JP5101710B2 - Purification method of ethylene glycol - Google Patents

Description

  In the production of ethylene oxide by catalytic vapor phase oxidation of ethylene, the recovered ethylene glycol such as a crude glycol aqueous solution produced in the recovery and purification process of ethylene oxide is used as a raw material. The present invention relates to a method for producing monoethylene glycol (MEG).

  Monoethylene glycol for producing polyester fibers adversely affects various properties such as dyeing characteristics, strength, and coloration of the produced polyester fibers even if they contain a small amount of impurities. High purity monoethylene glycol suitable for the production of polyester fibers is called fiber grade monoethylene glycol and must pass the strict UV transmission test standards shown in Table 1 below.

  In general, ethylene glycol is produced by a hydrolysis reaction of ethylene oxide, and an ethylene oxide production plant and an ethylene glycol production plant are generally provided side by side. These processes are described in Non-Patent Document 1, for example.

  An example of an ethylene oxide / ethylene glycol production process is shown in FIG. In the ethylene oxide production process, water is circulated and used as an absorbent to separate and recover the produced ethylene oxide in the reactor effluent gas. In this circulation system, a part of ethylene oxide undergoes a hydrolytic reaction and ethylene glycol accumulates. Therefore, a part of the absorbent is discharged out of the system as a purge flow. Ethylene glycol in the purge stream (crude glycol aqueous solution) is recovered as a by-product ethylene glycol for economic reasons, but the absorption liquid is used as raw materials, chemicals, by-products used in processes such as the oxidation process and ethylene oxide recovery / purification process. Since it contains various impurities such as aldehydes, organic acids, organic chlorines, organic acids, inorganic acid salts derived from reaction products, etc., by-product ethylene glycol recovered by the usual separation and purification method by distillation is It did not pass as fiber grade monoethylene glycol, and was generally an industrial grade product.

  As a method for improving this quality, in recovering ethylene glycol from the above crude glycol aqueous solution, the crude glycol aqueous solution is brought into contact with activated carbon or an ion exchange resin, and the impurities are adsorbed on the activated carbon or ion exchange resin. Further, a method of treating with alkali and activated carbon (Patent Document 1), a method of treating with ion exchange resin and activated carbon (Patent Document 2), etc. have been proposed. Because it contains a lot of reaction products with ethylene oxide, reaction products with by-products and ethylene glycol, etc., it is not suitable for industrial use in order to stop reducing the ability of activated carbon or ion exchange resin. In addition, activated carbon and ion exchange resin are expensive, especially in terms of quality, especially monoethylene glycol. Do not always satisfactory for use in fiber Le, or the processing operation has a problem such as a less than complex and cost-effective.

  As a method for improving the quality, when recovering ethylene glycol from the crude glycol aqueous solution, the crude glycol aqueous solution is distilled to cut off a part of ethylene glycol, and together with ethylene glycol, aldehyde, acid, and those and ethylene glycol. Although a method for removing the reaction product has been proposed, the quality of ethylene glycol cut by fractional distillation is poor, and further, a fractionation tower is required, which increases the cost of ethylene glycol.

  In addition, many methods for chemically treating and purifying impurities in crude ethylene glycols have been proposed. For example, as a method for purifying crude ethylene glycols recovered from a process for producing a polyester from an aromatic dicarboxylic acid and ethylene oxide or ethylene glycol, a method of contacting with hydrogen in the presence of a hydrogenation catalyst has been proposed ( Patent Document 3). However, even if this method is simply applied to a crude glycol aqueous solution obtained from a process for producing ethylene oxide by vapor phase oxidation of ethylene, high-purity ethylene glycols could not be obtained.

  In Patent Document 4, an aqueous glycol solution produced by a process for recovering and purifying ethylene oxide obtained by direct oxidation of ethylene is concentrated by a conventional method, and a concentrated crude glycol aqueous solution (including mono-, di- and triethylene glycol) is obtained. 60 to 95% by weight) with an alkali, the pH is adjusted to 10 or more, preferably 12 to 14, and the aqueous alkaline glycol glycol solution is distilled under reduced pressure at a temperature lower than 180 ° C., preferably 120 to 160. The crude glycol aqueous solution is distilled at a temperature of ℃, and most of it is distilled. On the other hand, heavy impurities are removed from the bottom of the system to perform crude distillation (coarse distillation step), and then ethylene glycol obtained by the crude distillation. Is purified by distillation to produce high-purity ethylene glycol suitable for the production of synthetic fibers on an industrial scale. It has also been reported that can be.

  However, in the method described in the above-mentioned publication (Patent Document 4), the removal of impurities (aldehydes, organic acids, organochlorine compounds) is insufficient in heavy fraction cutting only by crude distillation, and thus obtained monoethylene There was a problem with respect to the quality of glycol, particularly with respect to ultraviolet transmittance.

  Patent Document 5 discloses a method for producing high-purity monoethylene glycols from a crude glycol aqueous solution produced in the recovery and purification process of ethylene oxide in the production of ethylene oxide by vapor phase catalytic oxidation of ethylene. The crude distilled glycol after dehydration and crude distillation is subjected to hydrogenation treatment with hydrogen gas in the presence of a hydrogenation catalyst at a temperature of 200 ° C. or lower, and then purified. A method is disclosed.

  However, when the hydrotreating method described in the above publication (Patent Document 5) is performed, a hydrotreating reactor, a catalyst, hydrogen, and the like are required, which is not economical, complicated in operation, and has problems in terms of equipment. there were.

Japanese Patent Publication No. 45-10324 JP 58-62124 A JP-A-51-1403 Japanese Patent Publication No. 45-9926 Japanese Examined Patent Publication No. 4-28247

8. Chemical Engineering Society, “Chemical Process”, pages 121-128, 9. Ethylene oxide / ethylene glycol (Tokyo Kagaku Dojin, published on March 25, 1998)

  Therefore, an object of the present invention is to provide high-purity monoethylene glycol from a recovered ethylene glycol raw material, which is excellent in quality of monoethylene glycol, particularly in ultraviolet transmittance, simple in operation and equipment, and excellent in manufacturing cost. The manufacturing method of this is provided.

  In order to solve the above-mentioned problems, the present inventors diligently studied a method for producing high-purity monoethylene glycol from a recovered ethylene glycol-containing liquid. As a result, an alkali heat treatment step was provided before the rough distillation step, and the raw material was recovered. By heat-treating an ethylene glycol-containing liquid in the presence of an alkaline substance, the impurities (aldehydes, organic acids, organic chlorine compounds) in the liquid are fixed in advance, and then subjected to a crude distillation step to be fixed. Impurities that have been stabilized and have a high boiling point are concentrated at the bottom of the crude distillation column, and are removed outside the system to prevent contamination of impurities in the next rectification step. And found that extremely high-purity monoethylene glycol excellent in quality, particularly in ultraviolet transmittance, can be obtained, and the present invention has been completed. It is intended.

  That is, the object of the present invention can be achieved as follows.

(1) In a method for producing high-purity monoethylene glycol using a recovered ethylene glycol-containing liquid as a raw material,
The recovered ethylene glycol-containing liquid is subjected to a heat treatment in the presence of an alkaline substance, and then a distillate obtained by roughly distilling the heat-treated ethylene glycol-containing liquid is purified. A method for producing ethylene glycol.

  (2) The production according to (1) above, wherein the recovered ethylene glycol-containing liquid contains a crude glycol produced in a process of recovering and purifying ethylene oxide when ethylene oxide is produced by catalytic vapor phase oxidation of ethylene. Method.

  (3) The above (1) or (2), wherein the alkaline substance is at least one selected from the group consisting of alkali metal hydroxides, carbonates, alkoxides, and alkaline earth metal hydroxides. ) Manufacturing method.

  (4) The manufacturing method as described in any one of said (1)-(3) whose usage-amount of the said alkaline substance is 0.01 weight% or more with respect to whole quantity of the collection | recovery ethylene glycol containing liquid.

  (5) The manufacturing method according to any one of (1) to (4), wherein a processing temperature in the heat treatment is 120 to 200 ° C., and a processing time is 1 hour or more.

  By the production method of the present invention, impurities are fixed to the bottom of the crude distillation column, and the impurity concentration in the distillate of the recovered ethylene glycol-containing liquid obtained from the column top is reduced. The quality of monoethylene glycol obtained by dehydrating this crude ethylene glycol aqueous solution and purifying it with a rectifying column is greatly improved. Furthermore, the UV transmittance increases, and fiber grade products can be acquired.

  Further, this method is simpler in operation than the hydrogenation treatment method and the like, does not require addition of hydrogen, and has an advantage in terms of equipment.

An example of a conventional typical ethylene oxide / ethylene glycol production process is shown. It is process schematic of the typical apparatus structure used for the manufacturing method of the high purity monoethylene glycol based on this invention.

The present invention uses a recovered ethylene glycol-containing liquid as a raw material, and a method for producing high-purity monoethylene glycol.
The recovered ethylene glycol-containing liquid is subjected to heat treatment in the presence of an alkaline substance (hereinafter also referred to as an alkali heat treatment step), and then the distillate obtained by distilling the heat-treated ethylene glycol-containing liquid is roughly It is characterized by being purified (hereinafter also referred to as a purification step). In the present invention, aldehydes, organic acids, organic chlorine compounds, and the like, which are impurities in the recovered ethylene glycol-containing liquid, can be effectively immobilized by performing an alkali heat treatment before the crude distillation. Therefore, these impurities remain in the falling liquid in the crude distillation operation, accumulate in the bottom of the crude distillation column, and can be efficiently removed out of the system, thus preventing impurities from entering the ethylene glycol rectification column. is there. Hereinafter, description will be given in the order of the alkali heat treatment step and the purification step.

(I) Alkaline Heat Treatment Step In the alkali heat treatment step, the recovered ethylene glycol-containing liquid is subjected to heat treatment in the presence of an alkaline substance. More specifically, the recovered ethylene glycol-containing liquid as a raw material is fixed in the presence of the alkaline substance and impurities before rough distillation in the presence of an alkaline substance in an amount necessary for fixing the impurities in the containing liquid. The heat treatment is performed under the condition that the conversion proceeds efficiently.

  As the recovered ethylene glycol-containing liquid of the raw material that can be used in the present invention, (1) a solution containing ethylene glycol produced as a by-product in the production of ethylene oxide by catalytic vapor phase oxidation of ethylene is recovered in an appropriate step; (2) In the production of ethylene glycol using ethylene oxide as a raw material, the recovered ethylene glycol of (1) and / or (2) above, in addition to the waste water or waste liquid containing a part of ethylene glycol recovered in an appropriate process In the containing liquid, unpurified ethylene glycol obtained by a hydrolysis reaction using ethylene oxide obtained by a production process by catalytic vapor phase oxidation of ethylene as a raw material (not a recovered ethylene glycol-containing liquid, manufactured as a target product, The one with the addition of ethylene glycol-containing liquid before being used for purification It is intended to be included within the scope of.

  As an example of the above (1), (a) a crude glycol aqueous solution produced in the recovery and purification process of ethylene oxide (for example, an absorption liquid for absorbing ethylene oxide contained in the ethylene oxide reactor outlet gas is partially used as a purge flow) Extracted water, aqueous glycol solution obtained by subjecting ethylene oxide containing impurities discharged from the ethylene oxide purification step to a hydrolytic reaction), (b) circulation between the ethylene oxide absorption step and the carbon dioxide absorption step and / or oxidation reaction step Ethylene glycol-containing liquid extracted from the system (for example, ethylene glycol obtained by subjecting ethylene glycol-containing waste water discharged from the carbon dioxide absorption process and ethylene oxide-containing condensate discharged from the heat exchanger at the outlet of the reactor to a hydrolysis reaction) Aqueous solution).

  Examples of the above (2) include: (a) waste liquid from the purification system of ethylene glycol, waste water (for example, ethylene glycol-containing waste water discharged from the dehydration process, or high purity monoethylene newly invented by the present inventors In a method for producing glycol, a side cut technique is introduced into a monoethylene glycol rectification column and monoethylene glycol is obtained from the side cut part. Ethylene glycol solution containing concentration impurities).

  These recovered ethylene glycol-containing liquids can be used singly or in combination of two or more. In general, as described in the prior art, since the crude glycol aqueous solution (1)-(a) is relatively produced as a by-product, the use of this can contribute to the reduction of the overall production cost. In addition, in this case, the crude glycol aqueous solution of (1)-(a) described above is usually provided together with the ethylene glycol production plant by catalytic vapor phase oxidation. It can be said that it is desirable to use the above solutions (2) to (1)-(b) in combination. Further, when the ethylene glycol concentration in the recovered ethylene glycol-containing liquid is low, it can be subjected to alkali heat treatment after dehydration and concentration to an ethylene glycol concentration of 60 to 95% by weight, preferably 80 to 90% by weight.

  The impurities contained in the recovered ethylene glycol-containing liquid include aldehydes, organic acids and organic chlorines as already described in the prior art. Therefore, the impurities which are the objects to be immobilized in the alkali heat treatment are aldehydes, organic acids and organic chlorines.

  In the alkaline heat treatment step, the alkaline substance that can be used is not particularly limited as long as it is a metal compound that dissolves in water and exhibits alkalinity. Alkoxides, alkaline earth metal hydroxides, and the like. Specifically, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium methoxide, sodium ethoxide Alkali metal alkoxides such as potassium methoxide and potassium ethoxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, etc., but good solubility in glycol, available at low cost Preferably, alkali metal hydroxides, carbonates, alkaline earth metal hydroxides, and the like are preferable because of their good thermal stability. In the present invention, one or more of these alkaline substances may be used.

  The amount of the alkaline substance used is not particularly limited as long as impurities contained in the recovered ethylene glycol-containing liquid can be suitably immobilized. It is 01 weight% or more, More preferably, it is 0.1 to 5 weight%, Most preferably, it is the range of 0.1 to 1 weight%. When the amount of the alkaline substance used is less than 0.01% by weight with respect to the recovered ethylene glycol-containing liquid, it is insufficient to immobilize impurities contained in the recovered ethylene glycol-containing liquid sufficiently. Allow the distillation of impurities not fixed together with ethylene glycol in the subsequent crude distillation process, and prevent the separation of monoethylene glycol into the rectification process because it cannot be easily separated and removed only by the conventional purification process. This is not preferable because it is difficult to obtain high-purity monoethylene glycol. On the other hand, when the amount exceeds 5% by weight with respect to the recovered ethylene glycol-containing liquid, a further effect corresponding to the amount of use cannot be obtained, and the amount of waste liquid when separating the alkaline substance is uneconomical. Etc. are not preferable.

  Further, the form of use of the alkaline substance is not particularly limited, but it can be said that it is preferable to use it in the form of an alkaline aqueous solution diluted to an appropriate concentration from the viewpoint of ease of handling and ease of mixing. . Further, the timing of the use (addition) of the alkaline substance to the recovered ethylene glycol-containing liquid is not particularly limited as long as the impurities can be optimally fixed by heat treatment. It can heat-process after adding and / or adding to a liquid.

  The heat treatment conditions in the alkali heat treatment step are not particularly limited as long as the alkaline substance can react with the impurities and can be immobilized. Preferably, the treatment temperature is 120 to 200 ° C., preferably 140 to 180 degreeC, Especially preferably, it is 150-165 degreeC, Although processing time should just be 1 hour or more, Preferably it is 2 to 5 hours, Most preferably, it is 2-3 hours. When the treatment temperature is less than 120 ° C., the impurities are not sufficiently immobilized by reaction with an alkaline substance, which is not preferable. On the other hand, when the temperature exceeds 200 ° C., odor and coloration are generated in the obtained monoethylene glycol, which is not preferable. Further, a pressure (internal pressure) generated thermodynamically by high-temperature treatment is added, so a pressure-resistant container is necessary. Therefore, an effect commensurate with further increase in temperature cannot be obtained, which is uneconomical. When the treatment time is less than 1 hour, the immobilization reaction of impurities by reaction with an alkaline substance is not sufficient, and unreacted impurities that are not separated by distillation are mixed in the purification step, and the resulting monoethylene glycol The purity is poor, and the quality, in particular, the ultraviolet transmittance is lowered, which is not preferable because it can be used only for limited applications. On the other hand, if it exceeds 5 hours, the impurities can be sufficiently fixed by using the alkaline substance, and there is no particular problem in this respect, but the heat treatment is continued even after 5 hours. This is not preferable because it is uneconomical because an effect corresponding to the above cannot be obtained.

  In addition, the pressure condition for the heat treatment is not particularly limited as long as it is maintained at a pressure equal to or higher than the vapor pressure of the liquid to be processed at the processing temperature so that the liquid to be processed does not boil.

  The alkali heat treatment apparatus that can be used in the alkali heat treatment step is not particularly limited as long as it is an apparatus having an appropriate heating means, but preferably the temperature specified above for the recovered ethylene glycol-containing liquid. Heat treatment time as defined above (ie, reaction time between impurities and alkaline substance, or residence time of recovered ethylene glycol-containing liquid) However, it is possible to use only a preheater such as a multi-tube heat exchanger as long as the residence time can be obtained.

(II) Monoethylene glycol purification step Next, in the purification step of the present invention, the recovered ethylene glycol-containing liquid treated in the alkali heat treatment step (I) is roughly distilled, and the resulting distillate is obtained. It is mixed and processed in the middle of the process of the facility for producing ethylene glycol (for example, the supply liquid to the dehydration tower) by appropriately treating in accordance with a conventionally known purification method of a recovered ethylene glycol-containing liquid, or by a hydrolysis reaction of ethylene oxide. As long as the desired monoethylene glycol can be purified and separated, it is not particularly limited, and a conventionally known improved method as exemplified in the prior art can be used in combination as appropriate. . However, in that case, it is necessary to provide devices and means for these improved parts, and since additives and the like used for these are also required to increase costs, for example, as shown in FIG. It can be said that it is desirable to carry out separation and purification with a simple apparatus and simple operation (and a small number of processing steps).

  Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings.

  FIG. 2 is a schematic diagram of typical steps (apparatus) used in the method for producing high-purity monoethylene glycol according to the present invention.

  As shown in FIG. 2, in this embodiment, a raw material recovered ethylene glycol-containing liquid (for example, a crude glycol aqueous solution produced in the recovery and purification process of ethylene oxide in the production of ethylene oxide by catalytic vapor phase oxidation of ethylene; 95 wt%, preferably 80 to 95 wt%) is introduced into the alkali heat treatment apparatus 101 through the pipe 103. At this time, an alkaline aqueous solution corresponding to an alkali amount of 0.01% by weight or more with respect to the recovered ethylene glycol-containing liquid is supplied from the alkali storage tank (not shown) to the recovered ethylene glycol in the pipe 103 through the pipe 102. Add to glycol-containing solution. Thereafter, using the alkali heat treatment apparatus 101, the recovered ethylene glycol-containing liquid is subjected to heat treatment for 1 hour or more at the treatment conditions specified above, that is, at a treatment temperature of 120 to 200 ° C. As a result, aldehydes, organic acids, organic chlorines and the like, which are impurities in the recovered ethylene glycol-containing liquid, can be reacted and immobilized extremely efficiently and effectively. Thereby, ethylene glycols can be separated on the distillation side and impurities fixed on the kettle liquid side can be separated by a simple distillation operation thereafter. After the alkali heat treatment, the treatment liquid in the alkali heat treatment apparatus 101 is introduced through a pipe 107 from a treatment liquid supply nozzle portion provided at an intermediate point of the rough distillation tower 105. In the crude distillation tower 105, the treatment liquid is distilled under reduced pressure, usually under a reduced pressure of 20 to 100 Torr. As a result, 90 to 99% by weight of the introduced processing liquid evaporates from the top of the crude distillation column 105. Distilled components such as evaporated ethylene glycol and water through the pipe 111 are condensed and liquefied by the cooling means provided on the pipe 111 path, so that an ethylene glycol aqueous solution is obtained. This ethylene glycol aqueous solution is further sent to the dehydration tower 109 through the pipe 111. On the other hand, the pot liquid containing impurities fixed by 1 to 10% by weight of alkali heat treatment remaining at the bottom of the crude distillation column 105 can be extracted out of the system through the pipe 113.

  The subsequent purification process of monoethylene glycol may be carried out in the same manner as in the conventional method. That is, the ethylene glycol aqueous solution sent to the dehydration tower 109 is fractionated into water and ethylene glycol by vacuum distillation. The water vapor exiting from the top of the dehydrating tower 109 is distilled through the pipe 115, and is condensed and liquefied by the cooling means on the path of the pipe 115 and discarded outside the system. On the other hand, an ethylene glycol liquid containing substantially no water is obtained at the bottom of the dehydrating tower 109. The ethylene glycol liquid is extracted from the bottom of the dehydration tower 109 through the pipe 119 and sent to the rectification tower 117. The ethylene glycol liquid sent to the rectifying column 117 is distilled under reduced pressure and fractionated into a low boiling point component monoethylene glycol, a high boiling point component diethylene glycol, and the like. The monoethylene glycol vapor distilled from the top of the rectifying column 117 is converted into a monoethylene glycol liquid that has been fully condensed and liquefied by the condenser 121 provided on the path of the pipe 120. A part of the monoethylene glycol liquid is returned to the rectification column 117 through the pipe 123 and the remaining monoethylene glycol liquid is collected through the pipe 124 into an MEG product storage tank (not shown). On the other hand, the diethylene glycol liquid remaining in the bottom of the rectifying column 117 is sent to a diethylene glycol treatment step outside the system through the pipe 125, and is processed and recovered.

  Although the above is the manufacturing method of the high purity monoethylene glycol in this embodiment, this invention is not specifically limited to these.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
The following experiment was conducted according to the schematic diagram of the apparatus (process) shown in FIG.

  As the recovered ethylene glycol-containing liquid, a crude glycol aqueous solution (containing 85% by weight as ethylene glycols) generated in the ethylene oxide recovery and purification process when ethylene oxide was produced by catalytic vapor phase oxidation of ethylene was used. The recovered ethylene glycol-containing liquid is fed to the heat treatment apparatus 101 through the pipe 103 at 37 liters / minute, and a 48% potassium hydroxide aqueous solution is added at 0.19 liter / minute through the pipe 102 to preheat the heat treatment apparatus 101. The mixture was preheated to 150 ° C. with a reactor, and then heat-treated for 2 hours at 150 ° C. with a reactor. After the treatment, the recovered ethylene glycol-containing liquid (treatment liquid) is fed to the crude distillation tower 105 through the pipe 107, and the crude distillation is performed by reducing the pressure to 50 torr while keeping the temperature of the bottom liquid of the crude distillation tower 105 at 136 ° C. or lower. went. 95% by weight of the treatment liquid was distilled from the top of the crude distillation column 105 as vapors of ethylene glycol and water. On the other hand, the pot liquid containing 5% by weight of immobilized impurities remaining in the crude distillation column 105 was extracted through the pipe 113. The ethylene glycol and water vapors distilled from the top of the crude distillation column 105 are all condensed and liquefied by a condenser provided on the path of the pipe 111 and fed to the dehydration column 109 as an ethylene glycol aqueous solution. While maintaining the bottom liquid temperature of the dehydration tower 109 at a temperature at which no water remains in the bottom liquid (ethylene glycol liquid) and ethylene glycol does not distill from the top of the dehydration tower 109, the pressure is reduced to 70 torr. The water was fractionated into water and dehydrated through the pipe 115. The ethylene glycol liquid substantially free of water in the dehydration tower 109 is extracted from the dehydration tower 109 through the pipe 119, introduced into the monoethylene glycol rectification tower 117 reduced to 150 torr, and distilled from the top of the rectification tower 117. The vapor of monoethylene glycol to be used was a monoethylene glycol liquid that was fully condensed and liquefied by a condenser 121 provided on the path of the pipe 120. A part of this monoethylene glycol liquid was returned to the rectifying column 117 through the pipe 123 and recovered, and the remaining monoethylene glycol liquid was collected in the MEG product storage tank through the pipe 124, thereby obtaining a monoethylene glycol product. On the other hand, the column bottom liquid of the rectifying column 117 was taken out through the pipe 125. For the monoethylene glycol product collected in the MEG product storage tank, the ultraviolet transmittance at 220 nm was measured with an absorptiometer (manufactured by Hitachi, Ltd .: U-3200). The obtained results and alkaline heat treatment conditions are shown in Table 2 below.

Comparative Example 1
Using the same recovered ethylene glycol-containing liquid as in Example 1 and feeding this recovered ethylene glycol-containing liquid to the crude distillation tower without subjecting it to an alkali heating treatment, the crude distillation, dehydration and purification were performed in the same manner as in Example 1. The ultraviolet light transmittance at 220 nm was measured in the same manner as in Example 1 for the comparative monoethylene glycol product obtained by purification by distillation. The obtained results and alkaline heat treatment conditions are shown in Table 2 below.

101 alkali heat treatment equipment,
102, 103, 107, 111, 113, 115, 119, 120, 123, 124, 125 piping,
105 Coarse distillation tower,
109 dehydration tower,
117 rectifying tower,
121 Condenser.

Claims (5)

In a method for producing high-purity monoethylene glycol using a recovered ethylene glycol-containing liquid as a raw material,
Presence of alkaline substance in the alkaline treatment equipment that has heating means before feeding the recovered ethylene glycol-containing liquid to the crude distillation column at a pressure equal to or higher than the vapor pressure (except for the same pressure as the vapor pressure) A process for producing high-purity monoethylene glycol, characterized by purifying a distillate obtained by subjecting a heat treatment to the bottom and then roughly distilling the heat-treated ethylene glycol-containing liquid. The manufacturing method according to claim 1, wherein the heat treatment has a treatment temperature of 120 to 200 ° C. and a treatment time of 1 hour or more. 3. The production method according to claim 1, wherein the recovered ethylene glycol-containing liquid contains a crude glycol produced in a process of recovering and purifying ethylene oxide when ethylene oxide is produced by catalytic vapor phase oxidation of ethylene. The alkaline substance is a hydroxide of alkali metal, carbonate, alkoxide, any one of claims 1 to 3 is of at least one comprising selected from the group consisting of alkaline earth metals The manufacturing method as described in. The manufacturing method according to any one of claims 1 to 4 , wherein an amount of the alkaline substance used is 0.01% by weight or more based on a total amount of the recovered ethylene glycol-containing liquid.

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