JP2012153611A - Production method of terephthalic acid - Google Patents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
Description
本発明は、酢酸含有溶媒中、コバルト化合物、マンガン化合物及び臭素化合物からなる触媒の存在下、分子状酸素含有ガスを用いてｐ−フェニレン化合物を液相酸化してテレフタル酸を製造する方法において、液相酸化反応系から連続的に排出される酸化反応母液より触媒成分をピリジン環含有キレート樹脂に吸着させて回収し、安定した濃度の触媒液を液相酸化反応系に循環する方法に関する。 The present invention provides a method for producing terephthalic acid by liquid phase oxidation of a p-phenylene compound using a molecular oxygen-containing gas in the presence of a catalyst comprising a cobalt compound, a manganese compound and a bromine compound in an acetic acid-containing solvent. The present invention relates to a method in which a catalyst component is adsorbed and recovered from a pyridine ring-containing chelate resin from an oxidation reaction mother liquor continuously discharged from a liquid phase oxidation reaction system, and a catalyst solution having a stable concentration is circulated to the liquid phase oxidation reaction system.
テレフタル酸は、ｐ−キシレン等のｐ−フェニレン化合物の液相酸化反応により製造され、通常、酢酸溶媒の存在下、コバルト、マンガン等の触媒、又はさらに臭素化合物、アセトアルデヒド等の促進剤を加えた触媒が用いられる。
かかる液相酸化反応により得られるテレフタル酸を含有する酸化反応スラリーは、通常、晶析操作により、低圧、低温のスラリーとされ、常圧に近い圧力の状態での固液分離操作によりテレフタル酸結晶のケーキが分離される。
一方、固液分離して得られた酸化反応母液には、触媒由来のコバルトイオン、マンガンイオン及び臭化物イオンなどの有用な触媒成分が含まれており、これらの触媒成分を回収して循環使用することにより、製造コストを下げることが要求される。
Terephthalic acid is produced by a liquid phase oxidation reaction of a p-phenylene compound such as p-xylene. Usually, in the presence of an acetic acid solvent, a catalyst such as cobalt or manganese, or a promoter such as a bromine compound or acetaldehyde is added. A catalyst is used.
The oxidation reaction slurry containing terephthalic acid obtained by such a liquid phase oxidation reaction is usually made into a low-pressure and low-temperature slurry by crystallization operation, and terephthalic acid crystals are obtained by solid-liquid separation operation at a pressure close to normal pressure. Cakes are separated.
On the other hand, the oxidation reaction mother liquor obtained by solid-liquid separation contains useful catalyst components such as cobalt ions, manganese ions, and bromide ions derived from the catalyst, and these catalyst components are recovered and recycled. Therefore, it is required to reduce the manufacturing cost.
最も簡便な触媒成分の循環方法は、前記酸化反応母液をそのまま反応系に戻して再使用することであり、商業規模のテレフタル酸製造プロセスなどで行われている。
ところが、該酸化反応母液中には、液相酸化反応で副生する様々な有機不純物や装置の腐食に由来する無機不純物などが混在しており、該酸化反応母液をそのまま反応系に再使用すると、反応系におけるこれらの不純物の濃度が次第に高まり、一定量を超えると液相酸化反応に悪影響を与える。
テレフタル酸を製造する場合、該酸化反応母液を反応系に戻す割合は、通常、７０〜９８％であり、反応系に再使用しない２〜３０％の酸化反応母液は、パージ母液として溶媒である酢酸を回収する工程へ送られる。
かかる酢酸回収工程へ送られる酸化反応母液から触媒成分を回収・再使用する方法として、ピリジン環含有キレート樹脂を用いる方法が提案されている（例えば、特許文献１参照）。
The simplest catalyst component circulation method is to return the oxidation reaction mother liquor as it is to the reaction system and reuse it, which is carried out in a commercial scale terephthalic acid production process or the like.
However, in the oxidation reaction mother liquor, various organic impurities by-produced in the liquid phase oxidation reaction and inorganic impurities derived from corrosion of the apparatus are mixed, and when the oxidation reaction mother liquor is reused as it is in the reaction system. The concentration of these impurities in the reaction system gradually increases, and if it exceeds a certain amount, the liquid phase oxidation reaction is adversely affected.
When producing terephthalic acid, the ratio of returning the oxidation reaction mother liquor to the reaction system is usually 70 to 98%, and 2 to 30% of the oxidation reaction mother liquor that is not reused in the reaction system is a solvent as a purge mother liquor. It is sent to the process of recovering acetic acid.
As a method for recovering and reusing the catalyst component from the oxidation reaction mother liquor sent to the acetic acid recovery step, a method using a pyridine ring-containing chelate resin has been proposed (for example, see Patent Document 1).
特許文献１では、触媒由来の重金属イオン及び臭化物イオンをピリジン環含有キレート樹脂に連続的に吸着させ、しかる後に含水酢酸を用いて、吸着した重金属イオン及び臭化物イオンを溶離させて回収触媒液が得られる。該プロセスは、吸着−溶離工程を繰り返し、複数のキレート樹脂塔を切り替えながら触媒成分の回収が行われる。 In Patent Document 1, the catalyst-derived heavy metal ions and bromide ions are continuously adsorbed on the pyridine ring-containing chelate resin, and then the adsorbed heavy metal ions and bromide ions are eluted using hydrous acetic acid to obtain a recovered catalyst solution. It is done. In this process, the adsorption and elution steps are repeated, and the catalyst components are recovered while switching between the plurality of chelate resin towers.
この回収触媒液は、いったんキレート樹脂に吸着した触媒成分が溶離してキレート樹脂より溶出するために、吸着工程−溶離工程のサイクルの中で濃度変動を起こす。これはイオン交換樹脂や合成吸着材に吸着した成分が、溶出時に濃度のピークを持った溶出パターンを示すことと同様の現象である。
従って、程度の差はあるものの、常に濃度変動している回収触媒液を液相酸化反応系、より具体的には触媒調合槽に直接戻すと、例え回収触媒液を連続的に一定流量で送液したとしてもその中に含まれる触媒成分の量は変動しているため、触媒調合槽中の触媒濃度が変動することになる。
Since the catalyst component once adsorbed to the chelate resin elutes and elutes from the chelate resin, the concentration of the recovered catalyst solution varies in the cycle of the adsorption process-elution process. This is the same phenomenon as the component adsorbed on the ion exchange resin or the synthetic adsorbent shows an elution pattern having a concentration peak at the time of elution.
Therefore, if the recovered catalyst solution whose concentration is constantly fluctuating is returned to the liquid-phase oxidation reaction system, more specifically, directly to the catalyst preparation tank, the recovered catalyst solution is continuously sent at a constant flow rate. Even if it is liquid, the amount of the catalyst component contained therein varies, so that the catalyst concentration in the catalyst preparation tank varies.
このような液相酸化反応における触媒濃度の変動は、生成するテレフタル酸結晶の品質に直接影響を及ぼすので、種々の対策が提案されている（例えば、特許文献２、３参照）。
即ち、特許文献２には、排ガス中のＣＯ、ＣＯ2などの濃度を測定して、反応温度、原料供給速度、触媒濃度などを調節することが記載されており、特許文献３には反応器への供給液や循環母液中のマンガン濃度を自動分析計で測定し、その測定値に基づき触媒の供給量を制御し、マンガン濃度の変動係数を１．０％以下に維持することが記載されている。
上記の特許文献２に記載の方法では排ガス中のＣＯ、ＣＯ2などの濃度を測定する煩雑な操作が必要であり、その結果を反応温度、原料供給速度、触媒濃度等にフィードバックするため、タイムラグによる品質の振れはまぬかれ得ない。
また、特許文献３に記載の方法ではマンガン濃度の自動測定装置が必要で操作も煩雑であり、触媒成分の変動を効率的に解消することが困難である。
Since such fluctuations in the catalyst concentration in the liquid phase oxidation reaction directly affect the quality of the terephthalic acid crystals produced, various countermeasures have been proposed (see, for example, Patent Documents 2 and 3).
That is, Patent Document 2 describes that the concentration of CO, CO 2 and the like in exhaust gas is measured to adjust the reaction temperature, raw material supply rate, catalyst concentration, and the like, and Patent Document 3 describes a reactor. It is described that the manganese concentration in the supply liquid and the circulating mother liquor is measured with an automatic analyzer, the supply amount of the catalyst is controlled based on the measured value, and the variation coefficient of the manganese concentration is maintained at 1.0% or less. ing.
The method described in Patent Document 2 requires a complicated operation for measuring the concentration of CO, CO 2 and the like in the exhaust gas, and the result is fed back to the reaction temperature, feed rate, catalyst concentration, etc. The quality fluctuation due to cannot be overwhelmed.
Further, the method described in Patent Document 3 requires an automatic measuring device for manganese concentration, and the operation is complicated, and it is difficult to efficiently eliminate fluctuations in catalyst components.
本発明の目的は、ピリジン環含有キレート樹脂を用いる触媒回収プロセスを有するテレフタル酸の製造方法において、高価な測定制御装置を用いずに、効率良く回収触媒液の濃度変動を抑え、該回収触媒液を戻す触媒調合槽における触媒成分の濃度変動を小さくすることにより、液相酸化反応を安定化させ、品質の安定したテレフタル酸を得る方法を提供することである。 An object of the present invention is to provide a method for producing terephthalic acid having a catalyst recovery process using a pyridine ring-containing chelate resin, efficiently suppressing concentration fluctuations in the recovered catalyst solution without using an expensive measurement controller, and It is intended to provide a method for obtaining terephthalic acid having a stable quality by stabilizing the liquid phase oxidation reaction by reducing the concentration fluctuation of the catalyst component in the catalyst preparation tank for returning the catalyst.
本発明者らは、上記目的を達成するために鋭意検討を重ねた結果、ピリジン環含有キレート樹脂塔から溶出した回収触媒液を受け入れる回収触媒液槽を設け、該回収触媒液槽に一定量の回収触媒液を貯め、滞留した回収触媒液を連続的に触媒調合槽に循環する際に、回収触媒液槽での滞留時間を十分に取ることにより、該キレート樹脂塔から溶出した時点での触媒成分の濃度変動を緩和し、触媒調合槽出口における濃度変動を小さく抑えことができ、液相酸化反応系の触媒濃度が安定し、高品質のテレフタル酸を容易に得ることができることを見出し、本発明に到達した。 As a result of intensive investigations to achieve the above object, the present inventors have provided a recovered catalyst liquid tank that receives the recovered catalyst liquid eluted from the pyridine ring-containing chelate resin tower, and a certain amount of the recovered catalyst liquid tank is provided in the recovered catalyst liquid tank. When the recovered catalyst solution is stored and the retained recovered catalyst solution is continuously circulated to the catalyst preparation tank, the catalyst at the time of elution from the chelate resin tower is obtained by taking sufficient residence time in the recovered catalyst solution tank. It has been found that the concentration fluctuations of the components can be mitigated, the concentration fluctuations at the catalyst preparation tank outlet can be kept small, the catalyst concentration in the liquid phase oxidation reaction system can be stabilized, and high-quality terephthalic acid can be easily obtained. The invention has been reached.
即ち本発明は、以下のテレフタル酸の製造方法を提供する。
１．酢酸含有溶媒中、コバルト化合物、マンガン化合物及び臭素化合物を含む触媒の存在下、分子状酸素含有ガスを用いてｐ−フェニレン化合物を液相酸化してテレフタル酸を製造する方法において、液相酸化により得られた酸化反応スラリーを連続的多段階晶析にて冷却し、該冷却スラリーを固液分離操作にてテレフタル酸結晶と酸化反応母液とに分離し、得られた酸化反応母液の７０〜９８％をリサイクル母液として液相酸化の触媒調合槽に循環し、残りの酸化反応母液をパージ母液として該パージ母液から触媒成分を回収する際に
（I）パージ母液をピリジン環含有キレート樹脂と接触させ、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを吸着する工程（吸着工程）と、
（II）工程（I）により触媒成分を吸着したピリジン環含有キレート樹脂に含水酢酸又は水を接触させて、該触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを溶離して回収触媒液(A)を得る工程（溶離工程）を、
回分式により切り替え、
（III）回収触媒液(A)を回収触媒液槽で１．５〜６時間滞留させる工程
を有し、工程（III）からの回収触媒液(B)を、触媒調合槽を経て液相酸化反応系に循環することを特徴とするテレフタル酸の製造方法。
２．工程（III）からの回収触媒液(B)と、リサイクル母液を予めと混合して触媒調合槽に導入する上記１のテレフタル酸の製造方法。
３．工程（III）からの回収触媒液(B)を触媒調合槽に戻した際の、触媒調合槽出口でのコバルトイオン、マンガンイオン及び臭化物イオンの各濃度の変動係数が全て５％以下である上記１又は２のテレフタル酸の製造方法。
That is, the present invention provides the following method for producing terephthalic acid.
1. In a method for producing terephthalic acid by liquid-phase oxidation of a p-phenylene compound using a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound, a manganese compound and a bromine compound in an acetic acid-containing solvent, The obtained oxidation reaction slurry is cooled by continuous multistage crystallization, the cooling slurry is separated into terephthalic acid crystals and an oxidation reaction mother liquor by solid-liquid separation operation, and the obtained oxidation reaction mother liquor is 70 to 98. When the catalyst component is recovered from the purge mother liquor using the remaining oxidation reaction mother liquor as the purge mother liquor, (I) the purge mother liquor is brought into contact with the pyridine ring-containing chelate resin. A process of adsorbing cobalt ions, manganese ions and bromide ions derived from the catalyst (adsorption process);
(II) A hydrous acetic acid or water is brought into contact with the pyridine ring-containing chelate resin that has adsorbed the catalyst component in step (I) to elute cobalt ions, manganese ions and bromide ions derived from the catalyst, and the recovered catalyst solution (A ) To obtain (elution step)
Switch by batch method,
(III) It has a step of retaining the recovered catalyst solution (A) in the recovered catalyst solution tank for 1.5 to 6 hours, and the recovered catalyst solution (B) from step (III) is liquid-phase oxidized through the catalyst preparation tank. A process for producing terephthalic acid, characterized in that it is circulated in a reaction system.
2. The method for producing terephthalic acid as described in 1 above, wherein the recovered catalyst liquid (B) from step (III) and the recycled mother liquor are mixed in advance and introduced into the catalyst preparation tank.
3. The coefficient of variation of each concentration of cobalt ion, manganese ion and bromide ion at the catalyst preparation tank outlet when the recovered catalyst solution (B) from step (III) is returned to the catalyst preparation tank is 5% or less A process for producing 1 or 2 terephthalic acid.
本発明においては、ピリジン環含有キレート樹脂塔から溶出した回収触媒液を受け入れる回収触媒液槽を設け、該回収触媒液槽に一定量の回収触媒液を貯め、滞留した回収触媒液を連続的に触媒調合槽に戻す際に、回収触媒液槽での滞留時間を十分に取ることにより、該キレート樹脂塔から溶出した時点でのバッチプロセスによる触媒成分の濃度変動を緩和し、触媒調合槽出口における濃度変動を小さく抑え、液相酸化反応に影響を及ぼさないようにすることができ、安定した品質のテレフタル酸を製造することができる。
従って、本発明によれば、高価な分析制御装置を用いずに、簡便な操作で、安定した品質のテレフタル酸を、効率良く製造することができる。
In the present invention, a recovered catalyst liquid tank is provided for receiving the recovered catalyst liquid eluted from the pyridine ring-containing chelate resin tower, a certain amount of recovered catalyst liquid is stored in the recovered catalyst liquid tank, and the retained recovered catalyst liquid is continuously added. When returning to the catalyst preparation tank, sufficient residence time in the recovered catalyst liquid tank is taken to alleviate fluctuations in the concentration of the catalyst component due to the batch process at the time of elution from the chelate resin tower, and at the catalyst preparation tank outlet. Concentration fluctuation can be suppressed to a small extent so as not to affect the liquid phase oxidation reaction, and stable quality terephthalic acid can be produced.
Therefore, according to the present invention, stable quality terephthalic acid can be efficiently produced by a simple operation without using an expensive analysis control device.
本発明では、酢酸含有溶媒中、コバルト化合物、マンガン化合物及び臭素化合物を含む触媒の存在下、分子状酸素含有ガスを用いてｐ−フェニレン化合物を液相酸化してテレフタル酸が製造され、液相酸化により得られた酸化反応スラリーを連続的多段階晶析にて冷却し、該冷却スラリーを固液分離操作にてテレフタル酸結晶と酸化反応母液とに分離し、得られた酸化反応母液の７０〜９８％をリサイクル母液として液相酸化の触媒調合槽に循環し、残りの酸化反応母液をパージ母液として該パージ母液から触媒成分を回収する際に、
（I）パージ母液をピリジン環含有キレート樹脂と接触させ、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを吸着する工程と、
（II）工程（I）により触媒成分を吸着したピリジン環含有キレート樹脂に含水酢酸又は水を接触させて、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを溶離して回収触媒液(A)を得る工程を、
回分式により一定時間毎切り替え、
（III）回収触媒液(A)を回収触媒液槽で１．５〜６時間滞留させる工程
を有し、工程（III）からの回収触媒液(B)を、触媒調合槽を経て液相酸化反応系に循環するものである。
In the present invention, terephthalic acid is produced by liquid-phase oxidation of a p-phenylene compound using a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound, a manganese compound and a bromine compound in an acetic acid-containing solvent. The oxidation reaction slurry obtained by oxidation is cooled by continuous multi-stage crystallization, and the cooling slurry is separated into terephthalic acid crystals and an oxidation reaction mother liquor by solid-liquid separation operation. When recovering catalyst components from the purge mother liquor by circulating ~ 98% as a recycled mother liquor to a liquid phase oxidation catalyst preparation tank and using the remaining oxidation reaction mother liquor as a purge mother liquor,
(I) contacting the purge mother liquor with a pyridine ring-containing chelate resin to adsorb cobalt ions, manganese ions and bromide ions derived from the catalyst;
(II) Recovered catalyst solution (A) by bringing hydrous acetic acid or water into contact with the pyridine ring-containing chelate resin adsorbing the catalyst component in step (I) and eluting cobalt ions, manganese ions and bromide ions derived from the catalyst. The process of obtaining
Switching at regular intervals by batch method,
(III) It has a step of retaining the recovered catalyst solution (A) in the recovered catalyst solution tank for 1.5 to 6 hours, and the recovered catalyst solution (B) from step (III) is liquid-phase oxidized through the catalyst preparation tank. It circulates in the reaction system.
まず、本発明は、酢酸含有溶媒中、コバルト化合物、マンガン化合物及び臭素化合物を含む触媒の存在下、分子状酸素含有ガスを用いてｐ−フェニレン化合物を液相酸化してテレフタル酸を製造する方法に関するものである。
本発明では、酢酸含有溶媒としては、水分１〜１５質量％、好ましくは水分３〜１３質量％の含水酢酸が使用される。ｐ−フェニレン化合物としてはｐ−ジアルキルベンゼンを例示することができ、好ましくはｐ−キシレンである。
First, the present invention provides a method for producing terephthalic acid by liquid phase oxidation of a p-phenylene compound using a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound, a manganese compound and a bromine compound in an acetic acid-containing solvent. It is about.
In the present invention, water-containing acetic acid having a water content of 1 to 15% by mass, preferably 3 to 13% by mass, is used as the acetic acid-containing solvent. An example of the p-phenylene compound is p-dialkylbenzene, preferably p-xylene.
ｐ−フェニレン化合物の液相酸化に用いられる触媒は、コバルト化合物、マンガン化合物及び臭素化合物を含むものである。コバルト化合物及びマンガン化合物の他に、必要に応じてその他の重金属化合物、例えばニッケル化合物、セリウム化合物、ジルコニウム化合物などが添加される。これらのコバルト化合物、マンガン化合物及びその他の重金属化合物としては、各々その有機酸塩、水酸化物、ハロゲン化物、炭酸塩などが例示されるが、特に酢酸塩及び臭化物が好適に用いられる。 The catalyst used for the liquid phase oxidation of the p-phenylene compound contains a cobalt compound, a manganese compound and a bromine compound. In addition to the cobalt compound and the manganese compound, other heavy metal compounds such as a nickel compound, a cerium compound, and a zirconium compound are added as necessary. Examples of these cobalt compounds, manganese compounds and other heavy metal compounds include organic acid salts, hydroxides, halides, carbonates, etc., and acetates and bromides are particularly preferably used.
また臭素化合物としては、反応系で溶解し、臭化物イオンを発生するものであればいかなるものでもよく、臭化水素、臭化ナトリウム、臭化コバルトなどの無機臭素化合物、及びブロモ酢酸、テトラブロムエタンなどの有機臭素化合物が例示され、特に臭化水素（臭化水素酸を含む）、臭化コバルトまたは臭化マンガンが好適に用いられる。 The bromine compound may be any bromine compound that dissolves in the reaction system and generates bromide ions, such as inorganic bromine compounds such as hydrogen bromide, sodium bromide, and cobalt bromide, and bromoacetic acid, tetrabromoethane. Examples of the organic bromine compound include hydrogen bromide (including hydrobromic acid), cobalt bromide, and manganese bromide.
触媒調合槽は、溶媒である低級脂肪族カルボン酸、液相酸化原料であるｐ−フェニレン化合物、触媒である重金属化合物及び臭素化合物を混合する槽であり、触媒調合槽内における内液の均一化を図るために、内液を混合する攪拌機を備えていることが好ましい。ここで均一に調合された混合液（フィードミックスと呼ぶ）は連続的に液相酸化反応器に送液され、酸化剤として用いられる分子状酸素含有ガスと接触することにより液相酸化反応が行われる。
この触媒調合槽に供給される溶媒及び触媒として、リサイクル母液を使用することが好適に行われる。そしてマテリアルバランス上不足する溶媒や触媒は新規供給分として補給される。
The catalyst preparation tank is a tank for mixing a lower aliphatic carboxylic acid as a solvent, a p-phenylene compound as a liquid phase oxidation raw material, a heavy metal compound as a catalyst, and a bromine compound, and uniformizing the internal liquid in the catalyst preparation tank Therefore, it is preferable to provide a stirrer that mixes the internal liquid. Here, the uniformly mixed liquid (referred to as a feed mix) is continuously sent to the liquid phase oxidation reactor, and the liquid phase oxidation reaction is carried out by contact with the molecular oxygen-containing gas used as the oxidizing agent. Is called.
It is preferable to use a recycled mother liquor as the solvent and catalyst supplied to the catalyst preparation tank. Solvents and catalysts that are insufficient in terms of material balance are replenished as new supplies.
液相酸化反応の温度は１６０〜２３０℃、好ましくは１８０〜２１０℃の範囲である。反応温度を１６０℃以上とすることにより、反応中間体が多量に生成スラリー中に残存することがなく、２３０℃以下とすることにより含水酢酸溶媒の燃焼損失が大きくなることがない。液相酸化反応の圧力は、反応温度において反応系が液相を保持できる圧力であれば良く、通常０．８〜３．２ＭＰａＧ、好ましくは１．０〜１．９ＭＰａＧである。
分子状酸素含有ガスとしては、空気、不活性ガス希釈された酸素、酸素富化空気等が用いられるが、設備面及びコスト面から通常は空気の使用が好ましい。
The temperature of the liquid phase oxidation reaction is in the range of 160 to 230 ° C, preferably 180 to 210 ° C. By setting the reaction temperature to 160 ° C. or higher, a large amount of reaction intermediate does not remain in the produced slurry, and by setting it to 230 ° C. or lower, combustion loss of the hydrous acetic acid solvent does not increase. The pressure of the liquid phase oxidation reaction may be any pressure as long as the reaction system can maintain the liquid phase at the reaction temperature, and is usually 0.8 to 3.2 MPaG, preferably 1.0 to 1.9 MPaG.
As the molecular oxygen-containing gas, air, oxygen diluted with an inert gas, oxygen-enriched air, or the like is used, but air is usually preferable in terms of equipment and cost.
酸化反応器で生成した粗テレフタル酸結晶を含む酸化反応スラリーは、先ず、連続的多段階晶析にて冷却されるが、好ましくは直列に連結された次の酸化反応器へ送られて、更に酸素含有ガスによって仕上げの後酸化反応を経た後、連続的多段階晶析、即ち直列に連結された２段以上の晶析槽を経由して落圧、冷却されて、固液分離工程へ送られる。晶析槽の段数は２〜３段とすることが好ましい。 The oxidation reaction slurry containing the crude terephthalic acid crystals produced in the oxidation reactor is first cooled by continuous multistage crystallization, but is preferably sent to the next oxidation reactor connected in series, and further After finishing after oxidation with an oxygen-containing gas, it undergoes continuous multi-stage crystallization, that is, it is dropped and cooled via two or more crystallization tanks connected in series, and sent to the solid-liquid separation process. It is done. The number of stages of the crystallization tank is preferably 2 to 3 stages.
液相酸化反応の例として、例えば、商業規模の装置を使い、含水酢酸中でｐ−キシレンを酢酸コバルト、酢酸マンガン、臭化水素酸の存在下、空気により、液相酸化して粗テレフタル酸スラリーを得、直列に連結された晶析槽へ導いて順次落圧、冷却するプロセスを挙げることができる。 As an example of the liquid phase oxidation reaction, for example, using a commercial scale apparatus, p-xylene is subjected to liquid phase oxidation with air in the presence of cobalt acetate, manganese acetate and hydrobromic acid in hydrous acetic acid, and crude terephthalic acid is obtained. An example is a process in which a slurry is obtained, led to a crystallization tank connected in series, and then gradually dropped and cooled.
液相酸化反応の後、酸化反応スラリーを冷却して粗テレフタル酸結晶を分離する。この固液分離工程では、酸化反応で生成した粗テレフタル酸スラリーが固液分離機によって粗テレフタル酸結晶と酸化反応母液に分離される。この固液分離は通常大気圧下で行われる。固液分離温度に特段の制約はないが、通常は大気圧下における溶媒の沸点より低い温度、例えば５０〜１１０℃の範囲で行われる。固液分離機の形式としては遠心分離機、遠心濾過機、真空濾過機などを挙げることができる。 After the liquid phase oxidation reaction, the oxidation reaction slurry is cooled to separate the crude terephthalic acid crystals. In this solid-liquid separation step, the crude terephthalic acid slurry generated by the oxidation reaction is separated into crude terephthalic acid crystals and an oxidation reaction mother liquor by a solid-liquid separator. This solid-liquid separation is usually performed under atmospheric pressure. The solid-liquid separation temperature is not particularly limited, but it is usually performed at a temperature lower than the boiling point of the solvent under atmospheric pressure, for example, in the range of 50 to 110 ° C. Examples of the solid-liquid separator include a centrifuge, a centrifugal filter, and a vacuum filter.
酸化反応母液には触媒由来のコバルトイオン、マンガンイオン及び臭化物イオンなどの有用な触媒成分が含まれており、その７０〜９８％はリサイクル母液として液相酸化反応系へ循環使用されるが、残りの酸化反応母液（パージ母液）は、液相酸化反応に影響を与える反応副生物や装置由来の腐食金属の濃縮を避けるために系外に排出される。該パージ母液には溶媒である酢酸が含まれているので、通常は酢酸を回収する工程に送られる。
しかし、この該パージ母液中には有用な触媒成分も含まれており、本発明では工程(I)で、ピリジン環含有キレート樹脂と接触させ、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを吸着し、触媒成分の回収を行う。
なお、リサイクル母液の割合は、７０〜９８％、好ましくは８０〜９５％とし、残りのパージ母液の全てをピリジン環含有キレート樹脂塔で処理することが好ましい。
The oxidation reaction mother liquor contains useful catalyst components such as cobalt ions, manganese ions, and bromide ions derived from the catalyst, 70 to 98% of which is recycled to the liquid phase oxidation reaction system as a recycle mother liquor. The oxidation reaction mother liquor (purge mother liquor) is discharged out of the system in order to avoid the concentration of reaction by-products affecting the liquid-phase oxidation reaction and corrosion metals derived from the apparatus. Since the purge mother liquor contains acetic acid as a solvent, it is usually sent to a step of recovering acetic acid.
However, the purge mother liquor also contains useful catalyst components, and in the present invention, in step (I), it is brought into contact with a pyridine ring-containing chelate resin, and cobalt ions, manganese ions and bromide ions derived from the catalyst are brought into contact. Adsorb and recover catalyst components.
The ratio of the recycled mother liquor is 70 to 98%, preferably 80 to 95%, and all of the remaining purge mother liquor is preferably treated with a pyridine ring-containing chelate resin tower.
ここで、本発明で使用するピリジン環含有キレート樹脂とは、４−ビニルピリジンとジビニルベンゼンを主たる原料として重合して得られる、ピリジン環を有する陰イオン交換型のキレート樹脂のことである。また、キレート樹脂は、一般的に、金属イオンに配位して錯体を形成する配位子を持ち、水に不溶性の高分子基体であり、特定の金属イオンを選択的に吸着分離する機能を有するものであり、特にピリジン環を含有することで、重金属イオンを効率良く吸着するという利点を有する。このようなピリジン環含有キレート樹脂は市販されているものを使用してもよく、市販品としては、例えば「ＲＥＩＬＬＥＸ（登録商標）４２５Ｐｏｌｙｍｅｒ」（商品名、Ｖｅｒｔｅｌｌｕｓ社製）、「スミキレート（登録商標）ＣＲ−２」（商品名、住友ケムテックス株式会社製）等が挙げられる。 Here, the pyridine ring-containing chelate resin used in the present invention is an anion exchange type chelate resin having a pyridine ring, which is obtained by polymerization using 4-vinylpyridine and divinylbenzene as main raw materials. Chelate resins generally have a ligand that coordinates to metal ions to form a complex, are insoluble in water, and have a function of selectively adsorbing and separating specific metal ions. In particular, the inclusion of a pyridine ring has the advantage of efficiently adsorbing heavy metal ions. Such a pyridine ring-containing chelate resin may be a commercially available product. Examples of commercially available products include “REILLEX (registered trademark) 425 Polymer” (trade name, manufactured by Vertellus), “Sumichelate (registered trademark)”. CR-2 "(trade name, manufactured by Sumitomo Chemtex Co., Ltd.) and the like.
このキレート樹脂を用いる方法は、主に吸着工程と溶離工程からなる。吸着工程はパージ母液をピリジン環含有キレート樹脂に接触させて触媒由来のコバルトイオン、マンガンイオンなどの重金属イオン及び臭化物イオンを吸着させる工程であり、溶離工程は該キレート樹脂に吸着した触媒成分を含水酢酸又は水を用いて溶離させる工程である。この吸着工程と溶離工程を繰り返すことにより、パージ母液中の触媒成分を回収することができる。
吸着工程と溶離工程における液と樹脂の接触は、液とキレート樹脂を同時に容器中に入れて吸着操作や溶離操作を行うバッチ方式、もしくは該キレート樹脂を塔に充填して液を供給する連続流通方式で行なわれる。ただし、系外にパージされるパージ母液は液相酸化反応工程から連続的に排出されるので、パージ母液と該キレート樹脂との接触は連続流通方式であることが好ましい。
This method using a chelate resin mainly comprises an adsorption step and an elution step. The adsorption step is a step in which the purge mother liquor is brought into contact with a pyridine ring-containing chelate resin to adsorb heavy metal ions such as cobalt ions and manganese ions and bromide ions, and the elution step contains the catalyst components adsorbed on the chelate resin. Elution with acetic acid or water. By repeating this adsorption step and elution step, the catalyst component in the purge mother liquor can be recovered.
The contact between the liquid and the resin in the adsorption process and the elution process is a batch system in which the liquid and the chelate resin are placed in a container at the same time to perform the adsorption operation or the elution operation, or continuous circulation in which the chelate resin is filled in the tower and the liquid is supplied. Done in a manner. However, since the purge mother liquor purged out of the system is continuously discharged from the liquid phase oxidation reaction step, the contact between the purge mother liquor and the chelate resin is preferably a continuous flow system.
連続流通方式は、複数のキレート樹脂塔を用い、吸着工程と溶離工程を切り替えながら触媒成分を回収する方法であり、例えば２塔（仮にＡ塔とＢ塔と呼ぶ）の場合は、Ａ塔が吸着工程の時はＢ塔が溶離工程であり、Ａ塔に触媒成分が十分に吸着されたら（吸着容量を超えて破過する前）塔を切り替えてＡ塔が溶離工程、Ｂ塔が吸着工程となる。
このピリジン環含有キレート樹脂は吸着成分の溶離が比較的簡単であり、吸着と溶離に要する時間の関係は（１）式のようになる。
吸着工程時間≧溶離工程時間 （１）
よってパージ母液の吸着処理はＡ塔、Ｂ塔を切り替えながら連続的に行うことができる。
吸着時のパージ母液の供給速度は、空間速度（ＳＶ）で１．０〜１０．０［１／ｈｒ］が好ましい。吸着工程時間は、ピリジン環含有キレート樹脂が破過する前であれば良く、１．０〜６．０［ｈｒ］が好ましい。また、溶離時の溶離液の供給速度は、空間速度（ＳＶ）で１．０〜１０．０［１／ｈｒ］が好ましく、溶離工程時間は（１）式を満たしつつ、０．５〜６．０[ｈｒ]が好ましい。
The continuous flow system is a method of using a plurality of chelate resin towers and recovering catalyst components while switching between the adsorption process and the elution process. For example, in the case of 2 towers (referred to as A tower and B tower), During the adsorption process, tower B is an elution process, and when the catalyst component is sufficiently adsorbed to tower A (before breakthrough exceeding the adsorption capacity), the tower is switched and tower A is the elution process, and tower B is the adsorption process. It becomes.
In this pyridine ring-containing chelate resin, the elution of the adsorbing component is relatively simple, and the relationship between the adsorption and the time required for the elution is expressed by equation (1).
Adsorption process time ≥ Elution process time (1)
Therefore, the adsorption treatment of the purge mother liquid can be performed continuously while switching between the A tower and the B tower.
The supply rate of the purge mother liquid at the time of adsorption is preferably 1.0 to 10.0 [1 / hr] in space velocity (SV). The adsorption process time may be before the pyridine ring-containing chelate resin breaks through, and is preferably 1.0 to 6.0 [hr]. In addition, the supply rate of the eluent during elution is preferably 1.0 to 10.0 [1 / hr] in space velocity (SV), and the elution step time satisfies 0.5 to 6 while satisfying the formula (1). 0.0 [hr] is preferable.
ピリジン環含有キレート樹脂とパージ母液を接触させてパージ母液中に含まれる触媒成分（コバルトイオン、マンガンイオン、臭化物イオンなど）を該キレート樹脂に吸着させる際に、パージ母液のブロム比（パージ母液中の臭化物イオンの物質量／パージ母液中のコバルトイオンとマンガンイオンの合計物質量）を調整することが好ましい。これはブロム比が高い方が、コバルトイオンとマンガンイオンの吸着率が高く、且つ反応副生物であるカルボン酸類（フタル酸、トリメリット酸、ピロメリット酸など）の吸着率が低下する傾向にあるためである。このブロム比としては、０．７〜３．５が好ましく、０．９〜３．０がさらに好ましい。特に吸着工程でパージ母液のブロム比を高くしておくことで、反応副生物であるカルボン酸類とコバルトイオン、マンガンイオン及び臭化物イオンからなる触媒成分との分離を効率良く行なうことができる。ブロム比の調整方法としては、パージ母液に、例えば臭化水素酸等の、前記臭素化合物の水溶液をブロム源として添加する方法を挙げることができる。 When the catalyst component (cobalt ion, manganese ion, bromide ion, etc.) contained in the purge mother liquor is brought into contact with the pyridine ring-containing chelate resin and the purge mother liquor, the bromine ratio of the purge mother liquor (in the purge mother liquor) It is preferable to adjust the amount of bromide ions of the total amount of cobalt ions and manganese ions in the purge mother liquor). The higher the bromide ratio, the higher the adsorption rate of cobalt ions and manganese ions, and the lower the adsorption rate of carboxylic acids (phthalic acid, trimellitic acid, pyromellitic acid, etc.) that are reaction byproducts. Because. The bromine ratio is preferably 0.7 to 3.5, more preferably 0.9 to 3.0. In particular, by increasing the bromine ratio of the purge mother liquor in the adsorption step, it is possible to efficiently separate the carboxylic acids as reaction by-products from the catalyst components composed of cobalt ions, manganese ions, and bromide ions. Examples of the method for adjusting the bromide ratio include a method in which an aqueous solution of the bromine compound such as hydrobromic acid is added as a bromide source to the purge mother liquor.
キレート樹脂を用いる触媒回収方法の溶離工程では、溶離液を供給しているキレート樹脂塔からの流出液を回収することになるが、流出液中に常に樹脂から溶出する触媒成分があるわけではなく、触媒成分が含まれる部分のみを回収触媒液として回収触媒液槽に送るようにする必要がある。これは水分濃度の高い溶離液由来の水分をできるだけ回収せず、水分を酸化反応系に持ち込まないためである。また、樹脂からの触媒成分の溶出はピークを持ったパターンを持ち、溶出中の触媒成分濃度は刻々と変動しており、有効な触媒成分を回収することが重要である。 In the elution step of the catalyst recovery method using a chelate resin, the effluent from the chelate resin tower supplying the eluent is recovered, but the effluent does not always have a catalyst component that elutes from the resin. It is necessary to send only the portion containing the catalyst component to the recovered catalyst solution tank as the recovered catalyst solution. This is because water derived from the eluent having a high water concentration is not collected as much as possible, and water is not brought into the oxidation reaction system. Moreover, the elution of the catalyst component from the resin has a pattern with a peak, and the concentration of the catalyst component during the elution is constantly changing, and it is important to recover an effective catalyst component.
本発明において、工程(I)が吸着工程に相当し、酸化反応母液の残りをピリジン環含有キレート樹脂と接触させ、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを吸着する。また、工程（II）が前記の溶離工程に相当し、溶離液として含水酢酸又は水を使用する。
また、このようなキレート樹脂塔を用いる触媒回収方法では、吸着工程の後、副生カルボン酸を回収する回収工程を設けることが好ましい。
即ち、前記吸着工程を経た後のピリジン環含有キレート樹脂に水分濃度１〜１５質量％、好ましくは水分濃度１〜１４質量％、より好ましくは水分濃度１〜９質量％の含水酢酸を接触させて副生カルボン酸混合物を選択的に溶離する回収工程を経た後、含水酢酸又は水を接触させて触媒由来の重金属イオン及び臭化物イオンを回収する溶離工程を経るようにすることが好ましい。工程（II）の溶離工程の前に回収工程を有することにより、ピリジン環含有キレート樹脂に他の有機不純物や金属不純物が殆ど吸着していないため、溶離液として水分濃度２０質量％以上の含水酢酸、好ましくは水分濃度２０〜７０質量％、より好ましくは水分濃度２５〜５０質量％の含水酢酸をピリジン環含有キレート樹脂に接触させることによって、そのまま液相酸化反応に再使用可能なコバルトイオン、マンガンイオン及び臭化物イオンなどを含有する含水酢酸、即ち「回収触媒液」が得られる。
In the present invention, step (I) corresponds to an adsorption step, and the remainder of the oxidation reaction mother liquor is brought into contact with a pyridine ring-containing chelate resin to adsorb cobalt ions, manganese ions and bromide ions derived from the catalyst. Step (II) corresponds to the elution step described above, and hydrous acetic acid or water is used as the eluent.
Moreover, in the catalyst recovery method using such a chelate resin tower, it is preferable to provide a recovery step of recovering byproduct carboxylic acid after the adsorption step.
That is, hydrated acetic acid having a water concentration of 1 to 15% by weight, preferably 1 to 14% by weight, more preferably 1 to 9% by weight, is brought into contact with the pyridine ring-containing chelate resin after the adsorption step. It is preferable that after a recovery step of selectively eluting the by-product carboxylic acid mixture, an elution step of recovering heavy metal ions and bromide ions derived from the catalyst by contacting with hydrous acetic acid or water is preferable. By having a recovery step before the elution step of step (II), other organic impurities and metal impurities are hardly adsorbed on the pyridine ring-containing chelate resin, so hydrous acetic acid having a water concentration of 20% by mass or more as an eluent. Cobalt ions and manganese that can be reused in a liquid phase oxidation reaction by contacting hydrous acetic acid having a water concentration of 20 to 70% by mass, more preferably 25 to 50% by mass with a pyridine ring-containing chelate resin. Hydrous acetic acid containing ions and bromide ions, that is, a “recovered catalyst solution” is obtained.
また、上記溶離工程を経たピリジン環含有キレート樹脂に、触媒成分の吸着効率の観点から、置換工程を設け、水分濃度１〜１５質量％、好ましくは水分濃度１〜１４質量％、より好ましくは水分濃度１〜９質量％の含水酢酸を置換液として接触させ、ピリジン環含有キレート樹脂を再生することが好ましい。こうして再生されるピリジン環含有キレート樹脂は吸着工程に再使用できる。
このような置換工程により、キレート樹脂の周りに存在する含水酢酸の水分濃度を置換液の水分濃度まで下げて、次の吸着工程にて重金属イオン及び臭化物イオンが速やかに吸着される状態になる。一方、該置換工程を設けない場合、溶離工程の直後は該キレート樹脂層の周りが高い水分濃度の含水酢酸で覆われているため、吸着工程における母液との接触初期において、触媒成分の吸着効率が悪くなり、触媒成分の回収率が低下し、経済的に不利となる。
さらにピリジン環含有キレート樹脂にコバルトイオン、マンガンイオン、臭化物イオンを吸着し易くするため、置換液としては水分濃度が１〜１５質量％であり且つ臭化物イオンを１〜１０００質量ｐｐｍ含む含水酢酸を用いることがより好ましい。
なお、吸着工程で得られる母液残液、回収工程で得られる回収液及び上記の置換工程で使用した置換液から水を留去する際に蒸留塔のボトムから得られる回収酢酸（水分濃度４〜１２質量％、臭化物イオン濃度１〜５０質量ｐｐｍ）を、置換液として用いることもできる。
Moreover, from the viewpoint of the adsorption efficiency of the catalyst component, the pyridine ring-containing chelate resin that has undergone the elution step is provided with a substitution step, and has a moisture concentration of 1 to 15% by mass, preferably a moisture concentration of 1 to 14% by mass, more preferably moisture. It is preferable to regenerate the pyridine ring-containing chelate resin by contacting hydrous acetic acid having a concentration of 1 to 9% by mass as a replacement liquid. The regenerated pyridine ring-containing chelate resin can be reused in the adsorption process.
By such a substitution step, the water concentration of the hydrous acetic acid present around the chelate resin is lowered to the moisture concentration of the substitution solution, and the heavy metal ions and bromide ions are quickly adsorbed in the next adsorption step. On the other hand, when the replacement step is not provided, immediately after the elution step, the periphery of the chelate resin layer is covered with hydrous acetic acid having a high water concentration, so that the adsorption efficiency of the catalyst component at the initial contact with the mother liquor in the adsorption step Becomes worse, the recovery rate of the catalyst component is lowered, which is economically disadvantageous.
Further, in order to facilitate adsorption of cobalt ions, manganese ions, and bromide ions to the pyridine ring-containing chelate resin, hydrous acetic acid having a water concentration of 1 to 15% by mass and containing bromide ions of 1 to 1000 ppm by mass is used as the substitution liquid. It is more preferable.
In addition, the recovered acetic acid (moisture concentration of 4 to 4) obtained from the bottom of the distillation tower when water is distilled off from the mother liquor residual liquid obtained in the adsorption process, the recovered liquid obtained in the recovery process, and the replacement liquid used in the above replacement process. 12 mass%, bromide ion concentration 1-50 mass ppm) can also be used as a replacement liquid.
本発明は工程（III）で、触媒成分の濃度変動を小さくするため、該樹脂塔から流出する回収触媒液(A)を回収触媒液槽に一旦貯め、一定の滞留時間を保った後に触媒調合槽を経て液相酸化反応系に戻すものである。
回収触媒液槽の有効容積をＶ［ｍ3］、回収触媒液(A)の流量をＱ［ｍ3／ｈｒ］とすると、回収触媒液槽における滞留時間Ｔ［ｈｒ］は（２）式のように定義される。
滞留時間：Ｔ＝Ｖ／Ｑ （２）
本発明での回収触媒液槽における回収触媒液の滞留時間は１．５〜６時間であり、好ましくは１．５〜４時間である。滞留時間を１．５時間以上とすることにより触媒成分の濃度変動を緩和し、触媒調合槽出口における濃度変動を小さく抑えことができる。
In the step (III) of the present invention, in order to reduce the concentration fluctuation of the catalyst component, the recovered catalyst liquid (A) flowing out from the resin tower is temporarily stored in the recovered catalyst liquid tank, and after maintaining a certain residence time, the catalyst preparation is performed. It returns to the liquid phase oxidation reaction system through the tank.
Assuming that the effective volume of the recovered catalyst solution tank is V [m 3 ] and the flow rate of the recovered catalyst solution (A) is Q [m 3 / hr], the residence time T [hr] in the recovered catalyst solution tank is expressed by the equation (2). Is defined as
Residence time: T = V / Q (2)
The residence time of the recovered catalyst solution in the recovered catalyst solution tank in the present invention is 1.5 to 6 hours, preferably 1.5 to 4 hours. By setting the residence time to 1.5 hours or more, the concentration fluctuation of the catalyst component can be reduced, and the concentration fluctuation at the catalyst preparation tank outlet can be suppressed to a small level.
溶離工程における該キレート樹脂塔からの流出液は、触媒成分が溶出している時は回収触媒液槽に送液されるが、前記の回収工程や置換工程などで触媒成分が溶出していない時の流出液は別に設置したパージ液槽に送液され、必要に応じて溶媒や副生カルボン酸の回収が行われる。また、触媒成分が溶出している時もその濃度は変動しているので本発明により回収触媒液槽を設置して一定の滞留時間とすることにより濃度変動を緩和する。
回収触媒液槽から液相酸化の触媒調合槽に送液される回収触媒液(B)は、液相酸化における触媒成分を安定化させるために特定量で連続的に液相酸化系に供給することが必要である。滞留時間を長くするには回収触媒液槽の有効容積を大きくする必要があり、これは設備投資額の増大につながるために限界がある。回収触媒液(B)の濃度変動を小さくするためには、ある程度の滞留時間を取ることが必要であり、これらのことを勘案すると、回収触媒液槽の滞留時間は１．５〜６時間の範囲が好ましい。
The effluent from the chelate resin tower in the elution step is sent to the recovered catalyst solution tank when the catalyst component is eluted, but when the catalyst component is not eluted in the recovery step or the replacement step. The effluent is sent to a separately installed purge solution tank, and the solvent and by-product carboxylic acid are recovered as necessary. Further, since the concentration of the catalyst component is also eluted, the concentration variation is mitigated by installing a recovered catalyst solution tank and setting a certain residence time according to the present invention.
The recovered catalyst liquid (B) fed from the recovered catalyst tank to the catalyst preparation tank for liquid phase oxidation is continuously supplied to the liquid phase oxidation system in a specific amount in order to stabilize the catalyst components in the liquid phase oxidation. It is necessary. In order to lengthen the residence time, it is necessary to increase the effective volume of the recovered catalyst liquid tank, which is limited because it leads to an increase in the amount of capital investment. In order to reduce the concentration fluctuation of the recovered catalyst liquid (B), it is necessary to take a certain residence time. Taking these into consideration, the residence time of the recovered catalyst liquid tank is 1.5 to 6 hours. A range is preferred.
溶離工程において該キレート樹脂塔より流出する回収触媒液(A)は、回収触媒液槽に送液され、所定の滞留時間を経てから濃度変動を抑えた回収触媒液(B)として液相酸化の触媒調合槽にリサイクルされる。滞留時間の調節は回収触媒液槽の液面の上げ下げにて行う。回収触媒液槽内における触媒組成の均一化を図るために、内液を混合する攪拌機を備えていることが好ましい。
回収触媒液(B)は通常は触媒調合槽に直接リサイクルされるが、リサイクル母液と予め混合して触媒調合槽にリサイクルすることも可能である。リサイクル母液と予め混合するとは、リサイクル母液が循環している配管に回収触媒液(B)を添加することであり、そのまま添加しても良いし、スタティックミキサー等の混合器を用いることも行われる。回収触媒液(B)をリサイクル母液と混合することにより触媒成分の濃度変動の振れ幅が小さくなり、触媒調合槽に戻した時の戻し口近傍での濃度変動を抑えることができる。
The recovered catalyst solution (A) flowing out from the chelate resin tower in the elution step is sent to the recovered catalyst solution tank, and after a predetermined residence time, the recovered catalyst solution (B) with reduced concentration fluctuations is subjected to liquid phase oxidation. Recycled to catalyst preparation tank. The residence time is adjusted by raising and lowering the liquid level of the recovered catalyst tank. In order to make the catalyst composition uniform in the recovered catalyst liquid tank, it is preferable to have a stirrer that mixes the internal liquid.
The recovered catalyst solution (B) is usually recycled directly to the catalyst preparation tank, but it can also be mixed with the recycle mother liquor in advance and recycled to the catalyst preparation tank. Premixing with the recycled mother liquor means adding the recovered catalyst solution (B) to the pipe through which the recycled mother liquor is circulated, which may be added as it is or using a mixer such as a static mixer. . By mixing the recovered catalyst solution (B) with the recycle mother liquor, the fluctuation range of the concentration fluctuation of the catalyst component is reduced, and the concentration fluctuation in the vicinity of the return port when returned to the catalyst preparation tank can be suppressed.
回収触媒液の濃度変動に起因する液相酸化反応の状態変動を抑えるためには、濃度変動幅を管理することが必要となる。管理点としては回収触媒液槽や触媒調合槽が好適である。液相酸化反応に直接影響が出やすいという点では触媒調合槽が重要である。ここで実際に管理する触媒成分は重金属イオン及び／または臭化物イオンであり、具体的にはコバルトイオン濃度、マンガンイオン濃度、臭化物イオン濃度を対象として、それらの濃度変動の変動係数で管理することになる。
ここで、変動係数は（３）式のように定義される。
変動係数＝（標準偏差／平均値）×１００［％］ （３）
コバルトイオン濃度、マンガンイオン濃度、臭化物イオン濃度の測定は、回収触媒液槽又は触媒調合槽において通常３回／日以上行い、測定数が１５点以上で変動係数を管理することが好ましい。
触媒調合槽出口におけるコバルトイオン、マンガンイオン、臭化物イオンの各濃度の変動係数は全て５．０％以下であることが好ましく、より好ましくは３．０％以下である。
In order to suppress the state fluctuation of the liquid phase oxidation reaction caused by the concentration fluctuation of the recovered catalyst liquid, it is necessary to manage the concentration fluctuation width. As a management point, a recovered catalyst solution tank or a catalyst preparation tank is suitable. A catalyst preparation tank is important in that it directly affects the liquid phase oxidation reaction. The catalyst components actually managed here are heavy metal ions and / or bromide ions. Specifically, for the cobalt ion concentration, manganese ion concentration, and bromide ion concentration, the catalyst components are managed by the variation coefficient of their concentration fluctuations. Become.
Here, the coefficient of variation is defined as in equation (3).
Coefficient of variation = (standard deviation / average value) x 100 [%] (3)
The cobalt ion concentration, manganese ion concentration, and bromide ion concentration are preferably measured 3 times / day or more in the recovered catalyst solution tank or catalyst preparation tank, and the coefficient of variation is preferably managed with 15 or more measurements.
The coefficient of variation of each concentration of cobalt ion, manganese ion, and bromide ion at the catalyst preparation tank outlet is preferably 5.0% or less, and more preferably 3.0% or less.
以下、実施例等により本発明を更に詳細に説明するが、本発明はこれらの例により何ら限定されるものではない。
なお、以下の実施例において、ピリジン環含有キレート樹脂の前処理、重金属イオン（コバルトイオン、マンガンイオン）の測定、および臭化物イオンの濃度の測定を次にように行った。
EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further in detail, this invention is not limited at all by these examples.
In the following Examples, pretreatment of the pyridine ring-containing chelate resin, measurement of heavy metal ions (cobalt ions and manganese ions), and measurement of bromide ion concentration were performed as follows.
＜ピリジン環含有キレート樹脂の前処理＞
ピリジン環含有キレート樹脂〔「ＲＥＩＬＬＥＸ（登録商標）４２５Ｐｏｌｙｍｅｒ」：商品名、Ｖｅｒｔｅｌｌｕｓ社製〕にＨＢｒ含有量が１．２質量％である臭化水素酸水溶液を通液させて該キレート樹脂を水溶媒（Ｂｒ-形）とし、次いで含水率が７．０質量％である酢酸溶媒を通液させて該キレート樹脂を酢酸溶媒（Ｂｒ-形）とした。
<Pretreatment of pyridine ring-containing chelate resin>
An aqueous solution of hydrobromic acid having a HBr content of 1.2% by mass is passed through a pyridine ring-containing chelate resin ["REILLEX (registered trademark) 425 Polymer": trade name, manufactured by Vertellus] to pass the chelate resin in an aqueous solvent. (Br - form), and then the water content is passed through the acetic acid solvent is 7.0% by weight the chelate resin acetic acid solvent - was (Br shape).
＜重金属イオンの濃度の測定＞
以下の仕様の原子吸光分析装置を用いて、重金属イオンの濃度を測定した。
機種：偏光ゼーマン原子吸光光度計Ｚ−２３００（株式会社日立ハイテクノロジーズ製）
波長：コバルトイオン２４０．７ｎｍ、マンガンイオン２７９．６ｎｍ
フレーム：アセチレン−空気
測定方法：１００ｍｌガラス製容器にサンプルを電子天秤にて重量を計り適量入れ、精密分析用２０質量％塩酸（定沸点、無鉄塩酸）約２ｍｌ及び純水を加えて測定対象の重金属イオンが約１ｐｐｍの濃度になるように電子天秤にて希釈サンプル重量を計って希釈する。０ｐｐｍ、１ｐｐｍ、２ｐｐｍの標準サンプルにより検量線を作成し、希釈サンプルの濃度を測定する。希釈サンプルの濃度に希釈倍率を掛けて重金属イオンの濃度を求める。
<Measurement of heavy metal ion concentration>
The concentration of heavy metal ions was measured using an atomic absorption analyzer with the following specifications.
Model: Polarized Zeeman atomic absorption photometer Z-2300 (manufactured by Hitachi High-Technologies Corporation)
Wavelength: Cobalt ion 240.7nm, Manganese ion 279.6nm
Frame: Acetylene-air Measuring method: Weigh the sample in a 100 ml glass container with an electronic balance, put an appropriate amount, add about 2 ml of 20 mass% hydrochloric acid (constant boiling point, iron-free hydrochloric acid) for precision analysis and pure water to measure The diluted sample is weighed and diluted with an electronic balance so that the concentration of heavy metal ions is about 1 ppm. A calibration curve is prepared using standard samples of 0 ppm, 1 ppm, and 2 ppm, and the concentration of the diluted sample is measured. Multiply the concentration of the diluted sample by the dilution factor to determine the concentration of heavy metal ions.
＜臭化物イオンの濃度の測定＞
臭化物イオンの濃度は、以下の条件で測定した。
滴定装置：電位差自動滴定装置 ＡＴ−５１０（京都電子工業株式会社製）
滴定液：１／２５０規定硝酸銀水溶液
検出電極：複合ガラス電極：Ｃ−１７２、
銀電極：Ｍ−２１４
温度補償電極：Ｔ−１１１
測定方法：２００ｍｌビーカーにテフロン（登録商標）製攪拌子を入れ、サンプルを適量入れる（天秤にてサンプル重量を計る）。純水を加えてビーカー内の液量を約１５０ｍｌとし、更に６０質量％の硝酸を約２ｍｌ加える。上記自動滴定装置にて沈殿滴定を行い、臭化物イオン濃度を求める。
<Measurement of bromide ion concentration>
The concentration of bromide ions was measured under the following conditions.
Titrator: automatic potentiometric titrator AT-510 (manufactured by Kyoto Electronics Industry Co., Ltd.)
Titration solution: 1/250 normal silver nitrate aqueous solution Detection electrode: Composite glass electrode: C-172
Silver electrode: M-214
Temperature compensation electrode: T-111
Measuring method: Put a Teflon (registered trademark) stirrer in a 200 ml beaker and put an appropriate amount of sample (weigh the sample with a balance). Pure water is added to make the liquid in the beaker about 150 ml, and about 2 ml of 60% by mass nitric acid is added. Precipitation titration is performed with the above automatic titrator to determine bromide ion concentration.
＜実施例１＞
水分濃度９質量％の含水酢酸中で、ｐ−キシレンをコバルトイオン５００ｐｐｍ、マンガンイオン３００ｐｐｍ及び臭化物イオン７００ｐｐｍの存在下、空気により連続２段で液相酸化（反応温度２００℃、反応圧力１．５ＭＰａＧ）させることにより、粗テレフタル酸スラリー（テレフタル酸濃度３４質量％、分散媒である含水酢酸の水分濃度１１質量％）を得、直列に連結された２段の晶析槽へ導いて順次落圧して大気圧下の粗テレフタル酸スラリーとした。このスラリーを固液分離し、粗テレフタル酸ケーキと酸化反応母液を得た。また、触媒回収プロセスおよび回収触媒液(B)を用いる次回の液相酸化を行うのに十分な量の酸化反応母液を準備した。該酸化反応母液の触媒組成を表−１に示す。
<Example 1>
Liquid phase oxidation (reaction temperature 200 ° C., reaction pressure 1.5 MPaG) in air continuously in two stages in the presence of cobalt ions 500 ppm, manganese ions 300 ppm and bromide ions 700 ppm in hydrous acetic acid with a water concentration of 9% by mass. ) To obtain a crude terephthalic acid slurry (terephthalic acid concentration: 34% by mass, water concentration of water-containing acetic acid: 11% by mass), which is introduced into a two-stage crystallization tank connected in series, and gradually reduced in pressure. Thus, a crude terephthalic acid slurry at atmospheric pressure was obtained. This slurry was subjected to solid-liquid separation to obtain a crude terephthalic acid cake and an oxidation reaction mother liquor. In addition, a sufficient amount of an oxidation reaction mother liquor was prepared for the next liquid phase oxidation using the catalyst recovery process and the recovered catalyst liquid (B). The catalyst composition of the oxidation reaction mother liquor is shown in Table-1.
該酸化反応母液の９０％を反応系へリサイクルし、リサイクルしない１０％分のパージ母液を、セラミックフィルターを用いるクロスフロー濾過して、テレフタル酸を主成分とする微細結晶を除去して濾過液を得た。触媒回収工程における触媒成分の回収率を向上させるため、該濾過液に臭化水素酸水溶液を添加した。この臭素添加パージ母液の触媒成分の組成を表−２に示す。 90% of the oxidation reaction mother liquor is recycled to the reaction system, and 10% of the purge mother liquor that is not recycled is subjected to cross-flow filtration using a ceramic filter to remove fine crystals mainly composed of terephthalic acid, and the filtrate is obtained. Obtained. In order to improve the recovery rate of the catalyst component in the catalyst recovery step, an aqueous hydrobromic acid solution was added to the filtrate. Table 2 shows the composition of the catalyst component of this bromine-added purge mother liquor.
前記の前処理を行ったピリジン環含有キレート樹脂５０[Ｌ]をガラス製二重管に充填したピリジン環含有キレート樹脂塔のジャケットに、８０℃の熱水を循環させて、ピリジン環含有キレート樹脂を８０℃に保温した。
上記の臭素添加パージ母液をピリジン環含有キレート樹脂塔の上部から下方へ流速１２５[Ｌ／ｈｒ]で１２０分間通液した［吸着工程］。
その後、水分濃度７．０質量％の含水酢酸を塔の上部から下方へ流速１００[Ｌ／ｈｒ]で１０分間通液した［回収工程］。
回収工程の後、水分濃度３５．０質量％の含水酢酸を、塔の上部から下方へ流速９０[Ｌ／ｈｒ]で１００分間通液した［溶離工程］。
溶離工程が終了したら置換液（水分濃度７．０質量％の含水酢酸）を塔の上部から下方へ流速１００[Ｌ／ｈｒ]で１０分間通液した［置換工程］。
この吸着工程→回収工程→溶離工程→置換工程→（吸着工程）のサイクルを２４０分／１サイクルで繰り返した。
また、該キレート樹脂塔からの流出液は、溶離工程にて溶出する触媒成分を回収触媒液槽に回収する時間を１１０分、触媒成分の溶出がほとんどないために該キレート樹脂塔からの流出液をパージ液槽に送る時間を１３０分とした。
By circulating 80 ° C. hot water through the jacket of the pyridine ring-containing chelate resin tower in which the pretreated pyridine ring-containing chelate resin 50 [L] is packed in a glass double tube, the pyridine ring-containing chelate resin is obtained. Was kept at 80 ° C.
The bromine-added purge mother liquor was passed from the top of the pyridine ring-containing chelate resin tower downward for 120 minutes at a flow rate of 125 [L / hr] [adsorption step].
Thereafter, hydrous acetic acid having a water concentration of 7.0% by mass was passed from the top of the tower downward for 10 minutes at a flow rate of 100 [L / hr] [recovery step].
After the recovery step, hydrous acetic acid having a water concentration of 35.0% by mass was passed from the top of the tower downward for 100 minutes at a flow rate of 90 [L / hr] [elution step].
When the elution step was completed, a substitution solution (hydrous acetic acid having a water concentration of 7.0% by mass) was passed from the top of the column downward for 10 minutes at a flow rate of 100 [L / hr] [substitution step].
This cycle of adsorption process → recovery process → elution process → replacement process → (adsorption process) was repeated at 240 minutes / cycle.
In addition, the effluent from the chelate resin tower has an effluent from the chelate resin tower because the catalyst component eluting in the elution step is collected for 110 minutes in the recovery catalyst liquid tank, and there is almost no elution of the catalyst component. Was sent to the purge solution tank for 130 minutes.
溶離工程で得られた回収触媒液(A)を攪拌機付きの回収触媒液槽に送液した。送液される回収触媒液(A)の平均流量は９０[Ｌ／ｈｒ]であり、回収触媒液槽の平均液面を５０％（この時の平均有効容積１８０［Ｌ］）とした。滞留時間は２［ｈｒ］となる。回収触媒液(A)の触媒成分の濃度変動幅を表−３に示す。触媒成分などの測定は２４回／２時間行い、４８点の濃度変動幅を示したものである。 The recovered catalyst solution (A) obtained in the elution step was sent to a recovered catalyst solution tank equipped with a stirrer. The average flow rate of the recovered catalyst solution (A) fed was 90 [L / hr], and the average liquid level of the recovered catalyst solution tank was 50% (average effective volume at this time 180 [L]). The residence time is 2 [hr]. Table 3 shows the concentration fluctuation range of the catalyst component of the recovered catalyst solution (A). The measurement of the catalyst component and the like was performed 24 times / 2 hours, and the concentration fluctuation range of 48 points was shown.
回収触媒液槽に２時間滞留させた後の回収触媒液(B)を予めリサイクル母液と共に混合して触媒調合槽へ送液し、液相酸化を行い、テレフタル酸を製造した。回収触媒液(B)の流量は回収触媒液(A)の平均流量と同じ９０[Ｌ／ｈｒ]とした。この回収触媒液(B)の触媒組成の平均値を表−４に示す。触媒成分などの測定は２４回／２時間行い、４８点の濃度変動幅を示したものである。 The recovered catalyst solution (B) that had been retained in the recovered catalyst solution tank for 2 hours was mixed with the recycle mother liquor in advance and sent to the catalyst preparation tank, and liquid phase oxidation was performed to produce terephthalic acid. The flow rate of the recovered catalyst solution (B) was 90 [L / hr], which is the same as the average flow rate of the recovered catalyst solution (A). The average value of the catalyst composition of this recovered catalyst solution (B) is shown in Table-4. The measurement of the catalyst component and the like was performed 24 times / 2 hours, and the concentration fluctuation range of 48 points was shown.
触媒調合槽出口の触媒組成および得られた粗テレフタル酸結晶の品質における標準偏差と変動係数を表−５に示す。なお、ここでいう品質とは、テレフタル酸をアルカリに溶解した溶液の波長３４０ｎｍにおける吸光度（色相値、ＯＤ340と称す）と酸化反応中間体である４−カルボキシベンズアルデヒド（４−ＣＢＡと略す）含有量である。 Table 5 shows the standard deviation and the coefficient of variation in the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude terephthalic acid crystals. The quality referred to here includes the absorbance (hue value, referred to as OD 340 ) at a wavelength of 340 nm of a solution in which terephthalic acid is dissolved in an alkali, and 4-carboxybenzaldehyde (abbreviated as 4-CBA) as an oxidation reaction intermediate. Amount.
＜実施例２＞
回収触媒液槽の平均有効容積を３６０［Ｌ］とし、滞留時間を４［ｈｒ］とした以外は実施例１と同様に運転を行った。回収触媒液(B)の触媒組成変動幅を表−６に、触媒調合槽出口の触媒組成および得られた粗テレフタル酸結晶の品質における標準偏差と変動係数を表−７に示す。液相酸化反応、特に後酸化反応の酸素消費量に大きな変動は見られなかった。粗テレフタル酸結晶の品質にも変動は見られなかった。
<Example 2>
The operation was performed in the same manner as in Example 1 except that the average effective volume of the recovered catalyst solution tank was 360 [L] and the residence time was 4 [hr]. Table 6 shows the catalyst composition fluctuation range of the recovered catalyst solution (B), and Table 7 shows the standard deviation and coefficient of variation in the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude terephthalic acid crystals. There was no significant change in the oxygen consumption of the liquid phase oxidation reaction, especially the post-oxidation reaction. There was no change in the quality of the crude terephthalic acid crystals.
＜比較例１＞
回収触媒液槽の平均有効容積を９０［Ｌ］とし、滞留時間を１［ｈｒ］とした以外は実施例１と同様に運転を行った。回収触媒液(B)の触媒組成変動幅を表−８に、触媒調合槽出口の触媒組成および得られた粗テレフタル酸結晶の品質における標準偏差と変動係数を表−９に示す。液相酸化反応、特に後酸化反応の酸素消費量に変動が見られた。また、粗テレフタル酸結晶の品質が大きく変動した。
<Comparative Example 1>
The operation was performed in the same manner as in Example 1 except that the average effective volume of the recovered catalyst solution tank was 90 [L] and the residence time was 1 [hr]. The catalyst composition fluctuation range of the recovered catalyst solution (B) is shown in Table-8, and the standard deviation and the coefficient of variation in the catalyst composition at the catalyst preparation tank outlet and the quality of the obtained crude terephthalic acid crystals are shown in Table-9. Variations were observed in the oxygen consumption of the liquid phase oxidation reaction, especially the post-oxidation reaction. In addition, the quality of the crude terephthalic acid crystals varied greatly.
以上のように、限定された条件で触媒成分を回収・リサイクルすることにより、粗テレフタル酸結晶の品質である４−ＣＢＡ含有量とＯＤ340の変動係数を抑えることができる。 As described above, the coefficient of variation of 4-CBA content and OD 340 , which are the quality of the crude terephthalic acid crystal, can be suppressed by collecting and recycling the catalyst component under limited conditions.
本発明によれば、安定した品質のテレフタル酸を、容易に、効率良く、工業的に有利に製造できる。 According to the present invention, stable quality terephthalic acid can be easily and efficiently produced industrially advantageously.
Claims (3)
（I）パージ母液をピリジン環含有キレート樹脂と接触させ、触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを吸着する工程（吸着工程）と、
（II）工程（I）により触媒成分を吸着したピリジン環含有キレート樹脂に含水酢酸又は水を接触させて、該触媒に由来するコバルトイオン、マンガンイオン及び臭化物イオンを溶離して回収触媒液(A)を得る工程（溶離工程）を、
回分式により切り替え、
（III）回収触媒液(A)を回収触媒液槽で１．５〜６時間滞留させる工程
を有し、工程（III）からの回収触媒液(B)を、触媒調合槽を経て液相酸化反応系に循環することを特徴とするテレフタル酸の製造方法。 In a method for producing terephthalic acid by liquid-phase oxidation of a p-phenylene compound using a molecular oxygen-containing gas in the presence of a catalyst containing a cobalt compound, a manganese compound and a bromine compound in an acetic acid-containing solvent, The obtained oxidation reaction slurry is cooled by continuous multistage crystallization, the cooling slurry is separated into terephthalic acid crystals and an oxidation reaction mother liquor by solid-liquid separation operation, and the obtained oxidation reaction mother liquor is 70 to 98. When the catalyst component is recovered from the purge mother liquor using the remaining oxidation reaction mother liquor as the purge mother liquor, (I) the purge mother liquor is brought into contact with the pyridine ring-containing chelate resin. A process of adsorbing cobalt ions, manganese ions and bromide ions derived from the catalyst (adsorption process);
(II) A hydrous acetic acid or water is brought into contact with the pyridine ring-containing chelate resin that has adsorbed the catalyst component in step (I) to elute cobalt ions, manganese ions and bromide ions derived from the catalyst, and the recovered catalyst solution (A ) To obtain (elution step)
Switch by batch method,
(III) It has a step of retaining the recovered catalyst solution (A) in the recovered catalyst solution tank for 1.5 to 6 hours, and the recovered catalyst solution (B) from step (III) is liquid-phase oxidized through the catalyst preparation tank. A process for producing terephthalic acid, characterized in that it is circulated in a reaction system.
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| JP2017095391A (en) * | 2015-11-24 | 2017-06-01 | 三菱化学株式会社 | Manufacturing method of aromatic dicarboxylic acid |
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| JP2017095391A (en) * | 2015-11-24 | 2017-06-01 | 三菱化学株式会社 | Manufacturing method of aromatic dicarboxylic acid |
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