A method and system for producing light olefins through multi-stage catalytic cracking

Abstract

The present invention relates to a method and system for producing light olefins by multi-stage catalytic cracking, the method comprising: allowing feed oil and a first catalyst to enter a reactor system for a multi-stage catalytic cracking reaction to obtain an oil-agent mixture; separating the oil-agent mixture to obtain a reaction oil gas and a catalyst to be produced; separating the reaction oil gas to obtain light olefins; the reactor system comprising three or more upward reaction units connected in series, wherein the outlet temperature of any two directly connected reaction units is 10-100°C higher than the outlet temperature of the previous reaction unit; and the reaction unit is a reaction zone and / or reactor of the reactor. The multi-stage catalytic cracking reaction of the present invention is sequentially carried out in the three or more reaction units connected in series, the reaction temperature is more compatible with the cracking performance of the hydrocarbon molecules, the intermediate products of the catalytic cracking are better converted, and the yield and selectivity of the light olefins can be significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum refining and petrochemical processing, and in particular to a method and system for producing light olefins through multi-stage catalytic cracking. Background Art

[0002] As an important secondary crude oil processing technology, catalytic cracking technology holds an irreplaceable position in the production of clean oil products and light olefins, characterized by its wide feedstock adaptability, high heavy oil conversion rate, and flexible product solutions. Recent development and trends in catalytic cracking technology for chemical feedstock production indicate that major oil companies and research institutions have shifted their focus from increasing light olefin yields to improving light olefin selectivity. In this process, researchers are developing new processes based on optimally matching hydrocarbon cracking performance with reaction temperature, reaction time, and catalyst performance.

[0003] The catalytic cracking unit is a self-heating device, where heat is transferred between the reaction and regeneration systems via the supported catalyst. This makes the regulation of reaction temperature inseparable from the circulation of the catalyst. In addition to providing the heat required for the catalytic cracking reaction, the catalyst also plays a crucial role in providing active centers for the reaction. As the cracking reaction occurs, the heat capacity of the catalyst particles decreases in tandem with the active centers. However, as the cracking reaction progresses, further cracking of small hydrocarbon molecules requires higher reaction temperatures. Researchers have also investigated how to best match reaction temperature and catalyst activity to the cracking properties of hydrocarbon molecules.

[0004] CN107557063 discloses a method for catalytic conversion of low-quality crude oil. This method utilizes a two-stage riser reactor. A portion of the spent catalyst is removed through a central expansion section, while a portion of the regenerated catalyst is added. This method allows for segmented control of the reaction depth and optimizes catalyst activity. However, this method uses a method that reduces the linear velocity and extends the reaction time in the expansion section to remove the catalyst. This increases the residence time of the oil and gas in the expansion section, significantly increases side reactions, and reduces the selectivity of the target product.

[0005] CN105368493 discloses a catalytic conversion method for producing high-octane gasoline. This method involves initially cracking the crude oil with a cooled regeneration agent at a relatively low temperature for a relatively short time. Subsequently, a higher temperature regeneration agent is added, and the cracking reaction is continued at a temperature 5-100°C higher than that in the initial reaction zone for a longer reaction time. This method controls the cracking depth by separately controlling the reaction severity in each riser reactor reaction zone. However, in this method, the carbonized catalyst after reaction in the initial reaction zone is completely transferred to the main reaction zone, which increases the proportion of hydrocarbons reacting on the deactivated catalyst and reduces the selectivity of the target product.

[0006] CN107337574 discloses a catalytic conversion method for producing olefins by cracking light hydrocarbons. This method uses spent catalyst drawn from a stripper or reacted catalyst drawn from a reactor to return to a pre-contact zone. After the light hydrocarbon feedstock is vaporized in the pre-contact zone, it enters the main reaction zone where it contacts the regenerated catalyst for high-temperature cracking. This method combines low-temperature pre-gasification with high-temperature cracking, optimizing the reactor's temperature distribution. However, due to the low reaction temperature in the pre-contact zone, this method not only vaporizes the light hydrocarbons but also hinders cracking reactions. This significantly reduces the catalyst-to-oil ratio in the main reaction zone, resulting in a low yield of low-carbon olefins from the cracking of the light hydrocarbons.

[0007] CN110240932 discloses a multi-stage fluidized catalytic reaction method and reactor for petroleum hydrocarbons. This method involves contacting and reacting feedstock oil and regenerated catalyst in a first reaction zone. After some of the catalyst is swirled out, the oil and gas continue through a delivery pipe to a second reaction zone where they react with a second catalyst replenished in a third reaction zone. The oil and gas in the first reaction zone continue to undergo cracking reactions under the new catalyst. Light hydrocarbons and light cycle oil react with the second catalyst in the third reaction zone, and the resulting oil enters the second reaction zone where it continues to undergo catalytic cracking. This method enables catalyst replacement, gradient control of the reaction temperature, and control of the carbon content of the regenerated catalyst. However, because the third reaction zone is located below the second reaction zone, the oil and gas in the first reaction zone can undergo severe thermal cracking reactions as they pass through the high-temperature third reaction zone, resulting in the production of large amounts of dry gas.

[0008] CN108753356 discloses a multi-stage countercurrent catalytic cracking / cracking system and method. This method utilizes at least two descending fluidized bed reactors and at least two gas-solid rapid separation devices arranged in a stepped configuration. The discharge port of each descending fluidized bed reactor is connected to the gas-solid mixed phase inlet of the corresponding gas-solid rapid separation device, and the gas outlet of the corresponding gas-solid rapid separation device of each descending fluidized bed reactor is connected to the feed port of the corresponding descending fluidized bed reactor of the previous stage. This method can provide different temperature fields and catalyst activity fields for each stage of the reaction, which is beneficial for improving the selectivity of hydrocarbon catalytic cracking / cracking. However, this method cannot flexibly control the temperature and catalyst activity according to the hydrocarbon cracking performance, which has significant operational limitations.

[0009] In the catalytic cracking reaction process, how to match the cracking properties of hydrocarbon molecules and flexibly control the reaction temperature and catalyst activity to improve the yield and selectivity of light olefins is a technical problem that needs to be solved urgently. Summary of the Invention

[0010] The purpose of the present invention is to provide a method and system for producing light olefins by multi-stage catalytic cracking, so as to improve the yield and selectivity of light olefins.

[0011] In a first aspect, the present invention relates to a method for producing light olefins through multi-stage catalytic cracking, the method comprising: allowing raw oil and a first catalyst to enter a reactor system for a multi-stage catalytic cracking reaction to obtain an oil-agent mixture; separating the oil-agent mixture to obtain reaction oil gas and a catalyst to be generated; and separating the reaction oil gas to obtain light olefins; the reactor system comprises three or more upward reaction units connected in series, and in any two directly connected reaction units, the outlet temperature of the subsequent reaction unit is 10-100°C higher than the outlet temperature of the previous reaction unit; the reaction unit is a reaction zone and / or a reactor of the reactor.

[0012] Optionally, the method further comprises: stripping and regenerating the spent catalyst to obtain a regenerated catalyst; wherein the temperature of the regenerated catalyst is 500-650°C, preferably 550-600°C.

[0013] Optionally, the method further comprises: independently introducing a second catalyst into one or more reaction units after the first-stage reaction unit.

[0014] Optionally, the first catalyst and the second catalyst are each independently the regenerated catalyst and / or the cooled regenerated catalyst.

[0015] Optionally, the outlet temperature of the latter reaction unit is 10-100° C. higher than the outlet temperature of the former reaction unit and is controlled by external heating, or by the temperature of the introduced catalyst.

[0016] Optionally, the outlet temperature of the first-stage reaction unit is 450-650°C, preferably 500-600°C; the outlet temperature of the last-stage reaction unit is 550-750°C, preferably 600-700°C.

[0017] Optionally, the feedstock oil is selected from a combination of one or more of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or a combination of partial fractions or full fractions of one or more of coal liquefaction oil, oil sands oil, shale oil, synthetic oil and animal and plant oils and fats.

[0018] In a second aspect, the present invention relates to a system for producing light olefins by multi-stage catalytic cracking, the system comprising three or more reaction units connected in series, wherein the reaction units are reaction zones and / or reactors of a reactor; a catalyst delivery pipe and a crude oil feed nozzle are respectively provided at the bottom of the first-stage reaction unit; a settler is connected to the top of the last-stage reaction unit, an oil and gas delivery pipe is provided at the top of the settler, and the oil and gas delivery pipe is connected to an oil and gas separation system; any two directly connected reaction units are configured so that the outlet temperature of the latter reaction unit is 10-100°C higher than the outlet temperature of the previous reaction unit.

[0019] Optionally, the system further comprises a stripper, the solid inlet of the stripper is connected to the catalyst outlet of the settler, and the stripper is provided with a steam delivery pipe and a delivery pipe for the catalyst to be regenerated; the system further comprises a regenerator connected to the delivery pipe for the catalyst to be regenerated, and the temperature of the regenerator is configured to be 500-650°C, preferably 550-600°C.

[0020] Optionally, one or more reaction units located after the first-stage reaction unit are respectively provided with a catalyst introduction pipe.

[0021] Optionally, the catalyst delivery pipe of the first-stage reaction unit and the catalyst introduction pipe of any reaction unit after the first-stage reaction unit are respectively connected to the catalyst outlet of the regenerator.

[0022] Optionally, heating tiles are provided on the outside of the reaction unit at any stage.

[0023] Optionally, the reactor is composed of a single or composite reactor selected from a riser reactor, a fast bed reactor and a fluidized bed reactor.

[0024] Beneficial effects:

[0025] The multi-stage catalytic cracking reaction of the present invention is carried out sequentially in three or more reaction units connected in series. The outlet temperature of the latter reaction unit is 10-100°C higher than that of the former reaction unit. The reaction temperature is more closely matched with the cracking performance of hydrocarbon molecules, so that the intermediate products of the catalytic cracking are better converted, and the yield and selectivity of light olefins can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a specific embodiment of a system for producing light olefins through multi-stage catalytic cracking provided by the present invention;

[0027] Description of Reference Numerals

[0028] 1. First-stage reaction unit; 2. Intermediate-stage reaction unit; 3. Last-stage reaction unit;

[0029] 4. Settler; 5. Stripper; 11. Catalyst delivery pipe;

[0030] 12 crude oil feed nozzle; 13 first heating furnace tile; 21 intermediate heating furnace tile;

[0031] 31 last stage heating furnace tile; 41 oil and gas transmission pipe; 51 water vapor transmission pipe;

[0032] 52 is a delivery pipe for the catalyst to be generated. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below through the accompanying drawings and examples, through which the features and advantages of the present application will become more clear and distinct.

[0034] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0035] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0036] In the present invention, "front" and "rear" refer to the flow direction of the oil, that is, the direction where the oil flows first is "front" and the direction where the oil flows later is "rear".

[0037] In a first aspect, the present invention relates to a method for producing light olefins through multi-stage catalytic cracking, the method comprising: allowing raw oil and a first catalyst to enter a reactor system for a multi-stage catalytic cracking reaction to obtain an oil-agent mixture; separating the oil-agent mixture to obtain reaction oil gas and a catalyst to be generated; and separating the reaction oil gas to obtain light olefins; the reactor system comprises three or more upward reaction units connected in series, and in any two directly connected reaction units, the outlet temperature of the subsequent reaction unit is 10-100°C higher than the outlet temperature of the previous reaction unit; the reaction unit is a reaction zone and / or a reactor of the reactor.

[0038] It should be noted that the term "two directly connected reaction units" refers to the oil mixture or reaction oil gas flowing from one reaction unit directly into the other reaction unit without passing through other reaction units in between. The feedstock and first catalyst first enter the first-stage reaction unit for the first-stage catalytic cracking reaction, and then the last-stage reaction unit for the last-stage catalytic cracking reaction. The reaction unit between the first-stage and last-stage reaction units is the intermediate-stage reaction unit 2.

[0039] In the second aspect, the present invention relates to a system for producing light olefins through multi-stage catalytic cracking, which comprises three or more reaction units connected in series, wherein the reaction units are reaction zones and / or reactors of a reactor; a catalyst delivery pipe 11 and a crude oil feed nozzle 12 are respectively provided at the bottom of the first-stage reaction unit 1; a settler 4 is connected to the top of the last-stage reaction unit 3, an oil and gas delivery pipe 41 is provided at the top of the settler 4, and the oil and gas delivery pipe 41 is connected to an oil and gas separation system; any two directly connected reaction units are configured so that the outlet temperature of the latter reaction unit is 10-100°C higher than the outlet temperature of the former reaction unit.

[0040] It should be noted that the method described in the first aspect of the present invention is applicable to the system described in the second aspect of the present invention. The reaction units can be reaction zones connected in series within a reactor, or reactors connected in series, or can be n1 reaction zones of a reactor connected in series with n2 reactors, where the sum of n1 and n2 is greater than or equal to 3. A first catalyst enters the first-stage reaction unit 1 via a catalyst delivery pipe 11. The feedstock oil enters the first-stage reaction unit 1 via a feedstock oil feed nozzle 12 under a water vapor atomizing medium. The feedstock oil and the first catalyst contact the first-stage reaction unit 1 to undergo a first-stage catalytic cracking reaction, yielding a first oil-agent mixture. The first oil-agent mixture moves upward and enters the second-stage reaction unit for a second-stage catalytic cracking reaction, yielding a second oil-agent mixture. The mixture then enters... until it enters the final-stage reaction unit 3 for a final-stage catalytic cracking reaction, yielding an oil-agent mixture. The oil-agent mixture then enters a settler 4 for cyclone separation to yield oil, gas, and spent catalyst. The oil and gas are then delivered via an oil-gas delivery pipe 41 to an oil-gas separation system for separation into dry gas, liquefied gas, gasoline, diesel, and oil slurry.

[0041] It should be noted that the smaller the hydrocarbon molecules are, the higher the reaction temperature required for further cracking is. In the catalytic cracking process, the catalyst is a heat carrier. Since the cracking reaction is an endothermic reaction, as the cracking depth of the hydrocarbon molecules increases, the temperature of the catalyst gradually decreases, which is not conducive to the further conversion of the cracking intermediates. The present invention divides the catalytic cracking system into 3 or more reaction units, and adopts hot catalyst or external heating measures to increase the reaction temperature as the cracking reaction deepens, which is conducive to the further conversion of the cracking intermediates. The outlet temperature of the latter reaction unit is 10-100 ° C higher than the outlet temperature of the previous reaction unit. The reaction temperature is more compatible with the cracking performance of the hydrocarbon molecules, which can significantly improve the yield and selectivity of light olefins.

[0042] According to a first embodiment of the first aspect of the present invention, the method further comprises: stripping and regenerating the spent catalyst to obtain a regenerated catalyst; wherein the temperature of the regenerated catalyst is 500-650°C, preferably 550-600°C.

[0043] According to a first embodiment of the second aspect of the present invention, the system further comprises a stripper 5, the solid inlet of the stripper 5 is connected to the catalyst outlet of the settler 4, and the stripper 5 is provided with a steam delivery pipe 51 and a catalyst delivery pipe to be regenerated 52; the system further comprises a regenerator connected to the catalyst delivery pipe to be regenerated 52, and the temperature of the regenerator is configured to be 500-650°C, preferably 550-600°C.

[0044] It should be noted that the method of the first embodiment of the first aspect of the present invention is applicable to the system of the first embodiment of the second aspect of the present invention. The catalyst to be regenerated obtained by separation in the settler 4 enters the stripper 5 for stripping, and water vapor enters the stripper 5 through the water vapor conveying pipe 51. The catalyst after stripping enters the regenerator through the catalyst to be regenerated conveying pipe 52 for regeneration to obtain a regenerated catalyst. The obtained regenerated catalyst can enter the first-stage reaction unit 1 through the catalyst conveying pipe 11 to begin to catalyze the cracking reaction. The temperature of the regenerator can be configured to be 500-650°C to obtain a regenerated catalyst of 500-650°C; in this way, the temperature of the catalyst regeneration process is controlled within a more reasonable range, and the activity of the obtained regenerated catalyst can be more matched with the feedstock oil to carry out catalytic cracking reaction in the system of the present invention, which can further improve the yield and selectivity of light olefins.

[0045] As a preferred embodiment, the regenerated catalyst at 550-600° C. obtained in the regenerator is used as the first catalyst to enter the reaction system to exert a catalytic effect, which can further improve the yield and selectivity of light olefins.

[0046] According to a first embodiment of the first aspect of the present invention, the method further comprises: independently introducing a second catalyst into one or more reaction units after the first-stage reaction unit.

[0047] According to a first embodiment of the second aspect of the present invention, one or more reaction units located after the first-stage reaction unit 1 are respectively provided with a catalyst introduction pipe.

[0048] It should be noted that the reaction units after the first-stage reaction unit include an intermediate-stage reaction unit and a final-stage reaction unit. By respectively providing a catalyst introduction tube in one or more of the reaction units located after the first-stage reaction unit 1, the second catalyst can be independently introduced into any intermediate-stage reaction unit or the final-stage reaction unit. In this way, a new catalyst can be independently introduced into each stage of the reaction to better control the catalytic activity and the temperature of the reaction unit.

[0049] According to a first embodiment of the first aspect of the present invention, the first catalyst and the second catalyst are each independently the regenerated catalyst and / or the cooled regenerated catalyst.

[0050] According to a first embodiment of the second aspect of the present invention, the catalyst delivery pipe 11 of the first-stage reaction unit 1 and the catalyst introduction pipe of any reaction unit after the first-stage reaction unit 1 are respectively connected to the catalyst outlet of the regenerator.

[0051] It should be noted that the method of the first embodiment of the first aspect of the present invention is applicable to the system of the first embodiment of the second aspect. The regenerated catalyst obtained in the regenerator can be transported to the first-stage reaction unit 1 via the catalyst delivery pipe 11, and then introduced into an intermediate-stage reaction unit or the final-stage reaction unit via the corresponding catalyst introduction pipe, thereby forming a self-circulating system.

[0052] According to a first embodiment of the first aspect of the present invention, the outlet temperature of the latter reaction unit is 10-100° C. higher than the outlet temperature of the former reaction unit and is controlled by external heating or by the temperature of the introduced catalyst.

[0053] According to a first embodiment of the second aspect of the present invention, heating furnace tiles are respectively provided on the outside of the reaction units at any stage.

[0054] It should be noted that the first-stage reaction unit 1 and the last-stage reaction unit 3 may be provided with first heating furnace tiles 13 and last-stage heating furnace tiles 31 on the outside respectively; and the intermediate-stage reaction unit 2 at any level may be provided with intermediate-stage heating furnace tiles 21 on the outside.

[0055] It should be noted that, as a preferred embodiment, the outlet temperature of the latter reaction unit is 10-100°C higher than the outlet temperature of the former reaction unit and is controlled by external heating, such as by heating the furnace tiles to perform external heating to control the temperature difference between the outlets of the two reaction units. In this way, the temperature of the catalyst during regeneration can be controlled at 500-650°C, avoiding the deactivation and breakage of the catalyst by regenerating the catalyst at too high a temperature. The catalyst obtained in this way has high catalytic activity stability, that is, the regenerated catalyst at 500-650°C is used as the first catalyst to enter the first-stage reaction unit, and then flows upward in sequence to perform multi-stage catalytic cracking reactions, so that the catalytic cracking reactions in the system are better carried out to further improve the yield and selectivity of light olefins. The finally obtained catalyst to be regenerated is returned to the first-stage reaction unit for recycling after stripping and regeneration, forming a self-circulating system.

[0056] According to the first embodiment of the first aspect of the present invention, the outlet temperature of the first-stage reaction unit is 450-650°C, preferably 500-600°C; the outlet temperature of the last-stage reaction unit is 550-750°C, preferably 600-700°C.

[0057] According to a first embodiment of the first aspect of the present invention, the feedstock oil is selected from a combination of one or more of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or is selected from a combination of partial fractions or full fractions of one or more of coal liquefaction oil, oil sands oil, shale oil, synthetic oil and animal and plant fats and oils.

[0058] It should be noted that crude oil, atmospheric gas oil, vacuum gas oil, etc. are petroleum hydrocarbons, while coal liquefaction oil, oil sands oil, shale oil, etc. are mineral oils. The multi-stage catalytic cracking method of the present invention for producing light olefins has wide applicability, can effectively catalytically crack a variety of feedstock oils to obtain high light olefin yields and selectivities, and does not require pre-separation of the feedstock oils. The method is simple and energy-efficient.

[0059] According to a first embodiment of the second aspect of the present invention, the reactor is selected from a single or composite reactor of a riser reactor, a fast bed reactor, and a fluidized bed reactor. The system of the present invention has a simple and fast assembly process and is promising for large-scale production.

[0060] The present invention is further described in detail below by way of examples, but the present invention is not limited thereto.

[0061] The catalytic cracking catalyst used in the Examples and Comparative Examples was produced by the Qilu Branch of Sinopec Catalyst Co., Ltd., under the trade designation EP-3B. This catalyst contains a ZSP molecular sieve with an average pore size of less than 0.7 nanometers and an ultrastable Y-type molecular sieve. Prior to use, the catalyst was hydrothermally aged at 800°C with saturated steam for 17 hours. The main physicochemical properties of the catalyst are shown in Table 1. The properties of the feedstock oils used in the Examples and Comparative Examples are listed in Table 2.

[0062] In the following examples and comparative examples, the calculation method and the like are described as follows:

[0063] The product distribution values ​​of dry gas, liquefied gas and gasoline in the table represent mass fractions; among them, the dry gas yield is the sum of the mass fractions of H2, CH4 and C2 hydrocarbons in the product; the liquefied gas yield is the sum of the mass fractions of C3 and C4 hydrocarbons in the product; the gasoline yield is the yield of liquids with a boiling point less than 221°C in the product; the diesel yield is the yield of liquids with a boiling point of 221°C to 331°C in the product; and the slurry oil yield is the yield of liquids with a boiling point greater than 331°C in the product.

[0064] Conversion rate (%) = 100% - diesel yield - slurry yield;

[0065] Triene yield (%) = ethylene yield + propylene yield + butene yield;

[0066] Triene selectivity = triene yield ÷ conversion rate.

[0067] Table 1

[0068]

[0069] Table 2

[0070]

[0071]

[0072] Example 1

[0073] The experiment was carried out using a modified medium-sized unit with continuous reaction-regeneration operation, such as Figure 1 As shown. The reactor in this medium-sized unit is a riser reactor with an inner diameter of 36 mm and a length of 5300 mm. A 600°C regenerated catalyst is introduced into the bottom of the reactor via catalyst delivery pipe 11. Preheated crude oil is atomized with steam and then enters the reactor through crude oil feed nozzle 12, where it comes into contact with the regenerated catalyst and sequentially passes through the first, second, and third reaction zones for catalytic cracking. The reacted catalyst is stripped and then introduced into a regenerator for char regeneration. The reaction oil and gas are then introduced into a product separation system for separation into gaseous and liquid products. The regenerated catalyst is returned to the reactor via catalyst delivery pipe 11 for recycling. The medium-sized unit uses electric heating to maintain the temperature of the reaction-regeneration system. The reactor is divided into three reaction zones: the first, second, and third reaction zones are 1500 mm, 2000 mm, and 1800 mm in length, respectively. The temperatures of the three reaction zones are controlled by external heating furnace tiles.

[0074] The main operating conditions and results are listed in Table 3.

[0075] Example 2

[0076] The catalytic cracking reaction was carried out according to the method of Example 1, except that the temperature of the regenerated catalyst introduced into the bottom of the reactor through the catalyst delivery pipe 11 was different. The temperature of the regenerated catalyst in this example was 670° C., and the catalyst-to-oil mass ratio of the reactor was 8.

[0077] The main operating conditions and results are listed in Table 3.

[0078] Example 3

[0079] The catalytic cracking reaction was carried out according to the method of Example 1, except that the outlet temperatures of the three reaction zones were different.

[0080] The main operating conditions and results are listed in Table 3.

[0081] Comparative Example 1

[0082] The catalytic cracking reaction was carried out according to the method of Example 1, except that the outlet temperature of the next-stage reaction zone was lower than the outlet temperature of the previous-stage reaction zone.

[0083] The main operating conditions and results are listed in Table 3.

[0084] Table 3

[0085]

[0086] As shown in Table 3, Examples 1-3, using the multi-stage catalytic cracking method for producing light olefins provided by the present invention, achieve high triene yields and high triene selectivity. Furthermore, while the catalyst regeneration temperature in Example 1 was 600°C, that in Example 2 was 670°C. The yield and selectivity of light olefins in Example 1 were superior to those in Example 2.

[0087] In the description of this application, it should be noted that the terms "upper", "lower", "inside", "outside", "front", "back", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on this application.

[0088] In the description of this application, it should be noted that, unless otherwise specified or limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0089] The present application has been described above in conjunction with preferred embodiments, but these embodiments are merely exemplary and serve only as an illustrative example. On this basis, various replacements and improvements can be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A method for producing light olefins by multi-stage catalytic cracking, wherein: The method comprises: allowing raw oil and a first catalyst to enter a reactor system for multi-stage catalytic cracking reaction to obtain an oil-agent mixture; separating the oil-agent mixture to obtain reaction oil gas and a catalyst to be regenerated; and separating the reaction oil gas to obtain light olefins; The reactor system comprises three or more upward reaction units connected in series, wherein the outlet temperature of any two directly connected reaction units is 10-100° C. higher than the outlet temperature of the previous reaction unit; the reaction unit is a reaction zone and / or a reactor of the reactor, wherein the outlet temperature of the subsequent reaction unit is 10-100° C. higher than the outlet temperature of the previous reaction unit and is controlled by external heating. The spent catalyst is stripped and regenerated to obtain a regenerated catalyst, wherein the temperature of the regenerated catalyst is 500-650°C, and the regenerated catalyst at 500-650°C is used as the first catalyst to enter the first-stage reaction unit, and then flows upward in sequence to perform a multi-stage catalytic cracking reaction.

2. The method according to claim 1, wherein the temperature of the regenerated catalyst is 550-600°C.

3. The method according to claim 1, wherein The outlet temperature of the first-stage reaction unit is 450-650°C; The outlet temperature of the last stage reaction unit is 550-750°C.

4. The method according to claim 3, wherein: The outlet temperature of the first-stage reaction unit is 500-600°C.

5. The method according to claim 3, wherein The outlet temperature of the last stage reaction unit is 600-700℃.

6. The method according to claim 1, wherein The raw oil is selected from one or more of crude oil, atmospheric wax oil, vacuum wax oil, atmospheric residue oil, vacuum residue oil, deasphalted oil, hydrogenated heavy oil and coker wax oil; or is selected from one or more of partial fractions or full fractions of coal liquefaction oil, oil sand oil, shale oil, and animal and plant oils and fats.

7. The method according to claim 1, wherein The raw oil is selected from a partial fraction or a full fraction of synthetic oil.

8. The method according to claim 1, wherein The outside of the reaction unit at any stage is respectively provided with heating furnace tiles.

9. The method according to claim 1, wherein The reactor is a single or composite reactor selected from a riser reactor, a fast bed reactor and a fluidized bed reactor.

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