JP4271423B2 - Method and apparatus for separating dimethylamide compound and carboxylic acid by distillation - Google Patents

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]
BACKGROUND OF THE INVENTION
The present invention relates to a technique used when a mixed solution containing a carboxylic acid and a dimethylamide compound is separated into components.
[0002]
[Background Art and Problems to be Solved by the Invention]
As dimethylamide compounds, dimethylformamide, dimethylacetamide and the like are used in many production processes as solvents. These are also used as solvents in polymerization processes of various polymer compounds and molding processes of fibers, artificial leather, membranes and the like.
[0003]
In these steps, carboxylic acid may be mixed in the dimethylamide compound as a solvent. Specifically, acetic acid may be mixed in the formulation 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 the production process, or the reaction raw material is discharged unreacted or discharged as a reaction product, it is often in a mixed state of various components. Solvents and unreacted substances are required to be separated into components and used again in the production process, or for the production process in which these substances are products, it is necessary to separate and take out the target substance alone.
[0005]
However, when the distillation operation is performed to separate and remove each component from the mixed solution containing the carboxylic acid and the dimethylamide compound, it is difficult to completely separate these two components because they 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 on a weight basis is: When the boiling point rises to about 165 ° C., it cannot be separated because it evaporates while maintaining the mixing ratio. Therefore, for example, if 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 azeotrope, so that 70 g of dimethylformamide can be separated, but the highest azeotrope is separated and recovered. I can't.
[0007]
In the case of dimethylformamide and formic acid, a maximum azeotrope with a boiling point of 163 ° C. is formed at a mixing ratio of about 31/69 on a weight basis. Dimethylacetamide likewise forms the highest azeotrope with formic acid and acetic acid.
[0008]
As described above, when the mixed liquid of carboxylic acid and dimethylamide compound becomes an azeotropic mixture composition and it is difficult to recover the dimethylamide compound, the acetic acid component is converted to an alkali such as caustic soda prior to the distillation operation. Treat with neutralization. And after producing | generating salt, such as sodium acetate, by neutralization reaction, the salt used as solid content is removed using means, such as an evaporation process. According to this method, a solution containing no acetic acid is obtained. For example, a method is known in which dimethylformamide is purified by distillation after adding an amino compound to the neutralization point with respect to dimethylformamide containing formic acid discharged in the polyurethane production process (for example, Patent Document 1). The solution thus obtained can be distilled to separate and recover dimethylformamide. However, acetic acid components cannot be recovered by this method, and the load of neutralization reaction / solids separation operation is large, and solid waste must be treated.
[0009]
As another means for solving the problem of the azeotropic mixture composition in the distillation separation, there is a method of adding a solvent that acts as an entrainer (for example, Patent Document 2 and Patent Document 3). In the method of using toluene as an entrainer and azeotropically separating acetic acid together with toluene, the acetic acid can be extracted into water for 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 a concentration direction rich in acetic acid. Excess dimethylformamide can be removed as a vapor. Therefore, in this method, each component can be isolated without requiring wastewater treatment.
[0011]
However, when the dimethylformamide obtained as described above is applied to various uses, contamination of impurities becomes a big problem. For example, when using dimethylformamide 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 examination of the present invention that dimethylformamide extracted by a method of adding a quinoline compound (for example, Patent Document 5) contains moisture as an impurity. That is, the present inventors have newly found a problem that water is mixed into the obtained dimethylformamide even when tested using a raw material liquid that has been sufficiently dehydrated and distilled to remove moisture.
[0013]
Accompanying the above water contamination problem, the generation of impurities due to the hydrolysis reaction of the dimethylamide compound has also become a problem. For example, in the hydrolysis of dimethylformamide, it is known that dimethylamine and formic acid are generated by side reactions (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 acid anhydride, the equilibrium of this reaction is biased toward the acetic acid side and it is unlikely that water will be generated. However, as a reaction that occurs only in the presence of isoquinoline, water is eventually generated. The entry of water, which is an impurity generated in such a minute amount, is a phenomenon newly found by carrying out a distillation separation method using a quinoline compound, and the purity of dimethylformamide extracted by distillation is lowered. Cause. Therefore, it becomes a big problem in applications that require high purity.
[0015]
As a 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 point product. However, formic acid remains with dimethylformamide forming the highest azeotrope composition. Therefore, in order to obtain dimethylformamide having a high purity, a distillation operation for separating and removing formic acid is required, and there has been a problem that distillation equipment, distillation operation and energy consumption are large.
[0016]
The present invention seeks to improve practical problems by improving the distillation system using the latter 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]
Chemical Engineering Vol.16, No.2, p391, Tsuneaki Fujiwara, 1990
[Non-Patent Document 2]
Shinji Hattori; Chemical Equipment November 1980 issue p. 33-50
[Non-Patent Document 3]
Masamichi Sugita; Chemical Equipment March, 1984 issue p. 54-58
[0018]
[Means for Solving the Problems]
The present inventors have completed the present invention as a result of intensive studies aimed at overcoming the contamination of impurities caused by water generation in the conventional system. That is, the present invention:
A method of adding a quinoline to a raw material mixture containing a dimethylamide compound and a carboxylic acid and distilling the dimethylamide compound. It is a distillation separation method and apparatus characterized in that it is distilled from the top of the column and the remainder is extracted as a further purified dimethylamide compound from the middle height position of the distillation column.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The raw material mixture used for the distillation of the method of the present invention is a mixture containing carboxylic acid such as acetic acid and a dimethylamide compound such as dimethylformamide. In the present invention, quinolines are added to the raw material mixture and distilled.
[0020]
As the raw material mixture, the composition formula (CH ₃ ) ₂ NCOR, 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} Specific examples include carboxylic acids represented by COOH and n selected from 0, 1, and 2, specifically, carboxylic acids such as acetic acid and formic acid, and dimethylamide compounds such as dimethylformamide and dimethylacetamide. For example, in the raw material mixed solution, a combination in which the carboxylic acid is acetic acid and the dimethylamide compound is dimethylformamide can be mentioned. In the raw material mixture, it is preferable that the content of the dimethylamide compound is larger than that of the carboxylic acid by weight. Examples of quinolines include quinoline, isoquinoline, and methylquinoline. Since a mixed solution of these carboxylic acid and dimethylamide compound forms the highest azeotropic mixture composition, it is difficult to separate by a normal distillation method. Quinolines may be included in the raw material mixture in advance, or may be added for distillation operation.
[0021]
The distillation operation of the present invention can be carried out using a normal distillation column, and it is not necessary to produce a special apparatus. The distillation column is basically a distillation column for purifying a dimethylamide compound, and the method of the present invention can be realized. The distillation tower may be a combination of two or more towers. A combination of two or more towers is preferable in order to separate the solvent more efficiently and accurately.
[0022]
The raw material mixture is supplied to the distillation tower. The raw material mixture is preferably supplied from the vicinity of the middle position of the distillation column. The supply of the raw material mixture can be selected from one place or a plurality of places 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 into a component that is evaporated by heating and distilled to the top of the column and a component from the bottom of the column. The “middle stage position” is a position above the bottom of the distillation column and below the position where the purified dimethylamide compound is taken out.
[0023]
The components at the bottom of the column are the highest azeotropic composition of carboxylic acid and dimethylamide compound having a high boiling point and the added quinoline, and these are both collected at the bottom of the column and taken out. At the top of the column, the dimethylamide compound in excess of the highest azeotropic composition has a relatively low boiling point and evaporates to reach the top of the column. This dimethylamide compound is distilled off.
[0024]
The most important and essential embodiment of the present invention is that the dimethylamide compound evaporated to the top of the column is distilled from the top of the column in an amount of 1% by weight to 50% by weight, and the rest is further removed. It is taken out from the middle height position of the distillation column as a purified dimethylamide compound (hereinafter referred to as a purified dimethylamide compound). Moreover, in this invention, the density | concentration of the quinolines of the tower bottom liquid of a distillation tower bottom part can be 10 weight%-95 weight%.
[0025]
In the present invention, the “intermediate height position” for removing the purified dimethylamide compound from the distillation column is a position that is at least one theoretical plate higher than the height position for supplying the raw material liquid to the distillation column, and It is a position that is at least one stage lower than the position at which the top reflux liquid of the distillation column is supplied. A more preferable “intermediate height position” is a position that is five or more steps higher than the height position at which the raw material liquid is supplied to the distillation column, and is 5% higher than the position at which the column top reflux liquid is supplied. The position is lower than the step. Here, “the feed height of the raw material liquid to the distillation column” is the middle position of the distillation column. The “position for supplying the reflux liquid at the top of the distillation tower” is the top.
[0026]
The higher the position at which the purified dimethylamide compound is removed from the distillation column, the higher the position relative to the height at which the raw material liquid is supplied to the distillation column, the more the impurities in the purified dimethylamide compound extracted from the intermediate height. It is advantageous that contamination with carboxylic acid and quinoline as a high-boiling substance can be easily reduced, or heat energy can be reduced by reducing the overhead reflux ratio in distillation. In addition, the lower the position relative to the position at which the top reflux solution of the distillation column is fed, the lower the boiling point of dimethylamine and water mixed in the purified dimethylamide compound extracted from the intermediate height. The advantage is that it can be easily reduced or the heat reflux 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 at which the column reflux liquid is supplied. The purified dimethylamide compound extracted from the middle height position of the distillation column has impurities contained in a weight ratio of 1/1000 to 1/3 from the dimethylamide compound distilled from the top of the distillation column. Significantly less purification.
[0027]
Here, “one stage” is an actual shelf in the shelf type distillation column, but it is a gas-liquid contact method using a filler and no shelf is used. It means the height of the filler that provides the distillation separation performance corresponding to one stage of the shelf. Such a theoretical stage of the filler is described as “HETP” (height equivalent to a theoretical plate) in, for example, page 134 of the 4th edition of the Physical and Chemical Dictionary (Iwanami Shoten, published in 1987). The quantitative handling thereof is clearly described, for example, on page 598 of Chemical Engineering Handbook Revised Edition 6 (Edited by Chemical Engineering Society, Maruzen, 1999).
[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 upper part of the tower so that the liquid and the vapor come into contact with each other. By contacting, components having a low boiling point among impurities contained in the vapor are further transported to the top of the column and concentrated and discharged. Further, in this distillation method using quinolines, it has been found in the examination of the present invention that water is generated, but water having a relatively low boiling point is concentrated toward the upper part of the distillation column. This water causes hydrolysis of the dimethylamide compound, generating dimethylamine. Since this dimethylamine has a low boiling point, it is further discharged to the top of the column. The formic acid generated simultaneously in this hydrolysis reaction forms the highest azeotrope with the dimethylamide compound, behaves as a high boiling point substance, and is concentrated to 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 tower is refluxed and flows down, low-boiling impurities such as water and dimethylamine are dissipated to the upper part by contacting with the distilled component vapor, and formic acid is Separated to the bottom of the tower. Therefore, a liquid mainly composed of dimethylformamide taken out from the column intermediate height can be obtained as a more purified dimethylamide compound with less impurities.
[0030]
Such a side reaction in which water is generated or hydrolyzed becomes more significant as the operating temperature is higher, but can be adjusted by lowering the distillation temperature by lowering the operating pressure of the distillation column. In this respect, the preferable range of the distillation temperature is 50 ° C to 200 ° C, more preferably 80 ° C to 120 ° C.
[0031]
Increasing the proportion of the dimethylamide compound fraction extracted from the top of the column can prevent impurities such as water and dimethylamine from entering the purified dimethylamide compound solution extracted from the middle height of the column. . However, on the other hand, the extraction amount of the more purified dimethylamide compound is reduced. Therefore, the ratio of the top distillate to the total amount of dimethylamide taken out is preferably 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 more stably eliminated. When the amount is 30% by weight or less, the amount of the purified dimethylamide compound taken out from the middle height position of the column increases, and the operation can be performed more efficiently.
[0032]
Moreover, when the reflux ratio (= refluxed liquid amount / distillate liquid amount) at the top of the distillation column is increased, impurities in the purified dimethylamide compound can be reduced. The reflux ratio can be about 1-50, and is preferably in the range of 5-20.
[0033]
In the present invention, the dimethylamide compound liquid is extracted from the middle height position of the distillation column. As a preferred mode of implementation, only the liquid flowing down from a certain position of the distillation column can be discharged, the fixed amount can be extracted as a more purified dimethylamide compound, and the remaining liquid can be returned to the distillation column and flowed 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 cross section in the tower 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 can be refluxed to a position immediately below the blocked position, and then dispersed and flowed down again across the tower section in order to discharge liquid from the distillation column. Although the falling liquid is blocked at the middle position of the distillation column, the distilled 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 of the amount of liquid flowing down in the tower. If the amount of liquid withdrawn is too large, the amount of liquid flowing down at the bottom of the tower may be reduced and the gas-liquid contact performance may be reduced. In addition, if the amount of liquid withdrawn exceeds a majority, a slight change in the flow rate and the amount of liquid flowing down the column will have a significant effect on the amount of liquid flowing back to the lower part of the column, and there will be no liquid in the lower part of the column. Problems may arise.
[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 water can be concentrated when the dimethylamide compound is distilled at the top of the column and the purified dimethylamide compound is taken out from the liquid at the middle height of the column to solve the problem. . That is, water contamination can be substantially eliminated, and chemical reaction substances such as acetic acid, acetic anhydride, and quinolines that are considered to be related to water generation are not mixed into the purified dimethylamide compound.
[0037]
An additional embodiment of the method of the present invention is a method comprising a dehydration distillation step prior to the basic distillation operation. In this method, the component distilled from the top of the dimethylamide compound purification distillation column can be supplied to the dehydration distillation column used for the dehydration distillation step and recycled. The water contained in the dimethylamide compound is removed by the dehydration distillation step, so that the mixed solution having a water concentration of 0.1% by weight or less, more preferably 0.01% by weight or less is used in 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 by a hydrolysis reaction is known. In order to suppress this, it is preferable to lower the operating temperature of the dehydration distillation process as much as possible. Specifically, it can be carried out at 150 ° C. or lower, more preferably 100 ° C. or lower, by a vacuum distillation method.
[0038]
Yet another embodiment of the present invention is a method of providing a hydrolysis step prior to the dehydration distillation step. This method is a more preferred embodiment when acetic anhydride is contained in the raw material mixture. In this case, the component distilled from the top of the dimethylamide compound purification distillation column can be recycled as a feed solution to the hydrolysis reactor used in the hydrolysis step. The dimethylamide compound distilled from the top of the “purification distillation column” and recycled may contain dimethylamine having a low boiling point among the hydrolysis by-products as well as moisture. This dimethylamine can be rapidly reacted with acetic anhydride and converted to dimethylacetamide. In the hydrolysis step, the main purpose is to cause a hydrolysis reaction of acetic anhydride. If the internal temperature of the hydrolysis reactor used in the hydrolysis step is too low, the reaction proceeds slowly. On the other hand, when the temperature is too high, hydrolysis of the dimethylamide compound becomes significant in addition to the intended reaction. Therefore, it is preferable to operate at a temperature of 50 ° C to 100 ° C. Since the target reaction proceeds in about 10 minutes to 2 hours, it is preferable to use either a batch type reactor or a flow type continuous reactor. In operation, when a flow-type continuous reactor is used, it can be realized by maintaining the temperature in the tubular reactor for a predetermined residence time. The internal pressure of the tubular reactor may be set higher than the storage state of the raw material liquid. With such a setting, it is possible to prevent gas components such as air dissolved in the raw material liquid during storage from being evaporated and bubbled in the heated reactor.
[0039]
The amount of water supplied to the hydrolysis reactor is sufficiently larger than the amount necessary for reacting acetic anhydride contained in the raw material liquid, but is 1% by weight to 30% by weight with respect to the total amount of the raw material liquid. Preferably, it can be made into 10 to 30 weight%. The reaction proceeds slowly when the amount of water is small. If the amount of water is too large, dehydration distillation becomes large and requires a large amount of heat energy for distillation. Even if the raw material liquid contains, for example, about 5% by weight of acetic anhydride by the treatment with the hydrolysis reactor, most of the acetic anhydride is converted to acetic acid so that the acetic anhydride content is about 10 ppm to 1000 ppm. it can.
[0040]
In addition, the water distilled from the top of the dehydrating distillation tower may contain a small amount of dimethylamide compound or carboxylic acid in addition to dimethylamine, which is a low-boiling component. In the case of not recirculating as described above, it is desirable to perform detoxification treatment as waste water from the distillation process. Therefore, in this invention, the water supplied to a hydrolysis reactor may be contained in the raw material liquid, and may be added additionally. In one preferred embodiment, water distilled from the top of the dehydration distillation column is recycled as feed water to the hydrolysis reactor. In this method of recirculating water, the amount of process discharge water is reduced, so the burden of wastewater detoxification treatment is reduced.
[0041]
The water distilled from the top of the dehydration distillation column contains dimethylamine produced by hydrolysis of the dimethylamide compound. However, this dimethylamine reacts quickly with acetic anhydride in the hydrolysis reactor and is converted to dimethylacetamide.
[0042]
In the present invention, as an embodiment that can be additionally selected, in addition to the above-described dimethylamide compound purification distillation column (first column), the second and third total three distillation columns may be used. it can. For example, when two towers are used, the azeotropic mixture composition of dimethylamide compound and carboxylic acid and quinolines are taken out from the bottom of the first distillation tower and introduced into the second distillation tower. The quinoline can be concentrated and taken out from the bottom of the second column, and can be circulated and fed to the first distillation column. When a three-column distillation tower is used, the azeotropic mixture composition of dimethylamide compound and carboxylic acid and quinoline are taken out from the bottom of the first distillation tower and introduced into the second distillation tower. The boiling-point quinoline can be concentrated and taken out from the bottom of the second column, and can be circulated and fed to the first distillation column. Furthermore, a mixed liquid 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 can be distilled from the top of the third distillation column, and the liquid in which dimethylamide remains can be taken out from the bottom of the third tower and circulated and supplied to the first tower.
[0043]
Here, if this distillation operation is continued for a long time, there is a problem that impurities having a higher boiling point than the boiling point of quinolines generated by a small amount of side reaction or contained in the raw material liquid accumulate. If the quinoline concentrate is dispensed, the trace amount of high-boiling impurities contained in it is also taken out at the same time. Therefore, the larger the dispense amount, the smaller the amount of trace high-boiling impurities accumulated in the distillation column system. . However, if the amount of the quinoline concentrate is dispensed too much, then the addition of a step of removing high boiling impurities from the quinoline concentrate becomes large.
[0044]
Therefore, as one additional embodiment of the present invention, the amount of quinoline concentrated liquid taken out from the bottom of the second column and circulated to the first distillation column is less than half, preferably 1% by weight. -30% by weight is extracted. The concentrated quinoline solution thus taken out can be distilled and purified in a separate quinoline recovery tower to remove impurities having a high boiling point, and then the purified quinoline can be taken out. Alternatively, the quinoline concentrate can be used again by supplying it to the first distillation column. From the top of the second distillation column, a mixed liquid of the remaining dimethylamide compound and carboxylic acid from which the quinolines have been separated and removed is distilled. By supplying this to the third distillation column, the highest azeotropic mixture composition in the absence of quinoline is separated to the bottom of the column, and excess acetic acid can be concentrated and distilled to 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 again to the first column to extract the dimethylamide compound.
[0045]
Another embodiment of the present invention is characterized in that an amount less than half of the liquid extracted from the bottom of the third tower and recirculated to the first tower, preferably 1 to 30% by weight, is taken out. A method of branching out of the pipe and letting it flow out can be selected. By-products from the hydrolysis of the dimethylamide compound are concentrated in the outflow component, and can be efficiently removed. A by-product in the distillation of dimethylformamide is formic acid. Further, dimethylacetamide generated by the reaction of dimethylamine, which is another hydrolysis by-product, with acetic anhydride, which is an acid anhydride, is also concentrated in this effluent component and can be efficiently removed.
[0046]
As one embodiment of the apparatus for distilling and separating the dimethylamide compound and the carboxylic acid of the present invention, the above distillation separation method can be realized, and it comprises three distillation columns.
[0047]
An embodiment of the apparatus of the invention using three distillation columns is illustrated by FIG. FIG. 1 is a conceptual diagram of an apparatus 10 composed of 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 piping.
[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 the purified dimethylamide compound liquid is provided at the middle height position of the tower. This pipe is called “intermediate part discharge pipe”. The first column intermediate portion discharge pipe 22 has a structure in which a part of the distilled flow-down liquid is extracted at the intermediate height position of the column and the remaining flow-down liquid is further flowed downward. The steam rising in the first tower 12 flows upward without being extracted.
[0049]
The first tower bottom can take-out pipe 24 is connected to a second tower supply pipe 26 connected to the second tower 14, and supplies the liquid discharged from the tower bottom of the first tower 12 to the second tower 14.
[0050]
The second distillation column has a column bottom can tube 28, which is connected to a circulation supply tube 30 that supplies quinolines again to the first column.
[0051]
In this apparatus, a pipe connected to the first tower supply is branched from the bottom of the second tower, and the supply amount to the first tower is adjusted by allowing a part of the fluid to flow out by adjusting the flow rate in the pipe. It can also be configured. Specifically, a branch pipe can be provided in the middle of the tower bottom can take-out pipe 28, and a part of the fluid can be discharged to a treatment step for removing high-boiling impurities. The tower top distillation pipe 32 of the second tower 14 is connected to the third tower supply pipe 34, and supplies the second tower top distillate to the third tower 16.
[0052]
The third tower 16 includes a tower top distillation pipe 36 and a tower bottom can discharge pipe 38. The third tower bottom can discharge pipe 38 is connected to the circulation supply pipe 30 so that the third tower bottom liquid can be supplied to the first tower 12. Note that the circulation supply pipes may be provided separately or may be joined in the middle as shown in FIG.
[0053]
Further, as a feature of the present invention, the pipe connected from the third tower bottom can take-out pipe to the first tower supply can be branched in the middle, and the flow rate can be adjusted to flow out a part of the fluid. Specifically, a branch pipe 39 is provided.
[0054]
As one embodiment of the apparatus for distilling and separating the dimethylamide compound and the carboxylic acid of the present invention, the above-described distillation separation method can be realized, and it comprises two distillation columns.
[0055]
An embodiment of the apparatus of the invention using two distillation columns is illustrated by FIG. FIG. 2 is a conceptual diagram of an apparatus 50 composed of 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 piping.
[0056]
The first column 52 includes a raw material liquid supply pipe 56 for supplying a raw material liquid containing a dimethylamide compound and a carboxylic acid and quinolines. The azeotropic composition of dimethylamide compound and carboxylic acid and the quinolines are taken out from the bottom bottom cannula 58 of the first column 52. Basically, 1% by weight to 50% by weight of the excess amount of the dimethylamide compound exceeding the azeotropic composition mixing ratio is discharged from the top of the first column, and the remaining liquid is passed through the first column intermediate height. Then, it is extracted as a purified dimethylamide compound by the intermediate part discharge pipe 60. The liquid extracted from the bottom of the first tower is introduced into the second tower 54 through the tower bottom can take-out pipe 58 through the second tower supply pipe 62. The second tower 54 is provided with a tower top distillation pipe 61 at the tower top and a tower bottom can outlet 64 at the tower bottom. Then, the high-boiling quinolines are concentrated in the second column 54, and are taken out from the bottom can take-out pipe 64 of the second column 54. A payout pipe 65 may be provided at the intermediate height position of the second tower and connected to a circulation supply pipe 66 that circulates and supplies the first tower. The second tower bottom can pipe 64 is connected to the circulation supply pipe 66, and the second tower bottom liquid can be supplied to the first tower 52. The circulation supply pipe may be provided separately and independently.
[0057]
As an additional embodiment of the apparatus of the present invention, the above two or three distillation columns are combined with one or more apparatuses of a hydrolysis reactor, a dehydration distillation column, or a quinoline recovery distillation column. is there. Basically, the object of the present invention can be realized by two or three distillation columns, but from the viewpoint of removal of mixed water and acetic anhydride, the above-mentioned additional embodiments can be preferably used. 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 apparatuses of the recovery distillation column, and further, three apparatuses of the three hydrolysis reactors, the dehydration distillation tower, and the quinoline recovery distillation tower may be added.
[0058]
One example device 70 of an additional aspect of the invention is illustrated by FIG. In FIG. 3, 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 tower 72 includes a raw material mixture supply pipe 82, a first tower tower top distillation pipe 84, and a first tower middle section extraction pipe 86. The first tower bottom can take-out pipe 88 is connected to the second tower 74 and the second tower supply pipe 90, and the first tower bottom liquid is supplied to the second tower 74. The second tower 74 includes a second tower top distillation tube 92 and a second tower bottom can outlet 94. The second tower bottom can outlet 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 tower middle part, and the second tower intermediate part discharge pipe 98 is connected to a circulation supply pipe 96 to the first tower 72. Here, as a further feature of the present invention, a pipe connecting from the second tower intermediate portion discharge pipe 98 to the circulation supply pipe 96 is branched. Specifically, a branch pipe 100 can be provided. Thereby, it can be set as the structure which adjusts the supply_amount | feed_rate to a 1st tower | column by flowing out 1 part of the fluid in piping by flow volume adjustment. Note that the circulation supply pipes may be provided separately or may be joined in the middle.
[0060]
In the apparatus shown in FIG. 3, the hydrolysis reactor 76 is connected to the dehydration distillation column 78, and the dehydration distillation column 78 is connected to the first column 72. It is preferable to install the hydrolysis reactor 76 when acetic anhydride is mixed in the raw material mixture. First, the raw material mixture is supplied to the hydrolysis reactor 76 through the raw material supply pipe 102.
[0061]
The raw material mixture that has undergone the reaction by the hydrolysis reactor 76 is supplied to the dehydration distillation column 78 through the dehydration distillation column supply pipe 104. The dehydration distillation column 78 plays a role of removing much of the water mixed in the raw material mixture. The liquid withdrawn from the bottom of the dehydration distillation column 78 is supplied to the “first tower” 72 via the supply pipe 82 of the first tower from the bottom liquid can discharge pipe 106.
[0062]
Here, the component distilled from the top of the first column 72, which is a dimethylamide compound purification distillation column, and the component distilled from the top of the dehydrating distillation column 78 used in the dehydration distillation step are the top of the first column From the distillation pipe 84 and the tower top distillation pipe 108 of the dehydration distillation tower 78, it can be circulated again as a supply liquid to the hydrolysis reaction tower 76 through the circulation supply pipe 110.
[0063]
When the amount of water is insufficient only by circulating the distilled water from the top of the dehydration distillation tower, water is added to the raw material liquid supply pipe 102 from the outside, and the water content is 1 It is preferable to adjust so that it may become 50 to 50 weight%. If water is included in the raw material feed solution in advance and the amount of water becomes excessive when the entire amount of water distilled from the top of the dehydration distillation tower is circulated, a part of the water distilled from the top of the dehydration distillation tower will be processed. Only the necessary amount can be circulated as wastewater.
[0064]
A quinoline recovery tower 80 is added to the distillation tower. The purpose of the quinoline recovery tower is to remove impurities accumulated in the distillation operation. In FIG. 3, from the second tower bottom can take-out pipe 94, the quinoline concentrate is taken out of the quinoline concentrate that is taken out and circulated to the first tower 72. Subsequently, the quinoline recovery tower is extracted. 80 is introduced through a supply pipe 112 and purified by distillation. Purified quinolines after removal of high-boiling impurities can be obtained. It can also be supplied to the first tower again.
[0065]
The component after the quinoline is removed in the second column 74 has an excess of carboxylic acid as compared with the azeotropic mixture composition. The excess carboxylic acid flows out from the top of the distillation column, and the remaining liquid flows out from the intermediate part discharge pipe 98 as an azeotropic mixture composition from the middle height of the tower and is supplied to the first tower through the circulation supply pipe 96. Is done. Here, it is possible to select a method in which the branch pipe 100 discharges an amount equal to or less than half of the liquid discharged from the intermediate height of the second tower and circulated to the first tower supply. Note that the circulation supply pipes may be provided separately or may be joined in the middle.
[0066]
The example in which the apparatus is additionally installed in two distillation columns has been described with reference to FIG. 3. In the present invention, the hydrolysis reactor, the dehydration distillation column, and the quinoline recovery distillation column are one distillation column. Even three towers can be added. Moreover, you may add any one or two apparatuses among a hydrolysis reactor, a dehydration distillation tower, or a quinoline collection distillation tower. In this case, the circulation supply pipe is preferably connected to the pipe for supplying the raw material mixture first in the embodiment of the present invention. Note that the circulation supply pipe may be a plurality of separate and independent pipes, or may be a mode of joining in the middle as indicated by 110 in FIG. Moreover, in the apparatus comprised by 3 towers, it is good to branch a 2nd tower bottom bottom discharge pipe and to connect piping to a quinoline collection distillation tower.
[0067]
The distillation column is provided with a condenser at the top of the column and a reboiler at the bottom of the column in order to exert its function.
[0068]
Although not specifically illustrated in the figure, the vapor at the top of each distillation column is condensed and liquefied by a condenser, one part is taken out as a top distillate, and the remaining liquid is refluxed to the top. . Further, the bottom liquid of the distillation tower is heated and evaporated by the reboiler to generate rising vapor in the distillation tower.
[0069]
As mentioned above, although the method and apparatus for distilling and separating the dimethylamide compound and carboxylic acid according to the present invention were described, the present invention can be applied to the synthesis of, for example, 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 distillation purification of these solvents. When this solvent is discharged in the state of evaporating gas from the molding process stage or the drying process, it can be collected by cooling and liquefying by a system such as a condenser or a scrubber, and then subjected to the distillation of the method of the present invention. Moreover, when acetic anhydride is contained in the collected solvent, water can be added to hydrolyze the acetic anhydride to convert it into acetic acid, and then subjected to the distillation of the method of the present invention. Further, when water is added in advance in the stage of collecting added water or solvent, dehydration distillation for the purpose of dehydration treatment can be performed prior to the distillation of the method of the present invention. Thus, the separated and purified dimethylformamide recovered from the middle height position of the distillation column by applying the present invention can be reused as a solvent. Since the degree of purification is high, it can be used for, for example, polymerization of polyimide resin and film formation.
[0070]
Although the present invention has been described above, the present invention is not limited to these embodiments, and various improvements, changes, and modifications can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It can implement in the aspect which added.
[0071]
【Example】
Next, an embodiment of a method and apparatus for distilling and separating a dimethylamide compound and a carboxylic acid according to the present invention will be described in detail with reference to the following examples.
[0072]
In the examples, “%” indicates wt%. “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 columns.
[0074]
(Example 1)
As the distillation tower, two stainless steel cylinders (outer diameter: 60 mm, inner diameter: 55 mm, total length: about 2500 cm) and two stainless steel Dickson packings (6 mmφ) filled as the packing material were used (first tower). The second tower). A filler was filled into 150 mm from the lower part of the stainless steel cylinder of the first tower, and a space 250 mm was provided thereon, and a nozzle for circulating supply liquid from the second tower was inserted. A 150 mm filler was filled thereon, and a raw material liquid supply nozzle was inserted into the upper space 250 mm. Further, a filler of 300 mm was filled above, and a liquid extraction part at the middle height of the tower was attached to a portion of the upper space of 450 mm. Subsequently, a 450 mm filler was put thereon, and a reflux liquid supply nozzle was inserted into the space above it. The second tower was filled with a filler 300 mm from the bottom of the stainless cylinder, provided with a space 300 mm above it, and inserted a supply nozzle for introducing the liquid discharged from the bottom of the first tower. A 150 mm filler was filled thereon, and a liquid extraction part at the middle height of the tower was attached to the 450 mm upper space. Subsequently, a 450 mm filler was put on top and a reflux liquid supply nozzle was inserted into the space above it. A condenser is installed at the top of the first tower and the second tower, and a reboiler is installed at the bottom of the tower.
[0075]
A device with the following outline was produced. 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 and removes one part thereof as a column top distillate, and connects the remaining liquid to the column top.
A liquid extraction part (side cut part) at the middle height position of the tower was provided below the top of the first distillation column with a packing material height of 30 cm. The pipe from the side cut liquid was a pipe that took out a part of the side cut liquid and refluxed the remaining liquid to the upper portion of the filler below.
A raw material supply pipe was provided at a lower position with a height of the filler of 30 cm from the side cut portion.
A pipe for supplying a liquid recirculated from the second distillation column was provided at a lower position with a filler height of 15 cm from the raw material supply pipe.
Further, a tower bottom liquid reservoir was provided at a lower position with a filler height of 15 cm. A reboiler was provided at the bottom of the column to evaporate the column bottom liquid and provide a pipe for extracting a certain amount of the column bottom liquid and supplying it to the second column.
[0076]
Side cut liquid extraction piping was provided 45 cm below the top of the second distillation column. A part of the side cut liquid was extracted from the second distillation column, and the remaining liquid was used as a pipe for refluxing to the upper part of the filler below.
A supply unit for the liquid extracted from the bottom of the first tower was further provided 15 cm below the side cut position. A liquid reservoir at the bottom of the tower was provided 30 cm below the side cut part. A reboiler was provided at the bottom of the second distillation column.
The tower bottom liquid was heated and evaporated by a reboiler to raise the vapor inside the tower, and a pipe for extracting a certain amount of the column bottom liquid was used. The side cut liquid of the second distillation column and the liquid extracted from the bottom of the second column were recirculated and supplied to the first column.
[0077]
The first column tower bottom liquid was heated to 100 ° C. with a reboiler and evacuated using a vacuum pump to adjust the pressure conditions in the tower interior space, and the operating pressure was 6.0 kPa-abs. It was. The feedstock solution to the first tower is a mixed solution of dimethylformamide: 79.5% by weight, acetic acid: 14.8% by weight, isoquinoline: 5.1% by weight, and the moisture contained as impurities is 0 0030% by weight. The supply liquid amount is about 98 g / h.
[0078]
It was taken out from the top of the first distillation column under distillation conditions with a flow rate of 8.5 g / h. In this liquid, in addition to dimethylformamide, a water content of 7000 ppm and dimethylamine of 6000 ppm were detected as impurities.
[0079]
Further, it was taken out from the first distillation column side cut under distillation conditions with 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 dimethylamine was 25 ppm. The extraction ratio of dimethylformamide from the side cut is 88.5%.
The composition of the liquid mixture extracted from the bottom of the first distillation column at a flow rate of 291 g / h contained 60% isoquinoline, 12% dimethylformamide, and 12% acetic acid.
The liquid recirculated from the second column and introduced into the first column was a flow rate of 267 g / h.
[0080]
The second column tower bottom liquid was heated to 150 ° C. with a reboiler and evacuated using a vacuum pump to adjust the pressure condition in the tower inner space, and the operating pressure was 7.3 kPa-abs. It was.
A flow rate of 70 g / h was discharged from the second column side cut, 7 g / h of which was purged, and the remainder was recycled to the first column. The purged side cut solution contained 45% dimethylformamide and 35% acetic acid.
A liquid containing isoquinoline as a main component was extracted from the bottom of the second tower at a flow rate of 204 g / h and recycled to the first tower together with the side cut liquid.
The distillate distilled 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)
Except for not performing the side cut in the first tower, the same raw material composition was used in the same apparatus as in Example 1, and the operating temperature and pressure were also operated in the same manner.
When a flow rate of 73.5 g / h was caused to flow out from the top of the first column, 853 ppm of water and 715 ppm of dimethylamine were contained as impurities in the dimethylformamide. Except not performing the side cut of the 1st tower, it carried out similarly to Example 1 about the 1st tower bottom extraction, the feed of the raw material to the 1st tower, the recirculation liquid from the 2nd, and the 2nd tower operation conditions.
[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 water in the dimethylformamide obtained in Example 1 according to the method of the present invention is 20 ppm and dimethylamine is 25 ppm. Compared with the comparative example, the impurity content could be remarkably reduced.
[0083]

[0084]
Hereinafter, Example 2 and Comparative Example 2 are apparatuses using one distillation column.
[0085]
(Example 2)
A stainless steel cylinder (outer diameter: 60 mm, inner diameter: 55 mm, total length: about 2500 cm) was used as the distillation tower, and a stainless steel Dixon packing (6 mmφ) was used as the filler inside the cylinder. The configuration of the distillation tower was the same as that of the first column in Example 1. A condenser is installed at the top of the column to perform condensate distillation and reflux to the top. There is a reboiler at the bottom of the tower to drain the liquid. From the middle height of the tower, the raw material liquid is supplied and the side cut liquid is extracted. A side cut liquid extraction position is provided at a position separated by about 30 cm from the top of the tower, and the raw material mixture is supplied at a position further separated by 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 moisture: 0.0047%. The reflux ratio at the top of the column was about 20, and a reflux liquid with a flow rate of about 150 g / h was allowed to flow down. When the distillate from the top of the distillation column had a flow rate of 7.4 g / h, its component was approximately DMF, containing about 0.5% moisture and about 0.1% DMA.
[0087]
In the side cut section, the entire top reflux liquid (about 150 g / h) is blocked and circulated through a conduit to a 50 ml receiving tank provided in the vicinity, and a part of the liquid (74 g / h) is side cut. And extracted as purified DMF. The remaining liquid was dropped back into the tower again. The water content in the purified DMF was 0.007%, the dimethylamine content was about 0.002%, and acetic acid was also 0.003%. The extraction ratio of dimethylformamide from the side cut is 98.9%.
[0088]
Below that, there is a liquid pool at the bottom of the column with a packed portion of about 30 cm apart, which is heated and evaporated as a reboiler and a constant amount (flow rate 271 g / h) is withdrawn. The composition extracted from the bottom of the column was DMF: 16%, acetic acid 15%, isoquinoline: 68%, and the like.
[0089]
The bottom liquid of the distillation tower was heated to 100 ° C. with a reboiler and evacuated using a vacuum pump to adjust the pressure conditions in the internal space of the tower. The operating pressure was 6.0 kPa-abs. It was.
[0090]
(Comparative Example 2)
The distillation column used in the experiment is made of glass, and is filled with a filler (glass Raschig ring 3 mmφ) in a cylinder having an inner diameter of 30 mmφ and a total length of about 1500 mm. The total height from the tower bottom reboiler to the tower top condenser is about 2500 mm. The raw material liquid supply from the middle position of the column is 122 g / h in flow rate, and the composition is DMF 29%, acetic acid 11%, isoquinoline 59% and water is about 0.005%.
[0091]
The side cut liquid was not withdrawn, and the DMF was taken out at a column top distillate of 22 g / h. As a result, 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 column bottom discharge liquid was set at a flow rate of 100 g / h, and the composition was DMF 15%, acetic acid: 13%, isoquinoline: about 72%, and acetic anhydride: 0.0025. Further, it was detected that about 0.005% of isoquinoline was converted to methyl isoquinoline. The operating pressure of the distillation column is 6.7 kPa-abs. It was. 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% moisture and 0.01% dimethylamine, whereas the moisture in the dimethylformamide obtained in Example 2 according to the method of the present invention is 0%. 0.007% and dimethylamine were 0.002%, and the impurity content could be significantly reduced as compared with Comparative Example 2.
[0094]

[0095]
Example 3 and Comparative Example 3 are apparatuses using four distillation columns.
[0096]
(Example 3)
A stainless steel cylinder (outer diameter: 60 mm, inner diameter: 55 mm) was used as a distillation tower, and four stainless steel Dixon packings (6 mmφ) were used as fillers inside the cylinder. A dehydration distillation column (length: about 2000 mm), a DMF purification distillation column (length: about 2500 mm), an acetic acid removing distillation column (length: about 2500 mm), and an isoquinoline recovery distillation column (length: about 1000 mm), respectively. 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 packing material is filled from the bottom of the column with 25 cm, a space part of 15 cm is provided, the packing material is filled with 20 cm, and the raw material liquid supply unit is provided in the space part of 15 cm. A filler of 45 cm was provided thereon, and the top was used as the tower top. The isoquinoline recovery distillation column has a structure in which a filler 30 cm is provided in order from the bottom connected to the reboiler, and the raw material liquid is supplied to the intermediate height 15 cm. The top was the tower top.
The hydrolysis reactor + dehydration distiller + DMF purification distiller + acetic acid removal distilling column are connected by piping in this order. A stainless steel tube (inner diameter 4 mmφ, length 10 m) was used as the hydrolysis reactor.
A condenser is connected to the tops of the DMF purification distillation column, acetic acid removal distillation column, and isoquinoline recovery distillation column. The condenser was liquefied and one part of the vapor was taken out as a column top distillate, and the remaining liquid was connected to reflux to the column top.
[0097]
The composition of the raw material liquid is DMF: 70%, acetic acid: 11%, acetic anhydride: 12%, isoquinoline: 2.5%, water: 3.5%, and this is fed with a metering pump at a flow rate of 42 g / h. Liquid was passed through the hydrolysis reactor. The reactor temperature was maintained at 80 ° C., a pressure control valve was attached to the outlet, and the pressure in the reactor was 0.2 MPa. At the reactor outlet, acetic anhydride was converted to acetic acid at a conversion rate of 99% or more. The liquid exiting the reactor was subsequently supplied to a dehydrating distillation column, water was separated and distilled from the top of the column, and the distilled water was circulated again to the hydrolysis reactor inlet. 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. It was.
[0098]
Distilled water produced at the top of the dehydration distillation column contained dimethylamine, but was converted to dimethylacetamide at the outlet of the hydrolysis reactor. By circulating and supplying a liquid mainly composed of water distilled from the top of a dehydration distillation column to the hydrolysis reactor inlet at a flow rate of about 10 g / h, the water concentration in the hydrolysis reactor is increased to 20% by weight. I made it. The liquid from which water was removed was extracted from the bottom of the dehydration distillation column, and the filler was supplied to a height position separated by 300 mm from the bottom of the dimethylformamide purification distillation column at a flow rate of about 50 g / h.
[0099]
The liquid at the top of the dimethylformamide purification distillation column is condensed into a condensate by a condenser, and a part thereof becomes a distillate at the top of the column, and the remainder is refluxed to the top of the distillation column. The reflux ratio is about 11, and the operating pressure is 6.0 kPa-abs. It was. A liquid with a flow rate of 8.5 g / h was distilled from the top of the purification distillation column, and this was also circulated and supplied to the hydrolysis reactor inlet.
[0100]
The refined column top distillate DMF contained about 0.35% water and about 0.1% dimethylamine. When purified DMF was side cut out at a flow rate of 26 g / h at a position about 30 cm below the top of the tower, water was 0.008% as impurities in DMF and DMA was 0.002%. The extraction ratio of dimethylformamide from the side cut is 75.4%.
[0101]
The liquid composition at the bottom of the purification distillation column is mainly composed of DMF: 23%, acetic acid: 15%, isoquinoline: 43%, etc., and is extracted at about 300 g / h and filled upward from the bottom of the acetic acid removal distillation column. Was fed to a position separated by 300 mm. The top reflux ratio of the acetic acid removing distillation column is 15, and the pressure is 7.3 kPa-abs. Was operated.
[0102]
The composition of the distillate flow rate of about 10 g / h in the “acetic acid removal distillation column” was about 90% acetic acid and about 10% DMF. The liquid at a position about 30 cm below the top of the column was side cut out at a flow rate of about 70 g / h, 3 g / h of which was purged, and the remainder was separated by 150 mm from the bottom of the dimethylformamide purification 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. "Acetic acid removal distillation column" The high-boiling components are concentrated at the bottom of the column, isoquinoline is contained in about 80%, and the remaining components are contained in the raw material liquid. Met. The liquid at the bottom of the column was withdrawn and supplied at a height of about 200 g / h from the bottom of the isoquinoline refining distillation column at a height of 150 mm.
[0104]
Isoquinoline and other high-boiling substances at the bottom of the acetic acid-removing distillation column are gradually brought from the feed liquid and gradually increase in accumulation. For this reason, an operation for recovering and distilling isoquinoline by extracting this increased liquid was performed. Since the test scale was small, the treatment liquid was collected and supplied to the isoquinoline recovery distillation column at a flow rate of about 50 g / h. The top reflux ratio of the isoquinoline recovery column is 10, and the pressure is 5.3 kPa-abs. The purified isoquinoline having a purity of 95% or more was obtained by adjusting the column top distillation to about 36 g / h. The column 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)
A 100 cc glass container was charged with dimethylformamide, acetic acid and isoquinoline at a mixing ratio of 25%, 10% and 65%, respectively, and maintained at 120 ° C., and the concentration of acetic anhydride over time was analyzed and measured. Although acetic anhydride was not detected at the beginning of charging, 0.014% acetic anhydride was detected from the liquid in the glass container after 1 hour and 0.029% after 2 hours.
[0107]
According to the result of Reference Example 1, acetic anhydride was generated in a mixed solution of dimethylformamide, acetic acid and isoquinoline. Presuming this, as one of the reasons why water is generated in the distillation tower in Examples 1, 2, 3 and Comparative Examples 1, 2, the following:
Acetic acid → acetic anhydride + water
It is possible that this reaction has occurred.
[0108]
However, the amount of acetic anhydride is very small compared to the amount of water detected in Comparative Example 2, and it is considered that there are other causes. Another cause is considered to be related to the occurrence of methyl isoquinoline observed in Comparative Example 2. Possible responses are:
Isoquinoline + acetic acid → methylisoquinoline + formic acid
Formic acid → water + carbon monoxide
It is. It is considered that water is generated by the reaction as described above.
[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 purified dimethyl compound having a high purity that improves the distillation method using the quinoline compound as an entrainer and overcomes the contamination of impurities. An amide compound can be obtained. In addition, the apparatus to which the method of the present invention is applied is a dimethylamide compound purification distillation column. By removing the purified dimethylamide compound from the middle height of the column, water generated in the distillation column as a trace impurity is distilled off from the top of the column. A highly purified dimethylamide compound with few impurities can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an apparatus for distilling and separating a dimethylamide compound of the present invention and a carboxylic acid comprising three distillation columns.
FIG. 2 is a conceptual diagram of an apparatus for distilling and separating a dimethylamide compound of the present invention and a carboxylic acid composed of two distillation columns.
FIG. 3 is a conceptual diagram of an apparatus for distilling and separating a dimethylamide compound of the present invention and a carboxylic acid, which is composed of two distillation columns and an addition apparatus.
[Explanation of symbols]
10: An example of an apparatus for separating the dimethylamide compound and carboxylic acid of the present invention by distillation
12; First tower
14; second tower
16; Third tower
18; First tower raw material liquid supply pipe
20; first tower top distillation pipe
22; First tower middle discharge pipe
24; first column tower bottom can pipe
26; Second tower supply pipe
28; bottom tower bottom can outlet
30; Circulation supply pipe
32; Second tower top distillate tube
34; Third tower supply pipe
36; Third tower top distillation pipe
38; Third tower bottom bottom can pipe
39; Branch pipe
50: Another example of apparatus for distilling and separating dimethylamide compound and carboxylic acid of the present invention
52; first tower
54; second tower
56; Raw material mixture supply pipe
58; first column tower bottom can outlet
60; first tower middle discharge pipe
62; Second tower supply pipe
64; second tower bottom can outlet
65; Second tower middle discharge pipe
66; Circulation supply pipe
70: Still another example of the apparatus for distilling and separating the dimethylamide compound and carboxylic acid of the present invention
72; first tower
74; second tower
76; hydrolysis reactor
78; Dehydrator
80; Quinoline recovery distillation tower
82; Raw material supply pipe
84; first column top distillate tube
86; First tower middle discharge pipe
88; first tower bottom bottom can pipe
90; Second tower supply pipe
92; Second tower top distillate
94; second tower bottom can outlet
96; Circulation supply pipe
98; Second tower middle discharge pipe
100; branch pipe
102; Raw material supply pipe
104; distillation tower supply pipe
106; Can bottom of distillation tower bottom
108; bottom of the dehydration distillation tower
110; Circulation supply pipe
112; quinoline supply pipe

Claims (16)

A method of adding a quinoline to a raw material mixture containing a dimethylamide compound and a carboxylic acid and distilling and purifying the mixture by a distillation column, wherein 1% by weight or more and 50% by weight or less of the total amount of dimethylamide compound taken out A method for distilling and separating a dimethylamide compound and a carboxylic acid, wherein the amide compound is distilled from the top of the distillation column, and the remainder is discharged from the “intermediate height position” of the distillation column as a further purified dimethylamide compound. . The distillation separation method according to claim 1, wherein the dimethylamide compound is represented by a composition formula (CH ₃ ) ₂ NCOR, and R is selected from the group consisting of H, CH ₃ , and CHCH ₂ . The distillation separation method according to claim 1, wherein the carboxylic acid is represented by a composition formula: C _n H _{2n + 1} COOH, and n is selected from 0, 1, 2. 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 is larger than that of the carboxylic acid in the raw material mixture. Dimethylamide compound and carboxylic acid are separated by distillation using three distillation columns comprising a first distillation column, a second distillation column, and a third distillation column (hereinafter referred to as the first column, the second column, and the 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 tower”.
(2) removing the liquid from the bottom of the “first tower” and supplying the bottom liquid from the “first tower” to the middle position of the “second tower”;
(3) A step of circulating the quinolines, taking out the quinolines from the bottom of the “second tower” and supplying the quinolines to the “first tower”.
(4) a step of distilling a mixed liquid of a dimethylamide compound and a carboxylic acid from the top of the “second tower” and supplying the mixed liquid to a middle position of the “third tower”;
(5) A liquid containing carboxylic acid as a main component is distilled from the top of the “third tower”, and a liquid in which a dimethylamide compound remains is removed from the bottom of the “third tower”. Supplying the bottom bottom effluent to the “first tower”;
(6) 1% by weight or more and 50% by weight or less of the total amount of dimethylamide compound extracted is distilled off from the top of the “first column”, and the remainder is further purified as a dimethylamide compound “middle” The distillation separation method according to any one of claims 1 to 6, comprising a step of extracting the liquid from a "height position". A method for distilling and separating a dimethylamide compound and a carboxylic acid using two distillation towers consisting of "first tower" and "second tower",
(1) supplying a dimethylamide compound and a carboxylic acid raw material mixed solution and quinolines to the “first tower”;
(2) A step of removing the liquid from the bottom of the “first tower” and supplying the bottom liquid of the “first tower” to the middle position of the “second tower”.
(3) A step of taking out quinolines from the bottom of the “second tower” and supplying them to the “first tower”, and circulatingly 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 mixed liquid of the dimethylamide compound from the intermediate height position of the “second tower” and supplying it to the “first tower”.
(6) 1% by weight or more and 50% by weight or less of the total amount of dimethylamide compound extracted is distilled from the top of the “first tower”, and the remainder is further refined as a purified dimethylamide compound at an intermediate height of the “first tower”. The distillation separation method according to any one of claims 1 to 6, comprising a step of extracting the liquid from the vertical position. The step of removing quinolines from the bottom of the “second tower”,
The method includes a step of diverging and taking out an amount of half or less of the bottoms from the bottom of the “second column”, and a step of separating and removing impurities having a high boiling point contained in the quinolines by distilling the liquid. Alternatively, the distillation separation method according to claim 8. further,
A mixed solution of a dimethylamide compound and 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. Water is distilled from the top, and from the bottom of the "dehydration distillation tower", the dehydrated liquid is taken out and supplied to the distillation tower as a raw material mixture;
The distillation separation method according to any one of claims 7 to 9, further comprising a step of supplying a distillate distilled from the top of the "first column" to the "dehydration distillation column". Furthermore, the distillation separation method of Claim 10 including the process of supplying the liquid which makes the main component the water distilled from the "dehydration distillation tower" tower top part 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 and quinolines to the "first column"
A "first tower" tower bottom bottom discharge pipe provided at the bottom of the "first tower" for discharging the "first tower"bottoms;
In order to supply the effluent from the “first tower” to the “second tower”, the “first tower” is connected to the bottom bottom take-out pipe and is provided at the “second tower” in the middle position. Two towers "supply pipe,
A "second tower" tower bottom cannula pipe provided at the bottom of the "second tower" to take out quinolines;
A quinoline circulation supply pipe for supplying the effluent of the “second tower” to the “first tower”;
A "second tower" tower top distillation pipe provided at the top of the "second tower" and for distilling a mixed liquid of a dimethylamide compound and a carboxylic acid;
A “third tower” supply pipe provided in the “third tower” for supplying the “second tower” distillate to the “third tower”;
A "third tower" tower top distillation pipe provided at the top of the "third tower" and taking out a fraction mainly composed of carboxylic acid from the top of the "third tower"tower;
A "third tower" bottom bottom discharge pipe which is provided at the bottom of the "third tower" and from which the "third tower" bottoms in which the dimethylamide compound remains from the bottom of the "third tower" ,
A "first tower" supply pipe for supplying the "third tower" bottoms to the "first tower",
An apparatus for separating dimethylamide compound and carboxylic acid by distillation,
And,
Of the total amount of the purified dimethylamide compound, 1% by weight or more and 50% by weight or less are distilled from the top of the “first tower” column, and the remainder is further refined as a purified dimethylamide compound at an intermediate height of the “first column”. A distillation separation device that can be taken out from the 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 quinolines to the “first column”;
A “first tower” tower bottom bottom discharge pipe for discharging the bottoms from the “first tower” tower bottom;
A “second tower” supply pipe for supplying the bottoms to the middle stage of the “second tower”;
A "second tower" tower bottom can take out quinolines from the "second tower" tower bottom;
A quinoline circulation supply pipe connected to the "first tower supply pipe" and circulatingly supplying the effluent from the "second tower" to the "first tower";
A “second tower” tower top distillation pipe for removing a fraction mainly composed of carboxylic acid from the “second tower” tower top;
A “second tower” intermediate discharge pipe for extracting the remaining mixed liquid of the dimethylamide compound from an intermediate height position of the “second tower”;
The “second tower” middle discharge pipe is connected to the “first tower supply pipe”.
An apparatus for separating dimethylamide compound and carboxylic acid by distillation,
And,
Of the total amount of dimethylamide compound taken out, 1 to 50% by weight is distilled from the top of the “first tower” column, and the remainder is further refined as a dimethylamide compound that is an intermediate high in the “first column”. A distillation separation device that can be taken out from the position. Furthermore, a branch pipe that branches from the bottom bottom can discharge pipe of the “second tower” and supplies an amount of less than half of the bottom liquid to the quinoline recovery tower,
and,
The distillation separation apparatus according to claim 12 or 13, further comprising a quinoline recovery tower for distilling the liquid to separate and remove impurities having a high boiling point contained in the quinolines. further,
A “hydrolysis reactor” for circulating 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 the raw material liquid from the “hydrolysis reactor” to the “dehydration distillation column”;
"Dehydration distillation tower" that distills the water contained in the raw material liquid from the top of the distillation tower,
"First tower" raw material provided at the bottom of the "dehydration distillation tower", for removing the dehydrated liquid obtained at the bottom of the "dehydration distillation tower" and supplying the bottoms as a raw material mixture A "dehydration distillation column" can discharge pipe connected to the supply pipe, a supply pipe for supplying the liquid distilled from the top of the "first tower" tower to the "hydrolysis reactor",
The distillation separation device according to any one of claims 12 to 14, comprising: A water circulation supply pipe for supplying a liquid mainly composed of water distilled 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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