JP2001261308A - Method of recovering hydrochloric acid - Google Patents

Method of recovering hydrochloric acid

Info

Publication number
JP2001261308A
JP2001261308A JP2000074213A JP2000074213A JP2001261308A JP 2001261308 A JP2001261308 A JP 2001261308A JP 2000074213 A JP2000074213 A JP 2000074213A JP 2000074213 A JP2000074213 A JP 2000074213A JP 2001261308 A JP2001261308 A JP 2001261308A
Authority
JP
Japan
Prior art keywords
hydrochloric acid
benzene
gas
aromatic hydrocarbon
tower
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2000074213A
Other languages
Japanese (ja)
Other versions
JP4389327B2 (en
Inventor
Akio Sato
明生 佐藤
Chizu Katsuo
智津 勝尾
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toagosei Co Ltd
Original Assignee
Toagosei Co Ltd
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Filing date
Publication date
Application filed by Toagosei Co Ltd filed Critical Toagosei Co Ltd
Priority to JP2000074213A priority Critical patent/JP4389327B2/en
Publication of JP2001261308A publication Critical patent/JP2001261308A/en
Application granted granted Critical
Publication of JP4389327B2 publication Critical patent/JP4389327B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Gas Separation By Absorption (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering hydrochloric acid by which the content of organic compounds in hydrochloric acid formed as a by-product in a chlorinating reaction of an aromatic hydrocarbon such as benzene is reduced. SOLUTION: A reactional gas containing hydrogen chloride gas produced in a chlorinating reaction is brought into contact with benzene in a washing column 4 to absorb and remove organic compounds having a higher boiling point than that of benzene and contained in the reactional gas in the benzene. The reactional gas after the absorption and removal is then fed to an adiabatic absorption type hydrochloric acid recovering column 6 to obtain crude hydrochloric acid from the column bottom of the recovering column 6 and a discharged gas is obtained from the column top of the recovering column 6 when the benzene is chlorinated in a chlorinating reactional column 2 to produce p- dichlorobenzene.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明はベンゼン、トルエン
等の芳香族炭化水素の塩素化反応において副生する塩化
水素ガスから塩酸を回収する方法に関する。
The present invention relates to a method for recovering hydrochloric acid from hydrogen chloride gas by-produced in a chlorination reaction of aromatic hydrocarbons such as benzene and toluene.

【0002】[0002]

【従来の技術】ベンゼンを塩素化して得られるジクロロ
ベンゼン(DCB)は工業的に重要な化合物である。ジ
クロロベンゼンには、オルトジクロロベンゼン(o−D
CB)、メタジクロロベンゼン(m−DCB)、パラジ
クロロベンゼン(p−DCB)の3異性体がある。これ
らの3異性体の内、PDCBは最も需要が多く、防虫剤
等に利用され、またエンジニアリングプラスチックであ
るポリフェニレンサルファイドの原料として注目されて
いる。
2. Description of the Related Art Dichlorobenzene (DCB) obtained by chlorinating benzene is an industrially important compound. Ortho-dichlorobenzene (o-D
There are three isomers: CB), metadichlorobenzene (m-DCB) and paradichlorobenzene (p-DCB). Among these three isomers, PDCB is most in demand, used as an insect repellent and the like, and attracts attention as a raw material for polyphenylene sulfide, which is an engineering plastic.

【0003】従来、ジクロロベンゼンは、塩化第二鉄等
のフリーデルクラフト型触媒を用いてベンゼン(BZ)
またはクロロベンゼン(CB)を塩素化することにより
製造されている。
[0003] Conventionally, dichlorobenzene has been prepared from benzene (BZ) using a Friedel-craft type catalyst such as ferric chloride.
Alternatively, it is produced by chlorinating chlorobenzene (CB).

【0004】製造時にパラジクロロベンゼンの選択率を
高めるため、硫黄、セレン系の無機または有機化合物と
塩化第二鉄とを触媒として併用する方法も提案されてい
る。
[0004] In order to increase the selectivity of paradichlorobenzene during production, there has been proposed a method in which a sulfur or selenium-based inorganic or organic compound and ferric chloride are used in combination as a catalyst.

【0005】更に、ゼオライトを触媒として用いること
により、ベンゼンまたはモノクロロベンゼンの塩素化反
応において、パラジクロロベンゼンの選択率を高める技
術も提案されている(特開昭57ー77631号公報、
特開昭59ー163329号公報) また更に、触媒として活性アルミナを使用することによ
り従来技術の有する問題を解決する技術も開示されてい
る(特開平1ー93550号公報)。
Further, a technique has been proposed in which the selectivity of paradichlorobenzene is increased in the chlorination reaction of benzene or monochlorobenzene by using zeolite as a catalyst (Japanese Patent Application Laid-Open No. 57-77631,
JP-A-59-163329 discloses a technique for solving the problems of the prior art by using activated alumina as a catalyst (JP-A-1-93550).

【0006】これらの製造方法においては、何れもベン
ゼンは気相または液相中で触媒の存在下に塩素化される
が、この塩素化反応においては、塩化水素が副生され、
これが副生塩化水素ガスとして外部に取出される。前記
外部に取出される副生塩化水素ガス中には、塩素化反応
の原料であるベンゼン、及び反応生成物であるクロロベ
ンゼン、ジクロロベンゼン、トリクロロベンゼン(TC
B)等の各種塩素化ベンゼンが少なくともその蒸気圧に
応じて含有されているので、前記副生塩化水素ガスを予
め冷却してベンゼンや塩素化ベンゼンを凝縮し、回収、
利用することが行われている。
In any of these production methods, benzene is chlorinated in the presence of a catalyst in a gas phase or a liquid phase. In this chlorination reaction, hydrogen chloride is produced as a by-product.
This is taken out as by-product hydrogen chloride gas. The by-product hydrogen chloride gas extracted to the outside includes benzene, which is a raw material of the chlorination reaction, and chlorobenzene, dichlorobenzene, trichlorobenzene (TC
Since various chlorinated benzenes such as B) are contained at least according to the vapor pressure, the by-product hydrogen chloride gas is cooled in advance to condense benzene and chlorinated benzene, and
Utilization is being done.

【0007】しかし、前記凝縮による回収は完全なもの
ではなく、冷却温度におけるベンゼン等の各有機化合物
の蒸気圧に相当する量は依然として副生塩化水素ガス中
に残存しており、このためこの副生塩化水素ガスを塩酸
回収塔に送り、ここで水と接触させて得られる塩酸中に
は、これらの塩素化ベンゼン等が含まれている。
However, the recovery by condensation is not complete, and the amount corresponding to the vapor pressure of each organic compound such as benzene at the cooling temperature still remains in the by-product hydrogen chloride gas. The raw hydrogen chloride gas is sent to the hydrochloric acid recovery tower, where the hydrochloric acid obtained by contacting with water contains these chlorinated benzenes and the like.

【0008】また、塩酸回収塔の塔頂側から取出される
排出ガスには、水と塩化水素以外にベンゼンや塩素化ベ
ンゼンが含まれており、これらは冷却されることにより
凝縮し、ベンゼンを主成分とする有機層と塩酸層とに層
分離する。通常、層分離したこれらの有機層と塩酸層と
は液液分離される。しかし、前記有機層は、塩素化ベン
ゼンを含有しているため比重が塩酸に近い。このため塩
酸層と有機層との液液分離は困難であり、その結果その
後の塩酸精製工程に支障をもたらすようになると共に、
前記有機層を回収して再度製造原料として用いることも
困難になる等の問題がある。
[0008] Exhaust gas withdrawn from the top of the hydrochloric acid recovery tower contains benzene and chlorinated benzene in addition to water and hydrogen chloride, and these are condensed by being cooled, and the benzene is condensed. The layers are separated into an organic layer as a main component and a hydrochloric acid layer. Usually, these separated organic layers and the hydrochloric acid layer are subjected to liquid-liquid separation. However, since the organic layer contains chlorinated benzene, the specific gravity is close to that of hydrochloric acid. For this reason, liquid-liquid separation of the hydrochloric acid layer and the organic layer is difficult, and as a result, the subsequent hydrochloric acid purification process is hindered,
There is a problem that it becomes difficult to collect the organic layer and use it again as a raw material.

【0009】[0009]

【発明が解決しようとする課題】本発明者等は、上記問
題を解決するために種々検討した結果、ベンゼンの塩素
化反応で発生する副生塩化水素ガスをベンゼンと接触さ
せることにより、副生塩化水素ガス中に含有される塩素
化ベンゼンをベンゼンと置換させた後、断熱吸収式回収
塔に送って粗塩酸を製造するようにすると、回収塔の塔
底から取出される粗塩酸中の有機物含有量を大幅に減少
させ得ると共に、塔頂から取出される排出ガスは、冷却
することにより凝縮して塩酸層と有機層とに分離する
が、有機層はベンゼンを主成分とするため比重が塩酸層
よりも充分小さく、このため簡単に上記2層は液液分離
でき、このようにして得られた各層はそれぞれ有効利用
できることを知得した。更に、上記方法はベンゼンに限
られず、各種の芳香族化合物一般にも適用できることを
知得した。本発明は、上記知見に基づき完成するに至っ
たものである。
The inventors of the present invention have conducted various studies to solve the above problems, and as a result, by contacting by-product hydrogen chloride gas generated in benzene chlorination reaction with benzene, the by-product After replacing the chlorinated benzene contained in the hydrogen chloride gas with benzene and sending it to the adiabatic absorption type recovery tower to produce crude hydrochloric acid, the organic matter in the crude hydrochloric acid removed from the bottom of the recovery tower While the content can be greatly reduced, the exhaust gas withdrawn from the top is condensed by cooling and separates into a hydrochloric acid layer and an organic layer. It was found that the two layers were easily separated from the hydrochloric acid layer by liquid-liquid separation, and that each layer thus obtained could be effectively used. Furthermore, it has been found that the above method is not limited to benzene, but can be applied to various aromatic compounds in general. The present invention has been completed based on the above findings.

【0010】従って、本発明の目的とするところは、従
来の問題点を解決する塩酸の回収方法を提供することに
ある。
Accordingly, it is an object of the present invention to provide a method for recovering hydrochloric acid which solves the conventional problems.

【0011】[0011]

【課題を解決するための手段】上記目的を達成するため
の本発明は以下に記載するものである。
The present invention for achieving the above object is as described below.

【0012】〔1〕 芳香族炭化水素の塩素化反応に
より塩素化芳香族炭化水素を製造するに当り、前記塩素
化反応において発生する塩化水素ガスを含む反応ガスを
原料の芳香族炭化水素と接触させて前記反応ガス中に含
まれる該芳香族炭化水素よりも高沸点の塩素化芳香族炭
化水素を該芳香族炭化水素に吸収除去させ、次いで吸収
除去後の反応ガスを断熱吸収式塩酸回収塔に送り、塔底
から粗塩酸を得ると共に、塔頂から排出ガスを抜出すこ
とを特徴とする塩酸の回収方法。
[1] In producing a chlorinated aromatic hydrocarbon by a chlorination reaction of an aromatic hydrocarbon, a reaction gas containing hydrogen chloride gas generated in the chlorination reaction is brought into contact with a raw material aromatic hydrocarbon. Then, the chlorinated aromatic hydrocarbon having a boiling point higher than that of the aromatic hydrocarbon contained in the reaction gas is absorbed and removed by the aromatic hydrocarbon. To obtain crude hydrochloric acid from the bottom of the column and withdraw exhaust gas from the top of the column.

【0013】〔2〕 排出ガスを凝縮させ、原料の芳香
族炭化水素を主成分とする有機層と塩酸層とに液液分離
し、前記有機層を脱水後、塩素化反応に再利用する
〔1〕に記載の塩酸の回収方法。
[2] The exhaust gas is condensed and separated into liquid and liquid into an organic layer mainly composed of an aromatic hydrocarbon as a raw material and a hydrochloric acid layer. After dehydration of the organic layer, the organic layer is reused in a chlorination reaction [ The method for recovering hydrochloric acid according to 1).

【0014】〔3〕 排出ガスを凝縮させ、原料の芳香
族炭化水素を主成分とする有機層と塩酸層とに液液分離
し、前記塩酸層を断熱吸収式塩酸回収塔に返送する
〔1〕に記載の塩酸の回収方法。
[3] The exhaust gas is condensed, liquid-liquid separated into an organic layer mainly composed of an aromatic hydrocarbon as a raw material and a hydrochloric acid layer, and the hydrochloric acid layer is returned to the adiabatic absorption type hydrochloric acid recovery tower [1]. ] The method for recovering hydrochloric acid according to [1].

【0015】以下、図面を参照して本発明を詳細に説明
する。
Hereinafter, the present invention will be described in detail with reference to the drawings.

【0016】[0016]

【発明の実施の形態】図1は本発明の塩酸の回収方法を
組込んだp−ジクロロベンゼンの製造装置の一例を示す
フロー図である。
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing an example of an apparatus for producing p-dichlorobenzene incorporating the method for recovering hydrochloric acid of the present invention.

【0017】図1中、2は塩素化反応塔で、内部に触媒
が充填されている。触媒としては、公知の活性アルミ
ナ、シリカ・アルミナ、結晶性アルミノシリケート等の
固体酸触媒や、塩化鉄、塩化アルミニウム等のフリーデ
ルクラフト型触媒等が例示される。前記塩素化反応塔2
には、原料の芳香族炭化水素であるベンゼン及び塩素等
が供給され、塩素化反応塔2内でこれらが反応して、p
−ジクロロベンゼンを主成分とする塩素化ベンゼンが反
応生成物として取出される。この反応自体は公知のもの
である。
In FIG. 1, reference numeral 2 denotes a chlorination reaction tower, which is filled with a catalyst. Examples of the catalyst include known solid acid catalysts such as activated alumina, silica-alumina, and crystalline aluminosilicate, and Friedel-craft type catalysts such as iron chloride and aluminum chloride. The chlorination reaction tower 2
Is supplied with benzene, chlorine, etc., which are aromatic hydrocarbons as raw materials, and these react in the chlorination reaction tower 2 to form p
-Chlorinated benzene based on dichlorobenzene is removed as a reaction product. This reaction itself is known.

【0018】前記塩素化反応においては、反応ガスが発
生するが、この反応ガスには塩化水素ガスを主成分と
し、その他の成分として、原料ベンゼン、及びモノクロ
ロベンゼン、o−、m−、p−ジクロロベンゼン、トリ
クロロベンゼン等の塩素化ベンゼンが含まれている。
In the chlorination reaction, a reaction gas is generated. The reaction gas contains hydrogen chloride gas as a main component, and other components include raw material benzene, monochlorobenzene, o-, m- and p-. Contains chlorinated benzene such as dichlorobenzene and trichlorobenzene.

【0019】この反応ガスは、塩素化反応塔2の塔頂か
ら取出され、必要により熱交換器(不図示)を通ってこ
こで前記塩素化ベンゼンの一部を凝縮除去された後、洗
浄塔4の塔底側に送られる。
This reaction gas is taken out from the top of the chlorination reaction tower 2 and if necessary passes through a heat exchanger (not shown) to condense and remove a part of the chlorinated benzene. 4 to the bottom side.

【0020】前記洗浄塔4内においては、塔頂側から供
給される洗浄液ベンゼンが洗浄塔4内を流下しながら、
塔底側から供給され洗浄塔内を上昇する反応ガスと向流
状態で気液接触を繰返し、これにより反応ガス中のベン
ゼンよりも高沸点の有機化合物(CB、DCB、TC
B、テトラクロロベンゼン、ヘキサクロロベンゼン等の
塩素化ベンゼン)が流下するベンゼンによって抽出除去
される。
In the washing tower 4, the washing liquid benzene supplied from the top of the washing tower 4 flows down the washing tower 4,
The gas-liquid contact is repeated in a counter-current state with the reaction gas supplied from the bottom of the tower and rising in the washing tower, whereby the organic compound having a higher boiling point than benzene (CB, DCB, TC
B, chlorinated benzenes such as tetrachlorobenzene and hexachlorobenzene) are extracted and removed by the flowing benzene.

【0021】ベンゼンよりも高沸点の有機化合物を抽出
しながら洗浄塔4内を流下したベンゼン溶液(洗浄液)
は、次いで塩素化反応塔2の塔底側に返送され、塩素化
反応の原料として再利用される。
A benzene solution (washing liquid) flowing down in the washing tower 4 while extracting an organic compound having a higher boiling point than benzene.
Is then returned to the bottom of the chlorination reaction tower 2 and reused as a raw material for the chlorination reaction.

【0022】洗浄塔4は、充填塔、棚段塔、濡れ壁塔、
スプレー塔、気泡塔等の一般的ガス吸収装置として用い
られている装置が利用できる。これらの内、充填塔は圧
損失が比較的小さく、ガス吸収効率が高いので、好まし
いものである。充填塔の液/ガス流量の運転条件として
は、フラッディング速度以下、特にフラッディング速度
の50%前後が好ましい。
The washing tower 4 includes a packed tower, a tray tower, a wet wall tower,
A device used as a general gas absorbing device such as a spray tower or a bubble tower can be used. Among these, the packed tower is preferable because it has a relatively small pressure loss and a high gas absorption efficiency. The operation condition of the liquid / gas flow rate of the packed tower is preferably equal to or lower than the flooding speed, and particularly preferably about 50% of the flooding speed.

【0023】塩化水素ガスの発生量が大きく、洗浄塔の
塔径が大きくなる場合は、棚段塔の使用が好ましい。
When the amount of generated hydrogen chloride gas is large and the diameter of the washing tower is large, the use of a plate tower is preferred.

【0024】スプレー塔は反応ガス中に洗浄液ベンゼン
が飛沫同伴により持込まれるので、この点に注意すれば
使用できる。
The spray tower can be used by paying attention to this point, because the cleaning liquid benzene is carried into the reaction gas by entrainment.

【0025】洗浄塔4の操作温度は、一般に低温である
ほど洗浄後の反応ガス中のベンゼン含有量が少なくなる
ので、低温の方が好ましい。しかし、洗浄液ベンゼンの
凝固点(5℃)以上で操作する必要があるので、5〜3
0℃が好ましく、特に7〜10℃が望ましい。
In general, the lower the operating temperature of the washing tower 4 is, the lower the benzene content in the reaction gas after washing becomes. However, since it is necessary to operate at a temperature higher than the freezing point (5 ° C.) of the cleaning liquid benzene, 5 to 3
0 ° C is preferable, and particularly preferably 7 to 10 ° C.

【0026】洗浄塔4の操作圧力は、高圧の方が好まし
い。高圧であるほど洗浄液ベンゼンの蒸気圧が低くな
り、その結果洗浄後の反応ガス中のベンゼン含有量が減
少する。しかし、高圧装置は高価であるので、1MPa
以下の圧力で操作することが好ましい。また、減圧にす
ると、ベンゼンや塩素化ベンゼン等の有機化合物の分圧
が大きくなり、その結果、洗浄後の反応ガス中のベンゼ
ンや有機化合物の含有量が増加するので好ましくない。
従って、洗浄塔の操作圧力は、常圧〜1MPaが好まし
い。
The operating pressure of the washing tower 4 is preferably higher. The higher the pressure, the lower the vapor pressure of the cleaning liquid benzene, and as a result, the lower the benzene content in the reaction gas after cleaning. However, high-pressure equipment is expensive, so 1 MPa
It is preferred to operate at the following pressures. Further, when the pressure is reduced, the partial pressure of an organic compound such as benzene or chlorinated benzene increases, and as a result, the content of benzene or the organic compound in the reaction gas after washing increases, which is not preferable.
Therefore, the operating pressure of the washing tower is preferably normal pressure to 1 MPa.

【0027】洗浄塔4内を上昇して、塩素化ベンゼンの
ほとんどすべてが除去された反応ガスは、次いで断熱吸
収式塩酸回収塔6に送られ、ここで反応ガス中の塩化水
素が塔内を流下する水に吸収されて粗塩酸となり、回収
塔6の塔底側から取出される。
The reaction gas from which the chlorinated benzene has been almost completely removed by ascending in the washing tower 4 is then sent to an adiabatic absorption type hydrochloric acid recovery tower 6, where hydrogen chloride in the reaction gas passes through the tower. It is absorbed by the flowing water to become crude hydrochloric acid, and is taken out from the bottom side of the recovery tower 6.

【0028】断熱吸収式塩酸回収塔6は、構造的には、
前記洗浄塔4とほぼ同一構造のものである。機能的に
は、回収塔6内で、反応ガス中の塩化水素が水に断熱吸
収され、その際に発生する大きな溶解熱に基づく温度上
昇により水が蒸発させられ、また反応ガス中に含有され
ているベンゼンや微量に存在する塩素化ベンゼンの凝縮
が妨げられる結果、それらの有機物が粗塩酸中に混入す
ることが避けられる。
The adiabatic absorption type hydrochloric acid recovery tower 6 is structurally
It has almost the same structure as the washing tower 4. Functionally, in the recovery tower 6, the hydrogen chloride in the reaction gas is adiabatically absorbed by the water, and the water is evaporated by the temperature rise based on the large heat of dissolution generated at that time, and is contained in the reaction gas. As a result of preventing condensation of benzene present and chlorinated benzene present in a trace amount, such organic substances can be prevented from being mixed into the crude hydrochloric acid.

【0029】前記断熱吸収式塩酸回収塔6の塔底側から
取出される粗塩酸は、その後塩酸濃度調整工程16、活
性炭処理等による塩酸精製工程18を順次通過して、製
品塩酸として取出される。
The crude hydrochloric acid taken out from the bottom side of the adiabatic absorption type hydrochloric acid recovery tower 6 then passes through a hydrochloric acid concentration adjusting step 16 and a hydrochloric acid refining step 18 by activated carbon treatment or the like in order to be taken out as a product hydrochloric acid. .

【0030】一方、断熱吸収式塩酸回収塔6の塔頂側か
らは、排出ガスが取出される。この排出ガスは、回収塔
6内で水と反応ガスとが向流接触することにより、反応
ガス中の塩化水素ガスの大部分が吸収除去されたガス
で、主として、大部分を占める水蒸気及びわずかな塩化
水素ガスとベンゼンガスとからなる。
On the other hand, exhaust gas is taken out from the top of the adiabatic absorption type hydrochloric acid recovery tower 6. This exhaust gas is a gas in which most of the hydrogen chloride gas in the reaction gas has been absorbed and removed by the countercurrent contact of water and the reaction gas in the recovery tower 6, and mainly the steam and the slightly Hydrogen gas and benzene gas.

【0031】前記排出ガスは、先ずコンデンサー8を通
過する際に冷却されて凝縮液になり、液液分離器10に
送られ、ここで有機層12と塩酸層14とに分離され
る。
The exhaust gas is first cooled when passing through the condenser 8 to be condensed liquid, sent to the liquid-liquid separator 10, where it is separated into the organic layer 12 and the hydrochloric acid layer 14.

【0032】分離された前記塩酸層は、その後断熱吸収
式塩酸回収塔6の塔頂と塔底との中間部に返送される。
また、分離された前記有機層12は蒸留法や、シリカゲ
ル、モレキュラーシーブ、無水硫酸ナトリウム等の固体
脱水剤等を用いて脱水処理がなされた後、塩素化反応塔
2に返送され、再利用される。上記実施の形態において
は、原料の芳香族炭化水素としてベンゼンが用いられた
が、これに限られず、塩素化反応塔2で塩素化すること
の出来る全ての芳香族炭化水素が原料として用いられ
る。特に好ましい原料の芳香族炭化水素としては、ベン
ゼン以外に、トルエン、キシレン、エチルベンゼン等が
例示され、製造目的物としては、p−ジクロロベンゼン
の他に、モノクロロベンゼンおよびジクロロトルエン等
が挙げられる。この場合、塩素化反応塔2の反応条件
は、使用される原料の芳香族炭化水素に応じて適宜選択
される。反応条件自体は公知である。また、洗浄塔4の
洗浄液としては、原料の芳香族炭化水素が使用される。
原料の芳香族炭化水素が洗浄液として用いられることに
より、反応ガス中のより沸点の高い塩素化芳香族炭化水
素類が効率よく抽出除去されると共に、この洗浄液が塩
素化反応塔に返送されることにより、塩素化反応の原料
として再利用される。洗浄塔4の運転条件も、上記実施
の形態の場合と同様の考え方が適用される。更に、断熱
吸収塔6及びその他の装置、運転条件等も上記実施の形
態と同様の考え方が適用されるので、その説明を省略す
る。
The separated hydrochloric acid layer is then returned to an intermediate portion between the top and bottom of the adiabatic absorption type hydrochloric acid recovery column 6.
Further, the separated organic layer 12 is subjected to a dehydration treatment using a distillation method or a solid dehydrating agent such as silica gel, molecular sieve, anhydrous sodium sulfate or the like, and then returned to the chlorination reaction tower 2 for reuse. You. In the above embodiment, benzene was used as a raw material aromatic hydrocarbon, but the present invention is not limited to this, and all aromatic hydrocarbons that can be chlorinated in the chlorination reaction tower 2 are used as the raw material. Particularly preferred aromatic hydrocarbons, in addition to benzene, include toluene, xylene, ethylbenzene, and the like. Examples of the production target include p-dichlorobenzene, monochlorobenzene, dichlorotoluene, and the like. In this case, the reaction conditions for the chlorination reaction tower 2 are appropriately selected according to the aromatic hydrocarbon used as the raw material. The reaction conditions themselves are known. As the cleaning liquid for the cleaning tower 4, an aromatic hydrocarbon as a raw material is used.
By using the aromatic hydrocarbon as the raw material as the cleaning liquid, the chlorinated aromatic hydrocarbons having a higher boiling point in the reaction gas can be efficiently extracted and removed, and the cleaning liquid is returned to the chlorination reaction tower. As a result, it is reused as a raw material for the chlorination reaction. The same concept as in the above embodiment is applied to the operating conditions of the washing tower 4. Further, the same concept as in the above-described embodiment is applied to the adiabatic absorption tower 6, other devices, operating conditions, and the like, and a description thereof will be omitted.

【0033】なお、本発明の塩酸の回収方法が組込まれ
るp−ジクロロベンゼン等の塩素化芳香族炭化水素の製
造装置は、上記実施の形態の構成のものに限られず、現
存する全ての装置に組込まれることができる。このよう
な装置として、例えば、塩素化工程後生成する塩素化ベ
ンゼン中のベンゼン及びモノクロロベンゼンを分離して
塩素化工程に返送する工程を具備するもの、更には高次
塩素化ベンゼンを分離してトランスクロロ化反応を行っ
た後、塩素化工程に返送する工程を具備するもの等が挙
げられる。
The apparatus for producing chlorinated aromatic hydrocarbons such as p-dichlorobenzene into which the method for recovering hydrochloric acid of the present invention is incorporated is not limited to the structure of the above-described embodiment, but is applicable to all existing apparatuses. Can be incorporated. As such an apparatus, for example, one having a step of separating benzene and monochlorobenzene in chlorinated benzene generated after the chlorination step and returning the same to the chlorination step, further separating high-order chlorinated benzene After the transchlorination reaction, those having a step of returning to the chlorination step and the like can be mentioned.

【0034】[0034]

【実施例】実施例1〜3、比較例1 実施例1〜3として、図1に示す構成のp−ジクロロベ
ンゼンの製造装置を用いて塩酸の回収を行った。
EXAMPLES Examples 1 to 3 and Comparative Example 1 As Examples 1 to 3, hydrochloric acid was recovered using the apparatus for producing p-dichlorobenzene having the structure shown in FIG.

【0035】比較例として、塩素化反応塔2の塔頂から
取出される反応ガスを洗浄塔4に送らず、直接断熱吸収
式塩酸回収塔6に送る以外は実施例と同様にして、塩酸
の回収を行った。
As a comparative example, the reaction gas taken out from the top of the chlorination reaction tower 2 was not sent to the washing tower 4 but was sent directly to the adiabatic absorption type hydrochloric acid recovery tower 6 in the same manner as in the example. Recovery was performed.

【0036】得られた結果を表1に示した。The results obtained are shown in Table 1.

【0037】[0037]

【表1】 [Table 1]

【0038】実施例1においては、塩素化反応により得
られる反応ガスを洗浄塔に送ってベンゼンによる洗浄操
作を行った後、断熱吸収式塩酸回収塔で塩化水素の回収
を行った。表1から明らかなように、断熱吸収式塩酸回
収塔入口ガス(洗浄後の反応ガス)中の全有機化合物含
有量は比較例1よりも多い。しかし、断熱吸収式塩酸回
収塔排出ガスの凝縮液における、塩酸層と、有機層との
比重差は比較例の比重差よりも大きい。このため、実施
例1の場合は塩酸層と有機層との液液分離が容易にな
り、塩酸回収塔に返送する塩酸層中に混入する有機化合
物量が少なくなる。その結果、回収塔の塔底から取出し
て塩酸濃度調整工程で濃度を調整した後の塩酸に含まれ
る全有機化合物濃度は比較例1のそれよりも少なくなっ
ている。
In Example 1, the reaction gas obtained by the chlorination reaction was sent to a washing tower to perform a washing operation with benzene, and then hydrogen chloride was collected in an adiabatic absorption type hydrochloric acid collecting tower. As is clear from Table 1, the content of all organic compounds in the gas at the inlet of the adiabatic absorption-type hydrochloric acid recovery tower (reaction gas after washing) is larger than that in Comparative Example 1. However, the specific gravity difference between the hydrochloric acid layer and the organic layer in the condensate of the adiabatic absorption type hydrochloric acid recovery tower exhaust gas is larger than the specific gravity difference of the comparative example. Therefore, in the case of Example 1, the liquid-liquid separation between the hydrochloric acid layer and the organic layer is facilitated, and the amount of the organic compound mixed in the hydrochloric acid layer returned to the hydrochloric acid recovery tower is reduced. As a result, the concentration of all the organic compounds contained in the hydrochloric acid after being taken out from the bottom of the recovery tower and adjusted in the hydrochloric acid concentration adjusting step is lower than that in Comparative Example 1.

【0039】実施例2においては、洗浄塔の操作温度を
実施例1よりも低下させた。表1から明らかなように、
操作温度を下げると、洗浄液であるベンゼンを含めて全
ての有機化合物の蒸気圧が減少するため、実施例1と比
較し、洗浄後の反応ガス中の全有機化合物含有量が減少
し、その結果濃度調整後の塩酸中の全有機化合物含有量
も減少している。
In Example 2, the operating temperature of the washing tower was lower than in Example 1. As is clear from Table 1,
When the operating temperature is lowered, the vapor pressure of all organic compounds including benzene which is a cleaning liquid is reduced, so that the content of all organic compounds in the reaction gas after cleaning is reduced as compared with Example 1, and as a result, The content of total organic compounds in hydrochloric acid after the concentration adjustment is also reduced.

【0040】実施例3においては、洗浄塔の操作圧力を
実施例1よりも高めた。表1から明らかなように、操作
圧力を高めると、有機化合物の分圧が減少するため、実
施例1と比較し、洗浄後の反応ガス中の全有機化合物含
有量が減少し、その結果濃度調整後の塩酸中の全有機化
合物含有量も減少している。
In Example 3, the operating pressure of the washing tower was higher than in Example 1. As is clear from Table 1, when the operating pressure is increased, the partial pressure of the organic compound is reduced. Therefore, as compared with Example 1, the total organic compound content in the reaction gas after washing is reduced, and as a result, the concentration is reduced. The total organic compound content in the hydrochloric acid after the adjustment is also reduced.

【0041】比較例1においては、洗浄塔を経由して洗
浄操作をすることなく、塩素化反応により得られる反応
ガスを直接断熱吸収式塩酸回収塔に送り、塩酸の回収を
行った。断熱吸収式塩酸回収塔入口ガス(反応ガス)中
の全有機化合物含有量は実施例1〜3と比較して少な
い。しかし、断熱吸収式塩酸回収塔排出ガスの凝縮液の
有機層と塩酸層との比重差が小さいため、液液分離効率
が悪い。また、高沸点の塩素化芳香族炭化水素が洗浄除
去されないまま前記回収塔に供給され、それが該回収塔
において気化せずに塩酸に混入される結果、濃度調整後
の塩酸中の全有機化合物含有量は実施例1〜3と比較し
遥かに多くなる。
In Comparative Example 1, the reaction gas obtained by the chlorination reaction was directly sent to the adiabatic absorption type hydrochloric acid recovery tower without performing the cleaning operation via the cleaning tower, and the hydrochloric acid was recovered. The total organic compound content in the gas (reaction gas) at the inlet of the adiabatic absorption-type hydrochloric acid recovery tower is smaller than in Examples 1 to 3. However, since the difference in specific gravity between the organic layer and the hydrochloric acid layer of the condensate of the exhaust gas from the adiabatic absorption type hydrochloric acid recovery tower is small, the liquid-liquid separation efficiency is poor. Further, the chlorinated aromatic hydrocarbon having a high boiling point is supplied to the recovery tower without being washed and removed, and is mixed with hydrochloric acid without being vaporized in the recovery tower. As a result, all the organic compounds in the hydrochloric acid after the concentration adjustment are obtained. The content is much higher than in Examples 1-3.

【0042】[0042]

【発明の効果】本発明においては、原料の芳香族炭化水
素を塩素化する際に生成する塩素化芳香族炭化水素等の
有機化合物を含有する塩化水素ガスを、塩素化芳香族炭
化水素よりも低沸点の芳香族炭化水素で洗浄し、塩化水
素ガス中のより高沸点の塩素化芳香族炭化水素を沸点の
低い芳香族炭化水素に置換することにより、断熱吸収式
塩酸回収塔において有機化合物の凝縮を防止し、塔底か
ら取出される粗塩酸中の有機化合物含有量を低減させ
る。更に、回収塔の塔頂から取出される排出ガスの凝縮
液は、有機層と塩酸層とに分離されるが、前記有機層は
塩素化芳香族炭化水素の含有量が少ないので比重が小さ
く、このため有機層と塩酸層との液液分離は容易で、互
いに他層が混入することなく分離され、分離効率が高
い。このようにして分離された有機層、及び塩酸層は互
いの混入が避けられているので純度が高く、このためこ
れらは有効に再利用でき、その結果得られる製品塩酸の
純度も高い。
According to the present invention, the hydrogen chloride gas containing an organic compound such as chlorinated aromatic hydrocarbon produced when chlorinating the aromatic hydrocarbon as the raw material is used more than the chlorinated aromatic hydrocarbon. By washing with a low-boiling aromatic hydrocarbon and replacing the higher-boiling chlorinated aromatic hydrocarbons in the hydrogen chloride gas with lower-boiling aromatic hydrocarbons, the adiabatic absorption-type hydrochloric acid recovery tower can remove organic compounds. Prevents condensation and reduces the content of organic compounds in the crude hydrochloric acid removed from the bottom of the column. Furthermore, the condensate of the exhaust gas withdrawn from the top of the recovery tower is separated into an organic layer and a hydrochloric acid layer, but the organic layer has a small specific gravity because the content of chlorinated aromatic hydrocarbons is small, Therefore, liquid-liquid separation between the organic layer and the hydrochloric acid layer is easy, and the layers are separated from each other without mixing with other layers, and the separation efficiency is high. The organic layer and the hydrochloric acid layer separated in this way have high purity because they are prevented from being mixed with each other, so that they can be effectively reused and the purity of the resulting hydrochloric acid product is high.

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

【図1】本発明の塩酸の回収方法を組込んだ塩素化ベン
ゼンの製造装置の一例を示すフロー図である。
FIG. 1 is a flow chart showing an example of an apparatus for producing chlorinated benzene incorporating the method for recovering hydrochloric acid of the present invention.

【符号の説明】[Explanation of symbols]

2 塩素化反応塔 4 洗浄塔 6 断熱吸収式塩酸回収塔 8 コンデンサー 10 液液分離器 12 有機層 14 塩酸層 16 塩酸濃度調整工程 18 塩酸精製工程 2 chlorination reaction tower 4 washing tower 6 adiabatic absorption type hydrochloric acid recovery tower 8 condenser 10 liquid-liquid separator 12 organic layer 14 hydrochloric acid layer 16 hydrochloric acid concentration adjusting step 18 hydrochloric acid refining step

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 FI テーマコート゛(参考) C07C 25/08 C07C 25/08 // C07B 61/00 300 C07B 61/00 300 63/00 63/00 G B Fターム(参考) 4D020 AA10 BA15 BB04 BC01 BC10 CB01 CB08 CB18 CB25 CB28 CD10 4H006 AA02 AA04 AC30 AD16 AD18 BA09 BA19 BA39 BA68 BA71 BC52 BD82 BD84 BE53 EA21 4H039 CA52 CD20 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) C07C 25/08 C07C 25/08 // C07B 61/00 300 C07B 61/00 300 63/00 63/00 G BF term (reference) 4D020 AA10 BA15 BB04 BC01 BC10 CB01 CB08 CB18 CB25 CB28 CD10 4H006 AA02 AA04 AC30 AD16 AD18 BA09 BA19 BA39 BA68 BA71 BC52 BD82 BD84 BE53 EA21 4H039 CA52 CD20

Claims (3)

【特許請求の範囲】[Claims] 【請求項1】 芳香族炭化水素の塩素化反応により塩素
化芳香族炭化水素を製造するに当り、前記塩素化反応に
おいて発生する塩化水素ガスを含む反応ガスを原料の芳
香族炭化水素と接触させて前記反応ガス中に含まれる該
芳香族炭化水素よりも高沸点の塩素化芳香族炭化水素を
該芳香族炭化水素に吸収除去させ、次いで吸収除去後の
反応ガスを断熱吸収式塩酸回収塔に送り、塔底から粗塩
酸を得ると共に、塔頂から排出ガスを抜出すことを特徴
とする塩酸の回収方法。
In producing a chlorinated aromatic hydrocarbon by a chlorination reaction of an aromatic hydrocarbon, a reaction gas containing hydrogen chloride gas generated in the chlorination reaction is brought into contact with a raw material aromatic hydrocarbon. Then, the chlorinated aromatic hydrocarbon having a higher boiling point than the aromatic hydrocarbon contained in the reaction gas is absorbed and removed by the aromatic hydrocarbon, and then the reaction gas after the absorption and removal is passed through an adiabatic absorption-type hydrochloric acid recovery column. A method for recovering hydrochloric acid, comprising feeding crude hydrochloric acid from the bottom of the column and extracting exhaust gas from the top of the column.
【請求項2】 排出ガスを凝縮させ、原料の芳香族炭化
水素を主成分とする有機層と塩酸層とに液液分離し、前
記有機層を脱水後、塩素化反応に再利用する請求項1に
記載の塩酸の回収方法。
2. The exhaust gas is condensed, liquid-liquid separated into an organic layer mainly composed of an aromatic hydrocarbon as a raw material and a hydrochloric acid layer, and the organic layer is dehydrated and reused in a chlorination reaction. 2. The method for recovering hydrochloric acid according to 1.
【請求項3】 排出ガスを凝縮させ、原料の芳香族炭化
水素を主成分とする有機層と塩酸層とに液液分離し、前
記塩酸層を断熱吸収式塩酸回収塔に返送する請求項1に
記載の塩酸の回収方法。
3. The exhaust gas is condensed, liquid-liquid separated into an organic layer mainly composed of an aromatic hydrocarbon as a raw material and a hydrochloric acid layer, and the hydrochloric acid layer is returned to an adiabatic absorption type hydrochloric acid recovery tower. 3. The method for recovering hydrochloric acid according to 1.).
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