JP4000912B2 - Method for producing dimethyl carbonate - Google Patents

Description

【００１３】
＜第１工程（Ａ）＞
先ず、ＥＣとＭｅＯＨとをエステル交換反応させ、ＭｅＯＨ、ＤＭＣ、ＥＧ及びＥＣ含む反応混合物を得る。なお、ＥＣとＭｅＯＨとのエステル交換反応は以下の化学反応式（１）で示される。
【００１４】
【化１】

【００１５】
上記のエステル交換反応は平衡反応であり、反応液中には必ず未反応の原料成分が存在する。すなわち、反応液中には、生成物のＤＭＣ及びＥＧの他に、原料のＥＣ及びＭｅＯＨが含まれ、更に、副生したＤＭＥ等が含まれている。
【００１６】
通常、上記のエステル交換反応は触媒の存在下に行なわれる。触媒としては、カーボネート類のエステル交換触媒として一般的に使用されているものを制限なく使用することが出来る。具体的には、均一系触媒として、トリエチルアミン等のアミン類、ナトリウム等のアルカリ金属、クロロ酢酸ナトリウム、ナトリウムメチラート等のアルカリ金属化合物、タリウム化合物などが挙げられ、不均一系触媒として、官能基により変性したイオン交換樹脂、アルカリ金属またはアルカリ土類金属の珪酸塩を含浸した無定型シリカ類、アンモニウム交換Ｙ型ゼオライト、コバルトとニッケルとの混合酸化物などが挙げられる。
【００１７】
反応器の形式は、特に限定されないが、固定床式反応器（具体的には管状リアクター）を使用するのが好ましい。反応は連続的に行なうのが好ましく、ＥＣに対するＭｅＯＨの使用割合（モル比）は通常２〜２０であり、反応温度は通常５０〜１８０℃、反応時間は通常０．５〜５時間である。
【００１８】
図示した例の場合、ＥＣ及びＭｅＯＨは、それぞれ、ライン（Ｌ１）及びライン（Ｌ２）から第１工程（Ａ）に供給され、反応液はライン（Ｌ３）から取り出される。
【００１９】
＜第２工程（Ｂ）＞
次いで、抽出溶媒としてのＥＣの存在下、第１工程で得た反応混合物を抽出蒸留してＭｅＯＨを分離し、第１工程に反応原料として循環する。反応混合物中のＭｅＯＨとＤＭＣとは最低共沸混合物を形成する。因に、常圧での共沸組成はＭｅＯＨが約６５重量％である。そこで、本発明においては、抽出溶媒としてＥＣを添加し、上記の共沸組成を目的とするＭｅＯＨの純度に対応するリッチサイドにずらして蒸留を行なう。
【００２０】
第２工程（Ｂ）で分離回収するＭｅＯＨの純度は、通常８５重量％以上、好ましくは９０重量％以上である。従って、第２工程（Ｂ）における蒸留塔の濃縮段および回収段の段数、操作条件（温度、圧力、還流比など）は、上記の成分分離が行なわれる様に適宜選択される。
【００２１】
反応液から原料を除去すると生成物のＤＭＣとＥＧとによりエステル交換反応の逆反応を起こす可能性がある。そこで、第２工程の処理温度は、通常１５０〜１８０℃、好ましくは１５０〜１７０℃とされる。また、滞留時間も可能な限り短くするのがよく、１５０℃以上に保持される滞留時間は１時間以下とするのがよい。
【００２２】
図示した例の場合、第１工程で得た反応混合物はライン（Ｌ３）から第２工程（Ｂ）に供給され、後述の第４工程（Ｄ）で回収されたＥＣはライン（Ｌ８ｂ）から第２工程（Ｂ）に供給される。そして、分離回収されたＭｅＯＨはライン（Ｌ４）を通して第１工程（Ａ）に循環され、ＭｅＯＨを分離した残余の高沸点留分はライン（Ｌ５）を通して回収される。
【００２３】
＜第３工程（Ｃ）＞
次いで、第２工程で回収した高沸点留分から目的成分であるＤＭＣを蒸留分離する。第３工程（Ｃ）で分離回収するＤＭＣの純度は、通常９５重量％以上、好ましくは９８重量％以上である。第３工程（Ｃ）における蒸留塔の濃縮段および回収段の段数、操作条件（温度、圧力、還流比など）は、上記の成分分離が行なわれる様に適宜選択される。
【００２４】
第２工程で回収した高沸点留分には、ＥＧが含まれており、これがＤＭＣと第１工程におけるエステル交換反応の逆反応を起こす可能性がある。そこで、第３工程の処理温度は、通常１５０〜１８０℃、好ましくは１５０〜１７０℃とされる。また、滞留時間も可能な限り短くするのがよく、１５０℃以上に保持される滞留時間は１時間以下とするのがよい。
【００２５】
なお、上記の逆反応の進行によりＤＭＣ中にＭｅＯＨが混入してくるが、ＤＭＣをフェノールとエステル交換させてポリカーボネート原料であるジフェニルカーボネートを製造する場合、反応によりＭｅＯＨが生成する。従って、回収されたＤＭＣに含まれる少量のＭｅＯＨは、ＤＭＣとフェノールのエステル交換反応によるジフェニルカーボネート（ＤＰＣ）生成反応で副生するＭｅＯＨと共に処理できるため、本発明の製造方法で得られるＤＭＣは、ＤＰＣの原料として使用可能である。
【００２６】
図示した例の場合、第２工程で回収した高沸点留分は、ライン（Ｌ５）から第３工程（Ｃ）に供給され、分離されたＤＭＣはライン（Ｌ６）を通して回収され、ＤＭＣを分離した残余の高沸点留分はライン（Ｌ７）を通して回収される。
【００２７】
＜第４工程（Ｄ）＞
次いで、第３工程で回収した高沸点留分からＥＣを分離し、第１工程に反応原料として循環すると共に第２工程に抽出溶媒として循環する。第４工程（Ｄ）で分離回収するＥＣの純度は、通常８５重量％以上、好ましくは９０重量％以上である。上記の循環用ＥＣは、通常、蒸留塔の側部からサイドカットとして回収される。すなわち、上記の循環用ＥＣは、塔頂からＥＧ留分を分離し、塔底からＴＥＧ、ＰＥＧ等の高沸点生成物留分を分離することにより回収される。従って、第４工程（Ｄ）における蒸留塔の濃縮段および回収段の段数、操作条件（温度、圧力、還流比など）は、上記の成分分離が行なわれる様に適宜選択される。
【００２８】
ＥＧとＥＣは共沸混合物を形成するが、常圧ないし７ＫＰａ程度の減圧の領域では明確な最低沸点を示さず、最低沸点は、エチレングリコールの沸点と一致する。従って、通常の蒸留分離により、塔頂からＥＧとＥＣの混合物、塔底からＥＣが得られる。
【００２９】
図示した例の場合、第３工程で回収した高沸点留分はライン（Ｌ７）から第４工程（Ｄ）に供給され、上記の循環用ＥＣは、ライン（Ｌ８）からの分岐ライン（Ｌ８ａ）及び（Ｌ８ｂ）を通してそれぞれ第１工程（Ａ）及び第２工程（Ｂ）に循環される。そして、ＥＧ留分はライン（Ｌ９）を通して回収され、ＴＥＧ、ＰＥＧ等の高沸点生成物留分はライン（Ｌ１０）を通して回収される。
【００３０】
本発明において、第４工程で分離したＥＣの第１工程および第２工程に循環する比率は、第１工程 ３０〜８０重量％（好ましくは５０〜７０重量％）、第２工程２０〜７０重量％（好ましくは３０〜５０重量％）（両工程での合計１００重量％）とするのがよい。斯かる物質収支によれば、ＥＣを利用した前述の抽出蒸留とＥＣのエステル交換反応への再利用とをバランス良く両立させることが出来る。第２工程へのＥＣ分配率が２０％未満の場合は抽出蒸留の機能を果たすことが出来ず、７０％を超える場合は第４工程におけるＥＣ分離エネルギーが多くなってエネルギーの損失となる。
【００３１】
前記の各蒸留塔の形式は、棚段塔または充填塔の何れの形式であってもよい。棚段塔としては、シーブトレイ、泡鐘塔などの公知の型式を使用することが出来る。充填塔における充填物としては、スルザーパック、メラパック、ＭＣパック等の規則充填物、ＩＭＴＰ、ラシヒリング等の不規則充填物を使用することが出来る。因に、各蒸留塔の理論段数は、通常５〜３０段、好ましくは７〜２０段であり、還流比は、通常０．１〜５、好ましくは０．５〜２である。なお、各蒸留塔に設置される凝縮器としては一般的な多管式熱交換器を使用することが出来る。
【００３２】
【実施例】
以下、本発明を実施例により更に詳細に説明するが、本発明は、その要旨を超えない限り、以下の実施例に限定されるものではない。
【００３３】
実施例１
以下に記載の第１工程〜第４工程を順次に行なった。
【００３４】
＜第１工程＞
反応器として、多孔質アルミナ粒子に酸化ビスマスを担持した触媒が充填された固定床反応器（直径５１ｃｍ、高さ１５２ｃｍ）を使用した。ＭｅＯＨ：９ｋｇ／ｈ及びＥＣ：１５ｋｇ／ｈと共に後述する操作により回収されたＭｅＯＨおよびＥＣを１４０℃に加熱して固定床反応器に連続的に供給してエステル交換反応を行なった。反応圧力は１４００ＫＰａ、ＬＨＳＶは０．３３とした。得られた反応液の組成は、ＥＣ：５９重量％、ＭｅＯＨ：２０重量％、ＥＧ：１０重量％、ＤＭＣ：１２重量％であった。
【００３５】
＜第２工程＞
蒸留塔として理論段数１９段の充填塔を使用した。そして、第１０段目に反応液を供給し、第２段目に第４工程で回収したＥＣ（回収量の３０重量％相当量）を供給し、塔頂圧力１０１ＫＰａ、還流比０．９３で抽出蒸留を行なった。塔頂留出液量は２５ｋｇ／ｈであり、その組成は、ＭｅＯＨ：９３重量％、ＤＭＣ：７重量％であり、微量のＥＧを含んでいた。一方、塔底缶出液流量は１２１ｋｇ／ｈであり、その組成は、ＥＣ：７９重量％、ＥＧ：１１重量％、ＭｅＯＨ：０．２重量％であった。
【００３６】
＜第３工程＞
蒸留塔として理論段数２１段の充填塔を使用した。そして、第１０段目に第２工程で回収した高沸点留分（塔底缶出液）を供給し、塔頂圧力１６ＫＰａ、還流比１で蒸留を行なった。塔頂留出液量は１２ｋｇ／ｈであり、その組成は、ＤＭＣ：９８重量％、ＭｅＯＨ：２重量％であった。一方、塔底缶出液流量は１０９ｋｇ／ｈであり、その組成は、ＥＣ：８８重量％、ＥＧ：１２重量％であり、ＤＭＣ含量は１０重量ｐｐｍ以下であった。
【００３７】
＜第４工程＞
蒸留塔として理論段数１９段の充填塔を使用した。そして、第１１段目に第３工程で回収した高沸点留分（塔底缶出液）を供給し、第１７段目からサイドカットを行ないつつ、塔頂圧力８ＫＰａ、還流比１で蒸留を行なった。塔頂留出液量は塔頂留出液量は１０ｋｇ／ｈであり、その組成は、ＥＧ：８３重量％、ＥＣ：１７重量％であった。一方、塔底缶出液流量は１ｋｇ／ｈであり、その組成は、ＴＥＧ、ＰＥＧ等の高沸点生成物であった。また、サイドカット液の液量は９８ｋｇ／ｈであり、その組成は、ＥＣ：９５．４重量％、ＥＧ：４．６重量％であった。そして、サイドカット液の７０重量％を反応原料として第１工程に循環し、３０重量％を第２工程に抽出溶媒として循環した。
【００３８】
以上の操作を連続的に行なった結果、ＥＣの転化率８９％でＤＭＣ：１２ｋｈ／ｈとＥＧ８ｋｇ／ｈを得ることが出来た。
【００３９】
【発明の効果】
以上説明した本発明によれば、外部からの第三成分の取り込みもないために通常の精製プロセスを採用することが出来、しかも、未反応原料を効率的に再利用することが出来る、工業的に有利なジメチルカーボネートの製造方法が提供される。
【図面の簡単な説明】
【図１】本発明の好ましい態様の一例を示すプロセス概念図
【符号の説明】
Ａ：第１工程
Ｂ：第２工程
Ｃ：第３工程
Ｄ：第４工程[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing dimethyl carbonate, and more particularly, to an industrially advantageous method for producing dimethyl carbonate employing a transesterification reaction.
[0002]
[Prior art]
In the production of dimethyl carbonate by transesterification of ethylene carbonate and methanol, the reaction is an equilibrium reaction, so that unreacted raw materials remain in the reaction solution. Therefore, in an industrial process, it is important how efficiently unreacted raw materials are recovered from a reaction mixture and recycled.
[0003]
[Problems to be solved by the invention]
This invention is made | formed in view of the said situation, The objective is to provide the manufacturing method of industrially advantageous dimethyl carbonate by transesterification with ethylene carbonate and methanol.
[0004]
[Means for Solving the Problems]
As a result of intensive studies, the present inventor has obtained the following knowledge. That is, the recovered unreacted ethylene carbonate is skillfully used, and a part thereof is used as an extraction solvent for extractive distillation of unreacted methanol, which is difficult to separate to form a minimum azeotropic mixture with dimethyl carbonate, If the remaining ethylene carbonate is recycled as a raw material for the transesterification reaction with the recovered unreacted methanol, a normal purification process can be adopted because there is no external third component incorporation. The unreacted raw material can be efficiently reused, which is industrially advantageous.
[0005]
This invention is completed based on said knowledge, The summary exists in the manufacturing method of the dimethyl carbonate characterized by including the following 1st processes-4th processes sequentially.
[0006]
<First step>
Ethylene carbonate and methanol are transesterified to obtain a reaction mixture containing methanol, dimethyl carbonate, ethylene glycol and ethylene carbonate.
[0007]
<Second step>
In the presence of ethylene carbonate as an extraction solvent, the reaction mixture obtained in the first step is subjected to extractive distillation to separate methanol and circulated as a reaction raw material in the first step.
[0008]
<Third step>
Dimethyl carbonate is distilled off from the high-boiling fraction recovered in the second step.
[0009]
<4th process>
Ethylene carbonate is separated from the high-boiling fraction recovered in the third step and circulated as a reaction raw material in the first step and circulated as an extraction solvent in the second step.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a process conceptual diagram showing an example of a preferred embodiment of the present invention.
[0011]
The production method of the present invention sequentially includes the following first to fourth steps. In the following description, the abbreviations shown in the following Table 1 may be used.
[0012]
[Table 1]

[0013]
<First step (A)>
First, EC and MeOH are transesterified to obtain a reaction mixture containing MeOH, DMC, EG and EC. The transesterification reaction between EC and MeOH is represented by the following chemical reaction formula (1).
[0014]
[Chemical 1]

[0015]
The transesterification reaction is an equilibrium reaction, and unreacted raw material components always exist in the reaction solution. That is, the reaction liquid contains raw material EC and MeOH in addition to the product DMC and EG, and further contains by-produced DME and the like.
[0016]
Usually, the transesterification reaction is carried out in the presence of a catalyst. As a catalyst, what is generally used as a transesterification catalyst of carbonates can be used without limitation. Specifically, examples of the homogeneous catalyst include amines such as triethylamine, alkali metals such as sodium, alkali metal compounds such as sodium chloroacetate and sodium methylate, and thallium compounds, and heterogeneous catalysts include functional groups. Ion-exchange resin modified by the above, amorphous silica impregnated with an alkali metal or alkaline earth metal silicate, ammonium-exchanged Y-type zeolite, mixed oxide of cobalt and nickel, and the like.
[0017]
The type of the reactor is not particularly limited, but it is preferable to use a fixed bed reactor (specifically, a tubular reactor). The reaction is preferably carried out continuously, the use ratio (molar ratio) of MeOH to EC is usually 2 to 20, the reaction temperature is usually 50 to 180 ° C., and the reaction time is usually 0.5 to 5 hours.
[0018]
In the case of the illustrated example, EC and MeOH are supplied to the first step (A) from the line (L1) and the line (L2), respectively, and the reaction solution is taken out from the line (L3).
[0019]
<Second step (B)>
Next, in the presence of EC as an extraction solvent, the reaction mixture obtained in the first step is subjected to extractive distillation to separate MeOH and recycled to the first step as a reaction raw material. MeOH and DMC in the reaction mixture form a minimum azeotrope. Incidentally, the azeotropic composition at normal pressure is about 65% by weight of MeOH. Therefore, in the present invention, EC is added as an extraction solvent, and distillation is performed while shifting to the rich side corresponding to the purity of MeOH for the above azeotropic composition.
[0020]
The purity of MeOH separated and recovered in the second step (B) is usually 85% by weight or more, preferably 90% by weight or more. Accordingly, the number of concentration stages and recovery stages of the distillation column and the operating conditions (temperature, pressure, reflux ratio, etc.) in the second step (B) are appropriately selected so that the above component separation is performed.
[0021]
If the raw material is removed from the reaction solution, the product DMC and EG may cause a reverse reaction of the transesterification reaction. Therefore, the treatment temperature in the second step is usually 150 to 180 ° C, preferably 150 to 170 ° C. The residence time should be as short as possible, and the residence time maintained at 150 ° C. or higher is preferably 1 hour or less.
[0022]
In the case of the illustrated example, the reaction mixture obtained in the first step is supplied from the line (L3) to the second step (B), and the EC recovered in the fourth step (D) described later is supplied from the line (L8b) to the second step (B). It is supplied to 2 steps (B). The separated and recovered MeOH is circulated through the line (L4) to the first step (A), and the remaining high-boiling fraction from which MeOH has been separated is recovered through the line (L5).
[0023]
<Third step (C)>
Next, DMC as the target component is distilled and separated from the high-boiling fraction recovered in the second step. The purity of DMC separated and recovered in the third step (C) is usually 95% by weight or more, preferably 98% by weight or more. The number of concentration stages and recovery stages of the distillation column and the operating conditions (temperature, pressure, reflux ratio, etc.) in the third step (C) are appropriately selected so that the above component separation is performed.
[0024]
The high boiling point fraction recovered in the second step contains EG, which may cause a reverse reaction of DMC and the transesterification reaction in the first step. Therefore, the treatment temperature in the third step is usually 150 to 180 ° C., preferably 150 to 170 ° C. The residence time should be as short as possible, and the residence time maintained at 150 ° C. or higher is preferably 1 hour or less.
[0025]
Note that MeOH is mixed in DMC as the reverse reaction proceeds. However, when DMC is transesterified with phenol to produce diphenyl carbonate, which is a polycarbonate raw material, MeOH is generated by the reaction. Therefore, since a small amount of MeOH contained in the recovered DMC can be treated together with MeOH produced as a by-product in the diphenyl carbonate (DPC) formation reaction by transesterification of DMC and phenol, the DMC obtained by the production method of the present invention is It can be used as a raw material for DPC.
[0026]
In the case of the illustrated example, the high boiling fraction recovered in the second step is supplied from the line (L5) to the third step (C), and the separated DMC is recovered through the line (L6) to separate the DMC. The remaining high-boiling fraction is recovered through line (L7).
[0027]
<4th process (D)>
Next, EC is separated from the high-boiling fraction recovered in the third step and circulated as a reaction raw material in the first step and circulated as an extraction solvent in the second step. The purity of the EC separated and recovered in the fourth step (D) is usually 85% by weight or more, preferably 90% by weight or more. The above circulating EC is usually collected as a side cut from the side of the distillation column. That is, the above-mentioned EC for circulation is recovered by separating the EG fraction from the top of the column and separating the high boiling point product fraction such as TEG and PEG from the bottom of the column. Therefore, the number of concentration stages and recovery stages of the distillation column and the operating conditions (temperature, pressure, reflux ratio, etc.) in the fourth step (D) are appropriately selected so that the above component separation is performed.
[0028]
EG and EC form an azeotrope, but do not show a clear minimum boiling point in the region of normal pressure to about 7 KPa, and the lowest boiling point matches the boiling point of ethylene glycol. Therefore, a mixture of EG and EC is obtained from the top of the column and EC is obtained from the bottom of the column by ordinary distillation separation.
[0029]
In the case of the illustrated example, the high-boiling fraction recovered in the third step is supplied from the line (L7) to the fourth step (D), and the above circulating EC is connected to the branch line (L8a) from the line (L8). And (L8b) are circulated to the first step (A) and the second step (B), respectively. And an EG fraction is collect | recovered through a line (L9), and high boiling-point product fractions, such as TEG and PEG, are collect | recovered through a line (L10).
[0030]
In the present invention, the ratio of the EC separated in the fourth step to the first step and the second step is 30 to 80% by weight (preferably 50 to 70% by weight) in the first step, and 20 to 70% in the second step. % (Preferably 30 to 50% by weight) (total 100% by weight in both steps). According to such a mass balance, the above-described extractive distillation using EC and the reuse of EC for transesterification can be balanced. When the EC distribution ratio to the second step is less than 20%, the function of extractive distillation cannot be achieved, and when it exceeds 70%, the EC separation energy in the fourth step increases, resulting in energy loss.
[0031]
The form of each of the distillation towers may be either a plate tower or a packed tower. As the plate tower, a known type such as a sieve tray or a bubble bell tower can be used. As the packing in the packed tower, regular packing such as sulzer pack, mela pack and MC pack, and irregular packing such as IMTP and Raschig ring can be used. Incidentally, the theoretical plate number of each distillation column is usually 5 to 30 plate, preferably 7 to 20 plate, and the reflux ratio is usually 0.1 to 5, preferably 0.5 to 2. In addition, as a condenser installed in each distillation column, a general multi-tube heat exchanger can be used.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.
[0033]
Example 1
The first to fourth steps described below were sequentially performed.
[0034]
<First step>
As the reactor, a fixed bed reactor (diameter 51 cm, height 152 cm) in which porous alumina particles were loaded with a catalyst supporting bismuth oxide was used. MeOH and EC recovered by the operation described later together with MeOH: 9 kg / h and EC: 15 kg / h were heated to 140 ° C. and continuously supplied to a fixed bed reactor to perform a transesterification reaction. The reaction pressure was 1400 KPa and LHSV was 0.33. The composition of the obtained reaction solution was EC: 59% by weight, MeOH: 20% by weight, EG: 10% by weight, and DMC: 12% by weight.
[0035]
<Second step>
A packed column having 19 theoretical plates was used as a distillation column. Then, the reaction liquid is supplied to the 10th stage, EC (corresponding to 30% by weight of the recovered amount) recovered in the 4th process is supplied to the 2nd stage, and the top pressure is 101 KPa and the reflux ratio is 0.93. Extractive distillation was performed. The amount of the top distillate was 25 kg / h, and its composition was MeOH: 93% by weight, DMC: 7% by weight, and contained a trace amount of EG. On the other hand, the bottom bottom flow rate was 121 kg / h, and the composition was EC: 79% by weight, EG: 11% by weight, and MeOH: 0.2% by weight.
[0036]
<Third step>
A packed column having 21 theoretical plates was used as a distillation column. And the high boiling point fraction (column bottom bottoms liquid) collect | recovered at the 2nd process was supplied to the 10th stage, and distillation was performed by tower top pressure 16KPa and the reflux ratio 1. The amount of distillate at the top of the column was 12 kg / h, and the composition was DMC: 98% by weight and MeOH: 2% by weight. On the other hand, the bottom bottom flow rate was 109 kg / h, the composition was EC: 88 wt%, EG: 12 wt%, and the DMC content was 10 ppm by weight or less.
[0037]
<4th process>
A packed column having 19 theoretical plates was used as a distillation column. Then, the high-boiling fraction recovered in the third step (the bottom bottom effluent) is supplied to the eleventh stage, and distillation is performed at a tower top pressure of 8 KPa and a reflux ratio of 1 while performing a side cut from the 17th stage. I did it. The amount of the column top distillate was 10 kg / h, and the composition thereof was EG: 83% by weight and EC: 17% by weight. On the other hand, the flow rate at the bottom of the bottom was 1 kg / h, and its composition was a high-boiling product such as TEG or PEG. Moreover, the liquid quantity of the side cut liquid was 98 kg / h, and the composition was EC: 95.4 weight% and EG: 4.6 weight%. Then, 70% by weight of the side cut solution was circulated as a reaction raw material in the first step, and 30% by weight was circulated in the second step as an extraction solvent.
[0038]
As a result of continuously performing the above operation, DMC: 12 kh / h and EG 8 kg / h could be obtained at an EC conversion rate of 89%.
[0039]
【The invention's effect】
According to the present invention described above, a normal purification process can be employed because there is no external third component incorporation, and unreacted raw materials can be efficiently reused. An advantageous process for producing dimethyl carbonate is provided.
[Brief description of the drawings]
FIG. 1 is a process conceptual diagram showing an example of a preferred embodiment of the present invention.
A: 1st process B: 2nd process C: 3rd process D: 4th process

Claims (2)

The manufacturing method of the dimethyl carbonate characterized by including the following 1st processes-4th processes sequentially.
<First step>
Ethylene carbonate and methanol are transesterified to obtain a reaction mixture containing methanol, dimethyl carbonate, ethylene glycol and ethylene carbonate.
<Second step>
In the presence of ethylene carbonate as an extraction solvent, the reaction mixture obtained in the first step is subjected to extractive distillation to separate methanol and circulated as a reaction raw material in the first step.
<Third step>
Dimethyl carbonate is distilled off from the high-boiling fraction recovered in the second step.
<4th process>
Ethylene carbonate is separated from the high-boiling fraction recovered in the third step and circulated as a reaction raw material in the first step and circulated as an extraction solvent in the second step. The ratio of ethylene carbonate separated in the first step and the second step separated in the fourth step is 30 to 80% by weight of the first step and 20 to 70% by weight of the second step (total of 100% by weight in both steps). The method for producing dimethyl carbonate according to claim 1.

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