JPS5953458A - Purification and recovery of methacrylonitrile - Google Patents

Abstract

PURPOSE:To obtain high-purity methacrylonitrile from the ammoxidation reaction product containing methacrolein and cyanic acid, economically in an industrial scale, by feeding the fraction distilled out under reduced pressure to the column to separate the low-boiling component. CONSTITUTION:The ammoxidation reaction product composed mainly of methacrylonitrile (abbreviated as MAN) and containing methacrolein and cyanic acid is absorbed with water, and the recovered MAN is distilled in the cyanic acid removing column 4a, the dehydration column 4b, the separation column for low-boiling component 6, and the product column 7 to recover the purified MAN. In the above process, the bottom liquid of the dehydration column 4b is introduced into the distillation column having reduced pressure, and the distillate from the column top is fed to the low-boiling component separation column 6 to obtain purified MAN. As an alternative method, the distillation in the dehydration column 4b is carried out under reduced pressure, and the gaseous distillate extracted from the bottom of the column is fed to the low-boiling separation column 6. EFFECT:The column bottom temperature can be lowered by the vacuum distillation to lower the decomposition rate of cyanhydrin and to suppress the contamination with the decomposed product. Cyanhydrin can be removed easily because the compound is discharged as a vapor phase.

Description

【発明の詳細な説明】 この発明はメククリロニトリル（以下、ＭＡＮと略称す
る）の精製回収方法、さらに詳しくはインブチレンある
いはターシャリ−ブチルアルコール等のアンモキシデー
ジョン反応物から製品Ｍ　ＡＮ　ｆ：鞘Σ（゛１回収す
る方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for purifying and recovering meccrylonitrile (hereinafter abbreviated as MAN), and more specifically, a method for purifying and recovering meccrylonitrile (hereinafter abbreviated as MAN), and more specifically, a method for purifying and recovering meccrylonitrile (hereinafter abbreviated as MAN), and more specifically, purifying and recovering the product MAN f: Regarding the method of collecting the sheath Σ(゛1).

ＭＡＮはイソブチレン等とアンモニアおよび酸素との気
相’ｊ′３：触反応、すなわちアンモキシデ　ジョン反
応により生成する。この反応生成物はＭ　Ａ　Ｎを主体
として、アセトニトリル、メタクロレイン、Ｔｉ’ｒ＋
Ｌ　アクリロニトリル、インブチロニトリル等を含有す
る１、これら副生物のうち、メタクロレインと′＃酸と
は結合して不安定な高沸点縮合物であるメタクロレイン
シアンヒドリン（ＮＩＢ　点９５°に　１３１１１ｊｉ
　）となる。従って反応生成物を蒸留して製品ＭＡ、Ｎ
を得ようとすると、蒸留分ぬＩＬの工程においてメタク
ロレインシアンヒドリンを生成し、これが後段の蒸留に
際し再びメタクロレインと青酸とに分解し留出液中に混
入し、Ｍ　Ａ　Ｎの純度を低下せしめ、高純度の製品が
イ０られなかった。MAN is produced by a gas phase catalytic reaction, that is, an ammoxide reaction, between isobutylene, etc., ammonia and oxygen. This reaction product mainly consists of M A N, acetonitrile, methacrolein, Ti'r+
L Contains acrylonitrile, imbutyronitrile, etc. 1. Among these by-products, methacrolein and '# acid combine to form an unstable high-boiling condensate, methacrolein cyanohydrin (NIB point 95°). 13111ji
). Therefore, the reaction products are distilled to produce products MA, N
When attempting to obtain MAN, methacrolein cyanohydrin is produced in the IL process without distillation, and this decomposes into methacrolein and hydrocyanic acid again in the subsequent distillation and is mixed into the distillate, reducing the purity of MAN. This caused a high purity product to be lost.

ＭＡＮの精製プロセスはアクリロニトリルのプロセスに
卑じ行なわれ、その−例は２８１図に示すごとくである
。吸収水に吸収せしめたＭＡＮを主成分とするアンモキ
シデージョン反応物は回収塔１において溶媒水とともに
抽出蒸留を行ない、塔頂蒸気はへ・を縮部２で凝縮され
、油水分雑器３で分離された油層はＭＡＮのほか、メタ
クロレイン、青酸、インブチロニトリル等の不純物およ
び飽和溶解量の水分を含んだ回収液となる。この回収液
は脱ｆ酸・水塔４の上部の脱Ｔ酸塔４ａの中段にフィー
ドし、塔頂から青酸を主体とする低沸成分を分離し、塔
底抜出し液を油水分離器５で水層と有機層とを分離後、
有機層を下部の脱水塔４ｂの上段にフィードする。脱水
塔４ｂの搭頂液は脱宵酸塔４ａの塔底にリターンし、塔
底液は抜出して低沸分離塔６の中段にフィードする。低
沸分＾１を塔６において、塔頂から低沸物を除去し、塔
底液を抜出して製品塔７にフィードし、微量の低沸物お
よび高沸物をそれぞれ塔頂、塔底から除去し製品Ｍ　Ａ
　Ｎをライン８から取得する。The MAN purification process is similar to that of acrylonitrile, an example of which is shown in Figure 281. The ammoxidation reaction product mainly composed of MAN absorbed in the absorption water is subjected to extractive distillation together with solvent water in the recovery column 1, and the vapor at the top of the column is condensed in the condensation section 2. The separated oil layer becomes a recovered liquid containing MAN, impurities such as methacrolein, hydrocyanic acid, and imbutyronitrile, and a saturated amount of water. This recovered liquid is fed to the middle stage of the T-deoxidation tower 4a located at the upper part of the deff-acid/water tower 4, and low-boiling components mainly consisting of hydrocyanic acid are separated from the top of the tower. After separating the layers and the organic layer,
The organic layer is fed to the upper stage of the lower dehydration tower 4b. The top liquid of the dehydration tower 4b is returned to the bottom of the dehydration tower 4a, and the bottom liquid is extracted and fed to the middle stage of the low-boiling separation tower 6. The low-boiling fraction ^1 is transferred to the column 6, where the low-boiling matter is removed from the top of the column, the bottom liquid is taken out and fed to the product column 7, and trace amounts of low-boiling matter and high-boiling matter are removed from the top and the bottom of the column, respectively. Removed product M A
Get N from line 8.

ところが、このプロセスにおいて、メタクロレインと青
酸とは一部がメタクロレインシアンヒドリンとなり、脱
青酸・水塔４および低沸分離塔６において除去できず、
塔底液に混入して製品塔７に入る。このメタクロレイン
シアンヒドリンは製品塔においてＭびメタクロレインと
’ｆ７酸に分解し製品ＭＡＮに混入して純度を低下せし
めた。なお、アクリロニトリル製造時に副生するアクロ
レインに比較し、メタクリロニトリル製造時のメタクロ
レインが１行に問題になる理由は、メタクロレインはア
クロレインに比べ、副生廿が多大である上に、水利反応
や重合反応が起りにくいため、メタクロレインが消滅せ
ずプロセス内に高儂度のまま存在するためでを）る。However, in this process, a part of methacrolein and hydrocyanic acid becomes methacrolein cyanohydrin, which cannot be removed in the hydrocyanic acid removal/water column 4 and the low boiling point separation column 6.
It mixes with the bottom liquid and enters the product column 7. This methacrolein cyanohydrin was decomposed into M, methacrolein and 'f7 acid in the product column and mixed into the product MAN, reducing its purity. The reason why methacrolein during the production of methacrylonitrile is more problematic than acrolein, which is produced as a by-product during the production of acrylonitrile, is that methacrolein produces more by-products than acrolein, and it also This is because methacrolein does not disappear and remains at a high degree in the process because polymerization reactions are difficult to occur.

この問題を力了決するためて、従来いくつかの提案がな
されている。Several proposals have been made to resolve this issue.

例えば、特公昭５０−２３０１７号公報には回収塔の中
段側流として青酸およびカルボニル化合物を除去し、後
段の蒸留プロセスにメタクロレインシアンヒドリンを持
込ませない１Ｐ案がある。しかし、低沸点のＷ　酸を回
収塔サイドから全量抜出すプロセスで、製品品質を確保
するためｌｌ５）５、スチーム消費１１が犬となり、径
が大きな蒸留塔が必要となり設備費の負担が増大する。For example, in Japanese Patent Publication No. 50-23017, there is a 1P plan in which hydrocyanic acid and carbonyl compounds are removed as a middle side stream of the recovery column, and methacrolein cyanohydrin is not brought into the subsequent distillation process. However, in the process of extracting the entire amount of low-boiling point W acid from the recovery column side, in order to ensure product quality, steam consumption11 becomes a problem, and a distillation column with a large diameter is required, increasing the equipment cost. .

さらに青酸を利用する場合は不純物を分離するためスト
リッピングポットの段数を増すか、スチーム消費Ｊ１１
をさらに増大する必要がある。Furthermore, when using hydrocyanic acid, the number of stripping pots must be increased to separate impurities, or steam consumption J11
needs to be further increased.

また、シアンヒドリンを安定化して分解によるアクロレ
イン痘ｊおよび青酸の製品中への混入を防止するため、
安定剤としてシュウ酸（特公昭３９−１０１１２号）、
スルファミン酸または酸性硫安（％公１１（３３９−２
８３１６号）　　、　、（ル；ｈ７Ｑｉたけ芳香族スル
ホン酸を用いる提案がある。しかし、この方法はシアン
ヒドリン含１．１．が少ない場合には有効であるが、含
−１７Ｙが多い１１５合、特に連続蒸留を行なう場合は
シアンヒドリンが蓄積されて含「１′Ｃが多くなり、製
品純度を向上せしめる効果は低い。In addition, in order to stabilize cyanohydrin and prevent acroleinpox and cyanide from being mixed into the product due to decomposition,
Oxalic acid (Special Publication No. 39-10112) as a stabilizer,
Sulfamic acid or acidic ammonium sulfate (% 11 (339-2
There is a proposal to use aromatic sulfonic acids (No. 8316), , (Ru; h7Qi). However, this method is effective when the 1.1. When continuous distillation is carried out, cyanohydrin is accumulated and 1'C content increases, and the effect of improving product purity is low.

特公昭４３−１８１２６号には、第１工程で票品添加し
、シアンヒドリンを分解し、アクロレイン類およびＶ？
酸を蒸留分離し、第２工程で薬品を添加し残存するシア
ンヒドリンを安定化しシアンヒドリンを蒸留分ＧＩ有す
る提案もある。この方法は回分蒸留においてシアンヒド
リンがい縮されない段階では有効であるが、連続蒸留を
行なう場合や回分蒸留においてもシアンヒドリンが蓄積
されて１３た・１′５合には、公知の無（、，’：　ｎ
′２あるいけ有様酸添加１１１：を増大する心安があり
、これら「（２の処理お゛よび装置オｊり′ｊに問題を
生じる１７本ジし３明渚らの検ｎ−Ｊによると、連続ｉ
、；昌）ｆにおいて効−！：！：をＭげるためにはシア
ンヒドリンｄ１°（度が上がらないように６′）相部を
多量に抜き出す必裁かシノリ、糸−’Ｌ　（ｊＦ的な方
法でＶゴない。In Japanese Patent Publication No. 43-18126, in the first step, a component is added to decompose cyanohydrin, and acrolein and V?
There is also a proposal to separate the acid by distillation and stabilize the remaining cyanohydrin by adding a chemical in the second step to obtain the distilled GI of cyanohydrin. This method is effective in the stage where cyanohydrin is not condensed in batch distillation, but when cyanohydrin is accumulated even in continuous distillation or batch distillation, there is no known problem (,,': n
There is a sense of security in increasing the number of acid additions (111) and these (17) which may cause problems in the processing and equipment used in (2). and continuous i
,;Chang) Effective at f! :! : In order to increase M, it is necessary to extract a large amount of cyanohydrin d1° (6' to avoid increasing the degree), or thread-'L (V cannot be obtained using the jF method).

以−［二述べたごとく、今までメタクロレインおよびＹ
Ｊ′酸を含イコーシたイ１１．メタクロニ２トリルから
高純度の製品メククリロニトリルを取イ：Ｉする１柴的
に完成された技術は見当らない。[As mentioned above, methacrolein and Y
11. Contains J′ acid. There is no known technology that has been perfected to obtain the highly purified product meccrylonitrile from methachronitrile.

この発明に、」二記石１１責に２゛ンみなされたもので
、その目的は、メタクロレイン、丁Ｊ′酸のン昆入ＪＸ
、が′４祖めて少なく、高品質のＭ　Ａ　Ｎを取イ：）
シ得る精製ｌ状法をＷ≦：ｆするにある。）その要旨は
、Ｍ　Ａ　Ｎを主成分としメタクロレイン、ｉ’ｒ　ｒ
ｆを含有するアンモキシデージョン反応物を水を溶媒と
して吸収・回収し、脱Ｖｌｉ′酸塔、脱水ノ１ハ低沸分
ｔｅｌ塔および製品ｉｕにおいで蒸留し製品ＭＡＮを取
得する精製回収プロセスにおいて、脱水塔塔底液を減圧
した蒸留塔に導き蒸留し塔頂からの留出物を、あるいは
脱水塔の蒸留を減圧下で行ないその塔底部から抜出した
ガス層の留出物を低沸分６１を塔にフィードすることを
特徴とするＭＡＮの精製回収方法である。In this invention, the purpose of this invention is to contain methacrolein, chloride acid, and JX.
, there are very few people in the 4th generation, and we have high quality M A N :)
The purification method for obtaining this is based on W≦:f. ) The gist is that M A N is the main component, methacrolein, i'r r
A purification and recovery process in which the ammoxidation reaction product containing f is absorbed and recovered using water as a solvent, and distilled in a Vli' removal tower, a dehydration step, a low boiling point tel tower, and a product iu to obtain a product MAN. In the process, the bottom liquid of the dehydration tower is introduced into a distillation column under reduced pressure and distilled, and the distillate from the top of the tower is distilled, or the distillate of the gas layer extracted from the bottom of the dehydration tower after distillation is carried out under reduced pressure. This is a method for purifying and recovering MAN, which is characterized by feeding a fraction 61 to a column.

第２図はこの精製回収方法を適用したプロセスの一例で
ある。このプロセスは脱Ｗ酸・水塔４に付帯してシアン
ヒドリン除去塔９が設けてあり１、脱水塔４ｂの塔底液
はこの除去塔９において減圧蒸留され、塔頂蒸気は？す
を縮部ｌＯでδを縮し留出液を低沸分離塔６にフィード
し、塔底液は塔底ライン１１を通り回収塔１にリターン
される。低沸分離塔６の塔底液は製品塔７にフィードし
、ライン８から製品Ｍ　Ａ　Ｎを液払出して取得し、塔
底液は一部ブローダウンをとりつつ回収塔１にリターン
される。FIG. 2 is an example of a process to which this purification and recovery method is applied. In this process, a cyanohydrin removal column 9 is provided attached to the dehydrating acid/water column 4. The bottom liquid of the dehydration column 4b is distilled under reduced pressure in this removal column 9, and the top vapor is ? The δ is condensed in the condensation section 1O, and the distillate is fed to the low boiling point separation column 6, and the bottom liquid is returned to the recovery column 1 through the bottom line 11. The bottom liquid of the low-boiling separation column 6 is fed to the product column 7, and the product M A N is discharged from the line 8 to be obtained, and the bottom liquid is returned to the recovery column 1 while being partially blown down.

第３図もこのｆ？？’？！回収方法を適用したプロセス
の一例である。このプロセスでは、脱水塔４ｂは脱青酸
塔４ａと別体をなし、脱青酸塔４ａの塔頂から青酸を分
＋：、′Ｃいり１け（液を油水分印部５で水層を分１’
；：Ａ　Ｌ、油Ｉニアを波圧下脱水’！Ｆ　４１）の上
段にフィードし減圧下蒸留する。」１シ頂１）７出液は
油水分離器５に戻し、’ｊＦ　ｈ’（６１５（’）　カ
ス／；ｊ７　ｆ抜出し、（−（７）　＄６縮液を塔底ガ
スライン１２を経て低沸分２Ｖ塔６にフィードし、塔底
液は塔底液ライン１３を経て回収搭工にリターンされる
。このａＥ　ｆｉｉｆ液１１＝、ｊｉ２図のプロセスと
四柱に低ｆｊｌ；分子ａ塔６２次いで製品塔７にて処理
し製品ＭＡＮを取得する。Figure 3 is also this f? ? '? ! This is an example of a process to which the collection method is applied. In this process, the dehydration tower 4b is separate from the prussic acid removal tower 4a, and prussic acid is separated from the top of the prussic acid removal tower 4a. 1'
;:A L, oil I near is dehydrated under wave pressure'! Feed into the upper stage of F41) and distill under reduced pressure. 1) The top 1) 7 output liquid is returned to the oil-water separator 5, 'jF h' (615 (') dregs/;j7 f is extracted, and (-(7) The low-boiling content is fed to the 2V column 6, and the bottom liquid is returned to the recovery tower via the bottom liquid line 13. Next, it is processed in a product tower 7 to obtain a product MAN.

この発明に係わる精製回収方法は以上の４ニア１；成で
あシ、シアンヒドリン除去」ｂあるいは脱水塔において
減圧下蒸留することによって、塔底温度を下げてシアン
ヒドリンの分解速度を低下せしめて、その分解を抑制し
分解物の混入を低減し、かつガス層として取出すことに
より、高沸物であるシアンヒドリンの高度の除去を可能
とする。また、シアンヒドリン除去塔、あるいは脱水塔
の減圧度は４００〜１００間Ｉｉｇ、塔底温度として８
０〜４０℃が好適である。８０°Ｃ以上ではシアンヒド
リンの分解抑制効果が充分でなく、１００　ｔｎ、ｍ　
ＩＩ、！ｉ’未満では設備費および比例弁のコストが増
大する割には分解抑制効果を著しく高める効果が認めら
れず好ましくない。The purification and recovery method according to the present invention includes the above-mentioned 4-Near 1: Removal of cyanohydrin, or distillation under reduced pressure in a dehydration tower to lower the bottom temperature and reduce the decomposition rate of cyanohydrin. By suppressing decomposition, reducing contamination of decomposed products, and extracting it as a gas layer, it is possible to remove cyanohydrin, which is a high-boiling substance, to a high degree. In addition, the pressure reduction degree of the cyanohydrin removal tower or dehydration tower is between 400 and 100 Iig, and the tower bottom temperature is 8
A temperature of 0 to 40°C is suitable. At temperatures above 80°C, the effect of suppressing the decomposition of cyanohydrin is not sufficient, and the temperature of 100 tn, m
II,! If it is less than i', the equipment cost and the cost of the proportional valve increase, but the effect of significantly increasing the decomposition suppressing effect is not observed, which is not preferable.

実ｌイＩＥ２す１ 第２図のイＩＩ＋′製回収グロスセに従い、メククリロ
ニトリルを主成分とし、それにメタクロレイン、青酸、
メククロレインシアンヒドリン及び飽和溶解変分の水分
を含有した液を、脱ＹＩ酸・脱水工ｉにフィードし、塔
底より青白λと水分〆゛↓度を低減したオ１１メタクリ
ロニトリルをイ４Ｊだ。次いで２００　ｍｌのフラスコ
全装着したシアンヒドリン除去塔（減圧単蒸留塔）の塔
底へとの粗メタクリロニトリルを２００　ｉ／′Ｉｌｖ
”でフィードし、塔頂圧力１９８朋Ｈｇ　、塔底液温度
６０℃にて塔頂より１９７．６ｇ　／　ＩＩｒ＋　’６
底よＪ）　２．４　ｆ　／　Ｈｒで抜き出した。この塔
頂留出液を２７０　ｒｉＩＩｇの圧力下、内径３２φ。Practical IE2S1 According to the recovered grosses made by II+' in Figure 2, the main component is meccrylonitrile, plus methacrolein, cyanogenic acid,
The liquid containing water of mechcrolein cyanohydrin and the saturated dissolved fraction is fed to the YI deacidification/dehydration plant I, and from the bottom of the column, O11 methacrylonitrile with reduced blue-white λ and water content is extracted. It's I4J. Then, the crude methacrylonitrile was fed to the bottom of a cyanohydrin removal column (vacuum simple distillation column) equipped with a 200 ml flask at a rate of 200 i/'Ilv.
197.6g/IIr+'6
Bottom J) I pulled it out at 2.4 f/Hr. This tower top distillate was heated under a pressure of 270 riIIg with an inner diameter of 32φ.

わ１段７０段を有する低沸分離塔の４５段に１００９／
Ｈｒでフィードし塔底より９５　ｇ／Ｈｒで液相を抜き
出し、次いで、３５０　ｙｎｘ　ＨｆＩの圧力下、内径
３２φ、棚段５５段を有する製品塔の３０１２に８０．
９／ＩＩｒでフ・イードし、サイド’１Ｉｌ−抜き出し
に上り７７　、！７．／ｌｌｒテ製品Ｍ　Ａ　Ｎを取得
した　ラ１（１にシ゛Ｊ品ＭＡＮ及び途中プロセス７１
に中不純’ｌ′’ｌ　ｕ＞度を示した。1009/
The liquid phase was extracted from the bottom of the column at a rate of 95 g/Hr, and then, under a pressure of 350 ynx HfI, it was transferred to a product column 3012 having an inner diameter of 32φ and 55 plates.
Fed with 9/IIr, went up to the side '1Il-extract, 77,! 7. /lrte product M A N has been obtained.
It showed a degree of medium impurity.

衣ｌ　製品及びプロセス液中不純物Ｘ！＋−＞を単位は
ｗ　ｔ　ｐ　ｐｎ＋ 比較例−１ 実施例−１と同一の脱水塔々底抜き出し液をシアンヒド
リン除去塔を経由しないで低沸分子２塔ヘフイードし、
以下の工程を実施例−１と同一の蒸留塔を用い、同様な
条件にて運転し製品ＭＡＮを取得した。表２に得られた
製品ＭＡＮ及び途中プロセス液中不純物濃度を示した。Clothing I Impurities in products and process liquids +-> is the unit w t p pn+ Comparative Example-1 The same dehydration tower bottom extract as in Example-1 was fed to two low-boiling molecule towers without passing through the cyanohydrin removal tower,
The following steps were performed using the same distillation column as in Example-1 and operated under the same conditions to obtain the product MAN. Table 2 shows the obtained product MAN and the impurity concentration in the intermediate process liquid.

、 表２　製品及びプロセス液中不純物の度単位はｗｔｐｐ
ｍ 実施例２ 第３図に示しだプロセスに従い、メタクリロニトリルを
主成分とし、それにメタクロレイン、青酸、メタクロレ
インシアンヒドリン及び飽和溶解度分の水分を含有した
液を、内径２５φ、高さ４００間の脱１￥酸塔の中段に
４５０９　／Ｈｒでフィードし、塔頂より青酸を分１；
Ｉ　した塔底液を油水分陥部で水層を分ｎｆ＃　ｔ、、
油層を２００　ｕｒｎ　ＩＩ、９の圧力下、内径２５φ
、高さ３５０闘の脱水塔の上段に３７０　ｇ／Ｉｌｒ　
テフイードする。。, Table 2 The degree unit of impurities in product and process liquid is wtpp
m Example 2 According to the process shown in Fig. 3, a liquid containing methacrolein, hydrocyanic acid, methacrolein cyanohydrin, and water equivalent to the saturation solubility was prepared using a tube having an inner diameter of 25φ and a height of 400 mm. Feed 4509/Hr into the middle stage of the deoxidation tower, and add 1 minute of hydrocyanic acid from the top of the tower.
Separate the aqueous layer from the bottom liquid in the oil-water depression section nf # t,,
Oil layer 200 urn II, under pressure of 9, inner diameter 25φ
, 370 g/Ilr on the upper stage of a dehydration tower with a height of 350 m
Tefued. .

脱水塔々Ｊ１２留出液は油水分Ｐｒ’ｌＡ器へ戻し、塔
底部よりガス層３５７９　／′Ｈｒで抜き出した。この
凝縮液を、実施例−１と同様に、まず低沸分離塔次いで
製品塔にて処理し、製品ＭＡＮを取得した。The J12 distillate from the dehydration tower was returned to the oil/water Pr'lA vessel and extracted from the bottom of the tower at a gas layer of 3579/'Hr. This condensate was first treated in a low-boiling separation column and then in a product column in the same manner as in Example-1 to obtain a product MAN.

表３に製品ＭＡＮ及び途中プロセス液中不純物の度を示
した。Table 3 shows the product MAN and the degree of impurities in the process liquid.

表３　製品及びプロセス液中不純物濃度ｔｐｐｍ 比較例−２ 実施例−２と同一の脱性ｒり塔フィード液を用い當圧下
、脱性酸、脱水塔を運転し、脱水塔々底よＪノミ皮接き
出しにＪり粗ＭＡＮを得だ。次いで、このｇ７１　Ｍ　
Ａ　Ｎを実カー例−１と同様に、甘ず低沸分離塔次いで
製品塔にて処即し、製品Ｍ　Ａ　Ｎを取イ（）シた。表
４に製品Ｍ　Ａ　Ｎ及び途中プロセス液中不純物り度を
示しだ７１ 、Ｈｊ、３４　　：ｊＨｑ品及びプロセス液中不紳１物
１宸度Table 3 Impurity concentration tppm in product and process liquid Comparative Example-2 Using the same dehydrating column feed liquid as in Example-2, operating the dehydrating acid and dehydrating column under the same pressure, I got a J rough MAN on the skin. Then, this g71 M
AN was processed in the sweet and low-boiling separation column and then in the product column in the same manner as in Actual Car Example-1, and the product MAN was removed. Table 4 shows the product M A N and the degree of impurity in the process liquid.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は従来のＭＡＮのＡ′ｎ製回収プロセスのフロー
シート、第２図、第３図はそれぞれこの発明の精製回収
方法を応用したプロセスのフローシートである。 １・・回収塔、２・・凝縮器、３・・油水分ｇ器、４・
・脱骨ｒｉ２・水塔、４ａ・・脱性酸浴、４ｂ・・脱水
塔、５・・油水分１’＋ＩＣ器、６・・低佛分ｎ：１塔
、７・・製品」１°シ、８・・製品Ｍ　Ａ　Ｎ取出しラ
イン、 ９・・シアンヒドリン除去塔、１０・・凝＃ｌ’ｌ’ｊ
　：：Ｆｉ、１１・・塔底ライン、１２・・塔底ガスラ
イン、１３・・塔底液ジイン。FIG. 1 is a flow sheet of a conventional MAN A'n recovery process, and FIGS. 2 and 3 are flow sheets of processes to which the purification and recovery method of the present invention is applied. 1. Recovery tower, 2. Condenser, 3. Oil/moisture girder, 4.
・Deboning ri 2・Water tower, 4a... Deoxidation acid bath, 4b... Dehydration tower, 5... Oil/water 1' + IC device, 6... Low fraction n: 1 tower, 7... Product" 1° cylinder , 8... Product M A N take-out line, 9... Cyanohydrin removal tower, 10... Coagulation #l'l'j
::Fi, 11... Tower bottom line, 12... Tower bottom gas line, 13... Tower bottom liquid diine.

Claims (1)

【特許請求の範囲】[Claims] （１）　　メタクリロニトリルを主成分としメタクロレ
イン、青酸を含有するアンモキシデージョン反応物を水
を溶媒として吸収、回収し、脱青酸塔、脱水塔、低沸分
離塔および製品基において蒸留し製品メタクリロニトリ
ルを取得するメタクリロニトリルのＦＳ７！Ｊ！回収プ
ロセスにおいて、脱水塔搭底液を減圧した蒸留塔に導き
蒸留し塔頂からの留出物をあるいは脱水塔の蒸留を減圧
下で行ないその塔底部から抜出したガス層の留出物を低
沸分離塔にフィードすることを特徴とするメタクリロニ
トリルの精製回収方法。(1) An ammoxidation reaction product containing methacrolein and hydrocyanic acid as a main component is absorbed and recovered using water as a solvent, and then distilled in a prussic acid removal tower, a dehydration tower, a low-boiling separation tower, and a product group. FS7 of methacrylonitrile to obtain the product methacrylonitrile! J! In the recovery process, the bottom liquid of the dehydration tower is led to a distillation tower under reduced pressure and distilled, and the distillate from the top of the tower is distilled, or the distillate from the gas layer extracted from the bottom of the tower after distillation from the dehydration tower is reduced. A method for purifying and recovering methacrylonitrile, which comprises feeding the methacrylonitrile to a boiling separation column.