U-shaped hollow fiber membrane catalytic membrane reactor for catalytic conversion of carbon dioxide

Abstract

The invention relates to the field of membranes, membrane separation and membrane catalytic reaction, and discloses a novel U-shaped hollow fiber membrane separation and catalytic membrane reactor assembly, which sequentially comprises a U-shaped hollow fiber membrane bundle, a heat insulation layer and a packaging base from top to bottom. The packaging base comprises two cavities used for air inlet and air outlet of the U-shaped membrane respectively, the U-shaped hollow fiber membrane penetrates through the heat insulation layer and the upper layer of the packaging base and is arranged in the two cavities, and the heat insulation layer plays a role in protecting the hollow fiber membrane and prevents a sealant used by the membrane and the packaging base from being melted. The packaging base is connected with gas, and the gas flows in from one end of the packaging base, passes through the U-shaped hollow fiber membrane bundle and flows out from the other end of the packaging base. The U-shaped hollow fiber membrane module provided by the invention is simple and compact in structure, high in flexibility, convenient to seal and low in leakage risk, the effective membrane area is increased, and the U-shaped hollow fiber membrane module has higher reliability and is easy to intensively amplify.

Description

Technical Field

[0001] This invention relates to the preparation of reforming catalyst structures and catalytic membrane reactors that can be used for the thermal decomposition of carbon dioxide. Background Technology

[0002] Catalytic thermal decomposition of carbon dioxide (CO2) (CO2→CO+1 / 2O2, ΔH) 898 (283 kJ / mol) is a highly promising carbon-negative technology pathway. This reaction can not only convert the main greenhouse gas CO2 into valuable fuels and chemicals, but also achieve the recycling of carbon resources. However, this reaction is strongly endothermic and strictly limited by thermodynamic equilibrium, with extremely low conversion rates even at atmospheric pressure and high temperatures up to 2000 °C. This means that to achieve an economically viable reaction rate and conversion rate, a continuous high-temperature energy input must be provided, and the thermodynamic equilibrium limitations of the reaction must be overcome. Therefore, the reaction is not easy to occur in a fixed-bed reactor. To ensure the reaction occurs, the reactor needs to be under extremely high temperature conditions, and the separation of products after the reaction is difficult. Moreover, under high temperature conditions, the oxygen and carbon monoxide products pose an explosion risk when they reach a certain concentration. If an oxygen permeation membrane is used, on the one hand, the oxygen permeation membrane removes the products from the reaction, shifting the chemical equilibrium of the reaction and increasing the conversion rate; on the other hand, membrane technology can separate the products simultaneously with the reaction. Therefore, membrane technology that couples separation and catalysis is expected to improve the catalytic conversion efficiency of carbon dioxide and the selectivity of the target products.

[0003] Perovskite hybrid conductor materials are an important component of membrane technology. Among them, the hybrid ion-electron conductor perovskite oxygen-permeable membrane is a type of dense, defect-free inorganic ceramic membrane. Under high-temperature conditions, oxygen at the high oxygen partial pressure end diffuses to the surface of the oxygen-permeable membrane and is adsorbed. The oxygen then dissociates into chemisorbed oxygen, which enters the lattice oxygen vacancies on the membrane surface. Under the oxygen vacancy gradient, directional lattice oxygen vacancy diffusion occurs. Finally, the chemisorbed oxygen releases electrons on the other side of the membrane to form oxygen molecules, which desorb from the membrane surface and diffuse into the low partial pressure gas phase with the purge of the carrier gas. This type of membrane can achieve oxygen separation without the need for external circuitry, and theoretically, the selectivity for oxygen is 100%.

[0004] Currently, membrane reactors mostly adopt sheet or tubular configurations. However, these structures generally suffer from low permeation flux and limited effective specific surface area, restricting their industrial-scale application. Thin-walled hollow fiber membranes can be obtained through wet spinning and possess advantages such as a large effective permeation membrane area per unit volume, high oxygen permeability, and ease of assembly into large-scale units. This makes hollow fiber membranes considered the most promising membrane type for future industrial applications. In carbon dioxide conversion, the highest conversion rate achieved by existing membrane reactors is only 28%. Perovskite-type oxygen-permeable membranes can be classified into three types according to their geometry: sheet, tubular, and hollow fiber membranes. Among them, hollow fiber membranes exhibit significant advantages due to their large specific surface area, low oxygen permeation resistance, and high oxygen flux. A phase transformation combined with a one-step heat treatment process has enabled the mass production of hollow fiber membranes. In particular, four-channel hollow fiber membranes not only possess excellent mechanical strength, making them suitable for the construction of catalytic membrane reactors, but also, due to their high flux and modular potential, are an ideal choice for industrial applications. Furthermore, the membrane material must maintain stable oxygen permeation performance at high temperatures over a long period and possess sufficient mechanical durability to support the assembly and operation of the actual reactor. From an economic and applicability perspective, an ideal membrane material should also have low cost, be able to withstand reducing atmospheres, and meet the needs of large-scale industrial applications.

[0005] To date, straight hollow fiber membranes have attracted widespread attention due to their large effective separation area per unit volume, and more and more researchers are dedicated to the development and application of this type of membrane material. However, under actual temperature variation conditions, straight hollow fiber membranes still have significant mechanical reliability issues. Because their ends are usually rigidly fixed in the outer tube, the thermal stress generated during heating and cooling cannot be effectively released through longitudinal expansion and contraction, which can easily lead to membrane breakage, severely limiting their long-term stability and engineering applicability in high-temperature environments. Summary of the Invention

[0006] The purpose of this invention is to avoid the shortcomings of existing straight hollow fiber membranes and provide a method for preparing a U-shaped hollow fiber membrane, while also fabricating a catalytic membrane reactor assembly suitable for carbon dioxide reactions. This invention achieves its objective through the following technical solution:

[0007] A U-shaped hollow fiber membrane, the membrane being composed of a mixed ion-electron conductor ceramic material.

[0008] The hybrid ion-electron conductor ceramic material is a perovskite oxide.

[0009] The general chemical formula of the perovskite oxide is A. 1-x A' x B y B' 1-y O 3-δWherein, A and A' are selected from at least one of La, Sm, Ca, Sr, and Ba, and B and B' are selected from at least one of Co, Fe, Mn, Cr, Ni, Cu, Nb, Ce, Zr, Y, Pr, and Ta, and 0≤x≤1, 0≤y≤1, and δ is the number of oxygen lattice defects.

[0010] The hollow fiber membrane is a multi-channel hollow fiber membrane.

[0011] The U-shaped hollow fiber membrane has a length of 80-120cm, an outer diameter of 1-5mm, and an inner diameter of 0.5-3mm; and / or, the span of the U-shaped bend of the U-shaped hollow fiber membrane is 4-8cm.

[0012] A hollow fiber membrane reactor assembly includes: at least one U-shaped hollow fiber membrane (1); a sealing base (3), wherein the U-shaped hollow fiber membrane has a head end and a tail end, both of which are inserted into and sealed within the sealing base (3), wherein the sealing base (3) has an inlet cavity and an outlet cavity that are isolated from each other, and the head end and the tail end of the U-shaped hollow fiber membrane are respectively connected to the inlet cavity and the outlet cavity; and a heat insulation layer (2) disposed between the high-temperature working area of ​​the U-shaped hollow fiber membrane and the sealing base (3).

[0013] The component includes 1-100 of the U-shaped hollow fiber membranes (1).

[0014] The encapsulation base (3) seals and fixes the first and last ends of the U-shaped hollow fiber membrane with a sealing material.

[0015] The sealing material is selected from at least one of ceramic adhesive, cyanoacrylate sealant, epoxy resin, polyvinyl acetate, phenolic resin, or silicone rubber.

[0016] The material of the insulation layer (2) is selected from at least one of mullite, alumina, vermiculite, diatomite, slag wool, asbestos or expanded perlite.

[0017] The component also includes an outer cover (4), and the material of the encapsulation base (3) and / or the outer cover (4) is selected from at least one of stainless steel, nylon, photosensitive resin, ABS material, aluminum alloy, titanium alloy, copper, cobalt-chromium alloy or ceramic.

[0018] A method for preparing a U-shaped hollow fiber membrane includes the following steps:

[0019] (a) Prepare a spinning solution containing mixed ion-electron conductor ceramic powder, and obtain a straight tubular hollow fiber membrane precursor by spinning process;

[0020] (b) The straight tubular hollow fiber membrane precursor is formed into a U-shaped structure;

[0021] (c) The precursor of the U-shaped structure is subjected to high-temperature sintering to obtain the U-shaped hollow fiber membrane.

[0022] The spinning process in step a) is a wet phase inversion method.

[0023] The spinning solution comprises the mixed ion-electron conductor ceramic powder, a polymer binder, a solvent, and a dispersant; preferably, the polymer binder is polyethersulfone; the solvent is N-methylpyrrolidone; and the dispersant is polyvinylpyrrolidone.

[0024] The wet phase inversion method uses deionized water as the internal coagulation bath and / or external coagulation bath.

[0025] Step b) includes: placing the straight tubular hollow fiber membrane precursor in a softened state into a U-shaped mold for drying and shaping.

[0026] The high-temperature sintering in step c) adopts the double-tube gap constraint sintering method.

[0027] The high-temperature sintering temperature is 1100-1160℃, and the sintering time is 5-8 hours.

[0028] The application of the U-shaped hollow fiber membrane or the hollow fiber membrane reactor assembly in the catalytic conversion of carbon dioxide.

[0029] The carbon dioxide conversion rate X is calculated by solving the following implicit equation. CO2 With hydrogen conversion rate X H2 ;

[0030]

[0031] Where K, α, and φ are the parameters to be fitted, and X is... CO2 It is the shell-side carbon dioxide conversion rate;

[0032] The inlet molar ratio of hydrogen at the tube side inlet to carbon dioxide at the shell side inlet is r = φy H2,o ;

[0033] Flow ratio coefficient F t,0 It is the total molar flow rate at the tube inlet, F CO2,o It is the carbon dioxide molar flow rate at the shell inlet, y H2,o It is the mole fraction of hydrogen at the tube inlet;

[0034] The tube-side hydrogen conversion rate was calculated using the following equation. .

[0035] The beneficial effects of this invention are:

[0036] U-shaped hollow fiber membranes do not tip over or break during thermal expansion, exhibiting excellent adaptive thermal expansion capability and thermal stability. Secondly, the two arms of the U-shape can freely expand and contract within a certain range, alleviating thermal stress accumulation and simplifying system installation and maintenance. Furthermore, the U-shaped membrane can be arranged with one end closed, significantly reducing leakage risk and improving sealing reliability. More importantly, the U-shaped membrane module naturally possesses a "two-in, two-out" flow channel structure, making it particularly suitable for constructing industrial-grade membrane reactor systems, enabling stable, long-term operation under high temperature and high pressure conditions. Therefore, U-shaped hollow fiber membranes have broad prospects in promoting the industrial application of hollow fiber membrane reactors from the laboratory. The U-shaped hollow fiber membrane reactor module effectively improves the membrane sealing problem. When used in permeation and catalytic reaction devices, the prepared U-shaped hollow fiber membrane fundamentally solves the sealing problem and also avoids leakage caused by membrane tube damage due to temperature changes during use. Attached Figure Description

[0037] Figure 1 It is the obtained U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) Hollow fiber membrane appearance.

[0038] Figure 2 It is the obtained U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) SEM microstructure of hollow fiber membrane after sintering.

[0039] Figure 3 This is a schematic diagram of the structure of a U-shaped hollow fiber membrane reactor assembly.

[0040] Figure 4 It is a single 70cm long U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Oxygen permeability of hollow fiber membrane as a function of helium flow rate on the permeate side.

[0041] Figure 5 It is a single 70cm long U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ The oxygen permeability of hollow fiber membranes as the air flow rate on the feed side changes.

[0042] Figure 6 It’s 20 U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Oxygen permeability of hollow fiber membrane modules.

[0043] Figure 7 It’s 20 U-shaped Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Hollow fiber membrane reactor assembly used for performance testing of carbon dioxide decomposition.

[0044] Figure 8 This is a comparison chart of the experimental and predicted values ​​of the fitted sample.

[0045] Figure 9 This is a comparison chart of the experimental and predicted values ​​of the validation sample.

[0046] Figure 10 This is a comparison chart of the experimental and predicted values ​​of the fitted sample.

[0047] Figure 11 This is a comparison chart of the experimental and predicted values ​​of the validation sample. Detailed Implementation

[0048] The U-shaped hollow fiber membrane reactor assembly disclosed in this invention operates by coupling the catalytic decomposition reaction of carbon dioxide with the in-situ separation of the product oxygen. During operation, a feed gas containing carbon dioxide is introduced into the shell-side space between the reactor assembly's outer casing and the U-shaped hollow fiber membrane bundle. Under high-temperature conditions, carbon dioxide undergoes a catalytic decomposition reaction on the outer surface of the U-shaped hollow fiber membrane, generating carbon monoxide and oxygen, thus creating a gaseous environment with a high oxygen partial pressure outside the membrane. Simultaneously, purge gas, such as inert helium or reactive hydrogen, flows through the tube-side channels inside the hollow fiber membrane. Due to the continuous flow of purge gas, the tube-side space inside the membrane maintains an extremely low oxygen partial pressure. The pressure gradient formed between the high oxygen partial pressure outside the membrane and the low oxygen partial pressure inside the membrane constitutes the driving force for the oxygen permeation process. The U-shaped hollow fiber membrane is made of a mixed ion-electron conductor ceramic material, which exhibits excellent selective permeation capability for oxygen at high temperatures. In the shell side, oxygen molecules are adsorbed and dissociated into oxygen ions on the outer surface of the membrane. These oxygen ions, aided by lattice oxygen vacancies, migrate from the outer surface to the inner surface through the membrane's dense crystalline structure. Upon reaching the inner surface, the oxygen ions recombine to form oxygen molecules and desorb, then are carried away by the purge gas in the tube side. This permeation process exhibits extremely high selectivity for oxygen, while remaining densely impermeable to carbon monoxide, carbon dioxide, and other gases such as purge gas components. By continuously removing oxygen, one of the reaction products, from the reaction system, the chemical equilibrium limitation of the carbon dioxide decomposition reaction is effectively broken, promoting a sustained forward reaction and significantly improving the carbon dioxide conversion rate. When hydrogen is used as the purge gas, the oxygen permeating into the tube side reacts with hydrogen to form water. This process more thoroughly consumes the oxygen in the tube side, establishing a stronger permeation driving force and further enhancing the carbon dioxide conversion efficiency.

[0049] In some typical implementations, this patent includes the following technical solutions:

[0050] A U-shaped hollow fiber membrane for carbon dioxide reaction includes the following steps:

[0051] (1) The U-shaped hollow fiber membrane was prepared by wet spinning: N-methylpyrrolidone and dispersant polyvinylpyrrolidone were added to the perovskite powder, followed by polyethersulfone polymer. After thorough stirring and dissolution, the spinning solution was placed in a pressure tank and connected to a spinning head. Under air pressure of 0.1-0.3 MPa, the spinning solution passed through the spinning head into the feed tank. Both the inner and outer coagulation solutions were deionized water. The membrane was left in the tank for 1-2 days to ensure structural stability. The ratio of powder, polyvinylpyrrolidone, N-methylpyrrolidone, and polyethersulfone polymer was 3:1.26:45:11.7, respectively.

[0052] (2) Cut the hollow fiber membrane precursor into 100-120cm pieces, put them in a glass tube and dry them in an oven at 90-120℃ to make them uniform in length and keep them straight. Store the dried samples in a sealed bag for subsequent sintering.

[0053] (3) After softening the precursor in step (2), put it into a U-shaped mold to dry. After drying, put it into a furnace and fire it at 1100-1160℃ for 5-8 hours using the double-tube gap constraint sintering method.

[0054] The hollow fiber membrane mentioned in step (1) is a four-channel hollow fiber membrane, a seven-channel hollow fiber membrane, or a thirteen-channel hollow fiber membrane.

[0055] The hybrid conductor film material mentioned in step (1) is perovskite oxide, and its general formula is A. 1-x A' x B y B' 1- y O 3-δ , where A and A' are any one of La, Sm, Ca, Sr, and Ba, and B and B' are any one of Co, Fe, Mn, Cr, Ni, Cu, Nb, Ce, Zr, Y, Pr, and Ta, 0≤x≤1, 0≤y≤1, and δ is the number of oxygen lattice defects.

[0056] The sintering method used is the double-tube gap constraint sintering method, which uses two alumina tubes to restrict the sintering of the straight tubes at both ends of the U-shape, ensuring the structural uniformity of the U-shaped hollow fiber membrane.

[0057] A U-shaped hollow fiber membrane reactor assembly for carbon dioxide reaction, comprising:

[0058] The U-shaped hollow fiber membrane (1) is sealed in the encapsulation base (3), including the first end and the last end, which are located in the two cavities of the base respectively. It passes through the heat insulation layer (2). The hollow fiber membrane bundle is sealed in the encapsulation base. Finally, the outer cover (4) of the component and the encapsulation base are connected by a flange. Each bundle of U-shaped hollow fiber membranes contains 1-100 hollow fiber membranes. The outer diameter of each U-shaped hollow fiber membrane is 1-5 mm, the inner diameter is 0.5-3 mm, the length is 80-90 cm, and the span of the U-shaped hollow fiber membranes is 4-8 cm.

[0059] The sealing materials are low-temperature sealants such as ceramic adhesive, cyanoisopropionic acid ester, epoxy resin, polyvinyl acetate and phenolic resin.

[0060] The materials used for the encapsulation base and outer cover include 304 stainless steel, 316L stainless steel, nylon, high-performance nylon, translucent photosensitive resin, transparent photosensitive resin, rubber, PAL material, ABS material, aluminum alloy, titanium alloy, copper, cobalt-chromium alloy, ceramics, gypsum, etc., which support the membrane and provide air passages. The encapsulation base is a cylinder with a radius of 50-80cm and a height of 20-30cm.

[0061] The insulation layer is made of mullite, alumina, vermiculite, diatomaceous earth, slag wool, asbestos, and expanded perlite.

[0062] Example 1:

[0063] (1) Preparation of Ba by phase inversion textile method 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ In the process of producing (BSCF) U-shaped hollow fiber membranes, 0.55 g of polyvinylpyrrolidone dispersant was first dissolved in 14 g of N-methylpyrrolidone solvent, followed by the addition of 4.2 g of polyethersulfone polymer, and the mixture was shaken until completely dissolved. Then, 83.5 g of BSCF powder was slowly added, and the mixture was continuously stirred at 500 rpm / min for 24 hours to ensure uniform dispersion of the powder in the polymer solution, forming a casting solution. The uniformly mixed casting solution was injected into the feed tank of a textile equipment and vacuum degassed for 1.5 hours at room temperature to remove air bubbles. Subsequently, under a pressure of 0.25 MPa, the casting solution was extruded through a 5 mm outer diameter spinneret to produce a four-channel hollow fiber membrane with an outer diameter of 4.8 mm and an inner diameter of 1.7 mm, which entered the gelation tank. Both the inner and outer gel solutions were deionized water. The resulting hollow fiber membrane preform was soaked in water for one day to stabilize its structure.

[0064] (2) Cut the prepared hollow fiber membrane precursor into 100 cm segments, place them in a glass tube, and dry them in an oven at 90°C to obtain hollow fiber membrane preforms of uniform length.

[0065] (3) The sintered U-shaped hollow fiber membrane is made from Figure 2 As shown in the figure, the microstructure of the U-shaped hollow fiber membrane was analyzed by scanning electron microscopy. As can be seen from the figure, the grains are tightly connected, and the sintered U-shaped hollow fiber membrane is in a dense state.

[0066] (4) After softening the obtained hollow fiber membrane preform, it was placed in a U-shaped mold for drying. A rectangular mold with a length of 50 cm, a width of 6 cm, a height of 3 cm and a U-shaped groove was used for drying. There were 20 membrane filaments in total. After bundling, the span between the membrane filament bundles was 4-8 cm. After drying, it was placed in a furnace and fired at 1120℃ for 6 hours using the double-tube gap constraint sintering method to obtain the U-shaped hollow fiber membrane. The membrane material was Ba. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ .

[0067] (5) The oxygen permeability of the U-shaped BSCF hollow fiber membrane was determined by chromatography, using He as the purge gas and chromatographic carrier gas, and air as the permeation oxygen source. The effect of air-side flow rate on oxygen permeability at different temperatures was investigated. The purge gas He flowed into the U-shaped hollow fiber membrane from one end, passed through the membrane, and exited from the other end, subsequently entering the connected detection system for analysis. During the experiment, the air flow rate on the air side of the hollow fiber membrane was kept constant at 120 ml / min. The helium flow rate on the permeation side was increased from 30 ml / min to 180 ml / min, while the temperature of the oxygen permeable membrane was adjusted within the range of 800–900 degrees Celsius to investigate the effect of the purge gas flow rate on the U-shaped BSCF hollow fiber membrane. Figure 4 As can be seen, the oxygen permeability increases with the increase of the purge gas velocity, especially in the high-temperature region, where the increase is more significant. This is because the increased purge gas velocity further reduces the oxygen partial pressure on the permeate side, thereby increasing the driving force of the oxygen permeation process (the oxygen partial pressure gradient across the membrane). Therefore, the oxygen permeability of the hollow fiber membrane also increases accordingly. When the operating temperature is low (below 900℃), the oxygen permeability hardly increases with the increase of the purge gas velocity. This is because in these low-temperature regions, the surface exchange process of the oxygen-permeable membrane accounts for an increasingly larger proportion of the entire oxygen permeation process. The effect of increasing the purge gas velocity to increase the oxygen partial pressure difference and thus improve the bulk diffusion rate is greatly weakened.

[0068] (6) The oxygen permeability of the U-shaped BSCF hollow fiber membrane was determined by chromatography. He was used as the purge gas and chromatographic carrier gas, while air was used as the permeation oxygen source. The effect of the purge gas flow rate on the oxygen permeability at different temperatures was investigated. The purge gas He flowed into the U-shaped hollow fiber membrane from one end, passed through the membrane, and exited from the other end, then entered the connected detection system for analysis. During the experiment, the helium flow rate on the permeation side of the hollow fiber membrane was kept constant at 120 ml / min, while the air flow rate on the feed side was increased from 40 ml / min to 200 ml / min. Simultaneously, the temperature of the oxygen permeable membrane was adjusted within the range of 750–900 degrees Celsius to investigate the effect of the feed gas flow rate on the U-shaped BSCF hollow fiber membrane. Figure 5It can be seen that when the air velocity is less than 120 ml / min, the oxygen permeability increases with the increase of air velocity; however, when the air velocity increases within the range of greater than 120 ml / min, the oxygen permeability of the membrane does not increase significantly.

[0069] Example 2

[0070] (1) Based on the U-shaped hollow fiber membrane element structure, a catalytic membrane reactor for coupling carbon dioxide decomposition and hydrogen-oxygen reaction can be constructed. In this reactor, the U-shaped hollow fiber membrane itself or its surface is loaded with a high-temperature carbon dioxide decomposition catalyst (such as perovskite oxide). The outer side of the membrane (shell side) undergoes the carbon dioxide catalytic decomposition reaction (CO2 → CO + 1 / 2O2), and the generated oxygen is selectively separated through an oxygen ion permeation membrane and permeates to the inner side of the membrane (tube side). At the same time, hydrogen is introduced into the inner side of the membrane and reacts with the permeated oxygen to synthesize water (2H2 + O2 → 2H2O). This reactor makes full use of the characteristics of single-sided encapsulation, compact structure, and reliable sealing of the U-shaped membrane. The specific installation and testing can be described as follows:

[0071] (2) Select 20 four-channel hollow fiber U-shaped BSCF hollow fiber membranes with a length of 80-90cm prepared above, test their compactness, and then fix the U-shaped membrane through the heat insulation layer to the encapsulation base with 704 silicone rubber. Install the U-shaped hollow fiber membrane element loaded with carbon dioxide decomposition catalyst in a high temperature and high pressure resistant membrane shell. The outer diameter of the membrane shell is 140mm and the inner diameter is 100mm. The hollow fiber membrane and the module are sealed by cold end. After the glue dries, the sealing head on one side of the membrane element is fastened to the upper and lower end caps through flanges to ensure the sealing performance under high pressure. The U-shaped hollow fiber membrane module is assembled.

[0072] (3) After the apparatus is configured, the oxygen permeability of the apparatus is tested. He is used as the purge gas, and air is used as the oxygen source. The air flow rate is 100 ml / min. The results are as follows: Figure 4 The graph showing the relationship between oxygen permeability and helium gas density is shown. Figure 4 As shown, as the amount of purge gas helium increases, the oxygen partial pressure in the permeation measurement is further reduced, thereby increasing the driving force of the oxygen permeation process.

[0073] (4) An inlet and an outlet are provided on the sidewall of the membrane shell for introducing carbon dioxide feed gas and discharging gaseous products (such as CO and unreacted CO2) after the reaction. After the reactor is installed, an airtightness test is first performed to ensure that there is no leakage in the shell side and the tube side under the operating pressure. Then, a test is conducted under high temperature conditions (usually above 700°C): carbon dioxide gas at a certain flow rate and pressure is introduced into the shell side, while hydrogen gas is introduced into the tube side. The concentrations of CO and CO2 in the outlet gas of the shell side are analyzed by online gas chromatography to calculate the carbon dioxide conversion rate and CO selectivity; the amount of water generated in the tube side is measured by weighing or condensation to evaluate the degree of hydrogen-oxygen reaction and oxygen permeation flux. During the test, the system temperature and pressure need to be monitored and maintained to ensure stability. At the same time, the effects of different space velocities, pressures and hydrogen flow rates on reactor performance (such as carbon dioxide conversion rate, oxygen permeation rate and water production rate) are investigated to evaluate the overall efficiency and long-term operational stability of the U-shaped membrane reactor coupled with carbon dioxide decomposition and hydrogen-oxygen reaction.

[0074] (5) A mixture of H2 and He was used as the reaction gas, while carbon dioxide was introduced outside the membrane. It can be observed that as the hydrogen concentration increased from 5% to 25%, the carbon dioxide conversion rate increased from 21.2% to 32.3%. The coupling of the hydrogen reaction and the carbon dioxide decomposition reaction provided a stronger driving force for the thermal decomposition reaction of carbon dioxide.

[0075] This invention further provides the shell-side CO2 conversion rate X under different inlet H2 concentration conditions. CO2 With the H2 conversion rate X in the tube H2 The prediction model is based on the following construction idea: First, the flux is described by O2 using the Wagner equation for a hybrid conductor oxygen-permeable membrane; then, the atmospheric equilibrium relationship on both sides is used to describe the p-flux. O2 The conversion rate is expressed as a function, and finally, the flux and conversion rate are coupled using overall material balance. Using a molar flow meter, let the CO2 molar flow rate F at the shell-side inlet be... CO2,0 The CO2 and CO flow rates at the shell-side outlet are F2 and F3, respectively. CO2,out F CO,out Then the shell-side CO2 conversion rate is For the inlet of the tube side, there is the H2 molar flow rate F of the H2 / He mixture at the tube side inlet. H2,0 The flow rate F at the outlet H2 of the tube H2,out Then the H2 conversion rate of the tube side can be obtained: .

[0076] Let the total effective area of ​​the membrane be... Where N is the number of membrane roots, d o Where L is the outer diameter and L is the effective length of a single U-shaped hollow fiber, for a dense mixed ion-electron conductor oxygen-permeable membrane, the steady-state oxygen flux can be written using the Wagner equation. J O2 p is the O2 flux of the membrane. O2,s p O2,t The oxygen partial pressures on the shell side and tube side are k, respectively. W Oxygen permeability coefficient, L m For the thickness of the dense film layer, σᵢ, σ e These are the ionic and electronic conductivity, respectively.

[0077] On the other hand, for the calculation of the CO2 / CO / O2 equilibrium relationship in the shell side, in the shell side, the reaction process is assumed to be... Reaction equilibrium constant The oxygen partial pressure on the shell side is obtained. If the shell-side inlet is approximately pure CO2 (or the inertness can negligibly affect the contrast ratio), then ,available .

[0078] For the calculation of the H2 / H2O / O2 equilibrium relationship in the tube process, let the reaction process be assumed. Equilibrium constant The oxygen partial pressure on the tube side is obtained. In the tube process, the presence of inert He will change the total molar flow rate, but the ratio p H2O / p H2 equal to molar ratio F H2O / F H2 Therefore, there is And thus obtain Substituting this into the Wagner equation, we get: Taking the logarithm and substituting back, we get:

[0079]

[0080] Next, we perform an overall material balance calculation. For every 1 mol of CO2 converted in the shell side, 0.5 mol of O2 is generated. If we assume that the O2 generated in the shell side is primarily removed by the membrane, then: Substituting JO2 into the equation, we obtain the implicit equation:

[0081]

[0082] Combine the parameters, set , Then we have:

[0083]

[0084] Assume that only oxygen-consuming reactions occur in the tube side, and that almost all the oxygen permeating in is consumed by H2. Since every 1 mol of CO2 converted in the shell side produces 0.5 mol of O2, and every 1 mol of O2 consumed in the tube side consumes 2 mol of H2, then every 1 mol of CO2 converted corresponds to the consumption of 1 mol of H2. Therefore, we can obtain... Let the H2 / CO2 concentration ratio be defined as r, then Therefore, we get Substituting this into the implicit equation, we can obtain a single equation that only requires solving XCO2:

[0085]

[0086] After obtaining XCO2, it is then possible to calculate... Let the volume fraction of H2 at the tube inlet be y. H2,0 If the increase in H2 is compensated by the decrease in He, then the total flow rate F in the tube during the experiment... t,0 Basically constant, , ,in This transforms the model input from r into y. H2,0 The final prediction model is calculated as follows:

[0087] The model inputs are the operating temperature T and the inlet H2 mole fraction y. H2,0 The parameters to be fitted are K, α, and φ. First, let's consider y... H2,0 Calculate r, Then, by solving for XCO2 and obtaining a numerical solution for the single-variable implicit equation, we have:

[0088]

[0089] Further calculations can be performed to obtain The hydrogen mole fraction y at the inlet of different tubes can be determined. H2,0 Under the given conditions, the carbon dioxide conversion rate X in the oxygen-permeable membrane reactor is output. CO2 With hydrogen conversion rate X H2 The predicted value.

[0090] The experimental data were randomly divided into a 60% fitted sample set and a 40% fitted sample set. After solving the above model, the parameters are as follows:

[0091]

[0092] The R² data for the training and validation groups are as follows:

[0093]

[0094] Experimental values ​​vs. predicted values, plus relative percentage error, are as follows:

[0095]

[0096] As can be seen, the relative error of most of the models in this patent is below 10%, indicating good predictive performance.

Claims

1. A U-shaped hollow fiber membrane, characterized in that, The membrane is composed of a mixed ion-electron conductor ceramic material; the mixed ion-electron conductor ceramic material is a perovskite oxide; the hollow fiber membrane is a single-tube or multi-channel hollow fiber membrane.

2. The U-shaped hollow fiber membrane according to claim 1, characterized in that, The general chemical formula of the perovskite oxide is A. 1-x A' x B y B' 1-y O 3-δ Wherein, A and A' are selected from at least one of La, Sm, Ca, Sr, and Ba, and B and B' are selected from at least one of Co, Fe, Mn, Cr, Ni, Cu, Nb, Ce, Zr, Y, Pr, and Ta, and 0≤x≤1, 0≤y≤1, and δ is the number of oxygen lattice defects.

3. The U-shaped hollow fiber membrane according to any one of claims 1-2, characterized in that, The U-shaped hollow fiber membrane has a length of 80-120cm, an outer diameter of 1-5mm, and an inner diameter of 0.5-3mm; the span of the U-shaped bend in the U-shaped hollow fiber membrane is 4-8cm.

4. A hollow fiber membrane reactor assembly, characterized in that, include: Multiple U-shaped hollow fiber membranes (1) as described in any one of claims 1-3; The encapsulation base (3) has a head end and a tail end, both of which are inserted into the encapsulation base (3) and sealed. The encapsulation base (3) is provided with an air inlet cavity and an air outlet cavity that are isolated from each other. The head end and the tail end of the U-shaped hollow fiber membrane are respectively connected to the air inlet cavity and the air outlet cavity. A heat insulation layer (2) is disposed between the high-temperature working area of ​​the U-shaped hollow fiber membrane and the encapsulation base (3).

5. The hollow fiber membrane reactor assembly according to claim 4, characterized in that, The component includes 1-1000 U-shaped hollow fiber membranes (1); the encapsulation base (3) seals and fixes the first and last ends of the U-shaped hollow fiber membranes with a sealing material.

6. The hollow fiber membrane reactor assembly according to claim 4, characterized in that, The sealing material is selected from at least one of ceramic adhesive, cyanoacrylate sealant, epoxy resin, polyvinyl acetate, phenolic resin, or silicone rubber; the material of the heat insulation layer (2) is selected from at least one of mullite, alumina, vermiculite, diatomaceous earth, slag wool, asbestos, or expanded perlite. The component also includes an outer cover (4), and the material of the encapsulation base (3) and / or the outer cover (4) is selected from at least one of stainless steel, nylon, photosensitive resin, ABS material, aluminum alloy, titanium alloy, copper, cobalt-chromium alloy or ceramic.

7. A method for preparing a U-shaped hollow fiber membrane as described in claim 1, characterized in that, Includes the following steps: a) Prepare a spinning solution containing mixed ion-electron conductor ceramic powder, and obtain a straight tubular hollow fiber membrane precursor by spinning process; b) The straight tubular hollow fiber membrane precursor is shaped into a U-shaped structure; c) The precursor of the U-shaped structure is sintered at high temperature to obtain the U-shaped hollow fiber membrane.

8. The preparation method according to claim 7, characterized in that, The spinning process in step a) is a wet phase inversion method; the spinning solution includes the mixed ion-electron conductor ceramic powder, polymer binder, solvent and dispersant; preferably, the polymer binder is polyethersulfone; the solvent is N-methylpyrrolidone; the dispersant is polyvinylpyrrolidone; the wet phase inversion method uses deionized water as the internal coagulation bath and / or external coagulation bath; Step b) includes: placing the straight tubular hollow fiber membrane precursor in a softened state into a U-shaped mold for drying and shaping; The high-temperature sintering in step c) adopts the double-tube gap-constrained sintering method; The high-temperature sintering temperature is 1100-1160℃, and the sintering time is 5-8 hours.

9. The application of the U-shaped hollow fiber membrane according to any one of claims 1-3 or the hollow fiber membrane reactor assembly according to any one of claims 4-8 in the catalytic conversion of carbon dioxide.

10. The application according to claim 9, characterized in that, The carbon dioxide conversion rate X is calculated by solving the following implicit equation. CO2 With hydrogen conversion rate X H2， And by adjusting the condition parameters in the catalytic process, the conversion rate can be made to reach the expected target value; ； Where K, α, and φ are the parameters to be fitted, and X is... CO2 It is the shell-side carbon dioxide conversion rate; The inlet molar ratio of hydrogen at the tube side inlet to carbon dioxide at the shell side inlet is r = φy H2,o ; Flow ratio coefficient F t,0 It is the total molar flow rate at the tube inlet, F CO2,o It is the carbon dioxide molar flow rate at the shell inlet, y H2,o It is the mole fraction of hydrogen at the tube inlet; The tube-side hydrogen conversion rate was calculated using the following equation. .

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