JP2019131526A - Method for recovering acetic acid from acetic acid-containing aqueous solution - Google Patents
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本発明は、酢酸の回収方法に関し、より具体的には、酢酸含有水溶液からの酢酸の回収方法に関する。 The present invention relates to a method for recovering acetic acid, and more specifically to a method for recovering acetic acid from an acetic acid-containing aqueous solution.
テレフタル酸は例えばポリエチレンテレフタレートなどのポリエステルの素原料として工業的に大量に生産・使用され、また、各種化学用途においても素原料として大量に用いられている。テレフタル酸の製造方法としては、酸化反応器において重金属化合物及び臭素化合物を触媒として用い、パラキシレンを酢酸溶媒中で分子状酸素含有ガスと接触させて液相酸化する方法が一般的である。この製造方法においては、スラリー状の酸化反応生成物からテレフタル酸を分離すると酢酸溶液が廃液として排出される。このため、効率的な酢酸の回収方法が希求されている。酢酸の回収方法としては、通常は、脱水蒸留塔を用いての回収が一般的であり、酢酸は蒸留塔の下部から缶出液として回収されるが、留出液としては酢酸及び酢酸エステルを含む水溶液が得られ、すなわち、蒸留法のみによっては酢酸を効率よく回収することができない。このことは水−酢酸系において、気液平衡上の問題で分離が難しいこと、特に酢酸が低濃度であるときの分離が困難という課題があった。 Terephthalic acid is industrially produced and used in large quantities as a raw material for polyester such as polyethylene terephthalate, and is also used in large quantities as a raw material in various chemical applications. As a method for producing terephthalic acid, a method in which a heavy metal compound and a bromine compound are used as catalysts in an oxidation reactor, and paraxylene is brought into contact with a molecular oxygen-containing gas in an acetic acid solvent to perform liquid phase oxidation. In this production method, when terephthalic acid is separated from the slurry-like oxidation reaction product, the acetic acid solution is discharged as a waste liquid. For this reason, an efficient method for recovering acetic acid is desired. As a method for recovering acetic acid, recovery using a dehydration distillation column is generally used, and acetic acid is recovered as bottoms from the bottom of the distillation column, but acetic acid and acetic acid ester are used as the distillate. In other words, acetic acid cannot be efficiently recovered by distillation alone. This is a problem in the water-acetic acid system in that separation is difficult due to gas-liquid equilibrium problems, and in particular, separation is difficult when acetic acid is at a low concentration.
かかる問題点に対処する方法として、蒸留塔留出液に含まれる微量酢酸を回収するため、抽剤として酢酸エステル等を使用して回収する方法（特許文献１、特許文献２、特許文献３、特許文献４）や、蒸留塔留出液を膜分離することで、水分を取り除き、濃縮して回収する方法（特許文献５、特許文献６）が提案されている。
As a method of coping with such problems, a method of recovering trace amounts of acetic acid contained in the distillation column distillate by using an acetate ester or the like as an extractant (
しかし、抽剤を使用して回収する方法では、抽出操作の後、抽出した液を蒸留によって分離するために蒸留塔下部から回収される液（缶出液）中への抽剤の移行が無視できない程度に発生して抽剤のロスが発生する。また、膜分離法によって酢酸を回収する方法では、酢酸濃度が高くなると膜の劣化が発生するため、酢酸濃度の適用範囲が限られ、運転効率として限定的であり、また、蒸留塔の運転条件に対する制約条件となる問題があった。 However, in the method of recovering using the extractant, the transfer of the extractant into the liquid recovered from the lower part of the distillation column (the bottoms) is ignored in order to separate the extracted liquid by distillation after the extraction operation. Loss of extractant occurs to the extent that it cannot be performed. Also, in the method of recovering acetic acid by membrane separation method, membrane degradation occurs when the acetic acid concentration becomes high, so the applicable range of acetic acid concentration is limited and the operating efficiency is limited, and the operating conditions of the distillation column There was a problem that became a constraint condition.
そこで本発明は、前記した問題を解決する効率的な酢酸の回収方法を提供するものである。 Accordingly, the present invention provides an efficient method for recovering acetic acid that solves the aforementioned problems.
上記した本発明の課題は、下記する発明により解決できる。すなわち、本発明は、以下の工程（Ｉ）〜（IV）をこの順で行う酢酸の回収方法、である。
（Ｉ）酢酸を含む水溶液からなる供給液（ａ）を蒸留し、残分として回収酢酸（ｂ）を得ると共に、留分として酢酸濃度１〜１０重量％の留出液（ｃ）を得る工程、
（II）工程（Ｉ）で得られた留出液（ｃ）に酢酸エステルを主成分とする抽剤（ｄ）を接触させ、抽出操作を行って、抽出液（ｅ）と抽残液（ｆ）とを得る工程、
（III）工程（II）で得られた抽出液（ｅ）、抽残液（ｆ）をそれぞれ蒸留し、抽剤（ｄ）および酢酸を回収するとともに、抽残液（ｆ）からの残分である残分（Ｉ）を得る工程、
（IV）工程（III）で得られた残分（Ｉ）を膜分離装置に供給し、水分の除去を行う工程
The above-described problems of the present invention can be solved by the following invention. That is, the present invention is an acetic acid recovery method in which the following steps (I) to (IV) are performed in this order.
(I) A step of distilling a feed liquid (a) comprising an aqueous solution containing acetic acid to obtain recovered acetic acid (b) as a residue and obtaining a distillate (c) having an acetic acid concentration of 1 to 10% by weight as a fraction. ,
(II) The extract (d) mainly composed of acetate is brought into contact with the distillate (c) obtained in the step (I), and an extraction operation is performed to extract the extract (e) and the residue ( f)
(III) The extract (e) and the extracted residue (f) obtained in step (II) are distilled to recover the extract (d) and acetic acid, and the residue from the extracted solution (f). Obtaining a residue (I) which is
(IV) A step of supplying the residue (I) obtained in the step (III) to a membrane separation device and removing moisture.
本発明に係る酢酸の回収方法によれば、効率的な酢酸の回収が可能となる。また、エネルギー的にも有利であり、膜の劣化なく排水中の酢酸濃度を大幅に削減でき、酢酸及び抽剤の回収率としても高い回収率とできる。 According to the acetic acid recovery method of the present invention, it is possible to efficiently recover acetic acid. In addition, it is advantageous in terms of energy, the concentration of acetic acid in the wastewater can be greatly reduced without deterioration of the membrane, and the recovery rate of acetic acid and extractant can be high.
以下に、本発明について、具体的な実施の形態とともにさらに詳細に説明する。しかし、本発明は以下に述べる例に限定して解釈されるものではない。 Hereinafter, the present invention will be described in more detail with specific embodiments. However, the present invention is not construed as being limited to the examples described below.
本発明に用いられる供給液（供給液（ａ））は、酢酸を含有した水溶液である。酢酸の濃度としては特に制限は無いが、酢酸の濃度は高い方が望ましく、供給液（ａ）の重量を１００重量％としたとき、酢酸を７０〜９０重量％程度、水を１０〜３０重量％程度含むものを用いることが、効率的な回収をはかることができ、好適である。また、供給液（ａ）にはその他の成分、例えば、酢酸エステルが０．１〜０．５重量％程度含有されていても構わない。 The supply liquid (supply liquid (a)) used in the present invention is an aqueous solution containing acetic acid. The concentration of acetic acid is not particularly limited, but it is desirable that the concentration of acetic acid is high. When the weight of the feed liquid (a) is 100% by weight, acetic acid is about 70 to 90% by weight and water is 10 to 30% by weight. It is preferable to use those containing about% because efficient recovery can be achieved. Further, the supply liquid (a) may contain about 0.1 to 0.5% by weight of other components, for example, acetate.
供給液は最初の工程（工程（Ｉ））として、蒸留工程に供される。この蒸留工程では留分（留出液（ｃ））として水を、残分（回収酢酸（ｂ））として酢酸を回収することを主たる目的として実行される。蒸留手段としては公知のものを用いることができる。好ましい段数と還流比としては、段数が２５〜４０段、還流比は２．７〜３．７である。残分に含まれる酢酸濃度は高い方が望ましいが、運転効率を考慮すれば８０〜９５％重量％とすることが望ましい。また、留出液（ｃ）においても酢酸は含まれることとなるが、留出液（ｃ）における酢酸の濃度は、１〜１０重量％とすることが望ましい。 The feed liquid is subjected to a distillation step as the first step (step (I)). This distillation step is performed mainly for the purpose of recovering water as a fraction (distillate (c)) and acetic acid as a residue (recovered acetic acid (b)). A known means can be used as the distillation means. The number of stages and the reflux ratio are preferably 25 to 40 stages and the reflux ratio is 2.7 to 3.7. The concentration of acetic acid contained in the residue is desirably higher, but it is preferably 80 to 95% by weight in consideration of operating efficiency. Moreover, although acetic acid will also be contained in the distillate (c), the concentration of acetic acid in the distillate (c) is preferably 1 to 10% by weight.
次に、留出液（ｃ）は、酢酸エステルを主成分とする抽剤（ｄ）を接触させ、抽出操作を行う工程（工程（II））に供される。 Next, the distillate (c) is subjected to an extraction operation (step (II)) by bringing the extractant (d) containing acetic ester as a main component into contact therewith.
工程（II）において用いる酢酸エステルとしては、酢酸メチル、酢酸エチル、酢酸プロピル、酢酸イソブチル、エチレングリコールモノメチルエーテルアセテート、エチレングリコールジアセテートなど公知の酢酸エステルを用いうるが、抽剤の回収率を高めることが可能であることから、酢酸メチルを用いることが好ましい。ここで、主成分とは抽剤（ｄ）の重量の８０重量％を占めることをいい、好ましくは、９０重量％以上を占めることをいう。抽剤（ｄ）の純度としては工業的グレードで構わない。また、本発明の目的を損なわないのであれば、水や酢酸が少量含まれていても構わない。抽出手段としては公知のものを用いることができ、連続的な抽出手段であっても、バッチ式の抽出手段であっても構わない。連続的な抽出手段の場合、段数が１０〜２０段で、抽剤と被抽出剤との比率である抽剤比（抽剤/被抽出剤）が、１．０〜２．０であることが好ましい。 As the acetate used in step (II), known acetates such as methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, and ethylene glycol diacetate can be used, but the recovery rate of the extractant is increased. Therefore, it is preferable to use methyl acetate. Here, the main component refers to occupying 80% by weight of the extractant (d), and preferably 90% by weight or more. The purity of the extractant (d) may be an industrial grade. Further, as long as the object of the present invention is not impaired, a small amount of water or acetic acid may be contained. Known extraction means can be used, and it may be a continuous extraction means or a batch type extraction means. In the case of continuous extraction means, the number of stages is 10 to 20, and the ratio of the extraction agent (extractant / extractable agent), which is the ratio of the extractant to the extractant, is 1.0 to 2.0. Is preferred.
また、本発明の実施の結果回収される抽剤分をそのまま、またはフィルタリングなどの清浄工程を通過させて工程（II）の抽剤として好ましく用いることができる。 Further, the extract collected as a result of the present invention can be preferably used as the extract in step (II) as it is or after passing through a cleaning process such as filtering.
この工程（II）においては、留出液（ｃ）に含まれた酢酸の多くは抽出液（抽出液（ｅ））側に移行する。また、通常は抽残液（抽残液（ｆ））にも幾らかの酢酸が含有されている。 In this step (II), most of acetic acid contained in the distillate (c) moves to the extract (extract (e)) side. In addition, some acetic acid is usually contained in the extraction residual liquid (extraction residual liquid (f)).
続いて、前記工程（II）において得られた、抽出液（ｅ）および抽残液（ｆ）は各々蒸留工程に供される（工程III）。 Subsequently, the extraction liquid (e) and the extraction residual liquid (f) obtained in the step (II) are each subjected to a distillation step (step III).
抽出液（ｅ）の蒸留においては、専ら、留分としての抽剤と残分としての酢酸の分離が行われる。用いる蒸留手段としては公知のものを用いることができ、好ましい段数と還流比としては、段数が１０〜２０段で、還流比は１．０〜２．０である。 In the distillation of the extract (e), the extractant as the fraction and the acetic acid as the residue are exclusively separated. As the distillation means to be used, known ones can be used. As the number of stages and the reflux ratio, the number of stages is 10 to 20 and the reflux ratio is 1.0 to 2.0.
抽残液（ｆ）の蒸留においては、専ら留分としての抽剤の回収が行われる。用いる蒸留手段としては公知のものを用いることができ、好ましい段数と還流比としては、段数が１０〜２０段で、還流比は１．０〜２．０である。 In the distillation of the extraction residual liquid (f), the extraction agent as a fraction is exclusively collected. As the distillation means to be used, known ones can be used. As the number of stages and the reflux ratio, the number of stages is 10 to 20 and the reflux ratio is 1.0 to 2.0.
この抽残液を蒸留しての残分（残分（Ｉ））には、抽剤と酢酸が少量ながら含まれているので、本発明においては、これを回収するべく、残分（Ｉ）を膜分離装置に供して濃縮を行う（工程IV）。用いうる膜分離装置としては公知のものを用いることができるが、分離膜としては、透過側に水が、濃縮側に抽剤に含まれる酢酸エステルと酢酸が、それぞれ分離されるものが使用され、このような分離が可能である分離膜としては逆浸透膜が使用できる。また、酢酸エステルと酢酸以外の成分、例えばアルコール、は透過側に分離されることが望ましい。 The residue obtained by distilling the extracted residue (residue (I)) contains a small amount of extractant and acetic acid. In the present invention, in order to recover this residue (I) Is subjected to concentration using a membrane separator (step IV). As the membrane separation apparatus that can be used, a known apparatus can be used. As the separation membrane, water that separates water on the permeate side and acetate and acetic acid contained in the extractant on the concentration side are used. As a separation membrane capable of such separation, a reverse osmosis membrane can be used. In addition, it is desirable that components other than acetic acid ester and acetic acid, such as alcohol, be separated on the permeate side.
工程（IV）を通過させることによって、濃縮側から酢酸と抽剤を濃縮しての回収をはかることができる。 By passing the step (IV), the acetic acid and the extractant can be concentrated and recovered from the concentration side.
以下、実施例により、本発明を具体的に説明するが、本発明は、これらの実施例により何ら限定を受けるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples.
（実施例１）
供給液として酢酸８１．２８重量％、水１８．４０重量％、酢酸メチル０．３０重量％、メタノール０．０２重量％の酢酸水溶液を使用し、脱水蒸留塔として段数２５段の棚段塔の２３段目に１００ｋｇ／ｈで供給し還流比２．７で連続蒸留を行った。得られた留出液１１．８ｋｇ／ｈの組成は、水９５．７６重量％、酢酸メチル２．５４重量％、酢酸１．５０重量％、メタノール０．１９重量％となり、缶出液（回収酢酸）８８．２ｋｇ／ｈの組成は、酢酸９１．９５重量％、水８．０５重量％となった。留出液は、段数１０段の抽出塔に供給し、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％の組成比である抽剤１３．８ｋｇ／ｈと抽剤比１．２で接触させた。得られた抽出液１３．８ｋｇ／ｈの組成は、酢酸メチル８２．９０重量％、水１５．８７重量％、酢酸１．０４重量％、メタノール０．２０重量％となり、抽残液１１．８ｋｇ／ｈの組成は、水８４．２２重量％、酢酸メチル１５．３０重量％、酢酸０．２８重量％、メタノール０．２０重量％となった。抽出液は、酢酸回収蒸留塔として段数１０段の棚段塔の４段目に供給し還流比１．０で連続蒸留を行った。得られた留出液（抽剤）１１．９ｋｇ／ｈの組成は、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％となり、缶出液（回収酢酸）１．９ｋｇ／ｈの組成は、水７７．６９重量％、酢酸７．５８重量％、酢酸メチル１４．５７重量％、メタノール０．１７重量％となった。抽残液は、抽剤回収蒸留塔として段数１０段の棚段塔の４段目に供給し還流比１．０で連続蒸留を行った。得られた留出液（抽剤）１．９ｋｇ／ｈの組成は、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％となり、缶出液（残分）９．９ｋｇ／ｈの組成は、水９９．２３重量％、酢酸０．３３重量％、酢酸メチル０．２３重量％、メタノール０．２０重量％となった。得られた缶出液（残分）は、膜分離装置に供給し、濃縮倍率５倍で膜分離を連続して行った。得られた透過液（排水）８．３ｋｇ／ｈの組成は、水９９．７０重量％、メタノール０．２２重量％、酢酸０．０６重量％、酢酸メチル０．０３重量％となり、濃縮液（回収酢酸）１．７ｋｇ／ｈの組成は、水９６．９１重量％、酢酸１．７０重量％、酢酸メチル１．２７重量％、メタノール０．１２重量％となった。その結果、酢酸回収率９９．９９重量％、抽剤回収率９９．２３重量％となった。
Example 1
An acetic acid aqueous solution of 81.28% by weight of acetic acid, 18.40% by weight of water, 0.30% by weight of methyl acetate, and 0.02% by weight of methanol was used as a feed liquid, and a 25-stage plate tower was used as a dehydration distillation column. In the 23rd stage, 100 kg / h was supplied, and continuous distillation was performed at a reflux ratio of 2.7. The composition of the obtained distillate 11.8 kg / h was 95.76% by weight of water, 2.54% by weight of methyl acetate, 1.50% by weight of acetic acid, and 0.19% by weight of methanol. The composition of 88.2 kg / h of acetic acid was 91.95% by weight acetic acid and 8.05% by weight water. The distillate was supplied to an extraction tower having 10 plates and extracted with 13.8 kg / h of an extractant having a composition ratio of 93.80% by weight of methyl acetate, 6.00% by weight of water and 0.20% by weight of methanol. Contact was made at an agent ratio of 1.2. The composition of the extract 13.8 kg / h obtained was 82.90% by weight of methyl acetate, 15.87% by weight of water, 1.04% by weight of acetic acid and 0.20% by weight of methanol. The composition of / h was 84.22% by weight of water, 15.30% by weight of methyl acetate, 0.28% by weight of acetic acid, and 0.20% by weight of methanol. The extract was supplied as the acetic acid recovery distillation column to the 4th stage of a 10-stage plate tower and subjected to continuous distillation at a reflux ratio of 1.0. The composition of the obtained distillate (extractant) 11.9 kg / h was 93.80% by weight of methyl acetate, 6.00% by weight of water, and 0.20% by weight of methanol. The composition of .9 kg / h was 77.69% by weight of water, 7.58% by weight of acetic acid, 14.57% by weight of methyl acetate, and 0.17% by weight of methanol. The extraction residue was supplied to the fourth stage of a 10-stage shelf tower as an extractant collection distillation tower, and subjected to continuous distillation at a reflux ratio of 1.0. The composition of the obtained distillate (extractant) 1.9 kg / h was 93.80% by weight of methyl acetate, 6.00% by weight of water, and 0.20% by weight of methanol. The composition of .9 kg / h was 99.23% by weight of water, 0.33% by weight of acetic acid, 0.23% by weight of methyl acetate, and 0.20% by weight of methanol. The resulting bottoms (residue) was supplied to a membrane separator, and membrane separation was continuously performed at a concentration factor of 5 times. The composition of the obtained permeate (drainage) 8.3 kg / h was 99.70% by weight of water, 0.22% by weight of methanol, 0.06% by weight of acetic acid, and 0.03% by weight of methyl acetate. The composition of the recovered acetic acid) 1.7 kg / h was 96.91 wt% water, 1.70 wt% acetic acid, 1.27 wt% methyl acetate, and 0.12 wt% methanol. As a result, the acetic acid recovery rate was 99.99% by weight and the extractant recovery rate was 99.23% by weight.
（比較例１）
供給液として酢酸８１．２８重量％、水１８．４０重量％、酢酸メチル０．３０重量％、メタノール０．０２重量％の酢酸水溶液を使用し、脱水蒸留塔として段数２５段の棚段塔の２３段目に１００ｋｇ／ｈで供給し還流比２．７で連続蒸留を行った。得られた留出液１１．８ｋｇ／ｈの組成は、水９５．７６重量％、酢酸メチル２．５４重量％、酢酸１．５０重量％、メタノール０．１９重量％となり、缶出液（回収酢酸）８８．２ｋｇ／ｈの組成は、酢酸９１．９５重量％、水８．０５重量％となった。留出液は、段数１０段の抽出塔に供給し、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％の組成比である抽剤１３．６ｋｇ／ｈと抽剤比１．２で接触させた。得られた抽出液１３．６ｋｇ／ｈの組成は、酢酸メチル８２．７１重量％、水１６．０４重量％、酢酸１．０６重量％、メタノール０．２０重量％となり、抽残液１１．８ｋｇ／ｈの組成は、水８４．２２重量％、酢酸メチル１５．３０重量％、酢酸０．２８重量％、メタノール０．２０重量％となった。抽出液は、酢酸回収蒸留塔として段数１０段の棚段塔の４段目に供給し還流比１．０で連続蒸留を行った。得られた留出液（抽剤）１１．７ｋｇ／ｈの組成は、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％となり、缶出液（回収酢酸）１．９ｋｇ／ｈの組成は、水７７．６９重量％、酢酸メチル１４．５７重量％、酢酸７．５８重量％、メタノール０．１７重量％となった。抽残液は、抽剤回収蒸留塔として段数１０段の棚段塔の４段目に供給し還流比１．０で連続蒸留を行った。得られた留出液（抽剤）１．９ｋｇ／ｈの組成は、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％となり、缶出液（残分）９．９ｋｇ／ｈの組成は、水９９．２３重量％、酢酸０．３３％、酢酸メチル０．２３重量％、メタノール０．２０重量％となった。その結果、酢酸回収率９９．９６重量％、抽剤回収率９２．２７重量％となった。
(Comparative Example 1)
An acetic acid aqueous solution of 81.28% by weight of acetic acid, 18.40% by weight of water, 0.30% by weight of methyl acetate, and 0.02% by weight of methanol was used as a feed liquid, and a 25-stage plate tower was used as a dehydration distillation column. In the 23rd stage, 100 kg / h was supplied, and continuous distillation was performed at a reflux ratio of 2.7. The composition of the obtained distillate 11.8 kg / h was 95.76% by weight of water, 2.54% by weight of methyl acetate, 1.50% by weight of acetic acid, and 0.19% by weight of methanol. The composition of 88.2 kg / h of acetic acid was 91.95% by weight acetic acid and 8.05% by weight water. The distillate was supplied to an extraction tower having 10 plates, and the extract was 13.6 kg / h of extractant having a composition ratio of 93.80% by weight of methyl acetate, 6.00% by weight of water, and 0.20% by weight of methanol. Contact was made at an agent ratio of 1.2. The composition of the obtained extract 13.6 kg / h was 82.71% by weight of methyl acetate, 16.04% by weight of water, 1.06% by weight of acetic acid and 0.20% by weight of methanol. The composition of / h was 84.22% by weight of water, 15.30% by weight of methyl acetate, 0.28% by weight of acetic acid, and 0.20% by weight of methanol. The extract was supplied as the acetic acid recovery distillation column to the 4th stage of a 10-stage plate tower and subjected to continuous distillation at a reflux ratio of 1.0. The composition of the obtained distillate (extractant) 11.7 kg / h was 93.80% by weight of methyl acetate, 6.00% by weight of water and 0.20% by weight of methanol. The composition of .9 kg / h was 77.69% by weight of water, 14.57% by weight of methyl acetate, 7.58% by weight of acetic acid, and 0.17% by weight of methanol. The extraction residue was supplied to the fourth stage of a 10-stage shelf tower as an extractant collection distillation tower, and subjected to continuous distillation at a reflux ratio of 1.0. The composition of the obtained distillate (extractant) 1.9 kg / h was 93.80% by weight of methyl acetate, 6.00% by weight of water, and 0.20% by weight of methanol. The composition of .9 kg / h was 99.23% by weight of water, 0.33% of acetic acid, 0.23% by weight of methyl acetate, and 0.20% by weight of methanol. As a result, the acetic acid recovery rate was 99.96% by weight, and the extractant recovery rate was 92.27% by weight.
（比較例２）
供給液として酢酸８１．２８重量％、水１８．４０重量％、酢酸メチル０．３０重量％、メタノール０．０２重量％の酢酸水溶液を使用し、脱水蒸留塔として段数２５段の棚段塔の２３段目に１００ｋｇ／ｈで供給し還流比２．７で連続蒸留を行った。得られた留出液１１．８ｋｇ／ｈの組成は、水９５．７６重量％、酢酸メチル２．５４重量％、酢酸１．５０重量％、メタノール０．１９重量％となり、缶出液（回収酢酸）８８．２ｋｇ／ｈの組成は、酢酸９１．９５重量％、水８．０５重量％となった。留出液は、酢酸回収蒸留塔として段数１０段の棚段塔の４段目に供給し還流比１．０で連続蒸留を行った。得られた留出液（回収酢酸メチル）０．３ｋｇ／ｈの組成は、酢酸メチル９３．８０重量％、水６．００重量％、メタノール０．２０重量％となり、缶出液（排水）１１．５ｋｇ／ｈの組成は、水９８．１０重量％、酢酸１．５４重量％、メタノール０．１９重量％、酢酸メチル０．１６重量％となった。得られた缶出液（排水）は、膜分離装置に供給し、濃縮倍率５倍で膜分離を連続して行った。得られた透過液（排水）９．６ｋｇ／ｈの組成は、水９９．４９重量％、酢酸０．２８重量％、メタノール０．２１重量％、酢酸メチル０．０２重量％となり、濃縮液（回収酢酸）１．９ｋｇ／ｈの組成は、水９１．１６重量％、酢酸７．８５重量％、酢酸メチル０．８７重量％、メタノール０．１２重量％となった。その結果、酢酸回収率９９．９７重量％、抽剤回収率９９．３８重量％となった。
(Comparative Example 2)
An acetic acid aqueous solution of 81.28% by weight of acetic acid, 18.40% by weight of water, 0.30% by weight of methyl acetate, and 0.02% by weight of methanol was used as a feed liquid, and a 25-stage plate tower was used as a dehydration distillation column. In the 23rd stage, 100 kg / h was supplied, and continuous distillation was performed at a reflux ratio of 2.7. The composition of the obtained distillate 11.8 kg / h was 95.76% by weight of water, 2.54% by weight of methyl acetate, 1.50% by weight of acetic acid, and 0.19% by weight of methanol. The composition of 88.2 kg / h of acetic acid was 91.95% by weight acetic acid and 8.05% by weight water. The distillate was supplied to the fourth stage of a 10-stage shelf tower as an acetic acid recovery distillation tower and subjected to continuous distillation at a reflux ratio of 1.0. The composition of the obtained distillate (recovered methyl acetate) 0.3 kg / h was 93.80% by weight methyl acetate, 6.00% by weight water, and 0.20% by weight methanol. The composition of 0.5 kg / h was 98.10 wt% water, 1.54 wt% acetic acid, 0.19 wt% methanol, and 0.16 wt% methyl acetate. The resulting bottoms (drainage) was supplied to a membrane separator, and membrane separation was continuously performed at a concentration factor of 5 times. The composition of the obtained permeate (drainage) 9.6 kg / h was 99.49 wt% water, 0.28 wt% acetic acid, 0.21 wt% methanol, and 0.02 wt% methyl acetate. The composition of 1.9 kg / h of recovered acetic acid was 91.16% by weight of water, 7.85% by weight of acetic acid, 0.87% by weight of methyl acetate, and 0.12% by weight of methanol. As a result, the acetic acid recovery rate was 99.97% by weight and the extractant recovery rate was 99.38% by weight.
本発明に係る方法は、本発明に係る酢酸回収方法によれば、蒸留と抽出、膜分離を組み合わせることで効率的に抽剤及び酢酸回収が可能となり、酢酸を溶媒としたテレフタル酸の製造等、反応後に酢酸水溶液から酢酸を分離回収する工程等に極めて好適に適用できる。 According to the acetic acid recovery method according to the present invention, the method according to the present invention enables efficient extraction and extraction of acetic acid by combining distillation, extraction, and membrane separation. Production of terephthalic acid using acetic acid as a solvent, etc. The present invention can be applied to a process of separating and recovering acetic acid from an aqueous acetic acid solution after the reaction.
１：脱水蒸留塔
２：リボイラ
３：コンデンサ
４：抽出塔
５：抽剤回収蒸留塔
６：酢酸回収蒸留塔
７：抽剤受槽
８：コンデンサ
９：冷却器
１０：膜分離装置
（ａ）：供給液
（ｂ）：回収酢酸
（ｃ）：留出液
（ｄ）：抽剤
（ｅ）：抽出液
（ｆ）：抽残液
（ｇ）：回収抽剤
（ｈ）：回収酢酸
（ｉ）：回収抽剤
（ｊ）：残分
（ｋ）：濃縮液
（ｌ）：透過液
1: dehydration distillation column 2: reboiler 3: condenser 4: extraction column 5: extractant recovery distillation column 6: acetic acid recovery distillation column 7: extractant receiving tank 8: condenser 9: cooler 10: membrane separator (a): supply Liquid (b): Recovered acetic acid (c): Distillate (d): Extractant (e): Extraction liquid (f): Extraction residual liquid (g): Recovered extract (h): Recovered acetic acid (i): Collected extract (j): residue (k): concentrate (l): permeate
Claims (3)
（Ｉ）酢酸を含む水溶液からなる供給液（ａ）を蒸留し、残分として回収酢酸（ｂ）を得ると共に、留分として酢酸濃度１〜１０重量％の留出液（ｃ）を得る工程、
（II）工程（Ｉ）で得られた留出液（ｃ）に酢酸エステルを主成分とする抽剤（ｄ）を接触させ、抽出操作を行って、抽出液（ｅ）と抽残液（ｆ）とを得る工程、
（III）工程（II）で得られた抽出液（ｅ）、抽残液（ｆ）をそれぞれ蒸留し、抽剤（ｄ）および酢酸を回収するとともに、抽残液（ｆ）からの残分である残分（Ｉ）を得る工程、
（IV）工程（III）で得られた残分（Ｉ）を膜分離装置に供給し、水分の除去を行う工程 A method for recovering acetic acid, wherein the following steps (I) to (IV) are carried out in this order.
(I) A step of distilling a feed liquid (a) comprising an aqueous solution containing acetic acid to obtain recovered acetic acid (b) as a residue and obtaining a distillate (c) having an acetic acid concentration of 1 to 10% by weight as a fraction. ,
(II) The extract (d) mainly composed of acetate is brought into contact with the distillate (c) obtained in the step (I), and an extraction operation is performed to extract the extract (e) and the residue ( f)
(III) The extract (e) and the extracted residue (f) obtained in step (II) are distilled to recover the extract (d) and acetic acid, and the residue from the extracted solution (f). Obtaining a residue (I) which is
(IV) A step of supplying the residue (I) obtained in the step (III) to a membrane separation device and removing moisture.
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| CN115413276A (en) * | 2020-03-31 | 2022-11-29 | 株式会社大赛璐 | Preparation method of purified acetic acid |
| CN115413276B (en) * | 2020-03-31 | 2024-04-02 | 株式会社大赛璐 | Preparation method of purified acetic acid |
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