TWI449690B - Method for producing ethylene carbonate and ethylene glycol - Google Patents

Description

Method for preparing ethyl carbonate and ethylene glycol

The present invention relates to a process for the preparation of ethyl carbonate and/or ethylene glycol.

Ethyl carbonate is used as, for example, a solvent of various high molecular weight compounds, a chemical solvent for various chemical reactions, a solvent for an electrolyte solution (electrolyte) for a lithium ion secondary battery, an extractant, A blowing agent, and a lubricant stabilizer. Usually, ethyl carbonate is synthesized by reacting ethylene oxide with carbon dioxide at a high temperature and a high pressure. Therefore, the ethyl carbonate contains diol (including, for example, ethylene glycol and diethylene glycol derived from materials for synthesis). For example, a small amount of water is also contained in the ethyl carbonate with the aforementioned impurities. This water reacts with ethyl carbonate to further produce ethylene glycol.

Preferably, the ethyl carbonate (which acts as a solvent for a wide variety of types) does not contain any very small amounts of impurities. A wide variety of methods, including, for example, distillation and crystallization, have been proposed for the purification of ethyl carbonate.

Distillation is the most commonly used purification method in the industry. However, ethyl carbonate has a high boiling point of 246 ° C (atmospheric pressure). Therefore, when the ethyl carbonate is purified by distillation, even if distillation is carried out at a low pressure, any thermal decomposition or damage is caused, and the ethyl carbonate exhibits a high molecular weight compound by reacting with the diol and water. According to the research conducted by the inventors, the following facts were found. That is, the bond of the high molecular weight ethylene glycol compound is partially cut off to return to the diol state. Therefore, even if distillation is carried out, the diol is thus left in the ethyl carbonate at an amount of about 100 ppm. Further, the distillation method requires energy corresponding to evaporation of latent heat of vaporization or related substances, and in addition, the reflux ratio must be increased. Therefore, the energy consumed is extremely large compared to the crystallization method, which is sufficient to be cooled by removing the perceptible heat.

The crystallization method is a purification method which utilizes the fact that the impurity component (which is still not crystallized at the temperature at which some of the target components are crystallized) is not mixed into the crystal. The crystallization method can be purified by an operation including only crystallization by cooling and dissolution by heating. Therefore, decomposition is not easily caused by side reactions, and the energy consumed is small. Further, Japanese Patent Application Publication No. 2007-284427 discloses that when the crystallization method described in this patent document is applied, ethyl carbonate having a high purity of not less than 99.999% can be obtained.

However, when ethyl carbonate is purified by crystallization, some traces of the colored component are present in the purified ethyl carbonate. This colored component causes some problems, especially in the case of application to an electrolyte for a lithium ion secondary battery requiring high purity.

According to the research conducted by the inventors, the following facts are gradually revealed. That is, the aforementioned colored component is not removed in the method of, for example, British Patent No. 2098985 and Japanese Patent Application Publication No. 2004-262767, in which a part of a catalyst-containing reaction solution is obtained to recover a catalyst, in which Water is added so that the solution is recycled back to the process after recovery of the catalyst. The colored component remains in the catalyst solution to be recycled to the process, and the colored component is concentrated upon performing continuous operation.

On the other hand, a method of producing ethylene glycol in which ethylene oxide and carbon dioxide are reacted at a high temperature and a high pressure to obtain a reaction solution for producing ethyl carbonate, and water is further added thereto to initiate a hydrolysis reaction, thereby Ethylene glycol is produced (Japanese Patent Publication No. 55-47617 and Japanese Patent Application Laid-Open Nos. 59-13741, 2000-128814, and 2004-196722). The foregoing method causes a problem of clogging or clogging of an output control valve in the hydrolysis reactor (reaction tank) when continuous operation is performed and cycled and a catalyst is used.

General theory of invention

The object of the present invention is to provide a process for producing ethyl carbonate, wherein the colored component contained in the aforementioned ethyl carbonate is removed, and a method for producing ethylene glycol is provided, so that it can be operated stably for a long period of time. At the same time, it prevents the blockage or blockage in the aforementioned glycol process.

The present inventors have devoted themselves to research to achieve the aforementioned object, and as a result, have found the following facts. That is, an ethylene carbonate having been removed from the colored component can be obtained by a method of producing ethyl carbonate (including sometimes referred to as "EC process") comprising the following steps: by making carbon dioxide and ethylene oxide Reacting in the presence of a catalyst to obtain a reaction solution containing ethyl acetate and purifying the ethyl carbonate obtained by crystallization, the method of removing the colored component comprises extracting a part of the ethyl carbonate for the production of ethyl carbonate a reaction solution (sometimes referred to herein as "carbonation reaction solution (reaction solution for producing carbonate)"), and 20 times by weight of water not less than the catalyst dissolved in the extraction solution is added to the extracted solution. The undissolved material is deposited to remove the deposited undissolved material from the extracted solution, and the solution is then recycled to the process. Further, the inventors have found that according to the method of producing ethylene glycol by further adding water to a carbonation reaction solution (hereinafter sometimes referred to as "hydrolysis step"), in the hydrolysis step, it is not in the reactor ( The output control valve of the reaction tank causes any blockage or blockage, even if the operation is continued for 1 year, the method involves extracting a part of the carbonation reaction solution, which is not less than 20 times that of the catalyst dissolved in the extracted solution. A weight of water is added to the extracted solution to deposit the undissolved material, the deposited undissolved material is removed from the extracted solution, and the resulting solution is then recycled to the process. The present invention has thus been completed.

That is, the present invention has the following features.

(1) A method for producing ethyl carbonate, which comprises reacting carbon dioxide and ethylene oxide in the presence of a catalyst to obtain a reaction solution containing ethyl carbonate and purifying carbonic acid obtained by purification by crystallization Ethyl ester, the method comprising extracting a solution containing a catalyst from the reaction solution, adding 20 times by weight of water not less than a catalyst dissolved in the extraction solution to the extracted solution to deposit undissolved matter, The extracted solution removes the deposited undissolved material and then circulates the resulting solution to the reaction solution.

(2) The method according to (1), wherein the catalyst-containing solution is a part of an output solution obtained from a reactor for reacting carbon dioxide with ethylene oxide to produce ethyl carbonate.

(3) A method for producing ethylene glycol, which comprises reacting carbon dioxide, ethylene oxide and water in the presence of a catalyst to obtain a reaction solution containing ethyl acetate and ethylene glycol, and further Water is added to the obtained reaction solution to convert ethyl carbonate to ethylene glycol. The method comprises extracting a solution containing a catalyst from the reaction solution, which is not less than 20 times the weight of the catalyst dissolved in the extracted solution. Water is added to the extracted solution to deposit undissolved material, the deposited undissolved material is removed from the extracted solution, and the resulting solution is then recycled to the reaction solution.

(4) The method according to (3), wherein the catalyst-containing solution is a part of an output solution obtained by a reactor for reacting carbon dioxide, ethylene oxide and water to produce ethyl carbonate and ethylene glycol. And a portion of the output solution obtained from a reactor for converting ethyl formate to ethylene glycol by adding water to the resulting reaction solution.

(5) The method according to any one of (1) to (4), wherein the undissolved substance is removed by static separation, filtration separation, or adsorption removal using an adsorbed substance.

(6) The method according to any one of (1) to (5) wherein the catalyst is iodinated or brominated to a quaternary phosphonium.

(7) An ethyl carbonate which has a Hazen value of not more than 10 and a purity of not less than 99.999%.

(8) A nonaqueous electrolyte solution containing the ethyl carbonate as defined in the item (7).

According to the present invention, there is provided a process for the manufacture of ethyl carbonate, wherein the ethyl carbonate is of high purity, wherein the colored component is removed. Further, there is provided a method for producing ethylene glycol, wherein the operation is carried out stably for a long period of time without causing any clogging or any blockage even if it is continuously operated for a long period of time.

Description of the preferred system (1) About colored components

The colored component contained in the ethyl carbonate is removed in the method for producing ethylene glycol according to the present invention, which is a substance which emits fluorescence when irradiated with ultraviolet light. A method for producing ethyl carbonate according to the present invention by fluorescence analysis (including production of ethyl carbonate by reaction of carbon dioxide and ethylene oxide in the presence of a catalyst, and purification of carbonic acid by crystallization) When the ethyl ester step is traced to the source of the material, the material is already present in the output gas stream obtained from the oxidation reactor used to make the ethylene oxide feedstock, and then the material is passed through the ethylene oxide absorber. And an ethylene oxide stripper, and this material is also contained in ethylene oxide as a raw material used in the EC process of the present invention. In the EC process, the colored component is recycled or recycled to the process along with the catalyst, and the colored component is concentrated.

When attempting to recover the ethyl carbonate derived according to the crystallization method in high purity, the concentrated colored component is mixed as a product into the ethyl carbonate and causes a reddish color. As a result of the structural analysis, the colored component is composed of a component composed of polyethylene glycol, polyethylene, and an aromatic compound. The colored component is dissolved in a polar solvent such as methanol. However, the solubility in water is low. Therefore, when a certain amount of water is added, the substance can be deposited (precipitated) and removed.

(2) Method for preparing ethyl carbonate

The method for producing ethyl carbonate of the present invention is a method comprising the steps of: reacting carbon dioxide and ethylene oxide in the presence of a catalyst to obtain a reaction solution containing ethyl carbonate (sometimes referred to as "supply" The reaction for producing carbonates") and the purification of ethyl acetate by crystallization.

The catalyst which can be used in the above-mentioned reaction for producing ethyl acetate is suitably selected from known catalysts, including, for example, bromide or iodide of an alkali metal (for example, Japanese Patent Publication No. 38-23175) , an alkaline earth metal halide (described in, for example, U.S. Patent No. 2,667,497), an alkylamine, a quaternary ammonium salt (described in, for example, U.S. Patent No. 2,773,070), organotin, antimony Or a hydrazine compound (described in, for example, Japanese Patent Application Laid-Open No. Hei 57-183784), and a halogenated organic sulfonium salt (described in, for example, Japanese Patent Application Laid-Open No. 58-126884). In particular, it is preferred to use a bromide or iodide of an alkali metal or a phosphonium salt. Preferred examples include, for example, potassium iodide, potassium bromide, cesium iodide or quaternary phosphonium bromide (for example, triphenylmethyl sulfonium iodide, triphenylpropyl sulfonium iodide, triphenyl iodide) Benzyl hydrazine, tributylmethyl hydrazine iodide and their bromides. The alkali metal carbonate-forming compound can also be used in combination with a cerium salt. The alkali metal carbonate inhibits addition to ethylene glycol and ethyl carbonate in the carbonation reaction. The production of any by-products is preferable. The potassium salt having a high solubility is preferably the same as the alkali metal. When a combined catalyst is used, a preferred example can be used as described in Japanese Patent Application Laid-Open No. 2000-128814.

Commercially available ethylene oxide having high purity can also be used as the ethylene oxide raw material for the carbonation reaction of the present invention. However, as ^{Ullmanns Encyclopedia of Industrial Chemistry, 5 th} Ed., Vol. A10, p.117 said person, after purification may be used, for example, by the following description of the synthesized reaction product obtained, wherein The reaction is carried out by passing a gas mainly containing ethylene (raw material), oxygen and methane (diluted gas) through a multi-tubular reactor equipped with a silver catalyst. Typically, the selectivity for the conversion of ethylene to ethylene oxide is about 80%. According to the complete oxidation reaction, about 20% of the residue is converted to carbon dioxide and water. The oxidation reaction gas (which flows out of the reactor) is composed of, for example, ethylene oxide, unreacted ethylene, carbonic acid gas, oxygen, and a diluent gas. The obtained ethylene oxide is absorbed by a liquid phase in an absorption tower using water as an absorption liquid. The ethylene oxide absorbed by the absorption liquid is distilled or stripped in an ethylene oxide stripper, and ethylene oxide is recovered from the top of the column as an aqueous solution having a high concentration of ethylene oxide. Further, dehydration treatment and purification treatment are carried out in a distillation column. The aqueous solution of the high concentration of ethylene oxide obtained from the top of the column can also be used directly as a raw material.

The carbonation reaction can be carried out by using any special equipment. For example, a bubble column having a liquid circulation conduit equipped with a heat exchanger for removing heat and a pump for circulation at an intermediate position is controlled by circulating a reaction solution contained in the column through a liquid circulation conduit temperature reflex. This reaction can be carried out continuously by continuously supplying ethylene oxide and carbon dioxide raw materials and catalyst from the bottom of the column. Also preferably, a reactor equipped with a spray type nozzle disclosed in Japanese Patent Application Laid-Open No. Hei No. 11-269110 is used. The reaction temperature is usually from 70 to 200 °C. However, the reaction temperature is preferably from 100 ° C to 170 ° C.

The reaction pressure is usually from 0.6 to 5.0 MPa. However, the reaction pressure is preferably from 1.0 to 3.0 MPa. Water can be added to the carbonation reaction of the present invention. In the presence of water, ethylene oxide is converted not only to ethyl carbonate but also to ethylene glycol. Therefore, even if the supply amount of carbon dioxide does not exceed the molar amount of ethylene oxide, the reaction is easy. The molar ratio of carbon dioxide to ethylene oxide is usually not more than 5, and preferably 0.5 to 3.0.

The supply molar ratio of water to ethylene oxide is usually not more than 10, and preferably from 0.5 to 5.0. This amount is not sufficient to fully react with the ethylene oxide in the bubble column. Therefore, it is also preferred to arrange the tubular reactor after the bubble column to further react ethylene oxide in the solution or liquid. In this procedure, the amount of the catalyst added is expressed as 1/1000 to 1/20, and preferably 1/200 to 1/50, with respect to the molar ratio of ethylene oxide. A portion of the reaction solution obtained in the carbonation reaction may be supplied to the purification step of the purified ethyl carbonate as described below, and the remainder may be preferably recycled to the carbonation reactor, which may be carried out by After the operation for recovering the catalyst, the operation of removing the colored component described below is performed. Alternatively, the operations for recovering the catalyst and the operations for removing the colored components may be performed in different operations. The operation for recovering the catalyst (which is used to prevent decomposition or damage of the catalyst) is carried out, for example, by the methods described in, for example, Japanese Patent Application Laid-Open Nos. 2004-262767, 2004-284976, and 2004-292384.

In general, a method of separating ethyl carbonate from a carbonation reaction solution by crystallization may be employed, in which crude ethyl carbonate crystals are obtained by cooling a carbonation reaction solution. As for the cooling method, the cooling can be carried out according to a known method. Specifically, for example, a method described in Japanese Patent Laid-Open Publication No. 7-89905 in which crystals are deposited on a cold vertical partition wall, followed by warming so that a part of the crystal melts, which flows downward and separates, As a result, crystals with improved purity are recovered. On the other hand, the convection contact method is also known as a continuous crystallization method (for example, Japanese Patent Application Laid-Open No. 2007-284427, British Patent No. 1086028, and "Separation Technology" (The Society of Separation Process Engineers, Japan), Vol. 35, No. 6, pp. 45-49 (2005)). The convection contact method is a method for increasing the purity of ethyl carbonate by the contact between the crystal of the ethyl carbonate and the liquid.

In the EC process of the present invention, a catalyst-containing solution is extracted from the reaction solution, and then 20 times by weight of water not less than the catalyst dissolved in the extraction solution is added to the extracted solution to deposit undissolved. substance. The colored component is removed by removing the deposited undissolved material (this operation is sometimes referred to herein as "colored component removal operation (operation to remove colored components)"). The solution containing the catalyst can be extracted anywhere in the solution containing the catalyst to be recycled. However, for example, it is preferred to extract a portion of the output liquid or liquid obtained at the outlet of the carbonation reactor. Suitably, the amount of extraction is the amount by which the colored component will not be concentrated in the process, since the solution or liquid is recycled to the EC process after removal of the colored component. The extraction amount is from 1/500 to 1/5, and preferably from 1/100 to 1/10, of the output solution obtained at the outlet of the carbonation reactor.

As for the amount of water added to the extracted solution containing the catalyst, the amount of water required to deposit the colored component must be added. The amount of water added is not less than 20 times by weight, preferably not less than 50 times by weight, and most preferably not less than 60 times by weight, based on the weight of the catalyst contained. As for the maximum amount, if a large amount of water is included in the method, a very large amount of energy is required to remove the water. Therefore, suitably, the maximum amount is not more than 100 times by weight and preferably not more than 200 times by weight with respect to the weight of the contained catalyst.

The above-mentioned extracted catalyst-containing solution can also continuously carry out the operation of recovering the catalyst and the operation of removing the colored component. First, the catalyst is recovered from the extracted catalyst-containing solution in the manner described above. The recovered catalyst may be used in this state, or the recovered catalyst may be dissolved, for example, in ethylene glycol to obtain a solution which can be used as a solution containing a catalyst. Water may also be added thereto to remove colored components. The amount of water added by this procedure is also equivalent to the foregoing.

Regarding the method of adding water, when the catalyst concentration is thin or low, no special equipment is required. For example, a water pipe can be connected to the catalyst-containing solution for mixing in the pipeline. On the other hand, when the catalyst concentration is, for example, a high concentration of 40% by weight, the catalyst is temporarily deposited when water is added. Therefore, preferably, this operation is carried out in a dissolver or tank equipped with a stirrer. The colored component is deposited after the addition of water. Thus, the deposited colored component is separated and removed by any suitable method. In particular, the separation and removal methods can be any method including, for example, static separation, filtration, and adsorption removal. In the case of static separation, the solution or liquid must be left for a period of time sufficient to precipitate the colored component. After the solution or liquid is allowed to stand, it is preferably allowed to stand for not less than 0.5 hours and more preferably not less than 1 hour, and the supernatant liquid is recovered as a catalyst solution. Regarding the apparatus used for performing the static separation, for example, the apparatus used may be a precipitator or a tank, wherein a general precipitator is provided with an input line and an output line which are located at opposite positions to reduce the flow velocity inside.

In the case of filtration separation, the separation is carried out by using a general filtration device or a percolator. However, after the addition of water, the colored components gradually aggregate and aggregate, and are easily filtered. Therefore, preferably, the filtration efficiency of the color component is determined, and the solution or liquid retention is preferably not less than 5 minutes and more preferably not less than 30 minutes before filtration. Regarding the apparatus for filtration, a commercially available general filtration apparatus or a percolator is suitably used. In the adsorption separation, adsorbents may also be used including, for example, general activated carbon and zeolite. However, it is preferred to use cotton-like materials including, for example, glass wool, polypropylene velvet, cotton, and metal velvet, which are capable of physically adhering or adsorbing colored components without difficulty due to their properties. Specifically, regarding the apparatus to be used, for example, a solution or a liquid containing a coal-contacting coal and adding water as described above is passed through a glass wool-filled adsorption container or tank, and thereby the colored group can be satisfactorily removed. Share.

There is no particular limitation on the period during which the solution or liquid is passed. When the density of the absorbent is thin or low, the solution must be allowed to flow slowly. However, when the absorbent is introduced in a dense manner, the adsorption treatment can be carried out in a short time. It is also possible to agglomerate colored components for a period of time before being supplied to the adsorption vessel. However, these two effects are carried out by allowing the adsorption time to be about 15 minutes to 3 hours to simultaneously perform adsorption and agglomeration in the adsorption container. The solution containing the catalyst obtained after removal of the colored component is recycled to the carbonation reaction of the EC process. The position at which the solution containing the catalyst is returned can be any position as long as the catalyst circulates at the position. This location includes, for example, the inlet of the carbonation reactor, the outlet of the carbonation reactor, and the catalyst separation step.

The ethyl carbonate which is produced by the EC process of the present invention is colorless and has high purity. Therefore, ethyl carbonate is preferably used as a raw material, for example, a raw material of a non-aqueous electrolyte solution (electrolyte). The so-called "no color" specifically means that the Hazen value does not exceed 10. A carbonic acid ethyl ester having a Hazen value of not more than 10 and a purity of not less than 99.999% and a nonaqueous electrolyte solution containing the ethyl carbonate are also included in the present invention. The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent for dissolving it in the same manner as any of the general non-aqueous electrolyte solutions. The non-aqueous electrolyte solution of the present invention contains these components as a main component, which is produced according to a generally used method.

(3) Method of preparing ethylene glycol

Another aspect of the invention relates to a process for the preparation of ethylene glycol based on a process comprising the following steps (sometimes referred to herein as "the process of EG"): by allowing carbon dioxide, ethylene oxide and water to be present in the presence of a catalyst Reacting to obtain a reaction solution containing ethyl acetate and ethylene glycol, and converting ethylene carbonate to ethylene glycol by further adding water to the obtained reaction solution (hydrolysis step), the method comprising self-reaction The solution is extracted with a solution containing a catalyst, and 20 times by weight of water not less than the catalyst dissolved in the extracted solution is added to the extracted solution to deposit undissolved substances, and the deposited solution is removed by deposition. The undissolved material is then recycled to the process. In another aspect, the colored component of ethyl carbonate (which will be removed in the method for making ethyl carbonate) described above causes clogging or clogging in the hydrolysis step of the process for making ethyl carbonate. . Therefore, when the colored component is removed according to the same or equivalent method, ethylene glycol can be stably produced for 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 obtain a reaction solution containing ethyl acetate and ethylene glycol is the same as the above-described EC production method or equal. The carbonation reaction solution is supplied to the hydrolysis step. However, a portion of the ethyl carbonate can be isolated and purified according to appropriate methods. In this procedure, the method of purifying ethyl carbonate is not limited to the aforementioned crystallization method. It is also possible to use, for example, a known distillation method. Of course, when purified by the aforementioned crystallization method, ethyl carbonate which is colorless and has high purity can be obtained.

From the viewpoint of the reaction rate, advantageously, in the hydrolysis step, the reaction is carried out at a high temperature. However, if the temperature is too high, there is a concern that the quality of the ethylene glycol is impaired. Therefore, it is usually preferred to carry out the reaction at 100 to 180 °C. The reaction pressure must be in the range of up to the boiling point of the solution or liquid. However, it is usually preferred to carry out the reaction at a pressure of from atmospheric pressure to 2.1 MPa. Further, preferably, when the hydrolysis reaction is carried out, the hydrolysis reaction is facilitated by increasing the reaction temperature and/or lowering the reaction pressure. In particular, a method described in, for example, Japanese Patent Application Laid-Open No. 59-13741 and No. 2000-128814, for example, a portion related to a raw material and an added amount of water can be used.

Ethylene glycol can be obtained by a method of producing ethylene glycol by a hydrolysis reaction according to a known method. Typically, the water is separated by distillation, preferably by distillation under reduced pressure to give crude ethylene glycol from, for example, ethylene glycol, diethylene glycol, other high boiling components, and carbonation reaction. The composition of the media. Thereafter, to separate the catalyst from the ethylene glycol, the crude ethylene glycol is supplied to the evaporation device. A larger portion of the ethylene glycol and a portion of the high boiling component are evaporated and recovered to obtain a residual liquid (which is composed, for example, of a catalyst, residual ethylene glycol, and a high boiling component). The residual liquid is supplied to the aforementioned carbonation reaction in the form of a "catalyst solution". The catalyst recovery step is also carried out at a low pressure to facilitate evaporation or gasification of the ethylene glycol and high boiling components. A device equipped with a reboiler serves as an evaporation device in which the energy required for evaporation is supplemented and the amount of evaporation is controlled.

In the EG process of the present invention, the catalyst-containing solution is also extracted from the reaction solution. 20 times by weight of water not less than the catalyst dissolved in the extracted solution was added to the extracted solution to deposit and remove undissolved matter. The solution is then recycled to the process again. In this procedure, the solution containing the catalyst may be any solution or liquid as long as it contains the catalyst used in the EG process. However, for example, it is preferred to use an output solution obtained at the outlet of the carbonation reactor or at the reaction solution of the hydrolysis step.

In the EG process, the catalyst recovered in the catalyst recovery step may also be subjected to a catalyst recovery operation to prevent any further decomposition of the catalyst, and the solution (by dissolving the recovered catalyst, for example, Alcohol, whichever is obtained, can be used as a solution containing a catalyst. In this procedure, the location where the circulating solution or liquid is returned also includes, for example, a carbonation reactor and a hydrolysis reactor.

Example 1: Manufacture of ethyl carbonate (1) Carbonation reaction

5 parts by weight of tributylmethylphosphonium iodide, 0.8 parts by weight of potassium carbonate, and 78 parts by weight of a raw material ethylene oxide aqueous solution (60% by weight) were supplied to the first reactor (100) °C, pressurization with carbon dioxide to 2.0 MPa), and left for 1 hour to obtain a carbonation reaction solution containing ethyl carbonate and ethylene glycol (EG). The resulting reaction solution was extracted at 3 parts by weight/hour, and water was added thereto in an amount of 60 times by weight based on the amount of the catalyst contained. This solution was passed through an adsorber of an existing polypropylene velvet (manufactured by DCM Japan Co., Ltd.) at SV=1. The catalyst solution passed has a pale yellow color. This solution was used and recycled to the carbonation reactor.

(2) Purification of ethyl carbonate

This operation lasted for one month, after which the ethyl carbonate was crystallized and purified from the carbonation reaction solution according to the method described in WO 2007/108213. Specifically, an upright type melting purification apparatus described in Japanese Patent Laid-Open Publication No. 6-91103 is used as a crystallization apparatus. This purification device is equipped with a stirrer. The agitator used was equipped with a stirring shaft with a horizontal stirring rod as a stirring blade. A slit-like observation hole (observation hole or window for confirming accumulation or sedimentation of crystals) is provided on the side of the crystallization apparatus used.

A part of the reaction solution obtained in the carbonation reaction was cooled to 17 ° C by a crystallization apparatus equipped with a cooling jacket (described in Japanese Patent Application Laid-Open No. 6-91103). A slurry containing ethylene glycol crystals was produced which was supplied from a crystal supply tube of the aforementioned crystallization apparatus. The crystals settle in the crystallization apparatus. Excess mother liquor is recovered from the upper portion of the crystallizer as an overflow liquid and recycled to the hydrolysis reactor.

The crystals settle and the crystals gradually accumulate at the bottom of the column. The crystal is heated by a heater to melt the crystal to form a melt. The melt initially moves upward while being in convection contact with the settled crystals (reflux liquid), and the melt is extracted from the upper extraction tube. This solution is returned to the hydrolysis reaction via a crystallization apparatus. At this point in time, ethylene glycol was not extracted from the product extraction tube to form a cumulative crystal layer on the melt. The cumulative crystal layer thickness was observed from the observation holes, and the amount extracted from the product extraction tube was adjusted so that the accumulated crystal layer thickness was 95% of the height of the crystallization apparatus.

This operation was continued for 3 days, and the quality of the ethyl carbonate product was evaluated using gas chromatography and a Karl Fischer hygrometer. As a result, the product had a glycol concentration of 1 ppm and a moisture content or water content of 2 ppm. In other words, the purity of the ethyl carbonate product is not less than 99.999%. As for the chromaticity, the Hazen value (APHA) does not exceed 10.

Comparative example 1

Ethyl carbonate was produced in the same manner as in Example 1, but the reaction solution obtained from the carbonation reaction was not extracted and the step of adding water to remove the deposited substance was not performed. The ethylene glycol concentration and moisture content of the ethyl carbonate product obtained after one year of operation were not changed as compared with Example 1. However, the chromaticity is slightly red, and the depth of the color represented by the Hazen value (APHA) is about 25.

Examples 2 to 6

The step of removing the deposited undissolved matter was carried out in the same manner as in Example 1, except that in the step of extracting the reaction solution obtained from the carbonation reaction and adding water to remove the deposited substance, the amount of added water and the shift were changed. A method other than undissolved matter. The results obtained are shown in Table 1. As apparent from Table 1, when the amount of water added to the solution containing the catalyst is 20 times the amount of the catalyst, after the undissolved substance or component is removed from the solution containing the catalyst, no effect is observed in the resulting solution. colour.

Comparative example 2

The step of removing the deposited undissolved substance or component is carried out in the same manner as in Example 1, except that in the step of extracting the reaction solution obtained from the carbonation reaction and adding water to remove the deposited substance, the amount of water added is The method of removing the undissolved matter by 10 times the amount of the catalyst was changed to the filtration method. The results obtained are shown in Table 1. As apparent from Table 1, when the amount of water added to the solution containing the catalyst is 10 times the amount of the catalyst, after the undissolved substance is removed from the solution containing the catalyst, the resulting solution is the same as that before the filtration, and the color is the same. The component was not removed.

Example 7: Preparation of ethylene glycol

The procedure was carried out in the same manner as in Example 1 until the carbonation reaction. The carbonation reaction solution was transferred to the second reactor, wherein the residence time was 2 hours, the pressure was 0.5 MPa, the temperature was 150 ° C, and the ethyl carbonate containing ethyl ester was hydrolyzed to obtain 66.5 parts by weight/time of catalyst-containing catalyst. Aqueous ethylene glycol solution. In this procedure, a portion of the carbonation reaction solution was extracted from the first reactor at 3 parts by weight/hour. Water was added in an amount of 60 times the amount of the catalyst contained in the solution. This solution was passed through a adsorption vessel equipped with polypropylene velvet (manufactured by DCM Japan Co., Ltd.) at SV=1. The passed solution is used and recycled to the carbonation reaction step.

The reaction solution obtained by the hydrolysis reaction is subjected to distillation, for example, by distillation at a low pressure of 80 Torr at 140 ° C to obtain a dehydrated solution from the bottom of the column. In addition, a larger portion of the ethylene glycol evaporates from the lower pressure evaporator operating at 140 ° C and 60 Torr. The catalyst-concentrated catalyst solution was recovered from the bottom of the evaporator at 13 parts by weight per hour. The recovered catalyst solution is used and recycled to the first reactor as a catalyst. At the beginning of the operation, the catalyst solution had a vinegar color, and no significant change in color was observed after one year of continuous operation. The control valve at the outlet of the hydrolysis reactor is free of any blockage or any blockage and this operation is successful and stable.

Comparative example 3

The operation was carried out for one year in the same manner as in Example 7, except that the step of extracting the carbonation solution with added water and recycling the solution after removing the deposited undissolved component was not performed. At the beginning of the operation, the catalyst solution was vinegar colored, and after one year of continuous operation, the color of the catalyst solution was changed to wine red. The control valve at the outlet of the hydrolysis reactor is clogged or blocked and it is difficult to perform any stable operation.

Example 8

The procedure was carried out in the same manner as in Example 7 until the hydrolysis reaction. The output solution from the hydrolysis reactor was extracted, water was added thereto, and the amount added was 60 times by weight of the amount of the catalyst contained in the solution, and then the deposited undissolved component was filtered with 5C filter paper. As a result, turbidity was removed and the uncolored catalyst solution was successfully recovered.

Example 9

The procedure was carried out in the same manner as in Example 7 until a larger portion of the ethylene glycol was evaporated from the hydrolysis reaction solution and the catalyst solution (in which the catalyst was concentrated) was recovered from the bottom of the evaporator at 13 parts by weight/hour. Water was added in an amount of 180 times by weight based on the amount of the catalyst contained in the obtained catalyst solution. As a result, the solution originally turned into burgundy became cloudy. The undissolved components deposited were filtered through 5C filter paper. As a result, turbidity was removed and the uncolored catalyst solution was successfully recovered. The precipitate adhered to the filter paper was washed with water, after which the precipitate was washed with methanol. As a result, methanol has a deep burgundy color, and the colored components contained in the catalyst solution are separated.

Claims (6)

A method for producing ethyl carbonate, which comprises reacting carbon dioxide and ethylene oxide in the presence of a catalyst to obtain a reaction solution containing ethyl carbonate and purifying ethyl carbonate by crystallization, the method comprising The reaction solution extracts a solution containing a catalyst, and 20 times by weight of water not less than a catalyst dissolved in the extracted solution is added to the extracted solution to deposit an undissolved substance, and the extracted solution is removed. The undissolved material is deposited and the resulting solution is then recycled to the reaction solution. The method of claim 1, wherein the catalyst-containing solution is part of an output solution obtained from a reactor for reacting carbon dioxide with ethylene oxide to produce ethyl carbonate. A method for producing ethylene glycol comprising reacting carbon dioxide, ethylene oxide and water in the presence of a catalyst to obtain a reaction solution containing ethyl carbonate and ethylene glycol, and further adding water to Converting ethyl carbonate to ethylene glycol in the obtained reaction solution, the method comprising extracting a solution containing a catalyst from the reaction solution, and adding not less than 20 times by weight of water dissolved in the catalyst in the extraction solution To the extracted solution to deposit undissolved material, the deposited undissolved material is removed from the extracted solution, and the resulting solution is then recycled to the reaction solution. The method of claim 3, wherein the catalyst-containing solution is part of an output solution obtained from a reactor for reacting carbon dioxide, ethylene oxide, and water to produce ethyl carbonate and ethylene glycol. And a portion of the output solution obtained from a reactor for converting ethyl formate to ethylene glycol by adding water to the resulting reaction solution. The method of any one of claims 1 to 4, wherein the undissolved material is removed by static separation, filtration separation, or adsorption removal using an adsorbent material. The method of any one of claims 1 to 4, wherein the catalyst is iodinated or brominated to a quaternary phosphonium.