Process and system for mixed low carbon alkane dehydrogenation

Abstract

This application provides a method and system for dehydrogenating mixed low-carbon alkanes. The method includes: subjecting a first low-carbon alkane to a first dehydrogenation reaction in a first reaction zone at a first reaction temperature T1 to generate a first reaction product containing a first low-carbon olefin; and subjecting a second low-carbon alkane to a second dehydrogenation reaction in a second reaction zone at a second reaction temperature T2 to generate a second reaction product containing a second low-carbon olefin; wherein 10℃≤T1-T2≤200℃. Using the technical solution of this application, the reaction conditions for dehydrogenation of different low-carbon alkanes can be independently controlled, ensuring that the dehydrogenated materials are under optimal reaction conditions. Furthermore, the regeneration system equipment, such as compressors and regeneration gas feed heaters, can be shared in this application, reducing redundant equipment investment and demonstrating significant technical advantages and promising application prospects.

Description

Technical Field

[0001] This application relates to the field of petrochemical technology, specifically to a method and system for dehydrogenating mixed low-carbon alkanes. Background Technology

[0002] Low-carbon olefins are essential organic raw materials with high demand and wide applications in the petrochemical industry. For example, propylene is a crucial basic petrochemical raw material with high demand and wide applications, second only to ethylene in total production. It is widely used in the production of polypropylene, acrylonitrile, propylene oxide, cumene / phenol / acetone / bisphenol A, acrylic acid and esters, epichlorohydrin, and other chemical products. Butene is also a widely used low-carbon olefin, used in the production of high-octane gasoline components, maleic anhydride, sec-butanol, heptene, polybutene, acetic anhydride, and other chemical products. Isobutylene can be used to produce methyl tert-butyl ether, ethyl tert-butyl ether, etc.

[0003] In recent years, with the rapid development of various industries, the demand for low-carbon olefins has been rising continuously, and a large number of production facilities have been built and put into operation. Among them, technologies that expand the sources of low-carbon olefins, represented by the dehydrogenation of low-carbon alkanes to olefins, have been widely used. Currently, the mainstream dehydrogenation processes are UOP's Oleflex process and ABB Lummus's Catofin process. Mixed alkane dehydrogenation to olefins can process two or more low-carbon alkanes simultaneously, adjusting the product structure according to market demand to maximize economic benefits. At present, several C3 / C4 mixed dehydrogenation units have been built and put into operation in China, but most of them use mixed feedstocks of C3 and C4, and the reaction conditions, such as temperature, often only meet the requirements of one of the products. More seriously, deviations from the optimal reaction conditions may lead to increased carbon deposition, thereby creating local hot spots in the catalyst bed and causing a decline in catalyst performance.

[0004] CN107428633 proposes an integrated C3-C4 hydrocarbon dehydrogenation method. This method involves contacting a C3-C4 hydrocarbon feedstock with a dehydrogenation catalyst classified as Geldart A or Geldart B in a fluidized bed at 550℃-760℃ to form dehydrogenation products, followed by catalyst activation in a fluidized bed regenerator to produce a product stream of the target olefin or diene. CN110845292 proposes a system and method for preparing and processing mixed C3 / C4 alkane dehydrogenation products. This involves setting up a desulfurization system connected to a product cooling and separation system to treat sulfur in the butane and isobutene mixture, thereby reducing the impact on the etherification system. However, in the above methods, both C3 and C4 are mixed feedstocks, and the dehydrogenation reaction conditions can only satisfy one of the products.

[0005] CN105693450 proposes a method and system for producing olefins. Through a specific arrangement, the purging cycle, regeneration cycle, or venting / reduction cycle of the reactors do not overlap, allowing multiple dehydrogenation systems to share a compression and separation system, thereby reducing equipment investment. Although C3 and C4 can react in specific reactors, due to the aforementioned limitations, the reaction times of C3 and C4 materials need to be kept consistent. The two systems still have mutual constraints, thus it is still impossible to simultaneously achieve optimal dehydrogenation reaction conditions for both C3 and C4. Summary of the Invention

[0006] The technical problem to be solved by this application is that existing mixed low-carbon alkane dehydrogenation devices can only guarantee that one of C3 or C4 is in the optimal dehydrogenation reaction conditions, resulting in a decline in reaction performance.

[0007] In a first aspect, this application provides a method for dehydrogenating mixed low-carbon alkanes, comprising:

[0008] The first low-carbon alkane undergoes a first dehydrogenation reaction in the first reaction zone at a first reaction temperature T1 to generate a first reaction product containing the first low-carbon alkene.

[0009] The second low-carbon alkane undergoes a second dehydrogenation reaction in the second reaction zone at a second reaction temperature T2 to generate a second reaction product containing a second low-carbon alkene.

[0010] Among them, 10℃≤T1-T2≤200℃.

[0011] In this application, T1-T2 represent the difference between the first reaction temperature and the second reaction temperature, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or any value between them.

[0012] In some embodiments, 20℃≤T1-T2≤150℃. In some embodiments, 30℃≤T1-T2≤80℃.

[0013] In some embodiments, 500℃ ≤ T1 ≤ 750℃, for example, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, or any value between them. In some embodiments, 550℃ ≤ T1 ≤ 700℃.

[0014] In some embodiments, 400℃ ≤ T2 ≤ 650℃, for example, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, or any value between them. In some embodiments, 450℃ ≤ T2 ≤ 600℃.

[0015] In some embodiments, at least one, preferably at least two, first reactors are provided in the first reaction zone, and a first catalyst is provided in the first reactor. In some embodiments, two, three, four, five, six, seven, eight, or nine first reactors are provided in the first reaction zone.

[0016] In some embodiments, at least one, preferably at least two, second reactors are provided in the second reaction zone, and a second catalyst is provided in the second reactor. In some embodiments, two, three, four, five, six, seven, eight, or nine second reactors are provided in the second reaction zone.

[0017] In some embodiments, regeneration gas is used to regenerate the catalysts in the first and second reaction zones, the regeneration gas passing through the first and second reaction zones in series.

[0018] In some embodiments, the first regenerated gas first enters the first reaction zone, regenerating the first catalyst in the first reaction zone to obtain the second regenerated gas; the second regenerated gas enters the second reaction zone, regenerating the second catalyst in the second reaction zone to obtain the regenerated tail gas.

[0019] In some embodiments, the first low-carbon alkane is a C3-C4 alkane. In some embodiments, the first low-carbon alkane is propane and / or n-butane.

[0020] In some embodiments, the second low-carbon alkane is a C4 alkane. In some embodiments, the second low-carbon alkane is isobutane and / or n-butane.

[0021] In some embodiments, the regeneration gas is a mixture containing nitrogen and oxygen, wherein the oxygen volume content is 10%-30%, for example 13%, 15%, 17%, 19%, 20%, 21%, 23%, 25% or 27%.

[0022] In some embodiments, the first catalyst and the second catalyst may be the same or different, and are selected from catalysts containing at least one metal, Cr or Pt.

[0023] In some embodiments, the mass ratio of the first low-carbon alkane feed rate, the second low-carbon alkane feed rate, and the regeneration gas is 1:(0.3-3):(0.5-10). In some embodiments, the mass ratio of the first low-carbon alkane feed rate, the second low-carbon alkane feed rate, and the regeneration gas is 1:(0.6-2):(1-10). In some embodiments, the mass ratio of the first low-carbon alkane feed rate, the second low-carbon alkane feed rate, and the regeneration gas is 1:(0.6-2):(1-5).

[0024] In some embodiments, the mass ratio of the first low-carbon alkane feed rate to the second low-carbon alkane feed rate is 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.0, 1:2.1, 1:2.3, 1:2.5, 1:2.7, 1:2.9, or any value between them. In some embodiments, the mass ratio of the first low-carbon alkane feed rate to the second low-carbon alkane feed rate is 1:(0.3-3), for example, 1:(0.6-2).

[0025] In some embodiments, the feed rate of the first low-carbon alkane and the mass ratio of the regenerated gas are 1:0.7, 1:1, 1:1.3, 1:1.5, 1:1.7, 1:1.2, 1:2.3, 1:2.5, 1:2.7, 1:3.0, 1:3.3, 1:3.5, 1:3.7, 1:4.0, 1:4.3, 1:4.5, 1:4.7, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or any value between them. In some embodiments, the feed rate of the first low-carbon alkane and the mass ratio of the regenerated gas are 1:(0.5-10), for example, 1:(1-5).

[0026] In some embodiments, the reaction pressure in the first reaction zone is 10 kPaA-300 kPaA, for example, 20 kPaA, 40 kPaA, 60 kPaA, 80 kPaA, 100 kPaA, 120 kPaA, 140 kPaA, 160 kPaA, 180 kPaA, 200 kPaA, 220 kPaA, 240 kPaA, 260 kPaA, 280 kPaA, or any value between them. In some embodiments, the reaction pressure in the first reaction zone is 30 kPaA-200 kPaA.

[0027] In some embodiments, the mass hourly space velocity (MSV) of the reaction gas in the first reaction zone is 0.1-4 h⁻¹. -1 For example, 0.3h-1 0.5h -1 0.7h -1 0.9h -1 1.0h -1 1.3h -1 1.5h -1 1.7h -1 1.9h -1 2.0h -1 2.5h -1 3.0h -1 3.5h -1 Or any value in between. In some embodiments, the mass hourly space velocity (MSV) of the reaction gas in the first reaction zone is 0.4-2 h⁻¹. -1 .

[0028] In some embodiments, the reaction pressure in the second reaction zone is 10 kPaA-200 kPaA, for example, 20 kPaA, 40 kPaA, 60 kPaA, 80 kPaA, 100 kPaA, 120 kPaA, 140 kPaA, 160 kPaA, 180 kPaA, or any value between them. In some embodiments, the reaction pressure in the second reaction zone is 20-150 kPaA.

[0029] In some embodiments, the mass hourly space velocity (MSV) of the reaction gas in the second reaction zone is 0.1-6 h⁻¹. -1 For example, 0.3h -1 0.5h -1 0.7h -1 0.9h -1 1.0h -1 1.3h -1 1.5h -1 1.7h -1 1.9h -1 2.0h -1 2.5h -1 3.0h -1 3.5h -1 4.0h -1 4.5h -1 5.0h -1 5.5h -1 Or any value in between. In some embodiments, the mass hourly space velocity (MSV) of the reaction gas in the second reaction zone is 0.4-4 h⁻¹. -1 .

[0030] In some embodiments, the temperature of the first regeneration gas entering the first reaction zone is 550°C-750°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, or any value between them. In some embodiments, the temperature of the first regeneration gas entering the first reaction zone is 580°C-720°C.

[0031] In some embodiments, the temperature of the second regeneration gas entering the second reaction zone is 500°C-700°C, for example, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, or any value between them. In some embodiments, the temperature of the second regeneration gas entering the second reaction zone is 540°C-650°C.

[0032] In some embodiments, the reaction and catalyst regeneration occur alternately in the first reaction zone and the second reaction zone.

[0033] In some implementations, the second regenerated gas may be partially vented or recycled back to the first reaction zone.

[0034] In some implementations, the second regenerated gas is temperature-adjusted before entering the second reaction zone.

[0035] In some embodiments, the method further includes separating the first reaction product and the second reaction product to obtain unreacted first low-carbon alkane recycle material, first low-carbon olefin, unreacted second low-carbon alkane recycle material and second low-carbon olefin.

[0036] In some embodiments, the first reaction product and the second reaction product are separated in the same separation unit.

[0037] In some embodiments, unreacted first low-carbon alkane recycled material and unreacted second low-carbon alkane recycled material are returned to the first reaction zone and the second reaction zone for recycling, respectively.

[0038] In some embodiments, the method for dehydrogenation of mixed low-carbon alkanes provided in this application includes the following specific steps:

[0039] After being heated to the first reaction temperature T1 by the first low-carbon alkane feed heater, the first low-carbon alkane feed enters the first reaction zone to undergo a dehydrogenation reaction, generating a first reaction product containing the first low-carbon alkene.

[0040] After being heated to the second reaction temperature T2 by the second low-carbon alkane feed heater, the second low-carbon alkane feed enters the second reaction zone to undergo a dehydrogenation reaction, generating a second reaction product containing the second low-carbon alkene.

[0041] The first reaction product and the second reaction product are fed into a separation system to obtain unreacted first low-carbon alkane recycled material and second low-carbon alkane recycled material, which are returned to the first low-carbon alkane feed and the second low-carbon alkane feed for recycling, respectively. At the same time, the first low-carbon olefin and the second low-carbon olefin are obtained from the separation system.

[0042] When the reaction is complete, the first regeneration gas feed is heated to the required temperature by the regeneration gas feed heater and then enters the first reaction zone, where the catalyst is regenerated, and then the second regeneration gas feed is obtained. The second regeneration gas feed enters the second reaction zone, where the catalyst is regenerated, and then the regeneration tail gas discharge system is formed.

[0043] In a second aspect, this application provides a system for the method of dehydrogenating mixed low-carbon alkanes described in the first aspect, comprising a first reaction unit, a second reaction unit, an optional regeneration unit, and an optional separation unit.

[0044] The first reaction unit includes a first heat exchanger and a first reaction zone, and a first reactor is provided in the first reaction zone; preferably, the number of first reactors is greater than or equal to 1, and more preferably greater than or equal to 2.

[0045] The second reaction unit includes a second heat exchanger and a second reaction zone, and a second reactor is provided in the second reaction zone; preferably, the number of second reactors is greater than or equal to 1, and more preferably greater than or equal to 2.

[0046] In some implementations, the regeneration unit includes a third heater, a first regenerator, and a second regenerator.

[0047] In some embodiments, the first heat exchanger is used to regulate the temperature of the first low-carbon alkane entering the first reaction zone.

[0048] In some embodiments, the second heat exchanger is used to regulate the temperature of the second low-carbon alkane entering the second reaction zone.

[0049] In some embodiments, the third heat exchanger is used to regulate the temperature of the regeneration gas.

[0050] In some embodiments, the regeneration unit further includes a fourth heat exchanger disposed between the first reaction zone and the second reaction zone for adjusting the temperature of the regeneration gas at the outlet of the first reaction zone.

[0051] In some embodiments, the first regeneration gas feed is heated to the required temperature by a third heat exchanger and then enters the first reaction zone, where the catalyst is regenerated, resulting in the second regeneration gas feed. The second regeneration gas feed enters the second reaction zone, where the catalyst is regenerated, forming a regeneration tail gas discharge system.

[0052] In some embodiments, the first regenerator is disposed in the first reaction zone for regenerating the first catalyst, and the second regenerator is disposed in the second reaction zone for regenerating the second catalyst.

[0053] Compared with existing technologies, this application has the following outstanding advantages:

[0054] 1) The reaction conditions for dehydrogenation of different low-carbon alkanes can be controlled independently to ensure that the dehydrogenated materials are in optimal reaction conditions.

[0055] 2) The regeneration system equipment used for dehydrogenation of mixed low-carbon olefins, such as compressors and regeneration gas feed heaters, can be shared, reducing redundant investment in equipment. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of a method for dehydrogenating mixed low-carbon alkanes according to some embodiments of this application.

[0057] Figure 2 This is a schematic diagram of a method for dehydrogenating mixed low-carbon alkanes according to some embodiments of this application.

[0058] Figure 3 A schematic diagram of a method for dehydrogenating mixed low-carbon alkanes according to some embodiments provided in this application.

[0059] Figure 4 This is a schematic diagram of a prior art method for dehydrogenating mixed low-carbon alkanes.

[0060] Figure label:

[0061] Wherein, 1 is the first low-carbon alkane feed; 2 is the second low-carbon alkane feed; 3 is the first reaction product; 4 is the second reaction product; 5 is the first low-carbon alkane recycled material; 6 is the second low-carbon alkane recycled material; 7 is the first low-carbon olefin; 8 is the second low-carbon olefin; 9 is the first regeneration gas feed; 10 is the second regeneration gas feed; 11 is the regeneration tail gas; 12 is the first regeneration gas vent section; 13 is the first regeneration gas recycling section; 14 is the regeneration gas feed; and 15 is the mixed dehydrogenation reaction product.

[0062] E1 is the first low-carbon alkane feed heater; E2 is the second low-carbon alkane feed heater; E3 is the regeneration gas feed heater; E4 is the regeneration gas intermediate heater; E5 is the mixed low-carbon alkane feed heater.

[0063] R represents the mixed dehydrogenation reaction zone; R1 represents the first reaction zone; and R2 represents the second reaction zone.

[0064] S represents the mixed dehydrogenation separation system; S1 represents the separation system.

[0065] X1 is the first regenerator; X2 is the second regenerator. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and technologies have also been described in numerous publications.

[0067] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0068] In this application, "low-carbon alkane" refers to alkane with no more than 5 carbon atoms, such as methane, ethane, propane, isopropane, n-butane, isobutane, tert-butane, n-pentane, isopentane, octopentane, etc.

[0069] In this application, "low-carbon olefin" refers to olefins with no more than 5 carbon atoms, such as ethylene, propylene, n-butene, isobutene, 2-butene, n-pentene, isopentenene, 2-pentene, etc.

[0070] This application provides a method for dehydrogenating mixed low-carbon alkanes, according to... Figure 1The process shown involves the following steps: First low-carbon alkane feed 1 is heated to a first reaction temperature T1 by first low-carbon alkane feed heater E1 and then enters first reaction zone R1 to undergo a dehydrogenation reaction, generating a first reaction product 3 containing a first low-carbon olefin; Second low-carbon alkane feed 2 is heated to a second reaction temperature T2 by second low-carbon alkane feed heater E2 and then enters second reaction zone R2 to undergo a dehydrogenation reaction, generating a second reaction product 4 containing a second low-carbon olefin; First reaction product 3 and Second reaction product 4 are sent to separation system S1 to obtain unreacted first low-carbon alkane recycled material 5 and Second low-carbon alkane recycled material 6, which are returned to first low-carbon alkane feed 1 and Second low-carbon alkane feed 2 for recycling, respectively. Simultaneously, First low-carbon olefin 7 and Second low-carbon olefin 8 are obtained from separation system S1. When the reaction is complete, the first regeneration gas feed 9 is heated to the required temperature by the regeneration gas feed heater E3 and then enters the first reaction zone R1, so that the catalyst in the first reaction zone R1 is regenerated. Then, the second regeneration gas feed 10 enters the second reaction zone R2, so that the catalyst in the second reaction zone S2 is regenerated and the regeneration tail gas 11 is discharged from the system.

[0071] In some embodiments, the ratio of the first low-carbon alkane feed rate, the second low-carbon alkane feed rate, and the regeneration gas is 1:(0.6-2):(1-10). The reaction pressure in the first reaction zone is 30-200 kPaA, and the mass hourly space velocity (HSV) of the reaction gas is 0.4-2 h⁻¹. -1 The reaction pressure in the second reaction zone is 20-150 kPaA, and the mass hourly space velocity (HHSV) of the reaction gas is 0.4-4 h⁻¹. -1 .

[0072] In some embodiments, the first reaction zone contains two or more reactors, and the second reaction zone contains two or more reactors. The number of reaction zones in the two reaction zones may be the same or different.

[0073] In some embodiments, the reactors in the first and second reaction zones are filled with catalysts, which are catalysts containing at least one metal selected from Cr or Pt. The catalysts in the two reaction zones may be the same or different.

[0074] During the dehydrogenation reaction stage, side reactions produce carbon deposits, which need to be removed by regeneration gas to restore the catalyst's activity. Therefore, the first and second reaction zones alternate between the reaction and catalyst regeneration.

[0075] In some embodiments, the regeneration gas is a mixture of nitrogen and oxygen, wherein the oxygen volume content is 10-30%.

[0076] In some embodiments, the regeneration temperature of the first reaction zone is 580°C-720°C. In some embodiments, the regeneration temperature of the second reaction zone is 500°C-700°C.

[0077] Because different types of low-carbon alkanes exhibit varying reactivity during the dehydrogenation reaction, and because the carbon deposit content changes with the progress of the reaction and catalyst aging, the outlet temperature of the regenerated gas in the first reaction zone fluctuates. Therefore, in a preferred embodiment of this application, a heat exchanger for regulating the inlet temperature of the regenerated gas in the second reaction zone can be installed between the first and second reaction zones.

[0078] In some implementation schemes, such as Figure 2 As shown in the process diagram, a regeneration gas intermediate heater E4 is provided between the first reaction zone R1 and the second reaction zone R2. When the reaction is completed, the first regeneration gas feed 9 is heated to the required temperature by the regeneration gas feed heater E3 and then enters the first reaction zone R1, regenerating the catalyst in the first reaction zone R1 to obtain the second regeneration gas feed 10. The second regeneration gas feed 10 passes through the regeneration gas intermediate heater E4 and is heated to the required temperature. Part of it enters the second reaction zone R2, regenerating the catalyst in the second reaction zone R2 to form regeneration tail gas 11, which is discharged from the system. Another part is discharged from the system as the first regeneration gas venting section 12, and the remaining part is recycled back to the first reaction zone outlet as the first regeneration gas circulation section 13. The regeneration gas at the outlet of the first reaction zone can be partially recycled back to the inlet of the first reaction zone.

[0079] In a preferred embodiment of this application, a regenerator specifically for catalyst regeneration is provided in the first reaction zone and / or the second reaction zone. The catalyst to be regenerated can be transported from the reaction zone to the regenerator, and the regenerated catalyst can also be returned to the reaction zone.

[0080] In some implementations, such as Figure 3 As shown in the figure, a first regenerator X1 is provided in the first reaction zone R1, and a second regenerator X2 is provided in the second reaction zone. The catalyst that needs to be regenerated can be transported from the reaction zone to the regenerator, and the regenerated catalyst can also be returned to the reaction zone, as shown by the dotted line in the figure.

[0081] Existing methods for the dehydrogenation of mixed low-carbon alkanes, according to Figure 4 The process shown involves mixing the first low-carbon alkane feed 1 and the second low-carbon alkane feed 2, then heating them to the reaction temperature T via the mixed low-carbon alkane feed heater E5 before entering the mixed dehydrogenation reaction zone R to undergo a dehydrogenation reaction, generating a mixed dehydrogenation reaction product 15. This mixed dehydrogenation reaction product 15 is then fed into the mixed dehydrogenation separation system S, from which the first low-carbon olefin 7 and the second low-carbon olefin 8 are obtained. After the reaction is complete, the regeneration gas feed 14 is heated to the required temperature via the regeneration gas feed heater E3 before entering the mixed dehydrogenation reaction zone R. This regeneration of the catalyst in the mixed dehydrogenation reaction zone R results in the formation of regeneration tail gas 11, which is then discharged from the system.

[0082] The present application will be described in detail below through examples and comparative examples.

[0083] Example 1

[0084] In such Figure 1 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0085] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 600℃, the reaction pressure is 55 kPaA, and the propane mass hourly space velocity (WHSV) is 0.7 h⁻¹. -1 The second reaction was carried out at a temperature of 520℃, a pressure of 50 kPaA, and a mass hourly space velocity (HHSV) of 1.0 h⁻¹. -1 The temperature of the first reaction is 80°C higher than that of the second reaction.

[0086] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:0.8:4. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature in the first reaction zone is 650℃, and the regeneration temperature in the second reaction zone is 570℃.

[0087] Propane conversion 45.0%, propylene selectivity 90%, propylene yield 40.5%. Isobutane conversion 55.0%, isobutene selectivity 89.0%, isobutene yield 49.0%.

[0088] Example 2

[0089] In such Figure 1 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0090] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 650℃, the reaction pressure is 45 kPaA, and the propane mass hourly space velocity (WHSV) is 0.7 h⁻¹. -1 The second reaction was carried out at a temperature of 570℃, a pressure of 42 kPaA, and a mass hourly space velocity (H₂S) of 4.0 h⁻¹. -1 The temperature of the first reaction is 80°C higher than that of the second reaction.

[0091] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:1:5. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature in the first reaction zone is 680℃, and the regeneration temperature in the second reaction zone is 600℃.

[0092] Propane conversion was 54.5%, propylene selectivity was 85.9%, and propylene yield was 46.8%. Isobutane conversion was 65.6%, isobutene selectivity was 82.1%, and isobutene yield was 53.9%.

[0093] Example 3

[0094] In such Figure 1 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0095] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 580℃, the reaction pressure is 55 kPaA, and the propane mass hourly space velocity (HSV) is 0.7 h⁻¹. -1 The second reaction was carried out at a temperature of 520℃, a pressure of 50 kPaA, and a mass hourly space velocity (HHSV) of 1.0 h⁻¹. -1 The temperature of the first reaction is 60°C higher than that of the second reaction.

[0096] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:2:10. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature in the first reaction zone is 630℃, and the regeneration temperature in the second reaction zone is 560℃.

[0097] Propane conversion was 44.8%, propylene selectivity was 93.8%, and propylene yield was 42.0%. Isobutane conversion was 54.8%, isobutene selectivity was 89.2%, and isobutene yield was 48.9%.

[0098] Example 4

[0099] In such Figure 1 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0100] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 600℃, the reaction pressure is 60 kPaA, and the propane mass hourly space velocity (WHSV) is 0.7 h⁻¹. -1 The second reaction was carried out at a temperature of 550℃, a pressure of 50 kPaA, and a mass hourly space velocity (HHSV) of 1.0 h⁻¹. -1 The temperature of the first reaction is 50°C higher than that of the second reaction.

[0101] The mass ratio of the first low-carbon alkane feed rate, the second low-carbon alkane feed rate, and the regeneration gas is 1:0.6:4. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature in the first reaction zone is 650℃, and the regeneration temperature in the second reaction zone is 590℃.

[0102] Propane conversion was 44.5%, propylene selectivity was 89.7%, and propylene yield was 39.9%. Isobutane conversion was 62.0%, isobutene selectivity was 85.1%, and isobutene yield was 52.8%.

[0103] Example 5

[0104] In such Figure 1 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0105] The first reaction zone contains five reactors, each loaded with a Cr-containing catalyst. The second reaction zone also contains five reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 630℃, the reaction pressure is 55 kPaA, and the propane mass hourly space velocity (HSV) is 0.4 h⁻¹. -1 The second reaction was carried out at a temperature of 520℃, a pressure of 50 kPaA, and a mass hourly space velocity (H₂S) of 2.0 h⁻¹. -1 The temperature of the first reaction is 110°C higher than that of the second reaction.

[0106] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:0.8:1. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature in the first reaction zone is 660℃, and the regeneration temperature in the second reaction zone is 570℃.

[0107] Propane conversion was 48.3%, propylene selectivity was 86.1%, and propylene yield was 41.6%. Isobutane conversion was 52.8%, isobutene selectivity was 87.7%, and isobutene yield was 46.3%.

[0108] Example 6

[0109] In such Figure 2 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0110] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains five reactors, also loaded with a Cr-containing catalyst. The first reaction temperature is 700℃, the reaction pressure is 30 kPaA, and the propane mass hourly space velocity (WHSV) is 2.0 h⁻¹. -1 The second reaction was carried out at a temperature of 500℃, a pressure of 20 kPaA, and a mass hourly space velocity (HHSV) of 0.6 h⁻¹. -1The temperature of the first reaction is 200°C higher than that of the second reaction.

[0111] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:0.8:4. After the reaction, regeneration is performed, and the regeneration gas is a mixture of nitrogen and oxygen with an oxygen content of 30%. The regeneration temperature in the first reaction zone is 720℃, and the regeneration temperature in the second reaction zone is 650℃. 20% of the regeneration gas from the outlet of the first reaction zone is vented and mixed with the regeneration tail gas.

[0112] Propane conversion was 63.5%, propylene selectivity was 81.5%, and propylene yield was 51.8%. Isobutane conversion was 53.6%, isobutene selectivity was 90.8%, and isobutene yield was 48.6%.

[0113] Example 7

[0114] In such Figure 3 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0115] The first reaction zone contains two reactors and one regenerator, with the reactors containing a Pt-containing catalyst. The second reaction zone also contains two reactors and one regenerator, with the reactors containing a Pt-containing catalyst. The first reaction temperature is 630℃, the reaction pressure is 120 kPaA, and the propane mass hourly space velocity (HSV) is 0.5 h⁻¹. -1 The second reaction was carried out at a temperature of 530℃, a pressure of 100 kPaA, and a mass hourly space velocity (HHSV) of 0.6 h⁻¹. -1 The temperature of the first reaction is 100°C higher than that of the second reaction.

[0116] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:0.8:3. After the reaction, regeneration is performed, and the regeneration gas is a mixture of nitrogen and oxygen with an oxygen content of 10%. The regeneration temperature in the first reaction zone is 680℃, and the regeneration temperature in the second reaction zone is 610℃.

[0117] Propane conversion was 39.8%, propylene selectivity was 94.2%, and propylene yield was 37.5%. Isobutane conversion was 50.3%, isobutene selectivity was 92.6%, and isobutene yield was 46.5%.

[0118] Example 8

[0119] In such Figure 3 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane isobutane.

[0120] The first reaction zone contains two reactors and one regenerator, with the reactors containing a Pt-containing catalyst. The second reaction zone also contains two reactors and one regenerator, with the reactors containing a Pt-containing catalyst. The first reaction temperature is 660℃, the reaction pressure is 200 kPaA, and the propane mass hourly space velocity (HSV) is 0.5 h⁻¹. -1 The second reaction was carried out at a temperature of 520℃, a pressure of 150 kPaA, and a mass hourly space velocity (HHSV) of 0.6 h⁻¹. -1 The temperature of the first reaction is 80°C higher than that of the second reaction.

[0121] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:1.2:4. After the reaction, regeneration is performed, and the regeneration gas is a mixture of nitrogen and oxygen with an oxygen content of 15%. The regeneration temperature in the first reaction zone is 680℃, and the regeneration temperature in the second reaction zone is 600℃.

[0122] Propane conversion was 40.1%, propylene selectivity was 86.1%, and propylene yield was 34.5%. Isobutane conversion was 46.0%, isobutene selectivity was 90.4%, and isobutene yield was 41.6%.

[0123] Example 9

[0124] In such Figure 2 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is n-butane and the second low-carbon alkane is isobutane.

[0125] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 560℃, the reaction pressure is 80 kPaA, and the n-butane mass hourly space velocity is 0.8 h⁻¹. -1 The second reaction was carried out at a temperature of 520℃, a pressure of 60 kPaA, and a mass hourly space velocity (HHSV) of 1.4 h⁻¹. -1 The temperature of the first reaction is 40°C higher than that of the second reaction.

[0126] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:1:5. After the reaction, regeneration is performed, and the regeneration gas is air with an oxygen content of 21%. The regeneration temperature of the first reaction zone is 590℃. An intermediate heater is also set between the first and second reaction zones, so that the regeneration temperature of the second reaction zone is 550℃.

[0127] The conversion rate of n-butane was 52.6%, the selectivity of n-butene was 87.2%, and the yield of n-butene was 45.9%. The conversion rate of isobutane was 52.5%, the selectivity of isobutene was 88.3%, and the yield of isobutene was 46.4%.

[0128] Example 10

[0129] In such Figure 2 The apparatus shown performs a dehydrogenation reaction of mixed low-carbon alkanes, wherein the first low-carbon alkane is propane and the second low-carbon alkane is n-butane.

[0130] The first reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The second reaction zone contains three reactors, each loaded with a Cr-containing catalyst. The first reaction temperature is 600℃, the reaction pressure is 70 kPaA, and the propane mass hourly space velocity (HSV) is 0.6 h⁻¹. -1 The second reaction was carried out at a temperature of 560℃, a pressure of 60 kPaA, and a mass hourly space velocity (HHSV) of 0.8 h⁻¹. -1 The temperature of the first reaction is 40°C higher than that of the second reaction.

[0131] The mass ratio of the first low-carbon alkane feed, the second low-carbon alkane feed, and the regeneration gas is 1:0.6:5. Regeneration is performed after the reaction, and the regeneration gas is a mixture of nitrogen and oxygen with an oxygen content of 15%. The regeneration temperature in the first reaction zone is 650℃, and the regeneration temperature in the second reaction zone is 610℃. An intermediate heat exchanger is installed between the first and second reaction zones, and 20% of the regeneration gas from the outlet of the first reaction zone is recycled back to the inlet of the first reaction zone.

[0132] Propane conversion was 44.7%, propylene selectivity was 89.4%, and propylene yield was 40.0%. n-Butane conversion was 52.8%, n-butene selectivity was 87.5%, and n-butene yield was 46.2%.

[0133] Example 11

[0134] The only difference from Example 1 is that the first reaction temperature is 550°C, the second reaction temperature is 530°C, and the first reaction temperature is 20°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 600°C, the regeneration temperature of the second reaction zone is 570°C, and an intermediate heat exchanger is provided between the first and second reaction zones.

[0135] Propane conversion was 37.8%, propylene selectivity was 94.8%, and propylene yield was 35.8%. Isobutane conversion was 56.8%, isobutene selectivity was 87.6%, and isobutene yield was 49.8%.

[0136] Example 12

[0137] The only difference from Example 1 is that the first reaction temperature is 580°C, the second reaction temperature is 530°C, and the first reaction temperature is 50°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 640°C, and the regeneration temperature of the second reaction zone is 570°C.

[0138] Propane conversion was 42.5%, propylene selectivity was 92.4%, and propylene yield was 39.3%. Isobutane conversion was 57.0%, isobutene selectivity was 87.5%, and isobutene yield was 49.9%.

[0139] Example 13

[0140] The only difference from Example 1 is that the first reaction temperature is 610°C, the second reaction temperature is 500°C, and the first reaction temperature is 110°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 660°C, and the regeneration temperature of the second reaction zone is 540°C.

[0141] Propane conversion was 47.3%, propylene selectivity was 88.8%, and propylene yield was 42.0%. Isobutane conversion was 51.0%, isobutene selectivity was 92.0%, and isobutene yield was 46.9%.

[0142] Example 14

[0143] The only difference from Example 1 is that the first reaction temperature is 620°C and the second reaction temperature is 470°C, with the first reaction temperature being 150°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 670°C, and the regeneration temperature of the second reaction zone is 560°C. 10% of the regeneration gas from the outlet of the first reaction zone is vented and mixed with the regeneration tail gas.

[0144] Propane conversion was 49.1%, propylene selectivity was 87.4%, and propylene yield was 42.9%. Isobutane conversion was 45.0%, isobutene selectivity was 96.5%, and isobutene yield was 43.4%.

[0145] Example 15

[0146] The only difference from Example 1 is that the first reaction temperature is 650°C and the second reaction temperature is 450°C, with the first reaction temperature being 200°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 700°C, and the regeneration temperature of the second reaction zone is 600°C. 20% of the regeneration gas from the outlet of the first reaction zone is vented and mixed with the regeneration tail gas.

[0147] Propane conversion was 53.7%, propylene selectivity was 84.0%, and propylene yield was 45.1%. Isobutane conversion was 36.0%, isobutene selectivity was 94.5%, and isobutene yield was 34.0%.

[0148] Comparative Example 1

[0149] In such Figure 4The apparatus shown performs a mixed low-carbon alkane dehydrogenation reaction. The dehydrogenation feedstock is a mixture of propane and isobutane, with a propane to isobutane ratio of 1:0.8. The reactor is packed with a Cr-containing catalyst, the reaction temperature is 560°C, the reaction pressure is 50 kPaA, and the total space velocity is 0.7 h⁻¹. After the reaction, regeneration is performed using air with an oxygen content of 21% at a regeneration temperature of 630°C.

[0150] Propane conversion was 36.3%, propylene selectivity was 93.5%, and propylene yield was 33.9%. Isobutane conversion was 52.2%, isobutene selectivity was 88.1%, and isobutene yield was 46.0%.

[0151] Comparative Example 2

[0152] In such Figure 4 The apparatus shown performs a mixed low-carbon alkane dehydrogenation reaction. The dehydrogenation feedstock is a mixture of n-butane and isobutane, with a n-butane to isobutane content ratio of 1:1. The reactor is packed with a Cr-containing catalyst, the reaction temperature is 540℃, the reaction pressure is 60 kPaA, and the total space velocity is 0.8 h⁻¹. -1 After the reaction is complete, regeneration is performed using air with an oxygen content of 21% at a regeneration temperature of 600℃.

[0153] The conversion rate of n-butane was 46.2%, the selectivity of n-butene was 90.1%, and the yield of n-butene was 41.6%. The conversion rate of isobutane was 47.8%, the selectivity of isobutene was 89.6%, and the yield of isobutene was 42.8%.

[0154] Comparative Example 3

[0155] The only difference from Example 1 is that the first reaction temperature is 550°C, the second reaction temperature is 570°C, and the second reaction temperature is 20°C higher than the first reaction temperature. The regeneration temperature of the first reaction zone is 600°C, the regeneration temperature of the second reaction zone is 620°C, and an intermediate heat exchanger is provided between the first and second reaction zones.

[0156] Propane conversion was 37.7%, propylene selectivity was 94.6%, and propylene yield was 35.7%. Isobutane conversion was 59.8%, isobutene selectivity was 76.5%, and isobutene yield was 45.7%.

[0157] Comparative Example 4

[0158] The only difference from Example 1 is that the first reaction temperature is 700°C, the second reaction temperature is 450°C, and the first reaction temperature is 250°C higher than the second reaction temperature. The regeneration temperature of the first reaction zone is 720°C, the regeneration temperature of the second reaction zone is 640°C, and 40% of the regeneration gas from the outlet of the first reaction zone is discharged and mixed with the regeneration tail gas.

[0159] Propane conversion was 60.0%, propylene selectivity was 73.0%, and propylene yield was 43.8%. Isobutane conversion was 36.0%, isobutene selectivity was 94.3%, and isobutene yield was 33.9%.

[0160] As can be seen from Example 1 and Comparative Example 1, when propane and isobutane are dehydrogenated using the mixed low-carbon alkane dehydrogenation method provided in this application, the yields of propylene and isobutene can be increased while ensuring comparable selectivity, since both low-carbon alkanes react under relatively favorable conditions.

[0161] As can be seen from Example 9 and Comparative Example 2, when using the mixed low-carbon alkane dehydrogenation method provided in this application to perform mixed dehydrogenation of n-butane and isobutane, the yields of n-butene and isobutene can be improved, and both conversion and selectivity can be improved, while ensuring comparable selectivity.

[0162] The preferred embodiments of this application have been described in detail above; however, this application is not limited thereto. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this application and are all within the protection scope of this application.

Claims

1. A method for dehydrogenating mixed low-carbon alkanes, comprising: The first low-carbon alkane undergoes a first dehydrogenation reaction in the first reaction zone at a first reaction temperature T1 to generate a first reaction product containing the first low-carbon alkene. The second low-carbon alkane undergoes a second dehydrogenation reaction in the second reaction zone at a second reaction temperature T2 to generate a second reaction product containing a second low-carbon alkene. Among them, 10℃≤T1-T2≤200℃.

2. The method according to claim 1, characterized in that, 20℃≤T1-T2≤150℃, preferably 30℃≤T1-T2≤80℃.

3. The method according to claim 1 or 2, characterized in that, 500℃≤T1≤750℃, preferably 550℃≤T1≤700℃; and / or 400℃≤T2≤650℃, preferably 450℃≤T2≤600℃.

4. The method according to any one of claims 1-3, characterized in that, At least one, preferably at least two, first reactors are provided in the first reaction zone, and a first catalyst is provided in the first reactor; The second reaction zone is equipped with at least one, preferably at least two, second reactors, and the second reactors are equipped with a second catalyst. Preferably, regeneration gas is used to regenerate the catalysts in the first reaction zone and the second reaction zone. The regeneration gas passes through the first reaction zone and the second reaction zone in series. Preferably, the first regeneration gas first enters the first reaction zone, regenerating the first catalyst in the first reaction zone to obtain the second regeneration gas; the second regeneration gas enters the second reaction zone, regenerating the second catalyst in the second reaction zone to obtain the regeneration tail gas.

5. The method according to any one of claims 1-4, characterized in that, The first low-carbon alkane is a C3-C4 alkane, preferably propane and / or n-butane; and / or The second low-carbon alkane is a C4 alkane, preferably isobutane and / or n-butane; and / or The regenerated gas is a mixture containing nitrogen and oxygen, wherein the oxygen volume content is 10%-30%; and / or The first catalyst and the second catalyst may be the same or different, and are selected from catalysts containing at least one metal, Cr or Pt.

6. The method according to any one of claims 1-5, characterized in that, The feed rates of the first low-carbon alkane, the second low-carbon alkane, and the regeneration gas are in a mass ratio of 1:(0.3-3):(0.5-10), preferably 1:(0.6-2):(1-5); and / or The reaction pressure in the first reaction zone is 10 kPaA-300 kPaA, preferably 30 kPaA-200 kPaA, and the mass hourly space velocity (HSV) of the reaction gas is 0.1-4 h⁻¹. -1 Preferably 0.4-2h -1 ; and / or The reaction pressure in the second reaction zone is 10 kPaA-200 kPaA, preferably 20 kPaA-150 kPaA, and the mass hourly space velocity (HSV) of the reaction gas is 0.1-6 h⁻¹. -1 Preferably 0.4-4h -1 ; and / or The temperature of the first regeneration gas entering the first reaction zone is 550℃-750℃, preferably 580℃-720℃; and / or The temperature of the second regeneration gas entering the second reaction zone is 500℃-700℃, preferably 540℃-650℃.

7. The method according to any one of claims 1-6, characterized in that, The reaction and catalyst regeneration occur alternately in the first and second reaction zones; and / or The second regenerated gas can be partially vented or recycled back to the first reaction zone; and / or The second regenerated gas is adjusted in temperature before entering the second reaction zone.

8. The method according to any one of claims 1-7, characterized in that, The method further includes separating the first reaction product and the second reaction product to obtain unreacted first low-carbon alkane recycle material, first low-carbon olefin, unreacted second low-carbon alkane recycle material, and second low-carbon olefin. Preferably, the first reaction product and the second reaction product are separated in the same separation unit; Preferably, the unreacted first low-carbon alkane recycled material and the unreacted second low-carbon alkane recycled material are returned to the first reaction zone and the second reaction zone for recycling, respectively.

9. A system for a method of dehydrogenating mixed low-carbon alkanes according to any one of claims 1-8, comprising a first reaction unit, a second reaction unit, an optional regeneration unit, and an optional separation unit. in, The first reaction unit includes a first heat exchanger and a first reaction zone, and a first reactor is provided in the first reaction zone; preferably, the number of first reactors is greater than or equal to 1, and more preferably greater than or equal to 2. The second reaction unit includes a second heat exchanger and a second reaction zone, and a second reactor is provided in the second reaction zone; preferably, the number of second reactors is greater than or equal to 1, and more preferably greater than or equal to 2. Preferably, the regeneration unit includes a third heater, a first regenerator, and a second regenerator.

10. The system according to claim 9, characterized in that, The first heat exchanger is used to regulate the temperature of the first low-carbon alkane entering the first reaction zone; and / or The second heat exchanger is used to regulate the temperature of the second low-carbon alkane entering the second reaction zone; and / or The third heat exchanger is used to regulate the temperature of the regeneration gas. Preferably, the regeneration unit further includes a fourth heat exchanger disposed between the first reaction zone and the second reaction zone, used to regulate the temperature of the regeneration gas at the outlet of the first reaction zone; and / or The first regenerator is located in the first reaction zone and is used for the regeneration of the first catalyst. The second regenerator is located in the second reaction zone and is used for the regeneration of the second catalyst.

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