Process for the preparation of organic carbonates

Abstract

The invention relates to a process for the preparation of organic carbonates, in particular diethyl carbonate, comprising a catalytic reaction of corresponding alcohols (ROH) with carbon dioxide, wherein R is a straight-chain or branched-chain alkyl group having 1-6 carbon atoms, preferably an ethyl group, and wherein water formed during the catalytic reaction is separated off via at least one inorganic membrane (21) and / or at least one hybrid membrane (21), characterised in that the catalyst comprises cerium oxide (CeO2) and in that the catalytic reaction is carried out at a temperature of at least 80°C and at a pressure of at least 5 bar.

Description

[0001] Process for the production of organic carbonates

[0002] The invention relates to a process for the preparation of organic carbonates, in particular diethyl carbonate, comprising a catalytic reaction of corresponding alcohols (ROH) with carbon dioxide, wherein R is a straight- or branched-chain alkyl radical having 1-6 carbon atoms, preferably an ethyl radical, and wherein water formed during the catalytic reaction is separated off via at least one inorganic membrane and / or at least one hybrid membrane.

[0003] The invention relates to a reactor for producing organic carbonates, in particular diethyl carbonate, wherein the reactor has at least one reactor module, and the reactor module has a reaction chamber, wherein the reaction chamber is separated by at least one inorganic membrane and / or at least one hybrid membrane from a discharge chamber for discharging water from the reaction chamber.

[0004] Organic carbonates are used, among other things, as starting materials for the synthesis of plastics, pharmaceuticals, veterinary agents, pesticides, dyes, photographic chemicals, and as electrolytes in lithium-ion batteries. Although they are currently used primarily as raw materials in the chemical industry, they are suitable as fuels or fuel additives to reduce exhaust emissions. Diethyl carbonate, in particular, has proven particularly advantageous as a fuel additive. When blended, less carbon monoxide (CO), particulate matter, and smoke are emitted. When DEC is produced from renewable sources, fossil CO2 emissions are also reduced. In particular, the possibility of blending it with diesel, compared to the starting product ethanol, has great ecological and economic potential.

[0005] The synthesis of organic carbonates occurs using CO2 and corresponding alcohols as starting materials, with the organic carbonate and water being formed during the catalytic reaction. The reaction equation for this catalytic reaction is therefore generally:

[0006] 2 R ' OH + CO2

[0007] For example, when using ethanol as the alcohol, diethyl carbonate can be produced:

[0008] As the end product of combustion processes, CO2 is thermodynamically stable and only reactive with high energy input. The formation of organic carbonates from CO2 and alcohol is exothermic and does not occur spontaneously at room temperature. It has been shown that removing the water produced during the catalytic reaction greatly promotes the reaction. Therefore, water-binding substances (chemical water scavengers) have been used to remove the water.

[0009] However, this is not very practical for the production of larger quantities, as the water scavenger must either be removed from the reaction mixture and regenerated or even discarded. Furthermore, contamination of the final product can occur. Therefore, these processes are not suitable for the production of organic carbonates on a larger, industrial scale.

[0010] In Wang et al., 2017 1 A process and reactor are disclosed that produce diethyl carbonate under ambient pressure using a CeO.8ZrO.2O.2 catalyst. The water is continuously removed via an inorganic membrane during the reaction. However, this only allows for a very low yield, according to the document, of approximately 0.06%.

[0011] CN 112657434 A discloses another process and reactor for electrochemical synthesis that operates at a somewhat higher pressure and temperature range. A transition metal such as Cu, Fe, Ni, Co, or Zn is used as the catalyst. The metal is supported on a CeC carrier, which provides mechanical support. The resulting water is separated by a polyimide membrane. For the reaction to occur, current must be supplied via electrodes. This requires higher energy consumption and a more complex reactor design. Furthermore, this embodiment has also proven to produce unsatisfactory results.

[0012] In Kuenen et al., 2016 2 , it is proposed to use a cerium oxide catalyst in combination with a PEEK-chitosan membrane - a polymer membrane. This has an insufficient yield. The document describes the

[0013] 1Wang, J., Hao, Z., Wohlrab, S., 2017. Continuous CO2 esterification to diethyl carbonate (DEC) at atmospheric pressure: application of porous membranes for in situ H2O removal. Green Chem. 19, 3595-3600. https: / / doi.org / 10.1039 / C7GC00916J

[0014] 2 Kuenen, HJ, Mengers, HJ, van der Ham, AGJ, & Kiss, AA (2016). Novel Process for Conversion of CO2 to Dimethyl Carbonate using Catalytic Membrane Reactors. In 26 European Symposium on Computer Aided Process Engineering, 2016 (Vol. 38, pp. 991-996). (Computer Aided Chemical Engineering; Vol. 38). Elsevier. https: / / doi.org / 10.1016 / B978-0-444-63428-3.50170-3 direct synthesis of dimethyl carbonate from methanol and CO2 in a membrane reactor with in-situ water separation. Furthermore, the data were obtained using a simulation, which means that no statement can be made as to whether the presented membrane can maintain the stated selectivity even at elevated temperatures in practice.

[0015] The object of the invention is to provide a process and a reactor by means of which organic carbonates can be produced in larger quantities and a higher yield is achieved.

[0016] This object is achieved according to the invention in that the catalytic reaction is carried out at a temperature of at least 80°C and at a pressure of at least 5 bar and in that the catalyst comprises at least one of the substances mentioned: cerium oxide (CeC), ZrC, CrC, Fe, Cu, Mg, Ni, SiC, Al2O3, TiO, MoO, BiO, ZnO, Ta2O5, Nb2O5 or an alloy comprising copper and nickel.

[0017] It is also achieved by arranging a catalyst in the reaction chamber and by the catalyst comprising at least one of the substances mentioned: cerium oxide (CeC), ZrC, CrC, Fe, Cu, Mg, Ni, SiC, Al2O3, TiO, MoO, BiO, ZnO, Ta2O5, Nb2O5 or an alloy comprising copper and nickel.

[0018] The specified metals iron, copper, magnesium and / or nickel (Fe, Cu, Mg and / or Ni) are preferably part of the catalyst in metallic form, but they can also be present in other forms, for example in the form of a salt, oxide or an organic compound.

[0019] Preferably, the catalyst is at least partially immobilized on a support material. This can be, for example, activated carbon. This is particularly advantageous when the catalyst comprises metals such as Fe, Cu, Mg, and / or Ni. The support material can be bonded to the membrane and / or be part of the membrane. For example, at least one layer comprising support material and catalyst can be arranged on the membrane, with this membrane preferably being water-permeable and / or porous. This ensures that the reaction takes place in the immediate vicinity of the membrane.

[0020] Inorganic membranes and hybrid membranes have been shown to be particularly well suited for use at higher pressures and temperatures. Even under these conditions, they exhibit high selectivity for water and can remove larger amounts of water from the reaction space. Organic membranes can swell under certain circumstances and become increasingly impermeable to water. The use of inorganic membranes or hybrid membranes prevents this. The membrane is permeable to water. Preferably, it is essentially impermeable, or at least more impermeable than its permeability to water, to the starting materials, i.e., CO2 and / or the alcohol, and / or essentially impermeable, or at least more impermeable than its permeability to water, to the end product, i.e., the organic carbonate.In this way, the resulting water can be selectively removed from the space in which the reaction takes place, thus shifting the reaction equilibrium to the side of the organic carbonate.

[0021] The membrane can comprise multiple layers, each with different materials or properties. Multiple membranes can separate water parallel to each other, or multiple membranes can be arranged parallel to each other between the reaction chamber and the separation chamber. "Parallel to each other" does not mean the spatial alignment of the membrane surfaces to each other, but rather that the two membranes are not arranged one behind the other between the reaction chamber and the separation chamber, but rather that the water separation on the membranes occurs parallel to each other.

[0022] In general, membranes can be divided into three different materials: organic, inorganic, and a combination of the two (hybrid).

[0023] Organic polymer membranes are generally widely used in membrane technology because they are comparatively inexpensive and, thanks to the choice of polymers and their easily controllable production, membrane specifications can be more easily adapted to customer requirements. However, polymer membranes tend to swell at elevated temperatures, which are necessary for our process, thereby significantly reducing selectivity. Polymer-based pervaporation membranes presented in the literature are described for temperatures up to 60°C. However, since the process according to the invention requires temperatures >100°C, these membranes no longer achieve sufficient selectivity at elevated temperatures. Some manufacturers have presented experimental special membranes for temperatures up to 110°C, but these have significantly poorer properties.Other, classic high-temperature membrane materials such as polyimide do not have sufficiently good performance (selectivity).

[0024] Inorganic membranes are generally made of a ceramic or zeolite material, which makes them suitable for higher temperatures or more aggressive media. Compared to polymer membranes, manufacturing is more complex, and the options for adapting specifications to customer requirements are less extensive. Furthermore, inorganic membranes are more expensive and more susceptible to mechanical stress.

[0025] So-called hybrid membranes are also known, which include both organic and inorganic materials.

[0026] Preferably, a membrane, particularly preferably a hybrid membrane, has at least one at least predominantly inorganic and / or at least one at least predominantly organic layer. The at least predominantly inorganic layer can comprise materials such as at least one ceramic (for example, oxidic ceramic, and / or based on aluminum, zirconium oxide, and / or silicon oxide), carbide, and / or zeolite. The at least predominantly organic layer can comprise materials such as PVA (polyvinyl alcohol).

[0027] It can be provided that the membrane, preferably a hybrid membrane, has at least one at least predominantly inorganic carrier layer, preferably comprising at least one ceramic, and / or that the membrane has at least one further layer, preferably comprising at least one organic material, particularly preferably a polymer material. The further layer preferably has a higher selectivity towards water than the carrier layer.

[0028] The combination of the inorganic carrier and the organic layer minimizes the swelling of the organic material, which means that good selectivity results can be expected even at elevated temperatures.

[0029] Particularly preferably, the membrane comprises at least one polymer-metal carbide membrane. These membranes exhibit particularly good temperature stability.

[0030] The hybrid membrane may comprise at least one single layer containing organic and inorganic materials. A single layer refers to a layer that cannot be subdivided into different sublayers depending on their materials. The organic and inorganic materials may be mixed together. Such membranes are sometimes also called mixed matrix membranes.

[0031] It can be provided that the hybrid membrane has at least one layer comprising an organic matrix in which inorganic material is arranged, preferably particles and / or preferably the catalyst and / or adsorbent. Further examples of membrane materials can be found in Vane et al. 3 .

[0032] Surprisingly, it has been found that particularly high yields can be achieved when the specified substances are used as catalysts and at higher temperatures and pressures. The need for a power supply, as is necessary for the electrochemical reduction of CO2 using transition metals, can be dispensed with. A catalyst comprising cerium oxide (CeC) has proven particularly efficient. Particularly high yields have been achieved with such a catalyst.

[0033] Surprisingly, it has been shown that a higher temperature of at least 80°C has a positive effect on the yield and reaction rate, even though the reaction is exothermic, i.e. it releases heat.

[0034] The reaction chamber of the reactor module is the space in which the catalyst is located and into which the starting materials are fed so that a catalytic reaction can take place. It is essential that the pressure and temperature in this reaction chamber correspond to the specified values ​​so that the reaction proceeds efficiently and as completely as possible.

[0035] The discharge chamber is preferably catalyst-free and serves to drain the water that is discharged from the reaction chamber via the membrane into the discharge chamber. The water produced by the reaction penetrates the membrane and separates into the discharge chamber, where it can be discharged, for example, via a water outlet or stored in a water tank.

[0036] Preferably, the membrane defines the reaction space on at least one side. It can therefore be arranged so that the catalyst and the membrane are arranged side by side. This allows the water formed to be removed via the membrane immediately after it is formed. This applies to both the process according to the invention and the reactor according to the invention.

[0037] Preferably, the pressure in the discharge chamber differs from the pressure in the reaction chamber by less than 6 bar. This prevents excessive pressure loading on the membrane.

[0038] The catalytic reaction can be carried out continuously or discontinuously.

[0039] 3Vane LM. Review: Membrane Materials for the Removal of Water from Industrial Solvents by Pervaporation and Vapor Permeation. J Chem Technol Biotechnol. 2019;94(2):343-365. doi: 10.1002 / jctb.5839. PMID: 30930521 ; PMCID: PMC6436640.A reactor for producing organic carbonates, in particular diethyl carbonate, can also be advantageous, wherein the reactor has at least one reactor module, and the reactor module has a reaction space which is separated from a discharge space for discharging water from the reaction space by at least one organic, inorganic membrane and / or hybrid membrane, wherein a catalyst, preferably immobilized on a molecular sieve or similar support materials, such as at least one polymer, is arranged in the reaction space and the catalyst comprises at least one of the substances mentioned: cerium oxide (CeC), ZrC, CrC, Fe, Cu, Mg, Ni, SiC, Al2O3, TiO, MoO, BiO, ZnO, TazOs, NbzOs or an alloy comprising copper and nickel.

[0040] Accordingly, a process for the production of organic carbonates, in particular diethyl carbonate, may also be advantageous, comprising a catalytic reaction of corresponding alcohols (ROH) with carbon dioxide, where R is a straight- or branched-chain alkyl radical having 1-6 carbon atoms, preferably ethyl alcohol, wherein water formed during the catalytic reaction is separated off via at least one organic or inorganic membrane and / or hybrid membrane, and wherein the catalyst comprises a catalyst which has been immobilized on a molecular sieve or similar support material prior to carrying out the catalytic reaction, and that the catalytic reaction is carried out at a temperature of at least 80°C and at a pressure of at least 5 bar, and that the catalyst comprises at least one of the substances mentioned: cerium oxide (CeC), ZrC, CrC, activated carbon (Fe, Cu, Mg, Ni), SiO2, Al2O3, TiO, MoO, BiO, ZnO, Ta2O5,Nb20s or an alloy comprising copper and nickel.,

[0041] Embodiments according to the last two paragraphs are particularly advantageous because they enable effective implementation in a particularly simple manner. They can be combined with all special features and embodiments described in this description or the claims. By arranging the catalyst on a molecular sieve, i.e., a molecular sieve, or similar support materials, a particularly large surface area is achieved, which is particularly useful for catalytically accelerating the process. The arrangement on a molecular sieve is particularly advantageous in combination with the membrane because such complex membrane structures, which offer the largest possible membrane surface area for water drainage and give the reaction spaces a spatially angled shape, can be combined particularly well with the largest possible catalyst.Despite the complex and intricate spatial structure of the reaction chamber, it can be easily and densely filled with the molecular sieve, which, thanks to its lumpy shape, still fills the space well. Molecular sieves are typically available in free-flowing, lumpy form, such as granules or pellets. This allows a particularly large membrane surface area to be combined with a particularly large catalyst surface area in a small space, leading to a synergistic improvement in yield. Furthermore, applying the sieve to the support material has the advantage that it is not loose in the reaction chamber, which can lead to blockages.

[0042] It is particularly advantageous if the reaction is carried out at at least 100°C, preferably at least 120°C, and particularly preferably between 110°C and 150°C, and / or if the reaction is carried out at at least 10 bar, preferably at a pressure above 12 bar and / or above 15 bar, and particularly preferably between 20 bar and 40 bar. As explained above, these temperature and pressure ranges enable particularly high yields, although this initially appears paradoxical due to the exothermic reaction. A particularly high yield could be achieved in particular at a temperature between 110°C and 150°C and / or a pressure above 12 bar, but especially at a pressure between 20 bar and 40 bar.

[0043] In a preferred embodiment, the separation via the membrane is carried out by membrane pervaporation and / or vapor permeation. This allows for particularly efficient water separation, particularly at higher pressures and temperatures. Accordingly, the membrane can also be designed to separate water by membrane pervaporation and / or vapor permeation.

[0044] It is particularly advantageous if the separation takes place via at least one carbon membrane and / or at least one ceramic membrane, particularly preferably at least one zeolite membrane. It has been shown that such membranes, especially zeolite membranes, exhibit good selectivity for water despite the high pressure and high temperatures and remain stable over long periods of time. The same applies if the membrane is intended to comprise a carbon membrane and / or a ceramic membrane, particularly preferably a zeolite membrane.

[0045] Furthermore, it is advantageous if the catalytic reaction is carried out in at least one reactor module in which the catalyst is arranged. This enables a compact and controlled reaction process in the reactor module. The reactor module can have one or more reaction chambers in which the catalyst is arranged and in which the catalytic reaction can take place. It is particularly advantageous if the reaction chamber is separated from a discharge chamber for discharging water from the reaction chamber by at least one inorganic membrane and / or hybrid membrane. This allows the water to be separated immediately after it is formed during the catalytic reaction. This minimizes the residence time of the water near the catalyst.

[0046] In this sense, it is also advantageous if the reactor has at least one carbon dioxide source and at least one alcohol source (ROH), where R is a straight- or branched-chain alkyl radical with 1-6 carbon atoms, preferably ethyl alcohol. These sources can be, for example, storage media for the substances, such as a CO2 bottle or a container with alcohol. It is also possible for the source itself to produce the substance directly; for example, the carbon dioxide source can be an internal combustion engine that generates carbon dioxide through the combustion of fuel. Other carbon dioxide sources could be plants that release carbon dioxide biologically, for example through fermentation, or chemical plants. A plant for extracting carbon dioxide directly from the ambient air (direct air capture) is also possible.

[0047] It is particularly advantageous if the reaction mixture is circulated through the reactor module during the catalytic reaction. This ensures that the mixture of starting materials and final product is continuously mixed, ensuring that the catalyst is constantly supplied with starting materials and the membrane is constantly supplied with water to ensure an efficient reaction. In this sense, it is also advantageous if the reactor has at least one circuit with at least one feed pump for transporting a liquid and / or gaseous mixture along the circuit, that the reactor module is part of the circuit, and that the carbon dioxide source and the alcohol source are preferably fluidly connected to the circuit.

[0048] To achieve a particularly efficient conversion, the reaction mixture can be circulated through several reactor modules connected in parallel during the catalytic reaction. By connecting the reactor modules in parallel, the amount of reacted starting substances can be further increased. This is particularly advantageous in a discontinuous process. The same applies if the circuit comprises several reactor modules connected in parallel. Alternatively, several reactor modules can be connected in series. This allows a higher concentration to be achieved.

[0049] It can also be provided that several circuits are connected in series, with at least a first and second circuit each having at least one reactor module. In other words, it can be provided that the reaction mixture, after being guided in a first circuit, is at least partially guided in a second circuit, with the reaction mixture being guided through at least one further reactor module during the course of being guided through the second circuit. It can be provided that different reaction equilibria are established in the circuits. This can be particularly useful when the process is carried out continuously.

[0050] Preferably, the catalytic reaction is carried out until the reaction mixture has a threshold weight fraction of end product, preferably at least 80% by weight, and that upon or after reaching the threshold weight fraction, the reaction mixture is discharged from the reactor module. After discharge, preferably carbon dioxide, the alcohol, or at least one other substance is separated from the organic carbonate as the end product. Such a discontinuous reaction regime quickly achieves a high degree of conversion. The reaction mixture can be recirculated until the threshold weight fraction is reached.In this sense, it can also be advantageous if carbon dioxide is separated from the reaction mixture after or during discharge, preferably via a droplet separator, and / or if the alcohol and / or other substances are separated from the reaction mixture, particularly preferably via distillation and / or via at least one membrane. Accordingly, it is also advantageous if the circuit has at least one discharge channel leading from the circuit for discharging end product, and if the discharge channel preferably comprises at least one condenser and / or at least one droplet separator, and particularly preferably a carbon dioxide return channel for returning carbon dioxide from the droplet separator to the circuit.

[0051] The separated substance or substances can be returned to the cycle. It can therefore be provided that at least one return channel is provided for the respective substance to be returned to the cycle. The substance, i.e., carbon dioxide or alcohol, can be pretreated before being returned, for example, by compression, heating, cooling, or purification.

[0052] It is also advantageous if, after the discharge, carbon dioxide and alcohol are fed into the reactor and another catalytic reaction is carried out. This can then initiate a new reaction.

[0053] In order to prevent excessive stress on the membrane, it can be provided that during the catalytic reaction a pressure is set on the side of the membrane facing away from the reaction mixture which deviates from the pressure of the reaction mixture by less than 10 bar, preferably less than 6 bar. It is also advantageous if a sweep gas flows past the side of the membrane facing away from the reaction mixture, the sweep gas preferably being carbon dioxide. The flow of the sweep gas drives the water that escapes from the membrane and away from the membrane surface, which improves water separation. The pressure on this side of the membrane can be adjusted via the sweep gas. Alternatively, nitrogen (N2), ethanol vapor or gas mixtures, preferably gas mixtures of the gases mentioned, such as a CC -ethanol vapor mixture, can also be used as the sweep gas.

[0054] It is particularly advantageous if, prior to the catalytic reaction, the catalyst is immobilized on a molecular sieve, preferably by applying a cerium salt, particularly preferably a cerium halogen salt such as cerium chloride and / or cerium(III) nitrate, to the molecular sieve, and then calcining the molecular sieve. This achieves a particularly large catalyst surface area, as described above. The same applies if the reaction space is substantially filled with a molecular sieve and the catalyst immobilized thereon.

[0055] Preferably, the membrane is designed as at least one membrane tube, inside which at least part of the discharge chamber is located. The tubular design allows for efficient water removal by means of sweep gas. Accordingly, it can also be provided that water produced during the catalytic reaction is separated via at least one membrane designed as at least one membrane tube.

[0056] It is particularly advantageous if the membrane has a selectivity of at least 100 to water at a temperature of 80°C and a pressure of 5 bar and / or a selectivity of at least 100 to water at a temperature of 100°C and a pressure of 10 bar. This allows for the purest possible separation of water. A selectivity of 100 to water means that the membrane allows only 1 part of ethanol to pass through 100 parts of water.

[0057] Furthermore, in order to adjust the temperature for the catalytic reaction, it can be provided that the circuit has at least one temperature control source for adjusting the temperature of the mixture in the circuit and / or the temperature of the mixture in the circuit is adjusted via at least one temperature control source.

[0058] In a preferred embodiment, the reactor module has an inlet fluidically connected to the reaction chamber, which is connected to a feed channel of the circuit, and an outlet, preferably located at the opposite end of the reaction chamber, which is connected to a retentate channel of the circuit. In addition to the connection via the reactor module, the feed channel and the retentate channel are also directly or indirectly connected to each other, thus creating a circuit.

[0059] It is particularly advantageous if at least one membrane tube extends into the reaction chamber, preferably extending from one end of the reaction chamber to the other. This allows water to be removed from the reaction chamber over the entire length of the reaction chamber, and the small amount of water throughout the entire reaction chamber converts a particularly large amount of starting substances into organic carbonate.

[0060] It is further advantageous if the membrane tube is fluidly connected to a sweep gas source in the region of a first end and to a water drainage channel for removing the water in the region of a second end. This achieves particularly efficient water removal.

[0061] In this sense, the first end can be closed, and the flow connection to the sweep gas source can be established via a dip tube that extends into the membrane tube via the second end. This allows the connections for the sweep gas to be located on one side of the reaction chamber. Furthermore, it makes it possible to use membrane tubes that are already industrially manufactured with one side closed.

[0062] For efficient separation of the water, it can be provided that the water discharge channel has a droplet separator for separating sweep gas, preferably a condenser upstream of the droplet separator and / or a sweep gas return line for returning the obtained sweep gas into the membrane tube.

[0063] The sweep gas can be, for example, carbon dioxide. Even if some of it were to enter the reaction chamber through the membrane, it would not contaminate the mixture there. Alternatively, another gas, such as nitrogen (N2), ethanol vapor, or gas mixtures, preferably gas mixtures of the aforementioned gases, such as a CO2-ethanol vapor mixture, can be used.

[0064] The separation of water is further improved if at least five, preferably six or seven membrane tubes are arranged in the reactor module.

[0065] The invention will now be described with reference to non-limiting embodiments of the invention in the figures. They show: Fig. 1a shows a reactor module according to the invention for installation in a reactor according to the invention and for carrying out a process according to the invention in a longitudinal section;

[0066] Fig. lb shows a section through the reactor module of Fig. la along the line AA;

[0067] Fig. 2 is a flow diagram of a reactor according to the invention using a process according to the invention in a first embodiment.

[0068] The reactor module 1 shown in Fig. 1a and Fig. 1b has an elongated, essentially cylindrical shape. At one end there is an inlet region 2 which has a connection 2a for connection to a feed channel. This supplies the reactor module with carbon dioxide and alcohol. The inlet region 2 is connected via an inlet 3 to a first end 4a of the reaction chamber 4, which is filled with molecular sieve (not shown) in pellet form and the catalyst calcined thereon, so that the starting materials can be converted into organic carbonate by the catalyst in the reaction chamber 4. The reaction chamber 4 extends over the majority of the reactor module 1; for better visibility, the reactor module 1 is shown interrupted in the region of the reaction chamber 4.

[0069] The reaction chamber 4 is fluidly connected to an outlet region 6 at its opposite second end 4b via an outlet 5. The outlet region 6 has a connection 6a for connection to a retentate channel. Thus, the retentate, which comprises the final product, optionally mixed with the starting substances that have not been reacted, can be discharged from the reaction chamber 4.

[0070] A total of seven membrane tubes 7 extend along the longitudinal extent of the reaction chamber 4, extending through an end wall 8 of the outlet region 6 into the outlet region 6 and further into the reaction chamber 4 to the first end 4a. The end wall 8 is tightly connected to the membrane tubes 7. The membrane tubes 7 terminate in a water collection region 9 located behind the end wall 9. The outer walls of the membrane tubes 7 thus face the reaction chamber 4, while the inner walls of the membrane tubes 7 face a discharge chamber 10 formed from the interior spaces of the membrane tubes 7 and which is free of catalyst.

[0071] At a second end 7b of the membrane tubes 7, these are open and in flow connection with the water collection area 9. Water that penetrates from the reaction chamber 4 into the discharge chamber 10 via the membrane tubes 7 can thus be collected in the water collection area 9 and discharged into a discharge channel via a connection 9a of the water collection area 9.

[0072] At a first end 7a, the end facing the first end 4a of the reaction chamber 4, the membrane tubes 7 are closed. Immersion tubes 11 are inserted into the membrane tubes 7 via the second end 7b, extending to the first end 7a and open there. Sweep gas can thus be brought via the immersion tubes 11 into the discharge chamber 10 in the area of ​​the first end 7a. The immersion tubes 11 limit the discharge chamber 10 to the narrow area between the outside of the immersion tubes 11 and the inside of the membrane tubes 7.

[0073] The dip tubes 11 extend from the second end 7b further through the water collection area 9 and through another end wall 12 of the reactor module 1, which end wall 12 is also tightly connected to the dip tubes 11. Beyond the end wall 12, the dip tubes 11 are fluidly connected to a sweep gas source.

[0074] In Fig. 2, an embodiment of a reactor according to the invention is explained in more detail using a flow diagram. The reactor comprises a reactor module 20 having a membrane 21 separating a reaction chamber 4 from a discharge chamber 10. The reaction chamber 4 is part of a circuit 22 having a circulation pump 23 that moves its fluid in one direction. The circuit 22 can have channels, such as pipes, for guiding the fluid. The membrane 21 comprises at least one inorganic membrane and / or at least one hybrid membrane.

[0075] The reaction chamber is connected via an inlet to a feed channel 29 of circuit 22 downstream of the circulation pump 23, and via an outlet to a retentate channel 30 upstream of the circulation pump 23. "Connected" in this sense refers to flow connections. The circulation pump 23 thus acts as a feed pump.

[0076] Fig. 2 shows only one reactor module 20. However, as already explained, it can also be provided that the feed channel 29 branches upstream of the reactor module and supplies several reactor modules 20 in parallel. Accordingly, the retant channel 30 would then also branch out accordingly, collecting the reaction mixture from the reactor modules and converging it into a single channel upstream of the circulation pump 23.

[0077] Furthermore, an ethanol supply line 24 is connected to the circuit 22, via which ethanol is fed into the circuit from an ethanol tank 25 and by a feed pump. Preferably, the supply line 24—as shown in this embodiment—is arranged downstream of the circuit pump 23 and upstream of the reactor module 20.

[0078] Furthermore, a supply line 26 for carbon dioxide (CO2) is connected to the circuit 22, via which CO2 is fed into the circuit from a carbon dioxide tank 27 and, if necessary, another feed pump. Preferably, the supply line 26—as shown in this embodiment—is arranged downstream of the circuit pump 23 and upstream of the reactor module 20.

[0079] The circuit 22 is also connected to a discharge channel 28 between the reaction chamber 4 and the circuit pump 23, via which retentate can be discharged into a retentate tank 31.

[0080] The discharge chamber 10 is connected to a carbon dioxide source, preferably the same carbon dioxide tank 27, via another supply line 35. Thus, the CO2 in the discharge chamber 10 acts as a sweep gas and carries the water away from the membrane 21.

[0081] The discharge chamber 10 is connected to a water discharge channel 32, through which water can be discharged from the discharge chamber 10 and directed into a water tank 34. The water discharge channel 32 preferably has a condenser 33, through which the water is condensed before being introduced into the water tank 34.

[0082] The reactor module 20 is preferably temperature-controlled, particularly preferably via a temperature-control fluid such as an oil, which is guided to and from the reactor module 20 via temperature-control channels 36.

Claims

PATENT CLAIMS 1. A process for the production of organic carbonates, in particular diethyl carbonate, comprising a catalytic reaction of corresponding alcohols (ROH) with carbon dioxide, where R is a straight-chain or branched-chain alkyl radical having 1-6 carbon atoms, preferably an ethyl radical, and where water formed during the catalytic reaction is separated off via at least one inorganic membrane (21) and / or at least one hybrid membrane (21), characterized in that the catalytic reaction is carried out at a temperature of at least 80°C and at a pressure of at least 5 bar and in that the catalyst comprises at least one of the substances mentioned: cerium oxide (CeO2), ZrO2, CrO2, Fe, Cu, Mg, Ni, SiO2, Al2O3, TiO, MoO, BiO, ZnO, Ta2O5, Nb2O5 or an alloy comprising copper and nickel.

2. Process according to claim 1, characterized in that the reaction is carried out at at least 100°C, preferably at least 120°C and particularly preferably between 110°C and 150°C, and / or that the reaction is carried out at at least 10 bar, preferably at a pressure between 20 bar and 40 bar.

3. Method according to claim 1 or 2, characterized in that the separation via the membrane (31) takes place by means of membrane pervaporation and / or vapor permeation.

4. The method according to any one of claims 1 to 3, characterized in that the separation takes place via at least one carbon membrane and / or at least one ceramic membrane, particularly preferably at least one zeolite membrane and / or that the separation takes place via at least one membrane which has at least one at least predominantly inorganic and / or at least one at least predominantly organic layer.

5. The method according to any one of claims 1 to 4, characterized in that the catalytic reaction is carried out in at least one reactor module (20) in which the catalyst is arranged and that preferably the reaction space (4) is separated by at least one inorganic membrane (21) and / or at least one hybrid membrane (21) from a discharge space (10) for discharging water from the reaction space (4).

6. The method according to claim 5, characterized in that during the catalytic reaction the reaction mixture is circulated (22) through the reactor module (20).

7. The method according to claim 6, characterized in that during the catalytic reaction the reaction mixture is circulated (22) through several reactor modules (20) connected in parallel.

8. The method according to any one of claims 1 to 7, characterized in that the catalytic reaction is carried out until the reaction mixture has a threshold weight fraction of end product, preferably at least 80% by weight, and that upon or after reaching the threshold weight fraction, the reaction mixture is discharged from the reactor module (20) and that after the discharge, preferably carbon dioxide, the alcohol or at least one other substance is separated from the organic carbonate as the end product.

9. The method according to claim 8, characterized in that after or during the discharge, carbon dioxide is separated from the reaction mixture and / or that the alcohol and / or other substances are separated from the reaction mixture, particularly preferably by distillation and / or by at least one membrane.

10. Process according to claim 8 or 9, characterized in that after the discharge, carbon dioxide and alcohol are fed into the reactor and a further catalytic reaction is carried out.

11. Method according to one of claims 1 to 10, characterized in that during the catalytic reaction on the side of the membrane (21) facing away from the reaction mixture, a pressure is set which deviates from the pressure of the reaction mixture by less than 10 bar, preferably less than 6 bar.

12. Method according to one of claims 1 to 11, characterized in that a sweep gas flows past the side of the membrane (21) facing away from the reaction mixture, the sweep gas preferably being carbon dioxide.

13. The process according to any one of claims 1 to 12, characterized in that prior to the catalytic reaction, the catalyst is immobilized on a molecular sieve and preferably a cerium salt, particularly preferably a cerium halogen salt such as cerium chloride and / or cerium(III) nitrate, is applied to the molecular sieve and the molecular sieve is subsequently calcined.

14. Method according to one of claims 1 to 13, characterized in that the water is separated via the membrane (21) directly after its formation during the catalytic reaction.

15. Reactor for producing organic carbonates, in particular diethyl carbonate, wherein the reactor has at least one reactor module (20), and the reactor module (20) has a reaction chamber (4), wherein the reaction chamber (4) is separated from a discharge chamber (10) for discharging water from the reaction chamber (4) by at least one inorganic membrane (21) and / or at least one hybrid membrane (21), characterized in that a catalyst is arranged in the reaction chamber (4) and that the catalyst comprises at least one of the substances mentioned: cerium oxide (CeO2), ZrO2, CrO2, Fe, Cu, Mg, Ni, SiO2, Al2O3, TiO, MoO, BiO, ZnO, Ta2O5, Nb2O5 or an alloy comprising copper and nickel.

16. Reactor according to claim 15, characterized in that the membrane (20) comprises a carbon membrane and / or a ceramic membrane, particularly preferably a zeolite membrane and / or that the membrane has at least one at least predominantly inorganic and / or at least one at least predominantly organic layer.

17. Reactor according to claim 15 or 16, characterized in that the reactor comprises at least one carbon dioxide source and at least one alcohol source (ROH), where R is a straight- or branched-chain alkyl radical having 1-6 carbon atoms, preferably ethyl alcohol.

18. Reactor according to one of claims 15 to 17, characterized in that the reactor has at least one circuit (22) with at least one feed pump for transporting a liquid and / or gaseous mixture along the circuit (22), that the reactor module (20) is part of the circuit (22) and that preferably the carbon dioxide source and the alcohol source are fluidly connected to the circuit (22).

19. Reactor according to claim 18, characterized in that the circuit (22) comprises several reactor modules (20) which are connected in parallel to one another.

20. Reactor according to one of claims 15 to 19, characterized in that the membrane (21) is designed as at least one membrane tube (7), in the interior of which at least part of the discharge space is located.

21. Reactor according to one of claims 15 to 20, characterized in that the membrane (21) has a selectivity o to water of at least 100 at a temperature of 80°C and a pressure of 5 bar and / or a selectivity o to water of at least 100 at a temperature of 100°C and a pressure of 10 bar.

22. Reactor according to one of claims 18 to 21, characterized in that the circuit (22) has at least one temperature control source for adjusting the temperature of the mixture in the circuit (22).

23. Reactor according to one of claims 18 to 22, characterized in that the circuit (22) has at least one discharge channel (28) leading from the circuit (22) for discharging end product.

24. Reactor according to one of claims 15 to 23, characterized in that the reactor module (20) has an inlet (3) which is fluidly connected to the reaction chamber (4) and is connected to a feed channel (29) of the circuit (22), and has an outlet (5), preferably arranged at the opposite end of the reaction chamber (4), which is connected to a retentate channel (30) of the circuit (22).

25. Reactor according to one of claims 15 to 24, characterized in that at least one membrane tube (7) projects into the reaction chamber (4) and preferably extends from one end of the reaction chamber (4) to the other end of the reaction chamber (4).

26. Reactor according to claim 25, characterized in that the membrane tube (7) is fluidly connected to a sweep gas source in the region of a first end (7a) and the membrane tube (7) is fluidly connected to a water discharge channel (32) for discharging the water in the region of a second end (7b).

27. Reactor according to claim 26, characterized in that the first end (7a) is closed and the flow connection to the sweep gas source is made via a dip tube (11) which projects into the membrane tube (7) via the second end (7b).

28. Reactor according to one of claims 25 to 27, characterized in that at least five, preferably six membrane tubes (7) are arranged in the reactor module (20).

29. Reactor according to one of claims 15 to 28, characterized in that the reaction space (4) is essentially filled with a molecular sieve and the catalyst immobilized thereon.

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