Methane coupling ethylene production method and reaction device using multi-stage oxygen feeding

Abstract

This invention discloses a method and apparatus for the production of ethylene from methane via multi-stage oxygen feeding, relating to the field of acyclic or carbocyclic compound production technology. The method includes: mixing methane with water vapor and introducing it into a riser, where it mixes with catalyst particles within the riser to form a gas-solid mixture, which is then conveyed axially along the riser; introducing oxygen into the riser through multiple oxygen inlet points, wherein the multiple oxygen inlet points are spaced apart axially along the riser, allowing the oxygen to mix with the gas-solid mixture in stages within the riser and undergo a methane oxidative coupling reaction to generate a product containing ethylene. This invention, by introducing oxygen in stages, effectively reduces the local oxygen concentration in each feeding zone while maintaining a constant total oxygen intake, increasing the local alkoxy ratio (CH4 / O2), thereby suppressing the deep oxidation side reactions of methyl radicals and the product ethylene, and improving methane conversion, ethylene selectivity, and ethylene yield.

Description

Technical Field

[0001] This invention relates to the field of acyclic or carbocyclic compound production technology, and in particular to a method and reaction apparatus for producing ethylene from methane using multi-stage oxygen feeding. Background Technology

[0002] Oxidative coupling of methane to ethylene is a technology of strategic value in the chemical industry. It involves the activation of methane molecules with oxygen, achieving C-C coupling to produce ethylene; this reaction is a strongly exothermic process. In existing technologies, the oxygen feed method in the reactor is generally a single-point, one-time injection. This feeding method has the following drawbacks: First, the local oxygen concentration is too high: the one-time injection of oxygen causes a sudden increase in the local oxygen concentration in the feeding area, resulting in an excessively low alkoxy ratio (the molar ratio of methane to oxygen). This promotes a deep oxidation reaction between methyl radicals and oxygen, generating a large amount of CO. x (CO / CO2) severely inhibits the formation of C2 hydrocarbons (ethylene, ethane).

[0003] Second, the heat of reaction is concentrated: the exothermic reaction is concentrated in the feed area, forming a localized concentrated heat release, which makes the local temperature too high, aggravates the secondary oxidation of ethylene, and accelerates the sintering and deactivation of the catalyst, affecting the stability of the unit operation.

[0004] Patent application number 201810430243.7 discloses a reaction apparatus and method for producing ethylene via methane oxidative coupling. It employs a fluidized bed reactor and utilizes multiple oxygen distributors located at the top, middle, and bottom of the fluidized zone for multi-stage oxygen supplementation. This segmented oxygen supplementation adjusts the methane-to-oxygen ratio to suppress deep oxidation. However, the generated ethylene has an excessively long residence time in the fluidized bed, making it prone to secondary deep oxidation reactions with oxygen, reducing ethylene selectivity. Simultaneously, some methane and oxygen undergo non-selective gas-phase combustion reactions due to excessive backmixing and residence time, generating large amounts of CO. x This results in waste of raw materials and increases the burden of separation. Summary of the Invention

[0005] This invention provides a method and apparatus for the coupling production of ethylene from methane using multi-stage oxygen feeding, aiming to solve the technical problem of deep oxidation of products caused by single-point oxygen intake.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for producing ethylene from methane using multi-stage oxygen feeding, comprising the following steps: Methane is mixed with water vapor and introduced into the riser, where it mixes with catalyst particles inside the riser to form a gas-solid mixture, which is then transported axially along the riser. Oxygen is introduced into the riser through multiple oxygen inlet points, which are spaced apart along the axial direction of the riser, so that the oxygen and the gas-solid mixture are mixed in sections within the riser and undergo a methane oxidative coupling reaction to generate a product containing ethylene.

[0007] Compared to single-stage oxygen injection, this invention introduces oxygen in stages while maintaining the same total oxygen consumption. This allows the oxygen to mix with the gas-solid mixture in stages within the riser, resulting in a methane oxidative coupling reaction. Under the premise of constant total oxygen intake, this effectively reduces the local oxygen concentration in each feeding zone and increases the local alkoxy ratio (CH4 / O2), thereby suppressing the deep oxidation side reactions of methyl radicals and the product ethylene. At the same time, the staged oxygen injection disperses the heat of reaction along the reactor axis, avoiding the local hot spot problem caused by the reaction being concentrated in the feeding zone in traditional processes. This prevents the heat of reaction from aggravating the deep oxidation of ethylene, reduces the risk of catalyst sintering and deactivation, and extends the catalyst's lifespan.

[0008] Meanwhile, the reaction takes place inside the riser, where gas and solid flow upwards in parallel, resulting in high gas-solid contact efficiency and short contact time. Compared to fluidized bed reactors, riser reactors exhibit minimal gas-solid backmixing, which helps reduce secondary oxidation of the product ethylene.

[0009] Preferably, the total oxygen intake at all the oxygen intake points is not less than 1.5 of the total alkane-oxygen ratio of methane, and the local alkane-oxygen ratio at each oxygen intake point is not less than 2.

[0010] By controlling the total alkoxy ratio to no less than 1.5, sufficient methane is maintained relative to oxygen in the reaction system, providing a sufficient raw material basis for the coupling reaction of methyl radicals. At the same time, the local alkoxy ratio at each oxygen injection point is controlled to no less than 2, further ensuring that the oxygen concentration in each reaction region is at a low level, which significantly inhibits the deep oxidation reaction.

[0011] Preferably, along the conveying direction of the gas-solid mixture, the oxygen intake at the first oxygen inlet point is no more than 50% of the total oxygen intake at all oxygen inlet points.

[0012] By controlling the first-stage oxygen intake to within 50% of the total oxygen intake, the sudden increase in local oxygen concentration and violent exothermic reaction caused by excessive oxygen injection in the early stages of the reaction are avoided. This design ensures that methane is in a high alkane-to-oxygen ratio environment when it first enters the riser, which is conducive to the mild activation of methane and the generation of methyl radicals. This creates a good reaction foundation for the gradual introduction of oxygen in subsequent stages, effectively suppresses the initial deep oxidation reaction, and improves the overall C2 selectivity.

[0013] Preferably, the oxygen inlet points are distributed at intervals along the axial direction of the riser pipe, and the oxygen inlet ratio of the three oxygen inlet points is 0.5:0.25:0.25 along the conveying direction of the gas-solid mixture.

[0014] A three-stage oxygen inlet system with an oxygen distribution ratio of 0.5:0.25:0.25 was experimentally verified as the optimal process conditions. Under this ratio, the methane conversion rate reached 62.8%, the C2 selectivity reached 50.9%, and the C2 yield reached 31.9%, representing improvements of 5.7, 11.7, and 9.5 percentage points respectively compared to a single-stage oxygen inlet system. This ratio achieved a rational distribution of oxygen along the reactor axis, ensuring that the alkane-to-oxygen ratio in each reaction zone was within the optimal range. This maximized the balance between the competition between methane activation and deep oxidation, resulting in optimal overall reaction performance.

[0015] Preferably, the ethylene-containing product generated in the riser is subjected to gas-solid separation to obtain an ethylene-containing gas mixture and catalyst particles. The separated catalyst particles are regenerated by a regenerator and then recycled back to the riser. The separated ethylene-containing gas mixture is subjected to gas separation to obtain ethylene.

[0016] Gas-solid separation enables rapid separation of reaction products from the catalyst, avoiding prolonged contact between the products and the catalyst in the high-temperature zone and reducing secondary oxidation losses of ethylene. The separated catalyst is regenerated to remove adsorbed active oxygen and then recycled back to the riser, achieving continuous catalyst recycling, reducing catalyst consumption costs, and ensuring stable catalyst activity within the reaction system.

[0017] Preferably, the catalyst particles regenerated by the regenerator are stripped by a stripper and then returned to the riser.

[0018] A stripping step is added before the catalyst returns to the riser. Water vapor is used to replace the trace amounts of hydrocarbons (methane, ethane, ethylene, etc.) remaining in the pores and on the surface of the catalyst particles. This effectively prevents the non-selective oxidation of residual hydrocarbons after they return to the reactor with the catalyst, avoids product loss, and further purifies the catalyst surface, ensuring the reaction selectivity of the recycled catalyst.

[0019] Preferably, the unreacted methane obtained from the gas separation of the ethylene-containing gas mixture is mixed with fresh methane and water vapor and then reintroduced into the riser. The carbon oxide gas obtained by further gas separation of the ethylene-containing gas mixture obtained from gas-solid separation is introduced into the regenerator. The water vapor obtained from the gas separation of the ethylene-containing gas mixture is fed into the stripper.

[0020] The recycling of unreacted methane improves feedstock utilization and reduces fresh methane consumption; carbon oxides (CO / CO2) are introduced into the regenerator for deoxygenation and regeneration of catalyst particles, achieving self-circulation of regenerated gas and reducing the need for external reducing gases; steam is introduced into the stripper, using the water generated in the reaction as the stripping medium, reducing the consumption of externally supplied steam. This recycling design enables the recycling of reaction byproducts.

[0021] A second aspect of the present invention provides a reaction apparatus for implementing the method for producing ethylene by methane coupling using multi-stage oxygen feeding as described in any embodiment of the first aspect, comprising a riser, wherein a plurality of oxygen nozzles are provided on the sidewall of the riser, and the plurality of oxygen nozzles are spaced apart along the axial direction of the riser.

[0022] Multiple sets of oxygen nozzles spaced along the axial direction inject oxygen into the riser in segments, enabling precise control of the oxygen concentration distribution and the heat release distribution within the reactor.

[0023] Preferably, it further includes a regenerator, a stripper, a first gas separator, a second gas separator, a first cyclone separator, and a second cyclone separator; The stripper is located at the bottom of the regenerator and communicates with the inner cavity of the regenerator; the outlet end of the stripper is connected to the inlet end of the riser. The outlet end of the riser pipe is connected to the inlet of the first cyclone separator, the riser pipe of the first cyclone separator is connected to the first gas separator, and the cyclone material leg of the first cyclone separator is connected to the inner cavity of the regenerator. The carbon oxide outlet of the first gas separator is connected to the inner cavity of the regenerator, the water vapor outlet of the first gas separator is connected to the inner cavity of the stripper, and the methane outlet of the first gas separator is connected to the inlet end of the riser. The top of the regenerator is connected to the inlet of the second cyclone separator, the riser of the second cyclone separator is connected to the second gas separator, and the cyclone material leg of the second cyclone separator is connected to the inner cavity of the regenerator. The carbon oxide outlet of the second gas separator is connected to the inner cavity of the regenerator.

[0024] This device forms a complete catalyst recycling and gas circulation loop. Through the orderly connection of each unit, it realizes continuous catalyst recycling, efficient separation and recycling of reaction products and by-products.

[0025] Preferably, the outlet direction of the oxygen nozzle is perpendicular to the axis of the riser tube; Alternatively, the oxygen nozzle may be inclined toward the inlet end of the riser tube. Alternatively, the oxygen nozzle may be inclined toward the outlet end of the riser tube.

[0026] By flexibly selecting the injection direction of the oxygen nozzle, the mixing effect of oxygen and gas-solid mixture can be optimized according to different operating conditions: vertical injection can enhance radial mixing, allowing oxygen to be quickly dispersed throughout the entire cross-section; tilting towards the inlet end can form a local reflux zone, enhancing the mixing intensity; tilting towards the outlet end can achieve forward and gentle mixing. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the reaction apparatus of the present invention.

[0029] Figure 2 This is a schematic diagram showing the direction of the oxygen nozzle's outlet perpendicular to the axis of the riser pipe. The arrows in the diagram indicate the flow direction of the gas-solid mixture and the oxygen flow direction within the riser pipe, respectively.

[0030] Figure 3 This is a schematic diagram showing the oxygen nozzle's outlet direction tilted towards the inlet end of the riser pipe. The arrows in the diagram indicate the flow direction of the gas-solid mixture and the oxygen flow direction within the riser pipe, respectively.

[0031] Figure 4 This is a schematic diagram showing the oxygen nozzle's outlet direction tilted towards the riser's outlet end. The arrows in the diagram indicate the flow direction of the gas-solid mixture and the oxygen flow direction within the riser, respectively.

[0032] Figure 5 Bar chart showing experimental data on methane conversion rate, C2 selectivity, and C2 yield for different oxygen inlet methods.

[0033] Explanation of reference numerals in the attached figures: Riser 1, Regenerator 2, Stripper 3, Oxygen Nozzle 4, First Gas Separator 5, Second Gas Separator 6, First Cyclone Separator 7, Second Cyclone Separator 8, Oxygen Compressor 9, Pre-lift Section 10, Main Inlet Pipe for Raw Material Gas 11, First Distributor 12, Flow Guide 13, Catalyst Circulation Pipe 14, Flow Control Valve 15, Second Distributor 16, Third Distributor 17. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The following are some embodiments of the method for producing ethylene from methane using multi-stage oxygen feeding according to the present invention.

[0037] refer to Figure 1 In some embodiments, a multi-stage oxygen-fed methane coupling method for producing ethylene includes the following steps: Methane and water vapor are mixed and introduced into riser 1, where they mix with catalyst particles to form a gas-solid mixture, which is then conveyed axially along riser 1. It should be noted that the volume ratio of methane to water vapor is adjusted according to the catalyst type and reaction temperature.

[0038] With the total oxygen consumption remaining constant, oxygen is introduced into riser 1 through multiple oxygen inlet points, which are spaced apart along the axial direction of riser 1. This allows the oxygen and gas-solid mixture to mix in stages within riser 1, resulting in a methane oxidative coupling reaction to produce a product containing ethylene. It should be noted that the number of oxygen inlet points is not limited to a fixed number of stages and can be set to 2, 3, 4, or more stages depending on the height of riser 1, the catalyst circulation rate, and the target product distribution.

[0039] In some embodiments, the total oxygen intake at all oxygen inlet points is not less than 1.5 of the total alkoxy ratio of methane. For example, the total alkoxy ratio can be 1.5, 1.6, 1.8, 2.0, 2.5 or higher. When the catalyst activity is high, a higher total alkoxy ratio can be used to further suppress deep oxidation; when the catalyst activity is low, a lower total alkoxy ratio can be used to ensure sufficient methane conversion.

[0040] The local alkane-to-oxygen ratio at each oxygen inlet point should not be less than 2. It should be noted that the local alkane-to-oxygen ratio refers to the molar ratio of methane to oxygen in the local mixed gas in the area where oxygen is injected after oxygen is introduced from that inlet point. The local alkane-to-oxygen ratio can be controlled by adjusting the amount of oxygen injected at the corresponding inlet point.

[0041] Optionally, the local alkoxide ratio at each oxygen inlet point can be the same or different. For example, the local alkoxide ratio in the first stage can be set higher to minimize initial deep oxidation; the local alkoxide ratio in subsequent stages can be appropriately reduced to ensure the overall conversion rate of methane. It should be noted that a local alkoxide ratio of not less than 2 is an experimentally verified preferred lower limit, but under special catalyst systems, the local alkoxide ratio can also be lower than 2, such as 1.9, 1.8 or even lower, as long as the goal of simultaneously improving conversion rate and selectivity can be achieved.

[0042] In some embodiments, along the conveying direction of the gas-solid mixture, the oxygen intake at the first oxygen inlet point does not exceed 50% of the total oxygen intake at all oxygen inlet points, and the remaining oxygen is injected by subsequent stages. The first oxygen inlet point is the one closest to the inlet end of riser 1.

[0043] It should be noted that the upper limit for the oxygen intake at the first oxygen inlet point is set to avoid deep oxidation caused by excessively high oxygen concentration in the early stages of the reaction. However, depending on the oxidation resistance and exothermic characteristics of different catalyst systems, this upper limit can be appropriately relaxed to 60% or 65%, as long as it ensures that no local hot spots are formed in the early stages of the reaction and that the C2 selectivity is not lower than that of single-stage oxygen inlet. For example, for catalyst systems with mild exothermic reactions, the oxygen intake at the first oxygen inlet point can be increased to 55%, and the number of oxygen inlet points can be appropriately reduced; for systems with severe exothermic reactions, the oxygen intake at the first oxygen inlet point should be controlled below 40%, and correspondingly, the number of oxygen inlet points needs to be appropriately increased.

[0044] In some embodiments, three oxygen inlet points are distributed at intervals along the axial direction of the riser pipe 1, and the oxygen inlet ratio of the three oxygen inlet points is 0.5:0.25:0.25 along the conveying direction of the gas-solid mixture.

[0045] It should be noted that fluidized beds exhibit strong gas-solid backmixing, long gas-solid contact time, and a wide operating window, thus requiring lower uniformity and precise proportioning of oxygen injection. Even with slight deviations in the flow rates of each stage of the multi-stage oxygen distributor, macroscopic mixing and conversion of reactants can still be achieved due to the intense turbulence and long residence time within the bed. Compared to fluidized beds, the riser 1 of this invention offers higher gas-solid contact efficiency and shorter contact time. This invention employs a segmented oxygen supply method, which avoids over-reaction and reduces byproduct formation. However, multi-stage oxygen supply also significantly disturbs the high-speed airflow field within riser 1. If the oxygen proportioning at each stage is not precisely controlled, it will not only fail to suppress deep oxidation but also disrupt the gas-solid contact state, leading to deep oxidation (generating large amounts of CO). x If methane conversion is incomplete, energy loss will increase. Therefore, the oxygen intake ratio at each stage must be precisely adjusted, and the control conditions are more stringent.

[0046] To address the high-speed, short-contact characteristics of the riser 1 reactor, a ratio of 0.5:0.25:0.25 was used to achieve a reasonable distribution of oxygen along the reactor axis, ensuring that the alkane-oxygen ratio in each reaction zone was within the optimal range. This maximized the balance between the competition between methane activation and deep oxidation, resulting in optimal overall reaction performance. Consequently, high conversion and high selectivity were achieved simultaneously in the demanding reactor, riser 1.

[0047] For example, in a set of comparative experiments, when a ratio of 0.5:0.25:0.25 was used, the reference... Figure 5 The methane conversion rate was 62.8%, the C2 selectivity was 50.9%, and the C2 yield was 31.9%, which were 5.7, 11.7, and 9.5 percentage points higher than those of the primary feed, respectively.

[0048] It should be noted that the ratio of 0.5:0.25:0.25 is the optimal value verified by experiments, but it is not the only usable ratio. Depending on different catalyst systems, reaction temperatures, and target product distributions, other ratios can be used. When the methane conversion rate is low, the oxygen inlet ratio at the first oxygen inlet point can be appropriately increased, for example, to 0.6:0.2:0.2, to enhance the initial reaction. When the C2 selectivity is low, the oxygen inlet ratio at the first oxygen inlet point can be appropriately decreased, for example, to 0.4:0.3:0.3, to suppress deep oxidation.

[0049] In some embodiments, the products generated in the riser (containing ethylene, unreacted methane, water vapor, CO / CO2, and catalyst particles) undergo gas-solid separation to obtain an ethylene-containing gas mixture and catalyst particles. The separated catalyst particles are regenerated in regenerator 2 and then recycled back to riser 1. The separated ethylene-containing gas mixture undergoes further gas separation to obtain ethylene. Exemplarily, the products generated in the riser are subjected to gas-solid separation using a first cyclone separator 7 to obtain catalyst particles and an ethylene-containing gas mixture. The catalyst particles are discharged from the cyclone feed leg of the first cyclone separator 7, and the ethylene-containing gas mixture undergoes further separation. This subsequent separation of the ethylene-containing gas mixture is a conventional technique in the art. The separated catalyst particles are contacted with a CO / CO2 mixture in regenerator 2 to remove surface-adsorbed active oxygen, and then returned to riser 1 for recycling via catalyst circulation pipe 14.

[0050] Optionally, multiple first cyclone separators 7 can be connected in series to perform multi-stage separation of the products generated in the riser pipe to improve the separation effect.

[0051] Furthermore, the catalyst particles regenerated by the regenerator 2 are fed into the stripper 3, where they are mixed with steam. The steam displaces the trace amounts of hydrocarbons (such as methane, ethane, ethylene, etc.) remaining in the pores and on the surface of the catalyst particles. The catalyst particles stripped by the stripper 3 are then returned to the riser 1 for recycling.

[0052] It should be noted that the oxidative coupling reaction between methane and oxygen in riser 1 is a strongly exothermic reaction. Since the specific heat capacity of the catalyst particles is greater than that of the gas, the catalyst particles absorb this heat. This heat is then exchanged with the CO / CO2 mixture in regenerator 2 and with water vapor in stripper 3. The catalyst particles release this heat, which is ultimately discharged with the gas. Therefore, during the circulation process, the catalyst can carry away the heat generated by the reaction, keeping the temperature inside riser 1 essentially constant. In other words, the circulation of the catalyst particles not only catalyzes the reaction but also acts as a heat carrier for heat transfer.

[0053] In some embodiments, the unreacted methane obtained from the gas-solid separation of the ethylene-containing gas mixture is mixed with fresh methane and water vapor and then reintroduced into riser 1. It should be noted that the total amount of unreacted methane and fresh methane should be kept substantially constant in proportion to the water vapor. For example, the unreacted methane and fresh methane are mixed and the flow rate is uniformly measured to control the ratio of methane to water vapor.

[0054] The ethylene-containing gas mixture obtained from gas-solid separation is further separated into carbon oxide-containing gas, which is then fed into regenerator 2. The carbon oxide-containing gas mainly consists of CO and CO2. The carbon oxide-containing gas is fed into regenerator 2 through a distributor at the bottom of regenerator 2. The catalyst particles settle downwards from the top of regenerator 2. The rising carbon oxide-containing gas comes into countercurrent contact with the falling catalyst particles, and the carbon oxide-containing gas removes the active oxygen adsorbed on the catalyst surface.

[0055] Furthermore, the regenerator 2 is equipped with a gas outlet at the top. The gas discharged from the gas outlet is separated by the second cyclone separator 8. The catalyst particles return from the cyclone feed leg of the second cyclone separator 8 to the inner cavity of the regenerator 2. The separated gas portion is further separated by a gas separator to obtain a relatively pure carbon oxide-containing gas, which is then returned to the inner cavity of the regenerator 2 for circulation. Optionally, only one second cyclone separator 8 can be provided, or two or more can be connected in series.

[0056] The water vapor obtained from the gas separation of the ethylene-containing gas mixture is introduced into the stripper 3 through a water vapor distributor. Optionally, if the amount of water vapor generated by the product gas separation unit is insufficient, external water vapor can be supplied; if there is an excess of water vapor, the excess portion can be discharged or used for circulation into the feed end of the riser 1.

[0057] The following provides some embodiments of the reaction apparatus of the present invention.

[0058] refer to Figure 1 In some embodiments, the reaction apparatus includes a riser 1, with multiple sets of oxygen nozzles 4 disposed on the sidewall of the riser 1 at intervals along the axial direction of the riser 1. Optionally, each set of oxygen nozzles 4 includes multiple nozzles, evenly distributed circumferentially around the axis of the riser 1. For example, the number of nozzles in each set can be 2, 3, 4, 6, or 8. Each nozzle is connected to an oxygen compressor 9 via an oxygen pipeline. The oxygen compressor 9 introduces oxygen into the inner cavity of the riser 1 through the oxygen pipeline and the oxygen nozzles 4, where it mixes with the gas-solid mixture composed of methane, water vapor, and catalyst particles. Each set of oxygen nozzles 4 corresponds to one oxygen inlet point.

[0059] Optionally, refer to Figure 2 The outlet direction of the oxygen nozzle 4 is perpendicular to the axis of the riser pipe 1, that is, the oxygen is injected radially along the riser pipe 1, which is conducive to the rapid penetration of oxygen into the central area of ​​the riser pipe 1 and enhances radial mixing so that the oxygen is quickly dispersed throughout the entire cross section.

[0060] Or, refer to Figure 3 The oxygen nozzle 4 is inclined towards the inlet end of the riser pipe 1, so that the direction of oxygen injection is opposite to that of the gas-solid mixture in the riser pipe 1, which enhances the turbulent mixing intensity of oxygen and gas-solid mixture and makes oxygen and gas-solid mixture mix quickly.

[0061] Or, refer to Figure 4 The oxygen nozzle 4 is inclined towards the outlet end of the riser pipe 1. This inclined arrangement allows the oxygen to be injected into the mainstream of the gas-solid mixture in the forward direction, resulting in a gentler mixing process and avoiding violent disturbances.

[0062] It should be noted that the nozzle direction at different oxygen inlet points can be set independently according to their location and functional requirements, and is not limited to using the same direction at all points. For example, along the conveying direction of the gas-solid mixture, the first oxygen inlet point should preferably use downward or vertical injection to enhance mixing, the second oxygen inlet point should preferably use vertical injection, and the third oxygen inlet point should preferably use upward injection to gently introduce oxygen.

[0063] Preferably, the inlet end of the riser 1 is provided with a pre-lifting section 10, which is cylindrical. The outlet end of the pre-lifting section 10 is connected to the inlet end of the riser 1. The inlet end of the pre-lifting section 10 is provided with a main feed gas inlet pipe 11, which is connected to a first distributor 12 located within the pre-lifting section 10. The mixture of methane and water vapor is uniformly introduced into the pre-lifting section 10 through the main feed gas inlet pipe 11 and the first distributor 12. Catalyst particles are introduced into the pre-lifting section 10 from the side wall and mixed with the mixture of methane and water vapor to form a gas-solid mixture. The pre-lifting section 10 allows methane, water vapor, and catalyst particles to be mixed in the pre-lifting section 10 before entering the riser 1, forming a stable gas-solid mixture in a piston flow state before entering the riser 1 for conveying.

[0064] Furthermore, a guide tube 13 is coaxially arranged within the pre-lifting section 10. The outer diameter of the guide tube 13 is smaller than the inner diameter of the pre-lifting section 10, creating an annular gap between the guide tube 13 and the pre-lifting section 10. Methane and water vapor introduced from the first distributor 12 partially enter the guide tube 13 and partially enter the annular gap. Catalyst particles enter the annular gap from the side wall of the pre-lifting section 10, forming an annular dense-phase turbulent fluidization region. The catalyst mixes violently within the annular gap, eliminating localized accumulation and ensuring uniform circumferential distribution of the particles. It then mixes with the methane and water vapor mixture within the guide tube 13, forming a uniform gas-solid mixture that enters the riser 1. The guide tube 13 effectively overcomes the flow distribution problem caused by the catalyst entering the pre-lifting section 10 from one side.

[0065] In some embodiments, the reaction apparatus further includes a regenerator 2, a stripper 3, a first gas separator 5, a second gas separator 6, a first cyclone separator 7, and a second cyclone separator 8; the connection relationships of each component are as follows: The stripper 3 is located at the bottom of the regenerator 2 and communicates with the inner cavity of the regenerator 2. The outlet end of the stripper 3 is connected to the inlet end of the riser pipe 1 via the catalyst circulation pipe 14. A flow control valve 15 is provided on the catalyst circulation pipe 14. Preferably, a conical transition section is provided between the regenerator 2 and the stripper 3, and between the stripper 3 and the catalyst circulation pipe 14.

[0066] The outlet end of the riser pipe 1 is connected to the inlet of the first cyclone separator 7. The riser pipe of the first cyclone separator 7 is connected to the first gas separator 5. The cyclone feed leg of the first cyclone separator 7 is connected to the inner cavity of the regenerator 2. The solid catalyst particles separated by the first cyclone separator 7 enter the inner cavity of the regenerator 2 through the cyclone feed leg. The ethylene-containing gas mixture separated by the first cyclone separator 7 enters the first gas separator 5 for further separation. The ethylene-containing gas mixture separated by the first cyclone separator 7 mainly includes the target product ethylene, unreacted methane, water vapor, and carbon oxides mainly composed of carbon monoxide and carbon dioxide. For example, the first cyclone separator 7 can be arranged in the upper part of the regenerator 2, and its cyclone feed leg can be directly inserted into the dense phase of the regenerator 2. The dense phase refers to the region with a high concentration of catalyst particles formed at the bottom of the regenerator 2 due to the downward settling of catalyst particles under gravity.

[0067] The first gas separator 5 has multiple outlets, including but not limited to a carbon oxide outlet, a water vapor outlet, a methane outlet, and an ethylene outlet. The ethylene separated by the first gas separator 5 is discharged through the ethylene outlet for further processing or collection.

[0068] The carbon oxide outlet of the first gas separator 5 is connected to the inner cavity of the regenerator 2. The carbon oxides (carbon monoxide and carbon dioxide) separated by the first gas separator 5 are introduced into the inner cavity of the regenerator 2 and mixed with the catalyst particles. This displaces the products and oxygen entrained in the catalyst particles, deoxygenating the catalyst particles and regenerating them for recycling. Preferably, a second distributor 16 is provided at the bottom of the regenerator 2, through which the carbon oxide gas uniformly enters the dense phase of the regenerator 2.

[0069] The steam outlet of the first gas separator 5 is connected to the inner cavity of the stripper 3. The steam separated by the first gas separator 5 is introduced into the stripper 3 and mixed with the deoxygenated and regenerated catalyst particles for further purification. Preferably, a third distributor 17 is provided at the bottom of the stripper 3, through which steam enters the stripper 3 evenly. Furthermore, the stripper 3 is provided with multi-stage grids, allowing the catalyst particles and steam to come into full contact under the turbulence of the grids.

[0070] The methane outlet of the first gas separator 5 is connected to the inlet end of the riser 1. The unreacted methane separated by the first gas separator 5 is mixed with fresh methane and water vapor, and then fed into the riser 1 after passing through the pre-lifting section 10, thus realizing the secondary utilization of the unreacted methane.

[0071] The top of the regenerator 2 is equipped with a gas outlet, which is connected to the inlet of the second cyclone separator 8. The gas-solid mixture in the regenerator 2 enters the second cyclone separator 8 for gas-solid separation. The riser pipe of the second cyclone separator 8 is connected to the second gas separator 6. The separated gas mixture is fed into the second gas separator 6 for further separation. The second gas separator 6 has a carbon oxide-containing outlet, which is connected to the inner cavity of the regenerator 2. The carbon oxide-containing gas separated by the second gas separator 6 is fed back into the inner cavity of the regenerator 2 via the second distributor 16 for recycling. The cyclone feed leg of the second cyclone separator 8 is connected to the inner cavity of the regenerator 2. The catalyst particles separated by the second cyclone separator 8 are returned to the regenerator 2 for regeneration and recycling.

[0072] Preferably, two or more second cyclone separators 8 are connected in series to perform multi-stage separation of the gas-solid mixture.

[0073] Preferably, the riser pipe of the second cyclone separator 8 has an exhaust branch pipe for discharging excess gas mixture.

[0074] It should be noted that the specific structure of the first gas separator 5 and the second gas separator 6 can be selected according to the separation requirements. Moreover, the first gas separator 5 and the second gas separator 6 are not limited to a single device, but can also be composed of multiple stages of devices.

[0075] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0076] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A method for producing ethylene from methane using multi-stage oxygen feeding, characterized in that, Includes the following steps: Methane and water vapor are mixed and introduced into the riser (1) to mix with the catalyst particles in the riser (1) to form a gas-solid mixture and be transported along the axial direction of the riser (1); Oxygen is introduced into the riser (1) through multiple oxygen inlet points, wherein the multiple oxygen inlet points are distributed at intervals along the axial direction of the riser (1), so that the oxygen and the gas-solid mixture are mixed in sections in the riser (1) and undergo a methane oxidative coupling reaction to generate a product containing ethylene.

2. The method for producing ethylene from methane using multi-stage oxygen feeding according to claim 1, characterized in that, The total oxygen intake at all the oxygen intake points and the total alkane-oxygen ratio of methane shall not be less than 1.5, and the local alkane-oxygen ratio at each of the oxygen intake points shall not be less than 2.

3. The method for producing ethylene from methane using multi-stage oxygen feeding according to claim 2, characterized in that, Along the conveying direction of the gas-solid mixture, the oxygen intake at the first oxygen inlet point shall not exceed 50% of the total oxygen intake at all oxygen inlet points.

4. The method for producing ethylene from methane using multi-stage oxygen feeding according to claim 3, characterized in that, The oxygen inlet points are distributed at intervals along the axial direction of the riser pipe (1). The oxygen inlet ratio of the three oxygen inlet points is 0.5:0.25:0.25 along the conveying direction of the gas-solid mixture.

5. The method for producing ethylene from methane using multi-stage oxygen feeding according to any one of claims 1-4, characterized in that, The ethylene-containing product generated in the riser is subjected to gas-solid separation to obtain an ethylene-containing gas mixture and catalyst particles. The separated catalyst particles are regenerated by a regenerator (2) and then recycled back to the riser (1). The separated ethylene-containing gas mixture is subjected to gas separation to obtain ethylene.

6. The method for producing ethylene from methane using multi-stage oxygen feeding according to claim 5, characterized in that, The catalyst particles regenerated by the regenerator (2) are stripped by the stripper (3) and then returned to the riser (1).

7. The method for producing ethylene from methane via multi-stage oxygen feeding according to claim 6, characterized in that, The unreacted methane obtained from the gas-solid separation of the ethylene-containing gas mixture is mixed with fresh methane and water vapor and then reintroduced into the riser (1). The carbon oxide gas obtained by gas separation of the ethylene-containing gas mixture obtained by gas-solid separation is introduced into the regenerator (2). The water vapor obtained by gas separation of the ethylene-containing gas mixture obtained from gas-solid separation is fed into the stripper (3).

8. A reaction apparatus, characterized in that, The method for producing ethylene by methane coupling using multi-stage oxygen feeding as described in any one of claims 1-7 includes a riser (1), on the side wall of which are provided multiple sets of oxygen nozzles (4), the multiple sets of oxygen nozzles (4) being distributed at intervals along the axial direction of the riser (1).

9. The reaction apparatus according to claim 8, characterized in that, It also includes a regenerator (2), a stripper (3), a first gas separator (5), a second gas separator (6), a first cyclone separator (7), and a second cyclone separator (8); The stripper (3) is located at the bottom of the regenerator (2) and communicates with the inner cavity of the regenerator (2). The outlet end of the stripper (3) is connected to the inlet end of the riser (1). The outlet end of the riser (1) is connected to the inlet of the first cyclone separator (7), the riser pipe of the first cyclone separator (7) is connected to the first gas separator (5), and the cyclone material leg of the first cyclone separator (7) is connected to the inner cavity of the regenerator (2). The carbon oxide outlet of the first gas separator (5) is connected to the inner cavity of the regenerator (2), the water vapor outlet of the first gas separator (5) is connected to the inner cavity of the stripper (3), and the methane outlet of the first gas separator (5) is connected to the inlet end of the riser (1). The top of the regenerator (2) is connected to the inlet of the second cyclone separator (8), the riser pipe of the second cyclone separator (8) is connected to the second gas separator (6), and the cyclone material leg of the second cyclone separator (8) is connected to the inner cavity of the regenerator (2). The carbon oxide outlet of the second gas separator (6) is connected to the inner cavity of the regenerator (2).

10. The reaction apparatus according to claim 8 or 9, characterized in that, The outlet direction of the oxygen nozzle (4) is perpendicular to the axis of the riser tube (1); Alternatively, the outlet direction of the oxygen nozzle (4) is inclined toward the inlet end of the riser tube (1); Alternatively, the outlet direction of the oxygen nozzle (4) is inclined toward the outlet end of the riser pipe (1).

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