JPS5852239A - Treatment of gas produced by oxidation reaction - Google Patents

Abstract

PURPOSE:To remove impurities from the gas produced by the vapor-phase catalytic reaction of methacrolein, and to prevent the formation of scum in the preparation of methacrylic acid by the condensation and extraction of the produced gas, by introducing the gas prior to condensation into a specific collecting apparatus. CONSTITUTION:Gas containing methacrylic acid and obtained by the vapor- phase catalytic oxidation reaction of methacrylein is condensed, and methacrylic acid is extracted from the condensation liquid with an organic solvent. Prior to the condensation, the gas is introduced into a collecting apparatus keeping the temperature of the collecting part of the apparatus above the dew point of said gas under the pressure in the collecting apparatus and below 250 deg.C to remove the impurities having high boiling point and high melting point from said gas. The deposition of solid impurities to the condenser can be prevented, and there is no necessity to solve the blocking problem, to use a specially designed column, and to prepare a means for removing the solid, etc. Since the solid impurities is taken out in a dry state, the methacrylic acid can be obtained without loss, and the waste can be conveniently incinerated and disposed.

Description

【発明の詳細な説明】 本発明は、メタクロレインを気、相接触酸化して得られ
るガスを冷却して碍たメタクリル酸水溶液を有機溶剤に
て抽出す゛る際二液の界面に発生するスカム（浮きかす
）の生成を防止する方法に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention deals with the scum ( The present invention relates to a method for preventing the formation of floating particles.

メタクロレインの気相酸化法によるメタクリル酸の製造
方法において、メタクリル酸水溶液からメタクリル酸を
取出すために先ず有機溶剤によって抽出する方法が一般
によく知られている。In a method for producing methacrylic acid by a gas phase oxidation method of methacrolein, a method is generally well known in which methacrylic acid is first extracted with an organic solvent in order to remove methacrylic acid from an aqueous methacrylic acid solution.

しかしこの抽出の際二液の界面にスカムが発生して抽出
塔内に滞留し、塔内部を汚したり二液分離の境界面に蓄
積したりしてついには抽出塔が運転不能になるという問
題が生ずる。このスカムの発生を防止するためにメタク
リル酸水溶液を活性炭或は吸着樹脂で処理する（特開昭
５Ｏ−５２０２１−）或はメタクリル酸水溶液をあらか
じめ溶剤と接触させて発生したスカムを除去した後抽出
塔へ送る（特開昭５６−１６４３８）或は同様に有機溶
剤と接触させてスカムを有機層へ移行させる（特開昭５
６−７９６３４）などの方法が行われている。However, during this extraction, scum is generated at the interface of the two liquids and remains in the extraction tower, polluting the inside of the tower and accumulating at the interface between the two liquids, eventually making the extraction tower inoperable. occurs. To prevent the generation of scum, the methacrylic acid aqueous solution is treated with activated carbon or adsorption resin (JP-A-5O-52021-), or the methacrylic acid aqueous solution is brought into contact with a solvent in advance to remove the generated scum, and then extracted. The scum is sent to a column (Japanese Patent Application Laid-Open No. 56-16438) or similarly brought into contact with an organic solvent to transfer the scum to an organic layer (Japanese Patent Application Laid-Open No. 56-16438).
6-79634) has been used.

しかし前者の方法はコスト高となり、後二者の方法はス
カムがメタクリル酸水溶液の酸濃度がうすぐなるに応じ
て更に析出して来るためいずれも充分な除去は出来ず、
抽出塔で次第にスカムが蓄積して来る欠点がある。However, the former method is costly, and the latter two methods cannot remove the scum sufficiently as the scum further precipitates as the acid concentration of the methacrylic acid aqueous solution decreases.
There is a drawback that scum gradually accumulates in the extraction tower.

又特開昭５２−４８６０９号においては反応ガス中に含
まれるカーボンタール状物質を高温の水で洗浄すること
により除去する方法が記載されている。Furthermore, JP-A-52-48609 describes a method for removing carbon tar-like substances contained in a reaction gas by washing with high-temperature water.

しかしこの方法では洗浄塔内での重合の危険性があり又
排出液中への目的物であるメタクリル酸のロスがさけら
れない。However, in this method, there is a risk of polymerization within the washing tower, and loss of the target methacrylic acid into the discharged liquid cannot be avoided.

又特開昭５５−１２７３４号においては反応−−△ 出ガスを極めて短時間（０，１秒好ましくは０．０１秒
）の間に冷却することによりスカムの発生を防止する方
法が記載されて贋るが、大型の実装置においてこのよう
な条件を実現することは極めて困難である。このように
上記方法はいづれも欠点があり充分満足出来る方法とは
云えない。Furthermore, JP-A-55-12734 describes a method for preventing the generation of scum by cooling the reaction gas in a very short period of time (0.1 seconds, preferably 0.01 seconds). However, it is extremely difficult to realize such conditions in a large-scale actual device. As described above, all of the above methods have drawbacks and cannot be said to be fully satisfactory methods.

本発明者らはスカム発生の根本的な防止策としてその発
生原因を種々検討した結果、驚くべきことには反応生成
ガス中に気体状で含まれ冷却時に固状で析出する高沸点
、高融点の不純物（以下固状不純物という）を選択的に
除去した後のガスでは、通常の方法で冷却、液化せしめ
た凝縮液を原料として抽出操作を行っても実質的にスカ
ムの発生が認められないという事実を見出し本発明を完
成するに到った。As a fundamental preventive measure against scum generation, the present inventors investigated various causes of scum generation and found that, surprisingly, scum is present in gaseous form in the reaction product gas and precipitates in solid form upon cooling. In the gas after selectively removing impurities (hereinafter referred to as solid impurities), virtually no scum is generated even if extraction operations are performed using condensate that has been cooled and liquefied in the usual manner as raw material. Having discovered this fact, we have completed the present invention.

即ち１本発明は、メタクロレインの気相接触酸化反応に
より得られるメタクリル酸を含有する反応生成ガスを凝
縮させ、得られる凝縮液から有機溶剤を用いてメタクリ
ル酸を抽出する方法において、該ガスを凝縮させる前に
捕集器内の捕集部分の温度を補集器内の圧力における該
ガスの露点以上２５０ｃ以下の温度に保った捕集器に導
き該ガス中に含有される高沸点、高融点の不純物を捕集
せしめた後凝縮器に導いて凝縮させることを特徴とする
酸化反応生成ガスの処理法に関するものである。Namely, the present invention provides a method for condensing a reaction product gas containing methacrylic acid obtained by a gas phase catalytic oxidation reaction of methacrolein, and extracting methacrylic acid from the resulting condensate using an organic solvent. Before condensing, the high boiling point, high The present invention relates to a method for treating an oxidation reaction product gas, which is characterized in that impurities at a melting point are collected and then introduced into a condenser to be condensed.

本発明の方法によるとスカムの生成が防止できる。この
理由については未だ完全に解明されていないが、恐らく
次の理由によるものと思われる。スカムとなる物質は、
詳細な構造は不明であるが分子量数百位を中心とする重
合物の混合物と考えられ、その性状からみて反応流出ガ
ス中に含まれているものではなく１反応流出ガスが前記
の固状不純物を伴って凝縮する際何らかの化学変化を受
けて生成するものと考えられ。According to the method of the present invention, the formation of scum can be prevented. Although the reason for this has not yet been completely elucidated, it is probably due to the following reason. The substances that become scum are
The detailed structure is unknown, but it is thought to be a mixture of polymers with a molecular weight of around several hundred. Judging from its properties, it is not contained in the reaction effluent gas, but rather the reaction effluent gas is the solid impurity mentioned above. It is thought that it is formed as a result of some kind of chemical change during condensation.

本発明によって固状不純物が除去された結果反応ガスが
凝縮する際スカム物質が生成されないのであろうと考え
られる。It is believed that as a result of the removal of solid impurities by the present invention, no scum material is produced when the reaction gas is condensed.

ここで云う流出ガス中に含まれる冷却時に固状で析出す
る高沸点、高融点の不純物とは１通常芳香族カルボン酸
類、芳香族アルデヒド類などを含み該流出ガスの露点Ｄ
ｌ上２５０ＣＪ：Ｊ下の温度において固体状の形状とな
り−、うるものを指す。The high boiling point and high melting point impurities contained in the outflow gas and precipitated in solid form during cooling are 1. Usually include aromatic carboxylic acids, aromatic aldehydes, etc., and the dew point D of the outflow gas is
250CJ: refers to something that becomes solid at temperatures below 250CJ and is wet.

該流出ガスから上記固状不純物を除去するに際し、その
操作温度（該流出ガスの冷却温度）は該ガスの操作圧力
での露点以上であることが必要である。When removing the solid impurities from the effluent gas, the operating temperature (cooling temperature of the effluent gas) needs to be higher than the dew point of the gas at the operating pressure.

即ち、該流出ガスを露点以下に冷却した場合には、配管
及び（或は）捕集器内にてガスの凝縮を生じ、その凝縮
液中に含まれるメタクリル酸、メタクロレイン等によっ
て重合物が発生してトラブルの原因となり、又有用物の
損失をも招くので望ましくない。That is, when the effluent gas is cooled below its dew point, the gas condenses in the piping and/or the collector, and the methacrylic acid, methacrolein, etc. contained in the condensate cause polymerization. This is not desirable because it causes trouble and also causes loss of useful materials.

従って、流出ガスを冷却する温度は少なくとも該ガスの
捕集器内での操作圧力における露点以上であること、が
必要であり、配管装置内での部分的な温度差を考慮すれ
ば露点より２０〜３０Ｃ以上高くすることが望ましい。Therefore, it is necessary that the temperature at which the outflow gas is cooled is at least higher than the dew point of the gas at the operating pressure in the collector, and if local temperature differences within the piping equipment are taken into account, the temperature is 200 m below the dew point. It is desirable to increase the temperature by ~30C or more.

上限は２５０Ｃであり、この温度より高いと固状不純物
の除去が不充分となる。好ましい温度は２３０Ｃ以下で
ある。The upper limit is 250C; if the temperature is higher than this, solid impurities will not be removed sufficiently. A preferred temperature is 230C or less.

本発明の今一つ゛の利点は５本発明による操作を行わず
流出ガ、ｘ′ｆｒ：そのまま冷却して凝縮させた場合、
前記固状不純物が凝縮器に耐着して閉塞したり又凝縮液
中に懸濁して後の工程へ移ったりするため、塔の形状を
工夫したり固形物を除去する手段を考慮する必要がある
が１本発明ではこれらの問題も発生しない。又、固状不
純物は乾燥状態で取出せるため、メタクリル酸等の有用
物のロスは実質的にない上、焼却、廃棄等の処“理にも
好都合である。Another advantage of the present invention is 5: If the flowed gas is cooled and condensed without performing the operation according to the present invention,
Because the solid impurities adhere to the condenser and clog it, or are suspended in the condensate and transferred to subsequent steps, it is necessary to devise the shape of the tower and consider means to remove the solids. However, in the present invention, these problems do not occur. Furthermore, since solid impurities can be removed in a dry state, there is virtually no loss of useful substances such as methacrylic acid, and it is convenient for disposal such as incineration and disposal.

本発明において用いる捕集器としては、固体のみを選択
的に除去する必要があるので、かかる固体の析出、捕集
に適し且つ固体を系外に取出せるようになっているもの
でなければならないＯ 固体を取出す方法は連続又は断続でもよく。Since it is necessary to selectively remove only solids, the collector used in the present invention must be suitable for precipitation and collection of such solids, and must be capable of removing solids from the system. O The method for removing solids may be continuous or intermittent.

連続カキ取装置又は切替清掃方式でもよい。一般にガス
を冷却する方法として多管式等の熱交換器が用いられる
が、本発明の流出ガスの場合には、液状物質が凝縮しな
い露点以上においても固状不純物が次第に蓄積してつい
には閉塞を起し運転不能となってしまうため、通常の熱
交換を目的とする固体を系外に取出せるよう釦なってい
ない機器は不適当で１ある。A continuous oyster removal device or a switching cleaning method may be used. Generally speaking, a shell-and-tube heat exchanger is used as a method of cooling gas, but in the case of the effluent gas of the present invention, solid impurities gradually accumulate even at temperatures above the dew point at which liquid substances do not condense, eventually leading to blockage. Equipment that does not have a button to allow solids for normal heat exchange to be taken out of the system is unsuitable, as this may cause the system to become inoperable.

本発明におけるメタクロレインの気相接触酸化反応には
、メタクロレインが使用されるが。Methacrolein is used in the gas phase catalytic oxidation reaction of methacrolein in the present invention.

インブチレン、ターシャリーブメノール又はインブチル
アルデヒド等を気相接触酸化して得られるメタクロレイ
ンを含む反応生成ガスをそのまま使用することも出来る
。メタクロレインの気相接触酸化反応は公知の方法によ
って行うことが出来る。その際使用する触媒も特に限定
されず例えばモリブデン及びリンを含有する触媒等が使
用出来る。A reaction product gas containing methacrolein obtained by gas phase catalytic oxidation of inbutylene, tertiary bumenol, inbutyraldehyde, etc. can also be used as it is. The gas phase catalytic oxidation reaction of methacrolein can be carried out by a known method. The catalyst used at that time is not particularly limited, and for example, a catalyst containing molybdenum and phosphorus can be used.

メタクリル酸を抽出する際に用いる抽出溶剤としては１
種々のものが使用出来、特に限定さレス、例えば、トル
エン、キシレン、ヘキサン、ヘク、ｆｉ　ンＦ）　如キ
炭化水素類、メチルインブチルケトンの如きケトン類、
酢酸エチル、酢酸グロビルの如きエステル類を単独又は
混合して使用すること２が出来る。The extraction solvent used when extracting methacrylic acid is 1
A variety of hydrocarbons can be used, without particular limitation, such as toluene, xylene, hexane, hexafluoride, fin F), ketones such as methyl butyl ketone,
Esters such as ethyl acetate and globyl acetate can be used alone or in combination2.

次に第１図および第２図に本発明の適用されるプロセス
の例ヲ示ス。Next, FIGS. 1 and 2 show examples of processes to which the present invention is applied.

第１図において反応器１０２にはメタクロレインを含む
原料ガス又はインブチレン、ターシャリ−ブタノール、
イソブチルアルデヒド等ヲ酸化して得られるメタクロレ
インヲ含むＪ５ｉ　応ガスを管１全通じて導入し気相接
触酸化反応を行わせで主としてメタクリル酸を含む反応
流出ガスを舟、これを管２．３を通じて捕集器１０３へ
導入する。In FIG. 1, a reactor 102 contains a raw material gas containing methacrolein, imbutylene, tert-butanol,
A J5i reaction gas containing methacrolein obtained by oxidizing isobutyraldehyde etc. is introduced through all pipes 1 to carry out a gas phase catalytic oxidation reaction, and the reaction effluent gas containing mainly methacrylic acid is transferred to pipe 2.3. The water is introduced into the collector 103 through the filter.

捕集器１０３はラセン状のカキ取羽根を有する回、転軸
を中心にもち、捕集器内壁は２５０Ｃ以下の所定温度に
保ちカキ取装置は２５０ｔ：以上の所定温度に保つ。The collector 103 has a rotating shaft having helical oyster blades at its center, and the inner wall of the collector is maintained at a predetermined temperature of 250C or lower, and the oyster collector is maintained at a predetermined temperature of 250T: or higher.

内壁には固状不純物が附着しカキ取羽根によってカキ取
られて落下し導管４を経て排出される。１０３の出ガス
は管５．６を通じて冷却器（凝縮器）１０４に導入され
、管１０−１１より導入される熱交１０５で冷却された
凝縮液と接触して凝縮し、主としてメタクリル酸ヲ含む
水溶液を得る。未凝縮ガスは管７を通じて排出きれる。Solid impurities adhere to the inner wall, are removed by the oyster blade, fall, and are discharged through the conduit 4. The output gas from 103 is introduced into a cooler (condenser) 104 through a pipe 5.6, and is condensed by contacting the condensate cooled by a heat exchanger 105 introduced through a pipe 10-11, and mainly contains methacrylic acid. Obtain an aqueous solution. Uncondensed gas can be exhausted through pipe 7.

凝縮液は管８．９を通じて抽出塔１０６へ送られ管１２
より導入される有機溶剤と接触し、てメタクリル酸は有
機層へ抽出され管１３より次の工程へ送られる。抽残水
は管１４より排出される。The condensate is sent to the extraction column 106 via pipe 8.9 and to the extraction column 106 via pipe 12.
The methacrylic acid comes into contact with the organic solvent introduced into the organic layer, and is extracted into the organic layer, which is then sent to the next step through the pipe 13. The raffinate water is discharged through pipe 14.

第２図は捕集器の別の例であるが、捕集器２０３Ａ、２
０３Ｂは二連でフィンを有するＵ字管を内部に有し、Ｕ
字管を通して熱媒を循環しフィンの温度’１２５０ＣＩ
２Ｊ下の所定温度に保ち捕集器内壁は２５０Ｃ以上の所
定温度に保つ。FIG. 2 shows another example of the collector, collectors 203A, 2
03B has two U-shaped tubes with fins inside.
The heat medium is circulated through the tube to reduce the temperature of the fins to 1250 CI.
The temperature is maintained at a predetermined temperature below 2J, and the inner wall of the collector is maintained at a predetermined temperature above 250C.

フィンチューブに固状不純物が附着するので一定時間毎
に切替えフィンチューブを取外して清掃する。Since solid impurities adhere to the fin tube, the fin tube should be removed and cleaned at regular intervals.

以下実施例により本発明の詳細な説明する。The present invention will be explained in detail below with reference to Examples.

実施例１、 第１図に示す〒程において反応器１０２の流出ガス組成
はメメクリル酸２．４モル％、メタクロレイン０．５モ
ル％、酢酸０．９モル％、水蒸気：３’　３．４モル％
、非凝縮ガス６１．５モル％、その他１．３モル％であ
った。捕集器１０３人口でのガス温度は２７０Ｃであっ
た。捕集器内圧力１．５　ｋｇ　／ｃｒｌにおける流出
ガスの露点は約８２Ｃであった。捕集器の内壁をｌｌ０
Ｕ、内部カキ取器の温度を２６０Ｃとして７日間連続運
転を行った。固状不純物の取出しに支障はなかった。Example 1 In the step shown in FIG. 1, the composition of the gas flowing out of the reactor 102 was 2.4 mol% of memethacrylic acid, 0.5 mol% of methacrolein, 0.9 mol% of acetic acid, and water vapor: 3' 3.4 mole%
, 61.5 mol% of non-condensable gas, and 1.3 mol% of others. The gas temperature at collector 103 was 270C. The dew point of the effluent gas was about 82C at a collector internal pressure of 1.5 kg/crl. The inner wall of the collector
U. Continuous operation was performed for 7 days with the temperature of the internal oyster collector set at 260C. There was no problem in removing solid impurities.

碍られた凝縮液を管９より抽出塔１０６に供給し管１２
より抽剤としてキシレンを供給して抽出を行った。抽出
操作は安定し界面にスカムの発生は実質的に認められな
かった。The crushed condensate is supplied to the extraction column 106 through the pipe 9 and then passed through the pipe 12.
Extraction was performed by supplying xylene as an extractant. The extraction operation was stable and virtually no scum was observed at the interface.

実施例２゜ 第１図に示す捕集器の代りに第２図に示しだ捕集器を用
いた工程において反応器１０２の流出ガス組成はメタク
リル酸３，３モル％、メタクロレイン０．５モル％、酢
酸ｏ、ｓモル％、水蒸気２５．８モル％、非凝縮性ガス
６８．３モル％、その他１．３モル％であった。捕集器
２０１３人口でのガス温度は２７０Ｃであった。捕集器
内圧力２．９ｋｇ／ｃ＜における流出ガスの露点は約８
３Ｃであった。Example 2 In a process using the collector shown in FIG. 2 instead of the collector shown in FIG. 1, the composition of the gas flowing out from the reactor 102 was 3.3 mol% of methacrylic acid and 0.5 mol% of methacrolein. mol%, acetic acid o, s mol%, water vapor 25.8 mol%, non-condensable gas 68.3 mol%, and other 1.3 mol%. The gas temperature at the collector 2013 population was 270C. The dew point of the outflow gas at a collector internal pressure of 2.9 kg/c is approximately 8.
It was 3C.

捕集器内のＵ字型フィンチー−プの熱媒温度を１４０Ｃ
１捕集器内壁温度’ｔ２５５　ｔ：’として定期的に切
替えながら１０日間運転を行った。The heat medium temperature of the U-shaped fin chip in the collector is set to 140C.
1 Collector inner wall temperature 't255 t:' was operated for 10 days while changing periodically.

得られた凝縮液を管９より抽出塔１０６に供給し管１２
より抽剤としてキシレンとメチルイソブチルケトンとの
混合物を導入して抽出を行った。The obtained condensate is supplied to the extraction column 106 through the pipe 9 and
Then, extraction was carried out by introducing a mixture of xylene and methyl isobutyl ketone as an extractant.

抽出操作は安定し界面にスカムの発生は実質的に認めら
れなかった。The extraction operation was stable and virtually no scum was observed at the interface.

比較例１゜ 第１図において実施例１と同じガス組成の反応流出ガス
を捕集器１０３を通さず冷却器（凝縮器）１０４に直接
導入した。Comparative Example 1 In FIG. 1, a reaction effluent gas having the same gas composition as in Example 1 was directly introduced into a cooler (condenser) 104 without passing through a collector 103.

得られた凝縮液を抽出塔１０６に管８．９を通じて導入
し実施例１と同様に抽出操作を行った。The obtained condensate was introduced into the extraction column 106 through the pipe 8.9, and the same extraction operation as in Example 1 was performed.

操作に伴ってスカムが発生して界面に蓄積し約２０時間
で運転不能となった。During operation, scum was generated and accumulated on the interface, and operation became impossible after about 20 hours.

又、冷却器（凝縮器）１０４のガス導入口にも固状不純
物が蓄積し５日間で閉塞し運転不能となった。In addition, solid impurities accumulated in the gas inlet of the cooler (condenser) 104, which became clogged within 5 days and became inoperable.

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

第１図は本発明の実施態様の一例を示したフローシート
である。第２図は捕集器の一例を示したものである。 １０２・・・・・・反応器 １０３・・・・・・捕集器 １０４・・・・・・凝縮器 １０６・・・・・・抽出塔 ２０３Ａ　、　２０３Ｂ・・曲捕集器 特許出願人　日本化薬株式会社 第２図FIG. 1 is a flow sheet showing an example of an embodiment of the present invention. FIG. 2 shows an example of a collector. 102... Reactor 103... Collector 104... Condenser 106... Extraction towers 203A, 203B... Bench collector patent applicant Japan Kayaku Co., Ltd. Figure 2

Claims (1)

【特許請求の範囲】[Claims] メタクロレインの気相接触酸化反応により得られるメタ
クリル酸を含有する反応生成ガスを凝縮ζせ、得られる
凝縮液から有機溶剤を用いてメタクリル酸を抽出する方
法において、該ガスを凝縮させる前に捕集器内の捕集部
分の温度を捕集器内の圧力における該ガスの露点以上２
５０ＣＤＪ下の温度に保った捕集器に導き該ガス中に含
有される高沸点、高融点の不純物を捕集せしめた後凝縮
器に導いて凝縮させることを特徴とする酸化反応生成ガ
スの処理法。In a method of condensing a reaction product gas containing methacrylic acid obtained by a gas phase catalytic oxidation reaction of methacrolein and extracting methacrylic acid from the resulting condensate using an organic solvent, the gas is captured before condensing. The temperature of the collecting part in the collector should be 2 or higher than the dew point of the gas at the pressure inside the collector.
Processing of oxidation reaction product gas characterized by introducing it into a collector kept at a temperature of 50 CDJ or below to collect impurities with high boiling points and high melting points contained in the gas, and then introducing it into a condenser to condense it. Law.