JP4923183B2 - Method for producing chloroethylene carbonate - Google Patents

Description

  The present invention relates to a method for producing chloroethylene carbonate (CEC) in which ethylene carbonate (EC) is photochlorinated, and more particularly to a method for producing CEC with few impurities that are difficult to separate and remove by distillation purification.

  CEC is synthesized by chlorinating EC.

  CEC is a material used as a raw material when producing vinylene carbonate (VC).

  VC synthesized by dehydrochlorinating CEC is a substance useful as a solvent and additive for lithium ion secondary battery electrolyte, and highly purified VC is required to improve battery performance. It has been. In this application, impurities containing chlorine are particularly noticed, and high purity VC having a total chlorine content of 100 ppm or less, preferably 20 ppm or less is required. When VC is produced using CEC having low purity, the purity of VC is also lowered, and it is difficult to synthesize high purity VC. Therefore, a product with less impurities is required at the CEC stage.

  As a method for producing CEC by chlorinating EC, Non-Patent Document 1 describes a production method by photochlorination reaction with chlorine gas under light irradiation. Patent Document 1 discloses a production method using a chlorinating agent such as sulfuryl chloride in the presence of a radical initiator, Patent Document 2 discloses a production method using a halogenated sulfuryl chlorinating agent in the presence of AIBN, and Patent Document 3 Describes a production method using a sulfuryl halide as a chlorinating agent under ultraviolet (UV) irradiation.

JP-A-11-171882 Special Table 2002-529461 Special Table 2002-529460 J. et al. Am. Chem. Soc. , 75, 1263-1264 (1953)

However, even when EC is chlorinated by any of these methods, the obtained CEC contains not a few impurities (hardly separable impurities) that are difficult to separate and remove by distillation purification. Currently.
Distillation purification of EC, which is a raw material, and dichloroethylene carbonate (DCEC), which is produced by perchlorination of successive reactions, has a relatively low boiling point (saturated vapor pressure is separated) from CEC, which is the main component. This process can be separated and removed relatively easily. On the other hand, in the by-product generated by the chlorination reaction, multiple peaks of compounds having boiling points close to the main component CEC (saturated vapor pressure close) are detected, and even when distillation purification is performed, It is difficult to increase the purity of CEC. An attempt to remove these by-products in order to improve the purity results in a low yield.
Here, the hard-to-separate impurities having a chlorine atom in the molecule are a group of components detected in the GC chromatogram obtained under predetermined conditions in the vicinity of the CEC peak, particularly behind the peak. When VC is synthesized, the quality is likely to deteriorate. In order to obtain CEC suitable as an intermediate for the production of VC, it is necessary to suppress the production of by-products, particularly this hardly separable impurity, as much as possible at the stage of chlorination reaction.

  Therefore, the present invention has been made to solve the above technical problem, and can suppress the generation of difficult-to-separate impurities among by-products, and can produce vinylene carbonate (VC). It aims at providing the manufacturing method of chloroethylene carbonate (CEC) suitable as an intermediate body.

As a result of intensive studies to solve such problems, the inventors of the present application made ethylene carbonate and aromatic chloride coexist in a CEC production method in which ethylene carbonate and chlorine gas were reacted under light irradiation. By introducing chlorine gas into the system, among the by-products generated during the chlorination reaction under light irradiation, it has been found that impurities that are difficult to separate by distillation purification are greatly reduced, and the present invention has been completed. .

That is, in the method for producing chloroethylene carbonate of the present invention, chlorine gas is introduced into a system in which ethylene carbonate and aromatic chloride coexist, and ethylene carbonate and chlorine gas are reacted under light irradiation.

In the method for producing chloroethylene carbonate of the present invention, the amount of impurities in the reaction product is reduced because (1) the aromatic chloride coexists with EC, so that the aromatic chloride is coordinated with EC. , Making the chlorination reaction less likely to generate impurities, and (2) the decomposition reaction that co-ordinates with the target product CEC and produces impurities by the coexistence of aromatic chloride It is possible that it is difficult to occur. Therefore, even if a relatively small amount of aromatic chloride is present, there is an effect of reducing the generation of impurities.

That is, by introducing chlorine gas into a system in which ethylene carbonate and aromatic chloride coexist, and reacting ethylene carbonate and chlorine gas under light irradiation, chloroethylene carbonate that can be easily purified by distillation is obtained. It can be produced with high yield and high selectivity.

In the method for producing chloroethylene carbonate of the present invention, chlorine gas is introduced into a system in which ethylene carbonate and 0.1 to 7.0 times moles of aromatic chloride with respect to ethylene carbonate coexist, It is preferable to react ethylene carbonate and chlorine gas. In particular, a system in which an aromatic chloride of about 10 times mol or more with respect to the chlorinated substance coexists is called a so-called solvent system. In particular, an effect manifested in the solvent system is called a solvent effect. In the production method of chloroethylene carbonate, the abundance ratio of aromatic chloride is small, and it is judged that the mechanism is different from the general solvent effect.

In the method for producing chloroethylene carbonate of the present invention, if the amount of aromatic chloride coexisting with ethylene carbonate is small, the effect of reducing hardly separable impurities is small. Therefore, the amount of the aromatic chloride coexisting in the reaction system is preferably 0.1 times mol or more, more preferably 0.3 times mol or more with respect to ethylene carbonate.

On the other hand, when the amount of the aromatic chloride coexisting with ethylene carbonate exceeds 1.0 times in molar ratio to ethylene carbonate, the effect of reducing difficult-to-separate impurities becomes dull. In an actual production apparatus, if the amount of the aromatic chloride to be coexisted is increased, the volume efficiency is deteriorated and the productivity is lowered, which is uneconomical. Therefore, the amount of the aromatic chloride to be coexisted is preferably 7.0 times mol or less, more preferably 3.5 times mol or less with respect to ethylene carbonate. The aromatic chloride that coexists with ethylene carbonate is preferably monochlorobenzene, dichlorobenzene, trichlorobenzene or the like .

  The light source used for light irradiation for photochlorination is not particularly limited as long as the wavelength peak is in the ultraviolet region such as 313 and 365 nm, but a high-pressure mercury lamp or the like can be used. An internal irradiation type reaction vessel is preferable in terms of light efficiency, but an external irradiation type reaction vessel can also obtain the effect.

  The reaction temperature for photochlorination must be equal to or higher than the melting point (36 to 38 ° C.) of EC as a raw material, and if it is set low, the chlorination reaction rate decreases (reactivity itself decreases). preferable. When the reaction temperature is high, the amount of by-products increases, so that it is preferably 80 ° C. or lower, more preferably 70 ° C. or lower.

As a way of thinking about the end point of the photochlorination reaction, it is preferable to terminate the reaction with reference to the content (concentration) of a specific impurity in consideration of impurity removal in a subsequent process.
For example, in the stage of the photochlorination reaction, the production of difficult-to-separate impurities is suppressed and the content is kept low. The content of is preferably 2% or less, and more preferably 1.5% or less.
Since DCEC can be easily separated by distillation, any amount can be used from the viewpoint of removal. However, if the content of DCEC is too large, the amount of distillation removed and the amount of main components distilled off accompanying this increase, and the amount of various impurity components increases as the reaction proceeds. For this reason, the content of DCEC at the end point of the reaction is preferably 8% or less, and more preferably 7% or less.
In practice, the production amount of CEC as the main component can be ensured to some extent, and the reaction can be completed with a degree of chlorination in which either DCEC or hardly separable impurities reach a target content (concentration). Here, the chlorination degree at the end point of the reaction is preferably 0.70 to 1.00, and more preferably 0.75 to 0.90.

  According to the present invention, when producing chloroethylene carbonate (CEC) by photochlorination of ethylene carbonate (EC), it is possible to greatly reduce the amount of difficult-to-separate impurities produced, and to reduce the CEC purification cost. At the same time, the purity of CEC after purification by distillation can be easily improved. Furthermore, when CEC obtained by the production method of the present invention is used as an intermediate for producing vinylene carbonate (VC), it is expected that the purification cost of VC can be reduced.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the examples disclosed herein.

<Example 1>
A reaction vessel equipped with a chlorine gas inlet, a thermocouple, an exhaust port connected to the exhaust gas removal device via a condenser, etc. coexists with a predetermined amount of EC and monochlorobenzene in a molar ratio of 0.33 to EC. After the inside of the system was purged with nitrogen, the reaction system was heated to 60 ° C., and a 200 W high pressure mercury lamp was turned on and irradiated with light from a position 15 cm away from the reaction vessel. A predetermined amount of chlorine gas was supplied to start the reaction so that the reaction temperature was kept at 60 ° C. The reaction was terminated when the DCEC content was about 6.0% or the content of difficult-to-separate impurities was 2.0% or less, the supply of chlorine gas was stopped, and the reaction was completed.

  Sampling of the reaction solution was carried out at regular intervals from the start of the reaction, gas chromatography (apparatus: GC14B (manufactured by Shimadzu Corporation), column: TC-1701, (0.25 mm IDX 30 m, film thickness 1 μm, manufactured by GL Sciences) Detector: FlD, INJ (vaporization chamber temperature): 200 ° C., DET (detector temperature): 200 ° C., column temperature: 140 ° C. is maintained for 5 min, and the temperature is increased to 150 ° C. at a rate of 1 ° C./min. In addition, the temperature was raised to 250 ° C. at a rate of 5 ° C./min, and then maintained at 250 ° C.), and each peak of EC, CEC and DCEC was identified by GC-MS analysis. . In the GC chromatogram of each reaction solution, a plurality of difficult-to-separate impurities having at least chlorine atoms in the molecule were detected after the CEC peak. The retention time of each component is DCEC: 6.6 min, EC: 11.4 min, CEC: 13.6 min, and hardly separable impurities detected after CEC in the retention time exceed 13.6 min and reach 30 min. This is the sum of the components detected. The quantitative analysis results of Example 1 are shown in Table 2. The results of GC analysis of the reaction solution after 16 hours are EC: 15.2%, CEC: 75.6%, DCEC: 4.2%, and the total number of difficult-to-separate impurities detected after CEC at a retention time of 0. The chlorination degree was 9% and 0.89.

  The degree of chlorination is a numerical value for evaluating how much chlorine is substituted. When the degree of chlorination is 1, it indicates that the same amount of chlorine as the raw material is substituted. In the following evaluation, EC = 0, CEC = 1, DCEC = 2, difficult-to-separate impurities detected after CEC = 1, and other = 1, and the chlorination degree of the reaction solution sampled at each time is expressed by the following equation: It was calculated according to However, the value of the composition amount used the GC detection intensity ratio as it is.

  Chlorination degree = {(EC composition amount (%)) × 0 + (CEC composition amount (%)) × 1 + (DCEC composition amount (%)) × 2 + (difficult-to-separate impurity amount (%) detected after CEC) ) × 1 + (other composition amount (%)) × 1} / 100

  305.0 g of the reaction solution thus obtained was distilled under reduced pressure using a distillation column having a theoretical plate number of 21 under a reflux ratio of 5, and a rectified fraction 119 having a temperature of 112 to 116 ° C./17 to 20 mmHg. .8 g was obtained. The distillation yield was 68.4% based on CEC, the purity of CEC was 99.31%, and the content of hardly separable impurities was 0.12%.

<Example 2>
As shown in Table 1, the photochlorination reaction was carried out in the same manner as in Example 1 except that the molar ratio of monochlorobenzene coexisting with EC to EC was 0.66 times. The GC analysis results of Example 2 are shown in Table 3.

<Example 3>
As shown in Table 1, the photochlorination reaction was carried out in the same manner as in Example 1 except that the molar ratio of monochlorobenzene to EC that coexists with EC was 1.05 times. The GC analysis results of Example 3 are shown in Table 4.

<Example 4>
As shown in Table 1, the photochlorination reaction was carried out in the same manner as in Example 1 except that the molar ratio of monochlorobenzene coexisting with EC to EC was 3.28 times. The GC analysis results of Example 4 are shown in Table 5.

<Example 5>
As shown in Table 1, a predetermined amount of EC was coexisted with orthodichlorobenzene having a molar ratio of 1.18 to the EC. Otherwise, the photochlorination reaction was carried out in the same manner as in Example 1. The GC analysis results of Example 5 are shown in Table 6.

<Comparative Example 1>
As shown in Table 1, as an aromatic chloride , nothing was added to EC, and the photochlorination reaction was carried out in the same manner as in Example 1. Table 7 shows the GC analysis results of the comparative examples.

  About 209.5 g of the reaction solution thus obtained, purified distillation was performed under reduced pressure using a distillation column having a theoretical plate number of 21 under a reflux ratio of 5 to obtain a rectified fraction of 112 to 116 ° C./17 to 20 mmHg. 82.0 g was obtained. The distillation yield was 70.7% based on CEC, the purity of CEC was 98.88%, and the content of difficult-to-separate impurities was 0.51%.

  Regarding the results of Examples 1 to 4 and Comparative Example 1, the relationship between the amount of purified refractory impurities with respect to the degree of chlorination is shown in FIG. 1 using the molar ratio of monochlorobenzene to EC (MCB coexistence ratio) as a parameter. FIG. 2 shows the relationship between the MCB coexistence ratio and the amount of hardly separable impurities produced at a chlorination degree of 0.6 in FIG.

As a difference in the amount of the flame separation impurities for MCB coexistence ratio, as shown in FIGS. 1 and 2, when the reaction is carried out in 0.33 MCB coexistence ratio, as compared with the case of the absence of aromatic chlorides, It was found that the amount of hardly separable impurities produced was 1/3. Moreover, the tendency for the production amount of a hard-to-separate impurity to decrease further decreased by increasing the coexistence ratio of aromatic chloride (to EC molar ratio).

However, if the coexistence ratio of aromatic chloride (to EC molar ratio) is increased, volumetric efficiency is deteriorated and productivity is lowered. It is considered that the aromatic chloride coexistence ratio (to EC molar ratio) is preferably 7.0 times or less under conditions assuming an actual machine.

FIG. 1 is a graph showing the relationship of the amount of hardly separable impurities produced with respect to the degree of chlorination, using the molar ratio of monochlorobenzene to EC (MCB coexistence ratio) as a parameter. FIG. 2 is a graph showing the relationship between the monochlorobenzene to EC molar ratio (MCB coexistence ratio) of the coexisting monochlorobenzene at the chlorination degree of 0.6 in FIG.

Claims (2)

Introducing ethylene carbonate and an aromatic system to a chlorine gas are allowed to coexist and chlorides, under light irradiation, a manufacturing method of chloroethylene carbonate, characterized in that the reaction of ethylene carbonate with chlorine gas. The method for producing chloroethylene carbonate according to claim 1, wherein chlorine gas is introduced into a system in which ethylene carbonate and 0.1 to 7.0-fold moles of aromatic chloride coexist with ethylene carbonate.

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