JP2004149421A - Method for separating dimethylamide compound and carboxylic acid by distillation and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that water is produced and mixed in purified dimethylamide, and to provide the high-purity dimethylamide containing slight impurities when quinolines are added to a maximum azeotropic composition of a mixture liquid of a carboxylic acid and the dimethylamide to separate the carboxylic acid and dimethylamide by distillation. <P>SOLUTION: The purified dimethylamide is taken out from a position at the intermediate height of a dimethylamide purifying distillation column in the distillation column. Thereby, the water produced in the distillation column as a minor impurity can be enriched to an overhead distillate and separated. As a result, the high-purity dimethylamide containing the slight impurities is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【００８４】
以下、実施例２と比較例２は、蒸留搭１本用いた装置である。
【００８５】
（実施例２）
蒸留塔としてステンレス製円筒（外径：６０ｍｍ、内径：５５ｍｍ、全長：約２５００ｃｍ）に、充填材としてステンレス製ディクソンパッキン（６ｍｍφ）を円筒内部に充填したものを１本用いた。蒸留搭の構成は、実施例１の第１塔と同様にした。塔頂部はコンデンサーを設置し、凝縮液留出と塔頂部への還流を行なう。塔底部はリボイラーがあり液抜き出しする。塔の中ほどの高さ位置からは原料液供給とサイドカット液抜き出しを行なう。塔頂から３０ｃｍ程度の充填部分を隔てた位置にサイドカット液抜出し位置を設け、サイドカット位置から更に下方３０ｃｍ程度の充填部分を隔てたところに原料混合液を供給する。
【００８６】
蒸留塔への原料混合液を流量３６８ｇ／ｈで供給した。原料混合液の組成は、ＤＭＦ：３３．７％，酢酸：１１．３％、イソキノリン：５４．１％、水分：０．００４７％である。塔頂部での還流比を約２０として、流量１５０ｇ／ｈ程度の還流液を流下させた。蒸留塔頂部からの留出液は、流量７．４ｇ／ｈとすると、その成分は概ねＤＭＦであり水分が約０．５％、ＤＭＡが約０．１％含まれていた。
【００８７】
サイドカット部では、塔頂部還流流下液（約１５０ｇ／ｈ）を全量塞き止めて、側近に設けた５０ｍｌ程度の受槽へ導管を通じて流通させ、その液の一部（７４ｇ／ｈ）をサイドカットして精製ＤＭＦとして抜き出した。残りの液は再び塔内に戻して落下させた。精製ＤＭＦ中の水分は０．００７％であり、ジメチルアミン含有量は０．００２％程度、酢酸も０．００３％であった。サイドカットからのジメチルホルムアミドの取り出し割合は、９８．９％である。
【００８８】
その下方に更に３０ｃｍ程度の充填部を隔てて塔底部の液溜りがあり、リボイラーとして加熱蒸発させるとともに塔底液を一定量（流量２７１ｇ／ｈ）抜き出す。塔底部抜き出し液組成はＤＭＦ：１６％，酢酸１５％、イソキノリン：６８％などであった。
【００８９】
蒸留塔塔底液はリボイラーで１００℃に加熱し、真空ポンプを用い排気することにより、塔内部空間の圧力条件を調整し、操作圧力は６．０ｋＰａ−ａｂｓ．とした。
【００９０】
（比較例２）
実験に用いた蒸留塔はガラス製で内径３０ｍｍφ、全長約１５００ｍｍの円筒に充填材（ガラス製ラッシッヒリング３ｍｍφ）を入れたものである。塔底部リボイラーから塔頂部コンデンサーまでの全高さは約２５００ｍｍである。塔中段位置からの原料液供給を流量１２２ｇ／ｈとし、その組成はＤＭＦ２９％，酢酸１１％、イソキノリン５９％で水０．００５％程度である。
【００９１】
サイドカット液の抜出しをすることはせず、塔頂部留出液を２２ｇ／ｈとしてＤＭＦを取り出したところ、水分が０．０８％程度、ジメチルアミン０．０１％程度および無水酢酸０．０００５％が検出された。塔頂部の還流比は１とした。
【００９２】
塔底部払出し液を流量１００ｇ／ｈとし、組成はＤＭＦ１５％，酢酸：１３％、イソキノリン：７２％程度、無水酢酸：０．００２５であった。また、イソキノリンの０．００５％程度がメチルイソキノリンに変成していることが検出された。蒸留塔の操作圧力は６．７ｋＰａ−ａｂｓ．とした。温度は１００℃程度とした。
【００９３】
（実施例２と比較例２との比較）
比較例２で得られたジメチルホルムアミドは水分０．０８％とジメチルアミン０．０１％を含んでいることに対して、本発明の方法による実施例２で得られたジメチルホルムアミド中の水分は０．００７％およびジメチルアミンは０．００２％であり比較例２に比べて不純物含有量を著しく低減することができた。
【００９４】

【００９５】
実施例３と比較例３は、蒸留搭４本用いた装置である。
【００９６】
（実施例３）
蒸留塔としてステンレス製円筒（外径：６０ｍｍ、内径：５５ｍｍ）に、充填材としてステンレス製ディクソンパッキン（６ｍｍφ）を円筒内部に充填したものを４本用いた。それぞれ脱水蒸留塔（長さ：約２０００ｍｍ）、ＤＭＦ精製蒸留塔（長さ：約２５００ｍｍ）、酢酸除去蒸留塔（長さ：約２５００ｍｍ）、イソキノリン回収蒸留塔（長さ：約１０００ｍｍ）とした。ＤＭＦ精製蒸留塔と酢酸除去蒸留塔は、実施例１の第１塔、第２塔と同様の構成とした。脱水蒸留塔は、リボイラーを塔底に接続し、塔底から充填材を２５ｃｍ充填、空間部１５ｃｍを設け、さらに充填材を２０ｃｍ充填し、その上の空間部１５ｃｍに原料液供給部を設ける。その上に充填材４５ｃｍを設け、その上を塔頂部とした。イソキノリン回収蒸留塔の構造は、リボイラーに接続した塔底から順にその上に充填材３０ｃｍを設け、この中間高さ１５ｃｍのところに原料液を供給する。その上を塔頂部とした。
加水分解反応器＋脱水蒸留器＋ＤＭＦ精製蒸留器＋酢酸除去蒸留搭は、この順に配管で連結されている。加水分解反応器としてステンレスチューブ（内径４ｍｍφ、長さ１０ｍを用いた。
ＤＭＦ精製蒸留塔、酢酸除去蒸留塔、イソキノリン回収蒸留塔の塔頂部には、コンデンサーが接続されている。コンデンサーは、蒸気を液化してその１部分を塔頂部留出液として取り出すとともに、残りの液を塔頂部に還流するように接続した。
【００９７】
原料液の組成はＤＭＦ：７０％，酢酸：１１％、無水酢酸：１２％、イソキノリン：２．５％，水：３．５％程度であり、これを定量ポンプでにて流量４２ｇ／ｈ送液して該加水分解反応器を流通させた。反応器温度を８０℃に維持し、出口に圧力制御弁を付けて反応器内の圧力を０．２ＭＰａとした。反応器出口では９９％以上の転化率で無水酢酸が酢酸に変換された。反応器を出た液を引き続いて脱水蒸留塔に供給し、水を分離して塔頂部から留出させて、その留出水を再び加水分解反応器入口へ循環供給した。脱水塔頂部の還流比は０．５程度とした。脱水蒸留塔の操作圧力は１２．０ｋＰａ−ａｂｓ．とした。
【００９８】
脱水蒸留塔頂部留出水にはジメチルアミンが生成して含まれていたが、加水分解反応器の出口ではジメチルアセトアミドに転化していた。脱水蒸留搭等頂から留出する水を主成分とする液を流量約１０ｇ／ｈで加水分解反応器入口へ循環供給することによって、加水分解反応器の水濃度が２０重量％まで上昇するようにした。脱水蒸留塔塔底部から水分を取り除いた液を抜き出し、流量５０ｇ／ｈ程度でジメチルホルムアミド精製蒸留塔の塔底部から充填材を３００ｍｍ隔てた高さ位置に供給した。
【００９９】
ジメチルホルムアミド精製蒸留塔の塔頂液は、コンデンサーで凝縮液化されて、その一部は塔頂部留出液とし、その残りは、蒸留搭塔頂部に還流する。還流比は約１１で、操作圧力を６．０ｋＰａ−ａｂｓ．とした。該精製蒸留塔頂部から流量８．５ｇ／ｈの液を留出させ、これも加水分解反応器入口へ循環供給した。
【０１００】
精製塔頂部留出ＤＭＦは水を約０．３５％およびジメチルアミン約０．１％を含んでいた。塔頂から３０ｃｍ程度下部の位置で精製ＤＭＦを流量２６ｇ／ｈでサイドカット抜出ししたところ、ＤＭＦ中の不純物として水０．００８％でＤＭＡは０．００２％であった。サイドカットからのジメチルホルムアミドの取り出し割合は、７５．４％である。
【０１０１】
精製蒸留塔底部の液組成はＤＭＦ：２３％，酢酸：１５％、イソキノリン：４３％などが主成分であり、約３００ｇ／ｈにて抜出して、酢酸除去蒸留塔の塔底部から上方に充填材を３００ｍｍ隔てた位置へ供給した。酢酸除去蒸留塔の塔頂還流比は１５として、圧力は７．３ｋＰａ−ａｂｓ．で操作した。
【０１０２】
「酢酸除去蒸留搭」の留出液流量約１０ｇ／ｈの組成は酢酸：９０％、ＤＭＦ：１０％程度になった。塔頂から３０ｃｍほど下の位置の液を流量約７０ｇ／ｈにてサイドカット抜出しし、その内３ｇ／ｈをパージして残りをジメチルホルムアミド精製蒸留塔の塔底部から充填材を１５０ｍｍ隔てた高さの位置へ供給した。
【０１０３】
該サイドカット液の組成は、ＤＭＦ：５９％，酢酸：３７％、ジメチルアセトアミド：４％などであった。「酢酸除去蒸留塔」塔底部には高沸点成分が濃縮されており、イソキノリンが８０％程度含まれており、残りの成分は原料液に含まれている、さらに高沸点を有する各種未同定物質であった。その塔底液を抜出して約２００ｇ／ｈにてイソキノリン精製蒸留塔の塔底から上方へ充填材を１５０ｍｍ隔てた高さ位置へ供給した。
【０１０４】
酢酸除去蒸留塔底部のイソキノリンおよびその他の高沸点物質は、供給原料液から僅かずつもたらされ、徐々に蓄積増量してくる。このため、この増加分の液を抜出してイソキノリン回収蒸留処理する操作を行なった。試験規模が小さいので処理液を溜めてから流量約５０ｇ／ｈにてイソキノリン回収蒸留塔へ供給した。イソキノリン回収塔の塔頂還流比を１０として圧力を５．３ｋＰａ−ａｂｓ．で操作し、塔頂留出を約３６ｇ／ｈとすることにより純度９５％以上の精製イソキノリンが得られた。塔底液は残存イソキノリン濃度２０％程度まで濃縮して払出した。
【０１０５】
水発生の状況を調べるために観察を行なった。
【０１０６】
（参考例１）
１００ｃｃのガラス容器にジメチルホルムアミド、酢酸およびイソキノリンを重量比でそれぞれ２５％、１０％、６５％の混合比で仕込み、１２０℃に維持して、時間経過に伴う無水酢酸の濃度を分析測定した。仕込当初の無水酢酸は検出されなかったが、１時間経過後のガラス容器内の液からは０．０１４％、２時間経過後には０．０２９％の無水酢酸が検出された。
【０１０７】
参考例１の結果によればジメチルホルムアミド、酢酸、イソキノリンの混合溶液で無水酢酸が発生した。このことから推定すると、上記実施例１，２，３および比較例１，２において蒸留塔で水が発生している原因のひとつとして：
酢酸 → 無水酢酸 ＋水
の反応が生じている可能性が考えられる。
【０１０８】
ただし、比較例２で検出されている水の量に比べて無水酢酸量は極めて少量でありその他に原因があるものと考えられる。その他の原因としては、比較例２において観察されたメチルイソキノリンの発生と関係があることが考えられる。推定される反応としては：
イソキノリン＋酢酸→メチルイソキノリン＋蟻酸
蟻酸→水＋一酸化炭素
である。以上のような反応により、水が発生すると考えられる。
【０１０９】
【発明の効果】
以上説明したように、本発明にかかるジメチルアミド化合物とカルボン酸を蒸留分離する方法によれば、キノリン化合物をエントレーナーとして用いた蒸留方式を改良し、不純物の混入を克服した純度の高い精製ジメチルアミド化合物を得ることができる。また、本発明の方法を適用した装置は、ジメチルアミド化合物精製蒸留塔にて、塔中間高さから精製ジメチルアミド化合物を取り出すことにより、微量不純物として蒸留塔内で発生した水は塔頂留出分へ濃縮されて分離でき、不純物の少ない純度の高いジメチルアミド化合物が得られる。
【図面の簡単な説明】
【図１】３つの蒸留塔で構成される本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置の概念図である。
【図２】２つの蒸留塔で構成される本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置の概念図である。
【図３】２つの蒸留塔と付加装置で構成される本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置の概念図である。
【符号の説明】
１０；本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置の１例
１２；第１塔
１４；第２塔
１６；第３塔
１８；第１塔原料液供給管
２０；第１塔塔頂留出管
２２；第１塔中間部払出し管
２４；第１塔塔底部缶出管
２６；第２塔供給管
２８；第２塔塔底部缶出管
３０；循環供給管
３２；第２塔塔頂留出管
３４；第３塔供給管
３６；第３塔塔頂留出管
３８；第３塔塔底部缶出管
３９；分岐管
５０；本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置の他の１例
５２；第１塔
５４；第２塔
５６；原料混合液供給管
５８；第１塔塔底部缶出管
６０；第１塔中間部払出し管
６２；第２塔供給管
６４；第２塔塔底部缶出管
６５；第２塔中間部払出し管
６６；循環供給管
７０；本発明のジメチルアミド化合物とカルボン酸を蒸留分離する装置のさらに他の１例
７２；第１塔
７４；第２塔
７６；加水分解反応器
７８；脱水蒸留器
８０；キノリン類回収蒸留塔
８２；原料液供給管
８４；第１塔塔頂留出液管
８６；第１塔中間部払出し管
８８；第１塔塔底部缶出管
９０；第２塔供給管
９２；第２塔塔頂留出管
９４；第２塔塔底部缶出管
９６；循環供給管
９８；第２塔中間部払出し管
１００；分岐管
１０２；原料液供給管
１０４；蒸留搭供給管
１０６；蒸留塔塔底部缶出管
１０８；脱水蒸留搭塔底部缶出管
１１０； 循環供給管
１１２；キノリン類供給管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique used for separating a mixed solution containing a carboxylic acid and a dimethylamide compound into components.
[0002]
Problems to be solved by the prior art and the invention
As the dimethylamide compound, dimethylformamide, dimethylacetamide, and the like are used as solvents in many production processes. These are also used as solvents in the polymerization step of various polymer compounds and in the molding step of fibers, artificial leathers, films and the like.
[0003]
In these steps, a carboxylic acid may be mixed into a dimethylamide compound as a solvent. Specifically, acetic acid may be mixed in the recipe of the production process, or may be converted to acetic acid by hydrolysis of acetic anhydride. Alternatively, formic acid may be generated by hydrolysis of dimethylformamide, or acetic acid generated by hydrolysis of dimethylacetamide may be included.
[0004]
As described above, when used as a solvent in a production process, or when a reaction raw material is discharged without being reacted, or when discharged as a reaction product, it is often a mixed state of various components. Solvents and unreacted substances need to be separated into individual components and used again in the production process, or even in production processes in which those substances are products, it is necessary to separate and extract the target substance alone.
[0005]
However, if a distillation operation is performed to separate and extract each component from a mixed solution containing a carboxylic acid and a dimethylamide compound, it is difficult to completely separate the two components because the two components form the highest azeotropic mixture. It is.
[0006]
For example, acetic acid has a boiling point of 118 ° C. and dimethylformamide has a boiling point of 153 ° C. In a distillation operation at normal pressure, for example, a mixed solution in which the ratio of acetic acid to dimethylformamide is about 33/66 by weight is: When the boiling point rises to about 165 ° C., it cannot be separated because it evaporates while maintaining its mixing ratio. Thus, for example, when a mixed solution of 10 g of acetic acid and 90 g of dimethylformamide is distilled, 10 g of acetic acid and 20 g of dimethylformamide become the highest azeotropic mixture, so that 70 g of dimethylformamide can be separated, but the highest azeotropic mixture must be separated and recovered. Can not.
[0007]
In the case of dimethylformamide and formic acid, the highest azeotropic mixture having a boiling point of 163 ° C. is formed at a mixing ratio of about 31/69 by weight. Dimethylacetamide also forms the highest azeotrope with formic acid and acetic acid.
[0008]
As described above, when the mixture of the carboxylic acid and the dimethylamide compound becomes an azeotropic composition and it becomes difficult to recover the dimethylamide compound, prior to the distillation operation, the acetic acid component is converted to an alkali such as caustic soda. For neutralization. Then, after a salt such as sodium acetate is generated by the neutralization reaction, the salt that has become a solid content is removed by means such as an evaporation treatment. According to this method, a solution containing no acetic acid is obtained. For example, there is known a method of adding an amino compound to a neutralization point to dimethylformamide containing formic acid discharged in a polyurethane production process, and then purifying dimethylformamide by distillation (for example, Patent Document 1). The solution thus obtained can be distilled to separate and recover dimethylformamide. However, this method cannot recover the acetic acid component, imposes a large burden on the neutralization reaction / solids separation operation, and has the difficulty of treating solid waste.
[0009]
As another means for solving the problem of the azeotropic composition in the distillation separation, there is a method of adding a solvent that acts as an entrainer (for example, Patent Documents 2 and 3). In a method in which toluene is used as an entrainer and acetic acid is separated by azeotropic distillation with toluene, acetic acid can be extracted into water and subjected to wastewater treatment.
[0010]
On the other hand, there is a method using a distillation method using isoquinoline or the like as an entrainer. According to this method, in order to distill and separate the highest azeotropic mixture composition of acetic acid and dimethylformamide, isoquinoline is added to shift the azeotropic composition toward the acetic acid-rich concentration direction. Excess dimethylformamide can be removed as vapor. Therefore, in this method, each component can be isolated without requiring wastewater treatment.
[0011]
However, when dimethylformamide obtained as described above is applied to various uses, contamination of impurities becomes a serious problem. For example, when dimethylformamide is used as a polyimide polymerization solvent, it is necessary to reduce the water content in dimethylformamide (for example, Patent Document 4).
[0012]
However, it has been found in the study of the present invention that dimethylformamide extracted by a method of adding a quinoline compound (for example, Patent Document 5) contains water as an impurity. In other words, the present inventors have newly found a problem that water is mixed into the obtained dimethylformamide even when the test is performed using a raw material liquid from which water has been removed by sufficient dehydration distillation.
[0013]
Along with the above-mentioned water mixing problem, the generation of impurities due to the hydrolysis reaction of the dimethylamide compound also became a problem. For example, in the hydrolysis of dimethylformamide, it is known that dimethylamine and formic acid are generated by a side reaction (for example, Non-Patent Document 1).
[0014]
Under these conditions, the reason for the generation of water is not clear. Although it is assumed that acetic acid is split into water and an acid anhydride, the equilibrium of this reaction is biased toward the acetic acid side, and it is unlikely that water is generated. However, water is evolved as a reaction that occurs only in the presence of isoquinoline. The contamination of water, which is an impurity generated in such a small amount, is a phenomenon newly discovered by performing a distillation separation method using a quinoline compound, and the purity of dimethylformamide taken out by distillation is reduced. Cause. Therefore, it becomes a serious problem in applications requiring high purity.
[0015]
As means for removing water in dimethylformamide, a dehydration distillation method has been conventionally known (for example, Non-Patent Document 2 and Non-Patent Document 3). In this dehydration distillation operation, dimethylamine and formic acid are generated by hydrolysis of dimethylformamide, and dimethylamine is removed together with water as a low-boiling substance. However, formic acid remains in the highest azeotropic composition with dimethylformamide. Therefore, in order to obtain dimethylformamide having a high purity, a distillation operation for separating and removing formic acid is required subsequently, and there has been a problem that distillation equipment and distillation operation and energy consumption are large.
[0016]
The present invention is intended to improve the practical problem by improving the latter distillation method using a quinoline compound.
[0017]
[Patent Document 1]
Japanese Patent Publication No. 58-57421
[Patent Document 2]
Japanese Patent Application 2002-166994
[Patent Document 3]
Japanese Patent Application 2001-158870
[Patent Document 4]
JP-A-6-87958
[Patent Document 5]
Japanese Patent Application 2001-158870
[Non-patent document 1]
Journal of Chemical Engineering, Vol. 16, No. 2, p. 391, Tsuneaki Fujiwara, 1990
[Non-patent document 2]
Shinji Hattori, Chemical Equipment, November, 1980, p. 33-50
[Non-Patent Document 3]
Masamichi Sugita; Chemical Equipment March 1984 p. 54-58
[0018]
[Means for Solving the Problems]
The present inventors have conducted intensive studies with the aim of overcoming the contamination of impurities caused by water generation in the conventional method, and as a result, completed the present invention. That is, the present invention:
A method in which quinolines are added to a raw material mixture containing a dimethylamide compound and a carboxylic acid and distillation is performed. A distillation separation method and apparatus, characterized in that the distillation is carried out from the top of the column, and the remainder is withdrawn as a further purified dimethylamide compound from an intermediate height position of the distillation column.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The raw material mixture used for distillation in the method of the present invention is a mixture containing a carboxylic acid such as acetic acid and a dimethylamide compound such as dimethylformamide. The present invention is characterized in that quinolines are added to a raw material mixture and distilled.
[0020]
As the raw material mixture, the composition formula (CH ₃ ) ₂ NCOR, where R is H, CH ₃ , CHCH ₂ A dimethylamide compound selected from the group consisting of: and a composition formula: C _n H _{2n + 1} Examples thereof include a combination of a carboxylic acid represented by COOH, wherein n is selected from 0, 1, 2, and a carboxylic acid such as acetic acid and formic acid, and a dimethylamide compound such as dimethylformamide and dimethylacetamide. For example, a combination in which the carboxylic acid is acetic acid and the dimethylamide compound is dimethylformamide in the raw material mixture. In the raw material mixture, the content of the dimethylamide compound is preferably higher than the carboxylic acid by weight. Examples of quinolines include quinoline, isoquinoline, and methylquinoline. Since a mixture of these carboxylic acids and a dimethylamide compound forms the highest azeotropic composition, it is difficult to separate them by ordinary distillation methods. The quinolines may be contained in the raw material mixture in advance, or may be added for a distillation operation.
[0021]
The distillation operation of the present invention can be performed using a normal distillation column, and it is not necessary to manufacture a special apparatus. The distillation column is basically a single distillation column for purifying a dimethylamide compound, and can realize the method of the present invention. The distillation tower may be a combination of two or more towers. In order to more efficiently and accurately separate the solvent, a combination of two or more columns is preferable.
[0022]
Supply the raw material mixture to the distillation column. The raw material mixture is preferably supplied from near the middle position of the distillation column. The supply of the raw material mixture can be selected from one or a plurality of locations near the middle position of the distillation column. The supplied raw material liquid is introduced into a distillation column and subjected to a distillation operation, so that it can be separated and taken out into components that are heated and evaporated to distill at the top of the column and components from the bottom of the column. The “middle position” is a position above the bottom of the distillation column and below the position for removing the purified dimethylamide compound.
[0023]
The components at the bottom of the tower are the highest azeotropic composition of a carboxylic acid and a dimethylamide compound having a high boiling point, and the added quinolines, which are both collected at the bottom of the tower and discharged. At the top of the column, the dimethylamide compound in excess of the highest azeotropic composition evaporates and reaches the top of the column due to its relatively low boiling point. This dimethylamide compound is distilled.
[0024]
The most important and essential embodiment of the present invention is that, of the dimethylamide compound evaporated to the top of the column, an amount of 1% to 50% by weight of the dimethylamide compound is distilled off from the top of the column, and the remainder is further distilled. This is to take out the purified dimethylamide compound (hereinafter, referred to as a purified dimethylamide compound) from the intermediate height position of the distillation column. In the present invention, the concentration of quinolines in the bottom liquid at the bottom of the distillation column can be 10% by weight to 95% by weight.
[0025]
In the present invention, the "intermediate height position" for removing the purified dimethylamide compound from the distillation column is a position at least one or more theoretical plates higher than the height position at which the raw material liquid is supplied to the distillation column, and The position is at least one stage lower than the position at which the reflux liquid at the top of the distillation column is supplied. A more preferable “intermediate height position” is a position that is higher by 5 or more stages with respect to the height position at which the raw material liquid is supplied to the distillation column, and is 5 positions higher than the position at which the top reflux liquid of the distillation column is supplied. It is a position lower than the step. Here, "the supply height of the raw material liquid to the distillation column" is the middle position of the distillation column. Further, the “position at which the reflux liquid at the top of the distillation column is supplied” is the top.
[0026]
As the position at which the purified dimethylamide compound is removed from the distillation tower is higher with respect to the height position at which the raw material liquid is supplied to the distillation tower, the purified dimethylamide compound extracted from the intermediate height has an impurity as an impurity. Advantageously, the incorporation of carboxylic acid and the incorporation of high-boiling quinolines can be easily reduced, or the heat energy can be reduced by reducing the overhead reflux ratio in distillation. In addition, the lower the position where the reflux liquid at the top of the distillation column is supplied, the lower the level of contamination of dimethylamine and water as low boiling impurities in the purified dimethylamide compound extracted from the intermediate height. The advantage is that the energy can be easily reduced, or the heat energy can be reduced by reducing the overhead reflux ratio in distillation. Therefore, the intermediate height position of the distillation column is preferably an intermediate position between the raw material supply position and the position for supplying the top reflux liquid. The purified dimethylamide compound withdrawn from the intermediate height position of the distillation column has an impurity contained in a weight ratio of 1/1000 to 1/3 that of the dimethylamide compound distilled from the top of the distillation column. Can result in significantly less purification.
[0027]
Here, “one-stage” is an actual one-stage plate in a plate-type distillation tower, but also in a case where a gas-liquid contact method using a filler is used and a plate is not used, It means the height of the packing material that provides the distillation separation performance corresponding to one tray plate. Such a theoretical stage of the filler is described as “HETP” (high equivalent to a theoretical plate) in, for example, page 134 of the fourth edition of the Physical and Chemical Dictionary (Iwanami Shoten, 1987). The quantitative treatment is clearly described in, for example, Chemical Engineering Handbook Revised 6th Edition (edited by the Society of Chemical Engineers, Maruzen, 1999), page 598.
[0028]
Various impurities behave as follows. That is, the liquid condensed by the condenser is distilled off at the top of the tower, and a part of the liquid is refluxed from the top of the tower, and the liquid and the vapor come into contact with each other. By the contact, components having a low boiling point among the impurities contained in the vapor are further carried to the top of the column, concentrated and discharged. In addition, it has been found in the study of the present invention that water is generated in this distillation method using quinolines, but water having a relatively low boiling point is concentrated toward the upper part of the distillation column. The water causes hydrolysis of the dimethylamide compound to generate dimethylamine. Since dimethylamine has a low boiling point, it is further discharged to the top of the column. In addition, formic acid generated simultaneously in this hydrolysis reaction forms a highest azeotropic mixture with the dimethylamide compound, acts as a high-boiling substance, and is concentrated at the bottom of the distillation column.
[0029]
As described above, in the process in which the liquid condensed in the condenser at the top of the column is refluxed and flows down, by contacting the distillation component vapor, low-boiling impurities such as water and dimethylamine are diffused to the upper part, and formic acid is removed. Separated to the bottom of the tower. Therefore, the liquid containing dimethylformamide as the main component, which is taken out from the column intermediate height, can be obtained as a more purified dimethylamide compound having less impurities.
[0030]
Such side reactions in which water is generated or hydrolysis occurs become remarkable as the operating temperature increases, but can be adjusted by lowering the operating pressure of the distillation column to lower the distillation temperature. In this respect, a preferable range of the distillation temperature is 50 ° C to 200 ° C, and more preferably 80 ° C to 120 ° C.
[0031]
Increasing the ratio of the dimethylamide compound fraction withdrawn from the top of the tower can prevent impurities such as water and dimethylamine from being mixed into the purified dimethylamide compound liquid taken out from the middle position of the tower. . However, on the other hand, the extraction amount of the more purified dimethylamide compound decreases. Therefore, it is preferable that the ratio of the dimethylamide extracted from the column to the total amount of dimethylamide taken out is in the range of 1% by weight to 50% by weight. More preferably, when the content is 5% by weight or more, moisture can be removed more stably. On the other hand, when the content is 30% by weight or less, the amount of the purified dimethylamide compound taken out from the intermediate height position of the column is increased, and the operation can be performed more efficiently.
[0032]
When the reflux ratio at the top of the distillation column (= reflux amount / distillate amount) is increased, impurities in the purified dimethylamide compound can be reduced. The reflux ratio can be about 1 to 50, preferably in the range of 5 to 20.
[0033]
The present invention is characterized in that the dimethylamide compound liquid is extracted from the intermediate height position of the distillation column. In a preferred embodiment, only the liquid flowing down from a certain position in the distillation column is discharged in its entirety, a certain amount is withdrawn as a more purified dimethylamide compound, and the remaining liquid can be returned to the distillation column and flow down. At this time, the vapor component in the distillation column rises in the column without being extracted.
[0034]
More specifically, the liquid flowing down the entire section inside the column is blocked at the intermediate height position of the distillation column, and the entire amount of the liquid is discharged and introduced into the receiver. Next, a part of the liquid is discharged from the receiver as a purified dimethylamide compound by a pump or the like. The remaining liquid is refluxed immediately below the closed position to discharge the liquid from the distillation column, and can be dispersed again over the entire column cross section and allowed to flow down. At this intermediate position of the distillation column, the flowing liquid is blocked, but the distillation vapor in the column can be raised without blocking.
[0035]
In this case, the amount of liquid extracted as the purified dimethylamide compound is preferably not more than half the amount of liquid flowing down the column. If the amount of liquid to be withdrawn is too large, the amount of liquid flowing down in the lower part of the column may be small, and the gas-liquid contact performance may be reduced. In addition, when the amount of liquid to be withdrawn exceeds the majority, the effect of slight fluctuations in the flow rate and the amount of liquid flowing down in the tower on the amount of liquid flowing down to the lower part of the tower becomes significant, and there is no liquid in the lower part of the tower. Problems may occur.
[0036]
In the present invention, the problem that water is mixed as an impurity cannot be solved by physically separating what is mixed and introduced into the feedstock to the distillation column. It is presumed that water is generated by a chemical reaction inside the distillation column. However, in the present invention, it has been found that the problem can be solved by concentrating water at the time of distilling off the dimethylamide compound at the top, and extracting the purified dimethylamide compound from the liquid at the column intermediate height position. . That is, the contamination of water can be substantially eliminated, and a chemically reactive substance such as acetic acid, acetic anhydride, and quinoline which is considered to be related to the generation of water does not enter the purified dimethylamide compound.
[0037]
An additional embodiment of the method of the present invention is a method comprising a dehydration distillation step preceding the basic distillation operation. In this method, the components distilled off from the top of the dimethylamide compound purification distillation column can be supplied to the dehydration distillation column for the dehydration distillation step and recycled. By removing the water contained in the dimethylamide compound by the dehydration distillation step, the mixed solution having a water concentration of 0.1% by weight or less, more preferably 0.01% by weight or less, is subjected to the next purification distillation Can be fed to the tower. In such a dehydration distillation operation of a dimethylamide compound, a by-product of dimethylamine due to a hydrolysis reaction is known. In order to suppress this, it is preferable to lower the operating temperature in the dehydration distillation step as much as possible. Specifically, it can be carried out at 150 ° C. or lower, or more preferably at 100 ° C. or lower, by a vacuum distillation method.
[0038]
Yet another embodiment of the present invention is a method in which a hydrolysis step is further provided prior to the dehydration distillation step. This method is a more preferred embodiment when the raw material mixture contains acetic anhydride. In this case, the components distilled off from the top of the dimethylamide compound purification distillation column can be recycled as a supply liquid to the hydrolysis reactor used in the hydrolysis step. The dimethylamide compound distilled off from the top of the “purification distillation column” and recycled may contain not only water but also dimethylamine having a low boiling point among hydrolysis by-products. This dimethylamine can be rapidly reacted with acetic anhydride and converted to dimethylacetamide. The main purpose of the hydrolysis step is to cause a hydrolysis reaction of acetic anhydride. If the temperature inside the hydrolysis reactor used for the hydrolysis step is too low, the reaction proceeds slowly. On the other hand, if the temperature is too high, hydrolysis of the dimethylamide compound becomes remarkable in addition to the intended reaction. Therefore, it is preferable to operate at a temperature of 50C to 100C. Since the target reaction proceeds in about 10 minutes to 2 hours, it is preferable to use either a batch reactor or a continuous flow reactor. When a continuous flow reactor is used for the operation, it can be realized by maintaining the temperature in the tubular reactor for a predetermined residence time. The internal pressure of the tubular reactor is preferably set higher than the storage state of the raw material liquid. With such a setting, it is possible to prevent a gas component such as air dissolved in the raw material liquid during storage from evaporating and evaporating in the heated reactor to form a bubble flow.
[0039]
The amount of water supplied to the hydrolysis reactor is set to be sufficiently larger than the amount required for reacting acetic anhydride contained in the raw material liquid, but is adjusted to be 1% by weight to 30% by weight based on the total amount of the raw material liquid. Preferably, the content can be set to 10% by weight to 30% by weight. If the amount of water is small, the progress of the reaction is slow. If the amount of water is too large, dehydration distillation becomes large-scale and a large amount of heat energy is required for distillation. Even if, for example, about 5% by weight of acetic anhydride is contained in the raw material liquid by the treatment in the hydrolysis reactor, most of the acetic anhydride is converted to acetic acid to reduce the acetic anhydride content to about 10 ppm to 1000 ppm. it can.
[0040]
In addition, the water distilled from the top of the dehydration distillation tower may contain a small amount of a dimethylamide compound or a carboxylic acid in addition to dimethylamine, which is a component having a low boiling point. When not recirculating as described above, it is desired to perform detoxification treatment as wastewater from the distillation process. Therefore, in the present invention, the water supplied to the hydrolysis reactor may be contained in the raw material liquid or may be additionally added. In one preferred embodiment, the water distilled from the top of the dehydration distillation column is recycled as feed water to the hydrolysis reactor. In the method of recirculating water, the amount of process effluent water is reduced, so that the burden of wastewater detoxification treatment is reduced.
[0041]
The water distilled from the top of the dehydration distillation column contains dimethylamine generated by hydrolysis of the dimethylamide compound. However, this dimethylamine quickly reacts with acetic anhydride in a hydrolysis reactor and is converted into dimethylacetamide.
[0042]
In the present invention, as an embodiment that can be additionally selected, in addition to the above-mentioned dimethylamide compound purification distillation column (first column), a second and a third distillation column can be used. it can. For example, when a two-column distillation column is used, an azeotropic mixture composition of a dimethylamide compound and a carboxylic acid and quinolines are taken out from the bottom of the first distillation column, and introduced into the second distillation column to have a high boiling point. The quinolines can be concentrated and taken out from the bottom of the second column, and can be circulated to the first distillation column. When a three-column distillation column is used, an azeotropic mixture of a dimethylamide compound and a carboxylic acid and quinolines are taken out from the bottom of the first distillation column and introduced into the second distillation column. The quinolines having a boiling point can be concentrated and taken out from the bottom of the second column, and can be circulated to the first distillation column. Further, a mixed solution of a dimethylamide compound and a carboxylic acid can be distilled from the top of the second distillation column and supplied to the third distillation column. A liquid containing carboxylic acid as a main component is distilled off from the top of the third distillation column, and the remaining liquid of dimethylamide is taken out from the bottom of the third column and circulated and supplied to the first column.
[0043]
Here, when this distillation operation is continued for a long time, there is a problem that impurities are generated due to a small amount of side reaction or impurities having a boiling point higher than the boiling point of quinolines contained in the raw material liquid. If the quinoline concentrate is dispensed, a small amount of high-boiling impurities contained therein are also extracted at the same time. Therefore, the larger the amount of dispensed, the more the amount of small high-boiling impurities accumulated inside the distillation column system can be reduced. . However, if the amount of the concentrated quinoline solution to be dispensed is too large, the additional step of removing high-boiling impurities from the concentrated quinoline solution is increased.
[0044]
Therefore, in one additional embodiment of the present invention, less than half, preferably 1% by weight, of the quinoline concentrate concentrated from the bottom of the second column and supplied to the first distillation column by circulation. -30% by weight is extracted. The quinoline-concentrated liquid thus taken out is subsequently distilled and purified separately in a quinoline-recovery tower to remove impurities having a high boiling point, and then the purified quinolines can be taken out. Alternatively, the quinoline concentrate can be supplied to the first distillation column again and used. From the top of the second distillation column, the remaining liquid mixture of the dimethylamide compound and the carboxylic acid from which the quinolines have been separated and removed is distilled off. By supplying this to the third distillation column, the highest azeotropic composition liquid in the absence of quinolines is separated at the bottom of the column, and excess acetic acid can be concentrated and distilled at the top of the third column. it can. The azeotropic composition at the bottom of the third column is a liquid having a higher dimethylamide compound concentration than in the presence of quinolines, and this can be circulated and supplied again to the first column to remove the dimethylamide compound.
[0045]
Another embodiment of the present invention is characterized in that less than half of the liquid withdrawn from the bottom of the third column and fed back to the first column, preferably 1% to 30% by weight, is removed from the bottom of the third column. It is possible to select a method of branching out the middle of the pipe and discharging the pipe. By-products resulting from hydrolysis of the dimethylamide compound are concentrated in the effluent component, and can be efficiently removed. A by-product of distilling dimethylformamide is formic acid. In addition, dimethylacetamide, which is generated by the reaction of dimethylamine, which is another hydrolysis by-product, with acetic anhydride, is concentrated in this outflow component and can be efficiently removed.
[0046]
As one embodiment of the apparatus of the present invention for separating a dimethylamide compound and a carboxylic acid by distillation, the apparatus can realize the above-mentioned distillation separation method and is constituted by three distillation columns.
[0047]
An embodiment of the apparatus of the present invention using three distillation columns will be described with reference to FIG. FIG. 1 is a conceptual diagram of an apparatus 10 including three distillation columns, a first column, a second column, and a third column. The three distillation columns, that is, the first column 12, the second column 14, and the third column 16 are connected by pipes, respectively.
[0048]
The first tower 12 includes a raw material mixture supply pipe 18 and a tower top distillation pipe 20. One major feature of the present invention is that a pipe for taking out a purified dimethylamide compound liquid is provided at an intermediate height of the tower. This pipe is referred to as “middle part discharge pipe”. The first tower middle portion discharge pipe 22 has a structure in which a part of the distillation flow-down liquid at the intermediate height position of the column is withdrawn, and the remaining flow-down liquid flows down further. The steam rising in the first tower 12 flows upward without being extracted.
[0049]
The first tower bottom bottom discharge pipe 24 is connected to a second tower supply pipe 26 connected to the second tower 14, and supplies the liquid discharged from the bottom of the first tower 12 to the second tower 14.
[0050]
The second distillation column has a bottom bottom discharge pipe 28, which is connected to a circulating supply pipe 30 that supplies quinolines to the first column again.
[0051]
In this apparatus, a pipe connected to a first tower supply is branched from a bottom of a second tower, and a supply amount to the first tower is adjusted by flowing a part of a fluid by adjusting a flow rate in the pipe. It can also be configured. Specifically, a branch pipe can be provided in the middle of the bottom bottom discharge pipe 28 to allow a part of the fluid to flow out to a treatment step for removing high-boiling impurities. The top distillate pipe 32 of the second tower 14 is connected to a third tower feed pipe 34 to supply the third tower 16 with the distillate of the second tower top.
[0052]
The third tower 16 is provided with a top distilling pipe 36 and a bottom bottom discharging pipe 38. The third bottom liquid can be supplied to the first column 12 by connecting the third column bottom discharge pipe 38 to the circulation supply pipe 30. Note that the circulation supply pipes may be provided separately and independently, or may be in a mode of merging in the middle as shown in FIG.
[0053]
Further, as a feature of the present invention, a pipe connected from the bottom tower of the third tower to the feed of the first tower may be branched on the way, and may be configured to adjust a flow rate to discharge a part of the fluid. Specifically, a branch pipe 39 is provided.
[0054]
One embodiment of the apparatus for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention can realize the above-mentioned distilling and separating method, and comprises two distillation columns.
[0055]
An embodiment of the apparatus of the present invention using two distillation columns will be described with reference to FIG. FIG. 2 is a conceptual diagram of an apparatus 50 including two distillation columns, a first column and a second column. The distillation column, the first column 52, and the second column 54 are connected by pipes, respectively.
[0056]
The first column 52 includes a raw material mixture supply pipe 56 for supplying a raw material liquid containing a dimethylamide compound and a carboxylic acid and quinolines. An azeotropic composition of a dimethylamide compound and a carboxylic acid and quinolines are taken out from the bottom bottom outlet tube 58 of the first column 52. Basically, 1% to 50% by weight of the excess amount of the dimethylamide compound in excess of the azeotropic composition mixture ratio is discharged from the top of the first column, and the remaining liquid is removed from the first column. From there, it is withdrawn as a purified dimethylamide compound by the middle part discharge pipe 60. The liquid withdrawn from the bottom of the first column is introduced into the second column 54 from the bottom bottom discharge pipe 58 through the second column supply pipe 62. In the second column 54, a column top distilling pipe 61 is provided at the column top, and a column bottom discharge pipe 64 is provided at the column bottom. Then, the high-boiling quinolines are concentrated in the second column 54 and are discharged from the bottom bottom discharge pipe 64 of the second column 54. A discharge pipe 65 may be provided at an intermediate height position of the second tower, and may be connected to a circulation supply pipe 66 that circulates and supplies the first tower. The second column bottom discharge pipe 64 is connected to the circulation supply pipe 66, and the second column bottom liquid can be supplied to the first column 52. The circulation supply pipes may be provided separately and independently.
[0057]
As an additional embodiment of the apparatus of the present invention, the above two or three distillation towers are combined with one or more apparatuses of a hydrolysis reactor, a dehydration distillation tower, or a quinoline recovery distillation tower. is there. Basically, the object of the present invention can be realized by two or three distillation towers, but the above-mentioned additional embodiment can be preferably used from the viewpoint of removing mixed water and acetic anhydride. As a combination, any one of the above, or two devices of a hydrolysis reactor and a dehydration distillation column, or two devices of a hydrolysis reactor and a quinoline recovery distillation column, or a dehydration distillation column and a quinoline Two devices of the recovery distillation column, and further, three devices of the above three hydrolysis reactors, a dehydration distillation column, and a quinoline recovery distillation column can be added.
[0058]
One example 70 of an apparatus according to an additional aspect of the present invention is described with reference to FIG. FIG. 3 shows a structure in which a hydrolysis reactor 76, a dehydration distillation column 78, or a quinoline recovery distillation column 80 is added to two distillation columns of a first column 72 and a second column 74.
[0059]
The first column 72 includes a raw material mixture supply pipe 82, a first column top distilling pipe 84, and a first column middle extraction pipe 86. The first column bottom bottom discharge pipe 88 is connected to the second column 74 and the second column supply pipe 90, and the first column bottom liquid is supplied to the second column 74. The second column 74 includes a second column top distilling pipe 92 and a second column bottom bottom discharging pipe 94. The second tower bottom bottom discharge pipe 94 is connected to the circulation supply pipe 96 of the first tower 72. The second tower 74 has a discharge pipe 98 from the middle part of the tower. The second discharge pipe 98 is connected to a circulation supply pipe 96 to the first tower 72. Here, as a feature of the present invention, a pipe connected from the second tower intermediate portion discharge pipe 98 to the circulation supply pipe 96 is branched. Specifically, a branch pipe 100 may be provided. Thus, the supply amount to the first tower can be adjusted by discharging a part of the fluid in the pipe by adjusting the flow rate. In addition, the circulation supply pipes may be provided separately and independently, or may be in a mode of merging in the middle.
[0060]
In the apparatus shown in FIG. 3, the hydrolysis reactor 76 is connected to a dehydration distillation tower 78, and the dehydration distillation tower 78 is connected to the first tower 72. The hydrolysis reactor 76 is preferably installed when acetic anhydride is mixed in the raw material mixture. The raw material mixture is first supplied to the hydrolysis reactor 76 through the raw material supply pipe 102.
[0061]
The raw material mixture that has undergone the reaction in the hydrolysis reactor 76 is supplied to the dehydration distillation tower 78 through the dehydration distillation tower supply pipe 104. The dehydration distillation tower 78 plays a role in removing much of the water mixed in the raw material mixture. The liquid discharged from the bottom of the dehydration distillation tower 78 is supplied from the bottom liquid outlet pipe 106 to the “first tower” 72 via the supply pipe 82 of the first tower.
[0062]
Here, the components distilled out from the top of the first column 72, which is a dimethylamide compound purification distillation column, and the components distilled out from the top of the dehydration distillation column 78 used in the dehydration distillation step, are the first column top. The liquid can be circulated again from the distilling pipe 84 and the top distilling pipe 108 of the dehydration distillation tower 78 as a supply liquid to the hydrolysis reaction tower 76 by the circulation supply pipe 110.
[0063]
If the amount of water is insufficient just by circulating the distillate from the top of the dehydration distillation tower, water is added from outside to the raw material liquid supply pipe 102 so that the content of water is 1 to the raw material liquid. It is preferable to adjust the amount to be from 50% by weight to 50% by weight. If water is contained in the raw material feed liquid in advance and the amount of water becomes excessive when all the distillate at the top of the dehydration distillation tower is circulated, a part of the distillate from the top of the dehydration distillation tower is processed. Waste water can be discarded and only the required amount can be circulated.
[0064]
A quinoline recovery column 80 is added to the distillation column. The purpose of the quinoline recovery column is to remove impurities accumulated in the distillation operation. In FIG. 3, the bottom liquid is taken out from the bottom tower 94 at the bottom of the second column, and less than half of the quinoline concentrate concentrated and supplied to the first column 72 is circulated. 80 is introduced through a supply pipe 112 and purified by distillation. Purified quinolines after removing high boiling impurities can be obtained. Further, it can be supplied again to the first column.
[0065]
The components after the quinolines have been removed in the second column 74 have an excess of carboxylic acid as compared with the azeotropic composition. The excess carboxylic acid is discharged from the top of the distillation column, and the remaining liquid is discharged from the intermediate height of the column as an azeotropic mixture composition through the middle discharge pipe 98 and supplied to the first column through the circulation supply pipe 96. Is done. Here, it is possible to select a method in which less than half of the liquid that is discharged from the intermediate height of the second column and circulated to the first column supply is discharged through the branch pipe 100. In addition, the circulation supply pipes may be provided separately and independently, or may be in a mode of merging in the middle.
[0066]
An example in which an apparatus is additionally installed in two distillation towers has been described with reference to FIG. 3. In the present invention, the hydrolysis reactor, the dehydration distillation tower, and the quinoline recovery distillation tower are one distillation tower. Can be added even with three towers. Further, any one or two of a hydrolysis reactor, a dehydration distillation column, and a quinoline recovery distillation column may be added. In this case, it is preferable that the circulating supply pipe be connected to the pipe for supplying the raw material mixture first in the embodiment of the present invention. In addition, the circulation supply pipe may be a plurality of separate and independent pipes, or may be a mode in which the circulation supply pipe joins in the middle as shown by 110 in FIG. Further, in an apparatus composed of three columns, it is preferable to branch the bottom bottom outlet of the second column and connect the piping to a quinoline recovery distillation column.
[0067]
The distillation tower is provided with a condenser at the top and a reboiler at the bottom in order to exhibit its function.
[0068]
Although not particularly described in the drawing, the vapor at the top of each distillation column is condensed and liquefied by a condenser, one part of which is taken out as a top distillate, and the remaining liquid is refluxed to the top. . Further, the bottom liquid of the distillation column is heated and evaporated by the reboiler to generate ascending vapor in the distillation column.
[0069]
The method and apparatus for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention have been described above. However, the present invention can be applied to, for example, synthesis of a polyimide resin. In the synthesis of a polyimide resin, dimethylformamide, which is a solvent discharged from the molding step, contains acetic acid and acetic anhydride, and the present invention can be applied to the purification of these solvents by distillation. When this solvent is discharged in the form of an evaporative gas from the molding step or the drying step, it can be collected by liquefaction by cooling using a condenser, scrubber, or the like, and then subjected to distillation in the method of the present invention. When acetic anhydride is contained in the collected solvent, water can be added to hydrolyze acetic anhydride to convert it into acetic acid, and then can be subjected to the distillation of the method of the present invention. In addition, when water is added in advance in the step of collecting added water or the solvent, dehydration distillation for the purpose of dehydration treatment can be performed prior to the distillation in the method of the present invention. Thus, the dimethylformamide separated and purified recovered from the intermediate height position of the distillation column by applying the present invention can be reused as a solvent. Since it has a high degree of purification, it can be used for, for example, polymerization of polyimide resin or film formation.
[0070]
Although the present invention has been described above, the present invention is not limited to only these embodiments, and various improvements, changes, and modifications may be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Can be implemented.
[0071]
【Example】
Next, an embodiment of a method and an apparatus for separating a dimethylamide compound and a carboxylic acid by distillation according to the present invention will be described in detail with reference to the following examples.
[0072]
In Examples, "%" indicates% by weight. “G / h” indicates a flow rate per unit time. DMF refers to dimethylformamide. DMA refers to dimethylamine.
[0073]
Example 1 and Comparative Example 1 are apparatuses using two distillation towers.
[0074]
(Example 1)
As the distillation column, two stainless steel cylinders (outer diameter: 60 mm, inner diameter: 55 mm, total length: about 2500 cm), and two stainless steel Dixon packings (6 mmφ) filled therein as a filler were used (first column). , The second tower). A filler was filled 150 mm from the lower portion of the stainless steel cylinder of the first tower, and a space 250 mm was provided thereon, and a nozzle for the circulating supply liquid from the second tower was inserted. A filler material of 150 mm was filled thereon, and a raw material liquid supply nozzle was inserted into the space 250 mm above the space. The upper part was filled with a filler of 300 mm, and a liquid extraction part at the height of the middle of the tower was attached to a part of the upper space of 450 mm. Subsequently, a 450 mm filler was placed thereon, and a reflux liquid supply nozzle was inserted into the space above the filler. In the second column, a filler was placed 300 mm from the bottom of the stainless steel cylinder, a space 300 mm was provided thereon, and a supply nozzle for introducing the liquid discharged from the bottom of the first column was inserted. A filler of 150 mm was filled thereon, and a liquid extraction part at a height of the middle of the tower was attached to a portion of the upper space of 450 mm. Subsequently, a 450 mm filler was placed above, and a reflux liquid supply nozzle was inserted into the space above the filler. A condenser is installed at the top of the first and second towers, and a reboiler is installed at the bottom.
[0075]
The following outline device was manufactured. That is, the first distillation column supplies the raw material liquid and takes out the purified dimethylformamide liquid. The second distillation column takes out the carboxylic acid component (acetic acid) from the top of the column.
A condenser is connected to the top of the first distillation column and the second distillation column. The condenser liquefies the vapor, removes a portion of the vapor as a top distillate, and connects the remaining liquid to the top to reflux.
A liquid extraction section (side cut section) was provided below the column of the first distillation column at a height of 30 cm from the top of the column with a filler height of 30 cm. The piping from the side cut liquid was a pipe for taking out part of the side cut liquid and returning the remaining liquid to the upper portion of the filler below the liquid.
A raw material supply pipe was provided at a lower position with a filler height of 30 cm further from the side cut portion.
A pipe for supplying a liquid recirculated from the second distillation column was provided at a position below the raw material supply pipe at a filler height of 15 cm further.
Further, a liquid sump at the bottom of the column was provided below with a filler height of 15 cm. A reboiler was provided at the bottom of the tower, and the bottom liquid was heated and evaporated, and a pipe for extracting a certain amount of the bottom liquid and supplying it to the second column was provided.
[0076]
A side cut liquid discharge pipe was provided 45 cm below the top of the second distillation column. A part of the side cut liquid was withdrawn from the second distillation column, and a pipe was formed to reflux the remaining liquid to the upper portion of the filler below the side cut liquid.
A supply section for the liquid withdrawn at the bottom of the first tower was provided further 15 cm below the side cut position. A liquid pool at the bottom of the tower was provided further 30 cm below the side cut portion. A reboiler was provided at the bottom of the second distillation column.
The bottom liquid was heated and evaporated by a reboiler to raise the vapor inside the tower, and a pipe was formed to extract a certain amount of the bottom liquid. The side cut liquid from the second distillation column and the liquid withdrawn from the bottom of the second column were recycled to the first column.
[0077]
The bottom liquid of the first column was heated to 100 ° C. by a reboiler and evacuated using a vacuum pump to adjust the pressure conditions in the column internal space. The operating pressure was 6.0 kPa-abs. And The liquid feed to the first column was a mixed solution of dimethylformamide: 79.5% by weight, acetic acid: 14.8% by weight, and isoquinoline: 5.1% by weight. 0.0030% by weight. The feed rate is about 98 g / h.
[0078]
It was taken out from the top of the first distillation column under a distillation condition of a flow rate of 8.5 g / h. In this solution, in addition to dimethylformamide, water content of 7000 ppm and dimethylamine of 6000 ppm were detected as impurities.
[0079]
Further, it was taken out from the side cut of the first distillation tower under the distillation conditions of a flow rate of 65 g / h.
The component ratio of the side cut solution was dimethylformamide as a main component, the water content was 20 ppm, and the dimethylamine was 25 ppm. The removal rate of dimethylformamide from the side cut is 88.5%.
The composition of the mixed solution extracted from the bottom of the first distillation column at a flow rate of 291 g / h contained 60% of isoquinoline, 12% of dimethylformamide, and 12% of acetic acid.
The liquid recirculated from the second column and introduced into the first column had a flow rate of 267 g / h.
[0080]
The bottom liquid of the second column was heated to 150 ° C. by a reboiler and evacuated using a vacuum pump to adjust the pressure condition of the column internal space, and the operating pressure was 7.3 kPa-abs. And
A flow rate of 70 g / h was discharged from the side cut of the second column, of which 7 g / h was purged, and the remainder was recycled to the first column. The purged side cut contained 45% dimethylformamide and 35% acetic acid.
A liquid containing isoquinoline as a main component was extracted from the bottom of the second column at a flow rate of 204 g / h, and recirculated to the first column together with the side cut liquid.
The distillate distilled off from the top of the second distillation column at a flow rate of 12 g / h was dimethylformamide 25% and acetic acid 75%.
[0081]
(Comparative Example 1)
Operating temperature and pressure were similarly operated using the same raw material composition in the same apparatus as in Example 1 except that no side cut was performed in the first tower.
When a flow rate of 73.5 g / h was discharged from the top of the first tower, 853 ppm of water and 715 ppm of dimethylamine were contained as impurities in dimethylformamide. Except not performing the side cut of the 1st tower, it carried out similarly to Example 1 about extraction of the 1st tower bottom part, the supply of the raw material to the 1st tower, the recycle liquid from the 2nd, and the operating conditions of the 2nd tower.
[0082]
(Comparison between Example 1 and Comparative Example 1)
The dimethylformamide obtained in Comparative Example 1 contains 853 ppm of water and 715 ppm of dimethylamine, whereas the dimethylformamide obtained in Example 1 according to the method of the present invention has 20 ppm of water and 25 ppm of dimethylamine. Yes, the impurity content was significantly reduced as compared with the comparative example.
[0083]

[0084]
Hereinafter, Example 2 and Comparative Example 2 are apparatuses using one distillation tower.
[0085]
(Example 2)
As a distillation column, one stainless steel cylinder (outer diameter: 60 mm, inner diameter: 55 mm, total length: about 2500 cm) filled with stainless steel Dickson packing (6 mmφ) as a filler was used. The structure of the distillation column was the same as that of the first column in Example 1. A condenser is installed at the top of the column to distill condensate and reflux to the top of the column. There is a reboiler at the bottom of the tower to drain the liquid. From the height position in the middle of the tower, the raw material liquid is supplied and the side cut liquid is withdrawn. A side-cut liquid withdrawal position is provided at a position about 30 cm away from the top of the tower, and the raw material mixture is supplied at a position about 30 cm below the side-cut position.
[0086]
The raw material mixture was supplied to the distillation column at a flow rate of 368 g / h. The composition of the raw material mixture is DMF: 33.7%, acetic acid: 11.3%, isoquinoline: 54.1%, and water: 0.0047%. With the reflux ratio at the top of the tower being about 20, a reflux liquid at a flow rate of about 150 g / h was allowed to flow down. Assuming that the flow rate of the distillate from the top of the distillation column was 7.4 g / h, the component was generally DMF, containing about 0.5% of water and about 0.1% of DMA.
[0087]
In the side cut section, the entire reflux liquid (about 150 g / h) at the top of the tower is blocked and circulated through a conduit to a 50 ml receiving tank provided near the side, and a part (74 g / h) of the liquid is side cut. And extracted as purified DMF. The remaining liquid was returned to the tower and dropped. The water content in the purified DMF was 0.007%, the dimethylamine content was about 0.002%, and the acetic acid content was 0.003%. The removal rate of dimethylformamide from the side cut is 98.9%.
[0088]
A liquid reservoir at the bottom of the column is further provided below the column with a filling section of about 30 cm. The reservoir is heated and evaporated as a reboiler, and a certain amount of the bottom liquid is withdrawn (a flow rate of 271 g / h). The composition of the liquid withdrawn from the bottom of the column was DMF: 16%, acetic acid 15%, isoquinoline: 68%, and the like.
[0089]
The bottom liquid of the distillation column was heated to 100 ° C. with a reboiler and evacuated using a vacuum pump to adjust the pressure conditions in the column internal space. The operating pressure was 6.0 kPa-abs. And
[0090]
(Comparative Example 2)
The distillation column used in the experiment was made of glass and was a cylinder having an inner diameter of 30 mmφ and a total length of about 1500 mm, in which a filler (glass Raschig ring 3 mmφ) was put. The total height from the bottom reboiler to the top condenser is about 2500 mm. The flow rate of the raw material liquid from the middle position of the column is 122 g / h, and the composition is DMF 29%, acetic acid 11%, isoquinoline 59% and water about 0.005%.
[0091]
The DMF was taken out at a top distillate of 22 g / h without extracting the side cut liquid. The water content was about 0.08%, dimethylamine was about 0.01%, and acetic anhydride was 0.0005%. Was detected. The reflux ratio at the top of the column was 1.
[0092]
The flow rate at the bottom of the column was 100 g / h, and the composition was DMF 15%, acetic acid: 13%, isoquinoline: about 72%, and acetic anhydride: 0.0025. It was also detected that about 0.005% of isoquinoline was converted to methyl isoquinoline. The operating pressure of the distillation column was 6.7 kPa-abs. And The temperature was about 100 ° C.
[0093]
(Comparison between Example 2 and Comparative Example 2)
The dimethylformamide obtained in Comparative Example 2 contains 0.08% of water and 0.01% of dimethylamine, whereas the water in dimethylformamide obtained in Example 2 according to the method of the present invention has a water content of 0%. 0.0007% and dimethylamine were 0.002%, indicating that the impurity content was significantly reduced as compared with Comparative Example 2.
[0094]

[0095]
Example 3 and Comparative Example 3 are apparatuses using four distillation towers.
[0096]
(Example 3)
As a distillation column, four stainless steel cylinders (outer diameter: 60 mm, inner diameter: 55 mm) filled with stainless steel Dickson packing (6 mmφ) as a filler were used. The dehydration distillation tower (length: about 2000 mm), the DMF purification distillation tower (length: about 2500 mm), the acetic acid removal distillation tower (length: about 2500 mm), and the isoquinoline recovery distillation tower (length: about 1000 mm) were used. The DMF purification distillation column and the acetic acid removal distillation column had the same configuration as the first column and the second column in Example 1. In the dehydration distillation column, a reboiler is connected to the bottom of the column, the space is filled with a filler of 25 cm from the bottom, a space of 15 cm is provided, the space is further filled with a space of 20 cm, and a raw material liquid supply section is provided in a space of 15 cm above the space. A filler of 45 cm was provided thereon, and the upper portion was used as a tower top. The structure of the isoquinoline recovery distillation column is such that a filler is provided at 30 cm above the column connected to the reboiler in order from the bottom, and the raw material liquid is supplied at a height of 15 cm between them. Above that was the tower top.
The hydrolysis reactor, the dehydration distillation unit, the DMF purification distillation unit, and the acetic acid removal distillation column are connected by pipes in this order. A stainless steel tube (inner diameter 4 mmφ, length 10 m) was used as a hydrolysis reactor.
A condenser is connected to the top of the DMF purification distillation column, acetic acid removal distillation column, and isoquinoline recovery distillation column. The condenser liquefied the vapor, took out a part thereof as a top distillate, and connected the remaining liquid to the top so as to be refluxed.
[0097]
The composition of the raw material liquid is DMF: 70%, acetic acid: 11%, acetic anhydride: 12%, isoquinoline: 2.5%, water: about 3.5%, which is sent by a metering pump at a flow rate of 42 g / h. The solution was passed through the hydrolysis reactor. The reactor temperature was maintained at 80 ° C., and a pressure control valve was attached to the outlet to adjust the pressure in the reactor to 0.2 MPa. At the reactor outlet, acetic anhydride was converted to acetic acid with a conversion of 99% or more. The liquid exiting the reactor was subsequently supplied to a dehydration distillation column, where water was separated and distilled off from the top of the column, and the distilled water was circulated back to the inlet of the hydrolysis reactor. The reflux ratio at the top of the dehydration tower was about 0.5. The operating pressure of the dehydration distillation column is 12.0 kPa-abs. And
[0098]
Distilled water at the top of the dehydration distillation column contained dimethylamine produced and was converted to dimethylacetamide at the outlet of the hydrolysis reactor. By circulating a liquid containing water as a main component distilled from the top of the dehydration distillation column at a flow rate of about 10 g / h to the inlet of the hydrolysis reactor, the water concentration in the hydrolysis reactor is increased to 20% by weight. I made it. A liquid from which water was removed was withdrawn from the bottom of the dehydration distillation column, and the filler was supplied at a flow rate of about 50 g / h to a height of 300 mm from the bottom of the dimethylformamide purification distillation column.
[0099]
The top liquid of the dimethylformamide purification distillation column is condensed and liquefied by a condenser, a part of which is converted into a top distillate, and the remainder is refluxed to the top of the distillation column. The reflux ratio was about 11, and the operating pressure was 6.0 kPa-abs. And A liquid having a flow rate of 8.5 g / h was distilled off from the top of the purification distillation column, and this was also circulated and supplied to the inlet of the hydrolysis reactor.
[0100]
The purification tower top distillate DMF contained about 0.35% water and about 0.1% dimethylamine. When purified DMF was side-cut at a flow rate of 26 g / h at a position about 30 cm below the top of the tower, water was 0.008% and DMA was 0.002% as impurities in the DMF. The removal rate of dimethylformamide from the side cut is 75.4%.
[0101]
The liquid composition at the bottom of the purification distillation column is composed mainly of DMF: 23%, acetic acid: 15%, isoquinoline: 43%, etc., and is withdrawn at about 300 g / h. Was supplied to positions separated by 300 mm. The top reflux ratio of the acetic acid removal distillation column was 15, and the pressure was 7.3 kPa-abs. Operated by
[0102]
The distillate flow rate of the "acetic acid removal distillation column" at a flow rate of about 10 g / h was about 90% acetic acid and about 10% DMF. The liquid at a position about 30 cm below the top of the column was withdrawn by side cutting at a flow rate of about 70 g / h, 3 g / h of the liquid was purged, and the rest was separated from the bottom of the dimethylformamide purification distillation column by a height of 150 mm from the bottom of the distillation column. It was supplied to the position.
[0103]
The composition of the side cut solution was DMF: 59%, acetic acid: 37%, dimethylacetamide: 4%, and the like. The high-boiling point component is concentrated at the bottom of the “acetic acid removal distillation column” and contains about 80% of isoquinoline, and the remaining components are contained in the raw material liquid. Met. The bottom liquid was withdrawn, and the packing material was fed upward from the bottom of the isoquinoline purification distillation column to a height of 150 mm at a rate of about 200 g / h.
[0104]
Isoquinoline and other high-boiling materials at the bottom of the acetic acid removal distillation column come from the feed liquor little by little and build up gradually. For this reason, an operation of extracting the liquid of the increased amount and recovering and distilling isoquinoline was performed. Since the test scale was small, the processing liquid was stored and then supplied to the isoquinoline recovery distillation column at a flow rate of about 50 g / h. Assuming that the top reflux ratio of the isoquinoline recovery tower is 10, the pressure is 5.3 kPa-abs. By operating at a pressure of about 36 g / h, purified isoquinoline having a purity of 95% or more was obtained. The bottom liquid was concentrated and discharged to a residual isoquinoline concentration of about 20%.
[0105]
Observations were made to investigate the state of water generation.
[0106]
(Reference Example 1)
Dimethylformamide, acetic acid and isoquinoline were charged into a 100 cc glass container at a mixing ratio of 25%, 10% and 65% by weight, respectively, and maintained at 120 ° C., and the concentration of acetic anhydride with time was analyzed and measured. Although acetic anhydride was not detected at the beginning of the charging, 0.014% of acetic anhydride was detected from the liquid in the glass container after 1 hour, and 0.029% of acetic anhydride was detected after 2 hours.
[0107]
According to the results of Reference Example 1, acetic anhydride was generated in a mixed solution of dimethylformamide, acetic acid, and isoquinoline. Estimated from this, one of the causes of the generation of water in the distillation column in Examples 1, 2, 3 and Comparative Examples 1, 2 is as follows:
Acetic acid → acetic anhydride + water
It is possible that the reaction has occurred.
[0108]
However, the amount of acetic anhydride was extremely small compared to the amount of water detected in Comparative Example 2, and it is considered that there are other causes. The other cause is considered to be related to the occurrence of methyl isoquinoline observed in Comparative Example 2. Possible responses include:
Isoquinoline + acetic acid → methyl isoquinoline + formic acid
Formic acid → water + carbon monoxide
It is. It is considered that water is generated by the above reaction.
[0109]
【The invention's effect】
As described above, according to the method for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention, a high-purity purified dimethyl compound that improves the distillation method using a quinoline compound as an entrainer and overcomes contamination with impurities. An amide compound can be obtained. Further, in the apparatus to which the method of the present invention is applied, in a dimethylamide compound purification distillation column, by removing the purified dimethylamide compound from the column intermediate height, water generated in the distillation column as trace impurities is distilled off at the top. And a highly pure dimethylamide compound with few impurities can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an apparatus constituted by three distillation columns for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention.
FIG. 2 is a conceptual diagram of an apparatus composed of two distillation columns for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention.
FIG. 3 is a conceptual diagram of an apparatus for distilling and separating a dimethylamide compound and a carboxylic acid of the present invention, which is composed of two distillation columns and an additional device.
[Explanation of symbols]
10: An example of an apparatus for distilling and separating a dimethylamide compound and a carboxylic acid of the present invention
12; 1st tower
14; second tower
16; Third tower
18; Raw material liquid supply pipe of the first column
20; Top distillate pipe
22: Discharge pipe in the middle part of the first tower
24: Outer pipe of the bottom of the first tower
26; second tower supply pipe
28; Outer pipe of bottom of second tower
30; circulation supply pipe
32: Distillation pipe at the top of the second tower
34; third tower supply pipe
36; Distillation pipe at the top of the third tower
38; Outer can of bottom of third tower
39; branch pipe
50; Another example of the apparatus for distilling and separating the dimethylamide compound and carboxylic acid of the present invention
52; 1st tower
54; 2nd tower
56; material mixture supply pipe
58; Outer pipe of bottom of first tower
60; Discharge pipe in the middle part of the first tower
62; second tower supply pipe
64; second tower bottom bottom outlet
65; Discharge pipe in middle part of second tower
66; circulation supply pipe
70: Still another example of the apparatus for distilling and separating a dimethylamide compound and a carboxylic acid of the present invention
72; 1st tower
74; second tower
76; hydrolysis reactor
78; dehydration still
80; Quinoline recovery distillation column
82; raw material liquid supply pipe
84; Top distillate pipe
86: Discharge pipe in the middle part of the first tower
88; Outer pipe of the bottom of the first tower
90; second tower supply pipe
92; Distillation pipe at the top of the second tower
94; second tower bottom bottom outlet
96; circulation supply pipe
98: Discharge pipe in the middle part of the second tower
100; branch pipe
102; Raw material liquid supply pipe
104; distillation column supply pipe
106; Distillation tower bottom bottom outlet
108; Dehydration distillation tower bottom can outlet
110; circulation supply pipe
112; Quinoline supply pipe

Claims (16)

A method comprising adding a quinoline to a raw material mixture containing a dimethylamide compound and a carboxylic acid and distilling the mixture with a distillation column to separate and purify the dimethylamide compound. An amide compound is distilled off from the top of the distillation column, and the remainder is withdrawn from the "intermediate height position" of the distillation column as a further purified dimethyl amide compound. . The dimethylamide compound expressed by the formula _{(CH 3)} 2 NCOR, R _is H, CH 3, is selected from the group consisting of CHCH _2, distillation separation method of claim 1. The carboxylic acid composition _formula: C _n is represented by _H 2n + 1 COOH, n is selected from 0, 1, 2, claim 1 or claim 2 distillation separation method according. The distillation separation method according to claim 3, wherein in the raw material mixture, the carboxylic acid is acetic acid, and the dimethylamide compound is dimethylformamide. The distillation separation method according to any one of claims 1 to 4, wherein the quinolines are selected from the group consisting of quinoline, isoquinoline, and methylquinoline. The distillation separation method according to any one of claims 1 to 5, wherein the content of the dimethylamide compound in the raw material mixture is higher than that of the carboxylic acid. A dimethylamide compound and a carboxylic acid are separated by distillation using three distillation columns including a first distillation column, a second distillation column, and a third distillation column (hereinafter, referred to as a first column, a second column, and a third column). A way to
(1) a step of supplying a raw material mixed solution containing a dimethylamide compound and a carboxylic acid and a quinoline to the “first column”;
(2) removing the liquid from the bottom of the “first column” and supplying the bottom product from the bottom of the “first column” to the middle position of the “second column”;
(3) a step of removing quinolines from the bottom of the “second tower” and supplying the quinolines to the “first tower”, and circulating the quinolines;
(4) distilling a mixed solution of a dimethylamide compound and a carboxylic acid from the top of the “second column” and supplying the mixed solution to a middle position of the “third column”;
(5) Distilling a liquid containing a carboxylic acid as a main component from the top of the “third tower”, removing the remaining liquid of the dimethylamide compound from the bottom of the “third tower”, Supplying the bottom bottoms to the "first column";
(6) Distillation of 1 to 50% by weight of the total amount of the dimethylamide compound withdrawn from the top of the “first column”, and the remainder as a further purified dimethylamide compound in the “intermediate of the first column” The distillation separation method according to any one of claims 1 to 6, further comprising a step of withdrawing the liquid from the "height position". A method for separating and distilling a dimethylamide compound and a carboxylic acid using two distillation columns consisting of a “first tower” and a “second tower”,
(1) a step of supplying a raw material mixed solution of a dimethylamide compound and a carboxylic acid and quinolines to the “first column”;
(2) removing the liquid from the bottom of the “first column” and supplying the bottom liquid of the “first column” to the middle position of the “second column”;
(3) a step of taking out quinolines from the bottom of the “second column”, supplying the quinolines to the “first column”, and circulating and supplying the quinolines;
(4) a step of distilling a fraction containing carboxylic acid as a main component from the top of the “second column”;
(5) a step of discharging the remaining liquid mixture of the dimethylamide compound from the intermediate height position of the “second tower” and supplying the mixed liquid to the “first tower”;
(6) Distillation of 1% by weight or more and 50% by weight or less of the total amount of the dimethylamide compound withdrawn from the top of the "first column", and the remainder as a further purified dimethylamide compound having an intermediate height of the "first column" The distillation separation method according to any one of claims 1 to 6, further comprising a step of withdrawing the liquid from the position. The step of bottoming out quinolines from the bottom of the "second column" comprises the step of branching out and removing less than half of the bottoms in the bottom of the "second column"; and the step of distilling the liquid to obtain quinolines The distillation separation method according to claim 7 or 8, further comprising a step of separating and removing high boiling point impurities contained in the water. Further, a mixed solution of a dimethylamide compound, a carboxylic acid, and an acid anhydride thereof is first passed through a hydrolysis reactor to convert the acid anhydride into a carboxylic acid, and then passed through a dehydration distillation column to allow the “dehydration distillation column” to flow. Distilling water from the top of the tower, removing the dehydrated liquid from the bottom of the "dehydration distillation tower" and supplying it to the distillation tower as a raw material mixture, distilling from the top of the "first tower" The distillation separation method according to any one of claims 7 to 9, comprising a step of supplying the distilled distillate to the "dehydration distillation column". The distillation separation method according to claim 10, further comprising a step of supplying a liquid containing water distilled as a main component from the top of the "dehydration distillation column" to a hydrolysis reactor. Three distillation towers consisting of "first tower", "second tower" and "third tower";
A raw material supply pipe for supplying a raw material mixed solution of a dimethylamide compound and a carboxylic acid to the “first column”, and a quinoline;
A "first tower" column bottom discharge pipe provided at the bottom of the "first column" to discharge the "first column" bottom product;
In order to supply the bottom liquid of the "first column" to the "second column", the "first column" is connected to the bottom bottom discharge pipe and the "second column" is provided at the middle position of the "second column". Two towers "supply pipe,
A "second tower" tower bottom discharge pipe provided at the bottom of the "second tower" to discharge quinolines;
A quinoline circulation supply pipe for supplying the "second column" bottoms to the "first column";
A "second tower" overhead distilling pipe provided at the top of the "second tower" to distill a mixture of the dimethylamide compound and the carboxylic acid;
A "third column" supply pipe provided in the "third column" and supplying the "second column" distillate to the "third column";
A "third tower" overhead distilling pipe provided at the top of the "third tower" to take out a fraction containing carboxylic acid as a main component from the top of the "third tower";
A "third tower" bottom bottom outlet pipe, which is provided at the bottom of the "third tower", and discharges the "third tower" bottom discharged with the dimethylamide compound from the bottom of the "third tower"; ,
Supplying the “third column” bottoms to the “first column”;
It is a device that separates dimethylamide compound and carboxylic acid by distillation,
Further, of the total amount of the purified dimethylamide compound, 1% by weight or more and 50% by weight or less are distilled off from the top of the “first column”, and the remainder is further purified as a dimethylamide compound in the “first column”. A distillation separation device that can be taken out from an intermediate height position. Two distillation towers consisting of "first tower" and "second tower";
A "first column" raw material supply pipe for supplying a raw material mixed solution of a dimethylamide compound and a carboxylic acid and the quinoline to the "first column";
A “first column” bottom bottom discharge pipe for discharging bottom liquid from the “first column” column bottom;
A "second column" supply pipe for supplying the bottoms to the middle position of the "second column";
A “second tower” bottom bottom discharge pipe for discharging quinolines from the “second tower” tower bottom;
A quinoline circulating supply pipe connected to the “first tower supply pipe” and circulating and supplying the “second tower” bottoms to the “first tower”;
A "second column" overhead distilling tube for removing a fraction containing carboxylic acid as a main component from the "second column"overhead;
A “second tower” intermediate part discharge pipe for extracting the remaining mixed liquid of the dimethylamide compound from the intermediate height position of the “second tower”,
The “second tower” middle discharge pipe is connected to the “first tower supply pipe”,
It is a device that separates dimethylamide compound and carboxylic acid by distillation,
In addition, 1% by weight or more and 50% by weight or less of the total amount of the dimethylamide compound taken out are distilled off from the top of the “first column”, and the remainder is further purified as a dimethylamide compound of the “first column”. A distillation separation device that can be taken out from an intermediate height position. Further, a branch pipe which branches from the bottom pipe of the “second tower” and supplies half or less of the bottom liquid to the quinoline recovery tower,
14. The distillation / separation apparatus according to claim 12, further comprising: a quinoline recovery column for distilling the liquid to separate and remove high-boiling impurities contained in the quinoline. Furthermore, a `` hydrolysis reactor '' for flowing a mixed solution of a dimethylamide compound and a carboxylic acid and an acid anhydride thereof, and converting the acid anhydride contained in the mixed solution into a carboxylic acid,
A supply pipe for supplying a raw material liquid from the “hydrolysis reactor” to a “dehydration distillation column”;
A `` dehydration distillation tower '' that distills water contained in the raw material liquid from the top of the distillation tower,
The “first column” is provided at the bottom of the “dehydration distillation column”, and the dehydrated liquid obtained at the bottom of the “dehydration distillation column” is discharged to the bottom. A “dehydration distillation tower” bottom pipe connected to the supply pipe, a supply pipe for supplying a liquid distilled from the top of the “first tower” to the “hydrolysis reactor”,
The distillation separation device according to any one of claims 12 to 14, comprising: Further, a water circulation supply pipe for supplying a liquid containing water distilled as a main component from the top of the “dehydration distillation column” to the “hydrolysis reactor”,
The distillation separation device according to any one of claims 12 to 15, comprising:

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