Method for preparing cyclic carbonates

Abstract

The present invention is directed to a process for continuously reacting a gaseous mixture of an epoxide compound and carbon dioxide in the presence of a heterogeneous catalyst at a pressure between 0.1 and 0.4 MPa in one or more reactors to produce a liquid cyclic carbonate product and a gaseous effluent stream containing unreacted epoxide compound and carbon dioxide. A portion of the gaseous effluent is removed from the process, and another portion of the gaseous effluent is fed to an ejector, where the gaseous effluent is mixed with a gaseous mixture of the epoxide compound and carbon dioxide having a pressure at least 0.3 MPa greater than the pressure of the gaseous effluent. The resulting ejector effluent is fed to one or more reactors.

Description

Technical Field

[0001] The present invention relates to a method of continuously reacting a gas mixture of an epoxide compound and carbon dioxide in one or more reactors in the presence of a heterogeneous catalyst to obtain a liquid cyclic carbonate product and a gas effluent stream containing unreacted epoxide compound and carbon dioxide.

Background Art

[0002] Such a method is described in WO2019 / 125151. This publication describes a method of reacting propylene oxide with carbon dioxide to produce propylene carbonate at a pressure of 0.1 to 0.5 MPa. This reaction is carried out in a slurry with a supported dimeric aluminum salen complex activated by liquid propylene carbonate and benzyl bromide. The supported aluminum salen complex and benzyl bromide remain in the reaction vessel, and liquid propylene carbonate is discharged from the reactor. Unreacted propylene oxide and carbon dioxide separated from the propylene carbonate product can be recycled to the reactor. A portion of this stream may be removed from the process to avoid accumulation of unreacted compounds. This method is carried out at relatively low pressure. Nevertheless, it is necessary to increase the pressure of the gaseous reactants and the described gas recycle before feeding them to the reactor. Such an increase can be achieved using a compressor. The disadvantage of using a compressor is that it introduces complexity into the process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a simpler method that does not have the disadvantages of prior art methods. [Means for solving the problem]

[0005] This objective is achieved by the following method: a gaseous mixture of an epoxide compound and carbon dioxide is continuously reacted in one or more reactors at a pressure between 0.1 and 0.4 MPa in the presence of a heterogeneous catalyst to produce a gaseous effluent containing a liquid cyclic carbonate product and unreacted epoxide compound and carbon dioxide, wherein a portion of the gaseous effluent is removed from this method, and the remaining portion is supplied to an ejector, where the gaseous effluent is then processed. ,air Having a pressure at least 0.3 MPa higher than the pressure of the body effluent. Epoxide compounds and A method of mixing a gaseous mixture with carbon dioxide to obtain an ejector effluent, and supplying the ejector effluent to one or more reactors.

[0006] The applicant, in the ejector ,air Having a pressure at least 0.3 MPa higher than the pressure of the body effluent. Epoxide compounds and When using a gaseous mixture with carbon dioxide, the method according to the present invention has been found to eliminate the need for a compressor or require at least a smaller compressor. This higher-pressure mixture can be advantageously obtained by evaporating a liquid epoxide at high pressure and by evaporating a stored or supplied liquid carbon dioxide at high pressure and mixing the evaporated gaseous components. Thus, high-pressure stored carbon dioxide is used to arrive at a method that does not require a compressor or a compressor of a larger capacity.

[0007] The reactor configuration, the method of supplying the reactants, and the methods of treating the reactor and the product are as described in the aforementioned WO2019 / 125151. Preferably, one or more reactors are two or more reactors in series, including an upstream reactor, a downstream reactor, and an optional intermediate reactor. Preferably, two reactors in series are used. The ejector effluent is supplied to the upstream reactor. Liquid cyclic carbonate products are discharged from all reactors. An intermediate gas effluent containing unreacted epoxide compounds and carbon dioxide is sent from the upstream reactor to the next downstream reactor in the series. A gas effluent stream containing unreacted epoxide compounds and carbon dioxide is discharged from the downstream reactor in the series. Such a method of aligning the reactors in series is advantageous because it allows for the placement of a reactor with a more active catalyst as the downstream reactor, preferably as the furthest downstream reactor. This improves the overall conversion to cyclic carbonate and reduces the amount of epoxide compounds in the gas effluent. This is also advantageous because it results in a smaller amount of valuable epoxide compound being lost through removal.

[0008] The temperature inside the reactor can be between 0 and 200°C, the pressure between 0.1 and 0.4 MPa (absolute), and the temperature is lower than the boiling point of the cyclic carbonate product at the selected pressure. At the upper end of these temperature and pressure ranges, a complex reactor is required. Preferred results regarding selectivity and yield for the desired carbonate product can be achieved at lower temperatures and pressures, so it is preferable that the temperature in one or more reactors is between 20 and 150°C, more preferably between 40 and 120°C, and the absolute pressure is between 0.1 and 0.5 MPa, more preferably between 0.1 and 0.3 MPa. It is preferable that the pressure inside the upstream reactor is higher than the pressure inside the downstream reactor of the series of reactors. This is advantageous because it eliminates the need for special means such as a compressor or blower to create a flow of intermediate gas effluent from the upstream reactor to the downstream reactor.

[0009] Most heterogeneous catalysts deactivate over time. It is preferable to remove the reactor containing the deactivated catalyst from the line and subject it to a catalyst regeneration operation. Disconnecting the line means that reactants such as the epoxide compound and carbon dioxide are not supplied to the reactor, and cyclic carbonates are not discharged from the reactor. In other words, the reactor is not substantially involved in the method of preparing the cyclic carbonate product. Preferably, the catalyst in the upstream reactor is regenerated by disconnecting this reactor from the line such that the second reactor in the series becomes the upstream reactor in the series. The new reactor containing the regenerated catalyst is connected to the series as the downstream reactor. Since the downstream reactor contains the most active catalyst, a high conversion of the epoxide compound is achieved.

[0010] Reactors can be removed from the line and brought back online, and the upstream reactor can be changed to become the downstream reactor at the end of the step, by operating a set of sequence valves and conduits. The duration of one step can be 1 to 30 days, preferably 2 to 20 days. During such a period, the cyclic carbonate product can be prepared continuously in one or more reactors. Regeneration of the deactivated catalyst in the offline reactor can be carried out in a shorter time.

[0011] As mentioned above, the number of reactors in series is preferably two, with one upstream reactor directly coupled to one downstream reactor. Furthermore, one reactor can be regenerated to form a reactor series of three reactors in total. More reactor series may be operated in parallel.

[0012] The gaseous effluent, containing unreacted epoxide compounds and carbon dioxide, is obtained in the downstream reactor of a series of reactors. A portion of the gaseous effluent is removed from the process, and another portion is supplied to an ejector. The removed portion is typically small, e.g., less than 5% by volume of the gaseous effluent. This removal involves the presence of unreacted epoxide compounds and carbon dioxide, as well as several unreacted compounds such as nitrogen and other compounds that may be introduced into the process as trace impurities to the epoxide compounds and / or carbon dioxide feedstocks. The removal is necessary to avoid the accumulation of these unreacted compounds. Since valuable epoxide compounds are lost from the process, it is desirable to keep the removal as small as possible. It is preferable to increase the pressure of the gaseous effluent before using it in the ejector. This is particularly advantageous when two or more reactors are used in series. In a preferred lineup where no means of increasing the pressure of the intermediate gaseous effluent exists, the operating pressure in the downstream reactor is lower than the pressure in the upstream reactor. This pressure loss is adequately compensated for by increasing the pressure of the gaseous effluent. Since the required pressure increase is relatively low, preferably less than 0.1 MPa, the means of increasing the pressure can be simpler than that of a prior art compressor. This pressure increase is preferably achieved by a blower, which is far less complex than a compressor. Alternatively, a blower may be located between the ejector and one or more reactors.

[0013] The catalyst can exist as a fixed bed in the reactor. Preferably, the catalyst exists as a heterogeneous catalyst and a slurry of liquid cyclic carbonate products. The reactor can be any reactor that allows for close contact between the reactants and the catalyst and facilitates the supply of feedstocks. As part of a series of reactors, the reactor is preferably a continuously operated reactor. Such a reactor can be continuously supplied with carbon dioxide and epoxide compounds and continuously discharged with liquid cyclic carbonates and gaseous effluents. The reactor may be equipped with a sparger nozzle for adding the gaseous feedstock compound to the reactor and stirring the suitable catalyst slurry. Stirring can also be achieved by using mechanical stirring means such as an ejector or, for example, an impeller. Such reactors can be so-called bubble column slurry reactors and mechanically stirred tank reactors. In a preferred embodiment, the reactor is a continuously operated stirred reactor to which carbon dioxide and epoxide compounds are continuously supplied. This feedstock is supplied to the upstream reactor as ejector effluent and to other reactors (one or more) as intermediate gas effluent. From this continuously operated stirred reactor, a portion of the cyclic carbonate product is continuously withdrawn as part of the liquid flow, and gas effluent or intermediate gas effluent containing unreacted carbon dioxide and epoxide is continuously withdrawn. In a series of two or more reactors, the reactors are preferably of the same size and design. In an optionally parallel-operated reactor series, the reactors may differ from one reactor to the next.

[0014] When a fixed-bed reactor is used, the catalyst remains in the reactor. When a slurry of a heterogeneous catalyst and a cyclic carbonate product is used, it is preferable to retain the catalyst in the reactor or to return the catalyst to the reactor while a portion of the liquid cyclic carbonate product is discharged from the reactor. Preferably, a certain volume of the liquid cyclic carbonate product is discharged from one or more series reactors corresponding to the generation of the cyclic carbonate product in the reactor, such that the volume of suspended matter in the reactor remains substantially the same. The liquid cyclic carbonate can be separated from the slurryed heterogeneous catalyst by a filter. This filter may be installed outside the reactor. Preferably, the filter is placed inside the reactor. A preferred filter is a cross-flow filter. A preferred supported dimeric aluminum salen complex as a catalyst is a 10 μm filter, more preferably composed of so-called Johnson Screens(R) using Vee-Wire(R) filter elements. The filter may have the shape of a tube placed vertically inside the reactor. The filter may be equipped with means to create a negative flow on the filter to remove any solids from the filter opening.

[0015] In the above method, the liquid cyclic carbonate product can be discharged from all reactors in one or more online reactors, i.e., from the reactor to which the reactants are supplied. Dissolved epoxide compounds may be present in this discharged liquid cyclic carbonate. It is preferable to remove as much of these dissolved epoxide compounds as possible by contacting the liquid cyclic carbonate product with gaseous carbon dioxide obtained by evaporating liquid carbon dioxide. The gaseous carbon dioxide is properly removed before being mixed with the epoxide compounds. In this way, a purified product stream of cyclic carbonate is obtained.

[0016] A higher-pressure mixture can be obtained by evaporating liquid epoxide under high pressure, evaporating high-pressure liquid carbon dioxide, and mixing the evaporated gaseous components. The pressure of the liquid epoxide compound is preferably increased by a pump if the liquid epoxide compound is stored or supplied at too low a pressure. The resulting pressurized liquid epoxide compound then evaporates as its temperature rises and some of its pressure decreases. The pressure can be reduced, for example, by a throttle valve. The partially evaporated epoxide compound is separated from the remaining liquid epoxide compound in a gas-liquid separator. The unevaporated epoxide compound is appropriately recycled to a heat exchanger via a pump. The pressure of the gaseous epoxide compound is preferably between 0.5 and 0.8 MPa.

[0017] The starting liquid carbon dioxide can be stored or supplied via a pipeline. The liquid carbon dioxide preferably has a high pressure between 1.4 and 4 MPa. This method advantageously utilizes this high pressure. Evaporation can be carried out in a vaporizer where substantially gaseous carbon dioxide is obtained. This gas can then be heated in a heat exchanger to a temperature between 80 and 120°C and used for the preferred removal of the liquid cyclic carbonate product stream as described above. The pressure of the gaseous carbon dioxide is preferably between 0.5 and 0.8 MPa, and more preferably substantially the same as the pressure of the gaseous epoxide compound. This allows the gaseous carbon dioxide and the gaseous epoxide compound to be combined and supplied to the ejector. gas Having a pressure at least 0.3 MPa higher than the pressure of the spilled material. Epoxide compounds and A gaseous mixture with carbon dioxide can be obtained.

[0018] Heterogeneous catalysts can be any catalyst suitable for catalyzing the reaction of carbon dioxide and epoxides to cyclic carbonates and that is appropriately activated by halogenated compounds. More specifically, heterogeneous catalysts include organic compounds containing one or more nucleophiles, such as quaternary nitrogen halides. Preferred heterogeneous catalysts are supported dimeric aluminum salen complexes, with halogenated compounds as the activating compounds.

[0019] The supported dimeric aluminum salen complex can be any supported complex as disclosed by EP2257559B1 described above. Preferably, the complex is represented by the following formula.

[0020] [Chemical formula] In the formula, S represents a solid support linked to a nitrogen atom via an alkylene bridging group, where the supported dimeric aluminum salen complex is activated by a halogenated compound. The alkylene bridging group can have 1 to 5 carbon atoms. X 2 can be C6 cyclic alkylene or benzylene. Preferably, X 2 is hydrogen. X 1 is preferably tertiary butyl. Et in the above formula represents any alkyl group, preferably having 1 to 10 carbon atoms. Preferably, Et is an ethyl group.

[0021] S represents a solid support. A catalyst complex can be linked to such a solid support by (a) covalent bonding, (b) stereotrapping, or (c) electrostatic bonding. For covalent bonding, the solid support S needs to contain, or be derivatized to contain, reactive functional groups that can help link the compound to its surface by covalent bonding. Such materials are well known in the art and include, for example, silicon dioxide supports, polyacrylamide supports, polystyrene supports, and polyethylene glycol supports containing reactive Si-OH groups. A further example is sol-gel materials. Silica can be modified to contain 3-chloropropyloxy groups by treatment with (3-chloropropyl)triethoxysilane. Another example is Al columnar clay, which can also be modified to contain 3-chloropropyloxy groups by treatment with (3-chloropropyl)triethoxysilane. In the present invention, solid supports of particular interest for covalent bonding include siliceous MCM-41 and MCM-48, ITQ-2 and amorphous silica, SBA-15 and hexagonal mesoporous silica, which may be modified with 3-aminopropyl groups. Sol-gels are also of particular interest. Other conventional forms may also be used. For stereotrapping, the most suitable class of solid supports is zeolite, which may be natural or modified. The pore size must be small enough to trap the catalyst, but large enough to allow reactants and products to enter and exit the catalyst. Suitable zeolites include zeolites X, Y and EMT, as well as those partially decomposed to provide mesoporosity, enabling easier transport of reactants and products. For electrostatic bonding of the catalyst to the solid support, typical solid supports may include silica, Indian clay, Al columnar clay, Al-MCM-41, K10, laponite, bentonite, and zinc-aluminum layered double hydroxide. Among these, silica and montmorillonite clay are of particular interest. Preferably, the support S is a particle selected from the group consisting of silica, alumina, titania, siliceous MCM-41, or siliceous MCM-48.

[0022] Preferably, the heterogeneous catalyst is present as a slurry in the form of a powder in which the support S has dimensions such that it is small enough to create a high catalytic active surface per weight of the support and large enough to be easily separated from the cyclic carbonate inside or outside the reactor. Preferably, the support powder particles have a particle size exceeding 10 μm and less than 2000 μm for at least 90% by weight of all the particles. The particle size is measured by a Malvern(R) Mastersizer(R) 2000.

[0023] The supported catalyst complex as shown above is activated by a halogenated compound. The halogenated compound contains a halogen atom, which can be Cl, Br or I, and preferably is Br. The quaternary nitrogen atom of the complex shown above is paired with a halide counterion. A possible activating compound is exemplified by tetrabutylammonium bromide as a possible activating compound described in EP2257559B1. Benzyl bromide is a preferred activating compound since it can be separated by distillation from preferred cyclic carbonate products such as propylene carbonate and ethylene carbonate.

[0024] Examples of preferred supported dimeric aluminum salen complexes activated by benzyl bromide are shown below (where Et is ethyl, tBu is tert-butyl, and Osilica represents a silica support).

[0025]

Chemical formula

[0026] In use, the Et group in the above formula can be exchanged with an organic group of the halogenated compound. For example, when benzyl bromide is used as the halogenated compound to activate the above supported dimeric aluminum salen complex and the catalyst is reactivated, the Et group is exchanged with a benzyl group.

[0027] An alternative to the above-described supported dimeric aluminum salen complex may be a supported catalyst in which the aluminum salen complex portion is connected to a support. By arranging these monomers close enough to each other, the same catalytic effect as the above-described dimeric salen complex can be achieved. Optionally, a supported monomer aluminum salen complex can be reacted with an adjacent monomer aluminum salen complex to obtain the above-described supported dimeric aluminum salen complex having two linkage bridges to the support instead of one linkage bridge.

[0028] The cyclic carbonate product present in the purified product, such as that obtained in the stripper or directly in the reactor, may further contain an activated halogenated compound. This halogenated compound is appropriately separated from the cyclic carbonate in the distillation step, where the purified cyclic carbonate product is obtained as the bottom product of the distillation step. The halogenated compound obtained in the distillation step is appropriately used to activate the deactivated catalyst in an offline mode as described above.

[0029] It is preferable that the liquid cyclic carbonate product discharged from one or more reactors or the purified product stream obtained in the stripper passes through a buffer vessel upstream of the distillation step. In the method in which a heterogeneous catalyst is supported on a dimerized aluminum salen complex and the activating compound is a halogenated compound, the reaction between the epoxide compound and carbon dioxide occurs, and the amount of the dimerized aluminum salen complex present in one or more reactors expressed in kmol, preferably in the upstream and downstream reactors, is m 3 The volume of the buffer container (one or more) represented by this formula is 5 to 50 m³. 3 The concentration is preferably between / kmol. Such a buffer vessel averages out the content of halogenated compounds in the feed to the distillation column, thereby simplifying the distillation operation.

[0030] The present invention should be illustrated using Figures 1 and 2. [Brief explanation of the drawing]

[0031] [Figure 1] The present invention provides a possible lineup of methods for preparing cyclic carbonates from epoxide compounds and carbon dioxide, wherein a compressor (2) is used to increase the pressure of the gaseous epoxide compound (1) to the pressure inside the reactor (10). [Figure 2] An embodiment of the present invention that does not use a large compressor (2) as shown in Figure 1 is shown. [Figure 3] Indeed, the same embodiment according to the present invention is shown, except that the blower is located downstream of the ejector (36), as in Figure 2. [Modes for carrying out the invention]

[0032] Figure 1 shows a possible lineup of methods for preparing a cyclic carbonate from an epoxide compound and carbon dioxide, not relating to the present invention, in which a compressor (2) is used to raise the pressure to the pressure in a reactor (10) of the gaseous epoxide compound (1). The epoxide, at increased pressure (8), is mixed with carbon dioxide (5) at approximately the same pressure. The carbon dioxide (5) contains some of the epoxide compound obtained in a stripper (4) by contacting the liquid cyclic carbonate product (6) with gaseous carbon dioxide (3), resulting in a washed cyclic carbonate (7). The combined epoxide compound and gaseous carbon dioxide mixture (9) is fed into an upstream reactor (10) containing a slurry of a heterogeneous catalyst activated by a halogenated compound. From this upstream reactor (10), the first cyclic carbonate product (12) is discharged, and an intermediate gas effluent (11) is obtained. The intermediate gas effluent (11) is fed into a downstream reactor (13) containing a slurry of a heterogeneous catalyst. This reactor (13) is operated at a lower pressure than reactor (10). A second cyclic carbonate product (14) is discharged from this downstream reactor (13), yielding a gaseous effluent (15). A portion of the gaseous effluent (15) is removed as waste (16), and the remainder of the gaseous effluent (15) is recycled and combined with a gaseous epoxide compound (1) upstream of compressor (2). The first (12) and second (14) cyclic carbonate streams are collected in a buffer vessel (18). From this vessel, the combined liquid cyclic carbonate product (6) is supplied to stripper (4). A third reactor (19) is shown containing a slurry of heterogeneous catalysts that are regenerated in offline mode by the addition of a halogenated compound (20).

[0033] Figure 2 shows an embodiment of the present invention that does not use a large compressor (2) as shown in Figure 1. Liquid propylene oxide stored at 16°C and 0.2 MPa is pressurized by a pump (21a) and mixed with a return flow (26a) of liquid propylene oxide having a temperature of 94°C and a pressure of 1.3 MPa. The resulting mixture is heated to 130°C in a heat exchanger (22), and the pressure and temperature are reduced in a throttle valve (23) to a gas (27) and liquid (25) with a pressure of 0.6 MPa and a temperature of 95°C. The liquid (25) is recycled via a pump (26) to become a pressurized return flow (26a).

[0034] Liquid carbon dioxide (28) stored at a pressure of 1.9 MPa is vaporized again in a vaporizer (29), and its temperature is raised in a heat exchanger (30) to obtain gaseous carbon dioxide (31) at a temperature of 100°C and a pressure of 0.6 MPa. In the stripper (32), purified propylene carbonate (34) is obtained by contacting the liquid propylene carbonate product (33) with gaseous carbon dioxide (31). The carbon dioxide (35) discharged from the stripper (32) contains some regenerated propylene oxide. This carbon dioxide (35) is combined with gaseous propylene oxide (27) obtained in the gas-liquid separator (24), and the resulting mixture is supplied to the ejector (36) as a high-pressure feed to the ejector at a pressure of 0.6 MPa. Furthermore, pressurized gaseous effluent (37) with a pressure of 0.23 MPa is supplied to the ejector (36), and ejector effluent (38) with a pressure of 0.26 MPa is obtained. The ejector effluent (38) is supplied to an upstream reactor (39) containing a slurry of heterogeneous catalyst activated by a halogenated compound. From this upstream reactor (39), the first propylene carbonate product (40) is discharged, and an intermediate gaseous effluent (41) is obtained. The intermediate gaseous effluent (41) is supplied to a downstream reactor (42) containing a slurry of heterogeneous catalyst. This reactor (42) is operated at 0.17 MPa. From this downstream reactor (42), the second propylene carbonate product (43) is discharged, and a gaseous effluent (44) is obtained. A portion of the gaseous effluent (44) is removed as waste (45), and the remaining portion of the gaseous effluent (46) is pressurized to 0.23 MPa in the blower (47) to become pressurized gaseous effluent (37). The blower (47) can be thought of as a compressor, and is much smaller than the compressor (2) in Figure 1.

[0035] The first (40) and second (43) propylene carbonate streams are collected in a buffer vessel (48). From this vessel, the combined liquid propylene carbonate product (33) is supplied to a stripper (4). A third reactor (50) is shown containing a slurry of heterogeneous catalysts that are regenerated in offline mode by the addition of a halogenated compound (51).

[0036] Figure 3 shows the same embodiment according to the present invention as in Figure 2, except that the blower is located downstream of the ejector (36). The blower (52) further increases the pressure of the ejector effluent (38) before it is supplied as a flow (53) to the upstream reactor (39). [Examples]

[0037] [Comparative example A] The heat and mass balances are calculated using the method shown in Figure 1. Gaseous epoxide is supplied at 4.5 kg / second (Figure 1, 1), fresh carbon dioxide at 3.5 kg / second (Figure 1, 5), and the recycle flow is set to 2 kg / second (Figure 1, 17). The pressure of the gaseous epoxide, recycle flow, and resulting mixture rising compressor (2) is 0.7 barg. The energy input required to heat the feedstock A from 16°C to 55°C is calculated. Energy input for pressurizing the CO2 feedstock (stored at 10+ barg) is not considered. The required compression load of compressor (2) in Figure 1 is calculated to compress the gaseous epoxide and recycle mixture from 0.7 barg to the specified reactor inlet pressure of 2.1 barg. The polytropic compression energy is calculated using a compression efficiency of 65% for the compression load calculation. The calculated energy consumption is shown in Table 1.

[0038] [Example 1 of the Invention] The heat and mass balances are calculated using the method shown in Figure 3. Gaseous epoxide is supplied at 4.5 kg / second (Figure 3, 27), fresh carbon dioxide at 3.5 kg / second (Figure 3, 35), and the recycle flow is set to 2 kg / second (Figure 3, 46). The energy calculation takes into account the energy input for heating the epoxide feedstock from 16°C to 110°C (at 100°C, the vapor pressure of feedstock A is 5 barg), and the additional superheating up to 110°C to prevent undesirable condensation in the downstream piping. The energy input for pressurizing the CO2 feedstock (supplied and stored at 10+ barg) is not taken into account. In the static ejector (Figure 3, 36), the flow (46) is pressurized to the resulting discharge pressure. The discharge pressure is calculated using values ​​provided by the static ejector equipment supplier, based on predetermined ratios of flows (27), (35), and (46). The remaining compressive load required for the compressor / blower (52) between the elector (36) and the upstream reactor (39) is calculated to achieve the same pressure as in the comparative example. For the calculation of the compressive load of (52), the polytrope compressive energy is calculated using a 65% compressive efficiency.

[0039] The energy balances of both parties are calculated and compared in Table 1.

[0040] [Table 1]

[0041] The energy consumption figures presented in Table 1 show that, overall, the energy benefit of using static ejectors to increase the recycle flow is equal to 3.7% in this example calculation. Furthermore, the CAPEX cost is reduced by miniaturizing the required gas compressor, which can be replaced with relatively inexpensive static elements such as ejectors. The thermal energy load can also be further reduced by applying additional thermal integration to the entire plant, which requires a net cooling load (exothermic processes). In this case, the net energy benefit increases further when using static ejectors, as the amount of electrical energy load (which cannot be replaced) is greater in conventional methods.

[0042] The applicant found that the method in Figure 2 consumes less energy. The carbon dioxide loss resulting from operating the stripper at higher pressure in the method in Figure 3 is less, and this is fully compensated for by the advantage of not having to use a complex compressor and by the lower energy requirements.

Claims

1. A method for continuously reacting a gaseous mixture of an epoxide compound and carbon dioxide in one or more reactors at a pressure between 0.1 and 0.4 MPa in the presence of a heterogeneous catalyst to produce a gaseous effluent containing a liquid cyclic carbonate product and unreacted epoxide compound and carbon dioxide, wherein a portion of the gaseous effluent is removed from this method, another portion of the gaseous effluent is supplied to an ejector, in which the gaseous effluent is mixed with a gaseous mixture of an epoxide compound and carbon dioxide having a pressure at least 0.3 MPa higher than the pressure of the gaseous effluent to obtain an ejector effluent, and the ejector effluent is supplied to the one or more reactors.

2. The method according to claim 1, wherein the pressure of the gaseous effluent is increased by a blower before the gaseous effluent is mixed in the ejector.

3. The method according to any one of claims 1 to 2, wherein the gaseous mixture of an epoxide compound and carbon dioxide supplied to the ejector is obtained by mixing gaseous epoxide obtained by evaporating liquid epoxide with gaseous carbon dioxide obtained by evaporating liquid carbon dioxide having a pressure between 1.4 and 4 MPa.

4. The method according to claim 3, wherein a liquid cyclic carbonate product is discharged from one or more reactors, and any epoxide compounds present in the discharged liquid cyclic carbonate product are removed by contacting the liquid cyclic carbonate product with gaseous carbon dioxide, thereby obtaining a purified product stream.

5. The method according to claim 4, wherein the pressure of the gaseous carbon dioxide is between 0.5 and 0.8 MPa.

6. The method according to any one of claims 1 to 5, wherein the one or more reactors are two or more reactors in series, including an upstream reactor, a downstream reactor, and an arbitrary intermediate reactor, wherein the ejector effluent is supplied to the upstream reactor, a liquid cyclic carbonate product is discharged from all reactors, an intermediate gas effluent containing unreacted epoxide compound and carbon dioxide is sent from the upstream reactor of the series to the next downstream reactor, and a gas effluent containing unreacted epoxide compound and carbon dioxide is discharged from the downstream reactor of the series.

7. The method according to claim 6, wherein the catalyst in the upstream reactor is regenerated by taking the reactor offline such that the second reactor in the series becomes the upstream reactor in the series, and a new reactor containing the regenerated catalyst is connected to the series as the downstream reactor.

8. The method according to any one of claims 6 to 7, wherein the heterogeneous catalyst is present as a slurry in two or more reactors in series, the temperature of the two or more reactors is between 20 and 150°C, and the pressure is below the boiling point of the cyclic carbonate product at a selected pressure.

9. The method according to any one of claims 1 to 8, wherein the heterogeneous catalyst comprises an organic compound containing one or more quaternary halogenated nitrogen groups.

10. The method according to claim 9, wherein the heterogeneous catalyst is a dimeric aluminum salen complex on which the catalyst is supported, and the activating compound is a halogenated compound.

11. The supported dimerized aluminum salen complex is given by the following formula 【Chemistry 1】 [In the formula, S represents a solid support linked to a nitrogen atom via an alkylene group, where the supported dimeric aluminum salen complex is activated by a halogenated compound, X １ It is tertiary butyl, and X ２ [where is hydrogen, and Et is an alkyl group having 1 to 10 carbon atoms.] The method according to claim 10, as represented by the present invention.

12. The method according to claim 11, wherein the support S is composed of particles having an average diameter between 10 and 2000 μm.

13. The method according to claim 12, wherein the support S is a particle selected from the group consisting of silica, alumina, titania, siliceous MCM-41, or siliceous MCM-48.

14. The method according to any one of claims 10 to 13, wherein the halogenated compound is benzyl halogenate.

15. The method according to claim 14, wherein the benzyl halogenate is benzyl bromide.

16. The method according to any one of claims 1 to 15, wherein the epoxide compound is ethylene oxide, propylene oxide, butylene oxide, or pentene oxide.

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