JP2007063152A5

JP2007063152A5 - Method for azeotropic distillation of hydrous acetic acid containing aromatic hydrocarbons

Info

Publication number: JP2007063152A5
Application number: JP2005248105A
Authority: JP
Filing date: 2005-08-29
Publication date: 2007-11-08
Anticipated expiration: 2025-08-29

Description

本発明は、酢酸溶媒中、重金属触媒の存在下、アルキルベンゼンを液相で分子状酸素ガスによる酸化反応を行う芳香族カルボン酸の製造工程における芳香族炭化水素を含有した含水酢酸の共沸蒸留方法に関するもので、詳しくはアルキルベンゼンの酸化反応からの未反応のアルキルベンゼンを、反応溶媒である酢酸の回収系から回収、再使用する方法に関するものである。 The present invention relates to a method for azeotropic distillation of hydrous acetic acid containing an aromatic hydrocarbon in an aromatic carboxylic acid production process in which an alkylbenzene is oxidized with a molecular oxygen gas in a liquid phase in the presence of a heavy metal catalyst in an acetic acid solvent. More specifically, the present invention relates to a method of recovering and reusing unreacted alkylbenzene from the oxidation reaction of alkylbenzene from a recovery system of acetic acid as a reaction solvent.

それらの結果に基づき、芳香族ジカルボン酸製造工程における溶媒酢酸の回収系の共沸蒸留においては、パラキシレンなどの未反応ジアルキルベンゼンを、共沸領域の下限界域（共沸剤濃度０．１ｗｔ％）からでなく、そして直接連続して抜き出すことをせず、共沸蒸留塔内に未反応ジアルキルベンゼンと共沸剤との濃度比が上記範囲内に滞留するまで待つこと、そして、その蓄積濃度比を確認した後、該系内を該濃度比に保持したまま貯槽内に蓄積された留分を間歇的あるいは回分的に抜き出すことにより、ジアルキルベンゼンを高濃度に、安定した留出液として、回収ことが出来ること見出した。 Based on these results, in the azeotropic distillation of the solvent acetic acid recovery system in the aromatic dicarboxylic acid production process, unreacted dialkylbenzene such as paraxylene is removed from the lower limit region of the azeotropic region (azeotropic agent concentration 0.1 wt. %) And without direct continuous withdrawal, wait until the concentration ratio of unreacted dialkylbenzene and azeotropic agent stays in the above range in the azeotropic distillation column, and the accumulation After confirming the concentration ratio, dialkylbenzene can be made into a high concentration and a stable distillate by intermittently or batch-wise extracting fractions accumulated in the storage tank while maintaining the system at the concentration ratio. And found that it can be recovered.

即ち、未反応のジアルキルベンゼンは共沸蒸留塔の共沸領域に蓄積される留分であり、該域内への目標濃度比に蓄積するまで抜き出すことなく保持し、該蓄積された貯槽内留分を間歇的に抜き出す方法を見出した。 That is, unreacted dialkylbenzene is a fraction accumulated in the azeotropic region of the azeotropic distillation column, and is retained without being extracted until it accumulates in the target concentration ratio in the region, and the accumulated fraction in the storage tank is stored. I found a way to extract the data intermittently.

本発明に係る共沸蒸留塔の共沸領域からのアルキルベンゼンを安定した濃度での間歇的あるいは回分的回収法によれば、蒸留塔内の蒸留特性に変動を起こすことがないため、蒸留目的である塔底缶出酢酸中の水分および塔頂留出水中の酢酸混入量の安定性が向上し、かつ共沸剤の同伴を抑えた高濃度アルキルベンゼンの留分を安定的に回収することができる。特に回収留分のアルキルベンゼンと共沸剤との濃度比が約０．５重量比以上乃至約６重量比以下になれば塔頂留出水中の酢酸含有量が低濃度に安定し、酢酸の損失を抑え、排水の処理負荷を低減することができる。 According to the intermittent or batch recovery method of the alkylbenzene from the azeotropic region of the azeotropic distillation column according to the present invention at a stable concentration, the distillation characteristics in the distillation column are not changed, and therefore, for the purpose of distillation. Improves the stability of the water content in acetic acid from the bottom of a column and the amount of acetic acid mixed in the water at the top of the column, and enables stable recovery of fractions of high-concentration alkylbenzene with reduced entrainment of azeotropic agents. . In particular, if the concentration ratio of alkylbenzene and azeotropic agent in the recovered fraction is about 0.5 to 6 weight ratio, the acetic acid content in the overhead water is stabilized at a low concentration, and acetic acid is lost. Can be suppressed, and the wastewater treatment load can be reduced.

ところで、芳香族ジカルボン酸製造における未反応ジアルキルベンゼンは、運転開始当初は酢酸回収工程内には少なく、共沸蒸留塔１系内には低濃度にしか蓄積されていない。そのため、共沸蒸留系内の共沸領域からの留出液を留出液循環ライン１８を用いて二相分離型の留出液貯槽３に抜き出し、分離水相を底部から水相抜き出しライン２１を用いて排出する。そして、留出液貯槽３内の有機相留分を上記共沸蒸留系内に留出液循環ライン１９を用いて循環しながら共沸蒸留塔１内ならびに留出液貯槽３内のアルキルベンゼン留分の滞留量を増やし、留出液貯槽３内のアルキルベンゼンと共沸剤との濃度比を測定器４０で測定し、該測定された濃度比の目標範囲が、図２及び図３に示すように、約０．５重量比以上乃至約６重量比以下、好ましくは約１．０重量比以上乃至約４重量比以下に上昇するまで制御器２４は該循環の継続の制御を行う。留出液貯槽３内のアルキルベンゼンと共沸剤との濃度比が目標範囲に達した後には制御器２４は例えば制御バルブ２３を制御してその循環を停止し、共沸蒸留塔１と留出液貯槽３との連結を遮断した後、例えば制御バルブ２５を開いて留出液貯槽３内の有機相留分を有機相抜き出しライン２０から間歇的に抜き出し、回収する。 Meanwhile, unreacted dialkyl benzene in the aromatic dicarboxylic phosphate production, operation beginning is less in the acetic acid recovery step, the azeotropic distillation tower 1 system not accumulated only in a low concentration. Therefore, the distillate from the azeotropic region in the azeotropic distillation system is withdrawn into the two-phase separation type distillate storage tank 3 using the distillate circulation line 18, and the separated aqueous phase is taken out from the bottom into the aqueous phase withdraw line 21. To discharge. The organic phase fraction in the distillate storage tank 3 is circulated in the azeotropic distillation system using the distillate circulation line 19 while the alkylbenzene fraction in the azeotropic distillation column 1 and the distillate storage tank 3 is circulated. And the concentration ratio of the alkylbenzene and the azeotropic agent in the distillate storage tank 3 is measured by the measuring device 40, and the target range of the measured concentration ratio is as shown in FIG. 2 and FIG. The controller 24 controls the continuation of the circulation until it rises to about 0.5 to about 6 weight ratio, preferably about 1.0 to about 4 weight ratio. The controller 24 after the concentration ratio of the alkylbenzene and the entrainer distillate storage tank 3 has reached the target range stops the circulation by controlling, for example, control valve 23, the azeotropic distillation column 1 and the distillate After the connection with the liquid storage tank 3 is cut off, for example, the control valve 25 is opened, and the organic phase fraction in the distillate liquid storage tank 3 is intermittently extracted from the organic phase extraction line 20 and collected.

一方、図１に示すシミュレーション結果に見られるように、蒸留系内の共沸領域においてもジアルキルベンゼンの高濃度の留出領域の範囲が限られるため、また、共沸領域下限界側での濃度変化が急激であるため、実施にあたっての安定した濃度での抜き出しには蒸留塔１内からの留出位置に注意を要する。それには蒸留塔１における温度を９４〜１００℃であること、ならびに、ある程度の共沸剤の存在が好ましく、抜き出し有機相中の共沸剤（酢酸イソブチル）の濃度が約１５ｗｔ％以上、好ましくは約２０ｗｔ％以上存在することが好ましい。そのため、本発明の方法による安定した、高濃度のアルキルベンゼンの回収には、アルキルベンゼンと共沸剤の濃度比が約０．５重量比以上乃至約６重量比以下、好ましくは約１．０重量比以上乃至約４重量比以下の範囲となる共沸領域が好適である。 On the other hand, as shown in the simulation results shown in FIG. 1, since the range of the high concentration dialkylbenzene distillation region is limited in the azeotropic region in the distillation system, the concentration at the lower limit side of the azeotropic region is also observed. Since the change is abrupt, attention must be paid to the distillation position from the distillation column 1 for extraction at a stable concentration in the implementation. For this purpose, the temperature in the distillation column 1 is preferably 94 to 100 ° C., and the presence of a certain amount of azeotropic agent is preferable, and the concentration of the azeotropic agent (isobutyl acetate) in the extracted organic phase is about 15 wt% or more, preferably It is preferably present at about 20 wt% or more. Therefore, stable according to the method of the present invention, the recovery of a high concentration of alkylbenzene, the concentration ratio of about 0.5 weight above about 6 weight ratio of alkyl benzene and azeotropic agent or less, preferably about 1.0 weight ratio An azeotropic region that is in the range of from about 4 to about 4 weight ratio is preferred .

他方、アルキルベンゼン濃度が濃縮される領域であっても、アルキルベンゼンと共沸剤の濃度比が約６重量比（理論段数約３２段）を超える共沸領域の下限界付近では、後述する表４に示すように、水濃度が急激に高くなり、酢酸濃度も約１０ｗｔ％と高くなり、蒸留塔内の相の安定性ならびに分留性能の低下が起こるため、安定した組成で留出することが困難になる。従って、共沸領域の下限界は、アルキルベンゼンと共沸剤の濃度比が約６重量比以下、好ましくは約４重量比以下で、有機相中の共沸剤の濃度が約１５ｗｔ％以上、好ましくは約２０ｗｔ％以上の領域を選択することになる。 On the other hand, even in the region where the alkylbenzene concentration is concentrated, in the vicinity of the lower limit of the azeotropic region where the concentration ratio of alkylbenzene and azeotropic agent exceeds about 6 weight ratio (theoretical plate number: about 32 plates) , As shown, the water concentration increases rapidly, the acetic acid concentration also increases to about 10 wt%, and the stability of the phase in the distillation column and the fractionation performance decrease, making it difficult to distill with a stable composition. become. Therefore, the lower limit of the azeotropic range is that the concentration ratio of alkylbenzene and azeotropic agent is about 6 weight ratio or less, preferably about 4 weight ratio or less, and the concentration of azeotropic agent in the organic phase is about 15 wt% or more, preferably Will select an area of about 20 wt% or more.

次に、図１乃至図３に示す本発明に至る酢酸脱水塔での共沸蒸留シミュレーションを実施した条件等について説明する。 Next, a description will be given conditions that were carried out azeotropic distillation simulation with acetic acid dehydration column leading to the present invention shown in FIGS.

これらの結果をもとに、蒸留塔内における蒸留塔内組成（水および酢酸イソブチル）及びパラキシレン／酢酸イソブチルの重量比の関係を示したのが図２（理論段数２０〜４４段）であり、蒸留塔内におけるパラキシレン／酢酸イソブチル重量比及び塔内温度を点綴したのが図３（理論段数２０〜４４段）である。 Based on these results, the relationship between the composition in the distillation column (water and isobutyl acetate) and the weight ratio of paraxylene / isobutyl acetate in the distillation column is shown in FIG. 2 (theoretical plate number 20 to 44) . FIG. 3 (theoretical plate number: 20 to 44) shows the weight ratio of para-xylene / isobutyl acetate in the distillation column and the temperature in the column.

［実施例１］
テレフタル製造工程における酢酸回収系において、棚段式（実際段数８０段）の共沸蒸留塔１を用い、共沸剤として酢酸イソブチルを用いた共沸蒸留法により酢酸を脱水し、図４に示す流れのプロセスで酢酸を回収し、パラキシレン含有留分を抜き出し、回収した。図５には、本発明に係るジアルキルベンゼン回収のための操作ステップを示す。 [Example 1]
In the acetic acid recovery system in the terephthalate production process, acetic acid is dehydrated by an azeotropic distillation method using isobutyl acetate as an azeotropic agent using a azeotropic distillation column 1 having a plate type (80 actual plates), and is shown in FIG. Acetic acid was recovered in a stream process, and the paraxylene-containing fraction was withdrawn and recovered. FIG. 5 shows the operation steps for recovering the dialkylbenzene according to the present invention.

そして、蒸留塔１の温度９６〜９８℃を示す実際段数５７段（理論段数約３４段に相当する）の共沸領域から留出液を留出液貯槽３に抜き出す（Ｓ５３）。即ち、実際段数５７段の留出液（液相部）を約１５ｋｇ／ｈｒの割合で留出させ、冷却器４を通し約５０℃に冷却後、内容量約１．５ｍ^３（溢流有機相容量０．７ｍ^３）の二相分離可能な横型留出液貯槽３に導入しのち、溢流有機相留分をレベル検出器２６の液面制御によりポンプ２７を用いて蒸留塔１の実際段数５８段（理論段数約３５段）に還流する方法で行った（Ｓ５５）。該溢流有機相留分中のパラキシレン含有炭化水素濃度（パラキシレン含有率９５ｗｔ％以上のアルキルベンゼン濃度；ＰＸ濃度と称す）と共沸剤の濃度（酢酸イソブチルの濃度；ＩＢＡ濃度と称す）との濃度比を測定器４０で測定しながら、例えば制御器２４は、該濃度比が約０．６重量比（ＰＸ濃度が約３６ｗｔ％で、ＩＢＡ濃度が約６０ｗｔ％に相当する）になるまで蒸留塔１（実際段数５７段）−貯槽３−蒸留塔１（実際段数５８段）の留出液循環ライン１８、１９による循環を継続するように制御した（Ｓ５６、Ｓ５７、Ｓ５８Ｎｏ）。表１に示すように、運転開始から１７日目にＰＸ濃度が３６ｗｔ％を超え、ＰＸ／ＩＢＡの濃度比が約０．６を超えたので（Ｓ５８Ｙｅｓ）、制御器２４は、上記留出液貯槽３への循環の出入りを例えば制御バルブ２３を制御して遮断し（停止し）、蓄積された貯槽３内の留出液有機相留分について弁２５を制御することによって有機相抜き出しライン２０から排出して回収液受槽（図示せず）に高ＰＸ濃度溶液として回収した（Ｓ５９）。なお、上記循環継続中に貯槽３の分離槽底部に分離してくる水相をライン２１を通して抜き出して蒸留塔１の実際段数３６段への供給の原料１３に適時排出して混入した（Ｓ５４）。 And a distillate is extracted to the distillate storage tank 3 from an azeotropic region of 57 actual stages (corresponding to about 34 theoretical stages) showing a temperature of 96 to 98 ° C. in the distillation column 1 (S53). That is, a distillate (liquid phase part) having 57 actual stages is distilled at a rate of about 15 kg / hr, cooled to about 50 ° C. through the cooler 4, and then has an internal capacity of about 1.5 m ³ (overflow organic After introducing into the horizontal distillate storage tank 3 having a phase capacity of 0.7 m ³ ) and capable of separating into two phases, the overflow organic phase fraction is actually used in the distillation column 1 using the pump 27 under the liquid level control of the level detector 26. This was carried out by refluxing to 58 plates (about 35 theoretical plates) (S55). The paraxylene-containing hydrocarbon concentration in the overflow organic phase fraction (alkylbenzene concentration with paraxylene content of 95 wt% or more; referred to as PX concentration) and the azeotropic agent concentration (concentration of isobutyl acetate; referred to as IBA concentration) For example, the controller 24 measures the concentration ratio until the concentration ratio reaches about 0.6 weight ratio (PX concentration is about 36 wt% and IBA concentration is about 60 wt%). Distillation tower 1 (actual plate number 57) -storage tank 3-distillation tower 1 (actual plate number 58) was controlled so as to continue circulation through distillate circulation lines 18 and 19 (S56, S57, S58 No) . As shown in Table 1, since the PX concentration exceeded 36 wt% on the 17th day from the start of operation and the PX / IBA concentration ratio exceeded about 0.6 (S58 Yes) , the controller 24 controls the distillate. For example, the control valve 23 is controlled to shut off (stop) the circulation to and from the storage tank 3, and the organic phase extraction line 20 is controlled by controlling the valve 25 for the accumulated distillate organic phase fraction in the storage tank 3. pressurized et exhaust out recovered receiving tank was recovered (not shown) as a high PX concentration solution (S59). Incidentally, it mixed with timely discharge the raw material 13 for supply to the actual number 36 stage distillation column 1 aqueous phase separates out in the separation tank bottom of the reservoir 3 in the circulation continues withdrawn through a line 21 ( S54).

そして、制御器２４の制御に基づき、留出液貯槽３の有機相内容物排出後、上記と同様の留出液貯槽３への導入を約１０ｋｇ／ｈｒの割合で開始し、留出液貯槽３の溢流有機相が所定液面に到達後循環を再開し、約１５ｋｇ／ｈｒの割合で循環をした。次いで、制御器２４は、蓄積されてアルキルベンゼンが更に高濃度になるのを待ち（３〜５日）（Ｓ５６）、留出液貯槽３内のＰＸ／ＩＢＡの濃度比の測定を測定器４０で行い（Ｓ５７）、確認して濃度比の少なくとも目標（約０．６）を超えたとき弁２３を制御して循環の遮断（ポンプ２７停止）を行い、留出液有機相の回収操作（Ｓ５９）を、弁２５を制御して上記の通りに回収操作を繰り返し行った。 Then, based on the control of the controller 24, after discharging the organic phase contents of the distillate storage tank 3, introduction into the distillate storage tank 3 similar to the above is started at a rate of about 10 kg / hr. After 3 overflow organic phases reached the predetermined liquid level, the circulation was resumed and circulated at a rate of about 15 kg / hr. Next, the controller 24 waits until the accumulated alkylbenzene concentration becomes higher (3 to 5 days) (S56), and measures the concentration ratio of PX / IBA in the distillate storage tank 3 by the measuring device 40. (S57), and when the concentration ratio exceeds at least the target (about 0.6), the valve 23 is controlled to shut off the circulation (stop the pump 27 ) and recover the distillate organic phase ( In S59), the valve 25 was controlled and the recovery operation was repeated as described above.

なお、実施例１と同様、塔頂留出水中１５の酢酸含有量を次の表２に示したが、低含量（０．０３〜０．０５重量％）で安定していることが確認された。 As in Example 1, the acetic acid content of the column top distillate 15 is shown in the following Table 2. It was confirmed that the content was stable at a low content (0.03 to 0.05% by weight). It was.

以上説明したように、本発明に係るアルキルベンゼンの回収法の実施の形態によれば、共沸蒸留塔における系内の蒸留特性を乱すことなく、また、蒸留特性の変動に対しても、留出液貯槽内アルキルベンゼンの高濃度蓄積を待ち、有機相留分を間歇的あるいは回分的に回収することによって、アルキルベンゼンの高濃度留分を安定的に取り出すことを可能にした。 As described above, according to the embodiment of the alkylbenzene recovery method according to the present invention, the distillation characteristics in the system in the azeotropic distillation tower are not disturbed, and the distillation characteristics are also varied with respect to the distillation characteristics. By waiting for high concentration accumulation of alkylbenzene in the liquid storage tank and collecting organic phase fractions intermittently or batchwise, it became possible to stably extract high concentration fractions of alkylbenzene.

ちなみに、蒸留系の蒸留特性の変動あるいは蓄積量の減少などによってアルキルベンゼンが留出されない時期があっても、循環を継続して留出液貯槽の有機相留分に高濃度のアルキルベンゼンの滞留を確認して、有機相留分を間歇的あるいは回分的に回収することによって、回収有機相留分の濃度を高濃度に安定化することが可能となる。 By the way, even when there is a period when alkylbenzene is not distilled due to fluctuations in distillation characteristics of the distillation system or a decrease in the accumulated amount, the circulation is continued and it is confirmed that a high concentration of alkylbenzene remains in the organic phase fraction of the distillate storage tank. Thus, by collecting the organic phase fraction intermittently or batchwise, the concentration of the recovered organic phase fraction can be stabilized at a high concentration.

これは有機相留分の間歇的あるいは回分的抜き出しによって、蒸留系内のアルキルベンゼン濃度を保持し、系内の組成変動が抑制でき、蒸留塔本来の分留性能が安定するためであると考えられる。 This is thought to be due to the fact that the organic benzene fraction can be extracted intermittently or batchwise to maintain the alkylbenzene concentration in the distillation system, to suppress composition fluctuations in the system, and to stabilize the original distillation performance of the distillation column. .

なお、芳香族ジカルボン酸の製造における溶媒回収系から分離されるアルキルベンゼン（ＰＸと称す）には未反応ジアルキルベンゼンが９５ｗｔ％以上含有されており、その他の成分はトルエンなどの脱アルキルされた副生物であった。 The alkylbenzene (referred to as PX) separated from the solvent recovery system in the production of aromatic dicarboxylic acid contains 95% by weight or more of unreacted dialkylbenzene, and other components are dealkylated by-products such as toluene. Met.

従って、芳香族ジカルボン酸製造における溶媒酢酸の回収系において、酢酸イソブチルを共沸剤とした共沸蒸留による脱水塔から未反応ジアルキルベンゼンを高濃度で安定して抜き出すには、該脱水塔共沸領域からアルキルベンゼン含有留分を一旦貯槽に留出し、分離水相を除去したのち、有機相を再び該領域に循環しながらアルキルベンゼン濃度を目標濃度以上にあることを確認し、間歇的あるいは回分的に抜き出すこと。そして、その確認目標濃度をアルキルベンゼンと共沸剤（酢酸イソブチル）との濃度比が約０．５重量以上（アルキルベンゼン濃度約３０重量％以上）、好ましくは約１．０重量以上（アルキルベンゼン濃度約５０重量％以上）を目標とすることによって、より安定した抜き出しを可能にした。 Therefore, in the recovery system of solvent acetic acid in the production of aromatic dicarboxylic acid, in order to stably extract unreacted dialkylbenzene at a high concentration from the dehydration tower by azeotropic distillation using isobutyl acetate as an azeotropic agent, the dehydration tower azeotrope is used. After distilling the alkylbenzene-containing fraction from the region into the storage tank and removing the separated aqueous phase, confirm that the alkylbenzene concentration is above the target concentration while circulating the organic phase again in the region, and intermittently or batchwise. To extract. The target concentration for confirmation is such that the concentration ratio of alkylbenzene to azeotropic agent (isobutyl acetate) is about 0.5 wt. Or more (alkyl benzene concentration of about 30 wt.% Or more), preferably about 1.0 wt. Or more (alkyl benzene concentration of about 50 wt. The more stable extraction was made possible by setting a target of (% by weight or more).

［比較例１］
比較例１は、実施例１と同様の共沸蒸留塔において、蒸留塔１の５７段からの抜き出しを行なうことなく、蒸留塔１の５７段の留分の試料採取によりＰＸ濃度が約３６ｗｔ％になったことを確認した後、５７段から６ｋｇ／ｈｒの割合で定量的に冷却しながら連続して抜き出し、留出液貯槽ならび回収液受槽に蓄積したものである。このようにＰＸ濃度を確認した後、５７段から単に連続して抜き出し、その間、４日置きに抜き出し留分の冷却後試料を採取し（上記貯槽に導入前）、有機相部の組成を測定した結果、次の表３に示す３６日までの組成となった。 [Comparative Example 1]
In Comparative Example 1 , in the azeotropic distillation column similar to Example 1, the PX concentration was about 36 wt% by sampling the 57-stage fraction of the distillation column 1 without extracting from the 57-stage of the distillation column 1. After confirming that the amount of water was reduced, the water was continuously extracted from the 57th stage with quantitative cooling at a rate of 6 kg / hr and accumulated in the distillate storage tank and the recovery liquid receiving tank. After confirming the PX concentration in this way, it was simply extracted continuously from 57th stage, during which time samples were extracted every 4 days and samples were taken after cooling (before being introduced into the storage tank), and the composition of the organic phase part was measured. As a result, the composition up to 36 days shown in the following Table 3 was obtained.

［比較例２］
比較例２は、実施例２において、蒸留塔の実際段数５４段（理論段数約３２段）の留分の試料を採取した場合であり、該採取された留分の試料を冷却後（約３０℃）の有機相の割合ならびその組成分析の結果を表４に示した。なお、その間の５４段の温度は９８〜１０２℃であった。 [ Comparative Example 2 ]
Comparative Example 2 is a case where a sample of a fraction having an actual number of distillation plates of 54 (theoretical plate number of about 32) was collected in Example 2, and the sample of the collected fraction was cooled (about 30). Table 4 shows the ratio of the organic phase (° C.) and the result of the composition analysis. In addition, the 54 stage | paragraph temperature in the meantime was 98-102 degreeC.

本発明に係る酢酸−水−酢酸イソブチレンの共沸蒸留において、パラキシレンが定常的に少量導入された系の数値計算による多成分系蒸留のシミュレーションの結果に基づく蒸留塔内の組成分布を示す図である。The figure which shows the composition distribution in the distillation column based on the result of the simulation of the multicomponent distillation by the numerical calculation of the system in which the para-xylene was constantly introduced in small amounts in the azeotropic distillation of acetic acid-water-isobutylene acetate according to the present invention. It is. 本発明に係る酢酸−水−酢酸イソブチレンの共沸蒸留において、多成分系蒸留のシミュレーションの結果に基づく蒸留塔内組成（水および酢酸イソブチル）と、パラキシレン／酢酸イソブチルの重量比とを理論段数（２０〜４４段）との関係で示す図である。In the azeotropic distillation of acetic acid-water-isobutylene acetate according to the present invention, the number of theoretical plates represents the composition in the distillation column (water and isobutyl acetate) based on the simulation results of multi-component distillation and the weight ratio of paraxylene / isobutyl acetate. It is a figure shown by the relationship with (20-44 steps) . 本発明に係る酢酸−水−酢酸イソブチレンの共沸蒸留において、多成分系蒸留のシミュレーションの結果に基づく蒸留塔内温度とパラキシレン／酢酸イソブチルの重量比の傾向とを理論段数（２０〜４４段）との関係で示す図である。In the azeotropic distillation of acetic acid-water-isobutylene acetate according to the present invention, the temperature in the distillation column and the tendency of the weight ratio of paraxylene / isobutyl acetate based on the simulation results of multi-component distillation are calculated from the theoretical plate number (20 to 44 plates). ) . 本発明に係る共沸蒸留による酢酸の脱水とジアルキルベンゼン回収のための流れの一実施の形態を示す図である。It is a figure which shows one Embodiment of the flow for the dehydration of acetic acid by diazeotropic distillation and dialkylbenzene collection | recovery based on this invention. 本発明に係る共沸蒸留による酢酸の脱水とジアルキルベンゼン回収のための操作ステップを示すフロー図である。It is a flowchart which shows the operation step for the dehydration of acetic acid by diazeotropic distillation and dialkylbenzene collection | recovery based on this invention.

Claims

In the recovery system of solvent acetic acid in the production of aromatic dicarboxylic acid, a method of performing azeotropic distillation using hydrous acetic acid containing aromatic hydrocarbon as a distillation raw material ,
(1) using an azeotropic agent that forms an azeotropic composition with water,
(2) Supply the distillation raw material to the acetic acid concentration region,
(3) After the alkylbenzene-containing fraction is extracted from the azeotropic region into the distillate storage tank and circulated in the azeotropic region, the circulation is continued until the ratio of the concentration of alkylbenzene and azeotropic agent reaches the target range. , and exits disconnect the fraction of the distillate storage tank intermittently or batchwise,
(4) Condensed distillate from the top of the column, phase-separating the condensate, and stable product water with a low acetic acid content;
(5) A method for azeotropic distillation of hydrous acetic acid containing aromatic hydrocarbons, wherein dehydrated acetic acid having a water concentration of 2 to 8% by weight is recovered from the bottom of the tower .

The method for azeotropic distillation of hydrous acetic acid containing aromatic hydrocarbons according to claim 1, wherein the target range of the concentration ratio of alkylbenzene and azeotropic agent is 0.5 to 6 weight ratio .

The method for azeotropic distillation of hydrous acetic acid containing an aromatic hydrocarbon according to claim 1 or 2, wherein isobutyl acetate is used as an azeotropic agent .

The azeotropic distillation of hydrous acetic acid containing an aromatic hydrocarbon according to any one of claims 1 to 3, wherein the distillation raw material is supplied to an acetic acid concentration region in which the water concentration is about 90% by weight or less. Way .

The alkylbenzene fraction extracted intermittently or batchwise from the azeotropic region is reused directly or indirectly for the production of aromatic dicarboxylic acid. A method for azeotropic distillation of hydrous acetic acid containing an aromatic hydrocarbon .

The water-containing aromatic hydrocarbon according to any one of claims 1 to 5, wherein the aromatic dicarboxylic acid is terephthalic acid, and the alkylbenzene is paraxylene as a raw material for producing the carboxylic acid. A method for azeotropic distillation of acetic acid .

The aromatic according to claim 1 or 2, wherein a distillate in a temperature range of 94 to 100 ° C in the azeotropic region of the azeotropic distillation column is distilled and circulated into the distillate storage tank. A method for azeotropic distillation of hydrous acetic acid containing hydrocarbons .