Membrane reactor method and device for ammonia synthesis

Abstract

The invention relates to an ammonia synthesis membrane reactor method and device. The device comprises a raw material mixer, a preheater, a pre-reactor, a membrane reactor, a condenser, a product storage tank and other units. The method is characterized in that a membrane reactor and a pre-reactor are connected and have the same temperature and pressure, so that excessive energy consumption caused by temperature rise and temperature reduction is avoided, the pre-reactor and the membrane reactor reduce the pressure of synthesis ammonia to 0.1-10 MPa and the temperature to 150-400 DEG C through the strengthening effect of a membrane element, and the membrane element has the capability of selectively permeating ammonia under reaction conditions. The membrane reactor can break reaction equilibrium limitation, greatly improve the conversion per pass, reduce the reaction temperature and pressure, avoid temperature and pressure reduction, temperature and pressure rise and the like in the production process and reduce power equipment such as a heat exchanger and a mechanical compression pump, has the advantages of short flow, quick start and stop, high operation flexibility, low energy consumption, high efficiency and the like, is easily coupled with the green hydrogen production process, and is suitable for industrial production. And the method is suitable for application scenes of distributed ammonia synthesis.

Description

Technical Field

[0001] The present invention relates to ammonia synthesis and separation of ammonia / hydrogen mixed gas, in particular to an ammonia synthesis membrane reactor, and specifically to an ammonia synthesis membrane reactor and an energy-saving novel ammonia synthesis-separation device. Background Art

[0002] Ammonia is not only an important chemical raw material and agricultural fertilizer, but also a crucial carrier of green hydrogen. Existing ammonia synthesis processes all utilize the Haber-Bosch process, requiring industrial production at high temperatures (>450°C) and high pressures (>12 MPa). Even under these conditions, the single-pass H2 conversion rate is less than 15% due to thermodynamic and kinetic equilibrium limitations. In addition to low single-pass conversion rates, existing ammonia synthesis processes also present complex processes and high energy consumption. For example, to separate approximately 85% of unreacted H2 and N2 from the ammonia product, the high-temperature, high-pressure reaction and product mixture must be cooled to -25°C and then reduced to near-ambient pressure to separate the NH3 product. The unreacted gas must then be reheated and repressurized to continue the reaction. This means that most gases must undergo four to seven cycles of heating, increasing pressure, and cooling, resulting in exceptionally high energy consumption in existing processes. Currently, the global energy consumption per ton of NH3 produced is approximately 1.2 tons of standard coal (TCE) for coal-based feedstock and 0.96 tons of TCE for natural gas-based feedstock. Ammonia synthesis alone consumes 1-2% of the world's energy and produces about 3% of carbon emissions.

[0003] Regarding the ammonia synthesis process, researchers have primarily focused on improving catalysts to appropriately lower reaction temperature and pressure. Zhang Ke et al. proposed a spin-mediated promotion mechanism and developed a cobalt catalyst capable of synthesizing ammonia at low pressure (0.1 MPa) (Science, 2024, 383:1357-1363). Hattori Masashi et al. reported a metallic iron particle with an electron donor material as an ammonia synthesis catalyst, capable of catalyzing ammonia synthesis at low temperatures (100°C) (Journal of the American Chemical Society 2023, 145:7888-7897). Despite numerous achievements in catalyst research, industrial application has yet to be achieved. More importantly, improvements in catalysts have not been able to overcome the low thermodynamic equilibrium of the ammonia synthesis reaction.

[0004] At present, some literature and patents have proposed the use of new separation technologies such as membrane separation and adsorption after the reaction to reduce the extent of cooling or pressure reduction after the reaction, thereby achieving the purpose of appropriately reducing energy consumption. Surya Padinjarekutt et al. studied and reported the addition of Na +The prepared gated nanochannel membrane was applied to a device for separating ternary mixtures of NH3 / H2 / N2 (Chemical Engineering Journal, 2023, 454:139998); Yuan Mukang et al., in their invention patent CN118162056A, constructed a low-energy synthetic ammonia production device using a hollow fiber membrane separator and an ammonia synthesis reactor. However, none of these improvements broke the thermodynamic and kinetic equilibrium of the reaction, did not significantly improve the single-pass H2 conversion rate, and the overall heating and pressure increase-cooling and pressure reduction process did not change significantly. Overall, energy consumption remained high after these small-scale improvements, and process complexity did not significantly improve.

[0005] Therefore, faced with the current difficulty in significantly reducing consumption in ammonia synthesis, there is an urgent need at home and abroad to develop a low-energy consumption ammonia synthesis device with a simple process to cope with future energy shortages and meet market demand. Summary of the Invention

[0006] The technical problem addressed by this invention is the low reaction efficiency and high energy consumption caused by heat exchange during the product separation process in existing ammonia synthesis processes. This invention proposes a novel, energy-saving ammonia synthesis method and apparatus based on a membrane reactor. By utilizing the membrane material to separate ammonia in situ during the reaction, this process avoids the need for cooling and decompressing units and reheating and pressurizing units in the main flowsheet, reducing the complexity of the production process while significantly reducing process energy consumption.

[0007] In another technical solution, the membrane elements can catalyze the reaction, significantly increasing the H2 per-pass conversion rate within the membrane reactor due to the selective separation of ammonia from the system, further reducing process energy consumption. This achieves energy conservation and consumption reduction in the ammonia synthesis process, fully meeting future market requirements for green and environmentally friendly chemical industry practices.

[0008] A membrane reactor method for ammonia synthesis comprises the following steps:

[0009] The synthesis gas composed of H2 and N2 is synthesized through ammonia pre-reaction and then directly fed into the ammonia permeable separation membrane for ammonia selective permeation separation without cooling;

[0010] The surface of the ammonia permeable separation membrane may or may not contain an ammonia synthesis catalyst, wherein the ammonia synthesis catalyst is used to catalyze the synthesis of ammonia from H2 and N2 in the synthesis gas;

[0011] The retentate side material of the ammonia separation membrane is returned to the ammonia pre-reaction synthesis process; the permeate side material is subjected to ammonia purification.

[0012] Ammonia can be purified by condensation, adsorption, absorption, washing, distillation, etc.

[0013] The product after the ammonia purification is liquid ammonia, ammonia water or ammonium salt compound.

[0014] During the ammonia pre-reaction synthesis process, the space velocity range is 10000-60000 ml·g -1 ·h -1 , 150-400℃, reaction pressure 0.1-10MPa; and the reaction raw materials are deoiled.

[0015] The ammonia permeable separation membrane is a self-supporting membrane or a composite membrane including a carrier. The material of the selective separation layer on the ammonia permeable separation membrane is selected from polymers or inorganic materials.

[0016] The polymer is selected from polyimide film, polyamide film, polyurethane film, polyethylene film, polytetrafluoroethylene film, polymethacrylic acid film, polybenzodioxane film, polybenzoxazole film, polysulfone film, polyethylene terephthalate film, polyetherimide film or polyethersulfone film;

[0017] The inorganic material is selected from molecular sieve membranes, ceramic membranes, metal membranes, transition metal chalcogenide membranes, two-dimensional transition metal carbide membranes, two-dimensional transition metal nitride membranes, layered double hydroxide membranes, hexagonal boron nitride membranes, mica nanosheet membranes, metal-organic framework membranes, carbon membranes or graphene membranes.

[0018] The molecular sieve membranes are SOD molecular sieve membranes, AEI molecular sieve membranes and CHA molecular sieve membranes, which are loaded on the carrier surface through in-situ synthesis or secondary synthesis methods, and the pore size is adjusted by adding cations during the synthesis. The separation layer of the ammonia separation membrane has a pore size of 0.26-0.28nm.

[0019] The cation is K + 、Ti 4+ , Rb + , Ca 2+ 、Sr 2+ 、Ag + 、Cu 2+ One or more of the .

[0020] The configuration of the ammonia permeable membrane is single tube, multi-channel, flat plate, hollow fiber or coil; the diameter of the gas cross-flow channel is 2-50 mm, the thickness of the ammonia permeable membrane is 0.1-20 μm, and the thickness of the catalyst layer can be 1-100 μm.

[0021] When the ammonia permeable separation membrane contains an ammonia synthesis catalyst, the catalyst is loaded in one of the following two ways or a combination of the two:

[0022] The first type: the surface of the ammonia separation membrane is also loaded with a catalyst layer, the thickness of the catalyst layer is 1-100 μm;

[0023] The second type: the ammonia synthesis catalyst is located in the cross-flow channel of a single-tube, multi-channel, flat-plate, hollow fiber or spiral ammonia separation membrane, which is partially or completely filled with the catalyst.

[0024] The main catalyst used in the ammonia synthesis catalyst layer is an iron-based catalyst, a molybdenum-based catalyst, a nickel-based catalyst, a cobalt-based catalyst, a platinum-based catalyst or a palladium-based catalyst; the sub-catalyst is a mixture of one or more of aluminum oxide, zirconium oxide and titanium oxide.

[0025] When the synthetic ammonia catalyst through the ammonia separation membrane performs the catalytic reaction, the space velocity range is 2000-15000 ml g -1 ·h -1 , pressure is 0.1-10MPa.

[0026] An ammonia synthesis membrane reaction device, comprising:

[0027] A circulating pre-reactor for synthesizing ammonia by pre-reaction of synthesis gas composed of H2 and N2;

[0028] An ammonia permeable separation membrane is connected to the outlet of the circulating pre-reactor and is used for permeation separation of ammonia; and the surface of the ammonia permeable separation membrane may or may not contain an ammonia synthesis catalyst, and the ammonia synthesis catalyst is used to catalyze the synthesis of ammonia from H2 and N2 in the synthesis gas;

[0029] A liquefaction separator connected to the permeate outlet of the ammonia membrane is used to purify ammonia from the permeate gas;

[0030] When the circulating pre-reactor is connected to the ammonia permeable membrane, no cooling equipment is included.

[0031] The separation layer of the ammonia separation membrane has a separation factor of greater than 3 for NH3 / H2 and greater than 3 for NH3 / N2.

[0032] The ammonia permeable separation membrane is a self-supporting membrane or a composite membrane including a carrier. The material of the selective separation layer on the ammonia permeable separation membrane is selected from polymers or inorganic materials.

[0033] The polymer is selected from polyimide film, polyamide film, polyurethane film, polyethylene film, polytetrafluoroethylene film, polymethacrylic acid film, polybenzodioxane film, polybenzoxazole film, polysulfone film, polyethylene terephthalate film, polyetherimide film or polyethersulfone film;

[0034] The inorganic material is selected from molecular sieve membranes, ceramic membranes, metal membranes, transition metal chalcogenide membranes, two-dimensional transition metal carbide membranes, two-dimensional transition metal nitride membranes, layered double hydroxide membranes, hexagonal boron nitride membranes, mica nanosheet membranes, metal-organic framework membranes, carbon membranes or graphene membranes.

[0035] The configuration of the ammonia separation membrane is single-tube, multi-channel, flat-plate, hollow fiber or coiled; the diameter of the gas cross-flow channel is 2-50 mm, the ammonia separation membrane adopts a composite membrane containing a carrier, and the thickness of the separation layer is selected to be 0.1-20 μm, and the thickness of the catalyst layer can be 1-100 μm.

[0036] The molecular sieve membranes are SOD molecular sieve membranes, AEI molecular sieve membranes and CHA molecular sieve membranes, which are loaded on the surface of a carrier through in-situ synthesis or secondary synthesis, and the pore size is adjusted by adding cations during the synthesis.

[0037] The cation is K + 、Ti 4+ , Rb + , Ca 2+ 、Sr 2+ 、Ag + 、Cu 2+ One or more of the .

[0038] When the surface of the ammonia permeable separation membrane contains an ammonia synthesis catalyst, the catalyst is loaded in one of the following two ways or a combination of the two:

[0039] The first type: the surface of the ammonia separation membrane is also loaded with a catalyst layer, the thickness of the catalyst layer is 1-100 μm;

[0040] The second type: the ammonia synthesis catalyst is located in the cross-flow channel of a single-tube, multi-channel, flat-plate, hollow fiber or spiral ammonia separation membrane, which is partially or completely filled with the catalyst.

[0041] When connecting the circulating pre-reactor and the ammonia synthesis membrane reactor, no cooling equipment is included.

[0042] Also included: a raw material mixer for mixing H2 and N2.

[0043] It also includes: a multi-stage compressor connected to the feed port of the circulating pre-reactor, used to pressurize the synthesis gas composed of H2 and N2 entering the circulating pre-reactor 5.

[0044] Beneficial effects

[0045] The ammonia synthesis membrane reactor provided by the present invention can control the reaction temperature and membrane separation temperature to be the same, reducing the temperature to the range of 200-350°C and the pressure to 0.1-10 MPa. Because membrane separation does not involve thermal changes or phase transitions, overall process energy consumption is minimized. The ammonia-permeable membrane reactor can break the reaction equilibrium, improve the single-pass conversion rate, appropriately reduce the reaction temperature and pressure, and significantly reduce energy consumption through process intensification.

[0046] The present invention significantly improves the reaction conversion rate while optimizing the operating conditions through the coupling effect of reaction and separation in the membrane reactor. The equipment has a simple structure and is easy to operate. The effective circulation process of the materials extracted from the permeate side and the retentate side of the membrane reactor ensures the continuity and economy of the operation of the present invention. By reducing the load of the multi-stage compressor, the energy consumption required for the compression process is greatly reduced while the cooling water consumption is greatly reduced. In general, the present invention has shown good results in the direction of ammonia synthesis. Theoretically, the H2 single-pass conversion rate is about 35% (an increase of about 20%), and the operating energy consumption is saved by 60% to 70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The diagram is a schematic diagram of the membrane pores and structure of the membrane assembly and the catalytic membrane in the ammonia synthesis membrane reactor of the present invention.

[0048] Figure 2 This is a flow chart of an ammonia synthesis device based on a membrane reactor according to the present invention.

[0049] Figure 3 1 is a process flow chart of a comparative example (Haber-Bosch method) of an embodiment of the present invention.

[0050] 1. Raw material inlet; 2. Pressure-resistant sealing gasket; 3. Ammonia separation membrane; 4. Permeate side outlet; 5. Retentate side outlet; 6. Catalytic membrane layer; 7. Catalyst supporting layer.

[0051] 8. Raw material mixer; 9. Multi-stage compressor; 10. Deoiler; 11. Raw material temperature controller; 12. Circulating pre-reactor; 13. Circulating compressor; 14. Ammonia synthesis membrane reactor; 15. Liquefaction separator; 16. Ammonia product tank.

[0052] 17. Feed multi-stage compressor; 18. Oil remover; 19. Raw material temperature controller; 20. Ammonia synthesis tower; 21. Cooling tower; 22. Low-temperature separator; 23. Liquid nitrogen storage tank; 24. Circulating compressor. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with comparative examples and Example 1, Example 2, and Example 3 and Comparative Example 1, but the protection scope of the present invention is not limited thereto.

[0054] like Figure 3The comparative example employed the Haber-Bosch process, a conventional ammonia synthesis process in the chemical industry, comprising a feed multi-stage compressor 17, an ammonia synthesis tower 20, and other equipment. The multi-stage compressor 17 was connected to the inlet of an oil remover 18; the inlet of the oil remover 18 was connected to the multi-stage compressor 17, and the outlet was connected to the inlet of a raw material temperature controller 19; the outlet of the raw material temperature controller 19 was connected to the feed inlet of the ammonia synthesis tower 20; the feed inlet of the ammonia synthesis tower 20 was connected to the outlet of the raw material temperature controller 19; the ammonia synthesis tower 20 was provided with a refrigerant inlet and outlet; the discharge of the ammonia synthesis tower 20 was connected to the inlet of a cooling tower 21; the inlet of the cooling tower 21 was connected to the discharge of the ammonia synthesis tower 20, and the outlet was connected to the inlet of a low-temperature separator 22; the inlet of the low-temperature separator 22 was connected to the outlet of the cooling tower 21; the liquid phase outlet was connected to the inlet of a liquid nitrogen storage tank 23; and the gas phase outlet was connected to a circulating compressor 24; the inlet of the liquid nitrogen storage tank 23 was connected to the outlet of the low-temperature separator 22, and the liquid phase was extracted or transported internally.

[0055] like Figure 1 The present invention provides an ammonia synthesis membrane reactor, comprising an ammonia permeable separation membrane and a membrane assembly. The membrane assembly is provided with a feedstock inlet 1, an ammonia synthesis membrane reactor permeate outlet 4, and an ammonia synthesis membrane reactor retentate outlet 5. The ammonia permeable separation membrane is used to separate ammonia from a reaction mixture containing H2, N2, and NH3, allowing NH3 to permeate and separate it from H2 and N2. After the catalytic synthesis of H2 and N2, the reaction product material should enter the ammonia permeable separation membrane 3 directly for selective separation without cooling, thereby avoiding energy loss caused by cooling. In actual chemical processes, "not cooling" generally refers to not undergoing a cooling step using a heat exchanger, and natural heat loss in equipment and pipelines does not fall within the scope of the cooling step. The ammonia permeable separation membrane can be installed either inside the ammonia pre-synthesis reactor or outside the pre-synthesis reactor and connected by a pipeline. The specific installation location is not limited. In addition, the configuration of the ammonia permeable membrane element here can be single-tube, multi-channel, flat-plate, hollow fiber or coiled, etc., and the ammonia permeable separation membrane can be in the form of an inner membrane or an outer membrane.

[0056] In some other embodiments, the ammonia permeable separation membrane may also include an ammonia synthesis catalyst, which is used to achieve the synchronous reaction and selective separation of ammonia in the membrane reaction process. The catalyst here can be located on the surface of the separation layer. The catalyst can be loaded as a catalyst layer coated and loaded on the surface of the molecular sieve membrane selective separation layer, which has a certain thickness. It can also be a granular, integrated loaded catalyst with a fixed morphology, which is loaded on the surface of specific particles or an integrated porous carrier, and this fixed morphology loaded catalyst is placed on the outside of the molecular sieve membrane selective separation layer. In particular, when a single-tube or multi-channel configuration is adopted and an inner membrane method is used, the loaded catalyst is placed / filled in the pipe of the membrane element, which can achieve catalytic synthesis of ammonia containing H2 and N2. The filling amount inside the channel can be partial filling or full filling. In this case, the initial H2 and N2 raw materials can undergo a pre-reaction before entering the catalytic membrane to continue catalytic synthesis of ammonia on the supported catalyst or catalyst layer coating, and then simultaneously pass through the molecular sieve membrane selective separation layer adjacent to the catalyst for real-time NH3 separation. In this case, the entire membrane reactor can include a pre-reactor for preliminary ammonia synthesis, and the synthesis product gas can be continuously fed into the membrane reactor without cooling to continue catalytic reaction on the surface of the molecular sieve membrane element and NH3 separation. Alternatively, the synthesis gas composed of H2 and N2 can be directly fed into the membrane element for catalysis and separation. The catalytic membrane in the membrane assembly is sealed at both ends using a pressure-resistant sealing gasket 2.

[0057] In one embodiment, Figure 2 The present invention provides an ammonia synthesis device based on an ammonia membrane reactor, which includes a raw material mixer, a multi-stage compressor, an ammonia synthesis membrane reactor and other equipment. The inlet of the raw material mixer 8 is connected to the source of N2 raw material and H2 raw material respectively; the inlet of the multi-stage compressor 9 is connected to the outlet of the raw material mixer 8, and the outlet is connected to the inlet of the deoiler 10; the inlet of the deoiler 10 is connected to the outlet of the multi-stage compressor 9, and the outlet is connected to the inlet of the raw material temperature controller 11; the inlet of the raw material temperature controller 11 is connected to the outlet of the deoiler 10, and the discharge port is connected to the circulating pre-reactor 12; the inlet of the circulating pre-reactor 12 is connected to the outlet of the raw material temperature controller 11, and the outlet is connected to the feed port of the ammonia synthesis membrane reactor 14; the feed port of the ammonia synthesis membrane reactor 14 is connected to the discharge port of the pre-reactor 12, the permeate side outlet is connected to the inlet of the liquefaction separator 15, and the retentate side outlet is connected to the inlet of the circulating compressor 13; the inlet of the liquefaction separator 15 is connected to the permeate side outlet of the ammonia synthesis membrane reactor 14, the gas phase outlet is connected to the raw material mixer 8, and the liquid phase outlet is connected to the inlet of the ammonia product tank 16; the inlet of the ammonia product tank 16 is connected to the liquid phase outlet of the liquefaction separator 15, and the outlet is produced or internally transported.

[0058] In this patent, the use of an ammonia permeable separation membrane is capable of separating the products in the synthesis of ammonia, allowing ammonia to pass through the membrane, while hydrogen and nitrogen are retained. The "permeation" in the present invention does not mean complete permeation, but can have a certain permeability. For the separation of mixed gases of NH3 (kinetic diameter 0.26nm (Applied Chemistry, 2020, 37(1):1-15)), H2 (kinetic diameter 0.28nm), and N2 (kinetic diameter 0.374nm), for the preferred and pore-modified molecular sieve membrane, the pore size is 0.26-0.28nm, which is between the kinetic diameters of ammonia and hydrogen (nitrogen) molecules, so that the molecular sieve membrane has a good screening effect on ammonia. For polymer membranes, separation is achieved by dissolution and diffusion of ammonia molecules. The ammonia permeable separation membrane material herein should have a separation factor for NH3 / H2 greater than 3, greater than 10, greater than 20, greater than 50, greater than 100, greater than 150, greater than 200, greater than 250, greater than 300 or greater than 500, and also have a separation factor for NH3 / N2 greater than 3, greater than 10, greater than 20, greater than 50, greater than 100, greater than 150, greater than 200, greater than 250, greater than 300 or greater than 500.

[0059] The ammonia permeable separation membrane that can be used in the present invention can be a self-supporting membrane or a composite membrane including a carrier.

[0060] The material of the selective separation layer on the ammonia permeable separation membrane is selected from polymers or inorganic materials.

[0061] Among the above polymer materials, specifically polyimide film, polyamide film, polyurethane film, polyethylene film, polytetrafluoroethylene film, polymethacrylic acid film, polybenzodioxane film, polybenzoxazole film, polysulfone film, polyethylene terephthalate film, polyetherimide film or polyethersulfone film can be used; among the above inorganic materials, specifically molecular sieve membrane, ceramic membrane, metal membrane, transition metal chalcogenide membrane, two-dimensional transition metal carbide membrane, two-dimensional transition metal nitride membrane, layered double hydroxide membrane, hexagonal boron nitride membrane, mica nanosheet membrane, metal-organic framework membrane, carbon film or graphene membrane can be used as an example.

[0062] In particular, the molecular sieve membrane has the ability to work under higher temperature conditions, which can separate ammonia in the process of ammonia synthesis without cooling, thus breaking the reaction kinetic equilibrium. The molecular sieve membrane used here can be a mixture of cations with different ionic radii (K + / Ti 4+ / Rb + / Ca 2+ / Sr 2+ / Ag + / Cu 2+By regulating the molecular sieve pores at the sub-angstrom level (e.g., by using a molecule sieve pore size control method), molecular sieve membrane materials with pore sizes of 0.26-0.28 nm can be obtained. Furthermore, the molecular sieve membrane's preferential adsorption of NH3 makes it highly effective in screening ammonia. The pore size can be controlled by adding the aforementioned cations to the sol during the synthesis of the molecular sieve membrane, thereby preparing molecular sieve membranes (such as SOD molecular sieve membranes, AEI molecular sieve membranes, and CHA molecular sieve membranes) through in situ synthesis.

[0063] The molecular sieve membrane can be a layer of molecular sieve membrane supported on a conventional ceramic support, which exhibits good high-temperature resistance and mechanical strength. The ceramic support can be single-tube, multi-channel, or flat-plate. A multi-channel support is preferred. In the case of a single-tube or multi-channel support, the diameter of the gas cross-flow channel can be 2-50 mm, and the molecular sieve membrane thickness can be 0.1-20 μm.

[0064] In some embodiments, in this patent, by fully loading the ruthenium-based catalyst into the SOD molecular sieve membrane layer or powder, it can be used as a catalyst for filling the pre-reactor bed and a multi-channel catalytic membrane for a membrane reactor.

[0065] For the circulating pre-reactor, the molecular sieve (SOD) powder loaded with ruthenium-based catalyst is granulated through extrusion and shaping, and evenly filled into the pre-reactor.

[0066] For membrane reactors and devices, a catalyst layer is loaded onto the surface of the molecular sieve membrane. The catalyst layer can be 1-100 μm thick. The primary catalyst commonly used in ammonia synthesis processes can be iron-based catalysts, molybdenum-based catalysts, nickel-based catalysts, cobalt-based catalysts, platinum-based catalysts, or palladium-based catalysts. The secondary catalyst can be a mixture of one or more of aluminum oxide, zirconium oxide, and titanium oxide.

[0067] In some embodiments, the catalytic membrane element selectively permeating ammonia can catalyze the ammonia synthesis reaction and selectively permeate ammonia, with an NH3 / H2 selectivity >100.

[0068] In some embodiments, a multi-channel membrane structure is used. During the reaction and separation process, a multi-channel catalytic membrane is placed in a membrane reactor. The membrane reactor is provided with a feed inlet, a permeate side outlet and a retentate side outlet. The membrane tubes with catalytic function in the membrane reactor are arranged in a tube-in-tube manner. The membrane reactor and the pre-reactor are connected end to end. The temperature and pressure are kept the same or similar. The N2 and H2 raw materials (normal temperature and pressure) first enter the raw material mixer and are fully mixed and then sent to a multi-stage compressor to be compressed to a pressure of 0.1-10 MPa. After entering the deoiler for purification, they enter the preheater and are heated to 200-350°C. Ammonia synthesis pre-reaction is carried out in the pre-reactor; the outlet of the pre-reactor is connected to the inlet of the membrane reactor, and the mixture after the reaction in the pre-reactor enters the membrane reactor for the next stage of reaction and membrane separation; after sufficient reaction and separation, a mixture of higher-purity NH3 and a small amount of H2 and N2 is collected on the permeate side, and after further purification in the condenser, the liquefied ammonia at the lower end of the condenser is sent to the product ammonia storage tank, and the gas at the upper end of the condenser is compressed and sent to the pre-reactor to complete the cyclic reaction process; the retentate side collects a mixture mainly composed of H2 and N2, and after pressure replenishment by the retentate side circulating compressor, it is sent to the pre-reactor to complete the cyclic reaction process.

[0069] In some embodiments, in the above low-temperature, low-pressure ammonia synthesis membrane reactor device, the operating temperature range of the circulating pre-reactor and the membrane reactor is 150-400°C, preferably 200-350°C, and the operating pressure of the circulating pre-reactor and the membrane reactor is 0.1-10 MPa, preferably 1-10 MPa; the space velocity in the pre-reactor can generally range from 10,000 to 60,000 ml·g -1 ·h -1 During the membrane reaction, the space velocity range can be 2000-15000 ml·g -1 ·h -1 The circulating pre-reactor and the membrane reactor are provided with inlets and outlets for cooling logistics to ensure the temperature stability of the ammonia synthesis reaction process.

[0070] Example 1:

[0071] Ammonia synthesis units based on ammonia membrane reactors, such as Figure 1 The present invention provides an ammonia synthesis membrane reactor, comprising a catalytic membrane and a membrane assembly. The membrane assembly is provided with a feedstock inlet 1, an ammonia synthesis membrane reactor permeate outlet 4, and an ammonia synthesis membrane reactor retentate outlet 5. The pores of the catalytic membrane element are primarily composed of a catalytic membrane layer 3 and a catalyst-supporting layer 7. The catalytic membrane in the membrane assembly is sealed at both ends with a pressure-resistant sealing gasket 2.

[0072] like Figure 2The present invention provides an ammonia synthesis device based on an ammonia membrane reactor, which includes a raw material mixer, a multi-stage compressor, an ammonia synthesis membrane reactor and other equipment. The inlet of the raw material mixer 1 is connected to the source of N2 raw material and H2 raw material respectively; the inlet of the multi-stage compressor 9 is connected to the outlet of the raw material mixer 8, and the outlet is connected to the inlet of the deoiler 10; the inlet of the deoiler 10 is connected to the outlet of the multi-stage compressor 9, and the outlet is connected to the inlet of the raw material temperature controller 11; the inlet of the raw material temperature controller 11 is connected to the outlet of the deoiler 10, and the discharge port is connected to the circulating pre-reactor 12; the inlet of the circulating pre-reactor 12 is connected to the outlet of the raw material temperature controller 11, and the outlet is connected to the feed port of the ammonia synthesis membrane reactor 14; the feed port of the ammonia synthesis membrane reactor 14 is connected to the discharge port of the pre-reactor 12, the permeate side outlet is connected to the inlet of the liquefaction separator 15, and the retentate side outlet is connected to the inlet of the circulating compressor 13; the inlet of the liquefaction separator 15 is connected to the permeate side outlet of the ammonia synthesis membrane reactor 14, the gas phase outlet is connected to the raw material mixer 8, and the liquid phase outlet is connected to the inlet of the ammonia product tank 16; the inlet of the ammonia product tank 16 is connected to the liquid phase outlet of the liquefaction separator 15, and the outlet is used for production or internal transportation.

[0073] The target output is to produce 1,000 tons (125 kg / h) of qualified ammonia products (ammonia content ≥ 99%) annually.

[0074] In the following example, the membrane reactor used uses a 61-channel ceramic membrane as a carrier, and a layer of SOD molecular sieve membrane (thickness of about 2μm) is loaded on the surface. During the in-situ synthesis of the SOD molecular sieve membrane, the synthesis liquid is added with metal cations Cu 2+ The pore diameter was adjusted to be in the range of 0.26-0.28 nm; and a ruthenium-based catalytic layer (thickness of about 1 μm) was obtained on its surface by impregnation. The ammonia / hydrogen separation selectivity (permeation rate ratio) was greater than 400, indicating that the ammonia permeation rate was much greater than the hydrogen permeation rate (the latter was almost the test limit). It was determined that the pore size of the Cu-SOD molecular sieve membrane was between the kinetic diameters of ammonia (0.26 nm) and hydrogen (0.28 nm), and the pore size range was 0.26-0.28 nm. This selectivity was higher than that of Cu 2+ The modification was one order of magnitude higher, confirming the effectiveness of the above-mentioned ion pore regulation.

[0075] The characteristics of the SOD molecular sieve membrane include: (1) The SOD molecular sieve membrane has high chemical stability and can resist the erosion of various chemical substances, including corrosive media such as acids and alkalis. At the same time, its thermal stability is also very high, and it can maintain structural stability and performance invariance in high temperature environments, which gives it significant advantages in high-temperature separation and catalytic processes. (2) The SOD molecular sieve membrane exhibits excellent mechanical strength and can withstand certain pressures and mechanical shocks, ensuring stable operation under complex working conditions. (3) Due to its unique pore structure (0.26-0.28nm) and molecular size selectivity, the SOD molecular sieve membrane can effectively separate molecules of different sizes and achieve efficient material separation and purification. (4) The properties of the SOD molecular sieve membrane may be hydrophilic and have preferential adsorption for the polar molecule ammonia.

[0076] The low-temperature, low-pressure ammonia synthesis membrane reactor is in operation. H2 (~31.5 kmol / h) and N2 (~10.5 kmol / h) feedstocks are first thoroughly mixed in feedstock mixer 8 before entering multi-stage compressor 9 to raise the pressure from atmospheric pressure to the reaction pressure of 9 MPa. The mixed feedstock gas is compressed by multi-stage compressor 9 and then fed into deoiler 10 for purification. The mixed feedstock gas then enters feedstock temperature controller 11 to maintain a feedstock temperature of approximately 200°C and a space velocity of 40,000 ml·g -1 ·h -1 The raw gas is fed into the circulating pre-reactor 12 and then into the ammonia synthesis membrane reactor 14 for separation-reaction-separation cycle (the operating temperature is about 200 ° C, the space velocity is 8000 ml·g -1 ·h -1 ), the retentate side of the ammonia synthesis membrane reactor 14 is compressed by the circulating compressor 13 and then sent to the circulating pre-reactor 12. The permeate side of the ammonia synthesis membrane reactor 14 produces 7.46 kmol / h of ammonia-rich gas, and the retentate side produces 27.19 kmol / h of ammonia-lean gas, which is sent to the circulating pre-reactor 12 through the circulating compressor. The composition of the permeate and retentate side discharges is shown in Table 1.

[0077] Table 1 Composition of the discharge from the ammonia synthesis membrane reactor of Example 1

[0078]

[0079]

[0080] The permeate discharge from the ammonia synthesis membrane reactor 14 is then passed through the liquefaction separator 15 for cryogenic cooling of NH3, reducing the pressure to atmospheric pressure and the temperature to -30°C. The liquefied ammonia product (7.28 kmol / h, ammonia molar content: ≥99%) is produced at the lower end of the liquefaction separator 15 and fed into the ammonia product tank 16. The gas at the upper end (0.18 kmol / h) is circulated to the raw material mixer. See Table 2 for details.

[0081] Table 2 Example 1 Low temperature separation cycle material composition

[0082]

[0083] Through simulation calculations using software such as Aspen Plus and combined with the current status of industrial applications, the operating energy consumption of the low-temperature, low-pressure ammonia synthesis membrane reactor device under corresponding operating conditions can be obtained. The specific energy consumption is shown in Table 3.

[0084] Table 3 Energy consumption of main equipment in Example 1

[0085]

[0086] Example 2

[0087] The ammonia synthesis unit based on the ammonia membrane reactor has a target output of 1,000 tons (125 kg / h) of qualified ammonia products (ammonia content ≥ 99%) per year.

[0088] The membrane reactor used uses a 61-channel ceramic membrane as a carrier, and a layer of SOD molecular sieve membrane (thickness of about 0.5 μm) is loaded on the surface. During the in-situ synthesis of the SOD molecular sieve membrane, the synthesis liquid is exposed to the presence of an external metal cation Cu. 2+ The pore diameter is adjusted to a range of 0.26-0.28 nm, and a Pt catalyst layer (about 1 μm thick) is formed on the surface by impregnation. The pore diameter range can be analyzed by the separation selectivity parameter of the gas separation performance test.

[0089] Characteristics of SOD molecular sieve membrane: (1) SOD molecular sieve membrane has high chemical stability and can resist the erosion of various chemical substances, including corrosive media such as acids and alkalis. At the same time, its thermal stability is also very high, and it can maintain structural stability and performance invariance in high temperature environments, which gives it significant advantages in high-temperature separation and catalytic processes. (2) SOD molecular sieve membrane exhibits excellent mechanical strength and can withstand certain pressures and mechanical shocks, ensuring stable operation under complex working conditions. (3) Due to its unique pore structure (0.26-0.28nm) and molecular size selectivity, SOD molecular sieve membrane can effectively separate molecules of different sizes and achieve efficient material separation and purification. (4) The properties of SOD molecular sieve membrane may be hydrophilic and have preferential adsorption for polar molecule ammonia.

[0090] The process includes the following steps: (1) pelletizing the SOD powder loaded ruthenium-based catalyst, placing it in a circulating pre-reactor 12, and orderly filling the multi-channel catalytic membrane into the assembly to construct an ammonia synthesis membrane reactor 14; (2) operating the low-temperature and low-pressure ammonia synthesis membrane reaction device. The H2 (~36.75kmol / h) and N2 (~12.25kmol / h) raw materials are first fully mixed in the raw material mixer 8, and then enter the multi-stage compressor 9 to increase the pressure from atmospheric pressure to 5MPa. After being compressed by the multi-stage compressor 9, the mixed raw gas is integrated into the deoiler 10 for purification of the raw gas, and then enters the raw material temperature controller 11 to control the raw gas temperature at about 200°C and the air velocity at 40,000ml·g -1 ·h -1 The raw gas is fed into the circulating pre-reactor 12 and then into the ammonia synthesis membrane reactor 14 for separation-reaction-separation cycle (the operating temperature is about 200 ° C, the space velocity is 8000 ml·g -1 ·h -1 ), the retentate side of the ammonia synthesis membrane reactor 14 is compressed by the circulating compressor 13 and then sent to the circulating pre-reactor 12. The permeate side of the ammonia synthesis membrane reactor 14 produces 7.36 kmol / h of ammonia-rich gas, and the retentate side produces 34.29 kmol / h of ammonia-lean gas, which is sent to the circulating pre-reactor 12 through the circulating compressor. The composition of the permeate and retentate side discharges is shown in Table 4.

[0091] Table 4 Composition of the discharge from the ammonia synthesis membrane reactor of Example 2

[0092]

[0093] The discharge from the permeate side of the ammonia synthesis membrane reactor 14 is then passed through a low-temperature separator 15 for cryogenic operation of NH3, reducing the pressure to normal pressure and the temperature to -30°C. The liquefied ammonia product (6.6 kmol / h, ammonia molar content: ≥99%) is produced at the lower end of the liquefied separator 15 and fed into the ammonia product tank 16. The gas at the upper end (0.76 kmol / h) is circulated to the raw material mixer. The specific composition is shown in Table 5.

[0094] Table 5 Example 2 Low temperature separation cycle material composition

[0095]

[0096] Through simulation calculations using software such as Aspen Plus and combined with the current status of industrial applications, the operating energy consumption of the low-temperature, low-pressure ammonia synthesis membrane reactor device under corresponding operating conditions can be obtained. The specific energy consumption is shown in Table 6.

[0097] Table 6 Energy consumption of main equipment in Example 2

[0098]

[0099]

[0100] Example 3

[0101] The ammonia synthesis unit based on the ammonia membrane reactor has a target output of 1,800 tons (225 kg / h) of qualified ammonia products (ammonia content ≥ 99%) per year.

[0102] The membrane reactor used uses a 61-channel ceramic membrane as a carrier, and a layer of SOD molecular sieve membrane (thickness of about 500nm) is loaded on the surface. During the in-situ synthesis of the SOD molecular sieve membrane, the synthesis liquid is exposed to the presence of a metal cation Cu. 2+ The pore diameter is adjusted to a range of 0.26-0.28 nm. A ruthenium metal / alumina supported catalyst is pre-prepared by impregnation. The catalyst particles are then formed into a sol, the viscosity of which is adjusted. The ruthenium metal / alumina supported catalyst is then loaded onto the outer surface of the molecular sieve membrane by an impregnation and Czochralski method. The catalyst is then activated by calcination at 350°C for 6 hours. A catalytic film (approximately 50 μm thick) of the metal / alumina supported catalyst and molecular sieve membrane is then formed on the surface by impregnation.

[0103] Characteristics of SOD molecular sieve membrane: (1) SOD molecular sieve membrane has high chemical stability and can resist the erosion of various chemical substances, including corrosive media such as acids and alkalis. At the same time, its thermal stability is also very high, and it can maintain structural stability and performance invariance in high temperature environments, which gives it significant advantages in high-temperature separation and catalytic processes. (2) SOD molecular sieve membrane exhibits excellent mechanical strength and can withstand certain pressures and mechanical shocks, ensuring stable operation under complex working conditions. (3) Due to its unique pore structure (0.26-0.28nm) and molecular size selectivity, SOD molecular sieve membrane can effectively separate molecules of different sizes and achieve efficient material separation and purification. (4) The properties of SOD molecular sieve membrane may be hydrophilic and have preferential adsorption for polar molecule ammonia.

[0104] The method comprises the following steps: (1) granulating the catalyst containing Pt loaded on SOD powder, placing it in a circulating pre-reactor 12, and orderly filling the multi-channel catalytic membrane into the assembly to construct an ammonia synthesis membrane reactor 14; (2) operating the low-temperature and low-pressure ammonia synthesis membrane reaction device. The H2 (~56.7kmol / h) and N2 (~18.9kmol / h) raw materials are first fully mixed in the raw material mixer 8, and then enter the multi-stage compressor 9 to increase the pressure from atmospheric pressure to the reaction pressure of 8MPa. After being compressed by the multi-stage compressor 9, the mixed raw gas is integrated into the deoiler 10 for purification of the raw gas and then enters the raw material temperature controller 11 to control the raw gas temperature at about 250°C and the air velocity at 40,000ml·g -1 ·h -1The raw gas is fed into the circulating pre-reactor 12 and then into the ammonia synthesis membrane reactor 14 for separation-reaction-separation cycle (the operating temperature is about 200 ° C, the space velocity is 8000 ml·g -1 ·h -1 ), the retentate side of the ammonia synthesis membrane reactor 14 is compressed by the circulating compressor 13 and then sent to the circulating pre-reactor 12. The permeate side of the ammonia synthesis membrane reactor 14 produces 13.15 kmol / h of ammonia-rich gas, and the retentate side produces 49.22 kmol / h of ammonia-lean gas, which is sent to the circulating pre-reactor 12 through the circulating compressor. The composition of the permeate and retentate side discharges is shown in Table 7.

[0105] Table 7 Composition of the discharge from the ammonia synthesis membrane reactor of Example 3

[0106]

[0107] The discharge from the permeate side of the ammonia synthesis membrane reactor 14 is then passed through the liquefaction separator 15 for cryogenic operation on NH3, reducing the pressure to normal pressure and the temperature to -30°C. The liquefied ammonia product (13 kmol / h, ammonia molar content: ≥99%) is produced at the lower end of the liquefaction separator 15 and sent to the ammonia product tank 16, and the gas at the upper end (0.15 kmol / h) is circulated to the raw material mixer. See Table 8 for details.

[0108] Table 8 Example 3 Low temperature separation cycle material composition

[0109]

[0110] Through simulation calculations using software such as Aspen Plus and combined with the current status of industrial applications, the operating energy consumption of the low-temperature, low-pressure ammonia synthesis membrane reactor device under corresponding operating conditions can be obtained. The specific energy consumption is shown in Table 9.

[0111] Table 9 Energy consumption of main equipment in Example 3

[0112]

[0113] Comparative Example 1

[0114] Compared with Example 1, a molecular sieve membrane without a catalyst layer was used as the ammonia separator. The remaining process steps and parameters were the same.

[0115] Table 10 Composition of the discharge from the ammonia synthesis membrane reactor on the permeate side of the molecular sieve membrane in Example 1 and Comparative Example 1

[0116]

[0117]

[0118] The catalytic membrane can improve the reaction conversion rate and increase the permeability of ammonia in the membrane.

[0119] Comparative Example 2

[0120] like Figure 3 This comparative example employs the Haber-Bosch process, a conventional ammonia synthesis process in the chemical industry, and includes equipment such as a feed multi-stage compressor 17 and an ammonia synthesis tower 20. The multi-stage compressor 17 is connected to the inlet of an oil remover 18; the inlet of the oil remover 18 is connected to the multi-stage compressor 17, and the outlet is connected to the inlet of a raw material temperature controller 19; the outlet of the raw material temperature controller 19 is connected to the feed inlet of the ammonia synthesis tower 20; the feed inlet of the ammonia synthesis tower 20 is connected to the outlet of the raw material temperature controller 19; the ammonia synthesis tower 20 is provided with a refrigerant inlet and outlet; the discharge of the ammonia synthesis tower 20 is connected to the inlet of a cooling tower 21; the inlet of the cooling tower 21 is connected to the discharge of the ammonia synthesis tower 20, and the outlet is connected to the inlet of a low-temperature separator 22; the inlet of the low-temperature separator 22 is connected to the outlet of the cooling tower 21, the liquid phase outlet is connected to the inlet of a liquid nitrogen storage tank 23, and the gas phase outlet is connected to a circulation compressor 24; the inlet of the liquid nitrogen storage tank 23 is connected to the outlet of the low-temperature separator 22, and the liquid phase is withdrawn or transported internally.

[0121] The traditional ammonia synthesis process uses the Haber-Bosch process, with a target annual production of 1,000 tons (125 kg / h) of qualified ammonia product (ammonia content ≥99%). The specific process is as follows: A hydrogen-nitrogen mixture (N2: 24.53 kmol / h, H2: 73.53 kmol / h) is compressed to 30 MPa by a multi-stage compressor 17. Cooling water is introduced between the compressor stages to control the compressor outlet temperature. The compressed mixture first enters a deoiler 18 for impurity removal and then passes through a feed temperature controller 19 to control the feed gas temperature at approximately 450°C. The feed gas is then fed into an ammonia synthesis tower 20 for reaction. The maximum single-pass H2 conversion in the ammonia synthesis reaction is 15% over conventional iron-based catalysts. Therefore, the specific composition of the discharge from ammonia synthesis tower 20 is shown in Table 11.

[0122] Table 11 Comparative Example 1 Haber Bosch (Haber) process ammonia synthesis tower discharge composition

[0123]

[0124] The fully reacted ternary mixture is then fed into cooling tower 5 for thorough decompression and cooling before being fed into low-temperature separator 22 for further separation. The pressure in cooling tower 21 is reduced to approximately atmospheric pressure and the temperature to 100°C, while the temperature in low-temperature separator 22 is cooled to approximately -30°C. After decompression and condensation in cooling tower 21 and low-temperature separator 22, the tower bottom produces 7.4 kmol / h of liquefied NH3 product (99% molar content), while the top of the tower produces 83.43 kmol / h of a nitrogen-hydrogen ternary mixture containing trace amounts of NH3. The NH3 product is transferred to liquid nitrogen storage tank 23. The nitrogen-hydrogen mixture is compressed in multiple stages by recycle compressor 24 before being fed into deoiler 18 to continue the ammonia synthesis cycle. The composition of the recycle materials is shown in Table 12.

[0125] Table 12 Comparative Example 1 Recycled Material Composition

[0126]

[0127] Through simulation calculations using software such as Aspen Plus and combined with the current status of industrial applications, the operating energy consumption under the corresponding working conditions of the Haber Bosch method can be obtained. The specific energy consumption is shown in Table 13.

[0128] Table 13 Comparative Example 1 Haber Bosch process main equipment operating energy consumption

[0129]

[0130] In summary, the low-temperature, low-pressure ammonia synthesis membrane reactor device provided by this invention offers significant advantages over the existing Haber-Bosch process in terms of single-pass H2 conversion, reaction conditions, and operating energy consumption. Specifically, the single-pass H2 conversion is increased by 15-20%, while operating energy consumption can be reduced by over 60%, significantly reducing operating costs and making it suitable for a wide range of ammonia synthesis applications.

Claims

1. A method for synthesizing ammonia by a membrane reactor, characterized in that: The steps include: The synthesis gas composed of H2 and N2 is synthesized through ammonia pre-reaction and then directly fed into the ammonia permeable separation membrane for ammonia selective permeation separation without cooling; The ammonia separation membrane may or may not contain an ammonia synthesis catalyst, wherein the ammonia synthesis catalyst is used to catalyze the synthesis of ammonia from H2 and N2 in the synthesis gas; The retentate side material of the ammonia separation membrane is returned to the ammonia pre-reaction synthesis process; the permeate side material is subjected to ammonia purification.

2. The method for synthesizing ammonia by using a membrane reactor according to claim 1, characterized in that: During the ammonia pre-reaction synthesis process, the space velocity range is 10000-60000 ml·g -1 ·h -1 , 150-400℃, reaction pressure 0.1-10MPa; and the reaction raw materials are deoiled.

3. The method for synthesizing ammonia using a membrane reactor according to claim 1, wherein: The separation layer of the ammonia separation membrane has a separation factor greater than 3 for NH3 / H2 and greater than 3 for NH3 / N2.

4. The method for synthesizing ammonia using a membrane reactor according to claim 3, wherein: The ammonia permeable separation membrane is a self-supporting membrane or a composite membrane including a carrier. The separation layer of the ammonia permeable separation membrane is made of a polymer or an inorganic material.

5. The method for synthesizing ammonia using a membrane reactor according to claim 4, wherein: The polymer is selected from polyimide film, polyamide film, polyurethane film, polyethylene film, polytetrafluoroethylene film, polymethacrylic acid film, polybenzodioxane film, polybenzoxazole film, polysulfone film, polyethylene terephthalate film, polyetherimide film or polyethersulfone film; the inorganic material is selected from molecular sieve membrane, ceramic membrane, metal membrane, transition metal chalcogenide membrane, two-dimensional transition metal carbide membrane, two-dimensional transition metal nitride membrane, layered double hydroxide membrane, hexagonal boron nitride membrane, mica nanosheet membrane, metal-organic framework membrane, carbon film or graphene membrane.

6. The method for synthesizing ammonia using a membrane reactor according to claim 5, wherein: The molecular sieve membrane is a SOD molecular sieve membrane, an AEI molecular sieve membrane or a CHA molecular sieve membrane, which is loaded on the surface of a carrier by in-situ synthesis or secondary synthesis, and the pore size is adjusted by adding cations to the synthesis solution; the cations are K + 、Ti 4+ , Rb + , Ca 2+ 、Sr 2+ 、Ag + 、Cu 2+ One or more of the .

7. The method for synthesizing ammonia using a membrane reactor according to claim 1, wherein: The configuration of the ammonia permeable separation membrane is single tube type, multi-channel type, flat plate type, hollow fiber type or coil type; the diameter of the gas cross-flow channel is 2-50 mm, and the thickness of the separation layer of the ammonia permeable separation membrane is 0.1-20 μm.

8. The method for synthesizing ammonia using a membrane reactor according to claim 1, wherein: When the ammonia permeable separation membrane contains an ammonia synthesis catalyst, the catalyst is loaded in one of the following two ways or in a combination of the two: first, the surface of the separation layer of the ammonia permeable separation membrane is also loaded with a catalyst layer, and the thickness of the catalyst layer is 1-100 μm; second, the ammonia synthesis catalyst is located in the cross-flow channel of a single-tube, multi-channel, flat-plate, hollow fiber or coiled ammonia permeable membrane, and the channel is partially or completely filled with the catalyst; the main catalyst used in the ammonia synthesis catalyst layer is an iron-based catalyst, a ruthenium-based catalyst, a molybdenum-based catalyst, a nickel-based catalyst, a cobalt-based catalyst, a platinum-based catalyst or a palladium-based catalyst; the secondary catalyst is a mixture of one or more of aluminum oxide, zirconium oxide and titanium oxide.

9. The method for synthesizing ammonia using a membrane reactor according to claim 8, wherein: When the ammonia synthesis catalyst on the ammonia separation membrane performs the catalytic reaction, the space velocity range is 2000-15000 ml g -1 ·h -1 , pressure is 0.1-10MPa.

10. An ammonia synthesis device based on a membrane reactor, characterized in that: include: A circulating pre-reactor for synthesizing ammonia by pre-reaction of synthesis gas composed of H2 and N2; An ammonia permeable separation membrane is connected to the outlet of the circulating pre-reactor and is used for permeation separation of ammonia; and the surface of the ammonia permeable separation membrane may or may not contain an ammonia synthesis catalyst, and the ammonia synthesis catalyst is used to catalyze the synthesis of ammonia from H2 and N2 in the synthesis gas; A liquefaction separator connected to the permeate outlet of the ammonia separation membrane is used to purify ammonia from the permeate gas; When the circulating pre-reactor is connected to the ammonia separation membrane, no cooling equipment is included.

11. The ammonia synthesis device based on a membrane reactor according to claim 10, characterized in that: The separation layer of the ammonia separation membrane has a separation factor of greater than 3 for NH3 / H2 and greater than 3 for NH3 / N2.

12. The ammonia synthesis device based on a membrane reactor according to claim 11, characterized in that: The ammonia permeable separation membrane is a self-supporting membrane or a composite membrane including a carrier. The material of the selective separation layer on the ammonia permeable separation membrane is selected from polymers or inorganic materials.

13. The ammonia synthesis device based on a membrane reactor according to claim 12, characterized in that: The polymer is selected from polyimide film, polyamide film, polyurethane film, polyethylene film, polytetrafluoroethylene film, polymethacrylic acid film, polybenzodioxane film, polybenzoxazole film, polysulfone film, polyethylene terephthalate film, polyetherimide film or polyethersulfone film; the inorganic material is selected from molecular sieve membrane, ceramic membrane, metal membrane, transition metal chalcogenide membrane, two-dimensional transition metal carbide membrane, two-dimensional transition metal nitride membrane, layered double hydroxide membrane, hexagonal boron nitride membrane, mica nanosheet membrane, metal-organic framework membrane, carbon film or graphene membrane.

14. The ammonia synthesis device based on a membrane reactor according to claim 10, characterized in that: Also includes: A raw material mixer for mixing H2 and N2; The configuration of the ammonia permeable separation membrane is single-tube, multi-channel, flat, hollow fiber or coiled; the diameter of the gas cross-flow channel is 2-50 mm, the ammonia permeable separation membrane adopts a composite membrane containing a carrier, and the thickness of the separation layer is selected to be 0.1-20 μm, and the thickness of the catalyst layer is 1-100 μm; the molecular sieve membrane is a SOD molecular sieve membrane, an AEI molecular sieve membrane and a CHA molecular sieve membrane, which is loaded on the surface of the carrier by in-situ synthesis or secondary synthesis, and the pore size is adjusted by adding cations during the synthesis; the cation is K + 、Ti 4+ , Rb + , Ca 2+ 、Sr 2+ 、Ag + 、Cu 2+ One or more of the .

15. The ammonia synthesis device based on a membrane reactor according to claim 10, characterized in that: When the surface of the ammonia permeable separation membrane contains an ammonia synthesis catalyst, the catalyst is loaded in one of the following two ways or a combination of the two: The first type: the surface of the ammonia separation membrane is also loaded with a catalyst layer, the thickness of the catalyst layer is 1-100 μm; The second type: the ammonia synthesis catalyst is located in the cross-flow channel of a single-tube, multi-channel, flat-plate, hollow fiber or spiral ammonia separation membrane, which is partially or completely filled with the catalyst.

16. The ammonia synthesis device based on a membrane reactor according to claim 14, characterized in that: The main catalyst used in the ammonia synthesis catalyst layer is an iron-based catalyst, a ruthenium-based catalyst, a molybdenum-based catalyst, a nickel-based catalyst, a cobalt-based catalyst, a platinum-based catalyst or a palladium-based catalyst; the sub-catalyst is a mixture of one or more of aluminum oxide, zirconium oxide and titanium oxide.

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