JPS6220976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing ethylene glycol monoethyl ether acetate (hereinafter referred to as GEAc). Specifically, the present invention relates to a method for reacting acetic acid and ethylene glycol monoethyl ether (hereinafter referred to as GE) to obtain the desired GEAc in high yield. GEAc is used as a water-soluble high-boiling solvent in a wide range of fields, including acrylic, epoxy, and urethane water-soluble resin paints. This GEAc is usually obtained by an esterification reaction between acetic acid and GE, and at this time, an acid catalyst such as sulfuric acid, phosphoric acid, benzenesulfonic acid, etc. is used as an esterification catalyst. When separating such catalysts from the reaction solution after the reaction, it is normal to go through a process such as neutralization and washing with water, but the separation and recovery operations are complicated because GE and GEAc have extremely high solubility in water. However, there is also the disadvantage that wastewater treatment costs are high. As an alternative to these acid catalysts, it is possible to use solid acid catalysts, especially cation exchange resins.
A process has been proposed that can overcome the above drawbacks because of the ease of separation from the reaction solution (see, for example, US Pat. No. 3,404,175). The present inventors conducted research and development on a method for obtaining GEAc from acetic acid and GE in high yield using this cation exchange resin as a catalyst, and obtained several findings that led to the completion of the present invention. I've reached it. First of all, it has been found that the use of cation exchange resins as acid catalysts requires a reaction temperature of 50-100°C, preferably 60-90°C. This is because it has been found that when the temperature exceeds 100°C, in addition to problems with the heat resistance (life span) of the resin itself, the impurity generation reaction in the esterification reaction becomes too large to be ignored. On the other hand, low temperatures are not preferable because the reaction rate may become extremely low. Next, the molar ratio of acetic acid to GE is such that GE always needs to be in excess. The molar ratio of ethylene glycol monoethyl ether to acetic acid is preferably in the range of more than 1 and less than 2. Although increasing the molar ratio to 2 times or more has the advantage of increasing the conversion rate of raw material acetic acid to GEAc, the excess GE It turned out to be uneconomical because the cost of separating and recovering it from the reaction products outweighed its benefits. On the other hand, even if you try to increase the conversion rate of GE to GEAc by setting the molar ratio below 1, the excess acetic acid attacks GE and the product GEAc, causing side reactions such as decomposition reactions, resulting in the target GEAc. The selectivity of GE and acetic acid to this method becomes low, which, together with the complexity of subsequent steps, results in an extremely undesirable situation. According to the findings of the present inventors, in addition to the above findings, it was also found that the conversion rate of acetic acid should be suppressed to a maximum of 97%. Although the relationship between conversion rate and selectivity varies somewhat depending on the above molar ratio and reaction temperature, when the conversion rate of acetic acid reaches around 96-97%, the selectivity to the target substance GEAc decreases rapidly. This is because it has been found that there is a tendency to The present invention provides an industrially advantageous method for producing GEAc by making various improvements based on the above findings. The reaction between acetic acid and GE is an esterification reaction,
Since this is an equilibrium reaction, if the produced water accumulates in the reaction system, the apparent reaction rate will inevitably decrease, and the conversion rate will not reach the desired level. The water produced there is promptly removed from the reaction system,
Unreacted raw materials must be further reacted. As a measure for this purpose, the following method is adopted in the present invention. A. Directly remove produced water from the reaction system. Although a small amount of acetic acid, GE, and GEAc are distilled out, a separate distillation column is used to separate the distilled water and acetic acid, GE, and GEAc, and the recovered acetic acid, GE, and GEAc are recycled to the reaction system. B. An azeotropic agent that forms an azeotropic composition with water is added in advance to the reaction raw material mixture, so that the water produced by the reaction is immediately distilled out of the system together with the azeotropic agent. The distilled water and the entrainer are separated, and the entrainer is recycled to the reaction system again. C: No azeotropic agent is added to the reaction system; a part or all of the reaction liquid is taken out from the reaction system, an azeotropic agent is added thereto, and the water produced is removed by azeotropic distillation. The reaction solution from which water has been removed is subjected to the esterification reaction again. The present invention can be carried out by method A above. In particular, while maintaining the reaction temperature at 50 to 100℃, and at the same time
When reacting with Hg (absolute pressure) under reduced pressure, the present invention can be carried out without the need for an entrainer such as benzene. The amount of distilled water and small amounts of acetic acid, GE, and GEAc cannot be ignored, but by separating them using another distillation method and supplying the bottom liquid to the reaction system, the reaction can actually be carried out. is possible. On the other hand, compounds that can be particularly suitably employed in the present invention as entrainers that can be used in methods B and C above are benzene, cyclopentane, and nonane,
These can be recognized as stable compounds that do not exhibit an azeotropic relationship with acetic acid, GE, or GEAc, and are unlikely to cause decomposition reactions. Moreover, these compounds may be used in the form of a mixture. Although the present invention is carried out by these methods A, B, and C, either a batch one-stage reaction format or a continuous multi-stage reaction format can be adopted, and the reaction liquid is removed from the reaction system to remove the produced water. A reaction liquid circulation method in which the reaction liquid is taken out to the reactor and circulated back to the reaction system may be used in combination with these methods. Specifically, for example, according to Method A, the object of the present invention can be sufficiently achieved with a batch one-stage reaction format, and in Methods B and C, both a batch one-stage reaction format and a continuous multi-stage reaction format can be advantageously employed. Moreover, it is also possible to advantageously adopt a reaction liquid circulation system. The cation exchange resin used in the present invention is a commercially available polystyrene sulfonic acid type resin (for example, manufactured by Dow, Dowex HCRW, Mitsubishi Kasei, Diaion PK, etc.). The method of use is to feed the raw material mixture under heating into a reactor filled with this catalyst and carry out the esterification reaction.
There are fixed bed catalyst methods in which the produced water is distilled off in an evaporator equipped with a distillation column, and the bottom liquid is supplied to the same reactor or the next reactor, and a method in which the catalyst is dispersed in the reactor and the reaction is carried out with stirring. There is a usage method in which the moisture generated is directly distilled off and separated. Thus, the gist of the present invention can be defined as follows. That is, when producing ethylene glycol monoethyl ether acetate by reacting acetic acid and ethylene glycol monoethyl ether using a cation exchange resin as a catalyst, the molar ratio of ethylene glycol monoethyl ether and acetic acid exceeds 1. The range is 2 or less,
The reaction is carried out at a reaction temperature of 50 to 100°C, preferably 60 to 90°C, and the reaction is carried out while removing the produced water from the reaction system and when the conversion rate of acetic acid is in the range of 80 to 97%. GEAc characterized by stopping
It is a manufacturing method, in particular, the reaction system is heated to 760 to 10 mmHg.
The reaction is carried out under a pressure of (absolute pressure), preferably 400 to 40 mmHg (absolute pressure), while removing produced water from the reaction system. Furthermore, when removing produced water from the reaction system, benzene, cyclo This paper proposes a method in which at least one kind selected from the group consisting of pentane and nonane is used as an azeotropic agent.In particular, it discloses a method in which the reaction is carried out while coexisting an entraining agent in the reaction system. This study clarifies that the objective can be achieved by using benzene in an amount not more than twice the molar amount of acetic acid. Next, a process considered to be most preferable for carrying out the present invention will be described in detail based on the attached FIGS. 1 and 2. First, the batch one-stage reaction system (FIG. 1) will be explained. Ethylene glycol monoethyl ether and acetic acid were charged into the evaporator in a molar ratio of more than 1 but not more than 2, and benzene and acetic acid were charged in a molar ratio of not more than 2.0, and this reaction mixture was circulated to the reaction tower. do. The reaction column used is one filled with the above-mentioned commercially available polystyrene sulfonic acid ion exchange resin as a catalyst. The reaction temperature is 50 to 100℃, preferably 60 to 90℃, heated in a jacket or inner tube, and the pressure is 760 to 760℃.
It is carried out in the range of 40mmHg (absolute pressure). The water produced in the reaction column is sent to the distillation column together with GEAc, unreacted acetic acid, and GE, and the produced water is distilled out together with benzene.The water is then passed through a condenser and sent to the separation tank, where the benzene is refluxed to the distillation column and the water is removed from the system. Ru. The reaction is completed at an acetic acid conversion rate of 80-97%. In addition, if benzene is not mixed into the reaction solution using this device, the reaction temperature may be maintained at 50 to 100°C, and the pressure at this time may be in the range of 400 to 10 mmHg (absolute pressure). objective is achieved. In addition,
It is also possible to remove water produced by the reaction from the system by simply allowing the reaction to occur in the distillation column without substantially allowing benzene to be present in the reaction column. In this case, the reaction temperature will be in the range of 75 to 100°C and the pressure will be in the range of 400 to 40 mmHg (absolute pressure). The pressure is defined here on the assumption that the operating pressure in the distillation column is linked to the reaction pressure in the reaction column. Regarding the continuous multi-stage reaction type (Figure 2), see
Ethylene glycol monoethyl ether and acetic acid are continuously fed to the stage reaction tower at a molar ratio of more than 1 and less than 2, and benzene and acetic acid are continuously fed at a molar ratio of less than 2.0. The reaction tower temperature is 50-100℃, and the acetic acid conversion rate is 40-100℃.
It is 70%. The water produced in the reaction column is distilled off together with benzene in a distillation column. Distilled water and benzene pass through a separation tank, where water is removed from the system and benzene is returned to the distillation column as reflux.
GEAc, benzene, unreacted GE, and acetic acid are led to the next reaction column from the bottom of the distillation column. The temperature of the reaction tower is also maintained at 50 to 100°C, and the total conversion of acetic acid is adjusted to be in the range of 80 to 97% in the reaction tower. The water produced in the reaction column is removed from the system by a distillation column similar to the distillation column, and GEAc, benzene, unreacted GE, and acetic acid are extracted from the bottom of the distillation column, and then sent to the next purification system (not shown). benzene,
Furthermore, unreacted GE and acetic acid are separated and recycled to the reaction tower. At this time, if necessary, this collection
Part or all of the GE and acetic acid can also be recycled to the inlet of the reaction column. In addition, as in FIG. 1, when benzene is not substantially present in the reactor and the reaction is simply carried out in a distillation column, the present invention can be operated in the same manner by controlling the reaction temperature to a range of 75 to 100°C. can achieve the objectives of Next, the present invention will be explained in detail with reference to examples. Examples 1 to 4, Comparative Examples 1 to 2 Ion exchange resin Dowex HCRW2 was applied to the glass double heat exchange type inner tube with an inner tube of 30 mmφ and a height of 150 mmH.
(trade name manufactured by The Dow Chemical Company) was filled and fixed and used as a reaction tower. McMahon is used as a distillation device in a glass tube with an inner diameter of 40 mmφ and a height of 350 mmH.
A distillation column with a reflux device filled with 300 ml and a 14-necked flask connected as an evaporator as shown in the diagram were used (see Figure 3 below). This evaporator was charged with 798 g of a mixture of acetic acid and GE in a molar ratio of 1:1.2 and acetic acid and benzene in a molar ratio of 1:1.25. This reaction liquid was fed to the reaction column at a rate of 5 per hour, and the outlet reaction liquid was recycled to the distillation column. The water produced in this reaction column was distilled off from the top of the distillation column together with benzene, the water was removed from the system, and all of the benzene was returned to the distillation column as reflux. Since the composition of the reaction solution changes as the reaction progresses, the reaction was carried out for 6 hours while adjusting the pressure so that the temperature of the evaporator and the reaction tower remained constant. The initial reaction pressure was 760 mmHg (absolute pressure), and the reaction completion pressure was 400 mmHg (absolute pressure). As a result of analysis of each component in the reaction product, the conversion rate of acetic acid and
The selectivity to GEAc was 94.5% and 98.5%, respectively. Note that ethyl acetate, ethylene glycol diacetate, and ethylene glycol monoether were predominant as by-products. Reactions were carried out under various conditions as described above and the reaction results are shown in Table 1. Example 5 Using the same equipment as in Examples 1 to 4, acetic acid and GE mixed in advance at a molar ratio of 1:1.2 were placed in an evaporator.
I put in 673g. This reaction liquid was fed to the reaction column at a rate of 4 hours per hour, and the outlet reaction liquid was recycled to the distillation column. The benzene reflux rate of this distillation column is
0.6, the water produced in the reaction column was distilled out from the top of the distillation column along with benzene, the water was removed from the system, and the benzene was returned to the distillation column as reflux. Since the liquid composition changes as the reaction progresses, the pressure was adjusted so that the temperature of the evaporator and reaction tower remained constant at 90°C. The initial reaction pressure was 250 mmHg, and the reaction completion pressure was 75 mmHg. The results are shown in Table 2.

【table】

【table】

【table】 [Brief explanation of the drawing]

1 and 2 are examples of flow sheets for implementing the present invention. FIG. 3 is a simple flow sheet for the experiment of Example 1.

Claims (1)

[Claims] 1. When producing ethylene glycol monoethyl ether acetate by reacting acetic acid and ethylene glycol monoethyl ether using a cation exchange resin as a catalyst, the mole of ethylene glycol monoethyl ether and acetic acid is The ratio is in the range of more than 1 and less than 2, and the reaction temperature is in the range of 50 to 100 ° C. While removing the water produced from the reaction system, the reaction is carried out so that the conversion rate of acetic acid is in the range of 80 to 97%. 1. A method for producing ethylene glycol monoethyl ether acetate, which comprises stopping the process when the reaction occurs. 2. The method according to claim 1, wherein the pressure of the reaction system is set in the range of 760 to 10 mmHg (absolute pressure) and produced water is directly removed from the reaction system. 3. The method according to claim 1, wherein the pressure of the reaction system is set in the range of 760 to 10 mmHg (absolute pressure), and an azeotropic agent is present in the reaction system to remove produced water. 4. The method according to claim 3, wherein at least one selected from the group consisting of cyclopentane, nonane and benzene is used as the entrainer. 5. The method according to claim 1, wherein a part of the reaction liquid is extracted from the reaction system, produced water is removed from the extracted liquid, and the remainder is returned to the reaction system while performing the reaction. 6. The method according to claim 5, wherein an azeotropic agent is allowed to coexist as a method for removing produced water.