Method of producing alkylene carbonate

Abstract

Disclosed is a method for producing an alkylene carbonate, which includes: a reaction step for reacting an alkylene oxide with carbon dioxide in a reactor in the presence of an alkali halide so as to obtain an alkylene carbonate; a cooling step for cooling a mixture (A) that contains the alkylene carbonate and the alkali halide that have been subjected to the reaction step; and a solid-liquid separation step for separating a solid that contains the alkylene carbonate and the alkali halide from the mother liquor. The alkylene carbonate and the alkali halide separated in the solid-liquid separation step are supplied to the reactor.

Description

Process for producing alkylene carbonate

[0001] The present invention relates to a process for producing alkylene carbonate.

[0002] The reaction for producing alkylene carbonate from alkylene oxide and carbon dioxide (hereinafter also referred to as "the present reaction") has been studied extensively because of its usefulness, and the catalysts have also been actively studied in order to obtain an industrially sufficient reaction rate. There have been many reports using solid acid catalysts, alkali metal salt catalysts, homogeneous organometallic catalysts, etc. Although the catalysts have been considerably improved, 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 by-produced under the reaction conditions. Therefore, the establishment of a technique for the reuse method of the catalyst in the present reaction has been demanded. To solve this problem, 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 and used as a catalyst (Patent Document 1).

[0003] JP-A-2006-104092

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

[0005] An object of the present invention is to provide a process for producing alkylene carbonate, which recovers alkylene carbonate and alkali halide from waste liquid while reducing the entrainment of HB.

[0006] As a result of diligent research to solve the aforementioned problems, the inventors of the present invention have discovered that by cooling a mixture containing alkylene carbonate obtained by alkylene carbonate production, a catalyst, and HB, the alkylene carbonate and catalyst can be efficiently recovered as precipitates while HB is removed from the system as the mother liquor, leading to the present invention.

[0007] In other words, the present invention includes the following embodiments: <1> A method for producing alkylene carbonate, comprising: a reaction step of reacting alkylene oxide and carbon dioxide in a reactor in the presence of an alkali halogen to obtain alkylene carbonate; a cooling step of cooling a mixture (A) containing the alkylene carbonate and alkali halogen obtained through the reaction step; and a solid-liquid separation step of separating a solid containing alkylene carbonate and alkali halogen from a mother liquor, wherein the alkylene carbonate and alkali halogen separated in the solid-liquid separation step are supplied to the reactor. <2> The method for producing alkylene carbonate according to <1>, further comprising a separation step of obtaining the mixture (A) from the solution obtained through the reaction step. <3> The method for producing alkylene carbonate according to <2>, wherein in the separation step, the mixture (A) is obtained by separating alkylene carbonate, unreacted alkylene oxide and carbon dioxide from the solution obtained through the reaction step. <4> A method for producing an alkylene carbonate according to any one of <1> to <3>, wherein a portion of the mother liquor separated in the solid-liquid separation step is returned to the cooling step. <5> A method for producing an alkylene carbonate according to any one of <1> to <4>, wherein in the solid-liquid separation step, the solid is separated by centrifugal separation. <6> A method for producing an alkylene carbonate according to any one of <1> to <5>, further comprising a heating step of heating a solid containing the alkylene carbonate and an alkali halogen. <7> A method for producing an alkylene carbonate according to any one of <1> to <6>, wherein the alkylene oxide is ethylene oxide and the alkylene carbonate is ethylene carbonate. <8> A method for producing an alkylene carbonate according to any one of <1> to <7>, wherein the alkali halogen is an alkali metal iodide. <9> A method for producing alkylene carbonate according to any one of <1> to <8>, wherein the temperature at which the mixture (A) is cooled in the cooling step is -30 to 36°C. <10> A method for producing alkylene carbonate according to any one of <1> to <9>, wherein the slurry concentration of the mixture (A) after the cooling step is 10 to 40 wt%.

[0008] According to the present invention, a method for producing alkylene carbonate from alkylene oxide and carbon dioxide is provided, which recovers alkylene carbonate and alkali halogens from waste liquid while reducing the entrainment of HB.

[0009] Figure 1 is a block diagram showing the schematic process of this embodiment. Figure 2 shows the schematic configuration of the apparatus used in the method for producing alkylene carbonate. Figure 3 shows the schematic configuration of the crystallization apparatus.

[0010] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to those shown.

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

[0012] Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, vinylethylene oxide, cyclohexene oxide, and styrene oxide. Among 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), potassium bromide (KBr), and calcium iodide (CaI). ２ ), calcium bromide (CaBr ２ Examples include alkaline earth metal halides such as ). Among these, alkali metal halides are preferred, and alkali metal iodides are more preferred.

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

[0015] Figure 1 is a block diagram illustrating the schematic 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 stages: 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 to obtain a mixture (A) by separating alkylene carbonate, unreacted alkylene oxide, and carbon dioxide. The separation step may include a step of separating and removing dissolved carbon dioxide and alkylene oxide, and a separation and recovery step of separating and recovering alkylene carbonate. The residue after the separation and recovery step may be used as mixture (A) in the cooling step described later.

[0018] In the cooling step, the mixture (A) is cooled to precipitate alkylene carbonate and alkali halide. The mixture (A) preferably contains HB. High-boiling-point compound (HB) refers to an organic compound with a higher boiling point than the alkylene carbonate. In the cooling step, it is preferable to use a crystallization apparatus or the like for cooling.

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

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

[0021] In the solid-liquid separation step, the solid containing alkylene carbonate and alkali halogen is separated from the mother liquor. However, from the viewpoint of improving processing efficiency, the solid may be separated by centrifugation.

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

[0023] The general outline of the apparatus used in the alkylene carbonate production method according to this embodiment will be described below. As shown in Figure 2, the apparatus used in the alkylene carbonate production method according to this embodiment may include 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 mixing tank H. The method for producing alkylene carbonate according to this embodiment using this apparatus will be described below.

[0024] <First reaction step> In the first reaction step, a reaction mixture containing alkylene carbonate is obtained by reacting alkylene oxide with carbon dioxide in reactor A.

[0025] As the first reactor A, a reactor of a commonly used reaction type, such as a fully mixed reactor or a plug flow reactor, may be used. Among these, it is preferable to use a fully mixed reactor as the first reactor A.

[0026] For complete mixing, it is preferable to use a reactor that dissolves carbon dioxide in the reaction mixture, such as 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 a complete mixing reactor.

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

[0028] In the first reaction step, an alkali halide is used as a catalyst. Examples of catalysts include alkali halides of alkali metals or alkaline earth metals, as well as those to which small amounts of alcohols or water are added.

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

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

[0031] The reaction pressure in the first reaction step is preferably 2 to 15 MPaG, more preferably 4 to 12 MPaG, and even more preferably 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, which can be determined from the amount of liquid retained in the complete mixing reactor and the total amount of feed liquid, is preferably 0.5 to 10 hours, and 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 and supply the amount of carbon dioxide so that the pressure in the first reactor A remains constant.

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

[0035] When using a fully mixed reactor, it is preferable to circulate a large flow rate of the reaction mixture with a pump so that a larger amount of carbon dioxide is dissolved in the reaction mixture. Typically, the number of circulation cycles per unit time is 10 to 70 times / hour, preferably 20 to 50 times / hour. When a first heat remover B is installed in the piping through which the reaction mixture is circulated by the pump to remove reaction heat, it is preferable to circulate a large flow rate because this increases the cooling capacity of the heat exchanger.

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

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

[0038] As for the second reactor C, it is the same as the examples in the above-described first reactor A. From the viewpoint of suppressing the generation of HB which causes fouling in the apparatus, the reaction temperature in the second reaction step is 150 to 200 °C. 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 even more preferably 4.5 to 6.5 MPaG.

[0040] The reaction time in the second reaction step varies depending on the composition ratio of alkylene oxide and carbon dioxide as raw materials, the type and concentration of the catalyst used, the reaction temperature, etc. The average residence time determined from the residence liquid volume and the total supply liquid volume of the completely mixed reactor is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours.

[0041] The molar ratio of carbon dioxide to alkylene oxide at the inlet of the second reactor in the second reaction step is preferably 1 to 5, and more preferably 1 to 4. It is also possible to directly use the reaction mixture from the first reactor A without newly supplying carbon dioxide to the second reactor C.

[0042] This reaction is a significant exothermic reaction, and the removal of reaction heat is important. A part of the reaction mixture is withdrawn from the second reactor C through the second reaction mixture derivation line 2, and the reaction mixture cooled through the second heat remover D is returned to the second reactor C again for heat removal. Note that at least a part of the reaction mixture derived to the second reaction mixture derivation line 2 is sent to the third reactor E.

[0043] When using a completely mixed type reactor, a method of circulating a large flow rate of the reaction mixture with a pump so that a larger amount of carbon dioxide dissolves in the reaction mixture is preferred. Usually, the number of circulation times per unit time is 5 to 50 times / hour, and preferably 10 to 30 times / hour. When the second heat remover D is provided in the middle of the pipe for pumping and circulating the reaction mixture to remove reaction heat, performing a large flow rate circulation is preferred because the cooling capacity of the heat exchanger increases.

[0044] <Third Reaction Step> The method for producing an alkylene carbonate according to the present embodiment may have a third reaction step of obtaining a reaction mixture containing an alkylene carbonate by reacting at least a part of the reaction mixture obtained through the second reaction step with an alkylene oxide and carbon dioxide in a third reactor E. The third reactor E is preferably a full-liquid reactor. In the third reactor E, it is provided for reacting unreacted alkylene oxide and carbon dioxide. Further, the third reactor E preferably does not have an external circulation path.

[0045] <Separation and Recovery Step> The method for producing an alkylene carbonate according to the present embodiment may have a separation and recovery step of separating and recovering an alkylene carbonate from the reaction mixture obtained through the first reaction step. Note that the reaction mixture used in the separation and recovery step may have further passed through the second reaction step or the third reaction step. Note that the reaction mixture may have a flash tank F for separating and removing 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 column, a distillation column, a thin-film evaporator, etc. The fractions evaporated in the rectification column, the distillation column, and the thin-film evaporator are recovered as products, and the bottom liquid and the evaporation residue are sent to cooling crystallization. Among these, a thin-film evaporator is preferable from the viewpoints of suppressing the decomposition of the alkylene carbonate and the simplicity of the device. At this time, if the alkylene carbonate is not evaporated in the thin-film evaporator, the amount that can be recovered as a product will decrease. 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 the pumps, so it is not preferable. Depending on the catalyst used, it is preferable to set the distillation conditions so that the alkylene carbonate remains slightly at the bottom of the column so that the catalyst concentration in the distillation residue becomes about 2 to 10 wt%, because the catalyst can be maintained in a state of being 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. However, to prevent the accumulation of HB, which can cause fouling in the apparatus, it is preferable that 0.3 to 30 wt% of the mixture (A) flow rate is supplied to the cooling process from the wastewater discharge line 8, and the remainder is recycled to the first reactor A. In this case, to prevent a situation in which HB is likely to accumulate in the reaction system, it is preferable to set the amount introduced to the cooling process to 0.3 wt% or more of the total amount of mixture (A). Furthermore, from the viewpoint of preventing the discharge of a large amount of distillation residue outside the process and thus preventing these treatment facilities from becoming excessive, it is preferable to set the amount introduced to the cooling process to 30 wt% or less of the total amount of mixture (A). In addition, a new catalyst may be supplied from the replenishment catalyst supply line 9, or a catalyst that has gone through the cooling process and solid-liquid separation process described later may be supplied.

[0048] The method for producing alkylene carbonate according to this embodiment is preferably carried out on an industrial scale. In this specification, industrial scale means a scale at which alkylene carbonate is produced at a rate of 1 ton / hour or more. The amount of alkylene carbonate produced in the method for producing alkylene carbonate according to this 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 process and solid-liquid separation process according to this embodiment will be described. Figure 3 shows the schematic configuration of the 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, a stirring blade, and an external circulation mechanism for the refrigerant.

[0050] <Crystallization Apparatus> A mixture (A) containing alkylene carbonate, catalyst, and HB is supplied to the crystallization tank I through the wastewater discharge line 8. The mixture (A) introduced into the crystallization tank I is normally maintained 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 refrigerant in the cooling jacket section. Due to the difference in freezing point and solubility, solids (hereinafter also referred to as "crystals") containing alkylene carbonate and catalyst precipitate from the mixture (A) maintained at this temperature and exist in the tank as a slurry solution. The slurry solution is sent to the solid-liquid separator J from the extraction pipe 10 at the bottom of the crystallization tank. At this time, it is preferable to set the temperature of the crystallization tank I to 36°C or lower in order to ensure a sufficient amount of catalyst precipitate. On the other hand, it is preferable to maintain a temperature of -30°C or higher in order to suppress the increase in viscosity of HB due to low temperatures, improve agitation within the crystallization tank and the transferability of the slurry liquid, and thus maintain good operability.

[0051] Examples of solid-liquid separators J include solid-liquid separators of commonly used separation methods such as centrifugal filtration, pressure filtration, and vacuum filtration. The alkylene carbonate and catalyst crystals separated in the solid-liquid separator J are sent to the catalyst preparation tank H via piping 12, but they may be heated to a liquid state before being sent to the catalyst preparation tank H. Although both alkylene carbonate and catalyst are integrally contained in the crystals, the alkylene carbonate acts as a solvent for the catalyst and the catalyst acts as a catalyst in the aforementioned reaction step, so both are useful even if they are sent to the reaction step in an integral state. The mother liquor separated in the solid-liquid separator J is discharged outside the process via piping 13. In addition, in order to adjust the slurry concentration in the crystallization tank I, a portion of the recovered mother liquor is returned to the crystallization tank I via piping 11. The slurry concentration in the crystallization tank I is preferably maintained at 10 to 40 wt%, more preferably at 15 to 30 wt%. In this case, setting the slurry concentration to 40 wt% or less is preferable because it prevents the proportion of crystals in the slurry solution from increasing, which would worsen the agitation in the crystallization tank and the transferability of the slurry liquid. Also, setting the slurry concentration to 10 wt% or more is preferable because it eliminates the need to increase the amount of mother liquor returned to the crystallization tank I through the piping 11, in other words, the circulation volume of mother liquor, in order to reduce the proportion of crystals in the slurry solution, thus avoiding the need to oversize the crystallization tank and pump.

[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] This embodiment will be specifically described using Figures 2 and 3. Figure 2 shows a schematic configuration of an apparatus used for the production of ethylene carbonate (EC). 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 mixing tank H. Ethylene oxide (EO) was supplied to the first reactor A after being cooled to approximately 5°C. The supply rate was 2495 kg / h. CO ２ is liquefied CO ２ A hot water bath type CO2 ２The mixture (A) was vaporized in an evaporator and supplied to the first reactor A at a constant pressure of approximately 9.8 MPaG at a temperature of approximately 90°C. The supply rate was 3020 kg / h. After purifying the EC in the separation and recovery unit G, the recovered mixture (A) was supplied from the catalyst supply line 7, and the replenishment catalyst solution was supplied from the replenishment catalyst supply line 9. The catalyst solution was prepared in a ratio of mixture (A):replenishment catalyst solution = approximately 9:1. The catalyst solution was supplied so that the KI concentration in the first reactor A was 0.23-0.26 wt%. The supply rate of mixture (A) in the catalyst solution was 290 kg / h, and the supply rate of replenishment catalyst was 32 kg / h. The replenishment catalyst used was catalyst KI, which was prepared in the catalyst preparation tank H to a concentration of 5 wt% in the EC solution. The reaction temperature of the reactor was 180°C.

[0054] The mixture withdrawn from the third reactor E is supplied to the flash tank F through piping 3, and unreacted EO and CO are removed. ２ A small amount of EC was discharged as gas from pipe 4 to the outside of the process. The operating conditions of flash tank F were 760 Torr. Furthermore, a mixture mainly containing EC was withdrawn from the bottom of flash tank F through pipe 5 and introduced into separation and recovery device G. The evaporated and purified EC of 4910 kg / h was withdrawn through pipe 6, and the mixture (A) containing catalyst and HB was withdrawn through catalyst supply line 7. The composition of mixture (A) was EC: 80 wt%, KI: 5 wt%, HB: 15 wt%. A portion of this was supplied to the crystallization process through waste liquid discharge line 8 at a supply rate of 32 kg / h.

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

[0056] [Example 2] 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. In the crystallization apparatus in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 mixing tank H through the pipe 12. The supply rate of 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%. Part of the mother liquor was circulated into the crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 30.5 kg / h and 7 kg / h, respectively. The process fluid in piping 13 was liquid at room temperature of 20°C.

[0057] [Example 3] 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. In the crystallization apparatus in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 mixing tank H through the pipe 12. The supply rate of 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%. Part of the mother liquor was circulated into the crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 218 kg / h and 7 kg / h, respectively. The process fluid in piping 13 was liquid at room temperature of 20°C.

[0058] [Example 4] 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. In the crystallization apparatus in Figure 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 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 solid-liquid mixed phase liquid of the crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the piping 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 mixing tank H through the piping 12. The supply rate of 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%. Part of the mother liquor was circulated into the crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 88 kg / h and 10 kg / h, respectively. The process fluid in piping 13 was liquid at room temperature of 20°C.

[0059] [Example 5] The apparatus shown in Figures 2 and 3 was used in the same manner as in Example 1. The operating conditions in Figure 2 were the same as in Example 1. In the crystallization apparatus in Figure 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 mixture (A) was 32 kg / h. The mother liquor temperature of the crystallization tank I was set to -20°C by external circulation of the refrigerant. The solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 mixing tank H through the pipe 12. The supply rate of 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%. Part of the mother liquor was circulated into the crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 104 kg / h and 6 kg / h, respectively. The process fluid in piping 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 in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 mixing tank H through the pipe 12. The supply rate of crystals was 25 kg / h. The mother liquor had the composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%. Part of the mother liquor was circulated into crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 68 kg / h and 7 kg / h, respectively. The process liquid in piping 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 in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 crystals was 25 kg / h. The mother liquor had the composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%. Part of the mother liquor was circulated into crystallization tank I through piping 11, and part was discharged outside the process through piping 13. The supply rates of the mother liquor were 30.5 kg / h and 7 kg / h, respectively. The process liquid in piping 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 in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 crystals was 25 kg / h. The mother liquor had the composition of EC: 21.5 wt%, NaBr: 14.5 wt%, and HB: 63.9 wt%. A portion of the mother liquor was circulated into crystallization tank I through piping 11, and a portion was discharged outside the process through piping 13. The supply rates of the mother liquor were 218 kg / h and 7 kg / h, respectively. The process liquid in piping 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 in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 crystals was 22 kg / h. The mother liquor had the composition of EC: 39.5 wt%, NaBr: 15.4 wt%, and HB: 45.1 wt%. A portion of the mother liquor was circulated into crystallization tank I through piping 11, and a portion was discharged outside the process through piping 13. The supply rates of the mother liquor were 54 kg / h and 10 kg / h, respectively. The process liquid in piping 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 in Figure 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 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 solid-liquid mixed phase of crystals precipitated in the crystallization tank I and the mother liquor was supplied to the solid-liquid separator J through the extraction pipe 10. The supply rate of the solid-liquid mixed phase 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 mixing tank H through the pipe 12. The supply rate of crystals was 26 kg / h. The mother liquor had the composition of EC: 12.9 wt%, NaBr: 14.7 wt%, and HB: 72.4 wt%. A portion of the mother liquor was circulated into crystallization tank I through piping 11, and a portion was discharged outside the process through piping 13. The supply rates of the mother liquor were 72 kg / h and 6 kg / h, respectively. The process liquid in piping 13 was liquid at room temperature of 20°C.

[0065] [Comparative Example 1] The process was the same as in the example, except that the crystallization apparatus shown in Figure 3 was not used. The mixture (A) containing the catalyst and HB was drawn out through the catalyst supply line 7. The composition of mixture (A) was EC: 80 wt%, catalyst: 5 wt%, HB: 15 wt%. A portion of this was discharged outside the process through the waste liquid discharge line 8. The discharge rate of 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]

[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 unit, H: Catalyst mixing tank, I: Crystallization tank, J: Solid-liquid separator

Claims

1. A method for producing alkylene carbonate, comprising: a reaction step of reacting alkylene oxide and carbon dioxide in a reactor in the presence of an alkali halogen to obtain alkylene carbonate; a cooling step of cooling a mixture (A) containing the alkylene carbonate and alkali halogen obtained through the reaction step; and a solid-liquid separation step of separating the solid containing the alkylene carbonate and alkali halogen from the mother liquor, wherein the alkylene carbonate and alkali halogen separated in the solid-liquid separation step are supplied to the reactor.

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 obtained through the reaction step.

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

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

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

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

7. 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 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 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%.

Images