JP5660048B2 - Process for producing ethylene carbonate and ethylene glycol - Google Patents

Description

  The present invention relates to a method for producing ethylene carbonate and / or ethylene glycol.

  Ethylene carbonate is used as a solvent for various polymer compounds, a reaction solvent for various chemical reactions, an electrolyte solvent for lithium ion secondary batteries, an extractant, a foaming agent, and a lubricant stabilizer. Ethylene carbonate is usually synthesized by reacting ethylene oxide and carbon dioxide at high temperature and high pressure. For this reason, ethylene carbonate contains diols such as ethylene glycol and diethylene glycol derived from these synthetic raw materials. In addition, ethylene carbonate contains a small amount of moisture together with the above impurities, but this moisture reacts with ethylene carbonate to further produce ethylene glycol.

Ethylene carbonate used as various solvents preferably contains as little impurities as possible, and various methods such as distillation and crystallization have been proposed as methods for purifying ethylene carbonate.
The distillation method is the most widely used purification method industrially. However, because ethylene carbonate has a high boiling point of 246 ° C. (normal pressure), when ethylene carbonate is purified by distillation, thermal degradation occurs even if distillation is performed under reduced pressure, and ethylene carbonate reacts with diol and moisture. And high molecular weight. Further, in the study conducted by the present inventors, some bonds of the high molecular weight ethylene carbonate were broken and returned to diol, so that even after distillation, about 100 ppm of diol remained in ethylene carbonate. I found out that In addition, the distillation method requires energy for the latent heat of vaporization of the substance, and the reflux ratio must be increased. Therefore, the energy consumption is very large compared to the crystallization method that only requires cooling by sensible heat removal.

  The crystallization method is a purification method that utilizes the fact that an impurity component that does not crystallize at that temperature does not enter the crystal when the target component is crystallized. Since the crystallization method can be purified only by crystallization by cooling and dissolution by slight heating, deterioration due to side reactions hardly occurs and energy consumption is low. Patent Document 1 discloses that 99.999% or more of high-purity ethylene carbonate can be obtained by applying the crystallization method described in this document.

However, when ethylene carbonate is purified using a crystallization method, there is a slight coloring component in the purified ethylene carbonate, especially for electrolyte applications such as lithium ion secondary batteries that require high purity. This coloring component was a problem.
Depending on the method (Patent Documents 2 and 3) in which these coloring components are obtained, for example, in order to recover the catalyst, a part of the reaction solution containing the catalyst is obtained, water is added, and the catalyst is recovered and then recycled to the process. It has been found by the present inventors that the catalyst solution is not removed but remains in the catalyst solution circulated in the process and is concentrated as it is continuously operated.

  Further, a method for producing ethylene glycol by adding water to an ethylene carbonate reaction solution obtained by reacting ethylene oxide and carbon dioxide at high temperature and high pressure to cause a hydrolysis reaction is known (Patent Documents 4 to 4). 7). When the above process is continuously operated while circulating the catalyst, there has been a problem that the outlet control valve and the like are blocked in the hydrolysis reaction tank.

JP 2007-284427 A British Patent No. 2098985 JP 2004-262767 A Japanese Patent Publication No.55-47617 JP 59-13741 A JP 2000-128814 A JP 2004-196722 A

  The present invention provides a method for producing ethylene carbonate from which the coloring component contained in the ethylene carbonate is removed, and a method for producing ethylene glycol that can be stably operated for a long time while preventing clogging in the ethylene glycol production process. The issue is to provide

  As a result of intensive studies to solve the above problems, the present inventors obtained a reaction liquid containing ethylene carbonate by reacting carbon dioxide with ethylene oxide in the presence of a catalyst, and the produced ethylene carbonate was crystallized. In an ethylene carbonate production method by a process including a step of purifying by analysis (this may be referred to as “EC production process” in the present specification), an ethylene carbonate reaction solution (in this specification, “ A part of the carbonated reaction solution ”is extracted, and 20 weight times or more of water is added to the catalyst dissolved in the extracted solution to precipitate insoluble components, and the precipitated insoluble components are extracted. After removing from the liquid, it is found that ethylene carbonate from which coloring components have been removed is produced by circulating in the process. . Furthermore, the present inventors further added water to the carbonated reaction solution to produce ethylene glycol (hereinafter sometimes referred to as “hydrolysis step”). Extracting and adding 20 weight times or more of water to the catalyst dissolved in the extraction liquid to precipitate insolubles, removing the precipitated insolubles from the extraction liquid, and circulating to the process, 1 It has been found that even in the continuous operation for a year, the outlet control valve of the reaction tank does not clog in the hydrolysis step, and the present invention has been completed.

That is, the present invention
(1) In the manufacturing method of ethylene carbonate including the step of reacting carbon dioxide and ethylene oxide in the presence of a catalyst to obtain a reaction solution containing ethylene carbonate, and purifying the produced ethylene carbonate by crystallization, from the reaction solution Extracting the liquid containing the catalyst, adding 20 weight times or more of water to the catalyst dissolved in the extracted liquid to precipitate insolubles, removing the precipitated insolubles, and circulating to the reaction liquid A process for producing ethylene carbonate,
(2) The method according to (1) above, wherein the liquid containing the catalyst is a part of a reactor outlet liquid that reacts carbon dioxide and ethylene oxide to produce ethylene carbonate.
(3) A step of reacting carbon dioxide, ethylene oxide, and water in the presence of a catalyst to obtain a reaction liquid containing ethylene carbonate and ethylene glycol, and further adding water to the reaction liquid to convert ethylene carbonate into ethylene glycol. In the method for producing ethylene glycol, the catalyst-containing liquid is extracted from the reaction liquid, and 20 weight times or more of water is added to the catalyst dissolved in the extracted liquid to precipitate insoluble matter. After removing the solvent, circulating in the reaction solution, ethylene glycol production method,
(4) The liquid containing the catalyst reacts with carbon dioxide, ethylene oxide, and water to produce ethylene carbonate and ethylene glycol. A part of the outlet liquid of the reactor and / or water is added to the reaction liquid to add ethylene carbonate. The method according to (3) above, which is a part of the outlet liquid of a reactor that converts ethylene to ethylene glycol,
(5) The method according to any one of (1) to (4) above, wherein the insoluble matter is removed by stationary separation, filtration separation, or adsorption removal with an adsorbing substance,
(6) The method according to any one of (1) to (5) above, wherein the catalyst is a quaternary phosphonium iodide and / or bromide,
(7) ethylene carbonate having a Hazen number color of 10 or less and a purity of 99.999% or more,
(8) A non-aqueous electrolyte containing the ethylene carbonate described in (7) above,
It is.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the highly purified ethylene carbonate from which the coloring component was removed is provided. Moreover, the manufacturing method of the ethylene glycol which can be drive | operated stably, without being obstruct | occluded by long-term continuous operation is provided.

(1) Coloring component The coloring component in ethylene carbonate to be removed by the method for producing ethylene glycol of the present invention is a substance that emits fluorescence when irradiated with ultraviolet rays. In the presence of a catalyst, carbon dioxide and ethylene oxide are reacted to form ethylene carbonate, and the origin of the presence is traced by fluorescence analysis in the ethylene carbonate production process of the present invention including the step of purifying the produced ethylene carbonate by crystallization. And already in the drain of the outlet gas of the oxidation reactor for producing the raw ethylene oxide, and then passed through the ethylene oxide absorption tower and the ethylene oxide stripping tower in the ethylene oxide that is the raw material of the EC production process of the present invention. Also included. Further, in the EC production process, the coloring component is circulated and concentrated in the process together with the catalyst.

This concentrated colored component is mixed with the product ethylene carbonate and becomes reddish when the produced ethylene carbonate is recovered with high purity by a crystallization method.
As a result of structural analysis, this colored component is composed of components composed of polyethylene glycol, polyethylene, and aromatics. In addition, the coloring component is soluble in a polar solvent such as methanol, but has low solubility in water. Therefore, the coloring component is a substance that can be precipitated and removed by adding a certain amount of water.

(2) Ethylene carbonate production method The ethylene carbonate production method of the present invention comprises the production of ethylene carbonate by reacting carbon dioxide and ethylene oxide in the presence of a catalyst (in the present specification, this is referred to as "carbonation reaction"). This is due to a process including a step of purifying the produced ethylene carbonate by crystallization.

Examples of the catalyst used in the ethylene carbonate reaction include alkali metal bromides or iodides (for example, those described in JP-B No. 23175), alkaline earth metal halides (for example, US Pat. No. 2,667). , 497), alkylamines, quaternary ammonium salts (for example, those described in US Pat. No. 2,773,070), organotins or germanium or tellurium compounds (for example, JP The one described in Japanese Patent Laid-Open No. 57-183784) and halogenated organic phosphonium salts (for example, those described in Japanese Patent Laid-Open No. 58-126844) may be appropriately selected and used.
Of these, alkali metal bromides or iodides, or phosphonium salts are preferably used. Preferred examples include potassium iodide, potassium bromide, quaternary phosphonium iodide or quaternary phosphonium bromide, such as triphenylmethylphosphonium iodide, triphenylpropylphosphonium iodide, triphenylbenzylphosphonium iodide, tributylmethylphosphonium iodide. Id or bromide thereof. Moreover, the compound which forms an alkali metal carbonate can also be used together with a phosphonium salt. Alkali metal carbonates are preferred because they suppress the formation of by-products other than ethylene glycol and ethylene carbonate in the carbonation reaction. As the alkali metal, a potassium salt having high solubility is preferable. A preferable example in the case of using a catalyst together is as described in JP-A-2000-128814.

  Ethylene oxide used as a raw material for the carbonation reaction of the present invention may be commercially available high-purity ethylene oxide, for example, described in Ullmanns Encyclopedia of Industrial Chemistry, 5th Ed. As shown in the figure, a gas composed mainly of ethylene and oxygen as raw materials and methane as a diluent gas is passed through a multi-tubular reactor filled with a silver catalyst to perform a reaction, For example, it can be purified and used as described below. Usually, the selectivity of ethylene to ethylene oxide is about 80%, and the remaining 20% is converted to carbon dioxide and water by a complete oxidation reaction. The oxidation reaction gas flowing out of the reactor is composed of generated ethylene oxide and unreacted ethylene, carbon dioxide gas, oxygen, dilution gas, and the like. The produced ethylene oxide is absorbed in the liquid phase by an absorption tower using water as an absorption liquid. The ethylene oxide absorbed in the absorption liquid is diffused in an ethylene oxide stripping tower, recovered as a high-concentration ethylene oxide aqueous solution from the top of the tower, and further subjected to dehydration purification in a distillation tower. In addition, an aqueous solution of high-concentration ethylene oxide obtained from the top of the tower as described above can be directly used as a raw material.

  The carbonation reaction can be carried out using any apparatus. As an example, the reaction temperature is controlled by circulating the reaction liquid in the tower through the liquid circulation conduit using a bubble tower having a liquid circulation conduit equipped with a heat exchanger for heat removal and a circulation pump in the middle. The raw material ethylene oxide, carbon dioxide, and catalyst can be continuously supplied from the bottom of the column to continuously react. It is also preferable to use a reactor equipped with an ejector type nozzle as disclosed in JP-A-11-269110. The reaction temperature is usually 70 to 200 ° C, preferably 100 to 170 ° C.

  The reaction pressure is usually 0.6 to 5.0 MPa, preferably 1.0 to 3.0 MPa. Water may be added to the carbonation reaction of the present invention. In the presence of water, ethylene oxide is converted not only to ethylene carbonate but also to ethylene glycol. The reaction proceeds easily even with the supply amount. Usually, the molar ratio of carbon dioxide to ethylene oxide is 5 or less, preferably 0.5 to 3.0.

  The molar ratio of water to ethylene oxide is usually 10 or less, preferably 0.5 to 5.0. In addition, since it is inefficient to completely react the ethylene oxide in the bubble column, it is also preferable to arrange a tubular reactor after the bubble column to further react the ethylene oxide in the liquid. At this time, the addition amount of the catalyst is 1/1000 to 1/20, preferably 1/200 to 1/50 in molar ratio with respect to ethylene oxide. A part of the reaction solution obtained in the carbonation reaction is sent to a purification step of ethylene carbonate described later, and the rest is preferably subjected to a coloring component removal operation described later after performing a catalyst recovery operation described later. It can also be circulated to the carbonation reactor, and the catalyst recovery operation and the color component removal operation may be performed as separate operations. Examples of the catalyst recovery operation performed to prevent the deterioration of the catalyst include the methods described in JP-A-2004-262767, JP-A-2004-284976, JP-A-2004-292384, and the like.

  As a method for separating ethylene carbonate from the carbonated reaction solution by crystallization, generally, a crude ethylene carbonate crystal may be produced by cooling the carbonated reaction solution. As a cooling method, it can cool by a well-known method. Specifically, for example, as described in JP-A-7-89905, a crystal is deposited on a cold vertical wall, and then heated to melt a part of the crystal and flow down. A method of recovering crystals having a higher purity by separating them can be used. As a continuous crystallization method, a countercurrent contact method is also known (Japanese Patent Laid-Open No. 2007-284427, British Patent No. 1086028, Separation Technology Vol. 35, No. 6, pages 45 to 49 (2005). Etc.). The counter-current contact method is a method for increasing the purity of ethylene carbonate by bringing ethylene carbonate crystals into contact with a liquid.

  In the EC production process of the present invention, a solution containing the catalyst is extracted from the reaction solution, and 20 wt times or more of water is added to the catalyst dissolved in the extract solution to precipitate insoluble matter. Is removed from the extracted liquid to remove the colored component (this may be referred to as “colored component removing operation” in the present specification). The place for extracting the liquid containing the catalyst may be any place as long as it contains the circulating catalyst. For example, it is preferable to extract a part of the outlet liquid of the carbonation reactor. The amount to be withdrawn can be recirculated to the EC production process after removing the colored components, so long as the colored components are not concentrated in this process, but it is 1/500 to 1/5 of the carbonated reactor outlet liquid. The ratio is preferably 1/100 to 1/10.

  The amount of water added to the liquid containing the extracted catalyst needs to be added in an amount necessary for the coloring substance to precipitate, and is 20 times by weight or more, preferably 50 times by weight or more, relative to the contained catalyst. Most preferably, it is 60 weight times or more. In addition, as the maximum amount, when the amount of water contained in the process increases, it takes a lot of energy to finally remove the water, so 1000 weight times or less, preferably 200 weight times the catalyst amount contained. The following are appropriate.

  About the liquid containing the catalyst extracted above, the above-mentioned catalyst recovery operation and colored component removal operation can be performed continuously. First, the catalyst is recovered from the liquid containing the extracted catalyst as described above, and the recovered catalyst is used as it is or dissolved in ethylene glycol as a liquid containing the catalyst. Can also be removed. The amount of water added at this time is the same as above.

In the method of adding water, when the catalyst concentration is low, no special device is necessary. For example, a solution containing the catalyst and a water pipe may be connected and mixed in the pipe. When the catalyst concentration is as high as 40% by weight, for example, the catalyst is temporarily precipitated when water is added.
After adding water, a colored component is precipitated, which is separated and removed by an appropriate method. Specifically, the separation and removal method may be any method such as stationary separation, filtration, and adsorption separation. In the case of stationary separation, it is necessary to maintain the time necessary for the coloring components to precipitate, and the supernatant is recovered as a catalyst solution after preferably standing for 0.5 hour or longer, more preferably 1 hour or longer. As an apparatus for the stationary separation, for example, an apparatus in which an inlet pipe and an outlet pipe are installed at opposite positions in a normal container to reduce the flow velocity therein may be used as a precipitation tank.

In the case of filtration separation, it may be separated using a normal filtration device, but after adding water, the colored components gradually agglomerate, and filtration becomes easier, preferably 5 minutes or more, more preferably 30 minutes. Filtration after holding the above is preferable from the viewpoint of filterability of the coloring component. As a filtration device, a commercially available filtration device may be used.
In addition, adsorption separation may be performed using ordinary adsorbents such as activated carbon and zeolite, but glass wool, polypropylene wool, cotton, metal wool because the colored components easily physically adhere. A cotton-like material such as is preferable. As an apparatus to be used, specifically, for example, by passing a liquid containing a catalyst to which water has been added as described above through an adsorption tank filled with glass wool, it is possible to satisfactorily remove colored substances.

  The passage time is not particularly limited, but when the density of the adsorbent is low, it is necessary to slowly flow the liquid. However, if the adsorbent is densely packed, the adsorption treatment should be performed in a short time. I can do it. Although it may take time for the colored components to aggregate before being supplied to the adsorption tank, the adsorption time of about 15 minutes to 3 hours is required in order to perform both adsorption and aggregation in the adsorption tank at the same time. Two effects are achieved by applying. The liquid containing the catalyst after removing the coloring components is circulated to the carbonation reaction of the EC production process. The position where the liquid containing the catalyst is returned may be anywhere as long as the catalyst is circulated, and examples thereof include an inlet of the carbonation reactor, an outlet of the carbonation reactor, a catalyst separation step, and the like.

  Since ethylene carbonate produced by the EC production process of the present invention is not colored and has high purity, it is preferably used as a raw material for non-aqueous electrolytes and the like. That there is no coloring specifically means that the Hazen number is 10 or less. The present invention also includes ethylene carbonate having a Hazen number of 10 or less and a purity of 99.999% or more, and a nonaqueous electrolytic solution containing the ethylene carbonate. The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, as is the case with conventional non-aqueous electrolyte solutions. Manufactured by.

(3) Ethylene glycol production method Another aspect of the present invention is to react a carbon dioxide, ethylene oxide, and water in the presence of a catalyst to obtain a reaction liquid containing ethylene carbonate and ethylene glycol, and further add water to the reaction liquid. In the method for producing ethylene glycol by a process (in this specification, this may be referred to as “EG production process”), which includes a step (hydrolysis step) of converting ethylene carbonate to ethylene glycol by adding The liquid containing the catalyst is extracted from the liquid, and 20 weight times or more of water is added to the catalyst dissolved in the extracted liquid to precipitate the insoluble matter, and the precipitated insoluble matter is removed from the extracted liquid. A method for producing ethylene glycol, characterized by being circulated. On the other hand, the colored component of ethylene carbonate removed in the ethylene carbonate production method is a cause of clogging in the hydrolysis step of the ethylene glycol production method. In addition, ethylene glycol can be produced stably over a long period of time.

  In the method for producing ethylene glycol of the present invention, the step of reacting carbon dioxide, ethylene oxide, and water in the presence of a catalyst to produce ethylene carbonate and ethylene glycol is the same as the EC production process. The carbonated reaction solution is supplied to the hydrolysis step, from which part of the ethylene carbonate can be separated and purified by an appropriate method. In this case, the purification method of ethylene carbonate is not limited to the above-described crystallization method, and a known distillation method or the like can also be used. Naturally, when purified by the above crystallization method, high-purity ethylene carbonate without coloring can be obtained.

  In the hydrolysis step, it is more advantageous to carry out the reaction at a high temperature in terms of the reaction rate. However, if the temperature is too high, the quality of ethylene glycol may be deteriorated, so that the reaction is usually preferably carried out at 100 to 180 ° C. The reaction pressure is arbitrary as long as it is in the range up to the boiling point of the liquid, but it is usually preferable to carry out at normal pressure to 2.1 MPa. Also, as the hydrolysis proceeds, the reaction temperature is raised or the reaction pressure is lowered. It is also preferable to promote hydrolysis. Specifically, for example, the method described in JP-A-59-13741 and JP-A-2000-128814 can be used, such as the amount of raw material and water added.

  Ethylene glycol produced by hydrolysis can be obtained by a known method. Usually, after separating water by distillation, preferably distillation under reduced pressure to obtain crude ethylene glycol composed of ethylene glycol, diethylene glycol, other high-boiling components and carbonated catalyst, etc., the catalyst and ethylene glycol are separated. In addition, it is supplied to an evaporator, and a large part of ethylene glycol and a part of high-boiling components are evaporated and recovered, and a residual liquid consisting of a catalyst and the remaining ethylene glycol, high-boiling components is obtained. The liquid "is supplied to the carbonation reaction. This catalyst recovery step is also performed under reduced pressure in order to promote evaporation of ethylene glycol and high-boiling components. As an evaporation apparatus, an apparatus equipped with a reboiler is used to replenish energy required for evaporation and control the evaporation amount.

  Also in the EG production process of the present invention, the liquid containing the catalyst in the reaction liquid is extracted, and 20 wt times or more of water is added to the catalyst dissolved in the extracted liquid to precipitate insoluble matter. After the minute is removed from the extract, it is recycled to the process again. Here, the catalyst-containing liquid may be any liquid as long as it contains the catalyst in the EG production process, but preferably, the outlet liquid of the carbonation reactor, the reaction liquid of the hydrolysis step, etc. are preferably used. It is done.

  Also, in this EG production process, the catalyst recovered in the catalyst recovery step is further subjected to a catalyst recovery operation to prevent deterioration of the catalyst, and a solution obtained by dissolving the recovered catalyst in ethylene glycol or the like is used as a liquid containing the catalyst. It can also be used. Also in this case, examples of the position for returning the circulating liquid include a carbonation reactor and a hydrolysis reactor.

Example 1 Production of ethylene carbonate (1) Carbonation reaction Tributylmethylphosphonium iodide 5 parts by weight / hr, potassium carbonate 0.8 in a first reactor at 100 ° C. with a residence time of 1 hour pressurized with carbon dioxide at 2.0 MPa Carbonation reaction liquid containing ethylene carbonate and ethylene glycol (EG) was obtained by supplying 78 parts by weight / Hr of parts by weight / Hr and raw material ethylene oxide aqueous solution (60% by weight). The obtained reaction solution was extracted at 3 parts by weight / Hr, 60 times by weight of water was added to the amount of catalyst contained, and adsorption was performed with SV = 1 and filled with polypropylene wool (manufactured by DCM Japan). The tank was passed through. The color of the catalyst solution that passed through was a pale yellow color. This solution was recycled to the carbonation reactor.
(2) Purification of ethylene carbonate After the above operation had been continued for 1 month, ethylene carbonate was crystallized and purified from the carbonated reaction solution according to the method described in WO2007 / 108213. Specifically, a vertical melt purification apparatus described in JP-A-6-91103 was used as a crystallization apparatus. The refining apparatus was equipped with a stirrer, and a stirrer shaft having a horizontal stir bar was used as a stirring blade attached to the stirrer. In addition, the side surface of the crystallizer was provided with a slit-like viewing window for confirming crystal deposition.

  A part of the reaction solution obtained by the carbonation reaction is cooled to 17 ° C. by a crystallization apparatus with a cooling jacket described in JP-A-6-91103 to form a slurry containing ethylene carbonate crystals, and the above crystals It was supplied from the crystal supply tube of the analyzing apparatus. The crystals settled in the crystallizer, and the excess mother liquor was recovered as an overflow from the top of the crystallizer and circulated to the hydrolysis reactor.

The crystals settled and the crystals deposited on the bottom of the tower were heated with a heater to melt the crystals to form a melt. The molten liquid first rose while coming into contact with the precipitated crystals as a reflux liquid in countercurrent, extracted from the upper extraction tube, and returned to the hydrolysis reaction via the crystallizer.
At this time, ethylene carbonate was not extracted from the product extraction tube, and a crystal deposition layer was formed on the melt. Then, the thickness of the crystal deposition layer was confirmed from the viewing window, and the extraction amount from the product extraction tube was adjusted so that the thickness of the crystal deposition layer was 95% of the crystallizer.

  After the above operation was continued for 3 days, the quality of the product ethylene carbonate was evaluated using a gas chromatograph and a Karl Fischer moisture meter. The ethylene glycol concentration in the product was 1 ppm and the water content was 2 ppm. . That is, the purity of the product ethylene carbonate was 99.999% or more. The hue was 10 or less in terms of Hazen number (APHA).

Comparative Example 1
Ethylene carbonate was produced in the same manner as in Example 1 except that the reaction solution obtained from the carbonated reaction was taken out and the step of removing water by adding water was not performed. After one year of operation, the product ethylene carbonate obtained had the same ethylene glycol concentration and water content as in Example 1, but the hue was slightly reddish, and the color intensity was set to the Hazen number ( APHA) was about 25.

Examples 2-6
In the step of extracting the reaction solution obtained from the above carbonation reaction and removing the precipitate by adding water, the same as in Example 1 except that the amount of water to be added and the method for removing insoluble components were changed. The process of removing the insoluble component which precipitated was performed. The results are shown in Table 1. As is clear from Table 1, when the amount of water added to the liquid containing the catalyst is 20 times the weight of the catalyst, the liquid after removing the insoluble components from the liquid containing the catalyst is colored. I couldn't see it.

Comparative Example 2
In the step of extracting the reaction liquid obtained from the carbonate reaction and removing the precipitate by adding water, the amount of water to be added is 10 times the catalyst amount, and a method for removing insoluble components The step of removing the insoluble components precipitated was carried out in the same manner as in Example 1 except that was changed to filtration. The results are shown in Table 1. As is clear from Table 1, when the amount of water added to the liquid containing the catalyst is 10 times the amount of the catalyst, the liquid after removing the insoluble components from the liquid containing the catalyst is not filtered. The coloring component was not removed.

Example 7 Production Method of Ethylene Glycol The carbonation reaction is carried out in the same manner as in Example 1, and the above carbonated reaction solution is transferred to a second reactor having a residence time of 2 hours, a pressure of 0.5 MPa, and 150 ° C. The ethylene carbonate was hydrolyzed to obtain 66.5 parts by weight of an aqueous solution of ethylene glycol / Hr containing a catalyst. At this time, a part of the carbonated reaction solution was withdrawn from the first reactor at 3 parts by weight / Hr, 60 times by weight of water was added to the amount of catalyst contained in the solution, and SV = 1. An adsorption tank filled with wool (manufactured by DCM Japan Co., Ltd.) was passed through, and the passing solution was circulated for use in the carbonation reaction step.

  The obtained reaction liquid of the hydrolysis reaction was distilled by distillation under reduced pressure at 140 ° C. and 80 torr at the bottom of the column to obtain a dehydrated liquid from the bottom of the column, which was further reduced by a vacuum evaporator operated at 140 ° C. and 60 torr. Most of the ethylene glycol was evaporated, and 13 parts by weight / hr of the catalyst solution in which the catalyst was concentrated was recovered from the bottom of the evaporator. The recovered catalyst liquid was recycled to the first reactor as a catalyst. The catalyst solution that was the color of vinegar at the start of operation did not show a significant change in the color of the catalyst solution after one year of continuous operation. In addition, the control valve at the outlet of the hydrolysis reactor was not blocked and stable operation was possible.

Comparative Example 3
The operation was carried out for 1 year in the same manner as in Example 7 except that the carbonated reaction solution was extracted, water was added, and the precipitated insoluble components were removed, and then the circulation was not performed. The catalyst liquid which was the color of vinegar at the start of operation changed the color of the catalyst liquid to wine red after one year of continuous operation. In addition, the control valve at the outlet of the hydrolysis reactor was clogged, making stable operation difficult.

Example 8
The hydrolysis reaction is performed in the same manner as in Example 7. The above-mentioned hydrolysis reactor outlet liquid is taken out, 60 weight times of water is added to the amount of catalyst in the solution, and the precipitated insoluble component is filtered with 5C filter paper. As a result of filtration, the turbidity was removed and an uncolored catalyst solution could be recovered.
Example 9
The catalyst solution obtained by evaporating most of the ethylene glycol from the hydrolysis reaction solution and recovering 13 parts by weight / hr of the catalyst solution in which the catalyst was concentrated from the bottom of the evaporator was carried out in the same manner as in Example 7. When water was added in an amount of 180 times the amount of the catalyst contained, the wine-red liquid was turbid, and the precipitated insoluble components were filtered with 5C filter paper. A complete catalyst solution could be recovered. Further, the precipitate adhering to the filter paper was washed with water and then washed with methanol. As a result, methanol colored dark wine red, and the colored components contained in the catalyst solution were separated.

Claims (8)

In the presence of a catalyst, a reaction liquid containing ethylene carbonate is obtained by reacting carbon dioxide with ethylene oxide, and the process for purifying the produced ethylene carbonate by crystallization includes the catalyst from the reaction liquid. The liquid is extracted, and 20 weight times or more of water is added to the catalyst dissolved in the extracted liquid to precipitate the insoluble matter. After removing the precipitated insoluble matter , the catalyst after the insoluble matter is removed. A method for producing ethylene carbonate, comprising circulating a solution containing   The process according to claim 1, wherein the liquid containing the catalyst is a part of the outlet liquid of a reactor for reacting carbon dioxide and ethylene oxide to produce ethylene carbonate. Ethylene including a step of reacting carbon dioxide, ethylene oxide, and water in the presence of a catalyst to obtain a reaction liquid containing ethylene carbonate and ethylene glycol, and further adding water to the reaction liquid to convert ethylene carbonate into ethylene glycol. In the glycol production method, a solution containing the catalyst is extracted from the reaction solution, and 20 weight times or more of water is added to the catalyst dissolved in the extracted solution to precipitate the insoluble component, and the precipitated insoluble component is removed. After that, a method for producing ethylene glycol is characterized in that a liquid containing the catalyst from which the insoluble matter has been removed is circulated through the reaction liquid.   The liquid containing the catalyst reacts with carbon dioxide, ethylene oxide, and water to produce ethylene carbonate and ethylene glycol. A part of the outlet liquid of the reactor and / or water is added to the reaction liquid to convert ethylene carbonate into ethylene glycol. 4. A process according to claim 3, characterized in that it is part of the reactor outlet liquid that is converted to. The method according to claim 1 or 2 , wherein the insoluble matter is removed by stationary separation, filtration separation, or adsorption removal with an adsorbing substance. The method according to claim 3 or 4, wherein the insoluble matter is removed by stationary separation, filtration separation, or adsorption removal with an adsorbing substance. 6. The process according to claim 1 , wherein the catalyst is quaternary phosphonium iodide and / or bromide. 7. The method according to claim 3, wherein the catalyst is a quaternary phosphonium iodide and / or bromide.