Atmospheric self-heating bifunctional membrane reactor and method for simultaneously producing propylene and methane

Abstract

The application provides a normal-pressure self-heat-supply dual-function membrane reactor and a method for simultaneously preparing propylene and methane, and belongs to the field of membrane reactors, wherein the normal-pressure self-heat-supply dual-function membrane reactor comprises a shell and a membrane assembly arranged in the shell; propylene is introduced into the shell from a feed port, and the reaction product after propylene dehydrogenation is discharged from a discharge port; the membrane assembly comprises a tubular ceramic membrane, both ends of the tubular ceramic membrane are connected to the outside of the shell, the outer wall of the tubular ceramic membrane and the inner wall of the shell form a first reaction cavity, the inside of the tubular ceramic membrane forms a second reaction cavity, propylene in the first reaction cavity is cracked into propylene and hydrogen, and the hydrogen enters the second reaction cavity through the tubular ceramic membrane; carbon dioxide and hydrogen perform a synthesis reaction in the second reaction cavity to release heat, and the heat is used for heat supply for dehydrogenation in the first reaction cavity. Compared with the prior art, the application solves the technical problems that the comprehensive energy consumption and cost of carbon dioxide utilization and propylene dehydrogenation are high and the two processes cannot be simultaneously performed.

Description

Technical Field

[0001] This invention belongs to the field of membrane reactors, and more specifically, relates to an atmospheric pressure self-heating bifunctional membrane reactor. This invention also relates to a method for simultaneously preparing propylene and methane. Background Technology

[0002] Propylene is an important basic chemical raw material with continuously growing market demand. Direct propane dehydrogenation (PDH) is a crucial process for increasing propylene production. However, this reaction is a strongly endothermic process, requiring high temperatures (typically above 600°C) to achieve reasonable reaction rates and conversion rates, resulting in enormous energy consumption, demanding equipment materials, and high operating costs. Furthermore, high temperatures easily trigger side reactions such as cracking and carbon deposition, affecting catalyst life and product selectivity. While adopting a low-temperature operation strategy can effectively avoid these problems, it leads to a significant decrease in conversion rates due to thermodynamic equilibrium limitations.

[0003] On the other hand, the resource utilization of carbon dioxide, especially its conversion into high-value chemicals such as methane and methanol through hydrogenation, is an important technological pathway to achieve "carbon neutrality." Among these, carbon dioxide methanation (the Sabatier reaction) is a strongly exothermic reaction. If the endothermic demand of propane dehydrogenation can be combined with the exothermic characteristics of carbon dioxide methanation, theoretically, heat complementarity within the reaction system could be achieved, potentially significantly reducing overall energy consumption.

[0004] Existing technologies have attempted to thermally couple the two reactions. For example, this involves using a series-parallel arrangement of fixed-bed reactors or recovering heat using heat exchange networks. However, these methods have significant drawbacks: complex reactor structures and high equipment investment; heat transfer is indirect, resulting in losses and low efficiency; and the two reactions still need to operate under their respective optimal but often different pressure conditions (PDH often requires low pressure for equilibrium, while carbon dioxide hydrogenation often requires higher pressure to improve efficiency), making system coordination difficult. More importantly, the hydrogen produced by propane dehydrogenation is a valuable resource, and traditional coupling methods struggle to achieve immediate, efficient separation and targeted utilization of hydrogen, leading to underutilization of its value and potentially affecting the dehydrogenation reaction equilibrium.

[0005] In recent years, membrane reactor technology has provided new ideas for simultaneously achieving reaction and separation. In particular, hydrogen-selective permeation membranes can remove hydrogen during the reaction process, breaking the thermodynamic equilibrium limitations of the dehydrogenation reaction and thus improving the conversion rate. However, existing membrane reactor designs often focus on the enhancement of a single reaction (such as dehydrogenation or water-gas shift) or only on the membrane's separation function. Furthermore, when operating a single membrane reactor, additional power is needed to generate hydrogen partial pressure to drive the hydrogen permeation process. In contrast, dual-reaction membrane reactors utilize a reaction mechanism of dehydrogenation on one side and hydrogenation on the other to directly induce a hydrogen partial pressure difference across the membrane, automatically generating the driving force for hydrogen permeation and significantly reducing the energy consumption of membrane reactor operation.

[0006] Therefore, developing a bifunctional membrane reactor that performs propane dehydrogenation outside the membrane and carbon dioxide hydrogenation inside the membrane is of critical value. Summary of the Invention

[0007] The purpose of this invention is to provide an atmospheric pressure self-heating dual-function membrane reactor to solve the technical problems of high combined energy consumption and cost of existing carbon dioxide utilization and propane dehydrogenation, which cannot be carried out simultaneously.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: to provide an atmospheric pressure self-heating bifunctional membrane reactor, comprising: The outer shell is provided with an inlet and an outlet. Propane enters the outer shell from the inlet, and the reaction products after propane dehydrogenation are discharged from the outlet. The membrane module includes a tubular ceramic membrane disposed within the housing, with both ends of the tubular ceramic membrane extending to the outside of the housing. The outer wall of the tubular ceramic membrane and the inner wall of the housing enclose a first reaction chamber, and the interior of the tubular ceramic membrane forms a second reaction chamber. Propane in the first reaction chamber is decomposed into propylene and hydrogen, and hydrogen enters the second reaction chamber through the tubular ceramic membrane. Carbon dioxide is introduced into one end of the tubular ceramic membrane, and the material synthesized from carbon dioxide and hydrogen is discharged from the other end of the tubular ceramic membrane; the carbon dioxide and hydrogen undergo a synthesis reaction in the second reaction chamber, which releases heat to heat the dehydrogenation in the first reaction chamber.

[0009] In one feasible implementation, the tubular ceramic membrane includes a separation layer and a reaction layer stacked from the outside to the inside, wherein a second reaction chamber is formed within the reaction layer, and a first reaction chamber is formed between the separation layer and the outer shell; the separation layer is a dense molecular sieve layer that allows only hydrogen molecules to pass through, and the reaction layer includes a loose and porous alumina support and a nickel-based catalyst loaded on the alumina support.

[0010] In one feasible implementation, the first reaction chamber is filled with a platinum-based noble metal catalyst as a supplementary catalyst; the second reaction chamber is filled with nickel and aluminum oxide as supplementary catalysts.

[0011] In one feasible implementation, the second reaction chamber is filled with an inert gas to maintain an inert gas atmosphere in the second reaction chamber.

[0012] In one feasible implementation, the material of the separation layer is... In this equation, x, y, and z represent the mole fractions of silicon, aluminum, and phosphorus, respectively, with x ranging from 0.01 to 0.98, y ranging from 0.01 to 0.6, and z ranging from 0.01 to 0.52, and x + y + z = 1.

[0013] In one feasible implementation, the crystal structure of the separation layer contains a molecular sieve with eight ring pores, the pore size of which is 0.38 nm. 0.38nm.

[0014] In one feasible implementation, the outer casing is provided with a first connecting pipe and a second connecting pipe that are respectively sealed and connected to both ends of the tubular ceramic membrane; the outer periphery of the first connecting pipe and the outer periphery of the second connecting pipe are both sealed and connected to the inner wall of the outer casing, the first connecting pipe is used to introduce carbon dioxide, and the second connecting pipe is used to discharge the material synthesized from carbon dioxide and hydrogen.

[0015] In one feasible implementation, the reaction temperature of the first reaction chamber and the second reaction chamber is between 300°C and 400°C, and the reaction pressure of the first reaction chamber and the second reaction chamber is 1 standard atmosphere.

[0016] In one feasible implementation, the inert gas is made of nitrogen.

[0017] Compared with existing technologies, the beneficial effects of the atmospheric pressure self-heating bifunctional membrane reactor provided by this invention are as follows: Firstly, in this invention, the outer shell serves as a sealed, pressure-bearing body, with its inlet and outlet enabling continuous material input and output. The tubular ceramic membrane, as the core functional component, directly forms two independent reaction spaces through its physical separation (the first reaction chamber for dehydrogenation and the second reaction chamber for synthesis). This invention achieves spatial isolation and functional coupling of the reaction through the combination of these structures: the outer shell provides a stable environment for the entire reaction system, while the tubular ceramic membrane internally achieves spatial isolation and functional coupling of the reaction. With this configuration, propane enters the first reaction chamber through the inlet and undergoes cracking. The resulting hydrogen selectively permeates through the membrane wall into the second reaction chamber, where it reacts with the introduced carbon dioxide in an exothermic synthesis reaction. The heat released by the synthesis reaction is directly transferred through the membrane wall to the adjacent endothermic dehydrogenation reaction. This combination achieves self-circulation of heat and directional material transfer within the reactor, thus achieving the technical effect of self-heating and significantly reduced energy consumption during the reaction process under normal pressure. Furthermore, relying on the selective permeation characteristics of the membrane, the reactor can move the hydrogen generated from propane dehydrogenation to the inner side of the membrane in real time, thereby breaking the thermodynamic equilibrium limitation of the reaction, promoting the continuous forward reaction, and ultimately achieving a conversion rate comparable to high-temperature processes at low temperatures. It is worth noting that the carbon dioxide hydrogenation reaction on the inner side of the membrane not only provides a stable driving force for hydrogen migration across the membrane, but also simultaneously utilizes the permeated hydrogen. This avoids the adverse inhibitory effect of hydrogen enrichment on propane dehydrogenation and achieves the resource conversion of carbon dioxide. Compared with traditional fixed-bed reactors, this bifunctional membrane reactor, operating at a relatively low temperature, can significantly reduce overall energy consumption, improve propylene selectivity, and effectively reduce catalyst carbon deposition and regeneration frequency. Ultimately, it has an urgent need and significant value in achieving the dual goals of efficient propane production to propylene and resource utilization of carbon dioxide, improving the process's economics and environmental friendliness. Furthermore, this invention can solve the technical problems of low external heating efficiency, complex equipment, and high energy consumption in traditional stepwise processes.

[0018] Furthermore, the two types of catalysts function in their respective optimal reaction chambers: the chromium oxide catalyst specifically catalyzes the production of propylene and hydrogen, while the nickel catalyst specifically catalyzes the consumption of hydrogen and releases heat. They are linked by the hydrogen and heat flows transferred through a tubular ceramic membrane. Because the membrane reactor drives the equilibrium conversion, propane dehydrogenation can proceed at 400°C, and the low temperature reduces equipment energy consumption, minimizes side reactions, and improves selectivity. This combination allows the two reactions to proceed efficiently under their respective optimal catalytic conditions, achieving energy complementarity through heat transfer. Therefore, this application achieves the technical effect of improving propylene yield and maintaining system heat balance, preventing the technical problems of a single catalyst being unable to handle both reactions simultaneously, and the complexity of heat management.

[0019] Another object of the present invention is to provide a method for simultaneously preparing propylene and methane, based on the above-described atmospheric pressure self-heating bifunctional membrane reactor; the method for simultaneously preparing propylene and methane further includes the following steps: S1. Inert gas is introduced into the second reaction chamber to maintain an inert gas atmosphere inside the tubular ceramic membrane; S2. Propane is introduced into the first reaction chamber, and carbon dioxide is introduced into the second reaction chamber; S3. Propane is cracked in the first reaction chamber to release hydrogen gas, which is separated by a tubular ceramic membrane and enters the second reaction chamber, where it reacts with carbon dioxide in the second reaction chamber to produce methane. S4. Control the rate of carbon dioxide introduction to maintain the temperature of the first reaction chamber between 300℃ and 400℃.

[0020] Compared to existing technologies, the method for simultaneously preparing propylene and methane in this invention possesses all the advantages of the aforementioned atmospheric pressure self-heating bifunctional membrane reactor, which will not be elaborated upon here. Furthermore, in the method for simultaneously preparing propylene and methane in this invention, step S1 lays the foundation for a safe and efficient reaction; step S2 initiates two parallel reaction processes; step S3 describes the core mechanism of reaction-separation coupling; and step S4 achieves heat balance and stable control of the process. The combination of these steps constitutes a complete operating cycle. First, an inert environment is established to ensure safety and catalytic activity. Then, the two reactions are initiated simultaneously with the feed, utilizing the membrane to achieve directional hydrogen migration and reaction coupling. Finally, by adjusting a simple variable—the feed parameter (carbon dioxide rate)—the reaction temperature of the entire system can be controlled using the intensity of the exothermic reaction. This combination makes the complex bifunctional reaction coupling process simple and controllable. This achieves the technical effect of making the entire self-heating membrane reactor process easy to start, stable in operation, and easy to control, thus helping to solve the technical problems of complex operation, parameter sensitivity, and difficulty in stable operation that often exist in multi-reaction coupling systems. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the atmospheric pressure self-heating dual-function membrane reactor provided by the present invention; Figure 2 This is a flowchart illustrating the steps of the method for simultaneously preparing propylene and methane according to the present invention; Figure 3 This is a scanning electron microscope image of the tubular ceramic membrane in the atmospheric pressure self-heating bifunctional membrane reactor of the present invention.

[0022] In the picture: 1. Outer shell; 11. Inlet; 12. Outlet; 13. First reaction chamber; 2. Membrane module; 21. Tubular ceramic membrane; 211. Separation layer; 212. Reaction layer; 22. First connection pipe; 23. Second connection pipe; 24. Second reaction chamber. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "back" appear, indicating orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0025] Furthermore, in the description of this invention, unless otherwise explicitly defined, the terms "installation," "connection," "joining," and "connector" should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention in light of the specific circumstances.

[0026] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0027] Please refer to the following: Figures 1 to 3 The present invention will now describe the atmospheric pressure self-heating bifunctional membrane reactor. This atmospheric pressure self-heating bifunctional membrane reactor includes a shell 1 and a membrane module 2 disposed within the shell 1. The shell 1 has an inlet 11 and an outlet 12. Propane enters the shell 1 through the inlet 11, and the reactants after propane dehydrogenation are discharged through the outlet 12. The membrane module 2 includes a tubular ceramic membrane 21 disposed within the shell 1. Both ends of the tubular ceramic membrane 21 extend to the outside of the shell 1. The outer wall of the tubular ceramic membrane 21 and the inner wall of the shell 1 together form a first reaction chamber 13. The interior of the tubular ceramic membrane 21 forms a second reaction chamber 24. Propane in the first reaction chamber 13 is decomposed into propylene and hydrogen. Hydrogen enters the second reaction chamber 24 through the tubular ceramic membrane 21. Carbon dioxide is introduced into one end of the tubular ceramic membrane 21, and the material synthesized from carbon dioxide and hydrogen is discharged from the other end. The carbon dioxide and hydrogen undergo an exothermic synthesis reaction in the second reaction chamber 24, providing heat for the dehydrogenation in the first reaction chamber 13.

[0028] In the specific implementation of the above embodiments, in this invention, the outer shell 1 serves as a sealed pressure-bearing body, and its inlet 11 and outlet 12 enable continuous input and output of materials; the tubular ceramic membrane 21, as a core functional component, directly forms two independent reaction spaces through its physical separation function (the first reaction chamber 13 is used for dehydrogenation, and the second reaction chamber 24 is used for synthesis). Through the combination of the above structures, this invention provides a stable environment for the entire reaction system, while the tubular ceramic membrane 21 internally achieves spatial isolation and functional coupling of the reaction.

[0029] In this configuration, propane enters the first reaction chamber 13 through the feed inlet 11 and undergoes cracking. The resulting hydrogen selectively permeates through the membrane wall into the second reaction chamber 24, where it reacts with the introduced carbon dioxide in an exothermic synthesis reaction. The heat released by this synthesis reaction is directly transferred through the membrane wall to the adjacent endothermic dehydrogenation reaction. This combination achieves self-circulation of heat and directional mass transfer within the reactor, thus achieving the technical effect of self-heating of the reaction process under atmospheric pressure and significantly reducing energy consumption. Furthermore, relying on the selective permeation characteristics of the membrane, the reactor can move the hydrogen generated from propane dehydrogenation to the inner side of the membrane in real time, thereby breaking the thermodynamic equilibrium limitation of the reaction and promoting the continuous forward reaction, ultimately achieving a conversion rate comparable to that of high-temperature processes at low temperatures. It is worth noting that the carbon dioxide hydrogenation reaction on the inner side of the membrane not only provides a stable driving force for hydrogen migration across the membrane but also simultaneously utilizes the permeated hydrogen, thus avoiding the adverse inhibitory effect of hydrogen enrichment on propane dehydrogenation and realizing the resource conversion of carbon dioxide. Compared to traditional fixed-bed reactors, this bifunctional membrane reactor, operating at relatively low temperatures, significantly reduces overall energy consumption and improves propylene selectivity. It also effectively reduces catalyst carbon buildup and regeneration frequency, ultimately achieving the dual goals of efficient propane production to propylene and carbon dioxide resource utilization. This improved process economy and environmental friendliness are urgently needed and of significant value. Furthermore, this invention solves the technical problems of low external heating efficiency, complex equipment, and high energy consumption in traditional stepwise processes.

[0030] Based on the above embodiments, in one feasible embodiment, the tubular ceramic membrane 21 includes a separation layer 211 and a reaction layer 212 stacked from the outside to the inside. A second reaction chamber 24 is formed within the reaction layer 212, and a first reaction chamber 13 is formed between the separation layer 211 and the outer shell 1. The separation layer 211 is a dense molecular sieve layer that allows only hydrogen molecules to pass through, and the reaction layer 212 includes loose and porous alumina and a nickel-based catalyst loaded on the alumina support. The dense separation layer 211, based on its ion or atomic-scale channels, plays a sieving role by allowing only hydrogen (or hydrogen molecules) to pass through efficiently.

[0031] The porous reaction layer 212 provides a large specific surface area, serving as a catalytic site and gas diffusion channel for hydrogen and carbon dioxide. These technical features work in conjunction: hydrogen from high-temperature cracking rapidly moves to the second reaction chamber 24 under the selective action of the separation layer 211 due to the concentration gradient of hydrogen molecules; hydrogen separated by the separation layer 211 permeates through the reaction layer 212 to the second reaction chamber 24; and the alumina-material reaction layer 212, loaded with a nickel-based catalyst, promotes the synthesis of methane or methanol from hydrogen and carbon dioxide. This process not only removes hydrogen from the first reaction chamber 13 (facilitating a rightward shift in the dehydrogenation reaction equilibrium and improving conversion rate) but also provides a high-purity hydrogen source for the second reaction chamber 24. The combination of these two processes achieves integrated synergy between reaction and separation, resulting in multiple technical effects such as improved reaction rate, selectivity, and hydrogen utilization efficiency. This addresses the technical problems of thermodynamic equilibrium limitations and high energy consumption for product separation in traditional fixed-bed reactors.

[0032] In addition to the feasible embodiments described above, in a more preferred embodiment, to further adjust the reaction rates within the two reaction chambers, the first reaction chamber 13 is filled with a platinum-based noble metal catalyst as a supplementary catalyst; the second reaction chamber 24 is filled with nickel and aluminum oxide as supplementary catalysts. The two types of catalysts function in their respective optimal reaction chambers: the platinum-based catalyst specifically catalyzes the production of propylene and hydrogen, while the nickel catalyst specifically catalyzes the consumption of hydrogen and releases heat. They are linked by the hydrogen and heat flows transferred through the tubular ceramic membrane 21. This coordination allows the two reactions to proceed efficiently under their respective optimal catalytic conditions and achieves energy complementarity through heat transfer. Therefore, this application achieves the technical effect of improving propylene yield and maintaining system heat balance, preventing the technical problems of a single catalyst being unable to handle both reactions simultaneously and the complexity of heat management.

[0033] It should be noted that, in addition to propylene, propane cracking also produces small amounts of hydrocarbons such as ethylene and methane.

[0034] Based on the above embodiments, in a more preferred embodiment, the second reaction chamber 24 is filled with an inert gas to maintain an inert gas atmosphere. This arrangement allows the inert gas, acting as a diluent and atmospheric gas, to effectively eliminate active impurities such as oxygen due to its chemical inertness, preventing catalyst oxidation and deactivation or unnecessary deep oxidation reactions. Maintaining an inert environment in the second reaction chamber 24 before or during reaction start-up ensures that the carbon dioxide methanation reaction can proceed under pure and controllable conditions, protecting the nickel catalyst and improving the efficient utilization of syngas. This feature, combined with the selective hydrogen permeation function of the membrane, ensures that the hydrogen entering the second reaction chamber 24 is used efficiently and directionally for the target synthesis reaction. This achieves the technical effects of ensuring long-term stable operation of the catalyst, improving process safety, and enhancing product purity.

[0035] In one feasible embodiment, the material of the separation layer 211 is... Where x, y, and z represent the mole fractions of silicon, aluminum, and phosphorus, respectively, with x ranging from 0.01 to 0.98, y from 0.01 to 0.6, and z from 0.01 to 0.52, and x + y + z = 1. This embodiment defines the material of the separation layer 211, whose crystal structure provides a regular ion transport channel. Furthermore, the crystal structure of the separation layer 211 contains a molecular sieve composed of eight ring pores, with a pore size of 0.38 nm × 0.38 nm. With this configuration, the dense separation layer 211, constructed from this material, can act as a highly efficient hydrogen molecule (proton) conductor under high-temperature operating conditions, allowing hydrogen to migrate rapidly in ionic form while almost completely blocking other gas molecules. This provides a material basis for the ultra-high selective transport of hydrogen from the first reaction chamber 13 to the second reaction chamber 24. Combined with the structure of the reaction layer 212, efficient coupling of reaction and separation at the molecular scale is achieved. Thus, hydrogen separation and purification are realized at high temperature and normal pressure.

[0036] Furthermore, the pore size is larger than the kinetic diameter of a hydrogen molecule (approximately 0.289 nm), but much smaller than the molecular diameters of nitrogen, methane, and carbon dioxide, thus achieving spatial sieving of hydrogen molecules by size. In this embodiment, the molecular sieve with precise pores serves as the core structure of the separation layer 211. Combined with the surface adsorption and diffusion characteristics of the material itself, it not only ensures extremely high hydrogen selectivity through size exclusion effect but may also accelerate hydrogen transport through surface diffusion mechanisms within the pores. Coupled with a specific operating temperature, hydrogen can pass through efficiently and selectively, while other reactants and products are strictly confined within their respective reaction chambers. While maintaining high selectivity, a considerable hydrogen permeation flux is obtained, which helps to resolve the technical contradiction of poor selectivity in porous membranes and low flux in traditional dense membranes, making it difficult to match the reaction rate.

[0037] In addition to the above embodiments, in one feasible embodiment, the outer casing 1 is provided with a first connecting pipe 22 and a second connecting pipe 23 respectively sealed and connected to both ends of the tubular ceramic membrane 21; the outer periphery of the first connecting pipe 22 and the outer periphery of the second connecting pipe 23 are both sealed and connected to the inner wall of the outer casing 1. The first connecting pipe 22 is used to introduce carbon dioxide, and the second connecting pipe 23 is used to discharge the material synthesized from carbon dioxide and hydrogen. With this configuration, the first connecting pipe 22 and the second connecting pipe 23 achieve independent connection between the material (carbon dioxide feed and product outlet) of the second reaction chamber 24 and the external pipeline; the sealed connections at each point ensure reliable isolation between the first reaction chamber 13 and the second reaction chamber 24, as well as between them and the outside world. This structure fixes both ends of the tubular ceramic membrane 21 and leads it out of the outer casing 1, while simultaneously, through strict sealing, completely physically isolates the internal space of the outer casing 1 (first reaction chamber 13) from the internal space of the ceramic tube (second reaction chamber 24). This makes the methane / propylene flow and the carbon dioxide / synthesis gas flow two independent, non-intersecting flow paths. It enables independent transport of reactants and collection of products in the dual chambers, and fundamentally prevents gas cross-contamination that could lead to decreased reaction efficiency or safety issues.

[0038] In one feasible embodiment, the reaction temperature of the first reaction chamber 13 and the second reaction chamber 24 is between 300°C and 400°C, and the reaction pressure of both chambers is 1 standard atmosphere. This specific temperature setting simultaneously satisfies the requirement for a reasonable reaction rate in the propane dehydrogenation reaction and the operating window where the carbon dioxide methanation reaction releases sufficient heat and the molecular sieve membrane exhibits good hydrogen permeability. The atmospheric pressure (1 atm) operating condition greatly simplifies the pressure requirements on the reactor shell and auxiliary equipment. Under the aforementioned temperature and atmospheric pressure conditions, utilizing the self-heating characteristics of the coupled reaction within the membrane reactor, the system can spontaneously maintain this highly efficient reaction range without the need for complex high-pressure or ultra-high-temperature external equipment. The matching of temperature and membrane performance ensures rapid hydrogen transport and efficient reaction. The atmospheric pressure condition reduces energy consumption and safety risks. This achieves efficient production under mild and safe operating conditions, significantly reducing equipment investment and operating costs.

[0039] In one feasible embodiment, the inert gas is nitrogen. Nitrogen, as an readily available, inexpensive, and chemically extremely stable inert gas, is the most economical and practical medium for achieving and protecting the inert atmosphere of the second reaction chamber 24. Furthermore, using nitrogen as both a protective gas and a purge gas to remove air before the reaction and maintain an inert environment during the reaction aligns perfectly with the reactor's atmospheric pressure design. This ensures the effectiveness of the inert gas technology while minimizing raw material costs. Thus, effective reaction chamber atmosphere control is achieved with minimal operating costs, improving the overall economic efficiency of the process.

[0040] Another object of the present invention is to provide a method for the simultaneous preparation of propylene and methane, including the atmospheric pressure self-heating bifunctional membrane reactor described above.

[0041] The method for simultaneously preparing propylene and methane also includes the following steps: S1. Inert gas is introduced into the second reaction chamber to maintain an inert gas atmosphere inside the tubular ceramic membrane; S2. Propane is introduced into the first reaction chamber, and carbon dioxide is introduced into the second reaction chamber; S3. Propane is cracked in the first reaction chamber to release hydrogen gas, which is separated by a tubular ceramic membrane and enters the second reaction chamber, where it reacts with carbon dioxide in the second reaction chamber to produce methane. S4. Control the rate of carbon dioxide introduction to maintain the temperature of the first reaction chamber between 300℃ and 400℃.

[0042] Compared to existing technologies, the method for simultaneously preparing propylene and methane in this invention possesses all the advantages of the aforementioned atmospheric pressure self-heating bifunctional membrane reactor, which will not be elaborated upon here. Furthermore, in the method for simultaneously preparing propylene and methane in this invention, step S1 lays the foundation for a safe and efficient reaction; step S2 initiates two parallel reaction processes; step S3 describes the core mechanism of reaction-separation coupling; and step S4 achieves heat balance and stable control of the process. The combination of these steps constitutes a complete operating cycle. First, an inert environment is established to ensure safety and catalytic activity. Then, the two reactions are initiated simultaneously with the feed, utilizing the membrane to achieve directional hydrogen migration and reaction coupling. Finally, by adjusting a simple variable—the feed parameter (carbon dioxide rate)—the reaction temperature of the entire system can be controlled using the intensity of the exothermic reaction. This combination makes the complex bifunctional reaction coupling process simple and controllable. This achieves the technical effect of making the entire self-heating membrane reactor process easy to start, stable in operation, and easy to control, thus helping to solve the technical problems of complex operation, parameter sensitivity, and difficulty in stable operation that often exist in multi-reaction coupling systems.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bifunctional membrane reactor with self-heating at atmospheric pressure, characterized in that, include: The outer shell is provided with an inlet and an outlet. Propane enters the outer shell from the inlet, and the reaction products after propane dehydrogenation are discharged from the outlet. The membrane module includes a tubular ceramic membrane disposed within the housing, with both ends of the tubular ceramic membrane extending to the outside of the housing. The outer wall of the tubular ceramic membrane and the inner wall of the housing enclose a first reaction chamber, and the interior of the tubular ceramic membrane forms a second reaction chamber. Propane in the first reaction chamber is decomposed into propylene and hydrogen, and hydrogen enters the second reaction chamber through the tubular ceramic membrane. Carbon dioxide is introduced into one end of the tubular ceramic membrane, and the material synthesized from carbon dioxide and hydrogen is discharged from the other end of the tubular ceramic membrane; the carbon dioxide and hydrogen undergo a synthesis reaction in the second reaction chamber, which releases heat to heat the dehydrogenation in the first reaction chamber.

2. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 1, characterized in that, The tubular ceramic membrane includes a separation layer and a reaction layer stacked from the outside to the inside. A second reaction chamber is formed within the reaction layer, and a first reaction chamber is formed between the separation layer and the outer shell. The separation layer is a dense molecular sieve layer that allows only hydrogen molecules to pass through. The reaction layer includes a loose and porous alumina support and a nickel-based catalyst loaded on the alumina support.

3. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 2, characterized in that, The first reaction chamber is filled with a platinum-based noble metal catalyst as a supplementary catalyst; the second reaction chamber is filled with nickel and aluminum oxide as supplementary catalysts.

4. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 1, characterized in that, The second reaction chamber is filled with an inert gas to maintain an inert gas atmosphere.

5. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 2, characterized in that, The material of the separation layer is In this equation, x, y, and z represent the mole fractions of silicon, aluminum, and phosphorus, respectively, with x ranging from 0.01 to 0.98, y ranging from 0.01 to 0.6, and z ranging from 0.01 to 0.52, and x + y + z = 1.

6. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 5, characterized in that, The separation layer contains a molecular sieve with eight ring pores, the pore size of which is 0.38 nm. 0.38nm.

7. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 2, characterized in that, The outer casing is provided with a first connecting pipe and a second connecting pipe that are respectively sealed and connected to both ends of the tubular ceramic membrane; the outer periphery of the first connecting pipe and the outer periphery of the second connecting pipe are both sealed and connected to the inner wall of the outer casing. The first connecting pipe is used to introduce carbon dioxide, and the second connecting pipe is used to discharge the material synthesized from carbon dioxide and hydrogen.

8. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 2, characterized in that, The reaction temperature of the first reaction chamber and the second reaction chamber is between 300°C and 400°C, and the reaction pressure of the first reaction chamber and the second reaction chamber is 1 standard atmosphere.

9. The atmospheric pressure self-heating bifunctional membrane reactor as described in claim 4, characterized in that, The inert gas is made of nitrogen.

10. A method for simultaneously preparing propylene and methane, characterized in that, Based on the atmospheric pressure self-heating bifunctional membrane reactor as described in any one of claims 1 to 9, the method for simultaneously producing propylene and methane further includes the following steps: S1. Inert gas is introduced into the second reaction chamber to maintain an inert gas atmosphere inside the tubular ceramic membrane; S2. Propane is introduced into the first reaction chamber, and carbon dioxide is introduced into the second reaction chamber; S3. Propane is cracked in the first reaction chamber to release hydrogen gas, which is separated by a tubular ceramic membrane and enters the second reaction chamber, where it reacts with carbon dioxide in the second reaction chamber to produce methane. S4. Control the rate of carbon dioxide introduction to maintain the temperature of the first reaction chamber between 300℃ and 400℃.

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