Method for producing alkylene carbonate

Abstract

Provided is a method for producing alkylene carbonate from alkylene oxide and carbon dioxide, which recovers alkylene carbonate and an alkali halide from a waste liquid while reducing the entrainment of HB. [Solution] The method for producing alkylene carbonate comprises a reaction step of reacting alkylene oxide with carbon dioxide in a reactor in the presence of an alkali halide to obtain alkylene carbonate, a cooling step of cooling a mixture (A) containing the alkylene carbonate and the alkali halide that has undergone the reaction step, and a solid-liquid separation step of separating a solid containing the alkylene carbonate and the alkali halide from a mother liquor, wherein the alkylene carbonate and the alkali halide separated in the solid-liquid separation step are supplied to the reactor.

Description

[Technical field]

[0001] The present invention relates to a method for producing an alkylene carbonate. [Background technology]

[0002] The reaction for producing alkylene carbonate from alkylene oxide and carbon dioxide (hereinafter also referred to as "this reaction") has been extensively studied due to its usefulness, and catalysts have been actively studied to obtain an industrially sufficient reaction rate. There are many reports on the use of solid acid catalysts, alkali metal salt catalysts, homogeneous organometallic catalysts, etc., and catalysts have been significantly improved. However, a relatively large amount of catalyst is required for the catalytic reaction to react carbon dioxide, which is one of the most stable compounds, and the catalyst is deactivated by low molecular weight polymers of alkylene oxide that are by-produced under the reaction conditions. Therefore, there has been a demand for the establishment of a technology for a method of reusing the catalyst in this reaction. To address this issue, for example, a method has been disclosed in which the residual liquid after separating alkylene carbonate from the reaction mixture is returned to the reactor as a catalyst (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-104092 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the process described in Patent Document 1, the residual liquid contains, in addition to alkylene carbonate, high-boiling compounds (hereinafter also referred to as "HB") such as polyglycols and polycarbonates, which have a boiling point higher than that of alkylene carbonate, and these HBs accumulate while circulating in the process together with the catalyst. Therefore, in order to remove them from the process, a part of the residual liquid must be discharged as waste liquid outside the process, resulting in a loss of alkylene carbonate and the alkali halide used as the catalyst.

[0005] An object of the present invention is to provide a method for producing an alkylene carbonate from an alkylene oxide and carbon dioxide, which recovers an alkylene carbonate and an alkali halide from a waste liquid while reducing the entrainment of HB. [Means for solving the problem]

[0006] The present inventors have conducted intensive research to solve the above-mentioned problems, and as a result, have found that by cooling a mixture containing an alkylene carbonate, a catalyst, and HB obtained by the production of alkylene carbonate to precipitate the alkylene carbonate and the catalyst, it is possible to efficiently recover the alkylene carbonate and the catalyst as precipitates while removing HB from the system as a mother liquor, and have arrived at the present invention.

[0007] That is, the present invention includes the following embodiments. <1> 1. A method for producing an alkylene carbonate, comprising the steps of: a reaction step of reacting an alkylene oxide with carbon dioxide in a reactor in the presence of an alkali halide to obtain an alkylene carbonate; a cooling step of cooling the mixture (A) containing the alkylene carbonate and the alkali halide that has been subjected to the reaction step; a solid-liquid separation step of separating a solid containing an alkylene carbonate and an alkali halide from a mother liquor; having Supplying the alkylene carbonate and the alkali halide separated in the solid-liquid separation step to the reactor. A method for producing alkylene carbonate. <2> The method further includes a separation step of obtaining the mixture (A) from the solution that has been subjected to the reaction step. <1> A method for producing an alkylene carbonate according to claim 1. <3> In the separation step, the mixture (A) is obtained by separating the alkylene carbonate, the unreacted alkylene oxide, and the carbon dioxide from the solution that has been subjected to the reaction step. <2> A method for producing an alkylene carbonate according to claim 1. <4> A part of the mother liquor separated in the solid-liquid separation step is returned to the cooling step. <1> ~ <3> 2. A method for producing an alkylene carbonate according to claim 1 . <5> In the solid-liquid separation step, the solid is separated by centrifugation. <1> ~ <4> 2. A method for producing an alkylene carbonate according to claim 1 . <6> The method further includes a heating step of heating the solid containing the alkylene carbonate and the alkali halide. <1> ~ <5> 2. A method for producing an alkylene carbonate according to claim 1 . <7> The alkylene oxide is ethylene oxide, and the alkylene carbonate is ethylene carbonate. <1> ~ <6> 2. A method for producing an alkylene carbonate according to claim 1 . <8> The alkali halide is an alkali metal iodide. <1> ~ <7> 2. A method for producing an alkylene carbonate according to claim 1 . <9> The temperature to which the mixture (A) is cooled in the cooling step is −30 to 36° C. <1> ~ <8> 2. A method for producing an alkylene carbonate according to claim 1 . <10> The slurry concentration of the mixture (A) after the cooling step is 10 to 40 wt%. <1> ~ <9> 2. A method for producing an alkylene carbonate according to claim 1 . Effect of the Invention

[0008] According to the present invention, there can be provided a method for producing an alkylene carbonate from an alkylene oxide and carbon dioxide, which recovers an alkylene carbonate and an alkali halide from a waste liquid while reducing entrainment of HB. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an outline of the process of this embodiment. [Diagram 2] FIG. 2 shows a schematic configuration of an apparatus used in the method for producing an alkylene carbonate. [Diagram 3] FIG. 3 shows a schematic configuration of a crystallizer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the present invention. In addition, positional relationships such as up, down, left, and right in the drawings are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0011] The method for producing an alkylene carbonate according to this embodiment includes the steps of: a reaction step of reacting an alkylene oxide with carbon dioxide in a reactor in the presence of an alkali halide to obtain an alkylene carbonate; a cooling step of cooling the mixture (A) containing the alkylene carbonate and the alkali halide that has been subjected to the reaction step; a solid-liquid separation step of separating a solid containing an alkylene carbonate and an alkali halide from a mother liquor; having The alkylene carbonate and the alkali halide separated in the solid-liquid separation step are supplied to the reactor. According to the above embodiment, in a method for producing an alkylene carbonate from an alkylene oxide and carbon dioxide, it is possible to provide a method for producing an alkylene carbonate, in which an alkylene carbonate and an alkali halide are recovered from a waste liquid while reducing entrainment of HB.

[0012] Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, vinylethylene oxide, cyclohexene oxide, and styrene oxide. Of these, ethylene oxide is preferred.

[0013] Alkali halides are used as catalysts. Examples of alkali halides include alkali metal halides such as sodium iodide (NaI), potassium iodide (KI), sodium bromide (NaBr), and potassium bromide (KBr), and alkaline earth metal halides such as calcium iodide (CaI2) and calcium bromide. Among these, alkali metal halides are preferred.

[0014] Examples of alkylene carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, vinylethylene carbonate, cyclohexene carbonate, and styrene carbonate. Of these, ethylene carbonate is preferred.

[0015] 1 is a block diagram showing an outline of the process of this embodiment. This embodiment includes a reaction step, a cooling step, and a solid-liquid separation step. This embodiment may further include a separation step.

[0016] In the reaction step, alkylene oxide reacts with carbon dioxide to produce alkylene carbonate. As described later, the reaction step may have three steps, a first reaction step, a second reaction step, and a third reaction step. The mixture obtained by the reaction step may contain HB.

[0017] This embodiment may further include a separation step of obtaining a mixture (A) by separating the alkylene carbonate, the unreacted alkylene oxide, and the carbon dioxide. The separation step may include a step of separating and removing the dissolved carbon dioxide and the alkylene oxide, and a separation and recovery step of separating and recovering the alkylene carbonate. The residue after the separation and recovery step may be used as the mixture (A) in the cooling step described below.

[0018] In the cooling step, the mixture (A) is cooled to precipitate the alkylene carbonate and the alkali halide. The mixture (A) preferably contains HB. The high boiling point compound (HB) means an organic compound having a boiling point higher than that of the alkylene carbonate. In the cooling step, it is preferable to cool the mixture using a crystallizer or the like.

[0019] The temperature to which mixture (A) is cooled in the cooling step is preferably from -30 to 36°C, more preferably from -25 to 20°C, even more preferably from -20 to 10°C, and still more preferably from -15 to 0°C, from the viewpoint of ensuring a sufficient amount of alkali halide precipitated and from the viewpoint of operability.

[0020] The slurry concentration of the mixture (A) after the cooling step is preferably 10 to 40 wt %, more preferably 15 to 30 wt %. The slurry concentration means the concentration of the precipitated solid content in the mixture (A).

[0021] In the solid-liquid separation step, a solid containing an alkylene carbonate and an alkali halide is separated from a mother liquor. From the viewpoint of increasing the efficiency of the treatment, the solid may be separated by centrifugation.

[0022] In this embodiment, the alkylene carbonate and the alkali halide separated in the solid-liquid separation step are supplied to the reactor in the reaction step, but the alkylene carbonate and the alkali halide may be supplied to the reactor in the form of a solution. In this case, it is preferable to have a heating step of heating the solid containing the alkylene carbonate and the alkali halide.

[0023] The outline of the apparatus used in the alkylene carbonate production method according to the present embodiment will be described. As shown in Fig. 2, the apparatus used in the alkylene carbonate production method according to the present embodiment may have a first reactor A, a first heat remover B, a second reactor C, a second heat remover D, a third reactor E, a flash tank F, a separation and recovery device G, and a catalyst preparation tank H. Hereinafter, the alkylene carbonate production method according to the present embodiment using the apparatus will be described.

[0024] <First reaction step> In the first reaction step, an alkylene oxide is reacted with carbon dioxide in a first reactor A to obtain a reaction mixture containing an alkylene carbonate.

[0025] As the first reactor A, a reactor for a commonly used reaction system such as a complete mixing reactor, a plug flow reactor, etc. may be used. Among these, it is preferable to use a complete mixing reactor as the first reactor A.

[0026] The reactor for complete mixing is preferably a reactor that dissolves carbon dioxide in the reaction mixture, and examples of the reactor include a shower nozzle reactor, an ejector reactor, and a bubble column reactor. It is also preferable to use a complete mixing tank reactor equipped with a Venturi stirrer as the reactor for complete mixing.

[0027] In the first reactor A, alkylene oxide and carbon dioxide are supplied from the top of the first reactor A. The alkali halide used as a catalyst is adjusted to a predetermined concentration in advance in a catalyst preparation tank H using alkylene carbonate as a solvent, and then quantitatively supplied from a replenishment catalyst supply line 9 to a catalyst supply line 7 and then supplied from the top of the first reactor A.

[0028] In the first reaction step, an alkali halide is used as a catalyst, for example, an alkali halide such as an alkali metal or alkaline earth metal halide, or a mixture of these with a small amount of alcohol or water added thereto.

[0029] The amount of the catalyst used is preferably 0.1 to 3 wt %, and more preferably 0.1 to 2 wt %, based on the total amount of the reaction system.

[0030] From the viewpoint of suppressing the generation of HB that causes stains inside the apparatus, the reaction temperature in the first reaction step is 150 to 200° C. The reaction temperature in the first reaction step is preferably 155 to 195° C., and more preferably 160 to 190° C.

[0031] The reaction pressure in the first reaction step is preferably from 2 to 15 MPaG, more preferably from 4 to 12 MPaG, and further preferably from 6 to 10 MPaG.

[0032] The reaction time in the first reaction step varies depending on the composition ratio of the raw materials, alkylene oxide and carbon dioxide, the type and concentration of the catalyst used, the reaction temperature, etc. The average residence time calculated from the amount of the retained liquid in the complete mixing reactor and the total amount of the supplied liquid is preferably 0.5 to 10 hours, more preferably 1 to 5 hours.

[0033] The molar ratio of carbon dioxide to alkylene oxide in the first reaction step is preferably 1 to 5, and more preferably 1 to 2. It is preferable to adjust the amount of carbon dioxide supplied so that the pressure in the first reactor A is constant.

[0034] This reaction is a highly exothermic reaction, and it is important to remove the heat of reaction. A part of the reaction mixture is withdrawn from the first reactor A through the first reaction mixture discharge line 1, and the reaction mixture is cooled through the first heat remover B and returned to the first reactor A to remove heat. At least a part of the reaction mixture discharged to the first reaction mixture discharge line 1 is sent to the second reactor C.

[0035] When a complete mixing type reactor is used, a method of circulating the reaction mixture at a large flow rate by pumping is preferred so that a larger amount of carbon dioxide is dissolved in the reaction mixture. Usually, the number of circulations per unit time is 10 to 70 times / hour, and preferably 20 to 50 times / hour. When removing the reaction heat by providing a first heat remover B in the middle of the piping for pumping the reaction mixture, it is preferable to circulate at a large flow rate because the cooling capacity of the heat exchanger is increased.

[0036] <Second reaction step> The method for producing an alkylene carbonate according to this embodiment may include a second reaction step in which at least a portion of the reaction mixture that has undergone the first reaction step is reacted with an alkylene oxide and carbon dioxide in a second reactor C to obtain a reaction mixture containing an alkylene carbonate.

[0037] 2, the reaction mixture in the second reactor C is discharged from the second reaction mixture discharge line 2, and at least a part of it is sent to the second heat remover D. At least a part of the reaction mixture discharged to the second reaction mixture discharge line 2 is sent to the third reactor E.

[0038] The second reactor C is the same as the example of the first reactor A described above. The reaction temperature in the second reaction step is 150 to 200° C. from the viewpoint of suppressing the generation of HB, which causes stains inside the apparatus. The reaction temperature in the second reaction step is preferably 155 to 195° C., and more preferably 160 to 190° C.

[0039] The reaction pressure in the second reaction step is preferably 2 to 12 MPaG, more preferably 4 to 8 MPaG, and further preferably 4.5 to 6.5 MPaG.

[0040] The reaction time in the second reaction step varies depending on the composition ratio of the raw materials, alkylene oxide and carbon dioxide, the type and concentration of the catalyst used, the reaction temperature, etc. The average residence time calculated from the amount of the retained liquid in the complete mixing reactor and the total amount of the supplied liquid is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours.

[0041] In the second reaction step, the molar ratio of carbon dioxide to alkylene oxide at the inlet of the second reactor is preferably 1 to 5, more preferably 1 to 4. In the second reactor C, carbon dioxide may not be newly supplied, and the reaction mixture from the first reactor A may be used as it is.

[0042] This reaction is a highly exothermic reaction, and it is important to remove the heat of reaction. A part of the reaction mixture is withdrawn from the second reactor C through the second reaction mixture discharge line 2, and the reaction mixture is cooled through the second heat remover D and returned to the second reactor C again to remove heat. At least a part of the reaction mixture discharged to the second reaction mixture discharge line 2 is sent to the third reactor E.

[0043] When a complete mixing type reactor is used, a method of circulating the reaction mixture at a large flow rate by pumping is preferred so that a larger amount of carbon dioxide is dissolved in the reaction mixture. Usually, the number of circulations per unit time is 5 to 50 times / hour, and preferably 10 to 30 times / hour. When removing the reaction heat by providing a second heat remover D in the middle of the piping for pumping the reaction mixture, it is preferable to circulate at a large flow rate because the cooling capacity of the heat exchanger is increased.

[0044] <Third reaction step> The method for producing an alkylene carbonate according to this embodiment may include a third reaction step in which at least a portion of the reaction mixture that has undergone the second reaction step is reacted with an alkylene oxide and carbon dioxide in a third reactor E to obtain a reaction mixture containing an alkylene carbonate. The third reactor E is preferably a liquid-filled reactor. The third reactor E is provided to react the unreacted alkylene oxide with carbon dioxide. In addition, the third reactor E preferably does not have an external circulation path.

[0045] <Separation and recovery process> The method for producing an alkylene carbonate according to this embodiment may include a separation and recovery step in which an alkylene carbonate is separated and recovered from a reaction mixture that has been subjected to a first reaction step. The reaction mixture used in the separation and recovery step may be one that has been subjected to a second reaction step or a third reaction step. The reaction mixture may include a flash tank F that separates and removes dissolved carbon dioxide and alkylene oxide before the separation and recovery step.

[0046] Examples of the separation and recovery device G used for separation and recovery include a rectification tower, a distillation tower, and a thin film evaporator. The fraction evaporated in the rectification tower, distillation tower, and thin film evaporator is recovered as a product, and the bottom liquid and evaporation residue are sent to cooling crystallization. Among these, a thin film evaporator is preferred from the viewpoint of suppressing decomposition of alkylene carbonate and simplicity of the device. In this case, if the alkylene carbonate is not evaporated in the thin film evaporator, the amount that can be recovered as a product will be reduced, but conversely, if it is evaporated too much, HB will contaminate the alkylene carbonate, and the catalyst concentration will exceed the solubility and precipitate, which may cause problems such as damaging pumps, which is not preferable. Although it depends on the catalyst used, it is preferable to set the distillation conditions so that some alkylene carbonate is left at the bottom of the tower so that the catalyst concentration in the distillation residue is about 2 to 10 wt%, since it is possible to maintain a state in which the catalyst is uniformly dissolved in the alkylene carbonate after recovering the alkylene carbonate.

[0047] After the separation and recovery process, the mixture (A) contains alkylene carbonate, catalyst, and HB. In order to prevent the accumulation of HB, which causes fouling in the apparatus, it is preferable to feed the mixture (A) from the waste liquid discharge line 8 to the cooling process in the range of 0.3 to 30 wt% of the flow rate of the mixture (A), and the remainder is recycled to the first reactor A. In this case, in order to prevent the situation in which HB is likely to accumulate in the reaction system, it is preferable to set the amount introduced into the cooling process to 0.3 wt% or more of the total amount of the mixture (A), and from the viewpoint of preventing a large amount of distillation residue from being discharged outside the process and the treatment equipment from becoming excessive, it is preferable to set the amount introduced into the cooling process to 30 wt% or less of the total amount of the mixture (A). In addition, a new catalyst may be supplied from the supplementary catalyst supply line 9, or a catalyst that has been subjected to the cooling process and solid-liquid separation process described later may be supplied.

[0048] The alkylene carbonate production method according to the present embodiment is preferably carried out on an industrial scale. In this specification, the industrial scale means a scale in which alkylene carbonate is produced at a rate of 1 ton / hour or more. The amount of alkylene carbonate produced in the alkylene carbonate production method according to the present embodiment is preferably 1 ton / hour or more, more preferably 2 ton / hour or more, even more preferably 3 ton / hour or more, and even more preferably 4 to 20 ton / hour.

[0049] Next, an overview of the apparatus used in the cooling step and solid-liquid separation step according to this embodiment will be described. Fig. 3 shows a schematic configuration of a crystallization apparatus. The crystallization apparatus according to this embodiment has a crystallization tank I and a solid-liquid separator J. The crystallization tank I is equipped with a cooling jacket, an agitator blade, and an external refrigerant circulation mechanism.

[0050] <Crystallizer> The mixed solution (A) containing alkylene carbonate, catalyst, and HB is supplied to the crystallization tank I through the waste liquid discharge line 8. The mixed solution (A) introduced into the crystallization tank I is usually kept at -30 to 36 ° C, preferably -25 to 20 ° C, more preferably -20 to 10 ° C, and even more preferably -15 to 0 ° C by external circulation of the refrigerant in the cooling jacket part. In the mixed solution (A) kept at this temperature, a solid (hereinafter also referred to as "crystals") containing alkylene carbonate and catalyst is precipitated due to the freezing point difference and solubility difference, and exists in the tank as a slurry solution, and the slurry solution is sent to the solid-liquid separator J from the discharge pipe 10 at the bottom of the crystallization tank. At this time, from the viewpoint of ensuring a sufficient amount of catalyst precipitation, it is preferable to set the temperature of the crystallization tank I to 36 ° C or less. On the other hand, it is preferable to set the temperature to -30 ° C or more from the viewpoint of suppressing the increase in viscosity of HB due to low temperature, improving the stirrability and transportability of the slurry liquid in the crystallization tank, and maintaining good operability.

[0051] The solid-liquid separator J may be a solid-liquid separator of a generally used separation method such as centrifugal filtration, pressure filtration, or vacuum filtration. The crystals of the alkylene carbonate and catalyst separated in the solid-liquid separator J are sent to the catalyst preparation tank H through a pipe 12, but they may be heated to be liquid before being sent to the catalyst preparation tank H. The crystals contain both the alkylene carbonate and the catalyst inseparably, but since the alkylene carbonate acts as a solvent for the catalyst and the catalyst acts as a catalyst in the above-mentioned reaction step, both are useful even if they are sent to the reaction step in an inseparable state. The mother liquor separated in the solid-liquid separator J is discharged outside the process through a pipe 13. In addition, in order to adjust the slurry concentration in the crystallization tank I, a part of the recovered mother liquor is returned to the crystallization tank I through a pipe 11. The slurry concentration in the crystallization tank I is preferably maintained at 10 to 40 wt%, more preferably 15 to 30 wt%. In this case, it is preferable to set the slurry concentration to 40 wt% or less, since this prevents the crystal ratio in the slurry solution from becoming too high, which would deteriorate the stirrability and transportability of the slurry liquid in the crystallization tank. Also, it is preferable to set the concentration to 10 wt% or more, since it is not necessary to increase the amount of mother liquor returned to the crystallization tank I through the pipe 11 in order to reduce the crystal ratio in the slurry solution, i.e., the amount of mother liquor circulated, and therefore it is not necessary to oversize the crystallization tank or pump. EXAMPLES

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0053] [Example 1] The present embodiment will be specifically described with reference to FIG. 2 and FIG. 2 shows a schematic configuration of an apparatus used in the EC production method. The EC production apparatus according to this embodiment includes a first reactor A, a first heat remover B, a second reactor C, a second heat remover D, a third reactor E, a flash tank F, a separation and recovery device G, and a catalyst preparation tank H. EO was cooled to about 5℃ and supplied to the first reactor A. The supply rate was 2495kg / h. CO2 was gasified by using a hot water bath type CO2 evaporator to adjust the temperature to about 90℃ and the pressure to about 9.8MPaG, and supplied to the first reactor A. The supply rate was 3020kg / h. After EC was purified in the separation and recovery device G, the mixture (A) recovered was fed from the catalyst feed line 7, and the replenishment catalyst solution was fed from the replenishment catalyst feed line 9 to prepare a catalyst solution at a ratio of about 9:1: mixture (A): replenishment catalyst solution. The catalyst solution was fed so that the KI concentration in the first reactor A was 0.23-0.26wt%. In the catalyst solution, the supply rate of mixture (A) was 290kg / h and the supply rate of replenishment catalyst was 32kg / h. The replenishment catalyst was prepared in the catalyst preparation tank H to be 5wt% in the EC solution. The reaction temperature of the reactor was 180℃.

[0054] The mixture extracted from the third reactor E was supplied to the flash tank F through the pipe 3, and unreacted EO, CO2, and a small amount of EC were discharged from the process as gas through the pipe 4. The operating condition of the flash tank F was 760 Torr. Furthermore, a mixture mainly containing EC was extracted from the bottom of the flash tank F through the pipe 5 and introduced into the separation and recovery device G. EC purified by evaporation was extracted at 4910 kg / h through the pipe 6, and the mixture (A) containing the catalyst and HB was extracted through the catalyst supply line 7. The composition of the mixture (A) was EC: 80 wt%, KI: 5 wt%, and HB: 15 wt%. A part of this was supplied to the crystallization process through the waste liquid discharge line 8, and the supply amount was 32 kg / h.

[0055] 3 shows a schematic configuration of a crystallizer. The crystallizer according to this embodiment includes a crystallizer I and a solid-liquid separator J. The crystallizer I includes a cooling jacket, an agitator blade, and an external refrigerant circulation mechanism. A mixture (A) containing EC, KI, and HB was supplied to crystallization tank I through waste liquid discharge line 8. The supply rate of mixture (A) was 32 kg / h. The mother liquor temperature in crystallization tank I was set at -10°C by external circulation of a refrigerant. The crystals precipitated in crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to solid-liquid separator J through discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 100 kg / h, and the slurry concentration was 25 wt%. The crystals separated in solid-liquid separator J had a composition of EC: 96.5 wt%, KI: 2.6 wt%, and HB: 1.0 wt%, and were supplied to catalyst preparation tank H through pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.8 wt%, KI: 13.6 wt%, and HB: 64.6 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 68 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0056] [Example 2] The apparatus shown in Figures 2 and 3 was used as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1. In the crystallization apparatus shown in FIG. 3, a mixture (A) containing EC, KI, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature in the crystallization tank I was set to -10°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 62.5 kg / h, and the slurry concentration was 40 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 96.5 wt%, KI: 2.6 wt%, and HB: 1.0 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.8 wt%, KI: 13.6 wt%, and HB: 64.6 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 30.5 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0057] [Example 3] The apparatus shown in Figures 2 and 3 was used as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1. In the crystallization apparatus shown in FIG. 3, a mixture (A) containing EC, KI, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature in the crystallization tank I was set to -10°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 250 kg / h, and the slurry concentration was 10 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 96.5 wt%, KI: 2.6 wt%, and HB: 1.0 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.8 wt%, KI: 13.6 wt%, and HB: 64.6 wt%, and part of the mother liquor was circulated into crystallization tank I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 218 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0058] [Example 4] The apparatus shown in Figures 2 and 3 was used as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, KI, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to 15°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the pipe 10. The supply rate of the solid-liquid mixed phase liquid was 110 kg / h, and the slurry concentration was 25 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 97.7 wt%, KI: 1.7 wt%, and HB: 0.5 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 22 kg / h. The mother liquor had a composition of EC: 41.0 wt%, KI: 12.2 wt%, and HB: 46.8 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 88 kg / h and 10 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0059] [Example 5] The apparatus shown in Figures 2 and 3 was used as in Example 1. The operating conditions of Figure 2 were the same as in Example 1. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, KI, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -20°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 130 kg / h, and the slurry concentration was 25 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 95.1 wt%, KI: 3.1 wt%, and HB: 1.8 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 26 kg / h. The mother liquor had a composition of EC: 13.0 wt%, KI: 13.6 wt%, and HB: 73.4 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 104 kg / h and 6 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0060] [Example 6] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1, except that NaBr was used as the catalyst. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, NaBr, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -10°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 100 kg / h, and the slurry concentration was 25 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 96.8 wt%, NaBr: 2.3 wt%, and HB: 1.0 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 68 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0061] [Example 7] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1, except that NaBr was used as the catalyst. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, NaBr, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -10°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 62.5 kg / h, and the slurry concentration was 40 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 96.8 wt%, NaBr: 2.3 wt%, and HB: 1.0 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 30.5 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0062] [Example 8] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1, except that NaBr was used as the catalyst. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, NaBr, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -10°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 250 kg / h, and the slurry concentration was 10 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 96.8 wt%, NaBr: 2.3 wt%, and HB: 1.0 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 25 kg / h. The mother liquor had a composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 218 kg / h and 7 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0063] [Example 9] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1, except that NaBr was used as the catalyst. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, NaBr, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to 15°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 86 kg / h, and the slurry concentration was 25 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 99.4 wt%, NaBr: 0 wt%, and HB: 0.6 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 22 kg / h. The mother liquor had a composition of EC: 39.5 wt%, NaBr: 15.4 wt%, and HB: 45.1 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 54 kg / h and 10 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0064] [Example 10] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions of the apparatus in Figure 2 were the same as in Example 1, except that NaBr was used as the catalyst. In the crystallization apparatus of FIG. 3, a mixture (A) containing EC, NaBr, and HB was supplied to the crystallization tank I through the waste liquid discharge line 8. The supply rate of the mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -20°C by external circulation of a refrigerant. The crystals precipitated in the crystallization tank I and the solid-liquid mixed phase liquid of the mother liquor were supplied to the solid-liquid separator J through the discharge pipe 10. The supply rate of the solid-liquid mixed phase liquid was 104 kg / h, and the slurry concentration was 25 wt%. The crystals separated in the solid-liquid separator J had a composition of EC: 95.4 wt%, NaBr: 2.8 wt%, and HB: 1.8 wt%, and were supplied to the catalyst preparation tank H through the pipe 12. The supply rate of the crystals was 26 kg / h. The mother liquor had a composition of EC: 12.9 wt%, NaBr: 14.7 wt%, and HB: 72.4 wt%, and part of the mother liquor was circulated into crystallizer I through pipe 11, and part was discharged outside the process through pipe 13. The mother liquor supply rates were 72 kg / h and 6 kg / h, respectively. The process liquid in pipe 13 was liquid at room temperature of 20°C.

[0065] [Comparative Example 1] The process is the same as in the Example, except that the crystallizer shown in FIG. 3 is not used. The mixture (A) containing the catalyst and HB was extracted through the catalyst supply line 7. The composition of the mixture (A) was EC: 80 wt%, catalyst: 5 wt%, and HB: 15 wt%. A part of this was discharged outside the process through the waste liquid discharge line 8. The discharge rate of the mixture (A) was 32 kg / h. The process liquid in the waste liquid discharge line 8 was solid at room temperature of 20°C.

[0066] [Table 1] [Explanation of symbols]

[0067] A: First reactor, B: First heat remover, C: Second reactor, D: Second heat remover, E: Third reactor, F: Flash tank, G: Separation and recovery device, H: Catalyst preparation tank, I: Crystallization tank, J: Solid-liquid separator

Claims

1. 1. A process for producing an alkylene carbonate, comprising the steps of: a reaction step of reacting an alkylene oxide with carbon dioxide in a reactor in the presence of an alkali halide to obtain an alkylene carbonate; a cooling step of cooling the mixture (A) containing the alkylene carbonate and the alkali halide that has been subjected to the reaction step; a solid-liquid separation step of separating a solid containing an alkylene carbonate and an alkali halide from a mother liquor; having Supplying the alkylene carbonate and the alkali halide separated in the solid-liquid separation step to the reactor. A method for producing alkylene carbonate.

2. The method for producing an alkylene carbonate according to claim 1, further comprising a separation step of obtaining the mixture (A) from the solution that has been subjected to the reaction step.

3. The method for producing an alkylene carbonate according to claim 1 or 2, wherein a part of the mother liquor separated in the solid-liquid separation step is returned to the cooling step.

4. 3. The method for producing an alkylene carbonate according to claim 2, wherein in the separation step, the mixture (A) is obtained by separating the alkylene carbonate, unreacted alkylene oxide and carbon dioxide from the solution that has been subjected to the reaction step.

5. The method for producing an alkylene carbonate according to claim 1 or 2, wherein in the solid-liquid separation step, the solid is separated by centrifugation.

6. The method for producing an alkylene carbonate according to claim 1 or 2, further comprising a heating step of heating the solid containing the alkylene carbonate and the alkali halide.

7. 3. The method for producing an alkylene carbonate according to claim 1 or 2, wherein the alkylene oxide is ethylene oxide, and the alkylene carbonate is ethylene carbonate.

8. The method for producing an alkylene carbonate according to claim 1 or 2, wherein the alkali halide is an alkali metal iodide.

9. The method for producing an alkylene carbonate according to claim 1 or 2, wherein the temperature at which the mixture (A) is cooled in the cooling step is −30 to 36° C.

10. The method for producing an alkylene carbonate according to claim 1 or 2, wherein the slurry concentration of the mixture (A) after the cooling step is 10 to 40 wt %.

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