JP3804082B2 - Purification method of aniline - Google Patents

Description

【０００４】
粗製アニリンを蒸留して得られる精製アニリンには成分は定かでないが、着色性不純物が混入し、製品アニリンが着色する問題があった。これを解決するために、粗製アニリンに固形の苛性ソーダを添加して、又は粗製アニリンを固形の苛性ソーダと接触後、蒸留することによって着色しないアニリンを得る方法が知られている（特開昭４９−３５３４１号）。
しかしながら、この方法は高沸廃油の粘性が高くなり、取扱いが困難であること、また高濃度の苛性ソーダを高温（約１００℃〜１５０℃）で扱うために、蒸留塔の腐食の問題を有している。
【０００５】
一方、アニリン中の不純物として、フェノールは３０ｐｐｍ以下、高沸点分は０．１％以下にすることが望まれている。これらの濃度は JIS K 4109 に規定されている。
フェノールの沸点（１８１．４℃）とアニリンの沸点（１８４．４℃）は極めて近接しており、沸点付近の揮発度も１．０６であり、これらの分離を通常の蒸留塔で行うとエネルギー消費が多くなり、経済的ではない。
【０００６】
本発明者はかかる課題を解決するために鋭意検討した結果、フェノール類を含有するアニリン溶液を希薄アルカリ水溶液と接触させることによって、高沸廃油の取扱いや、蒸留塔の腐食を問題にすることなく、無着色でフェノールが３０ｐｐｍ以下のアニリンが容易に得られることを見出し、本発明を完成した。
【０００７】
【課題を解決するための手段】
すなわち本発明は下記のとおりである。
（１）ニトロベンゼンの水添反応によって得られる反応生成物であるフェノール類を含有するアニリン溶液を希薄アルカリ水溶液と接触させ、接触させて得られる水層中のアルカリ濃度が０．１〜０．７重量％とし、油水分離した後、油相を蒸留することを特徴とするアニリンの精製方法。
（２）含有するフェノール類に対するアルカリのモル比が３〜５００である前記〔１〕項記載の精製方法。
（３）アルカリが水酸化ナトリウム又は水酸化カリウムである前記〔１〕項又は〔２〕項記載の精製方法。
【０００８】
本発明で用いるアルカリとしては、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸水素ナトリウム、炭酸カリウム、炭酸水素カリウムが挙げられる。反応性、分液性等の点から水酸化ナトリウム又は水酸化カリウムが好ましく用いられる。
【０００９】
フェノール類を含有するアニリン溶液に所定濃度のアルカリ水溶液を加えて混合しフェノールを除去する。アニリン溶液がニトロベンゼンを水添して得られる水相を含む反応液の場合には、アルカリ水溶液を添加後の水相のアルカリ濃度が所定濃度になるようアルカリ水溶液の濃度又は量を調整する。勿論、反応液から水相を分離して、所定濃度のアルカリ水溶液を混合しても良い。
【００１０】
アルカリ水溶液を添加後の水相のアルカリ濃度は０．１wt％〜０．７wt％、好ましくは０．１５wt％〜０．６５wt％である。０．１wt％より低いとフェノール類を十分に除去するために多量のアルカリ水溶液を必要とし、経済的でない。また０．７wt％より高いと油相と水相の上下が反転したり、分液性が悪くなるので好ましくない。
【００１１】
またアルカリとフェノール類とのモル比は、アニリン溶液中のフェノール類の濃度にもよるが、３〜５００、好ましくは１０〜２００であり、３より低いと十分なフェノールの除去ができず、５００より多いとアルカリの量が多くなり、経済的ではない。
【００１２】
アニリン溶液（油相部分）とアルカリ水溶液（水相部分）との混合時間は、アニリン溶液とアルカリ水溶液の接触が十分に行われさえすれば、特に制限されるものではない。
【００１３】
混合後、静置し、油水分離し、油相部分を、通常、圧力７０torr〜２００torr、温度１１０℃〜１４０℃で蒸留することによって、フェノールを３０ｐｐｍ以下（通常、殆ど含有せず）、着色のない精製アニリンが得られる。
【００１４】
この際、高沸廃油の粘性が、取扱いが困難になるほど高くなったり、アルカリによる腐食も殆ど起こらない。
【００１５】
本発明の方法は、連続法でも、回分法でも容易に実施可能である。
【００１６】
【発明の効果】
本発明の方法により、高沸廃油の取扱いや、蒸留塔の腐食を問題にすることなく、無着色でフェノールを殆ど含まないアニリンを容易に得ることができる。
【００１７】
【実施例】
以下、本発明を実施例で詳細に説明するが、本発明はこれに限定されるものではない。
実験例
２５〜２９０ｐｐｍのフェノールを含有するアニリン及び０．１５〜０．７０ｗｔ％の水酸化ナトリウム水溶液を分液漏斗にて５分間振とうし、常温で１００分間静置した後、アニリン中のフェノール濃度を測定した。条件及び結果を表２に示す。
【００１８】
【表２】

【００１９】
実施例１〜５、比較例１
ニトロベンゼンを水添して得られた反応生成液（油相部分のフェノール濃度：２０〜１００ｐｐｍ）の水相部分の水酸化ナトリウム濃度を所定濃度になるよう水酸化ナトリウム水溶液を加えて混合し、次いでデカンターで油水分離し、油相部分を蒸留して精製アニリンを得た。精製アニリン中のフェノール濃度は５ppm 以下であり、缶出液の高沸廃液の抜き出しは容易であり、蒸留塔の腐食も殆ど見られなかった。条件及び結果を表３に示す。
【００２０】
【表３】

[0001]
[Industrial application fields]
The present invention relates to a method for purifying aniline.
Specifically, the present invention relates to a method for removing phenols contained in aniline.
[0002]
[Prior art and problems to be solved by the invention]
Aniline is generally produced by hydrogenating nitrobenzene in the gas phase or liquid phase in the presence of a catalyst. In this reaction, by-products such as phenols are generated in addition to the target product.
When the reaction product is usually cooled and the aqueous phase portion is separated, for example, crude aniline (oil phase portion) having the composition shown in Table 1 is obtained. This crude aniline is distilled stepwise to obtain purified aniline.
[0003]
[Table 1]

[0004]
The components of purified aniline obtained by distilling crude aniline are not clear, but there is a problem that coloring impurities are mixed and product aniline is colored. In order to solve this, there is known a method for obtaining uncolored aniline by adding solid caustic soda to crude aniline or by bringing the crude aniline into contact with solid caustic soda and then distilling it (Japanese Patent Laid-Open No. 49-49). 35341).
However, this method has high viscosity of high boiling waste oil and is difficult to handle, and has a problem of corrosion of the distillation tower because high concentration caustic soda is handled at a high temperature (about 100 ° C. to 150 ° C.). ing.
[0005]
On the other hand, as impurities in aniline, phenol is desired to be 30 ppm or less, and high boiling point content is desired to be 0.1% or less. These concentrations are specified in JIS K 4109.
The boiling point of phenol (181.4 ° C.) and the boiling point of aniline (184.4 ° C.) are very close to each other, and the volatility near the boiling point is 1.06. Consumption is high and not economical.
[0006]
As a result of diligent investigations to solve such problems, the present inventor brought the aniline solution containing phenols into contact with a dilute alkaline aqueous solution without causing problems with handling of high boiling waste oil and corrosion of the distillation tower. It was found that aniline having no coloring and 30 ppm or less of phenol could be easily obtained, and the present invention was completed.
[0007]
[Means for Solving the Problems]
That is, the present invention is as follows.
(1) An aniline solution containing phenols, which is a reaction product obtained by a hydrogenation reaction of nitrobenzene, is brought into contact with a dilute alkaline aqueous solution, and the alkali concentration in the aqueous layer obtained by contacting is 0.1 to 0.7. A method for purifying aniline, characterized in that the oil phase is distilled after oil-water separation by weight .
( 2 ) The purification method according to the above [1], wherein the molar ratio of alkali to phenol contained is 3 to 500.
( 3 ) The purification method according to the above [1] or [2], wherein the alkali is sodium hydroxide or potassium hydroxide.
[0008]
Examples of the alkali used in the present invention include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate. Sodium hydroxide or potassium hydroxide is preferably used from the viewpoint of reactivity, liquid separation, and the like.
[0009]
An aqueous alkaline solution having a predetermined concentration is added to an aniline solution containing phenols and mixed to remove phenol. When the aniline solution is a reaction solution containing an aqueous phase obtained by hydrogenating nitrobenzene, the concentration or amount of the aqueous alkaline solution is adjusted so that the alkaline concentration of the aqueous phase after the addition of the aqueous alkaline solution becomes a predetermined concentration. Of course, the aqueous phase may be separated from the reaction solution and mixed with an aqueous alkali solution having a predetermined concentration.
[0010]
The alkali concentration of the aqueous phase after adding the aqueous alkali solution is 0.1 wt% to 0.7 wt%, preferably 0.15 wt% to 0.65 wt%. If it is lower than 0.1 wt%, a large amount of alkaline aqueous solution is required to sufficiently remove phenols, which is not economical. On the other hand, when the content is higher than 0.7 wt%, the oil phase and the aqueous phase are reversed upside down, and the liquid separation property is deteriorated.
[0011]
The molar ratio of alkali to phenol is 3 to 500, preferably 10 to 200, although it depends on the concentration of phenol in the aniline solution. If it is lower than 3, sufficient phenol cannot be removed. If it is higher, the amount of alkali increases, which is not economical.
[0012]
The mixing time of the aniline solution (oil phase part) and the alkaline aqueous solution (aqueous phase part) is not particularly limited as long as the aniline solution and the alkaline aqueous solution are sufficiently contacted.
[0013]
After mixing, the mixture is left to stand, separated into oil and water, and the oil phase is usually distilled at a pressure of 70 torr to 200 torr and a temperature of 110 ° C to 140 ° C, so that phenol is 30 ppm or less (usually hardly contained) and colored. No purified aniline is obtained.
[0014]
At this time, the viscosity of the high-boiling waste oil becomes so high that it becomes difficult to handle, and corrosion by alkali hardly occurs.
[0015]
The method of the present invention can be easily carried out by a continuous method or a batch method.
[0016]
【The invention's effect】
By the method of the present invention, it is possible to easily obtain an aniline which is colorless and hardly contains phenol, without causing problems of handling of high boiling waste oil and corrosion of a distillation tower.
[0017]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this.
Experimental Example 25 Aniline containing phenol of 290 to 290 ppm and 0.15 to 0.70 wt% sodium hydroxide aqueous solution were shaken in a separatory funnel for 5 minutes, allowed to stand at room temperature for 100 minutes, and then phenol in aniline. Concentration was measured. The conditions and results are shown in Table 2.
[0018]
[Table 2]

[0019]
Examples 1-5, Comparative Example 1
A sodium hydroxide aqueous solution is added and mixed so that the sodium hydroxide concentration in the aqueous phase portion of the reaction product obtained by hydrogenating nitrobenzene (phenol concentration in the oil phase portion: 20 to 100 ppm) becomes a predetermined concentration, and then Oil and water were separated using a decanter, and the oil phase was distilled to obtain purified aniline. The phenol concentration in the purified aniline was 5 ppm or less, and it was easy to remove the high boiling waste liquid from the bottoms, and the corrosion of the distillation tower was hardly observed. The conditions and results are shown in Table 3.
[0020]
[Table 3]

Claims (3)

An aniline solution containing phenols, which are reaction products obtained by hydrogenation of nitrobenzene, is brought into contact with a dilute alkaline aqueous solution, and the alkali concentration in the aqueous layer obtained by contact is 0.1 to 0.7% by weight. A method for purifying aniline, characterized in that after oil-water separation, the oil phase is distilled .   The purification method according to claim 1, wherein the molar ratio of alkali to phenol contained is 3 to 500. The purification method according to claim 1 or 2 , wherein the alkali is sodium hydroxide or potassium hydroxide.