 1]
上記参考例に引き続き、 上記凝縮液 100重量部に対し、 脱塩水 300重量部 を混合したものを用いた以外は参考例と同様に、 テレフタル酸の製造を 500時 間連続して行った。 Following the above Reference Example, terephthalic acid was continuously produced for 500 hours in the same manner as in the Reference Example, except that a mixture of 100 parts by weight of the condensate and 300 parts by weight of demineralized water was used.
500時間経過後に得られた高純度テレフタル酸中のパラトルィル酸の濃度は The concentration of paratoluic acid in the high-purity terephthalic acid obtained after 500 hours has passed
1 35重量 p pmであった。 また、 1次分離母液中のパラトルィル酸の濃度は、 1 1 70 ρ ρ mであった。 The weight was 135 pm. The concentration of paratoluic acid in the primary separated mother liquor was 110 ρ ρm.
[実施例 2] [Example 2]
上記実施例 1に引き続き、 第 1晶析槽の温度を 240°C、 第 2晶析槽の温度を 200°Cに変更した以外は実施例 1と同様の条件で 2000時間連続運転を行つ た。 (第 1及び第 2晶析槽から得られた凝縮液のパラトルィル酸濃度は、 測定毎 に若千異なるが、 600〜1000 p pmの範囲である) Following Example 1 above, continuous operation was performed for 2000 hours under the same conditions as in Example 1 except that the temperature of the first crystallization tank was changed to 240 ° C and the temperature of the second crystallization tank was changed to 200 ° C. Was. (The concentration of paratoluic acid in the condensate obtained from the first and second crystallization tanks varies from measurement to measurement, but is in the range of 600 to 1000 ppm.)
2000時間経過後に得られた高純度テレフタル酸中のパラトルィル酸の濃度 は 1 80重量 p pmであった。 また、 1次:^離母液中のパラトルィル酸の濃度は 、 1720 ρ ρ mであった。 The concentration of paratoluic acid in the high-purity terephthalic acid obtained after lapse of 2000 hours was 180 weight ppm. The concentration of paratoluic acid in the primary: ^ mother liquor was 1720 ρ ρ m.
[実施例 3] [Example 3]
上記実施例 2に引き続き、 第 1晶析槽及び第 2晶析槽から得られた凝縮液 10 0重量部に対して、 脱塩水 500重量部を混合したものを用いた以外は、 実施例 2と同様の条件で 500時間連続運転を行なつた。 Example 2 Example 2 was repeated except that a mixture of 100 parts by weight of condensate obtained from the first crystallization tank and the second crystallization tank and 500 parts by weight of demineralized water was used. Under the same conditions as described above, continuous operation was performed for 500 hours.
500時間経過後に得られた高純度テレフタル酸中のパラトルィル酸の濃度は The concentration of paratoluic acid in the high-purity terephthalic acid obtained after 500 hours has passed
140重量 p pmであった。 また、 1次分離母液中のパラトルィル酸の濃度は、 1 250 p p mであった。 140 weight ppm. The concentration of paratoluic acid in the primary separated mother liquor was 1,250 ppm.
[実施例 4] [Example 4]
上記実施例 3において、 第 1の固液分離で得られた 1次分離母液は、 60°Cに
冷却後、 析出した固体を分離した後、 第 2の固液分離に付し、 2次分離母液を得 た。 実施例 3で 5 0 0時間経過後に得られた 2次分離母液のパラトルィル酸濃度 は、 1 1 5 O p p mであった。 上記実施例 3に引き続き、 第 1晶析槽及ぴ第 2晶 析槽から得られた凝縮液 1 0 0重量部に対して、 合成吸着剤 (三菱化学株式会社 製 S E P A B E D A S S P 8 2 5 ) によりパラトルィル酸濃度を 1 0 p p m未満に低減した 2次分離母液 5 0 0重量部混合したものを用いた以外は、 実施 例 3と同様の条件で 5 0 0時間連続運転を行なった。 In Example 3 above, the primary separated mother liquor obtained in the first solid-liquid separation was heated to 60 ° C. After cooling, the precipitated solid was separated and subjected to a second solid-liquid separation to obtain a second separated mother liquor. The paratoluic acid concentration of the secondary separated mother liquor obtained after 500 hours in Example 3 was 115 ppm. Continuing with Example 3 above, 100 parts by weight of the condensate obtained from the first and second crystallization tanks was paratolylized with a synthetic adsorbent (SEPABEDASSP 825, manufactured by Mitsubishi Chemical Corporation). The continuous operation was performed for 500 hours under the same conditions as in Example 3 except that 500 parts by weight of the secondary separated mother liquor in which the acid concentration was reduced to less than 100 ppm was used.
5 0 0時間経過後に得られた高純度テレフタル酸中のパラトルィル酸の濃度は The concentration of paratoluic acid in the high-purity terephthalic acid obtained after 500 hours has passed
1 2 5重量 p p inであった。 また、 1次分離母液中のパラトルィル酸の濃度は、The weight was 125 ppin. Also, the concentration of paratoluic acid in the primary separated mother liquor is
1 1 0 0 p p mでめつ 7こ。 本発明を詳細にまた特定の実施態様を参照して説明したが、 本発明の精神と範 囲を逸脱することなく様々な変更や修正を加えることができることは当業者にと つて明らかである。 1 1 0 0 7 Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
本出願は、 2003年 1月 8日出願の日本特許出願(特願 2003— 002269) に基づく ものであり、 その内容はここに参照として取り込まれる。 く産業上の利用可能性 > This application is based on a Japanese patent application filed on Jan. 8, 2003 (Japanese Patent Application No. 2003-002269), the contents of which are incorporated herein by reference. Industrial applicability>
この発明によると、 晶析工程で発生する蒸気をそのまま用いて、 又は水に熱を 与えて水蒸気とし、 これを用いて粗テレフタル酸のスラリーと熱交換して、 粗テ レフタル酸のスラリーを加熱するための熱源の一部として用いるので、 晶析工程 で発生する蒸気のもつ熱エネルギーを十分に有効利用できる。 According to the present invention, the steam generated in the crystallization step is used as it is, or water is given heat to form steam, which is used for heat exchange with the crude terephthalic acid slurry to heat the crude terephthalic acid slurry Since it is used as a part of the heat source for the crystallization process, the heat energy of the steam generated in the crystallization process can be fully and effectively used.
さらに、 晶析工程で発生する蒸気は、 熱交換によって凝縮して凝縮液となる。 この凝縮液を水系媒体の一部として用いるので、 凝縮液の有効利用を図ることが できる。 Furthermore, the vapor generated in the crystallization process is condensed by heat exchange to form a condensate. Since the condensate is used as a part of the aqueous medium, the condensate can be effectively used.
また、 2次母液を水系媒体の一部として用いる場合、 この 2次母液も有効利用 を図ることができる。
When the secondary mother liquor is used as a part of the aqueous medium, the secondary mother liquor can be effectively used.
Claims
1 . パラキシレンを酸化して得られる粗テレフタル酸を水系媒体に懸濁し てスラリーとし、 次いで加温することにより、 この粗テレフタル酸のスラリーを 完全溶解させ、 次いで還元処理した後、 晶析槽でテレフタル酸を晶析させ、 得ら れたテレフタル酸スラリ一を第 1固液分離工程にかけて、 高純度テレフタル酸を 製造する方法において、 1. The crude terephthalic acid obtained by oxidizing para-xylene is suspended in an aqueous medium to form a slurry, which is then heated to completely dissolve the crude terephthalic acid slurry. A method for producing high-purity terephthalic acid by subjecting the obtained terephthalic acid slurry to a first solid-liquid separation step,
上記晶析槽での晶析工程において放圧冷却することにより発生する蒸気及び/ 又はその凝縮液を、 上記第 1固液分離で得られる 1次分離母液中のパラトルィル 酸濃度が 8 0 0〜 2 0 0 0重量 p p mとなるように、 上記水系媒体の一部として 用いることを特徴とする高純度テレフタル酸の製造方法。 In the crystallization step in the crystallization tank, the vapor and / or the condensate generated by depressurizing and cooling the paratolylic acid concentration in the primary separated mother liquor obtained in the first solid-liquid separation is 800- A method for producing high-purity terephthalic acid, which is used as a part of the aqueous medium so as to have a concentration of 2000 ppm by weight.
2 . 上記晶析工程において放圧冷却により発生する蒸気を、 上記粗テレフ タル酸のスラリーと熱交換することにより、 上記晶析工程で発生する蒸気を上記 粗テレフタル酸のスラリーを加温する熱源の一部に用いると共に、 上記熱交換に よつて上記晶析工程で発生する蒸気を凝縮させて凝縮液とし、 2. A heat source that heats the steam generated in the crystallization step by heating the crude terephthalic acid slurry by exchanging heat with the crude terephthalic acid slurry in the crystallization step. As well as condensing the vapor generated in the crystallization step by the heat exchange into a condensate,
上記凝縮液を上記水系媒体の一部として用いることを特徴とする請求の範囲第 1項記載の高純度テレフタル酸の製造方法。 2. The method for producing high-purity terephthalic acid according to claim 1, wherein the condensate is used as a part of the aqueous medium.
3 . 上記晶析工程において放圧冷却により発生する蒸気を、 水と熱交換す ることにより、 上記水を水蒸気にすると共に、 上記晶析工程で発生する蒸気を凝 縮させて凝縮液とし、 3. The steam generated by the depressurized cooling in the crystallization step is heat-exchanged with water to convert the water into steam, and the steam generated in the crystallization step is condensed into a condensate.
上記水蒸気を、 上記粗テレフタル酸又は高純度テレフタル酸を製造するための 機器又は装置の用役として用い、 The steam is used as a utility of an apparatus or an apparatus for producing the crude terephthalic acid or the high-purity terephthalic acid,
上記凝縮液を上記水系媒体の一部として用いることを特徴とする請求の範囲第 1項記載の高純度テレフタル酸の製造方法。 2. The method for producing high-purity terephthalic acid according to claim 1, wherein the condensate is used as a part of the aqueous medium.
4 . 上記水蒸気を、 上記粗テレフタル酸のスラリーを加温する熱源の一部
として用いることを特徴とする請求の範囲第 3項記載の高純度テレフタル酸の製 造方法。 4. A part of the heat source that heats the steam to the crude terephthalic acid slurry 4. The method for producing high-purity terephthalic acid according to claim 3, wherein the method is used as a product.
5 . 上記第 1固液分離工程によって得られる 1次分離母液に含有するパラ ト^/レイル酸の少なくとも一部を除去した後に、 上記 1次分離母液を上記水系媒体 の一部として用いることを特徴とする請求の範囲第 1項乃至第 4項のいずれかに 記載の高純度テレフタル酸の製造方法。 5. After removing at least a part of para-^ / leic acid contained in the primary separation mother liquor obtained in the first solid-liquid separation step, use the primary separation mother liquor as a part of the aqueous medium. The method for producing high-purity terephthalic acid according to any one of claims 1 to 4, characterized in that:
6 . 上記第 1固液分離工程によって得られる 1次分離母液を冷却及び 又 は濃縮して得られたスラリーを第 2固液分離工程で 2次結晶と 2次分離母液に分 離し、 6. The slurry obtained by cooling and / or concentrating the primary separated mother liquor obtained in the first solid-liquid separation step is separated into secondary crystals and a secondary separated mother liquor in the second solid-liquid separation step,
上記 2次分離母液を直接又は間接的に上記水系媒体の一部として用いることを 特徴とする請求の範囲第 1項乃至第 4項のいずれかに記載の高純度テレフタル酸 の製造方法。 The method for producing high-purity terephthalic acid according to any one of claims 1 to 4, wherein the secondary separation mother liquor is used directly or indirectly as a part of the aqueous medium.
7 . 上記 2次結晶を、 パラキシレンを酸化する工程に供与することを特徴 とする請求の範囲第 6項記載の高純度テレフタル酸の製造方法。 7. The method for producing high-purity terephthalic acid according to claim 6, wherein the secondary crystal is provided to a step of oxidizing para-xylene.
8 . 粗テレフタル酸は、 4—カルボキベンズアルデヒ ドを 1 0◦ 0〜 5 0 O O p p m含有し、 かつ、 上記還元処理によってこの 4一カルボキベンズアルデ ヒドはパラトルィル酸に還元され、 8. Crude terephthalic acid contains 4-carboxybenzaldehyde in a range of 10 ° to 50 O O pm, and the above-mentioned reduction treatment reduces this 4-carboxybenzaldehyde to paratoluic acid.
上記粗テレフタル酸のスラリ一のスラリ一濃度は 1 0〜5 0重量%であり、 上 記晶析槽から第 1固液分離工程に送られるテレフタル酸スラリーの温度は 1 2 0 〜1 7 0 °Cであり、 上記第 1固液分離工程によって得られる高純度テレフタル酸 ケーキを、 この高純度テレフタル酸ケーキの全重量の 0 . 2〜3 . ◦重量倍の水 系媒体で洗浄又は懸洗し、 その後、 乾燥工程を経て、 パラトルィル酸の濃度が 5 0 ~ 2 0 0 p p mの高重度テレフタル酸結晶を製品として回収することを特徴と する請求の範囲第 1項乃至第 7項のいずれかに記載の高純度テレフタル酸の製造
The slurry concentration of the crude terephthalic acid slurry is 10 to 50% by weight, and the temperature of the terephthalic acid slurry sent from the crystallization tank to the first solid-liquid separation step is 120 to 170%. ° C, and washing or suspending the high-purity terephthalic acid cake obtained in the first solid-liquid separation step with an aqueous medium 0.2 to 3 times the total weight of the high-purity terephthalic acid cake. The method according to any one of claims 1 to 7, wherein a high-grade terephthalic acid crystal having a paratoluic acid concentration of 50 to 200 ppm is recovered as a product through a drying step. Of high-purity terephthalic acid as described in
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CN103121950A (en) * | 2011-11-18 | 2013-05-29 | 株式会社日立工业设备技术 | Method of refining crude terephthalic acid |
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WO1993024441A1 (en) * | 1992-05-29 | 1993-12-09 | Imperial Chemical Industries Plc | Process for the production of purified terephthalic acid |
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WO1993024441A1 (en) * | 1992-05-29 | 1993-12-09 | Imperial Chemical Industries Plc | Process for the production of purified terephthalic acid |
Cited By (2)
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CN103121950A (en) * | 2011-11-18 | 2013-05-29 | 株式会社日立工业设备技术 | Method of refining crude terephthalic acid |
CN103121950B (en) * | 2011-11-18 | 2015-10-14 | 株式会社日立制作所 | The process for purification of crude terephthalic acid |
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